WO2005012881A2 - An apparatus and method for providing a density measurement augmented for entrained gas - Google Patents

An apparatus and method for providing a density measurement augmented for entrained gas Download PDF

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Publication number
WO2005012881A2
WO2005012881A2 PCT/US2004/024803 US2004024803W WO2005012881A2 WO 2005012881 A2 WO2005012881 A2 WO 2005012881A2 US 2004024803 W US2004024803 W US 2004024803W WO 2005012881 A2 WO2005012881 A2 WO 2005012881A2
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WO
WIPO (PCT)
Prior art keywords
ofthe
fluid
density
flow
gas
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PCT/US2004/024803
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French (fr)
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WO2005012881A3 (en
Inventor
Daniel L. Gysling
Patrick Curry
Douglas H. Loose
Thomas E. Banach
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Cidra Corporation
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Priority claimed from US10/892,886 external-priority patent/US7152460B2/en
Application filed by Cidra Corporation filed Critical Cidra Corporation
Priority to CA2537933A priority Critical patent/CA2537933C/en
Publication of WO2005012881A2 publication Critical patent/WO2005012881A2/en
Publication of WO2005012881A3 publication Critical patent/WO2005012881A3/en

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N9/00—Investigating density or specific gravity of materials; Analysing materials by determining density or specific gravity
    • G01N9/002—Investigating density or specific gravity of materials; Analysing materials by determining density or specific gravity using variation of the resonant frequency of an element vibrating in contact with the material submitted to analysis
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
    • G01F1/00—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow
    • G01F1/74—Devices for measuring flow of a fluid or flow of a fluent solid material in suspension in another fluid
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
    • G01F1/00—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow
    • G01F1/76—Devices for measuring mass flow of a fluid or a fluent solid material
    • G01F1/78—Direct mass flowmeters
    • G01F1/80—Direct mass flowmeters operating by measuring pressure, force, momentum, or frequency of a fluid flow to which a rotational movement has been imparted
    • G01F1/84—Coriolis or gyroscopic mass flowmeters
    • G01F1/8409—Coriolis or gyroscopic mass flowmeters constructional details
    • G01F1/8413—Coriolis or gyroscopic mass flowmeters constructional details means for influencing the flowmeter's motional or vibrational behaviour, e.g., conduit support or fixing means, or conduit attachments
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
    • G01F1/00—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow
    • G01F1/76—Devices for measuring mass flow of a fluid or a fluent solid material
    • G01F1/78—Direct mass flowmeters
    • G01F1/80—Direct mass flowmeters operating by measuring pressure, force, momentum, or frequency of a fluid flow to which a rotational movement has been imparted
    • G01F1/84—Coriolis or gyroscopic mass flowmeters
    • G01F1/845—Coriolis or gyroscopic mass flowmeters arrangements of measuring means, e.g., of measuring conduits
    • G01F1/8468—Coriolis or gyroscopic mass flowmeters arrangements of measuring means, e.g., of measuring conduits vibrating measuring conduits
    • G01F1/8472—Coriolis or gyroscopic mass flowmeters arrangements of measuring means, e.g., of measuring conduits vibrating measuring conduits having curved measuring conduits, i.e. whereby the measuring conduits' curved center line lies within a plane
    • G01F1/8477—Coriolis or gyroscopic mass flowmeters arrangements of measuring means, e.g., of measuring conduits vibrating measuring conduits having curved measuring conduits, i.e. whereby the measuring conduits' curved center line lies within a plane with multiple measuring conduits
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
    • G01F1/00—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow
    • G01F1/76—Devices for measuring mass flow of a fluid or a fluent solid material
    • G01F1/78—Direct mass flowmeters
    • G01F1/80—Direct mass flowmeters operating by measuring pressure, force, momentum, or frequency of a fluid flow to which a rotational movement has been imparted
    • G01F1/84—Coriolis or gyroscopic mass flowmeters
    • G01F1/845—Coriolis or gyroscopic mass flowmeters arrangements of measuring means, e.g., of measuring conduits
    • G01F1/8468—Coriolis or gyroscopic mass flowmeters arrangements of measuring means, e.g., of measuring conduits vibrating measuring conduits
    • G01F1/849—Coriolis or gyroscopic mass flowmeters arrangements of measuring means, e.g., of measuring conduits vibrating measuring conduits having straight measuring conduits
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
    • G01F15/00—Details of, or accessories for, apparatus of groups G01F1/00 - G01F13/00 insofar as such details or appliances are not adapted to particular types of such apparatus
    • G01F15/02—Compensating or correcting for variations in pressure, density or temperature
    • G01F15/022—Compensating or correcting for variations in pressure, density or temperature using electrical means
    • G01F15/024—Compensating or correcting for variations in pressure, density or temperature using electrical means involving digital counting
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
    • G01F25/00—Testing or calibration of apparatus for measuring volume, volume flow or liquid level or for metering by volume
    • G01F25/10—Testing or calibration of apparatus for measuring volume, volume flow or liquid level or for metering by volume of flowmeters
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
    • G01N29/02—Analysing fluids
    • G01N29/024—Analysing fluids by measuring propagation velocity or propagation time of acoustic waves
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2291/00—Indexing codes associated with group G01N29/00
    • G01N2291/01—Indexing codes associated with the measuring variable
    • G01N2291/011—Velocity or travel time
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2291/00—Indexing codes associated with group G01N29/00
    • G01N2291/02—Indexing codes associated with the analysed material
    • G01N2291/021—Gases
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2291/00—Indexing codes associated with group G01N29/00
    • G01N2291/02—Indexing codes associated with the analysed material
    • G01N2291/025—Change of phase or condition
    • G01N2291/0258—Structural degradation, e.g. fatigue of composites, ageing of oils
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2291/00—Indexing codes associated with group G01N29/00
    • G01N2291/02—Indexing codes associated with the analysed material
    • G01N2291/028—Material parameters
    • G01N2291/02818—Density, viscosity
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2291/00—Indexing codes associated with group G01N29/00
    • G01N2291/02—Indexing codes associated with the analysed material
    • G01N2291/028—Material parameters
    • G01N2291/02836—Flow rate, liquid level
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2291/00—Indexing codes associated with group G01N29/00
    • G01N2291/02—Indexing codes associated with the analysed material
    • G01N2291/028—Material parameters
    • G01N2291/02872—Pressure
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2291/00—Indexing codes associated with group G01N29/00
    • G01N2291/04—Wave modes and trajectories
    • G01N2291/042—Wave modes
    • G01N2291/0422—Shear waves, transverse waves, horizontally polarised waves

Definitions

  • This invention relates to an apparatus for measuring the density of a fluid flow having entrained gas therein, and more particularly to an apparatus that measures the speed of sound propagating through the flow to determine the gas volume fraction ofthe flow in the process to augment or correct the density measurement of a density meter and/or to provide a composition measurement compensated for entrained gas.
  • Density meters are commonly used instruments in industrial processes. Common types of density meters include nuclear densitometers, vibrating vane densitometers and Coriolis flow meters having a density measurement as a by-product measurement. In most applications, density measurements are used to discern bulk properties of the process fluid. Typically, density measurements are intended to provide information about the liquid and solid phases of a process fluid. These measurements get confound when an rmknown amount of entrained air is present. For a two-component mixture, knowing the component densities and accurately measuring the mixture density provides a means to determine the phase fractions of each of * the two components.
  • multiphase process flow rate is a critical process control parameter for the paper and pulp industry. Knowing the amounts of liquid, solids and entrained gases flowing in process lines is key to optimizing the overall the papermaking process.
  • significant challenges remain in the achieving accurate, reliable, and economical monitoring of multiphase flow rates of paper and pulp slurries. Reliability challenges arise due the corrosive and erosive properties ofthe slurry. Accuracy challenges stem from the multiphase nature ofthe slurries. Economical challenges arise from the need to reduce total lifetime cost of flow measurement, considering installation and maintenance costs in addition to the initial cost ofthe equipment.
  • This disclosure provide an means and apparatus for well head monitoring that combines multiple existing technologies in to system that should meet a wide range of cost and performance goals. It is proposed herein to use sonar-based entrained gas measurement to determine the entrained gas level in conjunction with any mixture density measurement to improve the accuracy and therefore value ofthe density measurement.
  • a sound speed based entrained gas measurement can accurately determine the entrained gas in an aerated mixture without precise knowledge of the composition of either the non -gas components of the multiphase mixture ofthe composition of gas itself.
  • the entrained gas levels can be determined - 3 - CC-0765 PCT EV 386515255 US essentially independent ofthe determination ofthe liquid properties.
  • the accuracy could be improved using the sound speed measurement and mixture density simultaneously, but is not required. Determining the entrained gas level enables the density measurement to determine the properties of non-gas component ofthe multiphase mixture with the same precision as if the gas was not present. This capability also enables the density meters to provide significantly enhanced compositional information for aerated mixtures.
  • Objects ofthe present invention include an apparatus having a device for determining the speed of sound propagating within a fluid flow in a pipe to determine the gas volume fraction of a process fluid or flow flowing within a pipe, and augment to improve the accuracy of a density measurement of a density meter and/or to provide a composition measurement compensated for entrained gas.
  • a flow measuring system for determining the density of a fluid flowing in a pipe is provided.
  • the measuring system comprises a density meter that provides a density signal indicative ofthe density ofthe fluid flowing in the pipe.
  • a flow measuring device measures the speed of sound propagating through the fluid.
  • the measuring device provides an SOS signal indicative ofthe speed of sound propagating through the fluid and/or a GVF signal indicative ofthe gas volume fraction ofthe fluid.
  • a processing unit determines the density ofthe non-gaseous component ofthe aerated fluid in response to the SOS signal and/or the GVF signal and the density signal.
  • a well head metering system for measuring density of non-gaseous components of a three phase fluid flowing in a pipe is provided.
  • the metering system comprises a density meter that provides a density signal indicative of the density ofthe fluid flowing in the pipe.
  • a flow measuring device measures the speed of sound propagating through the fluid.
  • the measuring device provides an SOS signal indicative ofthe speed of sound propagating through the fluid and/or a GVF signal indicative ofthe gas volume fraction ofthe fluid.
  • a processing unit determines the density ofthe non-gaseous component ofthe aerated fluid in response to the SOS signal and/or the GVF signal and the density signal.
  • Fig. 1 is a schematic illustration of a flow measuring system for providing a density and/or composition measurement augmented for entrained gas within an aerated fluid flow passing within a pipe, in accordance with the present invention.
  • Fig. 2 is a schematic illustration of another flow measuring system for providing a density and/or composition measurement augmented for entrained gas within an aerated fluid flow passing within a pipe, in accordance with the present invention.
  • Fig. 3 is a function block diagram of a processing unit of flow measuring system similar to that of Fig. 1, in accordance with the present invention.
  • Fig. 1 is a schematic illustration of a flow measuring system for providing a density and/or composition measurement augmented for entrained gas within an aerated fluid flow passing within a pipe, in accordance with the present invention.
  • Fig. 3 is a function block diagram of a processing unit of flow measuring system similar to that of Fig. 1, in accordance with the present invention.
  • Fig. 1 is a schematic illustration of a flow
  • FIG. 4 is a schematic illustration of a flow measuring system for providing a density and/or composition measurement provided by a gamma densitometer augmented for entrained gas within a bitumen froth flow passing within a pipe, in accordance with the present invention.
  • Fig. 5 is a plot ofthe relative error in the interpreted percent solids versus the gas volume fraction in a bitumen froth flow, in accordance with the present invention.
  • Fig. 6 is a schematic illustration of a flow measuring system for providing a density and/or composition measurement provided by a coriolis meter augmented for entrained gas within a bitumen froth flow passing within a pipe, in accordance with the present invention.
  • Fig. 5 is a plot ofthe relative error in the interpreted percent solids versus the gas volume fraction in a bitumen froth flow, in accordance with the present invention.
  • Fig. 6 is a schematic illustration of a flow measuring system for providing a density and/or composition measurement provided
  • FIG. 7 is a function block diagram of a processing unit of flow measuring system similar to that of Fig. 6, in accordance with the present invention.
  • Fig. 8 is a schematic illustration of model of a coriolis meter having aerated fluid flowing therethrough that accounts for compressibility and inhomogeniety ofthe aerated fluid, in accordance with the present invention.
  • Fig. 9 is a schematic illustration of a well head monitoring system for providing a density and/or composition measurement provided by a coriolis meter augmented for entrained gas within a bitumen froth flow passing within a pipe, in accordance with the present invention.
  • Fig. 10 is a plot of three phase composition of an aerated hydrocarbon and water fluid flow as a function of sound speed and flow density, in accordance with the present invention.
  • Fig. 11 is another embodiment of a function block diagram of a processing unit of flow measuring system similar to that of Fig. 7, in accordance with the present invention.
  • Fig. 12 is a plot the density correction and gas volume fraction of a fluid determined by a flow system embodying the present invention
  • Fig. 13 is a plot of net oil error and watercut of three phase fluid flow determined by a flow system embodying the present invention.
  • Fig. 14 is a plot of a snap shot of three phase fluid flow determined by a flow system embodying the present invention.
  • Fig. 11 is another embodiment of a function block diagram of a processing unit of flow measuring system similar to that of Fig. 7, in accordance with the present invention.
  • Fig. 12 is a plot the density correction and gas volume fraction of a fluid determined by a flow system embodying the present invention
  • FIG. 15 is a schematic block diagram of a gas volume fraction meter, in accordance with the present invention.
  • Fig. 16 is a schematic block diagram of another embodiment of gas volume fraction meter, in accordance with the present invention.
  • Fig. 17 is a k ⁇ plot of data processed from an array of pressure sensors use to measure the speed of sound of a fluid flow passing in a pipe, in accordance with the present invention.
  • Fig. 18 is a plot ofthe speed of sound ofthe fluid flow as a function ofthe gas volume fraction over a range of different pressures, in accordance with the present invention.
  • Fig. 19 is a schematic block diagram of a volumetric flow meter having an array of sensor, in accordance with the present invention.
  • Fig. 20 is a graphical cross-sectional view ofthe fluid flow propagating through a pipe, in accordance with the present invention.
  • Fig. 21 is a k ⁇ plot of data processed from an array of pressure sensors use to measure the velocity of a fluid flow passing in a pipe, in accordance with the present invention.
  • Density meters 16 provide a measurement ofthe density of a fluid flow 12 passing through a pipe 14.
  • a density meter provides erroneous density measurements in the presence of entrained gas (e.g., bubbly gas) within the fluid flow.
  • the present invention provides a means for augmenting or compensating the density meter to determine improved density measurements that provides the density ofthe non-gas portion ofthe fluid flow 12.
  • the density meter may be any device capable of measuring the density ofthe fluid flow, such as nuclear densitometers, vibrating vane densitometers and Coriolis flow meters, which provide a density measurement as a by-product measurement.
  • the present invention proposes the use of sonar-based entrained gas measurements to determine the entrained gas level in conjunction with any density measurement of a mixture flowing in a pipe to improve the accuracy, and therefore value ofthe density measurement.
  • a sound speed based entrained gas measurement can accurately determine the entrained gas in an aerated mixture without precise knowledge ofthe composition of either the non -gas components ofthe multiphase mixture or the composition of gas itself.
  • the entrained gas levels can be determined essentially independent ofthe determination ofthe liquid properties. The accuracy could be improved using the sound speed measurement and mixture density simultaneously, but is not required. Determining the entrained gas level enables the density measurement to determine the properties of non- gas component ofthe multiphase mixture with the same precision as if the gas was not present.
  • a flow measuring system 10 embodying the present invention includes a density meter 16, a speed of sound (SOS) measuring apparatus 18 and a processing unit 20 to provide any one or more ofthe following parameters ofthe fluid flow 12, namely, gas volume fraction, speed of sound propagating through the fluid flow, uncompensated density, compensated density and composition.
  • the fluid flow may be any aerated fluid or mixture including liquid, slurries, solid/liquid mixture, liquid/liquid mixture, solid/solid mixture and any other multiphase flow having entrained gas.
  • the density meter 16 provides a signal 22 indicative ofthe density ofthe fluid flow 12 not augmented or compensated for entrained gas.
  • the SOS measuring apparatus 18 provides an SOS signal 24 indicative ofthe speed of sound propagating through the fluid flow.
  • a processing unit 20 determines at least one ofthe parameters ofthe fluid flow described hereinbefore in response to the SOS signal 24 and density signal 22.
  • Pressure and/or temperature signals 26,28 may also be provided to the processing unit 20, which may be used to provide more accurate measurements ofthe gas volume fraction. The pressure and temperature may be measured by known means or estimated.
  • the SOS measuring device 18 includes any means for measuring the speed of sound propagating through the aerated flow 12.
  • One method includes a pair of ultra-sonic sensors axially spaced along the pipe 14, wherein the time of flight of an ultrasonic signal propagating between an ultra-sonic transmitter and receiver is indicative ofthe speed of sound. Depending on the characteristics ofthe flow, the frequency ofthe ultra-sonic signal must be relating low to reduce scatter within the flow.
  • the meter is similar as that described in U.S. Patent Application No. 10/756,922 (CiDRA Docket No. CC-0699) filed on January 13, 2004, which is incorporated herein by reference.
  • a flow measuring system 30 embodying the present invention as shown in Figs.
  • the GVF meter 100 comprises a sensing device 116 having a plurality of strain-based or pressure sensors 118-121 spaced axially along the pipe for measuring the acoustic pressures 190 propagating through the flow 12.
  • the GVF meter determines and provides a first signal 27 indicative ofthe SOS propagating through the fluid flow 12 and a second signal 29 indicative ofthe gas volume fraction (GVF) ofthe flow 12, which will be described in greater detail hereinafter.
  • the gas volume fraction meter 100 is similar to that described in U.S. Patent Application No. 10/762,410 (Cidra Docket No. CC-0703) filed on January 21, 2004, which is incorporated herein by reference.
  • the processing unit 32 determines at least one ofthe parameters ofthe fluid flow described hereinbefore in response to the SOS signal 24 and/or GVF signal 29, and the density signal 22.
  • CC-0765 PCT EV 386515255 US Fig. 3 illustrates a functional block diagram 40 ofthe flow measuring system 30 of Fig. 2.
  • the GVF meter 100 measures acoustic pressures propagating through the fluids 12, thereby measuring the speed of sound ⁇ propagating through the fluid flow 12 at 42.
  • the GVF meter 100 calculates the gas volume fraction ofthe fluid using the measured speed of sound at 44.
  • the GVF meter may also use the pressure ofthe process flow to determine the gas volume fraction.
  • the pressure may be measured or estimated at 46.
  • an improved density 48 i.e., density of non-gas portion of flow 12
  • the calculated gas volume fraction 29 is provided to the processing unit 32.
  • the processing unit 32 can determine density ofthe non-gas portion of the multiphase flow 12. Specifically, the density ( ⁇ m ⁇ x ) 22 of an aerated flow 12 is related to the volumetric phase fraction ofthe components ( ⁇ j) and the density ofthe components ( ⁇ i).
  • knowing the density (p gas ) ofthe gas/air, the measured gas volume fraction ofthe gas ( ⁇ gas ), and the improved density measurement (p m i x ) ofthe aerated flow to be compensated for entrained gas enable the density (p n0n g as ) ofthe non-gas portion ofthe aerated flow 12 to be determined, which provides improved compositional information of the aerated flow 12.
  • knowing just the measured density (p m i x ) 22 ofthe aerated flow 12 density ofthe gas component and the gas volume fraction ( ⁇ gas ) 29 is sufficient to determine the density (p n0 ngas) 48 ofthe non-gas component ofthe flow 12.
  • the present invention further contemplates determining improved compositional information ofthe aerated flow 12.
  • bitumen froth mixture 12 which contains a small amount of entrained air and sand particles entrained in a liquid continuous mixture of bitumen and water.
  • the density of bitumen and water (pi) are nearly identical for most applications, therefore, variations in the bitumen / water cut of liquid phase has very limited effect on the mixture density. Variations in the mixture density are therefore due to the air and particles.
  • the density ofthe particles (p 2 ) and the density ofthe air (p gas ) are known.
  • Fig. 5 is a plot ofthe relative error in interpreted percent of solids in a bitumen froth flow versus the gas fraction of entrained air/gas in the flow 12.
  • a bitumen froth flow having 1 % of entrained air therein results in an approximately 20% error in percent solids (e.g., sand) in the bitumen froth flow.
  • the density measurement (p n0 n g as) and composition measurement ( ⁇ , ⁇ 2 ) described above can be done on the full pipe, or as shown in Fig. 6, on a slip stream pipe 70.
  • a slip stream pipe 70 enables the use of a coriolis meter 72 to measure the density (p m ix) by providing a smaller diameter pipe.
  • a further benefit of a sonar-based entrained air measurement is achieved when the sound speed measurement is used to enhance the accuracy ofthe coriolis on the aerated mixture, similar to that described in U.S. Patent Application No. 10/892,886 (Cidra Docket No. CC-0762), filed on July 15, 2004, which is incorporated herein by reference. While the entrained gas meter 100 is shown mounted on the full pipe in Fig. 6, the present invention contemplates that the entrained air meter may be mounted on the slip stream pipe 70.
  • the apparatus 100 for measuring the gas volume fraction ofthe flow 12 may also provide a velocity measurement and a volumetric flow rate measurement ofthe flow, similar to that described in U.S. Patent Application No. 10/712,818 (Cidra Docket No. CC-0675), filed on November 12, 2003, U.S. Patent Application No. 10/712,833 (Cidra Docket No. CC-0676), filed on November 12, 2003, U.S. Patent Application No. 10/766,440 (Cidra Docket No. CC-0714), filed on January 27, 2004, and U.S. Patent Application No.
  • Coriolis meters provide a measurement ofthe mass flow and/or density of a fluid flow 12 passing through a pipe 14.
  • a coriolis meter provides erroneous mass flow and density measurements in the presence of entrained gas within the fluid flow (e.g., bubbly gas).
  • the present invention may also provide a means for compensating the coriolis meter to provide corrected or improved density and/or mass flow measurements.
  • the gas volume fraction meter 100 may be used to determine the density of the non-gas component ofthe flow 12 and the composition of a multi-phase flow 12 as described hereinbefore
  • the GVF meter may be also used to compensate or augment the output density measurement and the mass flow measurement of a coriolis meter, similar to that described in U.S. Patent Application No. 10/892,886 (CiDRA Docket No. CC-0762) filed July 15, 2004, which is incorporated herein by reference.
  • the coriolis meter 16 provides a frequency signal (f nat ) indicative ofthe natural frequency ofthe fluid 12 loaded tubes ofthe coriolis meter and the phase signal ( ⁇ ) indicative ofthe phase lag in the tubes ofthe coriolis meter.
  • the GVF meter 100 or SOS measuring apparatus 18 provides an SOS signal 24 indicative ofthe speed of sound propagating through the fluid flow.
  • a processing unit 32 processes the frequency signal, the phase signal and the SOS signal to provide at least one ofthe parameters ofthe fluid flow described hereinbefore, including the mass flow ofthe flow 12.
  • Pressure and/or temperature signals may also be provided to the processing unit 32, which may be used to provide more accurate measurements ofthe gas volume fraction.
  • the pressure and temperature may be measured by known means or estimated.
  • the coriolis meter may be any known coriolis meter, such as two inch bent tube coriolis meter manufactured my MicroMotion Inc.
  • Fig. 7 illustrates a functional block diagram 80 ofthe flow measuring system of Fig. 2.
  • the GVF meter 100 measures acoustic pressures propagating through the fluids to measure the speed of sound ⁇ .
  • the GVF meter calculates at least gas volume fraction ofthe fluid and/or the reduced natural frequency using the measured speed of sound.
  • the GVF meter may also use the pressure ofthe process flow to determine the gas volume fraction.
  • the calculated gas volume fraction and/or reduced frequency is provided to the processing unit 21.
  • the improved density is determined using analytically derived or empirically derived density calibration models (or formulas derived therefore), which is a function ofthe measured natural frequency and at least one ofthe determined GVF, reduced frequency and speed of sound, or any combination thereof, which will be described in greater detail hereinafter.
  • the improved density measurement is the density of the aerated flow passing through the pipe.
  • the present invention further contemplates determining improved compositional information ofthe aerated flow. In other words, knowing the speed of sound propagating through the flow and the improved density, the processing unit 21 can determine phase fraction of each component ofthe multiphase flow.
  • the present invention also contemplates compensating or improving the mass flow rate measurement ofthe coriolis meter 16, as shown in Fig. 7.
  • the calculated gas volume fraction and/or reduced frequency is provided to the processing unit 32.
  • the improved mass flow rate is determined using analytically derived or empirically derived mass flow calibration models (or formulas derived therefore), which is a function ofthe measured phase difference ( ⁇ ) and at least one ofthe determined GVF, reduced frequency and speed of sound, or any combination thereof, which will be described in greater detail hereinafter.
  • the calculated gas volume fraction and/or reduced frequency is provided to the processing unit 32.
  • the improved density is determined using analytically derived or empirically derived density calibration/parameter models (or
  • the improved mass flow measurement is the mass flow rate ofthe aerated flow passing through the pipe. While the improved mass flow and improved density measurement may be a function GVF, SOS and reduced frequency, the present invention contemplates these improved measurements may be a function of other parameters, such a gas damping _" gas .
  • the processing unit 32 may improve both the density measurement and the density measurement ofthe coriolis meter 16
  • the invention contemplates that the processing may only compensate or improve one the density and mass flow rate parameters.
  • Results for a lumped parameter model of Fig. 8 presented hereinafter confirm long recognized accuracy degradation of vibrating tube density meters attributed to aeration.
  • the models can be used to illustrate qualitatively the role of several non-dimensional parameters that govern the performance ofthe meters in aerated fluids. It can be concluded from these models that gas volume fraction plays a dominant role, with several other parameters including gas damping _ ⁇ gas and reduced frequency also influencing performance.
  • the present invention provides an approach in which a speed-of-sound measurement ofthe process fluid is integrated with the natural frequency measurement of a vibrating tube density meter to form a system with an enhanced ability to operate accurately in aerated fluids.
  • Introducing a real time, speed-of-sound measurement address the effects of aeration on multiple levels with the intent to enable vibrating-tube-based density measurement to continue to report liquid density in the presence of entrained air with accuracy approaching that for a non-aerated liquid.
  • the aeration level ofthe process fluid can be determined with high accuracy on a real time basis.
  • liquids phase includes pure liquids, mixtures of liquids, as well as liquid / solid mixtures.
  • a simplified, lumped parameter model for the effects of aeration in vibrating tubes is developed. The model illustrates that the effects of aeration can be attributed to at least two independent mechanisms; 1) the density inhomogeniety of discrete gas bubbles and 2) increased mixture compressibility due to aeration.
  • This basic framework provides an accurate means to determine process fluid density under most operating conditions.
  • some ofthe fundamental assumptions regarding the interaction ofthe fluid 12 and the structure can deteriorate under different operating conditions. Specifically, aerated fluids in oscillating tubes behave differently from single phase fluids in two important ways; increased compressibility, and fluid inhomogeneity.
  • this frequency corresponds to a wavelength of an acoustic oscillation of approximately two diameters, i.e., this transverse mode is closely related to a "half wavelength" acoustic resonance ofthe tube.
  • the frequency ofthe first transverse acoustic mode is quite high compared to the typical structural resonant frequencies of coriolis meters of 100 Hz, however, the resonant acoustic frequency decreases rapidly with increased levels of entrained air.
  • a reduced frequency can be defined as a ratio ofthe natural frequency ofthe structural system to that ofthe fluid dynamic system.
  • J struct red mix Where f s tr uct is the natural frequency ofthe tabes in vacuum, D is the diameter ofthe tubes, and a m i ⁇ is the sound speed ofthe process fluid.
  • f s tr uct the natural frequency ofthe tabes in vacuum
  • D the diameter ofthe tubes
  • a m i ⁇ is the sound speed ofthe process fluid.
  • the density ofthe sphere is orders of magnitude below that ofthe liquid and the velocity of bubble approaches three times that ofthe fluid.
  • the increased motion ofthe sphere compared to the remaining fluid must result in a portion ofthe remaining fluid having a reduced level of participation in oscillation, resulting in a reduced, apparent system inertia.
  • a gas bubble of volume fraction ⁇ is connected across a fulcrum 42 to a compensating mass of fluid with volume 2T, where T is the gas volume fraction ofthe flow.
  • the fulcrum is rigidly connected to the outer pipe 14.
  • Fig. 8 shows a schematic of a lumped parameter model that incorporates the effects of compressibility and inhomogeniety using the mechanism-specific models developed above.
  • the equations of motion ofthe above lumped parameter model assuming solutions in the form of e s ⁇ where s is the complex frequency, can be expressed in non-dimensional form as:
  • Parameter Descrivtion Value fs Structural Frequency of Tubes 100 Hz ⁇ Mass ratio 1.25 Sstruot Critical Damping Ratio - 0.01 structure ⁇ fluid Critical Damping Ratio - fluid 0.01 gas Critical Damping Ratio - gas 0.01 Q Frequency Ratio As determined by sound speed of air / water at STP and structural parameters D Tube diameter 1.0 inches Table 2: Parameters Defining the Baseline Vibrating Tube Density Meter
  • the level of aeration has a dominant effect on the difference between actual and apparent mixture density.
  • the damping parameter associated with the movement ofthe gas bubble relative to the fluid within the tube, ⁇ gas is a parameter governing the response ofthe system to aeration. For ⁇ g as approaching zero, the apparent density approaches 1-3T, i.e., the meter under reports - 19 -
  • the two reduced frequencies are not independent, and are scalar multiples of each other.
  • variations in the reduced frequencies above are primarily determined by variations in process fluid sound speed. Physically, the reduced frequency represents the ratio between the time required for sound to propagate over a characteristic length to the time required for the tube to vibrate - 20 -
  • reduced frequencies serve to capture the importance of unsteadiness in the aeroelastic interaction ofthe fluid and structure.
  • the process can be modelled as quasi-steady.
  • Most analytical models of Corilois flow meters use a quasi-steady model for the fluid /structure interaction.
  • unsteady effects begin to influence the relationship between the measured structural response, i.e. the phase lag in the two legs ofthe meters and the natural frequency, and the sought fluid parameters, i.e. the mass flow ofthe fluid and fluid density.
  • a sound-speed based gas volume fraction parameter a reduced frequency parameter relating to phase lag to mass flow rate. If the reduced frequency based on diameter is non-negligible, the inertial load from the fluid on the pipe develops a slight phase lags that increases with increasing frequency.
  • the reduced frequency parameter and gas volume fraction can be used as inputs in the interpretation of phase lag in terms of mass flow. Due to the strong relationship between air content in liquids and mixture sound speed, the role ofthe reduced frequency parameter in the interpretation ofthe fundamental measurement ofthe Coriolis meter will have a more pronounce effect in bubbly flows. However, changes in sound speed and hence reduced frequency of operation in various types of liquids and other process mixtures have an effect on the interpretation and hence accuracy of Coriolis meter used in these applications as well.
  • the performance of a Coriolis meter on two liquids - water and oil Assume that the fluids - 22 - CC-0765 PCT EV 386515255 US have different densities and sound speeds.
  • the reduced frequency for the water will typically be ⁇ 10%-30% lower than that for the oil application. Recognizing that, while they are different, the reduced frequencies for both applications are still "small", the impact on accuracy may not be significant. However, some degree of inaccuracy is introduced by not accounting for the differences in the reduced frequency of operation ofthe Coriolis meter in this application.
  • water is pumped from the bottom of a large separator through a mag meter which measures the volumetric flow rate ofthe water. The water then flows through a SONARtrac entrained air meter to verify that the water has negligible entrained air. Air is then injected into the water forming a two phase mixture.
  • the amount of entrained air is then measured with a second SONARtrac meter.
  • the two phase mixture, of known water and air composition then passes through a 3 inch, bent tube Corilois meter.
  • the outputs of all ofthe above mentioned metering devices where recorded along with water pressure and temperature.
  • the errors associated with the coriolis meter operating in the aerated liquids can be determined and plotted as a function of sound speed based parameters.
  • Coriolis meter performance is characterized as a function of gas volume fraction. The errors were indeed significant.
  • the Coriolis meter is over reporting mass flow by 15% and under reporting mixture density by 2%.
  • the actual density being reported by the meter if inte ⁇ reted as the density ofthe liquid phase in the meter would be roughly 4%> in error.
  • the mass flow error is parameterized by the sound speed -based gas volume fraction of entrained air. The parametric dependence of this is given by the equation shown on the plot.
  • Mass Factor 0.0147gvf ⁇ 3 - 0.0018gvf ⁇ 2 + 0.004 lgvf + 1.0009
  • a flow measuring system 82 embodying the present invention may be used monitor well heads.
  • a basic configuration of a well metering system 84 is shown schematically in Fig. 9.
  • a two phase separator 86 e.g., gas/liquid cylindrical cyclone (GLCC) separator
  • GLCC gas/liquid cylindrical cyclone
  • the mostly gas stream 88 is fed to a sonar-based flow meter 89 similar as flow meter 90 which will be described in greater detail herein after.
  • the flow meter measures the flow rate ofthe gas and determines the gas volume fraction ofthe gas fluid.
  • the mostly liquid stream 89 is fed into a sonar-based flow meter 90, similar to the meters 18 and 100 of Figs. 1 and 2 respectively, which measures mixture sound speed and possibly convective velocity to determine the gas volume fraction and the volumetric flow rate, respectively, ofthe liquid gas mixture 89.
  • the flow meter 90 is similar to that described in U.S. Patent Application No. 10/XXX,XXX (CiDRA No. CC-0749) filed June 24, 2004, U.S. Patent Application No. 10/766,440 (CiDRA No. CC-0714) and U.S. Patent Application No. 10/762,410 (CiDRA No. CC-0703), which are incorporated herein by reference.
  • a processing unit 92 receives the output signals from the flow meter 90 and coriolis meter 16 to provide the measured outputs shown in Figs. 3 and 8.
  • the two processing options for measuring the aerated liquid mass flow and density are presented in Fig. 7.
  • the first method assumes that the performance ofthe coriolis for both mass flow and density can be augmented using the methods described in U.S. Patent Application No. 10/892,886 (CiDRA No. CC-0762) and U.S. Provisional Patent Application No. 60/539,640 (CiDRA No. CC-0704), which are incorporated herein by reference.
  • the second approach can be described as follows. To determine the density, the speed of sound (SOS) measurement provided by the flow meter 90 and the pressure (P) measurement provided by a pressure sensor 98 (or may be estimated) are used to calculate gas volume fraction and/ or reduced frequency parameter ofthe coriolis meter operating on the aerated fluid. Next the mixture density is determined by correcting the output ofthe Coriolis-based density meter for the effects of aeration (as described in similar to that described in U.S. Patent Application No.
  • SOS speed of sound
  • P pressure
  • the mixture density is determined by correcting the output ofthe Coriolis-based density meter for the effects of aeration (as described in similar to that described in U.S. Patent Application No.
  • the mostly gas stream 88 is feed in a sonar-based flow meter 99 similar to that described hereinbefore and in U.S. Patent Application No. 10/XXX,XXX (CiDRA No. CC- 0749) filed June 24, 2004, U.S. Patent Application No. 10/166,440 (CiDRA No. CC-0714) and U.S. Patent Application No. 10/762,410 (CiDRA No. CC-0703).
  • the flow meter 99 measures sound speed and volumetric flow rate ofthe gas stream 88, and optionally an orifice plate may be used to measure the gas stream momentum.
  • Figs. 12 - 14 illustrated data recorded from the coriolis meter 16 and the flow meter 90 to determine various parameters ofthe process fluid (e.g., oil/water/gas mixture). Specifically, Fig. 12 shows the density correction ofthe coriolis meter 16. Fig. 13 shows the net oil and water cut ofthe process fluid. Fig. 14 shows a snapshot ofthe oil production being pumped from ground.
  • the process fluid e.g., oil/water/gas mixture
  • Fig. 15 illustrates a gas volume fraction meter 100 of Fig. 2, as described herein before.
  • the GVF meter 100 includes a sensing device 116 disposed on the pipe 14 and a processing unit 124.
  • the sensing device 116 comprises an array of strain-based sensors or pressure sensors 118-121 for measuring the unsteady pressures produced by acoustic waves propagating through the flowl2 to determine the speed of sound (SOS).
  • the pressure signals P ⁇ (t) - P N (t) are provided to the processing unit 124, which digitizes the pressure signals and computes the SOS and GVF parameters.
  • a cable 113 electronically connects the sensing device 116 to the processing unit 124.
  • the analog pressure sensor signals P ⁇ (t) - P (t) are typically 4-20 mA current loop signals.
  • the array of pressure sensors 118-121 comprises an array of at least two pressure sensors 118,119 spaced axially along the outer surface 122 ofthe pipe 14, having a process flow 112 propagating therein.
  • the pressure sensors 118-121 may be clamped onto or generally removably mounted to the pipe by any releasable fastener, such as bolts, screws and clamps. Alternatively, the sensors may be permanently attached to, ported in or integral (e.g., embedded) with the pipe 14.
  • the array of sensors ofthe sensing device 116 may include any number of pressure sensors 118-121 greater than two sensors, such as three, four, eight, sixteen or N number of sensors between two and twenty-four sensors.
  • the accuracy ofthe measurement improves as the number of sensors in the array increases.
  • the degree of accuracy provided by the greater number of sensors is offset by the increase in complexity and time for computing the desired output parameter ofthe flow. Therefore, the number of sensors used is dependent at least on the degree of accuracy desired and the desire update rate ofthe output parameter provided by the apparatus 100.
  • the pressure sensors 118-119 measure the unsteady pressures produced by acoustic waves propagating through the flow, which are indicative ofthe SOS propagating through the fluid flow 12 in the pipe.
  • the output signals (P ⁇ (t)- P N ⁇ ) ofthe pressure sensors 118-121 are provided to a pre-amplifier unit 139 that amplifies the signals generated by the pressure sensors 118-121.
  • the processing unit 124 processes the pressure measurement data P ⁇ (t)- - P N ( and determines the desired parameters and characteristics ofthe flow 12, as described hereinbefore.
  • the apparatus 100 also contemplates providing one or more acoustic sources 127 to enable the measurement ofthe speed of sound propagating through the flow for instances of acoustically quiet flow.
  • the acoustic source may be a device the taps or vibrates on the wall ofthe pipe, for example.
  • the acoustic sources may be disposed at the input end of output end of the array of sensors 118-121, or at both ends as shown.
  • the passive noise includes noise generated by pumps, valves, motors, and the turbulent mixture itself.
  • the apparatus 10 has the ability to measure the speed of sound (SOS) by measuring unsteady pressures created by acoustical disturbances propagating through the flow 12. Knowing or estimating the pressure and/or temperature of the flow and the speed of sound of the acoustic disturbances or waves, the processing unit 124 can determine gas volume fraction, such as that described in U.S. Patent Application No. 10/349,716 (CiDRA Docket No. CC-0579), filed January 23, 2003, U.S. Patent Application No. 10/376,427 (CiDRA Docket No. CC-0596), filed February 26, 2003, U.S. Patent Application No. 10/762,410 (CiDRA Docket No.
  • SOS speed of sound
  • an apparatus 200 of Fig. 16 embodying the present invention has an array of at least two pressure sensors 118,119, located at two locations x ⁇ ,x 2 axially along the pipe 14 for sensing respective stochastic signals propagating between the sensors 118, 119 within the pipe at their respective locations.
  • Each sensor 118,119 provides a signal indicating an unsteady pressure at the location of each sensor, at each instant in a series of sampling instants.
  • the array may include more than two pressure sensors as depicted by pressure sensor 120,121 at location X 3 ,X N -
  • the pressure generated by the acoustic pressure disturbances may be measured through strained-based sensors and/or pressure sensors 118 - 121.
  • the pressure sensors 118-121 provide analog pressure time-varying signals P ⁇ (t),P 2 (t),P 3 (t),P N (t) to the signal processing unit 124.
  • the processing unit 124 processes the pressure signals to first provide output signals 151,155 indicative ofthe speed of sound propagating through the flow 12, and subsequently, provide a GVF measurement in response to pressure disturbances generated by acoustic waves propagating through the flow 12.
  • the processing unit 124 receives the pressure signals from the array of sensors 118- 121.
  • a data acquisition unit 154 digitizes pressure signals P ⁇ (t)-P (t) associated with the acoustic waves 14 propagating through the pipe 114.
  • An FFT logic 156 calculates the Fourier transform ofthe digitized time-based input signals P ⁇ (t) - P N ( and provide complex frequency domain (or frequency based) signals P ⁇ ( ⁇ ),P 2 ( ⁇ ),P 3 ( ⁇ ),P N ( ⁇ ) indicative ofthe frequency content ofthe input signals.
  • a data accumulator 158 accumulates the additional signals P ⁇ (t) - P ⁇ (t) from the sensors, and provides the data accumulated over a sampling interval to an array processor 160, which performs a spatial-temporal (two-dimensional) transform ofthe sensor data, from the xt domain to the k- ⁇ domain, and then calculates the power in the k- ⁇ plane, as represented by a k- ⁇ plot, similar to that provided by the convective array processor 146. To calculate the power in the k- ⁇ plane, as represented by a k- ⁇ plot (see Fig.
  • the array processor 160 determines the wavelength and so the (spatial) wavenumber k, and also the (temporal) frequency and so the angular frequency ⁇ , of various ofthe spectral components ofthe stochastic parameter.
  • the array processor 160 determines the wavelength and so the (spatial) wavenumber k, and also the (temporal) frequency and so the angular frequency ⁇ , of various ofthe spectral components ofthe stochastic parameter.
  • the acoustic ridges represent the concentration of a stochastic - 28 - CC-0765 PCT EV 386515255 US parameter that propagates through the flow and is a mathematical manifestation ofthe relationship between the spatial variations and temporal variations described above.
  • Such a plot will indicate a tendency for k- ⁇ pairs to appear more or less along a line 170,172 with some slope, the slope indicating the speed of sound.
  • the power in the k- ⁇ plane so determined is then provided to an acoustic ridge identifier 162, which uses one or another feature extraction method to determine the location and orientation (slope) of any acoustic ridge present in the left and right k- ⁇ plane.
  • the velocity may be determined by using the slope of one ofthe two acoustic ridges 170,172 or averaging the slopes ofthe acoustic ridges 170,172.
  • an analyzer 164 uses standard so-called beam forming, array processing, or adaptive array-processing algorithms, i.e. algorithms for processing the sensor signals using various delays and weighting to create suitable phase relationships between the signals provided by the different sensors, thereby creating phased antenna array functionality.
  • One such technique of determining the speed of sound propagating through the flow 12 is using array processing techniques to define an acoustic ridge in the k- ⁇ plane as shown in Fig. 17. The slope ofthe acoustic ridge is indicative ofthe speed of sound propagating through the flow 12.
  • the speed of sound (SOS) is determined by applying sonar arraying processing techniques to determine the speed at which the one dimensional acoustic waves propagate past the axial array of unsteady pressure measurements distributed along the pipe 14.
  • the apparatus 200 ofthe present invention measures the speed of sound (SOS) of one-dimensional sound waves propagating through the mixture to determine the gas volume fraction ofthe mixture. It is known that sound propagates through various mediums at various speeds in such fields as SONAR and RADAR fields.
  • the speed of sound propagating through the pipe and flow 12 may be determined using a number of known techniques, such as those set forth in U.S. Patent Application Serial No. 09/344,094, filed June 25, 1999, now US 6,354,147; U.S. Patent Application Serial No. 10/795,111, filed March 4, 2004; U.S. Patent Application Serial No. 09/997,221, filed November 28, 2001, now US 6,587,798; U.S.
  • the analyzer 164 ofthe processing unit 124 provides output signals indicative of characteristics ofthe process flow 12 that are related to the measured speed of sound (SOS) propagating through the flow 12.
  • the analyzer 164 assumes a nearly isothermal condition for the flow 12.
  • Gas Voulume Fraction (GVF) (-B+sqrt(B ⁇ 2-4*A*C))/(2*A)
  • the sound speed of a mixture can be related to volumetric phase fraction ( ⁇ i) ofthe components and the sound speed (a) and densities (p) ofthe component through the Wood equation.
  • ⁇ i volumetric phase fraction
  • p densities
  • One dimensional compression waves propagating within a flow 12 contained within a pipe 14 exert an unsteady internal pressure loading on the pipe.
  • the degree to which the pipe displaces as a result ofthe unsteady pressure loading influences the speed of propagation ofthe compression wave.
  • the relationship among the infinite domain speed of sound and density of a mixture; the elastic modulus (E), thickness (t), and radius (R) of a vacuum-backed cylindrical conduit; and the effective propagation velocity (a e j) for one dimensional compression is given by the following expression:
  • the mixing rule essentially states that the compressibility of a mixture (l/(p a 2 )) is the volumetrically- weighted average ofthe compressibilities ofthe components.
  • the compressibility of gas phase is orders of magnitudes greater than that ofthe liquid.
  • the compressibility ofthe gas phase and the density ofthe liquid phase primarily determine mixture sound speed, and as such, it is necessary to have a good estimate of process pressure to inte ⁇ ret mixture sound speed in terms of volumetric fraction of entrained gas.
  • process pressure The effect of process pressure on the relationship between sound speed and entrained air volume fraction is shown in Fig. 18.
  • processing unit 24 may be implemented in software (using a microprocessor or computer) and/or firmware, or may be implemented using analog and/or digital hardware, having sufficient memory, interfaces, and capacity to perform the functions described herein. While the embodiments ofthe present invention shown in Figs. 2, 20 and 21 shown the pressure sensors 118-121 disposed on the pipe 14, separate from the coriolis meter, the
  • the GVF meter 100 may be integrated with the coriolis meter to thereby provide a single apparatus.
  • the pressure sensors 118-121 may be disposed on one or both ofthe tubes ofthe coriolis meter.
  • the flow meter 100 may process the array of pressure signals to determine the velocity and/or the volumetric flow of fluid flow 12.
  • the flow meter 100 embodying the present invention has an array of at least two pressure sensors 118, 119, located at two locations x ⁇ ,x 2 axially along the pipe 14 for sensing respective stochastic signals propagating between the sensors 118,119 within the pipe at their respective locations.
  • Each sensor 118, 119 provides a signal indicating an unsteady pressure at the location of each sensor, at each instant in a series of sampling instants.
  • the sensor array may include more than two pressure sensors as depicted by pressure sensor 120,121 at location X ,X N -
  • the pressure generated by the convective pressure disturbances may be measured through strained-based sensors and/or pressure sensors 118 - 121.
  • the pressure sensors 118-121 provide analog pressure time-varying signals P ⁇ (t),P 2 (t),P 3 (t),PN(t) to the signal processing unit 124.
  • the processing unit 24 processes the pressure signals to first provide output signals indicative ofthe pressure disturbances that convect with the flow 12, and subsequently, provide output signals in response to pressure disturbances generated by convective waves propagating through the flow 12, such as velocity, Mach number and volumetric flow rate ofthe process flow 12.
  • the processing unit 24 receives the pressure signals from the array of sensors 118- 121.
  • a data acquisition unit 140 e.g., A/D converter
  • the FFT logic calculates the Fourier transform ofthe digitized time-based input signals P ⁇ (t) - P N (0 and provides complex frequency domain (or frequency based) signals P ⁇ ( ⁇ ),P 2 ( ⁇ ),P 3 ( ⁇ ),P]Nj( ⁇ ) indicative ofthe frequency content ofthe input signals.
  • any other technique for obtaining the frequency domain characteristics ofthe signals P ⁇ (t) - P N ( , may be used.
  • the cross-spectral density and the power spectral density may be used to form a frequency domain transfer functions (or frequency response or ratios) discussed hereinafter.
  • One technique of determining the convection velocity ofthe turbulent eddies 88 within the process flow 12 is by characterizing a convective ridge ofthe resulting unsteady - 32 -
  • CC-0765 PCT EV 386515255 US pressures using an array of sensors or other beam forming techniques similar to that described in U.S Patent Application, Serial No. (Cidra's Docket No. CC-0122A) and U.S. Patent Application, Serial No. 09/729,994 (Cidra's Docket No. CC-0297), filed December 4, 200, now US6,609,069, which are inco ⁇ orated herein by reference.
  • a data accumulator 144 accumulates the frequency signals P ⁇ ( ⁇ ) - P N (G>) over a sampling interval, and provides the data to an array processor 146, which performs a spatial-temporal (two-dimensional) transform ofthe sensor data, from the xt domain to the k- ⁇ domain, and then calculates the power in the k- ⁇ plane, as represented by a k- ⁇ plot.
  • the array processor 146 uses standard so-called beam forming, array processing, or adaptive array-processing algorithms, i.e. algorithms for processing the sensor signals using various delays and weighting to create suitable phase relationships between the signals provided by the different sensors, thereby creating phased antenna array functionality.
  • the prior art teaches many algorithms of use in spatially and temporally decomposing a signal from a phased array of sensors, and the present invention is not restricted to any particular algorithm.
  • One particular adaptive array processing algorithm is the Capon method/algorithm. While the Capon method is described as one method, the present invention contemplates the use of other adaptive array processing algorithms, such as MUSIC algorithm.
  • the present invention recognizes that such techniques can be used to determine flow rate, i.e. that the signals caused by a stochastic parameter convecting with a flow are time stationary and have a coherence length long enough that it is practical to locate sensor units apart from each other and yet still be within the coherence length.
  • the array processor 146 determines the wavelength and so the (spatial) wavenumber k, and also the (temporal) frequency and so the angular frequency ⁇ , of various ofthe spectral components ofthe stochastic parameter.
  • the array processor 146 determines the wavelength and so the (spatial) wavenumber k, and also the (temporal) frequency and so the angular frequency ⁇ , of various ofthe spectral components ofthe stochastic parameter.
  • the present invention may use temporal and spatial filtering to precondition the signals to effectively filter out the common mode characteristics P-ommonmode and other long wavelength (compared to the sensor spacing) characteristics in the pipe 14 by differencing adjacent sensors and retain a substantial portion ofthe stochastic parameter associated with the flow field and any other short wavelength (compared to the sensor spacing) low frequency stochastic parameters.
  • suitable turbulent eddies 88 see Fig. 20
  • the power in the k- ⁇ plane shown in a k- ⁇ plot of Fig. 21 shows a convective ridge 200.
  • the convective ridge represents the concentration of a stochastic parameter that convects with the flow and is a mathematical manifestation ofthe relationship between the spatial variations and temporal variations described above.
  • a convective ridge identifier 148 uses one or another feature extraction method to determine the location and orientation (slope) of any convective ridge 200 present in the k- ⁇ plane.
  • a so-called slant stacking method is used, a method in which the accumulated frequency of k- ⁇ - 34 - CC-0765 PCT EV 386515255 US pairs in the k- ⁇ plot along different rays emanating from the origin are compared, each different ray being associated with a different trial convection velocity (in that the slope of a ray is assumed to be the flow velocity or correlated to the flow velocity in a known way).
  • the convective ridge identifier 148 provides information about the different trial convection velocities, information referred to generally as convective ridge information.
  • the analyzer 150 examines the convective ridge information including the convective ridge orientation (slope).
  • the analyzer 150 determines the flow velocity, Mach number and/or volumetric flow.
  • the volumetric flow is determined by multiplying the cross-sectional area ofthe inside ofthe pipe with the velocity ofthe process flow.
  • the pressure sensors including electrical strain gages, optical fibers and/or gratings among others as described herein, may be attached to the pipe by adhesive, glue, epoxy, tape or other suitable attachment means to ensure suitable contact between the sensor and the pipe.
  • the sensors may alternatively be removable or permanently attached via known mechanical techniques such as mechanical fastener, spring loaded, clamped, clam shell arrangement, strapping or other equivalents.
  • the strain gages including optical fibers and/or gratings, may be embedded in a composite pipe. If desired, for certain applications, the gratings may be detached from (or strain or acoustically isolated from) the pipe if desired. It is also within the scope ofthe present invention that any other strain sensing technique may be used to measure the variations in strain in the pipe, such as highly sensitive piezoelectric, electronic or electric, strain gages attached to or embedded in the pipe. Accelerometers may be also used to measure the unsteady pressures. Also, other pressure sensors may be used, as described in a number ofthe aforementioned patents, which are inco ⁇ orated herein by reference. In another embodiment, the sensor may comprise of piezofilm or strips (e.g.
  • PVDF PVDF
  • the invention contemplates any number of sensors in the array as taught in at least one ofthe aforementioned patent applications. Also the invention contemplates that
  • the array of sensors may be mounted or integrated with a tabe of a coriolis meter having shape, such as pretzel shape, U-shaped (as shown), straight tube and any curved shape.
  • the invention further contemplated providing an elongated, non- vibrating (or oscillating) portion that permits a greater number of sensors to be used in the array. While the present invention describes an array of sensors for measuring the speed of sound propagating through the flow for use in inte ⁇ reting the relationship between coriolis forces and the mass flow through a coriolis meter.
  • an ultrasonic device could be used to determine speed of sound ofthe fluid entering.
  • each ofthe pressure sensors 118-121 may include a piezoelectric film sensor to measure the unsteady pressures ofthe fluid flow 12 using either technique described hereinbefore.
  • the piezoelectric film sensors include a piezoelectric material or film to generate an electrical signal proportional to the degree that the material is mechanically deformed or stressed.
  • the piezoelectric sensing element is typically conformed to allow complete or nearly complete circumferential measurement of induced strain to provide a circumferential-averaged pressure signal.
  • the sensors can be formed from PVDF films, copolymer films, or flexible PZT sensors, similar to that described in "Piezo Film Sensors Technical Manual” provided by Measurement Specialties, Inc., which is inco ⁇ orated herein by reference.
  • a piezoelectric film sensor that may be used for the present invention is part number 1-1002405-0, LDT4-028K, manufactured by Measurement Specialties, Inc.
  • Piezoelectric film like piezoelectric material, is a dynamic material that develops an electrical charge proportional to a change in mechanical stress. Consequently, the piezoelectric material measures the strain induced within the pipe 14 due to unsteady pressure variations (e.g., acoustic waves) within the process mixture 12. Strain within the pipe is transduced to an output voltage or current by the attached piezoelectric sensor.
  • the piezoelectrical material or film may be formed of a polymer, such as polarized fluoropolymer, polyvinyhdene fluoride (PVDF).
  • PVDF polyvinyhdene fluoride
  • Another embodiment ofthe present invention include a pressure sensor such as pipe strain sensors, accelerometers, velocity sensors or displacement sensors, discussed hereinafter, that are mounted onto a strap to enable the pressure sensor to be clamped onto the pipe.
  • the sensors may be removable or permanently attached via known mechanical techniques such as mechanical fastener, spring loaded, clamped, clam shell arrangement, strapping or other equivalents.
  • the pipe 12 may be desirable for the pipe 12 to exhibit a certain amount of pipe compliance.
  • two or more pressure sensors may be used around the circumference ofthe pipe 12 at each ofthe axial locations. The signals from the pressure sensors around the circumference at a given axial location may be averaged to provide a cross-sectional (or circumference)
  • the sensors 118-121 may be Bragg grating based pressure sensors, such as that described in US Patent Application, Serial No. 08/925,598, entitled " High Sensitivity Fiber Optic Pressure Sensor For Use In Harsh Environments", filed Sept. 8, 1997, now U.S. Patent 6,016,702, and in US Patent Application, Serial No.
  • a piezo-electronic pressure transducer may be used as one or more ofthe pressure sensors 115-118 and it may measure the unsteady (or dynamic or ac) pressure variations inside the pipe or tabe 14 by measuring the pressure levels inside ofthe tube.
  • the sensors 14 comprise pressure sensors manufactured by PCB Piezotronics.
  • PCB Piezotronics In one pressure sensor there are integrated circuit piezoelectric voltage mode-type sensors that feature built-in microelectronic amplifiers, and convert the high-impedance charge into a low-impedance voltage output.
  • a Model 106B manufactured by PCB Piezotronics is used which is a high sensitivity, acceleration compensated integrated circuit piezoelectric quartz pressure sensor suitable for measuring low pressure acoustic phenomena in hydraulic and - 38 - CC-0765 PCT EV 386515255 US pneumatic systems.
  • the 106B has the unique capability to measure small pressure changes of less than 0.001 psi under high static conditions.
  • the 106B has a 300 mV/psi sensitivity and a resolution of 91 dB (0.0001 psi).
  • the pressure sensors inco ⁇ orate a built-in MOSFET microelectronic amplifier to convert the high-impedance charge output into a low-impedance voltage signal.
  • the sensor is powered from a constant-current source and can operate over long coaxial or ribbon cable without signal degradation.
  • the low-impedance voltage signal is not affected by triboelectric cable noise or insulation resistance-degrading contaminants.
  • Power to operate integrated circuit piezoelectric sensors generally takes the form of a low-cost, 24 to 27 VDC, 2 to 20 mA constant-current supply.
  • a data acquisition system ofthe present invention may inco ⁇ orate constant-current power for directly powering integrated circuit piezoelectric sensors.
  • Most piezoelectric pressure sensors are constructed with either compression mode quartz crystals preloaded in a rigid housing, or unconstrained tourmaline crystals. These designs give the sensors microsecond response times and resonant frequencies in the hundreds of kHz, with minimal overshoot or ringing. Small diaphragm diameters ensure spatial resolution of narrow shock waves.
  • the output characteristic of piezoelectric pressure sensor systems is that of an AC- coupled system, where repetitive signals decay until there is an equal area above and below the original base line.
  • any strain sensing technique may be used to measure the variations in strain in the pipe, such as highly sensitive piezoelectric, electronic or electric, strain gages and piezo-resistive strain gages attached to the pipe 12.
  • Other strain gages include resistive foil type gages having a race track configuration similar to that disclosed U.S. Patent Application Serial No. 09/344,094, filed June 25, 1999, now US 6,354,147, which is inco ⁇ orated herein by reference.
  • the invention also contemplates strain gages being disposed about a predetermined portion of the circumference of pipe 12. The axial placement of and separation distance ⁇ Xi, ⁇ X 2 between the strain sensors are determined as described herein above. - 39 -
  • any other strain sensing technique may be used to measure the variations in strain in the tabe, such as highly sensitive piezoelectric, electronic or electric, strain gages attached to or embedded in the tube 14. While a number of sensor have been described, one will appreciate that any sensor the measures the speed of sound propagating through the fluid may be used with the present invention, including ultrasonic sensors.
  • the coriolis meter described herein before may be any known coriolis meter, such as two inch bent tabe coriolis meter manufactured my MicroMotion Inc. and a two in straight tabe coriolic meter manufactured by Endress & Hauser Inc.
  • the coriolis meters comprise a pair of bent tabes (e.g. U-shaped, pretzel shaped) or straight tabes. While a particular density meter was described for an embodiment, the present invention contemplates any density meter may be used in the embodiments. Similarly, while a particular meter was provided to determine speed of sound propagating through the fluid flow 12, the present invention contemplates any SOS measuring device may be used.
  • the dimensions and/or geometries for any ofthe embodiments described herein are merely for illustrative pu ⁇ oses and, as such, any other dimensions and/or geometries may be used if desired, depending on the application, size, performance, manufacturing requirements, or other factors, in view ofthe teachings herein.

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Abstract

A flow measuring system combines a density measuring device and a device for measuring the speed of sound (SOS) propagating through the fluid flow and/or for determining the gas volume fraction (GVF) of the flow. The GVF meter measures acoustic pressures propagating through the fluids to measure the speed of sound αmix propagating through the fluid to calculate at least gas volume fraction of the fluid and/or SOS. In response to the measured density and gas volume fraction, a processing unit determines the density of non-gaseous component of an aerated fluid flow. For three phase fluid flows, the processing unit can determine the phase fraction of the non-gaseous components of the fluid flow. The gas volume fraction (GVF) meter may include a sensing device having a plurality of strain-based or pressure sensors spaced axially along the pipe for measuring the acoustic pressures propagating through the flow.

Description

An Apparatus and Method for Providing a Density Measurement Augmented for Entrained Gas
Cross-Reference To Related Patent Applications The present invention is a continuation-in-part of U.S. Patent Application No.
10/892,886 filed July 15, 2004, which claimed the benefit of U.S. Provisional Patent Application No. 60/487,832 filed July 15, 2003, (Attorney Docket CC-0641); and claims the benefit of U.S. Provisional Patent Application No. 60/548,215 filed February 27, 2004, (Attorney Docket CC-0720); U.S. Provisional Patent Application No. 60/571,903 filed May 17, 2004, (Attorney Docket CC-0740); U.S. Provisional Patent Application No. 60/579,448 filed June 14, 2004, (Attorney Docket CC-0745); U.S. Provisional Patent Application No. 60/570,321 filed May 12, 2004, (Attorney Docket CC-0739); U.S. Provisional Patent Application No. 60/539,640 filed January 28, 2004, (Attorney Docket CC-0704); U.S. Provisional Patent Application No. 60/524,964 filed November 25, 2003, (Attorney Docket CC-0683); U.S. Provisional Patent Application No. 60/512,794 filed October 20, 2003, (Attorney Docket CC-0668); U.S. Provisional Patent Application No. 60/510,302 filed October 10, 2003, (Attorney Docket CC-0664); U.S. Provisional Patent Application No. 60/504,785 filed September 22, 2003, (Attorney Docket CC-0657); U.S. Provisional Patent Application No. 60/503,334 filed September 16, 2003, (Attorney Docket CC-0656); U.S. Provisional Patent Application No. 60/491,860 filed August 1, 2003, (Attorney Docket CC- 0643), which are all incorporated herein by reference.
Technical Field This invention relates to an apparatus for measuring the density of a fluid flow having entrained gas therein, and more particularly to an apparatus that measures the speed of sound propagating through the flow to determine the gas volume fraction ofthe flow in the process to augment or correct the density measurement of a density meter and/or to provide a composition measurement compensated for entrained gas.
- 1 - CC-0765 PCT EV 386515255 US Background Art Density meters are commonly used instruments in industrial processes. Common types of density meters include nuclear densitometers, vibrating vane densitometers and Coriolis flow meters having a density measurement as a by-product measurement. In most applications, density measurements are used to discern bulk properties of the process fluid. Typically, density measurements are intended to provide information about the liquid and solid phases of a process fluid. These measurements get confound when an rmknown amount of entrained air is present. For a two-component mixture, knowing the component densities and accurately measuring the mixture density provides a means to determine the phase fractions of each of * the two components. However, the presence of a third phase, such as entrained air (or gas) confounds this relationship. Typically, there is not significant contrast in the densities of the liquid components, which results in large errors in phase fraction determination resulting from small levels of entrained air. The measurement of slurries used in the paper and pulp industries and in other industries particularly presents problems in the production of paper. Slurries commonly used in the paper and pulp industry are mostly water and typically contain between 1% and 10% pulp content by mass. Monitoring the gas volume fraction of a slurry can lead to improved quality and efficiency ofthe paper production process. Processes run in the paper and pulp industry can often, either intentionally or unintentionally, entrain gas/air. Typically, this entrained air results in measurement errors in process monitoring equipment such as density meters. Industry estimates indicate that entrained air levels of 2-4% are common. Since most density meters are unable to distinguish between air and liquid, interpreting their output as a density measurement or composition measurement would result in an overestimate ofthe density ofthe liquid or slurry present at the measurement location. Similarly, the void fraction ofthe air within the pipe can cause errors in compositional measurements. Thus, providing a method and apparatus for measuring entrained air in paper and pulp slurries, for example, would provide an accurate measurement ofthe entrained air and would provide a means to correct the output of density meters.
CC-0765 PCT EV 386515255 US As suggested, multiphase process flow rate is a critical process control parameter for the paper and pulp industry. Knowing the amounts of liquid, solids and entrained gases flowing in process lines is key to optimizing the overall the papermaking process. Unfortunately, significant challenges remain in the achieving accurate, reliable, and economical monitoring of multiphase flow rates of paper and pulp slurries. Reliability challenges arise due the corrosive and erosive properties ofthe slurry. Accuracy challenges stem from the multiphase nature ofthe slurries. Economical challenges arise from the need to reduce total lifetime cost of flow measurement, considering installation and maintenance costs in addition to the initial cost ofthe equipment. Currently, there is an unmet need for multiphase flow measurement in the processing industry, such as the paper and pulp industry. Real time flow measurement is typically restricted to monitoring the total volumetric flow rate in a process line without providing information on the composition ofthe process mixture. Similarly, well head monitoring represents a difficult technical challenge with the presence of entrained gas. Metering well head production rates is a long standing challenge for the oil and gas industry. Performing accurate and timely monitoring ofthe production rates has many benefits, which include optimizing overall field and specific well production. The difficulty is due in no small part to the extreme variability of produced fluids which can include various types and mixtures of oil, water, gas, and solid particles. Many companies have developed various types of three phase meters designed to address the well head flow metering market. These products have met relatively limited commercial success due to a combination of performance, accuracy, and cost issues. This disclosure provide an means and apparatus for well head monitoring that combines multiple existing technologies in to system that should meet a wide range of cost and performance goals. It is proposed herein to use sonar-based entrained gas measurement to determine the entrained gas level in conjunction with any mixture density measurement to improve the accuracy and therefore value ofthe density measurement. A sound speed based entrained gas measurement can accurately determine the entrained gas in an aerated mixture without precise knowledge of the composition of either the non -gas components of the multiphase mixture ofthe composition of gas itself. Thus, the entrained gas levels can be determined - 3 - CC-0765 PCT EV 386515255 US essentially independent ofthe determination ofthe liquid properties. The accuracy could be improved using the sound speed measurement and mixture density simultaneously, but is not required. Determining the entrained gas level enables the density measurement to determine the properties of non-gas component ofthe multiphase mixture with the same precision as if the gas was not present. This capability also enables the density meters to provide significantly enhanced compositional information for aerated mixtures.
Summary of the Invention Objects ofthe present invention include an apparatus having a device for determining the speed of sound propagating within a fluid flow in a pipe to determine the gas volume fraction of a process fluid or flow flowing within a pipe, and augment to improve the accuracy of a density measurement of a density meter and/or to provide a composition measurement compensated for entrained gas. According to the present invention, a flow measuring system for determining the density of a fluid flowing in a pipe is provided. The measuring system comprises a density meter that provides a density signal indicative ofthe density ofthe fluid flowing in the pipe. A flow measuring device measures the speed of sound propagating through the fluid. The measuring device provides an SOS signal indicative ofthe speed of sound propagating through the fluid and/or a GVF signal indicative ofthe gas volume fraction ofthe fluid. A processing unit determines the density ofthe non-gaseous component ofthe aerated fluid in response to the SOS signal and/or the GVF signal and the density signal. According to the present invention, a well head metering system for measuring density of non-gaseous components of a three phase fluid flowing in a pipe is provided. The metering system comprises a density meter that provides a density signal indicative of the density ofthe fluid flowing in the pipe. A flow measuring device measures the speed of sound propagating through the fluid. The measuring device provides an SOS signal indicative ofthe speed of sound propagating through the fluid and/or a GVF signal indicative ofthe gas volume fraction ofthe fluid. A processing unit determines the density ofthe non-gaseous component ofthe aerated fluid in response to the SOS signal and/or the GVF signal and the density signal. - 4 - CC-0765 PCT EV 386515255 US The foregoing and other objects, features and advantages ofthe present invention will become more apparent in light ofthe following detailed description of exemplary embodiments thereof.
Brief Description of the Drawings Fig. 1 is a schematic illustration of a flow measuring system for providing a density and/or composition measurement augmented for entrained gas within an aerated fluid flow passing within a pipe, in accordance with the present invention. Fig. 2 is a schematic illustration of another flow measuring system for providing a density and/or composition measurement augmented for entrained gas within an aerated fluid flow passing within a pipe, in accordance with the present invention. Fig. 3 is a function block diagram of a processing unit of flow measuring system similar to that of Fig. 1, in accordance with the present invention. Fig. 4 is a schematic illustration of a flow measuring system for providing a density and/or composition measurement provided by a gamma densitometer augmented for entrained gas within a bitumen froth flow passing within a pipe, in accordance with the present invention. Fig. 5 is a plot ofthe relative error in the interpreted percent solids versus the gas volume fraction in a bitumen froth flow, in accordance with the present invention. Fig. 6 is a schematic illustration of a flow measuring system for providing a density and/or composition measurement provided by a coriolis meter augmented for entrained gas within a bitumen froth flow passing within a pipe, in accordance with the present invention. Fig. 7 is a function block diagram of a processing unit of flow measuring system similar to that of Fig. 6, in accordance with the present invention. Fig. 8 is a schematic illustration of model of a coriolis meter having aerated fluid flowing therethrough that accounts for compressibility and inhomogeniety ofthe aerated fluid, in accordance with the present invention. Fig. 9 is a schematic illustration of a well head monitoring system for providing a density and/or composition measurement provided by a coriolis meter augmented for entrained gas within a bitumen froth flow passing within a pipe, in accordance with the present invention. - 5 - CC-0765 PCT EV 386515255 US Fig. 10 is a plot of three phase composition of an aerated hydrocarbon and water fluid flow as a function of sound speed and flow density, in accordance with the present invention. Fig. 11 is another embodiment of a function block diagram of a processing unit of flow measuring system similar to that of Fig. 7, in accordance with the present invention. Fig. 12 is a plot the density correction and gas volume fraction of a fluid determined by a flow system embodying the present invention Fig. 13 is a plot of net oil error and watercut of three phase fluid flow determined by a flow system embodying the present invention. Fig. 14 is a plot of a snap shot of three phase fluid flow determined by a flow system embodying the present invention. Fig. 15 is a schematic block diagram of a gas volume fraction meter, in accordance with the present invention. Fig. 16 is a schematic block diagram of another embodiment of gas volume fraction meter, in accordance with the present invention. Fig. 17 is a kω plot of data processed from an array of pressure sensors use to measure the speed of sound of a fluid flow passing in a pipe, in accordance with the present invention. Fig. 18 is a plot ofthe speed of sound ofthe fluid flow as a function ofthe gas volume fraction over a range of different pressures, in accordance with the present invention. Fig. 19 is a schematic block diagram of a volumetric flow meter having an array of sensor, in accordance with the present invention. Fig. 20 is a graphical cross-sectional view ofthe fluid flow propagating through a pipe, in accordance with the present invention. Fig. 21 is a kω plot of data processed from an array of pressure sensors use to measure the velocity of a fluid flow passing in a pipe, in accordance with the present invention.
- 6 -
CC-0765 PCT EV 386515255 US Best Mode for Carrying Out the Invention Density meters 16 provide a measurement ofthe density of a fluid flow 12 passing through a pipe 14. As described in detail hereinbefore, a density meter provides erroneous density measurements in the presence of entrained gas (e.g., bubbly gas) within the fluid flow. The present invention provides a means for augmenting or compensating the density meter to determine improved density measurements that provides the density ofthe non-gas portion ofthe fluid flow 12. The density meter may be any device capable of measuring the density ofthe fluid flow, such as nuclear densitometers, vibrating vane densitometers and Coriolis flow meters, which provide a density measurement as a by-product measurement. The present invention proposes the use of sonar-based entrained gas measurements to determine the entrained gas level in conjunction with any density measurement of a mixture flowing in a pipe to improve the accuracy, and therefore value ofthe density measurement. A sound speed based entrained gas measurement can accurately determine the entrained gas in an aerated mixture without precise knowledge ofthe composition of either the non -gas components ofthe multiphase mixture or the composition of gas itself. Thus, the entrained gas levels can be determined essentially independent ofthe determination ofthe liquid properties. The accuracy could be improved using the sound speed measurement and mixture density simultaneously, but is not required. Determining the entrained gas level enables the density measurement to determine the properties of non- gas component ofthe multiphase mixture with the same precision as if the gas was not present. This capability also enables the density meters to provide significantly enhanced compositional information for aerated mixtures. As shown in Fig. 1, one embodiment of a flow measuring system 10 embodying the present invention includes a density meter 16, a speed of sound (SOS) measuring apparatus 18 and a processing unit 20 to provide any one or more ofthe following parameters ofthe fluid flow 12, namely, gas volume fraction, speed of sound propagating through the fluid flow, uncompensated density, compensated density and composition. The fluid flow may be any aerated fluid or mixture including liquid, slurries, solid/liquid mixture, liquid/liquid mixture, solid/solid mixture and any other multiphase flow having entrained gas.
- 7 - CC-0765 PCT EV 386515255 US In this embodiment, the density meter 16 provides a signal 22 indicative ofthe density ofthe fluid flow 12 not augmented or compensated for entrained gas. The SOS measuring apparatus 18 provides an SOS signal 24 indicative ofthe speed of sound propagating through the fluid flow. A processing unit 20 determines at least one ofthe parameters ofthe fluid flow described hereinbefore in response to the SOS signal 24 and density signal 22. Pressure and/or temperature signals 26,28 may also be provided to the processing unit 20, which may be used to provide more accurate measurements ofthe gas volume fraction. The pressure and temperature may be measured by known means or estimated. The SOS measuring device 18 includes any means for measuring the speed of sound propagating through the aerated flow 12. One method includes a pair of ultra-sonic sensors axially spaced along the pipe 14, wherein the time of flight of an ultrasonic signal propagating between an ultra-sonic transmitter and receiver is indicative ofthe speed of sound. Depending on the characteristics ofthe flow, the frequency ofthe ultra-sonic signal must be relating low to reduce scatter within the flow. The meter is similar as that described in U.S. Patent Application No. 10/756,922 (CiDRA Docket No. CC-0699) filed on January 13, 2004, which is incorporated herein by reference. Alternatively, a flow measuring system 30 embodying the present invention, as shown in Figs. 2, 7 and 11, provides a gas volume fraction (GVF) meter 100 for determining the gas volume fraction ofthe fluid flow 12, which will be described in greater detail hereinafter. The GVF meter 100 comprises a sensing device 116 having a plurality of strain-based or pressure sensors 118-121 spaced axially along the pipe for measuring the acoustic pressures 190 propagating through the flow 12. The GVF meter determines and provides a first signal 27 indicative ofthe SOS propagating through the fluid flow 12 and a second signal 29 indicative ofthe gas volume fraction (GVF) ofthe flow 12, which will be described in greater detail hereinafter. The gas volume fraction meter 100 is similar to that described in U.S. Patent Application No. 10/762,410 (Cidra Docket No. CC-0703) filed on January 21, 2004, which is incorporated herein by reference. The processing unit 32 determines at least one ofthe parameters ofthe fluid flow described hereinbefore in response to the SOS signal 24 and/or GVF signal 29, and the density signal 22.
CC-0765 PCT EV 386515255 US Fig. 3 illustrates a functional block diagram 40 ofthe flow measuring system 30 of Fig. 2. As shown, the GVF meter 100 measures acoustic pressures propagating through the fluids 12, thereby measuring the speed of sound α^ propagating through the fluid flow 12 at 42. The GVF meter 100 calculates the gas volume fraction ofthe fluid using the measured speed of sound at 44. The GVF meter may also use the pressure ofthe process flow to determine the gas volume fraction. The pressure may be measured or estimated at 46. For determining an improved density 48 (i.e., density of non-gas portion of flow 12), the calculated gas volume fraction 29 is provided to the processing unit 32. Knowing the gas volume fraction 29 (and/or speed of sound 27 propagating through the flow) and the measured density 22, the processing unit 32 can determine density ofthe non-gas portion of the multiphase flow 12. Specifically, the density (βmιx) 22 of an aerated flow 12 is related to the volumetric phase fraction ofthe components (øj) and the density ofthe components (βi).
Figure imgf000011_0001
Where continuity requires:
∑ 1=1 Λ = ι
For example, for a two-component fluid flow: P mix ~~
Figure imgf000011_0002
ψtiongas "t" f gas ψgas therefore, . = ( pmn - ps_ φs_ )/φ g_, = ( pma - pg_ φs_ )/l-φs , wherein .o„sas— l-φm Assuming the density ofthe gas (pgas) is substantially less than the density ofthe non-gas portion (pnongas) ofthe fluid flow 12, the equation can be reduced to:
Figure imgf000011_0003
CC-0765 PCT EV 386515255 US wherein pmix is the density ofthe mixture, Pnongas, ønongas are the density and phase fraction, respectively, of a non-gas component ofthe fluid flow, and pgas, øgas are the density and phase fraction, respectively, ofthe entrained gas within the mixture. Therefore, knowing the density (pgas) ofthe gas/air, the measured gas volume fraction ofthe gas (øgas), and the improved density measurement (pmix) ofthe aerated flow to be compensated for entrained gas enable the density (pn0ngas) ofthe non-gas portion ofthe aerated flow 12 to be determined, which provides improved compositional information of the aerated flow 12. For instances when the density ofthe gas component is substantially greater than the non-gas component, knowing just the measured density (pmix) 22 ofthe aerated flow 12 density ofthe gas component and the gas volume fraction (øgas) 29 is sufficient to determine the density (pn0ngas) 48 ofthe non-gas component ofthe flow 12. The present invention further contemplates determining improved compositional information ofthe aerated flow 12. When a two-component mixture 12 includes a third component of entrained gas or gas, the relationship is as follows:
Pmix = p ιφ t + p ιφ ι + p_» φ_« therefore, φ ι = [ pmjx - ps_ φs_ - p ι(l - φs_ ) ]/(
Figure imgf000012_0001
- pi ), where φ 2 = 1 - φ ι - φs_ assuming the density of the gas (pgas) is substantially less than the density ofthe non-gas portion (pnongas) ofthe fluid flow 12, the equation can be reduced to:
Figure imgf000012_0002
Therefore, knowing the density (pgas) ofthe gas/air and the measured density ofthe gas volume fraction (øgas) enables density measurement (pmix) ofthe mixture to be compensated for entrained gas and provide a density measurement of only the two- component mixture that does not include the density ofthe entrained air/gas at 50. Furthermore, knowing the densities of each ofthe components ofthe mixture (pi, p2) and the density of the gas/air (pgas), and knowing the measured densities ofthe mixture
- 10 - CC-0765 PCT EV 386515255 US (Pmix) and gas volume fraction (øgas) enable the volume fraction of each component (øi, ø2) to be determined at 52. Referring to Fig. 4, one example of an application for the flow measuring system 30 is in the oil sands industry, where monitoring entrained sand levels in bitumen / water froths is an important application. However, due to the presence of unknown amount of entrained air in the froth, an accurate measurement ofthe amount of particles (e.g., sand) is not possible using a gamma densitometer 60 operating on a bitumen froth mixture 12, which contains a small amount of entrained air and sand particles entrained in a liquid continuous mixture of bitumen and water. The density of bitumen and water (pi) are nearly identical for most applications, therefore, variations in the bitumen / water cut of liquid phase has very limited effect on the mixture density. Variations in the mixture density are therefore due to the air and particles. The density ofthe particles (p2) and the density ofthe air (pgas) are known. By measuring the gas volume fraction ofthe entrained air (øgas) and density of the fluid flow (pmix) directly and knowing the density ofthe particles (p2) and the density of the bitumen and water (pi), the gamma densitometer 60 in combination with the entrained gas meter 100 provides a means to determine the amount of sand left (ø2) in the slurry as well as other parameters ofthe mixture, as described hereinbefore. Fig. 5 is a plot ofthe relative error in interpreted percent of solids in a bitumen froth flow versus the gas fraction of entrained air/gas in the flow 12. As shown, a bitumen froth flow having 1 % of entrained air therein results in an approximately 20% error in percent solids (e.g., sand) in the bitumen froth flow. As shown in Fig. 4, the density measurement (pn0ngas) and composition measurement (øι,ø2) described above can be done on the full pipe, or as shown in Fig. 6, on a slip stream pipe 70. Referring to Fig. 6, a slip stream pipe 70 enables the use of a coriolis meter 72 to measure the density (pmix) by providing a smaller diameter pipe. A further benefit of a sonar-based entrained air measurement is achieved when the sound speed measurement is used to enhance the accuracy ofthe coriolis on the aerated mixture, similar to that described in U.S. Patent Application No. 10/892,886 (Cidra Docket No. CC-0762), filed on July 15, 2004, which is incorporated herein by reference. While the entrained gas meter 100 is shown mounted on the full pipe in Fig. 6, the present invention contemplates that the entrained air meter may be mounted on the slip stream pipe 70.
- 11 - CC-0765 PCT EV 386515255 US As shown in Figs. 4 and 6, the apparatus 100 for measuring the gas volume fraction ofthe flow 12 may also provide a velocity measurement and a volumetric flow rate measurement ofthe flow, similar to that described in U.S. Patent Application No. 10/712,818 (Cidra Docket No. CC-0675), filed on November 12, 2003, U.S. Patent Application No. 10/712,833 (Cidra Docket No. CC-0676), filed on November 12, 2003, U.S. Patent Application No. 10/766,440 (Cidra Docket No. CC-0714), filed on January 27, 2004, and U.S. Patent Application No. 10/XXX,XXX (Cidra Docket No. CC-0749), filed on June 24, 2004, which are incorporated herein by reference. Coriolis meters provide a measurement ofthe mass flow and/or density of a fluid flow 12 passing through a pipe 14. A coriolis meter provides erroneous mass flow and density measurements in the presence of entrained gas within the fluid flow (e.g., bubbly gas). The present invention may also provide a means for compensating the coriolis meter to provide corrected or improved density and/or mass flow measurements. While the gas volume fraction meter 100 may be used to determine the density of the non-gas component ofthe flow 12 and the composition of a multi-phase flow 12 as described hereinbefore, the GVF meter may be also used to compensate or augment the output density measurement and the mass flow measurement of a coriolis meter, similar to that described in U.S. Patent Application No. 10/892,886 (CiDRA Docket No. CC-0762) filed July 15, 2004, which is incorporated herein by reference. In this embodiment, the coriolis meter 16 provides a frequency signal (fnat) indicative ofthe natural frequency ofthe fluid 12 loaded tubes ofthe coriolis meter and the phase signal (Δφ) indicative ofthe phase lag in the tubes ofthe coriolis meter. The GVF meter 100 or SOS measuring apparatus 18 provides an SOS signal 24 indicative ofthe speed of sound propagating through the fluid flow. A processing unit 32 processes the frequency signal, the phase signal and the SOS signal to provide at least one ofthe parameters ofthe fluid flow described hereinbefore, including the mass flow ofthe flow 12. Pressure and/or temperature signals may also be provided to the processing unit 32, which may be used to provide more accurate measurements ofthe gas volume fraction. The pressure and temperature may be measured by known means or estimated. The coriolis meter may be any known coriolis meter, such as two inch bent tube coriolis meter manufactured my MicroMotion Inc. and a two in straight tube coriolic meter - 12 - CC-0765 PCT EV 386515255 US manufactured by Endress & Hauser Inc. The coriolis meters comprise a pair of bent tubes (e.g. U-shaped, pretzel shaped) or straight tubes as will be described hereinafter. Fig. 7 illustrates a functional block diagram 80 ofthe flow measuring system of Fig. 2. As shown, the GVF meter 100 measures acoustic pressures propagating through the fluids to measure the speed of sound α . The GVF meter calculates at least gas volume fraction ofthe fluid and/or the reduced natural frequency using the measured speed of sound. The GVF meter may also use the pressure ofthe process flow to determine the gas volume fraction. For determining an improved density for the coriolis meter, the calculated gas volume fraction and/or reduced frequency is provided to the processing unit 21. The improved density is determined using analytically derived or empirically derived density calibration models (or formulas derived therefore), which is a function ofthe measured natural frequency and at least one ofthe determined GVF, reduced frequency and speed of sound, or any combination thereof, which will be described in greater detail hereinafter. The improved density measurement is the density of the aerated flow passing through the pipe. The present invention further contemplates determining improved compositional information ofthe aerated flow. In other words, knowing the speed of sound propagating through the flow and the improved density, the processing unit 21 can determine phase fraction of each component ofthe multiphase flow. The present invention also contemplates compensating or improving the mass flow rate measurement ofthe coriolis meter 16, as shown in Fig. 7. For determining an improved mass flow rate for the coriolis meter, the calculated gas volume fraction and/or reduced frequency is provided to the processing unit 32. The improved mass flow rate is determined using analytically derived or empirically derived mass flow calibration models (or formulas derived therefore), which is a function ofthe measured phase difference (Δφ) and at least one ofthe determined GVF, reduced frequency and speed of sound, or any combination thereof, which will be described in greater detail hereinafter. For determining an improved density for the coriolis meter, the calculated gas volume fraction and/or reduced frequency is provided to the processing unit 32. The improved density is determined using analytically derived or empirically derived density calibration/parameter models (or
- 13 - CC-0765 PCT EV 386515255 US formulas derived therefore), which is a function ofthe measured natural frequency and at least one ofthe determined GVF, reduced frequency and speed of sound, or any combination thereof, which will be described in greater detail hereinafter. The improved mass flow measurement is the mass flow rate ofthe aerated flow passing through the pipe. While the improved mass flow and improved density measurement may be a function GVF, SOS and reduced frequency, the present invention contemplates these improved measurements may be a function of other parameters, such a gas damping _"gas. Further, while the functional block diagram illustrates that the processing unit 32 may improve both the density measurement and the density measurement ofthe coriolis meter 16, the invention contemplates that the processing may only compensate or improve one the density and mass flow rate parameters. Results for a lumped parameter model of Fig. 8 presented hereinafter confirm long recognized accuracy degradation of vibrating tube density meters attributed to aeration. The models can be used to illustrate qualitatively the role of several non-dimensional parameters that govern the performance ofthe meters in aerated fluids. It can be concluded from these models that gas volume fraction plays a dominant role, with several other parameters including gas damping _~gas and reduced frequency also influencing performance. The present invention provides an approach in which a speed-of-sound measurement ofthe process fluid is integrated with the natural frequency measurement of a vibrating tube density meter to form a system with an enhanced ability to operate accurately in aerated fluids. Introducing a real time, speed-of-sound measurement address the effects of aeration on multiple levels with the intent to enable vibrating-tube-based density measurement to continue to report liquid density in the presence of entrained air with accuracy approaching that for a non-aerated liquid. Firstly, by measuring the process sound speed with process pressure, the aeration level ofthe process fluid can be determined with high accuracy on a real time basis. Secondly, the real time measurements of sound speed, and the derived measurement of gas volume fraction, are then utilized with empirically derived correction factors to improve the interpretation ofthe measured natural frequency ofthe vibrating tubes in terms ofthe density ofthe aerated fluid. Thirdly, the combined knowledge of aerated mixture density and aerated mixture sound speed, enable the determination ofthe non-aerated liquid component density, providing improved compositional information. - 14 - CC-0765 PCT EV 386515255 US O 2005/012881
Note liquids phase includes pure liquids, mixtures of liquids, as well as liquid / solid mixtures. To illustrate the fundamental ways in which aeration impacts vibrating-tube density measurements, a simplified, lumped parameter model for the effects of aeration in vibrating tubes is developed. The model illustrates that the effects of aeration can be attributed to at least two independent mechanisms; 1) the density inhomogeniety of discrete gas bubbles and 2) increased mixture compressibility due to aeration. This basic framework provides an accurate means to determine process fluid density under most operating conditions. However, some ofthe fundamental assumptions regarding the interaction ofthe fluid 12 and the structure can deteriorate under different operating conditions. Specifically, aerated fluids in oscillating tubes behave differently from single phase fluids in two important ways; increased compressibility, and fluid inhomogeneity.
Fluid Compressibility It is well known that most aerated liquids are significantly more compressible than non-aerated liquids. Compressibility of a fluid is directly related to the speed of sound and density ofthe fluid 12. Mixture density and sound speed can be related to component densities and sound speed through the following mixing rules which are applicable to single phase and well- dispersed mixtures and form the basis for speed-of-sound-based entrained air measurement.
Figure imgf000017_0001
JV where pmιx = ∑ PtΦ, and κmιx is the mixture compressibility, and φ, is the ;=1 component volumetric phase fraction. Consistent with the above relations, introducing air into water dramatically increases the compressibility ofthe mixture 12. For instance, at ambient pressure, air is approximately 25,000 times more compressible than water. Thus, adding 1% entrained air increases the compressibility ofthe mixture by a factor of 250. Conceptually, this increase in compressibility introduces dynamic effects that cause the dynamic of behavior ofthe - 15 - CC-0765 PCT EV 386515255 US aerated mixture within the oscillating tube to differ from that ofthe essentially incompressible single-phase fluid. The effect of compressibility ofthe fluid 12 can be incorporated into a lumped parameter model of a vibrating tube as shown schematically in Fig. 8. The stiffness ofthe spring represents the compressibility ofthe fluid. As the compressibility approaches zero, the spring stiffness approaches infinity. As before the effective mass ofthe fluid 12 is proportional to the density ofthe fluid and the geometry ofthe flow tube. The natural frequency ofthe first transverse acoustic mode in a circular duct can be used to estimate an appropriate spring constant for the model
Figure imgf000018_0001
Note that this frequency corresponds to a wavelength of an acoustic oscillation of approximately two diameters, i.e., this transverse mode is closely related to a "half wavelength" acoustic resonance ofthe tube. For low levels of entrained air, the frequency ofthe first transverse acoustic mode is quite high compared to the typical structural resonant frequencies of coriolis meters of 100 Hz, however, the resonant acoustic frequency decreases rapidly with increased levels of entrained air. In characterizing aeroelastic systems, it is often convenient to define a reduced frequency parameter to gauge the significance ofthe interaction between coupled dynamic systems. For a vibrating tube filled with fluid, a reduced frequency can be defined as a ratio ofthe natural frequency ofthe structural system to that ofthe fluid dynamic system. J struct red mix Where fstruct is the natural frequency ofthe tabes in vacuum, D is the diameter ofthe tubes, and amiχ is the sound speed ofthe process fluid. For this application, as the reduced frequency becomes negligible compared to 1, the system approaches quasi-steady operation. In these cases, models, which neglect the compressibility ofthe fluid is likely to be suitable. However, the effects of unsteadiness increase with increasing reduced frequency. For a - 16 -
CC-0765 PCT EV 386515255 US O 2005/012881
given coriolis meter, mixture sound speed has the dominant influence of changes in reduced frequency. When considering coriolis meters of varying design parameters, increases in tube natural frequency or tube diameter will increase the effects of unsteadiness for a given level of aeration.
Fluid Inhomogeneity In additional to dramatically increasing the compressibility ofthe fluid 12, aeration introduces inhomogeneity to the fluid. For flow regimes in which the gas is entrained in a liquid-continuous flow field, the first-order effects ofthe aeration can be modeled using bubble theory. By considering the motion of an incompressible sphere of density of po contained in an inviscid, incompressible fluid with a density of p and set into motion by the fluid show that the velocity ofthe sphere is given by:
3p sphere ■ V p + 2p0 fl, uid
For most entrained gases in liquids, the density ofthe sphere is orders of magnitude below that ofthe liquid and the velocity of bubble approaches three times that ofthe fluid. Considering this result in the context ofthe motion of a sphere in a cross section of a vibrating tube, the increased motion ofthe sphere compared to the remaining fluid must result in a portion ofthe remaining fluid having a reduced level of participation in oscillation, resulting in a reduced, apparent system inertia. In a lumped parameter model, a gas bubble of volume fraction φ is connected across a fulcrum 42 to a compensating mass of fluid with volume 2T, where T is the gas volume fraction ofthe flow. The fulcrum is rigidly connected to the outer pipe 14. The effects of viscosity can be modeled using a damper connected to restrict the motion ofthe gas bubble with respect to the rest ofthe liquid and the tube itself. The remaining volume of liquid in the tube cross section (1-3IJ is filled with an inviscid fluid. In the inviscid limit, the compensating mass of fluid (2T) does not participate in the oscillations, and the velocity of the mass-less gas bubble becomes three times the velocity ofthe tube. The effect of this relative motion is to reduce the effective inertia ofthe fluid inside the tube to (1-3T. times - 17 - CC-0765 PCT EV 386515255 US O 2005/012881
that presented by a homogeneous fluid-filled the tube. In the limit of high viscosity, the increased damping constant minimizes the relative motion between the gas bubble and the liquid, and the effective inertia ofthe aerated fluid approaches 1-T. The effective inertia predicted by this model of an aerated, but incompressible, fluid oscillating within a tube agrees with those presented by (Hemp, et al, 2003) in the limits of high and low viscosities. One should appreciate that the processing unit may use these models independently or together in a lumped parameter model.
Combined Lumped Parameter Model Models were presented with the effects of aeration on vibrating tube density meters in which the effects of compressibility and inhomogeniety were addressed independently.
Fig. 8 shows a schematic of a lumped parameter model that incorporates the effects of compressibility and inhomogeniety using the mechanism-specific models developed above. The equations of motion ofthe above lumped parameter model, assuming solutions in the form of esτ where s is the complex frequency, can be expressed in non-dimensional form as:
Figure imgf000020_0001
The parameters governing the dynamic response ofthe model are defined in the following Table 1.
Svmbol Descrwtion Definition a Mass ratio πifluid mstruot Q Natural Frequency Ratio fi>fluid/<ϊ>stru-t ζf Critical Damping Ratio of Fluid System bfluid/(2mfiUjdC0flUid) ζs Critical Damping Ratio of Structural Dstruc'(2nistruct(Bsstruc) System ζg Critical Damping Ratio of Structural bgas/(2mflUjdωstruct) System 18 -
CC-0765 PCT EV 386515255 US τ Non-dimensional time t Ostruct y Non-dimensional temporal derivative of x dx/dτ Table 1: Definition of Non-dimensional Parameters Governing the Equation of Motion for the Lumped Parameter Model of a Tube Filled with a Compressible, Aerated Fluid
Solving the sixth-order eigenvalue problem described above provides a means to assess the influence ofthe various parameters on the observed density. The natural frequency ofthe primary tube mode predicted by the eigenvalue analysis is input into the frequency / density from the quasi-steady, homogeneous model to determine the apparent density ofthe fluid 12 as follows.
apparent
Figure imgf000021_0001
As a baseline condition, a "representative" coriolis meter with parameters given in Table 2 was analyzed.
Parameter Descrivtion Value fs Structural Frequency of Tubes 100 Hz α Mass ratio 1.25 Sstruot Critical Damping Ratio - 0.01 structure ζfluid Critical Damping Ratio - fluid 0.01 gas Critical Damping Ratio - gas 0.01 Q Frequency Ratio As determined by sound speed of air / water at STP and structural parameters D Tube diameter 1.0 inches Table 2: Parameters Defining the Baseline Vibrating Tube Density Meter
For a given coriolis meter, the level of aeration has a dominant effect on the difference between actual and apparent mixture density. However, other parameters identified by the lumped parameter model also play important roles. For example, the damping parameter associated with the movement ofthe gas bubble relative to the fluid within the tube, ζgas, is a parameter governing the response ofthe system to aeration. For ζgas approaching zero, the apparent density approaches 1-3T, i.e., the meter under reports - 19 -
CC-0765 PCT EV 386515255 US the density ofthe aerated mixture by 2T. However, as the ζgas is increased, the apparent density approaches the actual fluid density of 1-T. The influence of compressibility is function of gas volume fraction for a range of meters differing only in natural frequency ofthe tubes. The natural frequency ofthe tubes, primarily through the influence of the reduced frequency of operation at a given level of aeration can significantly influence the relation between the actual and apparent density of an aerated fluid.
Mass Flow Correction The current state-of-the-art appears to utilize quasi-steady models, and empirical correlations based on quasi-steady models, to relate the measured quantities to the derived fluid parameters. This quasi-steady model for the fluid structure interactions appears to work adequately for most Coriolis meters operating with most industrial process flows. The validity ofthe quasi-steady assumption will scale with the reduced frequencies ofthe vibration ofthe fluid within the pipe. Under a quasi-steady framework, the higher the reduced frequencies, the less accurate the Coriolis meters become. One relevant reduced frequency for the unsteady effects within a Corilois meter is the reduced frequency based on the vibrational frequency, tube diameter, and process fluid sound speed: mix Another relevant reduced frequency is the that based on the overall length ofthe corilois tubes:
J L ~~ amix It should be noted that, for any given meter design in which the geometry is fixed, the two reduced frequencies are not independent, and are scalar multiples of each other. For a given meter, variations in the reduced frequencies above are primarily determined by variations in process fluid sound speed. Physically, the reduced frequency represents the ratio between the time required for sound to propagate over a characteristic length to the time required for the tube to vibrate - 20 -
CC-0765 PCT EV 386515255 US O 2005/012881
one cycle. From a performance and accuracy perspective, reduced frequencies serve to capture the importance of unsteadiness in the aeroelastic interaction ofthe fluid and structure. In the limit of reduced frequencies approaching zero, the process can be modelled as quasi-steady. Most analytical models of Corilois flow meters use a quasi-steady model for the fluid /structure interaction. . However, for non-zero reduced frequencies, unsteady effects begin to influence the relationship between the measured structural response, i.e. the phase lag in the two legs ofthe meters and the natural frequency, and the sought fluid parameters, i.e. the mass flow ofthe fluid and fluid density. However, what is disclosed herein is to use a sound-speed based gas volume fraction parameter, a reduced frequency parameter relating to phase lag to mass flow rate. If the reduced frequency based on diameter is non-negligible, the inertial load from the fluid on the pipe develops a slight phase lags that increases with increasing frequency.
For non-negligible reduced frequencies based on the length ofthe flow tube, oscillations in the flow velocity can vary over the length ofthe pipe, potentially introducing error in the output ofthe meter. Typical variations in mixture sound speeds due to two phase flow result in significant variations in reduced frequencies. Thus, by dramatically reducing mixture speed of sound, the introduction of gas to a liquid mixture can dramatically increase the reduced frequency ofthe primary vibration associated with the Coriolis meter. If not accounted for in the interpretation, this increase in reduced frequency renders the quasi-steady model increasing inaccurate, and results in errors in mass flow and in density. This decrease in accuracy of Corilois meters with the introduction of bubbly fluids is well documented. In fact, others have attempted to correct for the effect of entrained air by correlating observed errors in mass flow to the gas volume fraction within the process fluid.
These authors proposed a correction based on GVF as follows:
2a R = 1-a Where the represents the gas volume fraction and R represents decrease in measured (apparent) mass flow normalized by the true mass flow. Thus, using this
- 21 - CC-0765 PCT EV 386515255 US correlation, a 1% increase in entrained air would result in a roughly 2%> underestimate ofthe actual mass flow. Although this formulation appears to capture the general trend observed experimentally, it has two drawbacks for use in the field. Firstly, the coriolis meter 16 has no direct way to measure the gas volume fraction. It has been suggested to use the measured apparent density ofthe fluid to estimate the level of entrained air, however, this is problematic since both ofthe two fundamental measurements, phase difference and natural frequency, are impacted by changes in the reduced frequency ofthe Coriolis vibration. Secondly, it is unlikely that the gas volume fraction is the only variable influencing the relationship between measured phase difference and mass flow and the measured natural frequency and density. Although gas volume fraction appears to correlate over at least some range of parameters, the physics ofthe problem suggest that sound speed, via a reduced frequency effect, may have also direct influence on the interpretation as developed above. What is proposed in this disclosure is to use a direct sound measurement from the process fluid to aid in the interpretation ofthe coriolis meter 16. In this interpretation, the reduced frequency parameters developed herein is included in interpreting the relation between the phase difference in the vibrating tubes and the mass flow as well as a direct role in interoreting the natural frequency ofthe oscillating flow tubes in terms of process fluid density. The sound speed measurement, combined with knowledge of process liquid and gas components as well as process temperature and pressure, enables a direct measurement of entrained air as well. Thus, the reduced frequency parameter and gas volume fraction can be used as inputs in the interpretation of phase lag in terms of mass flow. Due to the strong relationship between air content in liquids and mixture sound speed, the role ofthe reduced frequency parameter in the interpretation ofthe fundamental measurement ofthe Coriolis meter will have a more pronounce effect in bubbly flows. However, changes in sound speed and hence reduced frequency of operation in various types of liquids and other process mixtures have an effect on the interpretation and hence accuracy of Coriolis meter used in these applications as well. Consider, flow example, the performance of a Coriolis meter on two liquids - water and oil. Assume that the fluids - 22 - CC-0765 PCT EV 386515255 US have different densities and sound speeds. The different fluid properties suggest that the Coriolis meters will be operating at different reduced frequencies . The reduced frequency for the water will typically be ~10%-30% lower than that for the oil application. Recognizing that, while they are different, the reduced frequencies for both applications are still "small", the impact on accuracy may not be significant. However, some degree of inaccuracy is introduced by not accounting for the differences in the reduced frequency of operation ofthe Coriolis meter in this application. In this facility, water is pumped from the bottom of a large separator through a mag meter which measures the volumetric flow rate ofthe water. The water then flows through a SONARtrac entrained air meter to verify that the water has negligible entrained air. Air is then injected into the water forming a two phase mixture. The amount of entrained air is then measured with a second SONARtrac meter. The two phase mixture, of known water and air composition then passes through a 3 inch, bent tube Corilois meter. The outputs of all ofthe above mentioned metering devices where recorded along with water pressure and temperature. Using this information, the errors associated with the coriolis meter operating in the aerated liquids can be determined and plotted as a function of sound speed based parameters. In this example, Coriolis meter performance is characterized as a function of gas volume fraction. The errors were indeed significant. At 2% entrained air, the Coriolis meter is over reporting mass flow by 15% and under reporting mixture density by 2%. The actual density being reported by the meter, if inteφreted as the density ofthe liquid phase in the meter would be roughly 4%> in error. For this example, the mass flow error is parameterized by the sound speed -based gas volume fraction of entrained air. The parametric dependence of this is given by the equation shown on the plot.
Mass Factor = 0.0147gvfΛ3 - 0.0018gvfΛ2 + 0.004 lgvf + 1.0009
This correlation was then used to correct for the coriolis mass flow for the presence of entrained air. The amount of entrained air injected upstream ofthe Coriolis meter was varied in small increments such that the total entrained air levels ranged from 0 to 2%. The Coriolis meter registers and significant errors in mass flow (up to 15%) due to entrained air - 23 - CC-0765 PCT EV 386515255 US and the gas volume fraction based correlation employed successfully corrects the mass flow errors to within roughly 1% for the demonstration. A flow measuring system 82 embodying the present invention may be used monitor well heads. A basic configuration of a well metering system 84 is shown schematically in Fig. 9. This approach addresses most well head flow conditions and utilizes a two phase separator 86 (e.g., gas/liquid cylindrical cyclone (GLCC) separator) to separate the production stream of a gas/oil/water mixture 12 into a mostly gas stream 88 and a mostly liquid stream 89. While a GLCC is provide in the metering system 84, the present invention contemplates any device that separates the air and liquid components. The mostly gas stream 88 is fed to a sonar-based flow meter 89 similar as flow meter 90 which will be described in greater detail herein after. The flow meter measures the flow rate ofthe gas and determines the gas volume fraction ofthe gas fluid. The mostly liquid stream 89 is fed into a sonar-based flow meter 90, similar to the meters 18 and 100 of Figs. 1 and 2 respectively, which measures mixture sound speed and possibly convective velocity to determine the gas volume fraction and the volumetric flow rate, respectively, ofthe liquid gas mixture 89. The flow meter 90 is similar to that described in U.S. Patent Application No. 10/XXX,XXX (CiDRA No. CC-0749) filed June 24, 2004, U.S. Patent Application No. 10/766,440 (CiDRA No. CC-0714) and U.S. Patent Application No. 10/762,410 (CiDRA No. CC-0703), which are incorporated herein by reference. Following the flow meter 90, the flow 89 enters a coriolis meter 16. A processing unit 92 receives the output signals from the flow meter 90 and coriolis meter 16 to provide the measured outputs shown in Figs. 3 and 8. The two processing options for measuring the aerated liquid mass flow and density are presented in Fig. 7. The first method assumes that the performance ofthe coriolis for both mass flow and density can be augmented using the methods described in U.S. Patent Application No. 10/892,886 (CiDRA No. CC-0762) and U.S. Provisional Patent Application No. 60/539,640 (CiDRA No. CC-0704), which are incorporated herein by reference. The second approach, described in Fig. 11, assumes that only the density measurement ofthe coriolis meter is used for the mass flow and density ofthe aerated liquid. In this second approach, the volumetric flow rate determined by the flow meter 90 is combined with the corrected density to determine mass flow when aeration levels (e.g., gas - 24 - CC-0765 PCT EV 386515255 US O 2005/012881
volume fraction) exceed a threshold value. This approach takes advantage ofthe present inventions ability to detemiine a mass flow rate compensated for entrained gas and the coroilis ability to accurately mass flow rate for flows 12 having low levels of aeration. The second approach can be described as follows. To determine the density, the speed of sound (SOS) measurement provided by the flow meter 90 and the pressure (P) measurement provided by a pressure sensor 98 (or may be estimated) are used to calculate gas volume fraction and/ or reduced frequency parameter ofthe coriolis meter operating on the aerated fluid. Next the mixture density is determined by correcting the output ofthe Coriolis-based density meter for the effects of aeration (as described in similar to that described in U.S. Patent Application No. 10/892,886 (CiDRA No. CC-0762). Direct measurement ofthe mixture density along with knowledge ofthe gas volume fraction and the gas density enables determination of liquid phase density, as described hereinbefore. Mass flow is determined via one of two methods, depending on the gas volume fraction measurement ofthe flow meter 90. As shown in Fig. 11, if the gas volume fraction measurement is below a predetermined or input threshold level, the mass flow reported by the Coriolis is used. If it is above a threshold, the mass flow is calculated by first determining the total mixture volumetric flow rate by the flow meter 90 and then multiplying this value by corrected mixture density as described above. The combination of mixture sound speed and density enables a full description of the three phase fractions, i.e. the oil, water, and gas volumetric phase fraction, as described hereinbefore in accordance with present invention and shown in Fig. 10. The mostly gas stream 88 is feed in a sonar-based flow meter 99 similar to that described hereinbefore and in U.S. Patent Application No. 10/XXX,XXX (CiDRA No. CC- 0749) filed June 24, 2004, U.S. Patent Application No. 10/166,440 (CiDRA No. CC-0714) and U.S. Patent Application No. 10/762,410 (CiDRA No. CC-0703). The flow meter 99 measures sound speed and volumetric flow rate ofthe gas stream 88, and optionally an orifice plate may be used to measure the gas stream momentum. Combination of volumetric flow, sound speed and momentum measurements enables a good measurement of gas rate and liquid rate. The oil / water cut ofthe liquid phase ofthe mostly gas mixture can be assumed to be the same as the oil /water cut ofthe mostly liquid stream. The result is a compact, versatile, economical three phase metering system.
- 25 - CC-0765 PCT EV 386515255 US Tests were conducted on such a well metering system similar to that described in Fig. 9 to evaluate the performance ofthe flow meter 90 used in combination with the set-up shown in Fig. 9. Figs. 12 - 14 illustrated data recorded from the coriolis meter 16 and the flow meter 90 to determine various parameters ofthe process fluid (e.g., oil/water/gas mixture). Specifically, Fig. 12 shows the density correction ofthe coriolis meter 16. Fig. 13 shows the net oil and water cut ofthe process fluid. Fig. 14 shows a snapshot ofthe oil production being pumped from ground. As one will appreciate, the sonar-based entrained air meter 16 enables coriolis meters to maintain single phase accuracy in presence of entrained air. Fig. 15 illustrates a gas volume fraction meter 100 of Fig. 2, as described herein before. The GVF meter 100 includes a sensing device 116 disposed on the pipe 14 and a processing unit 124. The sensing device 116 comprises an array of strain-based sensors or pressure sensors 118-121 for measuring the unsteady pressures produced by acoustic waves propagating through the flowl2 to determine the speed of sound (SOS). The pressure signals Pι(t) - PN(t) are provided to the processing unit 124, which digitizes the pressure signals and computes the SOS and GVF parameters. A cable 113 electronically connects the sensing device 116 to the processing unit 124. The analog pressure sensor signals Pι(t) - P (t) are typically 4-20 mA current loop signals. The array of pressure sensors 118-121 comprises an array of at least two pressure sensors 118,119 spaced axially along the outer surface 122 ofthe pipe 14, having a process flow 112 propagating therein. The pressure sensors 118-121 may be clamped onto or generally removably mounted to the pipe by any releasable fastener, such as bolts, screws and clamps. Alternatively, the sensors may be permanently attached to, ported in or integral (e.g., embedded) with the pipe 14. The array of sensors ofthe sensing device 116 may include any number of pressure sensors 118-121 greater than two sensors, such as three, four, eight, sixteen or N number of sensors between two and twenty-four sensors. Generally, the accuracy ofthe measurement improves as the number of sensors in the array increases. The degree of accuracy provided by the greater number of sensors is offset by the increase in complexity and time for computing the desired output parameter ofthe flow. Therefore, the number of sensors used is dependent at least on the degree of accuracy desired and the desire update rate ofthe output parameter provided by the apparatus 100.
- 26 - CC-0765 PCT EV 386515255 US The pressure sensors 118-119 measure the unsteady pressures produced by acoustic waves propagating through the flow, which are indicative ofthe SOS propagating through the fluid flow 12 in the pipe. The output signals (Pι(t)- PNΦ) ofthe pressure sensors 118-121 are provided to a pre-amplifier unit 139 that amplifies the signals generated by the pressure sensors 118-121. The processing unit 124 processes the pressure measurement data Pι(t)- - PN( and determines the desired parameters and characteristics ofthe flow 12, as described hereinbefore. The apparatus 100 also contemplates providing one or more acoustic sources 127 to enable the measurement ofthe speed of sound propagating through the flow for instances of acoustically quiet flow. The acoustic source may be a device the taps or vibrates on the wall ofthe pipe, for example. The acoustic sources may be disposed at the input end of output end of the array of sensors 118-121, or at both ends as shown. One should appreciate that in most instances the acoustics sources are not necessary and the apparatus passively detects the acoustic ridge provided in the flow 12, as will be described in greater detail hereinafter. The passive noise includes noise generated by pumps, valves, motors, and the turbulent mixture itself. As suggested and further described in greater detail hereinafter, the apparatus 10 has the ability to measure the speed of sound (SOS) by measuring unsteady pressures created by acoustical disturbances propagating through the flow 12. Knowing or estimating the pressure and/or temperature of the flow and the speed of sound of the acoustic disturbances or waves, the processing unit 124 can determine gas volume fraction, such as that described in U.S. Patent Application No. 10/349,716 (CiDRA Docket No. CC-0579), filed January 23, 2003, U.S. Patent Application No. 10/376,427 (CiDRA Docket No. CC-0596), filed February 26, 2003, U.S. Patent Application No. 10/762,410 (CiDRA Docket No. CC-0703), filed January 21 , 2004, which are all incorporated by reference. Similar to the apparatus 100 of Fig. 15, an apparatus 200 of Fig. 16 embodying the present invention has an array of at least two pressure sensors 118,119, located at two locations xι,x2 axially along the pipe 14 for sensing respective stochastic signals propagating between the sensors 118, 119 within the pipe at their respective locations. Each sensor 118,119 provides a signal indicating an unsteady pressure at the location of each sensor, at each instant in a series of sampling instants. One will appreciate that the sensor
- 27 - CC-0765 PCT EV 386515255 US O 2005/012881
array may include more than two pressure sensors as depicted by pressure sensor 120,121 at location X3,XN- The pressure generated by the acoustic pressure disturbances may be measured through strained-based sensors and/or pressure sensors 118 - 121. The pressure sensors 118-121 provide analog pressure time-varying signals Pι(t),P2(t),P3(t),PN(t) to the signal processing unit 124. The processing unit 124 processes the pressure signals to first provide output signals 151,155 indicative ofthe speed of sound propagating through the flow 12, and subsequently, provide a GVF measurement in response to pressure disturbances generated by acoustic waves propagating through the flow 12. The processing unit 124 receives the pressure signals from the array of sensors 118- 121. A data acquisition unit 154 digitizes pressure signals Pι(t)-P (t) associated with the acoustic waves 14 propagating through the pipe 114. An FFT logic 156 calculates the Fourier transform ofthe digitized time-based input signals Pι(t) - PN( and provide complex frequency domain (or frequency based) signals Pι(ω),P2(ω),P3(ω),PN(ω) indicative ofthe frequency content ofthe input signals. A data accumulator 158 accumulates the additional signals Pι(t) - Pκ(t) from the sensors, and provides the data accumulated over a sampling interval to an array processor 160, which performs a spatial-temporal (two-dimensional) transform ofthe sensor data, from the xt domain to the k-ω domain, and then calculates the power in the k-ω plane, as represented by a k-ω plot, similar to that provided by the convective array processor 146. To calculate the power in the k-ω plane, as represented by a k-ω plot (see Fig. 17) of either the signals or the differenced signals, the array processor 160 determines the wavelength and so the (spatial) wavenumber k, and also the (temporal) frequency and so the angular frequency ω, of various ofthe spectral components ofthe stochastic parameter. There are numerous algorithms available in the public domain to perform the spatial/temporal decomposition of arrays of sensor units 118-121. In the case of suitable acoustic waves being present in both axial directions, the power in the k-ω plane shown in a k-ω plot of Fig. 17 so determined will exhibit a structure that is called an acoustic ridge 170,172 in both the left and right planes ofthe plot, wherein one ofthe acoustic ridges 170 is indicative ofthe speed of sound traveling in one axial direction and the other acoustic ridge 172 being indicative ofthe speed of sound traveling in the other axial direction. The acoustic ridges represent the concentration of a stochastic - 28 - CC-0765 PCT EV 386515255 US parameter that propagates through the flow and is a mathematical manifestation ofthe relationship between the spatial variations and temporal variations described above. Such a plot will indicate a tendency for k-ω pairs to appear more or less along a line 170,172 with some slope, the slope indicating the speed of sound. The power in the k-ω plane so determined is then provided to an acoustic ridge identifier 162, which uses one or another feature extraction method to determine the location and orientation (slope) of any acoustic ridge present in the left and right k-ω plane. The velocity may be determined by using the slope of one ofthe two acoustic ridges 170,172 or averaging the slopes ofthe acoustic ridges 170,172. Finally, information including the acoustic ridge orientation (slope) is used by an analyzer 164 to determine the flow parameters relating to measured speed of sound, such as the consistency or composition ofthe flow, the density ofthe flow, the average size of particles in the flow, the air/mass ratio ofthe flow, gas volume fraction ofthe flow, the speed of sound propagating through the flow, and/or the percentage of entrained air within the flow. An array processor 160 uses standard so-called beam forming, array processing, or adaptive array-processing algorithms, i.e. algorithms for processing the sensor signals using various delays and weighting to create suitable phase relationships between the signals provided by the different sensors, thereby creating phased antenna array functionality. In other words, the beam forming or array processing algorithms transform the time domain signals from the sensor array into their spatial and temporal frequency components, i.e. into a set of wave numbers given by k=2.r/λ where λ is the wavelength of a spectral component, and corresponding angular frequencies given by ω=2πv. One such technique of determining the speed of sound propagating through the flow 12 is using array processing techniques to define an acoustic ridge in the k-ω plane as shown in Fig. 17. The slope ofthe acoustic ridge is indicative ofthe speed of sound propagating through the flow 12. The speed of sound (SOS) is determined by applying sonar arraying processing techniques to determine the speed at which the one dimensional acoustic waves propagate past the axial array of unsteady pressure measurements distributed along the pipe 14.
- 29 -
CC-0765 PCT EV 386515255 US The apparatus 200 ofthe present invention measures the speed of sound (SOS) of one-dimensional sound waves propagating through the mixture to determine the gas volume fraction ofthe mixture. It is known that sound propagates through various mediums at various speeds in such fields as SONAR and RADAR fields. The speed of sound propagating through the pipe and flow 12 may be determined using a number of known techniques, such as those set forth in U.S. Patent Application Serial No. 09/344,094, filed June 25, 1999, now US 6,354,147; U.S. Patent Application Serial No. 10/795,111, filed March 4, 2004; U.S. Patent Application Serial No. 09/997,221, filed November 28, 2001, now US 6,587,798; U.S. Patent Application Serial No. 10/007,749, filed November 7, 2001, and U.S. Patent Application Serial No. 101162,410, filed January 21, 2004, each of which are incoφorated herein by reference. While the sonar-based flow meter using an array of sensors 118-121 to measure the speed of sound of an acoustic wave propagating through the mixture is shown and described, one will appreciate that any means for measuring the speed of sound ofthe acoustic wave may used to determine the entrained gas volume fraction ofthe mixture/fluid or other characteristics ofthe flow described hereinbefore. The analyzer 164 ofthe processing unit 124 provides output signals indicative of characteristics ofthe process flow 12 that are related to the measured speed of sound (SOS) propagating through the flow 12. For example, to determine the gas volume fraction (or phase fraction), the analyzer 164 assumes a nearly isothermal condition for the flow 12. As such the gas volume fraction or the void fraction is related to the speed of sound by the following quadratic equation: Ax2 + Bx + C = 0 wherein x is the speed of sound,
Figure imgf000032_0001
Keff/rl*ameasΛ2); Rg = gas density, rl = liquid density, K_ff = effective K (modulus ofthe liquid and pipewall), P= pressure, and ameas = measured speed of sound. Effectively, Gas Voulume Fraction (GVF) = (-B+sqrt(BΛ2-4*A*C))/(2*A) Alternatively, the sound speed of a mixture can be related to volumetric phase fraction (φi) ofthe components and the sound speed (a) and densities (p) ofthe component through the Wood equation. - 30 - CC-0765 PCT EV 386515255 US O 2005/012881
i
Figure imgf000033_0001
One dimensional compression waves propagating within a flow 12 contained within a pipe 14 exert an unsteady internal pressure loading on the pipe. The degree to which the pipe displaces as a result ofthe unsteady pressure loading influences the speed of propagation ofthe compression wave. The relationship among the infinite domain speed of sound and density of a mixture; the elastic modulus (E), thickness (t), and radius (R) of a vacuum-backed cylindrical conduit; and the effective propagation velocity (aej) for one dimensional compression is given by the following expression:
Figure imgf000033_0002
The mixing rule essentially states that the compressibility of a mixture (l/(p a2)) is the volumetrically- weighted average ofthe compressibilities ofthe components. For gas/liquid mixtures 12 at pressure and temperatures typical of paper and pulp industry, the compressibility of gas phase is orders of magnitudes greater than that ofthe liquid. Thus, the compressibility ofthe gas phase and the density ofthe liquid phase primarily determine mixture sound speed, and as such, it is necessary to have a good estimate of process pressure to inteφret mixture sound speed in terms of volumetric fraction of entrained gas. The effect of process pressure on the relationship between sound speed and entrained air volume fraction is shown in Fig. 18. Some or all ofthe functions within the processing unit 24 may be implemented in software (using a microprocessor or computer) and/or firmware, or may be implemented using analog and/or digital hardware, having sufficient memory, interfaces, and capacity to perform the functions described herein. While the embodiments ofthe present invention shown in Figs. 2, 20 and 21 shown the pressure sensors 118-121 disposed on the pipe 14, separate from the coriolis meter, the
- 31 - CC-0765 PCT EV 386515255 US O 2005/012881
present invention contemplates that the GVF meter 100 may be integrated with the coriolis meter to thereby provide a single apparatus. In this integrated embodiment, the pressure sensors 118-121 may be disposed on one or both ofthe tubes ofthe coriolis meter. As shown in Fig. 19, the flow meter 100 may process the array of pressure signals to determine the velocity and/or the volumetric flow of fluid flow 12. The flow meter 100 embodying the present invention has an array of at least two pressure sensors 118, 119, located at two locations xι,x2 axially along the pipe 14 for sensing respective stochastic signals propagating between the sensors 118,119 within the pipe at their respective locations. Each sensor 118, 119 provides a signal indicating an unsteady pressure at the location of each sensor, at each instant in a series of sampling instants. One will appreciate that the sensor array may include more than two pressure sensors as depicted by pressure sensor 120,121 at location X ,XN- The pressure generated by the convective pressure disturbances (e.g., eddies 88, see Fig. 20) may be measured through strained-based sensors and/or pressure sensors 118 - 121. The pressure sensors 118-121 provide analog pressure time-varying signals Pι(t),P2(t),P3(t),PN(t) to the signal processing unit 124. The processing unit 24 processes the pressure signals to first provide output signals indicative ofthe pressure disturbances that convect with the flow 12, and subsequently, provide output signals in response to pressure disturbances generated by convective waves propagating through the flow 12, such as velocity, Mach number and volumetric flow rate ofthe process flow 12. The processing unit 24 receives the pressure signals from the array of sensors 118- 121. A data acquisition unit 140 (e.g., A/D converter) converts the analog signals to respective digital signals. The FFT logic calculates the Fourier transform ofthe digitized time-based input signals Pι(t) - PN(0 and provides complex frequency domain (or frequency based) signals Pι(ω),P2(ω),P3(ω),P]Nj(ω) indicative ofthe frequency content ofthe input signals. Instead of FFT's, any other technique for obtaining the frequency domain characteristics ofthe signals Pι(t) - PN( , may be used. For example, the cross-spectral density and the power spectral density may be used to form a frequency domain transfer functions (or frequency response or ratios) discussed hereinafter. One technique of determining the convection velocity ofthe turbulent eddies 88 within the process flow 12 is by characterizing a convective ridge ofthe resulting unsteady - 32 -
CC-0765 PCT EV 386515255 US pressures using an array of sensors or other beam forming techniques, similar to that described in U.S Patent Application, Serial No. (Cidra's Docket No. CC-0122A) and U.S. Patent Application, Serial No. 09/729,994 (Cidra's Docket No. CC-0297), filed December 4, 200, now US6,609,069, which are incoφorated herein by reference. A data accumulator 144 accumulates the frequency signals Pι(ω) - PN(G>) over a sampling interval, and provides the data to an array processor 146, which performs a spatial-temporal (two-dimensional) transform ofthe sensor data, from the xt domain to the k-ω domain, and then calculates the power in the k-ω plane, as represented by a k-ω plot. The array processor 146 uses standard so-called beam forming, array processing, or adaptive array-processing algorithms, i.e. algorithms for processing the sensor signals using various delays and weighting to create suitable phase relationships between the signals provided by the different sensors, thereby creating phased antenna array functionality. In other words, the beam forming or array processing algorithms transform the time domain signals from the sensor array into their spatial and temporal frequency components, i.e. into a set of wave numbers given by k=27r/λ where λ is the wavelength of a spectral component, and corresponding angular frequencies given by ω=2πv. The prior art teaches many algorithms of use in spatially and temporally decomposing a signal from a phased array of sensors, and the present invention is not restricted to any particular algorithm. One particular adaptive array processing algorithm is the Capon method/algorithm. While the Capon method is described as one method, the present invention contemplates the use of other adaptive array processing algorithms, such as MUSIC algorithm. The present invention recognizes that such techniques can be used to determine flow rate, i.e. that the signals caused by a stochastic parameter convecting with a flow are time stationary and have a coherence length long enough that it is practical to locate sensor units apart from each other and yet still be within the coherence length. Convective characteristics or parameters have a dispersion relationship that can be approximated by the straight-line equation, k=ω/u,
- 33 - CC-0765 PCT EV 386515255 US where u is the convection velocity (flow velocity). A plot of k-ω pairs obtained from a spectral analysis of sensor samples associated with convective parameters portrayed so that the energy ofthe disturbance spectrally corresponding to pairings that might be described as a substantially straight ridge, a ridge that in tarbulent boundary layer theory is called a convective ridge. What is being sensed are not discrete events of turbulent eddies, but rather a continuum of possibly overlapping events forming a temporally stationary, essentially white process over the frequency range of interest. In other words, the convective eddies 88 is distributed over a range of length scales and hence temporal frequencies. To calculate the power in the k-ω plane, as represented by a k-ω plot (see Fig. 21) of either the signals, the array processor 146 determines the wavelength and so the (spatial) wavenumber k, and also the (temporal) frequency and so the angular frequency ω, of various ofthe spectral components ofthe stochastic parameter. There are numerous algorithms available in the public domain to perform the spatial/temporal decomposition of arrays of sensor units 118-121. The present invention may use temporal and spatial filtering to precondition the signals to effectively filter out the common mode characteristics P-ommonmode and other long wavelength (compared to the sensor spacing) characteristics in the pipe 14 by differencing adjacent sensors and retain a substantial portion ofthe stochastic parameter associated with the flow field and any other short wavelength (compared to the sensor spacing) low frequency stochastic parameters. In the case of suitable turbulent eddies 88 (see Fig. 20) being present, the power in the k-ω plane shown in a k-ω plot of Fig. 21 shows a convective ridge 200. The convective ridge represents the concentration of a stochastic parameter that convects with the flow and is a mathematical manifestation ofthe relationship between the spatial variations and temporal variations described above. Such a plot will indicate a tendency for k-ω pairs to appear more or less along a line 200 with some slope, the slope indicating the flow velocity. Once the power in the k-ω plane is determined, a convective ridge identifier 148 uses one or another feature extraction method to determine the location and orientation (slope) of any convective ridge 200 present in the k-ω plane. In one embodiment, a so- called slant stacking method is used, a method in which the accumulated frequency of k-ω - 34 - CC-0765 PCT EV 386515255 US pairs in the k-ω plot along different rays emanating from the origin are compared, each different ray being associated with a different trial convection velocity (in that the slope of a ray is assumed to be the flow velocity or correlated to the flow velocity in a known way). The convective ridge identifier 148 provides information about the different trial convection velocities, information referred to generally as convective ridge information. The analyzer 150 examines the convective ridge information including the convective ridge orientation (slope). Assuming the straight-line dispersion relation given by k=ω/u, the analyzer 150 determines the flow velocity, Mach number and/or volumetric flow. The volumetric flow is determined by multiplying the cross-sectional area ofthe inside ofthe pipe with the velocity ofthe process flow. For any embodiments described herein, the pressure sensors, including electrical strain gages, optical fibers and/or gratings among others as described herein, may be attached to the pipe by adhesive, glue, epoxy, tape or other suitable attachment means to ensure suitable contact between the sensor and the pipe. The sensors may alternatively be removable or permanently attached via known mechanical techniques such as mechanical fastener, spring loaded, clamped, clam shell arrangement, strapping or other equivalents. Alternatively, the strain gages, including optical fibers and/or gratings, may be embedded in a composite pipe. If desired, for certain applications, the gratings may be detached from (or strain or acoustically isolated from) the pipe if desired. It is also within the scope ofthe present invention that any other strain sensing technique may be used to measure the variations in strain in the pipe, such as highly sensitive piezoelectric, electronic or electric, strain gages attached to or embedded in the pipe. Accelerometers may be also used to measure the unsteady pressures. Also, other pressure sensors may be used, as described in a number ofthe aforementioned patents, which are incoφorated herein by reference. In another embodiment, the sensor may comprise of piezofilm or strips (e.g. PVDF) as described in at least one ofthe aforementioned patent applications. While the illustrations show four sensors mounted or integrated in a tube ofthe coriolis meter, the invention contemplates any number of sensors in the array as taught in at least one ofthe aforementioned patent applications. Also the invention contemplates that
- 35 - CC-0765 PCT EV 386515255 US the array of sensors may be mounted or integrated with a tabe of a coriolis meter having shape, such as pretzel shape, U-shaped (as shown), straight tube and any curved shape. The invention further contemplated providing an elongated, non- vibrating (or oscillating) portion that permits a greater number of sensors to be used in the array. While the present invention describes an array of sensors for measuring the speed of sound propagating through the flow for use in inteφreting the relationship between coriolis forces and the mass flow through a coriolis meter. Several other methods exists. For example, for a limited range of fluids, an ultrasonic device could be used to determine speed of sound ofthe fluid entering. It should be noted that the theory indicates that the inteφretation of coriolis meters will be improved for all fluids if the sound speed of the process fluid is measured and used in the inteφretation. Thus, knowing that the sound speed ofthe fluid is 5000 ft/sec as it would be for a water like substance, compared to 1500 ft/sec as it would be for say supercritical ethylene, would improve the performance of a coriolis based flow and density measurement. These measurements could be performed practically using existing ultrasonic meters. Another approach to determine speed of sound ofthe fluids is to measure the resonant frequency ofthe acoustic modes ofthe flow tabes. When installed in a flow line, the cross sectional area changes associated with the transition from the pipe into the typically much smaller flow tubes creates a significant change in acoustic impedance. As a result of this change in impedance, the flow tube act as somewhat of a resonant cavity. By tracking the resonant frequency of this cavity, one could determine the speed of sound of the fluid occupying the cavity. This could be performed with a single pressure sensitive device, mounted either on the coriolis meter, of on the piping network attached to the coriolis meter. In a more general aspect, the present invention contemplates the ablility to augmenting the performance of a coriolis meter using any method or means for measuring the gas volume fraction ofthe fluid flow. In one embodiment ofthe present invention as shown in Fig. 20, each ofthe pressure sensors 118-121 may include a piezoelectric film sensor to measure the unsteady pressures ofthe fluid flow 12 using either technique described hereinbefore.
- 36 -
CC-0765 PCT EV 386515255 US The piezoelectric film sensors include a piezoelectric material or film to generate an electrical signal proportional to the degree that the material is mechanically deformed or stressed. The piezoelectric sensing element is typically conformed to allow complete or nearly complete circumferential measurement of induced strain to provide a circumferential-averaged pressure signal. The sensors can be formed from PVDF films, copolymer films, or flexible PZT sensors, similar to that described in "Piezo Film Sensors Technical Manual" provided by Measurement Specialties, Inc., which is incoφorated herein by reference. A piezoelectric film sensor that may be used for the present invention is part number 1-1002405-0, LDT4-028K, manufactured by Measurement Specialties, Inc. Piezoelectric film ("piezofϊlm"), like piezoelectric material, is a dynamic material that develops an electrical charge proportional to a change in mechanical stress. Consequently, the piezoelectric material measures the strain induced within the pipe 14 due to unsteady pressure variations (e.g., acoustic waves) within the process mixture 12. Strain within the pipe is transduced to an output voltage or current by the attached piezoelectric sensor. The piezoelectrical material or film may be formed of a polymer, such as polarized fluoropolymer, polyvinyhdene fluoride (PVDF). The piezoelectric film sensors are similar to that described in U.S. Patent Application Serial No. 10/712,818 (CiDRA Docket No. CC- 0675), U.S. Patent Application Serial No. 10/712,833 (CiDRA Docket No. CC-0676), and U.S. Patent Application Serial No. 10/795,111 (CiDRA Docket No. CC-0732), which are incoφorated herein by reference. Another embodiment ofthe present invention include a pressure sensor such as pipe strain sensors, accelerometers, velocity sensors or displacement sensors, discussed hereinafter, that are mounted onto a strap to enable the pressure sensor to be clamped onto the pipe. The sensors may be removable or permanently attached via known mechanical techniques such as mechanical fastener, spring loaded, clamped, clam shell arrangement, strapping or other equivalents. These certain types of pressure sensors, it may be desirable for the pipe 12 to exhibit a certain amount of pipe compliance. Instead of single point pressure sensors 118- 121 , at the axial locations along the pipe 12, two or more pressure sensors may be used around the circumference ofthe pipe 12 at each ofthe axial locations. The signals from the pressure sensors around the circumference at a given axial location may be averaged to provide a cross-sectional (or circumference)
- 37 - CC-0765 PCT EV 386515255 US averaged unsteady acoustic pressure measurement. Other numbers of acoustic pressure sensors and annular spacing may be used. Averaging multiple annular pressure sensors reduces noises from disturbances and pipe vibrations and other sources of noise not related to the one-dimensional acoustic pressure waves in the pipe 12, thereby creating a spatial array of pressure sensors to help characterize the one-dimensional sound field within the pipe 12. The pressure sensors 118-121 of Fig. 20 described herein may be any type of pressure sensor, capable of measuring the unsteady (or ac or dynamic ) pressures within a pipe 14, such as piezoelectric, optical, capacitive, resistive (e.g., Wheatstone bridge), accelerometers (or geophones), velocity measuring devices, displacement measuring devices, etc. If optical pressure sensors are used, the sensors 118-121 may be Bragg grating based pressure sensors, such as that described in US Patent Application, Serial No. 08/925,598, entitled " High Sensitivity Fiber Optic Pressure Sensor For Use In Harsh Environments", filed Sept. 8, 1997, now U.S. Patent 6,016,702, and in US Patent Application, Serial No. 10/224,821, entitled " Non-Intrusive Fiber Optic Pressure Sensor for Measuring Unsteady Pressures within a Pipe", which are incoφorated herein by reference. In an embodiment ofthe present invention that utilizes fiber optics as the pressure sensors 14 they may be connected individually or may be multiplexed along one or more optical fibers using wavelength division multiplexing (WDM), time division multiplexing (TDM), or any other optical multiplexing techniques. In certain embodiments ofthe present invention, a piezo-electronic pressure transducer may be used as one or more ofthe pressure sensors 115-118 and it may measure the unsteady (or dynamic or ac) pressure variations inside the pipe or tabe 14 by measuring the pressure levels inside ofthe tube. These sensors may be ported within the pipe to make direct contact with the mixture 12. In an embodiment ofthe present invention, the sensors 14 comprise pressure sensors manufactured by PCB Piezotronics. In one pressure sensor there are integrated circuit piezoelectric voltage mode-type sensors that feature built-in microelectronic amplifiers, and convert the high-impedance charge into a low-impedance voltage output. Specifically, a Model 106B manufactured by PCB Piezotronics is used which is a high sensitivity, acceleration compensated integrated circuit piezoelectric quartz pressure sensor suitable for measuring low pressure acoustic phenomena in hydraulic and - 38 - CC-0765 PCT EV 386515255 US pneumatic systems. It has the unique capability to measure small pressure changes of less than 0.001 psi under high static conditions. The 106B has a 300 mV/psi sensitivity and a resolution of 91 dB (0.0001 psi). The pressure sensors incoφorate a built-in MOSFET microelectronic amplifier to convert the high-impedance charge output into a low-impedance voltage signal. The sensor is powered from a constant-current source and can operate over long coaxial or ribbon cable without signal degradation. The low-impedance voltage signal is not affected by triboelectric cable noise or insulation resistance-degrading contaminants. Power to operate integrated circuit piezoelectric sensors generally takes the form of a low-cost, 24 to 27 VDC, 2 to 20 mA constant-current supply. A data acquisition system ofthe present invention may incoφorate constant-current power for directly powering integrated circuit piezoelectric sensors. Most piezoelectric pressure sensors are constructed with either compression mode quartz crystals preloaded in a rigid housing, or unconstrained tourmaline crystals. These designs give the sensors microsecond response times and resonant frequencies in the hundreds of kHz, with minimal overshoot or ringing. Small diaphragm diameters ensure spatial resolution of narrow shock waves. The output characteristic of piezoelectric pressure sensor systems is that of an AC- coupled system, where repetitive signals decay until there is an equal area above and below the original base line. As magnitude levels ofthe monitored event fluctuate, the output remains stabilized around the base line with the positive and negative areas ofthe curve remaining equal. It is also within the scope ofthe present invention that any strain sensing technique may be used to measure the variations in strain in the pipe, such as highly sensitive piezoelectric, electronic or electric, strain gages and piezo-resistive strain gages attached to the pipe 12. Other strain gages include resistive foil type gages having a race track configuration similar to that disclosed U.S. Patent Application Serial No. 09/344,094, filed June 25, 1999, now US 6,354,147, which is incoφorated herein by reference. The invention also contemplates strain gages being disposed about a predetermined portion of the circumference of pipe 12. The axial placement of and separation distance ΔXi, ΔX2 between the strain sensors are determined as described herein above. - 39 -
CC-0765 PCT EV 386515255 US It is also within the scope ofthe present invention that any other strain sensing technique may be used to measure the variations in strain in the tabe, such as highly sensitive piezoelectric, electronic or electric, strain gages attached to or embedded in the tube 14. While a number of sensor have been described, one will appreciate that any sensor the measures the speed of sound propagating through the fluid may be used with the present invention, including ultrasonic sensors. The coriolis meter described herein before may be any known coriolis meter, such as two inch bent tabe coriolis meter manufactured my MicroMotion Inc. and a two in straight tabe coriolic meter manufactured by Endress & Hauser Inc. The coriolis meters comprise a pair of bent tabes (e.g. U-shaped, pretzel shaped) or straight tabes. While a particular density meter was described for an embodiment, the present invention contemplates any density meter may be used in the embodiments. Similarly, while a particular meter was provided to determine speed of sound propagating through the fluid flow 12, the present invention contemplates any SOS measuring device may be used. The dimensions and/or geometries for any ofthe embodiments described herein are merely for illustrative puφoses and, as such, any other dimensions and/or geometries may be used if desired, depending on the application, size, performance, manufacturing requirements, or other factors, in view ofthe teachings herein. It should be understood that, unless stated otherwise herein, any ofthe features, characteristics, alternatives or modifications described regarding a particular embodiment herein may also be applied, used, or incoφorated with any other embodiment described herein. Also, the drawings herein are not drawn to scale. Although the invention has been described and illustrated with respect to exemplary embodiments thereof, the foregoing and various other additions and omissions may be made therein and thereto without departing from the spirit and scope ofthe present invention.
- 40 - CC-0765 PCT EV 386515255 US

Claims

Claims What is claimed is:
1. A flow measuring system for determining the density of a fluid flowing in a pipe, the measuring system comprising: a density meter that provides a density signal indicative ofthe density ofthe fluid flowing in the pipe; a flow measuring device that measures the speed of sound propagating through the fluid, the measuring device providing an SOS signal indicative ofthe speed of sound propagating through the fluid and/or a GVF signal indicative ofthe gas volume fraction of the fluid; and a processing unit that determines the density ofthe non-gaseous component ofthe aerated fluid in response to the SOS signal and/or the GVF signal and the density signal.
2. The measuring system of claim 1, wherein the speed of sound measurement is used to determine a gas volumetric fraction (GVF) in the flow ofthe fluid.
3. The measuring system of claim 1, wherein the density meter includes one of a nuclear densitometer, a vibrating vane densitometer and a coriolisc meter.
4. The measuring system of claim 1, wherein the flow measuring device comprises an array of sensors disposed axially along the pipe for measuring acoustic pressures in the fluid.
5. The measuring system of claim 4, wherein the array of sensors includes at least one of strain based sensors, pressure sensors, ported pressure sensors and ultra-sonic sensors.
6. The measuring system of claim 1, wherein the processor provides a signal indicative ofthe volumetric phase fraction ofthe non-gaseous components ofthe fluid, wherein the non-gaseous components comprise two components. - 41 - CC-0765 PCT EV 386515255 US
7. The measuring device of claim 6, wherein the non-gaseous components ofthe fluid consist of liquid/liquid components or liquid/solid components ofthe fluid.
8. A well head metering system for measuring density of non-gaseous components of a three phase fluid flowing in a pipe, the metering system comprising: a density meter that provides a density signal indicative ofthe density ofthe fluid flowing in the pipe; a flow measuring device that measures the speed of sound propagating through the fluid, the measuring device providing an SOS signal indicative ofthe speed of sound propagating through the fluid and/or a GVF signal indicative ofthe gas volume fraction of the fluid; and a processing unit that determines the density ofthe non-gaseous component ofthe aerated fluid in response to the SOS signal and/or the GVF signal and the density signal.
9. The measuring system of claim 8, wherein the speed of sound measurement is used to determine a gas volumetric fraction (GVF) in the flow ofthe fluid.
10. The measuring system of claim 8, wherein the density meter includes one of a nuclear densitometer, a vibrating vane densitometer and a coriolisc meter.
11. The measuring system of claim 8, wherein the flow measuring device comprises an array of sensors disposed axially along the pipe for measuring acoustic pressures in the fluid.
12. The measuring system of claim 11, wherein the array of sensors includes at least one of strain based sensors, pressure sensors, ported pressure sensors and ultra-sonic sensors.
- 42 - CC-0765 PCT EV 386515255 US
13. The measuring system of claim 8, wherein the processor provides a signal indicative ofthe volumetric phase fraction ofthe non-gaseous components ofthe fluid, wherein the non-gaseous components comprise two components.
14. The measuring device of claim 13, wherein the non-gaseous components ofthe fluid consist of liquid/liquid components or liquid/solid components ofthe fluid.
15. The measuring device of claim 8, further comprising an air separating device the separates a substantial portion ofthe air from aerated fluid.
16. The measuring device of claim 15, wherein the air separating device is a gas/liquid cylindrical cyclone (GLCC).
- 43 - CC-0765 PCT EV 386515255 US
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Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN103323066A (en) * 2013-05-21 2013-09-25 中国石油大学(华东) Low-liquid-content gas-liquid two-phase flow measurement method and system
EP2878933A4 (en) * 2012-07-24 2016-06-15 Lanzhou Haimo Technologies Co Ltd Method for accurately measuring gas flow and liquid flow in gas and liquid mixed fluid
CN106461443A (en) * 2014-04-07 2017-02-22 高准公司 Improved vibrating flowmeter and related methods
CN109726440A (en) * 2018-12-04 2019-05-07 中国航空工业集团公司西安飞机设计研究所 A kind of aeroelastic analysis method considering internal flow dynamic characteristic
GB2572836A (en) * 2018-09-13 2019-10-16 M Flow Tech Ltd Void fraction calibration method
EP2572169B1 (en) * 2010-05-19 2020-06-03 Endress+Hauser Flowtec AG Method of measuring the flow rate of a medium within a pipe, and flowmeter
GB2581745A (en) * 2018-09-13 2020-08-26 M-Flow Tech Ltd Mass flow rate calculation method

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2009931A (en) * 1977-12-09 1979-06-20 Solartron Electronic Group Improvements relating to the measurement of fluid density
US5029482A (en) * 1989-02-03 1991-07-09 Chevron Research Company Gas/liquid flow measurement using coriolis-based flow meters
US5224372A (en) * 1990-05-14 1993-07-06 Atlantic Richfield Company Multi-phase fluid flow measurement
US6354147B1 (en) * 1998-06-26 2002-03-12 Cidra Corporation Fluid parameter measurement in pipes using acoustic pressures
US20030089161A1 (en) * 2001-11-07 2003-05-15 Gysling Daniel L. Fluid density measurement using acoustic pressures for industrial sensing applications

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2009931A (en) * 1977-12-09 1979-06-20 Solartron Electronic Group Improvements relating to the measurement of fluid density
US5029482A (en) * 1989-02-03 1991-07-09 Chevron Research Company Gas/liquid flow measurement using coriolis-based flow meters
US5224372A (en) * 1990-05-14 1993-07-06 Atlantic Richfield Company Multi-phase fluid flow measurement
US6354147B1 (en) * 1998-06-26 2002-03-12 Cidra Corporation Fluid parameter measurement in pipes using acoustic pressures
US20030089161A1 (en) * 2001-11-07 2003-05-15 Gysling Daniel L. Fluid density measurement using acoustic pressures for industrial sensing applications

Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2572169B1 (en) * 2010-05-19 2020-06-03 Endress+Hauser Flowtec AG Method of measuring the flow rate of a medium within a pipe, and flowmeter
EP2878933A4 (en) * 2012-07-24 2016-06-15 Lanzhou Haimo Technologies Co Ltd Method for accurately measuring gas flow and liquid flow in gas and liquid mixed fluid
CN103323066A (en) * 2013-05-21 2013-09-25 中国石油大学(华东) Low-liquid-content gas-liquid two-phase flow measurement method and system
CN103323066B (en) * 2013-05-21 2015-08-05 中国石油大学(华东) A kind of low liquid holdup gas-liquid two-phase flow measuring method and measuring system
CN106461443A (en) * 2014-04-07 2017-02-22 高准公司 Improved vibrating flowmeter and related methods
CN106461443B (en) * 2014-04-07 2020-08-21 高准公司 Improved vibratory flowmeter and related methods
GB2572836A (en) * 2018-09-13 2019-10-16 M Flow Tech Ltd Void fraction calibration method
GB2581745A (en) * 2018-09-13 2020-08-26 M-Flow Tech Ltd Mass flow rate calculation method
GB2572836B (en) * 2018-09-13 2020-09-02 M-Flow Tech Ltd Void fraction calibration method
GB2581745B (en) * 2018-09-13 2020-11-25 M Flow Tech Ltd Mass flow rate calculation method
CN109726440A (en) * 2018-12-04 2019-05-07 中国航空工业集团公司西安飞机设计研究所 A kind of aeroelastic analysis method considering internal flow dynamic characteristic

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