CN105783982A - Electrical resistance tomography-based gas-liquid two-phase flow measuring method and device - Google Patents

Abstract

The invention discloses an electrical resistance tomography-based gas-liquid two-phase flow measuring method and a device. Based on the method and the device, the phase content, the speed and the flow of each of the gas-phase flow and the liquid-phase flow can be recognized. Meanwhile, the overall average speed and the overall flow of the gas-phase flow and the liquid-phase flow can be recognized. The device comprises a measuring pipe (1), a spatially sensitive array (2), a sensitive electric field excitation unit (3), a data acquisition and processing system (4), an image reconstruction system (6), a control computer (5) and a differential pressure flowmeter (7).

Description

Gas-liquid two-phase flow measuring method and device based on Electrical Resistance Tomography

Technical field

The present invention relates to field of fluid measurement, specifically a kind of gas-liquid two-phase flow measuring method based on Electrical Resistance Tomography and device.The method and device may identify which each phase content of biphase gas and liquid flow, speed and flow and bulk flow velocity, flow.

Background technology

Engineering is widely present the flow phenomenon of two phase flow, wherein general with biphase gas and liquid flow.Such as in petroleum transportation pipeline, around hydroturbine rotor, the intracloud convection current of air etc., broadly fall into biphase gas and liquid flow flowing.Measured by two phase flow flow parameter, understand its characteristic and Changing Pattern, related scientific research, design and production tool are of great significance.Compared with single-phase flow, two phase flow owing to alternate there is mass transfer boundary is each, even chemical reaction, and in time, spatially variable at random, making the detection more complexity of such as each phase content, flow velocity, flow and the flow parameter such as overall rate, flow, difficulty is very big.Up to now, existing detection technique and method are built upon the detection means on single-phase sensor integration mostly, it is thus achieved that quantity of information little, and the overall permanence of two phase flow cannot be carried out real-time monitored description.Parameter and the form of expression that the measurement of biphase gas and liquid flow relates to are as follows:

1. flow

(1) mass flow of biphase gas and liquid flow:

G=G_g+G_l,

Wherein, G total mass flow rate；G_gAnd G_lRespectively gas phase and liquid phase quality flow.

(2) volume flow of biphase gas and liquid flow:

Q=Q_g+Q_l,

Wherein, Q total volumetric flow rate；Q_gAnd Q_lRespectively gas phase and liquid phase volume flow.

2. flow velocity

(1) gas-liquid divides phase velocity

$w_g=\frac{Q_g}{A_g};w_l=\frac{Q_l}{A_l},$

Wherein, w_gAnd w_lRespectively gas phase and liquid phase component velocity；A_gAnd A_lThe sectional area that respectively gas phase and liquid phase fluid pass through.

(2) gas-liquid divides phase superficial velocity

$w_{\mathrm{sg}}=\frac{Q_g}{A};w_{\mathrm{sl}}=\frac{Q_l}{A_l},$

w_sgAnd w_slRespectively gas phase and liquid phase superficial velocity；Actual internal area

A=A_g+A_l。

3. density

(1) flow density

${\mathrm{\ρ}}_f=\frac{G}{Q}.$

(2) real density

ρ=α ρ_g+(1-α)ρ_l,

Wherein, ρ_gAnd ρ_lRespectively gas phase and liquid phase fluid density；α is void fraction, also referred to as voidage.

4. void fraction

(1) void fraction (voidage)

$\mathrm{\α}=\frac{A_g}{A}.$

(2) filling-emptying model

$\mathrm{\β}=\frac{Q_g}{Q}.$

(3) mass gas content rate

$\mathrm{\χ}=\frac{{\mathrm{\β\ρ}}_g}{{\mathrm{\β\ρ}}_g+(1-\mathrm{\β}){\mathrm{\ρ}}_l}.$

Requirements at the higher level along with metering for two phase flow in commercial production, control aspect, it is necessary to exploitation one can measure each phase content, flow velocity and flow in acquisition biphase gas and liquid flow and the device of bulk flow velocity, flow simultaneously.

Electrical Resistance Tomography (ERT, ElectricalResistanceTomography) becomes the new method of gas-liquid two-phase flow measurement, has the advantages such as visualization, noncontact, radiationless, low cost.Specifically the application principle in gas-liquid two-phase flow measurement is: the periphery space sensitive electrod-array of container at pipeline, at a place plus exciting current, forms sensitive electric field.Owing to the conductivity of gas-liquid two-phase is different, when flowing, being continually changing of each phase content and distribution, cause the change of two-phase fluid compound electric conductance, the distribution making current field also changes therewith, causes a change for built-in potential distribution, thus the borderline measurement voltage of field domain also to change.The measurement data obtained from space sensitive electrod-array reflects the change information of electrical conductivity on whole pipeline section, and these data input computer also passes through certain image reconstruction algorithm, it is possible to rebuilds the distribution of conductivity in appearing on the scene, obtains the distribution of two phase contents.Continuous print measures point mutually each phase velocity and the flow that can also obtain aforementioned biphase gas and liquid flow, if being equipped with multiple other kinds of sensor, it is achieved measurement in a closed series, then can obtain the flow parameter of complete biphase gas and liquid flow.

The present invention provides a kind of gas-liquid two-phase flow measuring method based on Electrical Resistance Tomography and device, it is possible to identify each phase content of biphase gas and liquid flow, speed and flow and bulk flow velocity, flow.

Summary of the invention

The present invention provides a kind of gas-liquid two-phase flow measuring method based on Electrical Resistance Tomography and device.The method and device may identify which each phase content of biphase gas and liquid flow, speed and flow and bulk flow velocity, flow.Fig. 1 is based on the layout of the gas-liquid two-phase flow measuring apparatus of Electrical Resistance Tomography.Shown in figure, this device includes: measures pipeline (1), space sensitive array (2), sensitive electrical field excitation unit (3), data Collection & Processing System (4), image re-construction system (6), control computer (5), differential pressure flowmeter (7).Its annexation is:

Space sensitive array (2) is evenly distributed on the periphery of the measurement pipeline (1) of tested biphase gas and liquid flow flowing；

Sensitive electrical field excitation unit (3) connection space sensitization array (2)；

Space sensitive array (2) connects data Collection & Processing System (4)；

Data Collection & Processing System (4) connects image re-construction system (5)；

Differential pressure flowmeter (7) is positioned in measurement pipeline (1), in the downstream measuring pipeline (1)；

Control computer (5) connection space sensitization array (2), sensitive electrical field excitation unit (3), data acquisition and procession system

System (4), image re-construction system (6).

Fig. 2 is the schematic diagram that Electrical Resistance Tomography measures each phase content of biphase gas and liquid flow.Representing in figure, measuring pipeline (1) is tubulose, and its cross section is rounded, disposes along the even circumferential measuring pipeline wall (8) and is formed space sensitive array by multiple metal electrodes (9).In the process measured, sensitive electrical field excitation unit (3) applies exciting current to metal electrode (9), space sensitive array, under the excitation of alternating current, forms a space sensitive electric field that can scan whole circular cross-section from different observation angles.When measuring biphase gas and liquid flow flowing in pipeline, being continually changing of each phase content and distribution, namely bubble (10) and the size of liquid (11), position are continually changing, cause the change of two-phase fluid compound electric conductance, the distribution making current field also changes therewith, space sensitive field is produced modulating action by distribution and the change of internal conductance rate, makes space sensitive array export corresponding signal.Data Collection & Processing System (4) measures the voltage on other electrodes, it is input to image re-construction system (6), utilize image reconstruction algorithm, according to the distribution calculating sensitive electric field internal conductance rate, carry out data process, obtain the two dimension in two phase flow flow field or the time history of three-dimensional different distribution of conductivity and change, and then acquisition is measured the distribution of different electrical conductivity on certain cross section of pipeline and drawn each phase content in flow field.Show with the image (12) of reduction.

Accompanying drawing explanation

Fig. 1 is based on the layout of the gas-liquid two-phase flow measuring apparatus of Electrical Resistance Tomography；In figure, 1 measures pipeline, 2 space sensitive arrays, 3 sensitive electrical field excitation unit, 4 data Collection & Processing Systems, 5 control computer, 6 image re-construction systems, 7 differential pressure flowmeters.

Fig. 2 is the schematic diagram that Electrical Resistance Tomography measures each phase content of biphase gas and liquid flow；In figure, 3 sensitive electrical field excitation unit, 4 data Collection & Processing Systems, 5 control computers, 6 image re-construction systems, 8 measurement pipeline walls, 9 metal electrodes, 10 bubbles, 11 liquid, 12 images reduced.

Detailed description of the invention

With a specific embodiments further illustrate that the present invention proposes based on the gas-liquid two-phase flow measuring method of Electrical Resistance Tomography and the principle of device and structure.The method and device are for measuring each phase content of Air-C_2H_2 Flame, speed and flow and bulk flow velocity, flow.Parts composition in this device is identical with Fig. 1 with annexation.

In detailed description of the invention,

Measuring the cross section of pipeline (1) for circular, to be 1m, internal diameter for length be 50mm, wall thickness 10mm, material is lucite.Horizontal positioned.Circumferentially by 16 installing holes, aperture 3mm；

Space sensitive array (2) is made up of 16 Titanium electrodes, and electrode is cylindrical, diameter 3mm, is uniformly arranged in 16 installing holes measuring pipeline (1) along the circumferential direction.Titanium electrode does not penetrate through measurement pipeline wall thickness；

The mode of operation of sensitive electrical field excitation unit (3) is the excitation of adjacent sinusoidal current.Pair of electrodes in space sensitive array (2) is applied exciting current；

Voltage on data Collection & Processing System (4) measurement space sensitization array (2) other electrodes, is input to image re-construction system (6)；

Image re-construction system (6) utilizes image reconstruction algorithm, according to the distribution calculating sensitive electric field internal conductance rate, carry out data process, obtain the different distribution of conductivity on the two-dimensional section in Gas-water phases stream flow field, export the image Air-Water composition of the reduction distributed image on two-dimensional circular cross section simultaneously；

Control the operation that computer (5) connects, controls space sensitive array (2), sensitive electrical field excitation unit (3), data Collection & Processing System (4), image re-construction system (6), the continuous print sampling interval of specified data collection simultaneously and the system of process (4), thus obtaining point phase velocity of Air-Water；

The downstream of pipeline (1) measured by differential pressure flowmeter (7), measures total flow.

Claims (2)

1., based on the gas-liquid two-phase flow measuring method of Electrical Resistance Tomography and a device, this device includes

Measuring pipeline (1), space sensitive array (2), sensitive electrical field excitation unit (3), data Collection & Processing System (4), image re-construction system (6), control computer (5), differential pressure flowmeter (7), the annexation of above-mentioned parts is:

Space sensitive array (2) connects measures pipeline (1)；

Sensitive electrical field excitation unit (3) connection space sensitization array (2)；

Space sensitive array (2) connects data Collection & Processing System (4)；

Data Collection & Processing System (4) connects image re-construction system (5)；

Differential pressure flowmeter (7) is positioned in measurement pipeline (1), in the downstream measuring pipeline (1)；

Control computer (5) connection space sensitization array (2), sensitive electrical field excitation unit (3), data Collection & Processing System (4), image re-construction system (6).

2. a kind of gas-liquid two-phase flow measuring method based on Electrical Resistance Tomography according to claim l and device, it is characterized in that, described space sensitive array (2) is made up of multiple metal electrodes, is evenly distributed on the periphery of the measurement pipeline (1) of tested biphase gas and liquid flow flowing.