CN104897737B - Eight electrode rotary Electric field conductivity sensor gas holdup measurement methods - Google Patents
Eight electrode rotary Electric field conductivity sensor gas holdup measurement methods Download PDFInfo
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Abstract
The present invention relates to a kind of eight electrode rotary Electric field conductivity sensor gas holdup measurement methods, and used sensor includes four pairs of electrodes being evenly distributed on the same section of inner wall of the pipe, and each pair of electrode position is positioned opposite；Gas holdup measurement is carried out using following method：Apply the different sinusoidal signal of initial phase to four pairs of electrodes respectively to motivate, the phase difference between adjacent electrode is 45 °, so as to be synthetically produced the measurement electric field of rotation on section；When gas-liquid two-phase fluid flows through sensor, sensor output signal is acquired；Calculate rotating electric field conductivity sensor normalized conductance；Gas holdup is calculated using rotating electric field conductivity sensor normalized conductance.The present invention, which has, measures more accurate, the simple advantage of structure.
Description
Technical field
The invention belongs to fluid measurement technical fields, are related to a kind of conductivity sensor.
Background technique
Two-phase flow phenomenon is widely present in petroleum works, chemical engineering, metallurgical engineering, nuclear engineering, Aeronautical And Astronautical Engineering
Etc. in traditional industries and infant industry field.Biphase gas and liquid flow refers to the mixed flow system of gas phase Yu liquid phase Incompatible Substance.
Since there is the differences in the physical properties such as density, viscosity between composition each in biphase gas and liquid flow, in flow, pressure, gravity
And under the influence of the factors such as pipeline shape, cause biphase gas and liquid flow flow parameter measurement very difficult.Section gas holdup is
An important flow parameter in biphase gas and liquid flow industrial application system, its precise measurement is for production process metering, control
It is all of great significance with operational reliability.
Two phase flow gas holdup measuring technique mainly includes ultrasonic method, optical method, ray method, capacitance method, conductance method etc..Due to
Conductivity sensor has many advantages, such as clear principle, structure are simple, response is stablized, and has been widely used in the survey of multiphase flow parameter
In amount, early stage is researched and developed in sensor, plate electrode is mostly used to measure thickness of liquid film, in order to avoid the disturbance of sensor convection,
The annular electrode sensor of insertion vertical ascent pipeline inner wall comes into being, for example, annular conductivity sensor, to the cyclic annular electricity of wall type
Derivative sensor.And wall type ring-type conductivity sensor is received using one direction excitation, there is office in terms of field distribution directionality
It is sex-limited, it is influenced vulnerable to flow pattern.In order to solve this problem, M.Merilo et al. is in " Void fraction
measurementwith arotating electric field conductance gauge”(Journal
OfHeatTransfer, 1997, Vol 99, P330) propose rotating electric field formula conductometry, by the way that three-phase alternating current is distinguished
It is applied on the three pairs of electrodes arranged around tube wall to be synthetically produced wheel measuring electric field, eliminates flowing to a certain extent and be situated between
Matter is unevenly distributed caused measurement error.Nevertheless, first first three wheel measuring electric field that electrode is synthetically produced whether be
Optimum measurement mode fails to provide demonstration from theory analysis and experimental verification angle.
Summary of the invention
In view of the above-mentioned problems, the object of the present invention is to provide a kind of more accurate and simple possible the two phase flows of measurement to hold gas
Rate measurement method, technical scheme is as follows：
A kind of eight electrode rotary Electric field conductivity sensor gas holdup measurement methods, used sensor include uniformly dividing
Four pair electrodes of the cloth on the same section of inner wall of the pipe, each pair of electrode position are positioned opposite；If four pairs of electrodes are followed successively by A, B, C and
D, A and B are adjacent, and B is adjacent with C, and C is adjacent with D, and D is adjacent with A.Gas holdup measurement is carried out using following method：
(1) apply the different sinusoidal signal of initial phase to four pairs of electrodes respectively to motivate, the phase between adjacent electrode
Difference is 45 °, so as to be synthetically produced the measurement electric field of rotation on section；
(2) when gas-liquid two-phase fluid flows through sensor, sensor output signal is acquired；
(3) the normalized conductance rate G of fluid-mixing is definedeFor the conductivityσ of mixed phasemWith the conductivityσ of full waterwRatio
Value, the normalized conductance of eight electrode rotary Electric field conductivity sensors are defined as the mean value calculation of four pairs of electrode normalized conductances
Normalized conductance value calculates rotating electric field conductivity sensor normalized conductance
(4) rotating electric field conductivity sensor normalized conductance is utilizedCalculate gas holdup.
Preferably, conductivity sensor gas holdup measurement method, which is characterized in that Electrode opening angle θ is
22.5°.Electrode axial height H is 0.004m, and electrode radial thickness T is 0.001m.
Eight electrode rotaries Electric field conductivity sensor gas holdup measurement method proposed by the present invention, respectively on four pairs of electrodes
Apply 45 degree of phase phase difference of sinusoidal excitation signal to be synthetically produced rotating electric field, and pair cross-section measurement electric field has carried out sensitivity
Theoretical analysis and calculation, it is determined that eight electrode optimum geometry parameters, to reach optimal section gas holdup measurement effect.Have
Following advantages：
(1) rotating electric field formula conductivity sensor of the present invention has that structure type is simple, fast response time, stability
Height, the advantages that being easily installed measurement.
(2) gas holdup mensuration of the invention, the measurement of centering low flow velocity biphase gas and liquid flow gas holdup all can be used, Er Qieji
It calculates simply, accuracy is higher.
(3) gas holdup mensuration of the invention is applicable to vertical biphase gas and liquid flow bubble flow, slug flow and mixed shape and flows down
Gas holdup measurement.
Detailed description of the invention
Fig. 1 is rotating electric field formula conductivity sensor geometric parameter schematic diagram：(a) perspective view；(b) sectional view；(c) front view
Fig. 2 is rotating electric field formula conductivity sensor energisation mode schematic diagram.
Fig. 3 is rotating electric field formula conductivity sensor finite element fission structure chart.
Fig. 4 is three kinds of flow patterns four of biphase gas and liquid flow to electrode signal figure, and (a) (b) (c) is respectively bubble flow, slug flow, mixes
Shape stream.
Fig. 5 is the water phase flow and gas phase of air and liquid twophase flow experiment measurement data normalized conductance value and simulator calibration
Plate is tested between flow.
Fig. 6 biphase gas and liquid flow gas holdup measurement effect figure.
Specific embodiment
The present invention is described in detail below with reference to the accompanying drawings and embodiments.
The method have the characteristics that generating more uniform survey on pipeline section by the structural dimension optimization of sensor
Measure sensitivity field, the structure and dimensionally-optimised and measurement method of biphase gas and liquid flow rotating electric field formula conductivity sensor of the present invention include with
Lower step：
(1) eight electrode is to the ring-like conductivity sensor structure of wall as shown in Figure 1, being made of four pairs of stainless steel electrodes.Such as Fig. 2 institute
Show, the different sinusoidal signal of initial phase is applied to four pairs of electrodes respectively and is motivated, A is 0 °, and B is 45 °, and C is 90 °, and D is
135 °, the measurement electric field of rotation can be synthetically produced on section in this way.
(2) present invention optimizes sensor structure size using finite element method, is established using simulation software ANSYS
Rotating electric field formula conductivity sensor model, as shown in Figure 3.When modeling, set vertical ascent pipeline internal diameter D=0.02m, it is vertical on
Rise duct length L=0.2m, electrode radial thickness T, electrode axial height H, Electrode opening angle θ, water phase resistivity δw=1000
Ω m, electrode resistance rate δs=1.7241e-8 Ω m.Grid dividing is carried out using free partition patterns, is adopted when applying load
Use sinusoidal excitation.Emulation mode is：In ANSYS modeling, is measured on section in a model and be put into the small of a diameter 0.5mm
Ball, simulated bubble movement.When bead is in different location, the voltage of electrode is motivated also to follow variation, therefore excitation electricity can be passed through
The sensitivity of the voltage reflection conductivity sensor of pole variation.Bead one coordinate of every transformation, can be calculated the spirit in the coordinate
Sensitivity value.The coordinate of bead is traversed into all positions in vertical ascent pipeline section, obtains the sensitivity profile to electrode.
The present invention uses detecting field homogeneity error parameter (SVP) and sensor relative sensitivity (Savg) as optimization mesh
Mark.Sensor relative sensitivity (Savg) meaning refer to the average value of all position relative sensitivities in section, be defined as：
Definition measurement section homogeneity error parameter (SVP) be：
In formula, SdevFor the standard deviation of the relative sensitivity of different location on measurement section, it is defined as：
Obviously, SavgValue is bigger, indicates that transducer sensitivity is higher, SVP value is smaller, i.e., homogeneity error is smaller.
It is optimized using single factor test shift process.Only change one of factor, remaining is fixed, then carry out by
Step collocation experiment is compared, and the arranging scheme obtained, referred to as single factor alternate method are also isolated factor method.
Firstly, fixed Electrode opening angle θ and electrode radial thickness T, changes electrode axial height H, homogeneity error parameter
(SVP) and sensor relative sensitivity (Savg) as shown in the table.As can be seen that when electrode axial height H is 0.004m, spirit
The distribution character of sensitivity field is best.Therefore, electrode axial height H is fixed as 0.004m.
Then, fixed electrode axial height H and electrode radial thickness T, changes Electrode opening angle θ, homogeneity error parameter
(SVP) and sensor relative sensitivity (Savg) as shown in the table.It can be seen that when Electrode opening angle θ is 22.5 °, sensitivity field
Distribution character it is best.Therefore, Electrode opening angle θ is fixed as 22.5 °.
Finally, fixed Electrode opening angle θ and electrode axial height H, changes electrode radial thickness T, homogeneity error parameter
(SVP) and sensor relative sensitivity (Savg) as shown in the table.It can be seen that when electrode radial thickness T is 0.001m, it is sensitive
The distribution character for spending field is best.Therefore, electrode radial thickness T is fixed as 0.001m.
By optimizing to the sensor size, sensor optimized parameter, which can be obtained, is：Electrode opening angle θ is fixed as
22.5 °, electrode axial height H is fixed as 0.004m, and electrode radial thickness T is fixed as 0.001m.At this point, SavgFor
75.9804%, SVP 0.2172.
Sensitivity field also has been carried out to six electrode rotary Electric field conductivity sensors (structure that M.Merilo is proposed) simultaneously
Emulation, optimized parameter are that Electrode opening angle θ is fixed as 30 °, and electrode axial height H is fixed as 0.003m, and electrode radial thickness T is solid
It is set to 0.001m.Its SavgFor 66.1191%, SVP 0.2768.As can be seen that eight electrode rotary Electric field conductivity sensors without
By in terms of sensitivity intensity or uniformity will be better than six electrode structures, therefore, eight electrode structure of final choice.
(3) eight electrode rotary Electric field conductivity sensors of design are mounted on the vertical ascent oil-gas-liquid that caliber is 20mm
On phase flow tube road, when gas-liquid two-phase fluid flows through sensor, sensor output signal is acquired.The measurement of biphase gas and liquid flow gas holdup
Methods of experiments, process are：Experiment selects fluid media (medium) for originally water and air, selects industrial peristaltic pump and air pump point
Not carry out water phase and gas phase conveying, fixed gas phase flow velocity adjusts aqueous phase flow rate to obtain different operating condition proportions.Set water phase
With the flow of gas phase and be passed through in vertical ascent pipeline simultaneously, after the flow regime of two phase flow is stablized, conductivity sensor is believed
It number is acquired.
The method for obtaining measurement normalized conductance value is as follows：
Define the normalized conductance rate G of fluid-mixingeFor the conductivityσ of mixed phasemWith the conductivityσ of full waterwRatio,
Expression formula is：
Wherein, σmAnd σwConductivity when being the conductivity and pure water of fluid-mixing respectively, VmIt is each pair of electrode of sensor
Measure voltage, VwThe measurement voltage of sensor when being pure water.Rotating electric field conductivity sensor normalized conductance is defined as four pairs of electricity
The average value of pole normalized conductance, is defined as：
Wherein,It is the normalized conductance value of A phase, B phase, C phase, D phase electrode respectively.
(4) experimental verification and result：Fig. 4 gives the survey of three kinds of flow patterns (bubble flow, loads in mixture stream at slug flow) lower sensor
Signal is measured, it can be seen that, there are a little differences to electrode signal for synchronization four, this is by non-homogeneous point of flow media from signal
Caused by cloth.The measuring signal of four pairs of electrodes is averaged and seeks normalized conductance value, this is preferably solved to a certain extent
This problem, while also can preferably reflect the flow behavior of biphase gas and liquid flow.The normalization of biphase gas and liquid flow measurement result
Electric conductivity value is as shown in Figure 5 with experimental correlogram version between water phase flow and gas phase flow rate.As can be seen that normalized conductance value is to gas
Phase changes of contents has satisfied sensibility and resolution capability.
The gas holdup y under each operating condition is measured using fast valve in experimentg, biphase gas and liquid flow, which is obtained, using least square method holds
Gas rate measures statistical model：
Gas holdup measurement effect is as shown in fig. 6, counted to obtain the survey of rotating electric field conductivity sensor biphase gas and liquid flow gas holdup
Measuring result mean absolute error is 0.023.
Claims (3)
1. a kind of eight electrode rotary Electric field conductivity sensor gas holdup measurement methods, used sensor includes being uniformly distributed
Four pairs of electrodes on the same section of inner wall of the pipe, each pair of electrode position are positioned opposite；If four pairs of electrodes are followed successively by A, B, C and D,
A is adjacent with B, and B is adjacent with C, and C is adjacent with D, and D is adjacent with A, carries out gas holdup measurement using following method：
(1) apply the different sinusoidal signal of initial phase to four pairs of electrodes respectively to motivate, the phase difference between adjacent electrode is equal
It is 45 °, so as to be synthetically produced the measurement electric field of rotation on section；
(2) when gas-liquid two-phase fluid flows through sensor, four pairs of electricity of eight electrode rotary Electric field conductivity sensors are acquired respectively
The output signal of pole；
(3) the normalized conductance rate Ge for defining gas-liquid two-phase fluid is the conductivity of gas-liquid two-phase fluid and the conductivity of full water
Ratio, the normalized conductance rate of eight electrode rotary Electric field conductivity sensors are defined as the flat of the normalized conductance rate of four pairs of electrodes
Mean value；
(4) gas holdup is calculated using the normalized conductance rate of eight electrode rotary Electric field conductivity sensors.
2. conductivity sensor gas holdup measurement method according to claim 1, which is characterized in that Electrode opening angle θ is
22.5°。
3. conductivity sensor gas holdup measurement method according to claim 1, which is characterized in that electrode axial height H is
0.004m, electrode radial thickness T are 0.001m.
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| CN105756676A (en) * | 2015-11-19 | 2016-07-13 | 天津大学 | Method for measuring gas holdup of oil-gas-water three-phase flow by transmission-type ultrasonic sensor |
| CN105275450B (en) * | 2015-11-19 | 2018-03-06 | 天津大学 | Oil-gas-water three-phase flow flow parameter acoustoelectric sensor combination measurement method |
| CN108414579B (en) * | 2018-02-08 | 2020-06-09 | 天津大学 | Gas-liquid two-phase flow water holding rate measuring method capable of eliminating influence of water temperature and mineralization degree |
| CN109856047A (en) * | 2018-11-29 | 2019-06-07 | 天津大学 | A kind of single fiber sensor array biphase gas and liquid flow gas holdup imaging measurement method |
| CN111912880B (en) * | 2020-07-15 | 2022-04-15 | 中国核动力研究设计院 | Narrow rectangular channel full-field transient cavitation share measurement system and method |
| CN112083043B (en) * | 2020-09-10 | 2022-07-29 | 天津大学 | Combined measurement method for gas holdup of oil-gas-water three-phase flow conductivity sensor |
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