CN104101730B - Oil-gas two-phase flow liquid plug movement velocity based on capacitance detecting device and length measurement method - Google Patents
Oil-gas two-phase flow liquid plug movement velocity based on capacitance detecting device and length measurement method Download PDFInfo
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Abstract
Oil-gas two-phase flow liquid plug movement velocity based on capacitance detecting device and length measurement method, gather voltage signal including to the oil-gas two-phase flow in pipeline, according to differential technique voltage signal processing method, calculate each liquid voltage characteristic point beyond the Great Wall；Speed and the length of each liquid plug is calculated by Slug velocities and length computation formula.The present invention measures biphase gas and liquid flow Slug velocities and length by the capacitive differential method of cubing, there is the electrode sensitive to boundary, equipment is the simplest, the raw disturbance of not convection current movable property, do not affected by parameters such as dielectric conductance rate, temperature, it is made without demarcating, when liquid phase dielectric constant is relatively low, the corresponding voltage value of output capacitance difference can be made to be changed significantly by changing built-in chip type parameter.
Description
Technical field
The present invention relates to a kind of oil-gas two-phase flow Slug velocities and the capacitance detecting device of length and method, utilize two groups of cubings
Bi-concave capacitance electrode and the capacitive differential that both measure biphase flow liquid C1-esteraseremmer-N levied parameter measure, be mainly used in slug
The Slug velocities of flow pattern and measurement of length, belong to petroleum gas multiphase flow conveying technology field.
Background technology
Slug flow in biphase gas and liquid flow is a kind of common flow phenomenon, this flow pattern have intermittence, strong fluctuation and
Unstable feature, is one of the flowing safety-critical technical problem that must break through in deepwater oilfield exploitation, the cooling of nuclear power station cold water.
In marine oil and gas platform production system, the liquid plug parameter of liquid holdup, real-time such as movement velocity, slug length, frequency etc.
Detection data are significant for the safety running control of the equipment such as downstream separator.
Gas-liquid two-phase slug flow Slug velocities and length measurement method mainly there are optical method, ray method, electric method, high-speed camera
Method etc..First three methods needs two groups of identical measurement apparatus to slug flow Slug velocities with measurement of length, on pipeline not
Co-located slug flow liquid is filled in row measurement, the signal of two groups of measurement devices is carried out cross-correlation function computing obtain Slug velocities and
Length.Wherein, optical method and ray method certainty of measurement are the highest, but both apparatus expensive, operation is complicated, want operating environment
Ask high.High speed video process need liquid plug flow through transparent pipeline, by arranging scale on pipeline, in conjunction with the liquid being continuously taken
The position calculation Slug velocities of liquid plug on plug picture, slug length is calculated by the mark on pipe.This method is to operator
Requiring the highest, and there is the optical problem such as illumination, focusing, the scope of application is restricted.
The method of electric method measuring section plug flow Slug velocities and length is divided into conductance method and capacitance method from principle.Two kinds of methods have
Equipment is simple and convenient to operate, and is widely used in two phase flow phase content surveys quantifier elimination.At present, conductance is applied to gas
Liquid two-phase Slug velocities and measurement of length are more, but this method is only applicable to the measurement of conductor fluid, are not suitable for non-
The medium of conduction, as natural gas-crude oil flow is measured.The method of capacitance measurement Slug velocities and length is less, as China is special
Profit application text " based on electric capacity and micro-pipe gas-liquid two-phase flow rate measuring device of cross-correlation method " (publication date on July 7th, 2009,
Publication number CN201177634, February 4 2008 applying date) disclose one based on electric capacity and the cross-correlation method micro-pipe gas of measurement
The device of liquid two-phase speed, its measurement result is the most accurate.But the function device that this device needs is more, dispersion is placed
Time be easily subject to interference, and the caliber that can measure is less, and measurement electrode machining is more difficult.
In sum, all there is more restriction in the method measuring oil-gas two-phase flow Slug velocities and length, needs to study new side
Two phase flow Slug velocities and length are measured by method.
Summary of the invention
Provided herein is a kind of oil-gas two-phase flow liquid plug movement velocity based on capacitance detecting device and length measurement method and device, logical
The capacitive differential change crossing the gas-liquid interface accurately measuring liquid plug determines Slug velocities and length, improves pipe-line gas-liquid
The detection method of biphase flow liquid plug parameter.
Oil-gas two-phase flow liquid plug movement velocity based on capacitance detecting device and length measurement method, it is characterised in that described electric capacity
Detection device includes:
Two groups of bi-concave capacitance electrode arrangement, the signal source being connected with described bi-concave capacitance electrode arrangement by coaxial cable and electricity
Hold voltage converter ic, the analog input card being connected with signal source and computer with convert of capacitor to voltage integrated circuit；
Described signal source and convert of capacitor to voltage integrated circuit export according to the control program of computer and excite alternating current, and to collection
Voltage is measured in board output, and the measurement voltage that analog input card is collected by computer by data processing software processes, and counts
Calculate and measure volume phase content corresponding to voltage, carry out data storage and show the most in real time；
Described bi-concave capacitance electrode arrangement include the bi-concave capacitance electrode group for being arranged on isolated pipe outer wall, for
Bi-concave capacitance electrode group is fastened on the insulation filling material on isolated pipe outer wall, and is fastened on outside insulation filling material
Copper protection shell；Above-mentioned bi-concave capacitance electrode group includes two plate shapes identical arc copper sheet, and is close to insulation tube
Both sides, road are the most symmetrically placed；
Described measuring method comprises the following steps:
1) the two groups of bi-concave capacitance electrode arrangement being connected with signal source and capacitance-voltage conversion circuit are arranged on to be measured exhausted
On edge pipeline；The go-and-retum of two groups of bi-concave capacitance electrode arrangement is away from 10 times be set to not less than caliber；Through the liquid that statistics is minimum
Plug has the rule of 10 times of a length of caliber, finds again when the spacing of two groups of bi-concave capacitance electrode arrangement is not less than caliber
When 10 times, it is possible to best identifies three characteristic points；
2) by the CS2IN to MS3110 chip (10), CS1IN, CSCOM carry out the mode of parameter setting, make survey
The difference managing interior full oil ceiling voltage and the interior completely gas minimum voltage value of pipe measured is between 2V～4V；Owing to joining with this chip
The pressure scope of adopting closing the analog input card 5 used is+5V～-5V, controls difference and the curve of collection can be made between 2V～4V to be easy to
Waveform analysis identification；
3) after arranging parameter, by capacitance-voltage conversion circuit in the flow process of the oil-gas two-phase flow in isolated pipe
The capacitance signal produced is converted into voltage signal, is then acquired this voltage signal with analog input card, and the electricity that will collect
Pressure signal is acquired storage；
4) then read collection voltage, according to differential technique voltage signal processing method, calculate each liquid voltage characteristic point beyond the Great Wall；
Specifically: utilize formula
V=Vref*1.14*GAINSEL*(CS2IN-CS1IN)/CSCOM+Vref
Wherein, Vref=2.25V, arranges adjustment voltage for MS3110 chip, for fixed value；1.14 is the constant of this formula；
GAINSEL is amplification, unit V/V, chip self determine；CSCOM is the built-in integration of MS3110 chip
Electric capacity, unit pF；Above parameter is prefabricated parameter；CS2IN is that the bi-concave capacitance electrode arrangement near port of export position is surveyed
The electric capacity that the electric capacity measured, CS1IN arrive near the bi-concave capacitance electrode arrangement measurement of incoming-side location, unit pF；
Then two groups of bi-concave capacitance electrode arrangement are obtained at the output voltage corresponding to the capacitance of respective position measurement according to formula
Signal is V respectively1And V2；
This voltage signal V is versus time curve: V1=f1(t), V2=f2(t)；
Two curve magnitudes of voltage are poor V2-V1=f2(t)-f1(t)=f3T (), obtains difference curve V3=f3(t)；
Then difference curve V is analyzed3=f3(t), the curve that single liquid plug is corresponding have first have trough after have the class cosine curve of crest special
Levy, if the slope of any point is dV on curve3/ dT=k, the time is T, is liquid film district beyond isolated pipe (3) Nei Yesai district,
And the voltage in liquid film district is stable, by liquid film district magnitude of voltage Vconst, it is calculated three flex points (characteristic point):
When after T >=0.03S, (owing to working as V3≈Vconst, i.e. V3At VconstIt is transitive state time in the range of ± 0.1V, this state
Time without flex point, and this state duration is at least 0.03S), if exist first k < 0, defining this flex point is A point, i.e. liquid
Plug head is corresponding point when first group of bi-concave capacitance measuring device (1)；
After A point, for k > 0 time each section of curve, if the difference at the inclination angle corresponding to slope of each point is 2 in one section of curve
Within degree, then defining this section of curve is the curved section with same slope, then compares the size of the slope of each curved section, fixed
The starting point of the curved section that justice k value is maximum is B point, i.e. liquid plug head corresponding point when second group of capacitance measuring device (2)；
After pointb, there is slope and become the process of k=0 from k < 0, if V3At Vconst0.03S is stably continued in the range of ± 0.1V,
It is believed that slope k=0 of this curved section, is defined as C point, i.e. liquid plug afterbody through second group of electric capacity at the first of this curved section
Corresponding point during measurement apparatus (2)；
5) speed and the length of each liquid plug is calculated by following Slug velocities and length computation formula；Specific as follows:
Read the time that three flex points are the most corresponding, obtain T1, T2, T3；
Then formula V is utilizedS=L/ (TB-TA) calculate Slug velocities, wherein Vs is single Slug velocities, and L is two groups of bi-concave electricity
Hold electrode assembly center distance, TBIt is characterized a B correspondence time, TAIt is characterized an A correspondence time:
Obtain the speed Vs=L/ (T of this liquid plug2-T1)；
Recycling formula LS=VS×(TC-TA)-L calculates slug length, wherein Ls is single slug length, and Tc is characterized a C
The corresponding time:
Obtain slug length Ls=Vs × (T3-T1)-L
6) above-mentioned calculating is repeated for each liquid plug, thus obtain speed and the length of each liquid plug.
A kind of for oil-gas two-phase flow boundary real-time capacitive differential measurement system, it is characterised in that to include:
Two groups of bi-concave capacitance electrode arrangement, the signal source being connected with described bi-concave capacitance electrode arrangement by coaxial cable and electricity
Hold voltage converter ic, the analog input card being connected with signal source and computer with convert of capacitor to voltage integrated circuit；
Described signal source and convert of capacitor to voltage integrated circuit export according to the control program of computer and excite alternating current, and to collection
Voltage is measured in board output, and the measurement voltage that analog input card is collected by computer by data processing software processes, and counts
Calculate and measure volume phase content corresponding to voltage, carry out data storage and show the most in real time；
Described bi-concave capacitance electrode arrangement include the bi-concave capacitance electrode group for being arranged on isolated pipe outer wall, for
Bi-concave capacitance electrode group is fastened on the insulation filling material on isolated pipe outer wall, and is fastened on outside insulation filling material
Copper protection shell；Above-mentioned bi-concave capacitance electrode group includes two plate shapes identical arc copper sheet, and is close to insulation tube
Both sides, road are the most symmetrically placed.
Above-mentioned signal source includes with convert of capacitor to voltage integrated circuit: MS3110 chip, the most successively with MS3110 chip
On fourth, fifth, six pins connect INPUT CAP, wherein highest and lowest pin output 100kHz alternating current；
Also including the USB interface being connected with computer, this USB interface provides+5V running voltage for whole circuit board, and passes
The electronics write signal of defeated computer regulated chip parameter and the status feedback signal of chip；
Signal source and the core MS3110 chip of convert of capacitor to voltage integrated circuit, provide 100kHz by chip the 4th pin
Alternating current, carries out voltage conversion output by the 5th pin to measuring the capacitance obtained, by USB line by signal source and electric capacity
Voltage converter ic is connected with computer, by computer to built-in chip type parameter arrange, change output signal frequency and
Measuring output voltage, computer provides+5V running voltage for circuit board simultaneously.
The present invention is applicable to the non-conductive or biphase gas and liquid flow Slug velocities of weakly conducting liquid and slug length is measured, and its principle is:
The liquid plug of biphase gas and liquid flow has obvious intermittence, and utilization can measure bi-concave electric capacity electricity to biphase gas and liquid flow boundary
Pole device, measures the boundary of pipeline various location.When liquid plug is through out-of-date, the electricity measured due to two electrode assemblies
Pressure there are differences all the time, and there is obvious voltage jump at head and the afterbody of liquid plug, and the voltage of collection has obvious ripple
Dynamic feature.The voltage change corresponding when the two arrays of electrodes with liquid plug flow is there is on the voltage pulsation curve of two electrode measurement capacitive differential
Change characteristic point.Relation by the spacing between the time interval of associated voltage and electrode assembly, it is possible to obtain liquid plug speed and
Length.
The present invention measures biphase gas and liquid flow Slug velocities and length by the capacitive differential method of cubing, with other measuring method phases
Ratio has the following characteristics that the electrode sensitive to boundary, and equipment is inexpensively simple, and the raw disturbance of not convection current movable property, not by medium
The parameter such as electrical conductivity, temperature affects, it is not necessary to demarcate, and when liquid phase dielectric constant is relatively low, can join by changing built-in chip type
Number makes the corresponding voltage value of output capacitance difference be changed significantly.
Accompanying drawing explanation
Fig. 1 is the overall schematic of the measurement apparatus of the present invention.
Fig. 2 is capacitance electrode scheme of installation (containing cross-sectional end view and side sectional view).
Fig. 3 is signal source and the convert of capacitor to voltage integrated circuit of the measurement apparatus of the present invention.
Fig. 4 is that the present invention measures two phase flow Slug velocities and length calculation method block diagram.
Fig. 5 is the present invention theory analysis figure to two groups of capacitance electrode arrangement voltage difference curves,
Wherein, (a) slug length is more than the spacing of two electrode groups；B () slug length is approximately equal to the spacing of two electrode groups；(c)
Slug length is less than the spacing of two electrode groups.
Fig. 6 is superficial gas velocity 1.0m/s, under superficial liquid velocity 0.8m/s operating mode single liquid plug measure voltage difference curve and eigenvalue
Point.
Fig. 7 superficial gas velocity 4.0m/s, Slug velocities and the slug length measured under superficial liquid velocity 0.8m/s operating mode change over figure.
Fig. 8 is the slug length meansigma methods probability density distribution figure measured.
Wherein, 1,2 is bi-concave capacitance electrode arrangement, and 3 is isolated pipe, and 4 is signal source and the integrated electricity of convert of capacitor to voltage
Road, 5 is analog input card, and 6 is computer, and 7 is bi-concave capacitance electrode group, and 8 is insulation filling material, outside 9 protect for copper
Shell, 10 is MS3110 chip, and 11 is INPUT CAP, and 12 is USB interface.
Detailed description of the invention
Technical characterstic below in conjunction with the detailed description present invention:
See Fig. 1, two groups of capacitance electrode measurement apparatus be arranged on isolated pipe, with wire by capacitance electrode measurement apparatus with
Signal source is connected with convert of capacitor to voltage integrated circuit, carries out the fixing of electrode by insulant, metal screen layer.Insulation tube
Installing two groups of capacitance electrode measurement apparatus on pipeline outer wall, the go-and-retum of two groups of devices is away from being 10 times of caliber.Pass through data line
Signal source is connected with analog input card with convert of capacitor to voltage integrated circuit, gathers the capacitive differential voltage of the two arrays of electrodes measured.
Control software by the chip parameter on computer and signal source and convert of capacitor to voltage integrated circuit are carried out the setting of parameter.Pass through
Voltage signal acquisition that data acquisition software on computer measures also stores.Entered by the data processing software on computer
The process of row voltage signal, reads the capacitive differential voltage signal of corresponding liquid plug, according to the change calculations of capacitive differential voltage signal
Slug velocities and length.
See Fig. 4, read, by the data read procedure on computer, the capacitive differential voltage signal gathered and calculate Slug velocities
And length.The first step, reads the voltage signal gathered, and by the change curve of display voltage signal countershaft at any time.Second step,
Choose single measurement liquid capacitive differential voltage signal beyond the Great Wall to be analyzed.3rd step, marks the corresponding liquid on single liquid plug signal
Plug head through the change in voltage time point of two groups of capacitance electrode arrangement and liquid plug afterbody through the voltage of second capacitance electrode arrangement
Transformation period point.4th step, carries out the calculating of Slug velocities and length by theoretical formula.
Seeing Fig. 5, figure (a), (b), (c) are the change in voltage that often group electrode obtains after measuring a certain liquid plug, by two groups of electricity
Buckling carries out mathematic interpolation and obtains difference curve, and then studies theoretical difference voltage.When slug length immobilizes,
Changing the spacing between electrode group, the voltage signal often organizing measurement is level interval change along time shaft, and then can analyze electricity
The impact on capacitive differential signal of the pole group spacing, and find eigenvalue Changing Pattern in theory.Fig. 5 (a) is that slug length is more than electricity
Change in voltage during the group spacing of pole, in figure, B point voltage is close to minimum voltage, and after B point, voltage starts to raise.Fig. 5 (b)
Being slug length change in voltage when approximating electrode group spacing, B point voltage is of substantially equal with the voltage of A, C point.Fig. 5 (c)
Slug length is less than voltage levvl change before change in voltage during electrode group spacing, B point and roughly equal with A point voltage, B
Voltage rapid increase after Dian.
See Fig. 6, the curve in figure be superficial gas velocity be 1.00m/s, superficial liquid velocity be 0.80m/s operating mode under gather voltage
Change curve.In figure, the corresponding single liquid of A, B point liquid plug head beyond the Great Wall is through the moment of two groups of capacitance electrode arrangement of front and back, C
The corresponding liquid plug afterbody of point is through second capacitance electrode arrangement moment.It is 3.3m/s by the movement velocity being calculated this liquid plug,
A length of 21.2D, D are internal diameter of the pipeline.
Two capacitive differential that the present invention provides according to MS3110 chip measure function, obtain two groups of bi-concave capacitance electrode arrangement
The capacitive differential output voltage signal of respective position measurement on pipeline.For the flow fluid plug in biphase gas and liquid flow, between electrode
When fixing, there is the voltage characteristic not changed with Slug velocities in the capacitive differential signal of two groups of bi-concave capacitance electrode arrangement measurements
Point.Such characteristic point has three, and first characteristic point A correspondence liquid plug head flows through first group of capacitance electrode arrangement, TAIt is
The time of liquid plug flow warp；Second characteristic point B correspondence liquid plug correspondence liquid plug head flows through the time T of second group of capacitance electrode arrangementB,
The change in voltage trend on this aspect when electrode spacing is fixed, changes with the relativeness of electrode spacing with slug length and changes,
Its situation of change is divided into following three kinds of situations:
1) when slug length is more than electrode assembly spacing, B point voltage is close to the minima of measurement voltage, and after B point, voltage starts
Rise (Fig. 5 a)；
2) when slug length approximates electrode assembly spacing, there is the fluctuation of similar sinusoidal signal, B point in the voltage signal of collection
Voltage is roughly equal with A point voltage, and after B point, voltage rises (Fig. 5 b)；
3) when slug length is less than electrode assembly spacing, voltage levvl change before B point, and roughly equal with A point voltage, B point
Rear voltage rises (Fig. 5 c).
By known capacitance electrode group switching centre spacing L, the speed of corresponding liquid plug can be calculated.3rd characteristic point C is corresponding
Same liquid plug afterbody flows through second time T corresponding to capacitance electrode arrangementC, by the Slug velocities V tried to achieveS, it is multiplied by liquid plug
Flow through the time T of first electrodeAWith TCTime difference and deduct spacing L of electrode, it is possible to obtain length L of liquid plugS。
VS=L/ (TB-TA)
LS=VS×(TC-TA)-L
Embodiment
The application of the apparatus and method of oil-gas two-phase flow Slug velocities and linear measure longimetry is further illustrated in conjunction with example.By two groups of electric capacity
Electrode assembly is arranged on the lucite of internal diameter D=26mm and measures on pipeline, and the tip spacing l of two groups of capacitance electrode arrangement is 10
Times caliber i.e. l=260mm.For improving the degree of accuracy calculated, it is considered to often the width of group capacitance electrode group is 20mm, calculates in using
In the heart away from L=280mm.The wire of two groups of capacitance electrode arrangement is connected to signal source and convert of capacitor to voltage integrated circuit.Open
The chip parameter of computer controls software and data acquisition software, chip parameter control software is carried out chip MS3110 parameter and sets
Putting, now do not have biphase gas and liquid flow to flow in pipeline, the voltage of collection is straight line.When the magnitude of voltage collected is 2.25V ± 0.1V
Time, stop regulation and arrange.Use chip parameter to control software and preserve the parameter arranged.Regulation operating mode be superficial gas velocity be 1.00m/s,
Superficial liquid velocity is 0.80m/s, when occurring gas-liquid two-phase flow liquid plug in pipeline, starts data acquisition.Observe the data variation gathered,
If the difference of ceiling voltage and minimum voltage value is in 2V～4V, it is not necessary to be adjusted chip parameter, if difference does not exists
2V～4V, regulates chip parameter.Starting data acquisition, the magnitude of voltage after collection saves as TXT text.Compiled by Labview
The data read procedure write, demonstrates the voltage change curve Fig. 6 collected.Curve marks the A point corresponding time
T1The corresponding time T of=0.489s, B point2The corresponding time T of=0.573s, C point3=0.741s.According to Slug velocities computing formula
VS=L/ (TB-TA):
Vs=0.28/ (0.573-0.489)=3.3m/s
The speed obtaining this liquid plug is Vs=3.3m/s, according to slug length computing formula LS=VS×(TC-TA)-L:
Ls=3.3 × (0.741-0.489)-0.28=0.552m
Obtain a length of 0.552m of this liquid plug, be 21.2 times of bore.
Repeat above-mentioned implementation process, to superficial gas velocity 4.0m/s, the Slug velocities under superficial liquid velocity 0.8m/s operating mode and slug length
Continuous plus is added up, and can obtain Slug velocities and slug length under this operating mode and scheme over time, see Fig. 7.
Repeat above-mentioned implementation process, the Slug velocities under all operating modes and slug length Continuous plus are added up, obtain overall situation liquid plug
Length meansigma methods probability density distribution figure, Fig. 8.
Claims (1)
1. oil-gas two-phase flow liquid plug movement velocity based on capacitance detecting device and length measurement method, it is characterised in that described
Capacitance detecting device includes:
Two groups of bi-concave capacitance electrode arrangement (1,2), by coaxial cable with described bi-concave capacitance electrode arrangement (1,2) even
The signal source connect and convert of capacitor to voltage integrated circuit (4), be connected with convert of capacitor to voltage integrated circuit (4) with signal source
Analog input card (5) and computer (6)；
Described signal source and convert of capacitor to voltage integrated circuit (4) export to excite according to the control program of computer (6) and exchange
Electricity, and measure voltage to analog input card (5) output, analog input card (5) is collected by computer (6) by data processing software
Measurement voltage process, and calculate and measure volume phase content corresponding to voltage, carry out data storage over the display
Display in real time；
Described bi-concave capacitance electrode arrangement (1,2) includes the bi-concave electricity for being arranged on isolated pipe (3) outer wall
Hold electrode group (7), for bi-concave capacitance electrode group (7) is fastened on the insulation filling material on isolated pipe (3) outer wall
(8), and be fastened on insulation filling material (8) outside copper protection shell (9)；Above-mentioned bi-concave capacitance electrode group (7) is wrapped
Include two plate shapes identical arc copper sheet, and be close to isolated pipe (3) both sides symmetrically placed；
Described measuring method comprises the following steps:
1) the two groups of bi-concave capacitance electrode arrangement (1,2) being connected with capacitance-voltage conversion circuit (4) with signal source are installed
On isolated pipe (3) to be measured；The go-and-retum of two groups of bi-concave capacitance electrode arrangement (1,2) is away from being set to not less than pipe
10 times of footpath；
2) by the CS2IN to MS3110 chip (10), CS1IN, CSCOM carry out the mode of parameter setting, make measurement obtain
Pipe in full oil ceiling voltage and pipe the difference of full gas minimum voltage value be between 2V～4V；Owing to coordinating with this chip
The pressure scope of adopting of the analog input card (5) used is+5V～-5V, controls difference and can make the curve of collection just between 2V～4V
In waveform analysis identification；
3) after arranging parameter, by signal source with capacitance-voltage conversion circuit (4) to the oil gas two in isolated pipe (3)
The capacitance signal produced in the flow process flowed mutually is converted into voltage signal, then carries out this voltage signal with analog input card (5)
Gather, and the voltage signal collected is acquired storage；
4) then read collection voltage, according to differential technique voltage signal processing method, calculate each liquid voltage characteristic beyond the Great Wall
Point；Specifically: utilize formula
V=Vref*1.14*GAINSEL*(CS2IN-CS1IN)/CSCOM+Vref
Wherein, Vref=2.25V, arranges adjustment voltage for MS3110 chip (10), for fixed value；1.14 is the normal of this formula
Number；GAINSEL is amplification, unit V/V, chip self determine；CSCOM is the built-in long-pending of MS3110 chip (10)
Divide electric capacity, unit pF；Above parameter is prefabricated parameter；CS2IN is the bi-concave capacitance electrode arrangement near port of export position
(2) electric capacity, the CS1IN that measure measure the electric capacity arrived, unit near the bi-concave capacitance electrode arrangement (1) of incoming-side location
pF；
Then two groups of bi-concave capacitance electrode arrangement (1,2) are obtained corresponding to the capacitance of respective position measurement according to formula
Output voltage signal be V respectively1And V2；
This voltage signal V is versus time curve: V1=f1(t), V2=f2(t)；
Two curve magnitudes of voltage are poor V2-V1=f2(t)-f1(t)=f3T (), obtains difference curve V3=f3(t)；
Then difference curve V is analyzed3=f3(t), the curve that single liquid plug is corresponding have first have trough after have the class cosine of crest
Curvilinear characteristic, if the slope of any point is dV on curve3/ dT=k, the time is T, beyond isolated pipe (3) Nei Yesai district is
Liquid film district, and the voltage in liquid film district is stable, by liquid film district magnitude of voltage Vconst, it is calculated three flex points:
When, after T>=0.03S, if there is first k<0, defining this flex point is that A point, i.e. liquid plug head are through first group of concave-concave
Corresponding point during face capacitance measuring device (1)；
After A point, for k > 0 time each section of curve, if the difference at the inclination angle corresponding to slope of each point is 2 in one section of curve
Within degree, then defining this section of curve is the curved section with same slope, then compares the size of the slope of each curved section, fixed
The starting point of the curved section that justice k value is maximum is B point, i.e. liquid plug head corresponding point when second group of capacitance measuring device (2)；
After pointb, there is slope and become the process of k=0 from k < 0, if V3At VconstStablize in the range of ± 0.1V and continue
0.03S, then it is assumed that slope k=0 of this curved section, is defined as C point, i.e. liquid plug afterbody through by the first of this curved section
Corresponding point during two groups of capacitance measuring device (2)；
5) speed and the length of each liquid plug is calculated by following Slug velocities and length computation formula；Specific as follows:
Read the time that three flex points are the most corresponding, obtain T1, T2, T3；
Then formula V is utilizedS=L/ (TB-TA) calculate Slug velocities, wherein Vs is single Slug velocities, and L is two groups of bi-concaves
Capacitance electrode arrangement center distance, TBIt is characterized a B correspondence time, TAIt is characterized an A correspondence time:
Obtain the speed Vs=L/ (T of this liquid plug2-T1)；
Recycling formula LS=VS×(TC-TA)-L calculates slug length, wherein Ls is single slug length, and Tc is characterized a little
The C correspondence time:
Obtain slug length Ls=Vs × (T3-T1)-L
6) above-mentioned calculating is repeated for each liquid plug, thus obtain speed and the length of each liquid plug.
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