CN100587492C - Apparatus and method for measuring microtubule gas-liquid diphasic flow rate based on capacitance and correlational method - Google Patents

Abstract

The invention discloses a device for measuring gas phase and liquid phase flow velocity in miniature tube based on capacitor and cross correlation method and a method thereof. The device comprises aninsulating mini-measuring tube, two capacitive sensors, a capacitance-voltage switching circuit, a data acquisition circuit and a computer. The method comprises obtaining two sets of capacitance signals reflecting gas-liquid two phase flow distribution information by the two capacitive sensors, performing capacitance-voltage switching, transmitting to the computer via the data acquisition circuit,calculating the cross correlation function of two sets of capacitance measurement signals with the principle of cross-correlation velocity measurement, determining the transition time of the signalsaccording to the peak position of the cross correlation function, and further obtaining the flow velocity information of the gas phase and liquid phase in the miniature tube. The invention provides aneffective way to solve the problem of flow velocity measurement of non-conducting gas phase and liquid phase in the miniature tube, and the device has the advantages of simple structure, low cost with no influence on the flowing of gas phase and liquid phase in the tube by non-invasion manner. The invention is suitable for continuous online flow velocity measurement of non-conducting gas phase and liquid phase in the millimeter-scale miniature tube.

Description

Microtubule gas-liquid two-phase flow rate measuring device and method based on electric capacity and cross-correlation method

Technical field

The present invention relates to field of measuring techniques, relate in particular to a kind of microtubule gas-liquid two-phase flow rate measuring device and method based on electric capacity and cross-correlation method.

Background technology

Two-phase flow extensively is present among the fields such as petro chemical industry, and biphase gas and liquid flow is as a kind of typical diphasic flow phenomenon, and is very general in the middle of production reality.Biphase gas and liquid flow is furtherd investigate parameters such as usually needing to measure its flow velocity, voidage.Because the complicacy of diphasic flow system, the continuous on-line detection of these parameters is often very difficult.

Two-phase flow phenomenon in the microsystem is a current research focus, receive increasing the concern and attention, for example the micro-tube reactor has obtained the extensive studies application in many industrial circles, and the detection of diphasic stream parameter also becomes a new direction in polyphasic flow parameter detecting field in the micro-tube.Flow velocity carries out continuous on-line detection to it and has very important and practical meanings as the important parameter of two-phase flow phenomenon.At present, the detection to two-phase flow velocity in the micro-tube mainly contains two kinds of methods: high speed image Photographic technique and optical method.These methods still are in the laboratory study stage, though certain feasibility is arranged, still not mature enough perfect, be difficult in the actual industrial environment, be applied.Under the industrial condition in the micro-tube detection of two-phase flow velocity also lack efficient ways at present, need further research.

Capacitance method is with a long history, has characteristics simple in structure, with low cost, is convenient to commercial Application.Capacitance method mainly obtains the voidage information of non-conductive medium, successfully utilization under conventional yardstick, but, rarely have bibliographical information in the micro-tube of millimeter level micro-tube environment, especially caliber below 5mm.Capacitance method combines with the simple crosscorrelation measuring principle and can realize non-intrusion type on-line measurement to gas-liquid two-phase fluid speed, does not see use at present in micro-tube gas-liquid two-phase flow velocity is measured.

The present invention is directed to the current situation that the gas-liquid two-phase flow velocity detects in the current micro-tube, proposition is based on the measurement scheme of capacitance method and simple crosscorrelation measuring principle, design a covering device, comprise capacitive transducer, capacitance voltage change-over circuit, data acquisition circuit and computing machine, can realize continuous on-line measurement non-conductive biphase gas and liquid flow rate of flow of fluid in the millimeter level micro-tube.

Summary of the invention

The purpose of this invention is to provide a kind of stable, reliable microtubule gas-liquid two-phase flow rate measuring device and method based on electric capacity and cross-correlation method.

Microtubule gas-liquid two-phase flow rate measuring device based on electric capacity and cross-correlation method comprises that caliber is the miniature measuring channel of millimetre-sized insulation, two capacitive transducers that structure is identical are installed in the periphery of pipeline, capacitive transducer is connected with the capacitance voltage change-over circuit, two capacitive transducers respectively with the first capacitance voltage change-over circuit, the second capacitance voltage change-over circuit is connected, change-over circuit is connected with computing machine by data acquisition circuit, capacitive transducer is made of the metal electrode of two symmetries, be respectively excitation end and test side, two electrodes are symmetry and be close to the outer wall installation of the miniature measuring channel that insulate mutually, electrode is connected with lead, and the whole measuring channel outside evenly surrounds metal screen layer.

The described first capacitance voltage change-over circuit is identical with the second capacitance voltage converting circuit structure, connected mode is an end of first electronic switch, one end and second switch one end process capacitive transducer and the 3rd electronic switch, one end of the 3rd electric capacity, the first operational amplifier reverse input end is connected, second switch other end ground connection, the capacitive transducer two ends respectively with first electric capacity, one end, second electric capacity, one end is connected, the first electric capacity other end and the second electric capacity other end ground connection, first operational amplifier output terminal and first resistance, one end, the 3rd electric capacity other end, the 3rd switch other end is connected, the first resistance other end and second resistance, one end, the second operational amplifier reverse input end is connected, the first operational amplifier positive input and the second operational amplifier positive input ground connection, second operational amplifier output terminal and the second resistance other end, the first sampling holder input end, the second sampling holder input end is connected, the first sampling holder output terminal and the 4th electric capacity one end, the differential amplifier reverse input end is connected, the second sampling holder output terminal and the 5th electric capacity one end, the differential amplifier positive input is connected, the differential amplifier output terminal is connected with quadrielectron switch one end, the 4th electric capacity and the equal ground connection of the 5th electric capacity other end.

Described data acquisition circuit is: digital signal processor respectively with A/D converter, programmable gain amplifier, instrument amplifier, D/A converter, CPLD, the USB communication module is connected, D/A converter successively with instrument amplifier, programmable gain amplifier, A/D converter is connected, CPLD respectively with D/A converter, instrument amplifier, programmable gain amplifier, A/D converter is connected, CPLD respectively with D/A converter, instrument amplifier, programmable gain amplifier, A/D converter is connected.

Microtubule gas-liquid two-phase flow velocity measuring method based on electric capacity and cross-correlation method comprises the steps:

1) two identical capacitive transducers of structure are installed on the miniature measuring channel outer wall of insulation, this sensor produces the independent capacitance signal of two groups of reflection gas-liquid two-phase flow containing rates distributed intelligence, record by the first capacitance voltage change-over circuit and the second capacitance voltage change-over circuit, and send into computing machine by data acquisition circuit;

2) earlier two groups of capacitance signals are carried out normalization and handle, the signal E after handling with going average _X1, E _X2Carry out cross correlation process, the formula of cross correlation process is as follows:

$R_{E_{x1}{E}_{x2}}\left(j\right)=\frac{1}{N}\underset{n=1}{\overset{N}{\mathrm{\Σ}}}{E}_{x1}\left(n\right)E_{x2}(n+j),j=\mathrm{1,2,3}......,J$

Wherein:

N---be used for the number of the sampled point of cross-correlation calculation

3) according to by step 2) the cross correlation process result's that obtains peak of function position establishes the transit time τ of signal, and formula is as follows:

τ＝KΔt，

Wherein:

K---the signal lag of cross correlation function peak value correspondence is counted

Δ t---sampling interval

4) according to the transit time τ of signal and the center distance L of two capacitive transducers, determine the speed v of gas-liquid two-phase fluid in the micro-tube, formula is as follows:

$v=\frac{L}{\mathrm{\τ}}.$

Described to two groups of capacitance signals carry out normalization with go the average disposal route to comprise the steps:

1) two groups of capacitance signals are carried out normalized, the formula of normalized is as follows:

$C_{x1}^{\′}=\frac{C_{x1}-C_{01}}{C_{m1}-C_{01}}---\left(1\right)$

$C_{x2}^{\′}=\frac{C_{x2}-C_{02}}{C_{m2}-C_{02}}---\left(2\right)$

Wherein:

C ₀₁---first group of capacitance signal when all being gas in the measuring channel,

C ₀₂---second group of capacitance signal when all being gas in the measuring channel,

C _M1---first group of capacitance signal when all being liquid in the measuring channel,

C _M2---second group of capacitance signal when all being liquid in the measuring channel,

C ' _X1---first group of normalized result of capacitance signal,

C ' _X2---second group of normalized result of capacitance signal,

2) the signal C ' to obtaining by step 1) _X1, signal C ' _X2Go average to handle, the formula that goes average to handle is as follows:

E _x1＝C′ _x1-C′ _x1(3)

E _x2＝C′ _x2-C′ _x2(4)

Wherein:

C ' _X1---the average of signal after first group of normalization,

C ' _X2---the average of signal after second group of normalization,

E _X1---first group of signal after the past average is handled,

E _X2---second group of signal after the past average is handled.

The present invention can be used for non-conductive gas-liquid two-phase flow velocity in the millimeter level micro-tube is carried out on-line measurement, that corresponding device thereof has is simple in structure, non-intruding flows to gas-liquid two-phase in the pipeline does not have influence, low cost and other advantages, is applicable to the continuous on-line measurement of non-conductive gas-liquid two-phase flow velocity in the micro-tube.

Description of drawings

Fig. 1 is based on the structural representation of the microtubule gas-liquid two-phase flow rate measuring device of electric capacity and cross-correlation method;

Fig. 2 is the sectional view of capacitive transducer of the present invention along the pipeline direction;

Fig. 3 is the sectional view of capacitive transducer of the present invention along the tube section direction;

Fig. 4 is a data acquisition circuit block scheme of the present invention;

Fig. 5 is capacitance voltage change-over circuit figure of the present invention.

Embodiment

As shown in Figure 1, microtubule gas-liquid two-phase flow rate measuring device based on electric capacity and cross-correlation method comprises that caliber is the miniature measuring channel of millimetre-sized insulation, two capacitive transducers that structure is identical are installed in the periphery of pipeline, two capacitive transducers respectively with the first capacitance voltage change-over circuit, the second capacitance voltage change-over circuit is connected, the capacitance voltage change-over circuit is connected with computing machine by data acquisition circuit, capacitive transducer is made of the metal electrode of two symmetries, be respectively excitation end 1 and test side 2, two electrodes are symmetry and be close to outer wall 3 installations of the miniature measuring channel that insulate mutually, electrode is connected with lead 4, and the whole measuring channel outside evenly surrounds metal screen layer 5.

Two capacitive transducers obtain the capacitance signal of two groups of reflection gas-liquid two-phase flow containing rates distributed intelligence, are sent in the computing machine by data acquisition circuit after capacitance voltage transforms, and are stored and analyzing and processing by the data handling system in the computing machine.

As shown in Figure 2, on the outer wall of the miniature measuring channel of insulation two capacitive transducers with same structure are installed successively, spacing distance is l.The metal electrode that this sensor is W by two width constitutes.The measuring channel outer wall that installs capacitive transducer is surrounded by metal screen layer.

As shown in Figure 3, two metal electrodes of capacitive transducer are symmetrically distributed in the measuring channel outer wall, and the pairing subtended angle of electrode represents that with α the lead of drawing from electrode passes screen layer, is connected with the capacitance voltage change-over circuit.

As shown in Figure 4, data acquisition circuit is: digital signal processor is connected with A/D converter, programmable gain amplifier, instrument amplifier, D/A converter, CPLD, USB communication module respectively, D/A converter is connected with instrument amplifier, programmable gain amplifier, A/D converter successively, and CPLD is connected with D/A converter, instrument amplifier, programmable gain amplifier, A/D converter respectively.

Each original paper model adopts respectively: digital signal processor ADSP-2188N, CPLD XC9572XL, programmable gain amplifier AD526, instrument amplifier INA128, A/D converter AD7472BR, D/A converter TL5619.

Controlling of sampling is core with the digital signal processor, assist control with CPLD, during system works, computing machine sends to digital signal processor to order, and digital signal processor comes latch control signal by CPLD then; The USB communication module adopts highly integrated USB interface chip, USB interface chip intelligent engine can send data to computing machine automatically, other operation of this process of transmitting and digital signal processor walks abreast, after the data-signal that collects is sent to computing machine, realize analysis and processing on computers to signal.

As shown in Figure 5, the first capacitance voltage change-over circuit is identical with the second capacitance voltage converting circuit structure, and connected mode is the first electronic switch S ₁One end and second switch S ₂One end is through a capacitive transducer C _xWith the 3rd electronic switch S ₃An end, the 3rd capacitor C ₃An end, first operational amplifier A ₁Reverse input end is connected, second switch S ₂Other end ground connection, capacitive transducer C _xTwo ends respectively with first capacitor C ₁One end, second capacitor C, 2 one ends are connected first capacitor C ₁The other end and second capacitor C ₂Other end ground connection, first operational amplifier A ₁The output terminal and first resistance R ₁One end, the 3rd capacitor C ₃The other end, the 3rd switch S ₃The other end is connected, first resistance R ₁The other end and second resistance R ₂One end, second operational amplifier A ₂Reverse input end is connected, first operational amplifier A ₁The positive input and second operational amplifier A ₂Positive input ground connection, second operational amplifier A ₂The output terminal and second resistance R ₂The other end, the first sampling holder U ₁Input end, the second sampling holder U ₂Input end is connected, the first sampling holder U ₁Output terminal and the 4th capacitor C ₄One end, differential amplifier A ₃Reverse input end is connected, the second sampling holder U ₂Output terminal and the 5th capacitor C ₅One end, differential amplifier A ₃Positive input is connected, differential amplifier A ₃Output terminal and quadrielectron switch S ₄One end is connected, the 4th capacitor C ₄With the 5th capacitor C ₅The equal ground connection of the other end.

The break-make control of electronic switch encourages capacitive transducer excitation end, and the test side of capacitive transducer is responded to, and produces induced charge, to the 3rd capacitor C ₃Charging, the output voltage of second operational amplifier is sampled through sampling holder and is held, the difference of two sampling holder sustaining voltages of instrument amplifier output, this difference can reflect the capacitance signal on the sensor as the result of capacitance voltage change-over circuit.The job order of capacitance voltage change-over circuit is: (1) S ₃Disconnect, electronic switch has electric charge and injects C when disconnecting ₃, cause V ₁Place's voltage raises; (2) two sampling holders are sampled simultaneously, after sampling a period of time, and the first sampling holder U ₁Keep; (3) S ₂Disconnect S ₁Close, the capacitive transducer excited target produces induced charge in its test side, and induced charge is to C ₃Charging causes V ₁Further raise, according to the voltage superposition principle, this moment V ₁Be to disconnect the electric charge that produces and encourage the electric charge that produces to C by electronic switch ₃Common charging causes; (4) second sampling holder U ₂Sample and keep V ₃(5) difference of two sampling holder sustaining voltages of instrument amplifier output, it is to encourage the induced charge that produces to C ₃The change in voltage that charging causes, i.e. the result of capacitance voltage conversion.

Microtubule gas-liquid two-phase flow velocity measuring method based on electric capacity and cross-correlation method comprises the steps:

1) two capacitive transducer C that structure is identical _xBe installed on the miniature measuring channel outer wall of insulation, this sensor produces the independent capacitance signal of two groups of reflection gas-liquid two-phase flow containing rates distributed intelligence, is recorded by the capacitance voltage change-over circuit, and sends into computing machine by data acquisition circuit;

2) earlier two groups of capacitance signals are carried out normalization and handle, the signal E after handling with going average _X1, E _X2Carry out cross correlation process, the formula of cross correlation process is as follows:

$R_{E_{x1}{E}_{x2}}\left(j\right)=\frac{1}{N}\underset{n=1}{\overset{N}{\mathrm{\Σ}}}{E}_{x1}\left(n\right)E_{x2}(n+j),j=\mathrm{1,2,3}......,J$

Wherein:

N---be used for the number of the sampled point of cross-correlation calculation

3) according to by step 2) the cross correlation process result's that obtains peak of function position establishes the transit time τ of signal, and formula is as follows:

τ＝KΔt，

Wherein:

K---the signal lag of cross correlation function peak value correspondence is counted

Δ t---sampling interval

4) according to transit time τ and two capacitive transducer C of signal _xCenter distance L, determine the speed v of gas-liquid two-phase fluid in the micro-tube, formula is as follows:

$v=\frac{L}{\mathrm{\τ}}.$

Described to two groups of capacitance signals carry out normalization with go the average disposal route to comprise the steps:

1) two groups of capacitance signals are carried out normalized, the formula of normalized is as follows:

$C_{x1}^{\′}=\frac{C_{x1}-C_{01}}{C_{m1}-C_{01}}---\left(1\right)$

$C_{x2}^{\′}=\frac{C_{x2}-C_{02}}{C_{m2}-C_{02}}---\left(2\right)$

Wherein:

C ₀₁---first group of capacitance signal when all being gas in the measuring channel,

C ₀₂---second group of capacitance signal when all being gas in the measuring channel,

C _M1---first group of capacitance signal when all being liquid in the measuring channel,

C _M2---second group of capacitance signal when all being liquid in the measuring channel,

C ' _X1---first group of normalized result of capacitance signal,

C ' _X2---second group of normalized result of capacitance signal,

2) the signal C ' to obtaining by step 1) _X1, signal C ' _X2Go average to handle, the formula that goes average to handle is as follows:

E _x1＝C′ _x1-C′ _x1(3)

E _x2＝C′ _x2-C′ _x2(4)

Wherein:

C ' _X1---the average of signal after first group of normalization,

C ' _X2---the average of signal after second group of normalization,

E _X1---first group of signal after the past average is handled,

E _X2---second group of signal after the past average is handled.

Now the biphase gas and liquid flow that has formed at non-conductive medium air and glycerine is 1.56mm at internal diameter, 2.65mm, 3.96mm the horizontal glass pipeline on test, utilize apparatus and method mentioned among the present invention, the convection cell velocity range situation that is about 0～0.1m/s is tested, has obtained good effect.

Claims (4)

1. microtubule gas-liquid two-phase flow rate measuring device based on electric capacity and cross-correlation method, it is characterized in that: comprise that caliber is the miniature measuring channel of millimetre-sized insulation, two capacitive transducers that structure is identical are installed in the periphery of pipeline, two capacitive transducers respectively with the first capacitance voltage change-over circuit, the second capacitance voltage change-over circuit is connected, change-over circuit is connected with computing machine by data acquisition circuit, capacitive transducer is made of the metal electrode of two symmetries, be respectively excitation end (1) and test side (2), two electrodes are symmetry and be close to outer wall (3) installation of the miniature measuring channel that insulate mutually, electrode is connected with lead (4), and the whole measuring channel outside evenly surrounds metal screen layer (5); The described first capacitance voltage change-over circuit is identical with the second capacitance voltage converting circuit structure, and connected mode is the first electronic switch (S ₁) end and second switch (S ₂) end is through a capacitive transducer (C _x) and the 3rd electronic switch (S ₃) an end, the 3rd electric capacity (C ₃) an end, the first operational amplifier (A ₁) reverse input end is connected second switch (S ₂) other end ground connection, capacitive transducer (C _x) two ends respectively with the first electric capacity (C ₁) end, second electric capacity (C2) end be connected the first electric capacity (C ₁) other end and the second electric capacity (C ₂) other end ground connection, the first operational amplifier (A ₁) output terminal and the first resistance (R ₁) end, the 3rd electric capacity (C ₃) other end, the 3rd switch (S ₃) other end is connected the first resistance (R ₁) other end and the second resistance (R ₂) end, the second operational amplifier (A ₂) reverse input end is connected the first operational amplifier (A ₁) positive input and the second operational amplifier (A ₂) positive input ground connection, the second operational amplifier (A ₂) output terminal and the second resistance (R ₂) other end, the first sampling holder (U ₁) input end, the second sampling holder (U ₂) input end is connected the first sampling holder (U ₁) output terminal and the 4th electric capacity (C ₄) end, differential amplifier (A ₃) reverse input end is connected the second sampling holder (U ₂) output terminal and the 5th electric capacity (C ₅) end, differential amplifier (A ₃) positive input is connected differential amplifier (A ₃) output terminal and quadrielectron switch (S ₄) end is connected the 4th electric capacity (C ₄) and the 5th electric capacity (C ₅) the equal ground connection of the other end.

2. a kind of microtubule gas-liquid two-phase flow rate measuring device according to claim 1 based on electric capacity and cross-correlation method, it is characterized in that described data acquisition circuit is: digital signal processor respectively with A/D converter, programmable gain amplifier, instrument amplifier, D/A converter, CPLD, the USB communication module is connected, D/A converter and instrument amplifier, programmable gain amplifier, A/D converter is connected successively, CPLD respectively with D/A converter, instrument amplifier, programmable gain amplifier is connected with A/D converter.

3. the microtubule gas-liquid two-phase flow velocity measuring method based on electric capacity and cross-correlation method that use is installed according to claim 1 is characterized in that comprising the steps:

1) two capacitive transducer (C that structure is identical _x) be installed on the miniature measuring channel outer wall of insulation, this sensor produces the independent capacitance signal of two groups of reflection gas-liquid two-phase flow containing rates distributed intelligence, record by the first capacitance voltage change-over circuit and the second capacitance voltage change-over circuit, and send into computing machine by data acquisition circuit;

2) earlier two groups of capacitance signals are carried out normalization and handle, the signal E after handling with going average _X1, E _X2The formula that carries out cross correlation process is as follows:

$R_{E_{x1}{E}_{x2}}\left(j\right)=\frac{1}{N}\underset{n=1}{\overset{N}{\mathrm{\Σ}}}{E}_{x1}\left(n\right)E_{x2}(n+j),j=\mathrm{1,2,3}......,J$

Wherein:

N---be used for the number of the sampled point of cross-correlation calculation

3) according to by step 2) the cross correlation process result's that obtains peak of function position establishes the transit time τ of signal, and formula is as follows:

τ＝KΔt，

Wherein:

K---the signal lag of cross correlation function peak value correspondence is counted

Δ t---sampling interval

4) according to transit time τ and two capacitive transducer (C of signal _x) center distance L, determine the speed v of gas-liquid two-phase fluid in the micro-tube, formula is as follows:

$v=\frac{L}{\mathrm{\τ}}.$

4. a kind of microtubule gas-liquid two-phase flow velocity measuring method based on electric capacity and cross-correlation method according to claim 3 is characterized in that described elder generation carries out normalization and goes the average disposal route to comprise the steps: two groups of capacitance signals

1) two groups of capacitance signals are carried out normalized, the formula of normalized is as follows:

$C_{x1}^{\′}=\frac{C_{x1}-C_{01}}{C_{m1}-C_{01}}---\left(1\right)$

$C_{x2}^{\′}=\frac{C_{x2}-C_{02}}{C_{m2}-C_{02}}---\left(2\right)$

Wherein:

C ₀₁---first group of capacitance signal when all being gas in the measuring channel,

C ₀₂---second group of capacitance signal when all being gas in the measuring channel,

C _M1---first group of capacitance signal when all being liquid in the measuring channel,

C _M2---second group of capacitance signal when all being liquid in the measuring channel,

C ' _X1---first group of normalized result of capacitance signal,

C ' _X2---second group of normalized result of capacitance signal,

2) the signal C ' to obtaining by step 1) _X1, signal C ' _X2Go average to handle, the formula that goes average to handle is as follows:

E _x1＝C′ _x1-C′ _x1 (3)

E _x2＝C′ _x2-C′ _x2 (4)

Wherein:

C ' _X1---the average of signal after first group of normalization,

C ' _X2---the average of signal after second group of normalization,

E _X1---first group of signal after the past average is handled,

E _X2---second group of signal after the past average is handled.

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