CN100587492C - Device and method for measuring microtube gas-liquid two-phase flow velocity based on capacitance and cross-correlation method - Google Patents

Abstract

The invention discloses a microtube gas-liquid two-phase flow velocity measurement device and method based on capacitance and cross-correlation methods. It includes insulated miniature measuring pipes, two capacitive sensors, a capacitive voltage conversion circuit, a data acquisition circuit and a computer. Two capacitive sensors obtain two sets of capacitive signals reflecting the phase holdup distribution information of the gas-liquid two-phase flow, which are converted by the capacitive voltage and sent to the computer through the data acquisition circuit, and the cross-correlation of the two sets of capacitive measurement signals is calculated by using the principle of cross-correlation speed measurement The transit time of the signal is established according to the peak position of the cross-correlation function, and the flow velocity information of the gas-liquid two-phase in the pipeline is further obtained. The invention provides an effective way to solve the problem of non-conductive gas-liquid two-phase flow velocity measurement in micro-pipelines. The corresponding device has the advantages of simple structure, non-invasive effect on gas-liquid two-phase flow in the pipeline, and low cost. It is suitable for Continuous on-line measurement of non-conductive gas-liquid two-phase velocity in millimeter-scale micropipes.

Description

Device and method for measuring microtube gas-liquid two-phase flow velocity based on capacitance and cross-correlation method

technical field

The invention relates to the field of metering technology, in particular to a microtube gas-liquid two-phase flow velocity measurement device and method based on capacitance and cross-correlation methods.

Background technique

Two-phase flow exists widely in petrochemical industry and other fields. As a typical two-phase flow phenomenon, gas-liquid two-phase flow is very common in production practice. In-depth research on gas-liquid two-phase flow often requires measurement of parameters such as flow velocity and void fraction. Continuous on-line monitoring of these parameters is often difficult due to the complexity of two-phase flow systems.

The phenomenon of two-phase flow in micro-systems is a research hotspot nowadays, and has received more and more attention and attention. For example, micro-pipe reactors have been widely researched and applied in many industrial fields. Detection has also become a new direction in the field of multiphase flow parameter detection. As an important parameter of the two-phase flow phenomenon, the flow velocity is of great practical significance for its continuous on-line detection. At present, there are mainly two methods for detecting the two-phase flow velocity in micro-pipes: high-speed image photography and optical method. These methods are still in the stage of laboratory research. Although they are feasible, they are still not mature enough to be applied in the actual industrial environment. There is still a lack of effective methods for the detection of two-phase flow velocity in micro-pipes under industrial conditions, and further research is needed.

The capacitance method has a long history, and has the characteristics of simple structure and low cost, which is convenient for industrial application. The capacitance method mainly obtains the porosity information of non-conductive media, and has been successfully used in conventional scales. However, there are few reports in the literature for the environment of millimeter-scale micro-pipes, especially micro-pipes with a diameter of less than 5 mm. The combination of capacitance method and cross-correlation velocity measurement principle can realize the non-invasive online measurement of gas-liquid two-phase fluid velocity, which has not been used in the measurement of gas-liquid two-phase flow velocity in micro-pipelines so far.

Aiming at the current development status of gas-liquid two-phase velocity detection in micro-pipelines, the present invention proposes a measurement scheme based on the principle of capacitance method and cross-correlation velocity measurement, and designs a set of devices, including a capacitance sensor, a capacitance-voltage conversion circuit, a data acquisition circuit and a computer. , can realize the continuous on-line measurement of the flow velocity of the non-conductive gas-liquid two-phase fluid in the millimeter-scale micro-pipeline.

Contents of the invention

The purpose of the present invention is to provide a stable and reliable microtube gas-liquid two-phase flow velocity measurement device and method based on capacitance and cross-correlation method.

The microtube gas-liquid two-phase flow rate measurement device based on capacitance and cross-correlation method includes an insulated micro-measurement pipe with a diameter of millimeters, and two capacitive sensors with the same structure are installed on the periphery of the pipe. connection, the two capacitance sensors are respectively connected with the first capacitance voltage conversion circuit and the second capacitance voltage conversion circuit, the conversion circuit is connected with the computer through the data acquisition circuit, the capacitance sensor is composed of two symmetrical metal electrodes, which are respectively the excitation terminals and the detection end, the two electrodes are symmetrical to each other and are installed close to the outer wall of the insulated miniature measuring pipe, the electrodes are connected to the wires, and the outer side of the entire measuring pipe is evenly surrounded by a metal shielding layer.

The first capacitive voltage conversion circuit and the second capacitive voltage conversion circuit have the same structure, and the connection mode is that one end of the first electronic switch and one end of the second switch pass through the capacitive sensor, one end of the third electronic switch, one end of the third capacitor, The inverting input terminal of the first operational amplifier is connected, the other end of the second switch is grounded, the two ends of the capacitive sensor are respectively connected to one end of the first capacitor and one end of the second capacitor, the other end of the first capacitor and the other end of the second capacitor are grounded, and the other end of the second capacitor is connected to the ground. The output end of an operational amplifier is connected to one end of the first resistor, the other end of the third capacitor, and the other end of the third switch, the other end of the first resistor is connected to one end of the second resistor, and the reverse input end of the second operational amplifier is connected, and the first operational amplifier The positive input terminal of the amplifier and the positive input terminal of the second operational amplifier are grounded, the output terminal of the second operational amplifier is connected with the other end of the second resistor, the input terminal of the first sample holder, and the input terminal of the second sample holder, and the first sampling The output terminal of the keeper is connected with one terminal of the fourth capacitor and the reverse input terminal of the differential amplifier, the output terminal of the second sample holder is connected with one terminal of the fifth capacitor and the positive input terminal of the differential amplifier, and the output terminal of the differential amplifier is connected with the fourth electronic switch One ends are connected, and the other ends of the fourth capacitor and the fifth capacitor are grounded.

The data acquisition circuit is as follows: the digital signal processor is respectively connected with the A/D converter, the programmable gain amplifier, the instrument amplifier, the D/A converter, the complex programmable logic device, and the USB communication module, and the D/A conversion The device is connected with the instrumentation amplifier, the programmable gain amplifier, and the A/D converter in turn, and the complex programmable logic device is respectively connected with the D/A converter, the instrumentation amplifier, the programmable gain amplifier, and the A/D converter. The programming logic device is respectively connected with the D/A converter, the instrumentation amplifier, the programmable gain amplifier and the A/D converter.

The microtube gas-liquid two-phase velocity measurement method based on capacitance and cross-correlation method comprises the following steps:

1) Two capacitive sensors with the same structure are installed on the outer wall of the insulated miniature measuring pipe. The sensors generate two sets of independent capacitive signals reflecting the phase holdup distribution information of the gas-liquid two-phase flow, which are converted by the first capacitive voltage conversion circuit and the second capacitive Measured by the voltage conversion circuit, and sent to the computer by the data acquisition circuit;

2) Perform normalization and de-meaning processing on the two sets of capacitance signals first, and perform cross-correlation processing on the processed signals E _x1 and E _x2 . The formula for cross-correlation processing is as follows:

${\mathrm{<span\; class="notranslate">\; R</span>}}_{{\mathrm{<span\; class="notranslate">\; E.</span>}}_{\mathrm{<span\; class="notranslate">\; x</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; E.</span>}}_{\mathrm{<span\; class="notranslate">\; x</span>}\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; j</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; N</span>}}\underset{\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\overset{\mathrm{<span\; class="notranslate">\; N</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}{\mathrm{<span\; class="notranslate">\; E.</span>}}_{\mathrm{<span\; class="notranslate">\; x</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span>{\mathrm{<span\; class="notranslate">\; E.</span>}}_{\mathrm{<span\; class="notranslate">\; x</span>}\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; j</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; j</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1,2,3</span>}<span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; J</span>}$

in:

N——the number of sampling points used for cross-correlation calculation

3) according to the function peak position of the cross-correlation processing result obtained by step 2) establish the transit time τ of the signal, the formula is as follows:

τ=KΔt,

in:

K—the number of signal lag points corresponding to the peak value of the cross-correlation function

Δt——sampling interval

4) According to the transit time τ of the signal and the center distance L of the two capacitive sensors, determine the velocity v of the gas-liquid two-phase fluid in the micropipeline, the formula is as follows:

$\mathrm{<span\; class="notranslate">\; v</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; L</span>}}{\mathrm{<span\; class="notranslate">\; \&tau;</span>}}<span\; class="notranslate">\; .</span>$

The method for normalizing and removing the average value of two groups of capacitance signals includes the following steps:

1) Perform normalization processing on two sets of capacitance signals, the formula of normalization processing is as follows:

${\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; x</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; x</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; 01</span>}}}{{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; 01</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>$

${\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; x</span>}\mathrm{<span\; class="notranslate">\; 2</span>}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; x</span>}\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; 02</span>}}}{{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; 02</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>$

in:

C ₀₁ ——the first group of capacitance signals when the measuring pipeline is all gas,

C ₀₂ ——The second group of capacitance signals when the measuring pipeline is full of gas,

C _m1 ——the first set of capacitance signals when all the pipes are liquid,

C _m2 ——the second set of capacitance signals when all the pipes are liquid,

C′ _x1 ——the normalized result of the first group of capacitive signals,

C′ _x2 ——the normalized result of the second group of capacitance signals,

2) The signal C′ _x1 obtained by step 1), the signal C′ _x2 is carried out to remove the mean value, and the formula for removing the mean value is as follows:

E _x1 ＝C′ _x1 -C′ _x1 (3)

E _x2 ＝C′ _x2 -C′ _x2 (4)

in:

C′ _x1 ——the mean value of the first group of normalized signals,

C′ _x2 ——the mean value of the second group of normalized signals,

E _x1 ——the first group of signals after de-average processing,

_Ex2 ——The second group of signals after de-averaging processing.

The invention can be used for online measurement of non-conductive gas-liquid two-phase flow velocity in millimeter-scale micro-pipelines. The corresponding device has the advantages of simple structure, non-invasive effect on gas-liquid two-phase flow in the pipeline, and low cost, and is suitable for micro-pipelines Continuous on-line measurement of non-conductive gas-liquid two-phase flow rate.

Description of drawings

Fig. 1 is the structure schematic diagram of the micropipe gas-liquid two-phase velocity measurement device based on capacitance and cross-correlation method;

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

Fig. 3 is the sectional view of capacitive sensor of the present invention along the pipe section direction;

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

Fig. 5 is a circuit diagram of a capacitance-to-voltage conversion circuit of the present invention.

Detailed ways

As shown in Figure 1, the microtube gas-liquid two-phase flow velocity measurement device based on the capacitance and cross-correlation method includes an insulated micro-measurement pipe with a diameter of millimeters, and two capacitive sensors with the same structure are installed on the periphery of the pipe. The capacitance sensor is connected with the first capacitance voltage conversion circuit and the second capacitance voltage conversion circuit respectively, and the capacitance voltage conversion circuit is connected with the computer through the data acquisition circuit. The capacitance sensor is composed of two symmetrical metal electrodes, which are respectively excitation terminal 1 and At the detection end 2, the two electrodes are symmetrical to each other and are installed close to the outer wall 3 of the insulated miniature measuring pipe, the electrodes are connected to the wire 4, and the outer side of the entire measuring pipe is evenly surrounded by a metal shielding layer 5.

The two capacitive sensors obtain two sets of capacitive signals reflecting the phase holdup distribution information of the gas-liquid two-phase flow, which are converted into the capacitive voltage and transmitted to the computer through the data acquisition circuit, and are stored and analyzed by the data processing system in the computer.

As shown in Figure 2, two capacitive sensors with the same structure are sequentially installed on the outer wall of the insulated micro-measurement pipe, with an interval of l. The sensor consists of two metal electrodes with a width W. The outer wall of the measuring pipe where the capacitive sensor is mounted is surrounded by a metal shield.

As shown in Figure 3, the two metal electrodes of the capacitive sensor are symmetrically distributed on the outer wall of the measuring pipe, and the opening angle corresponding to the electrodes is represented by α. The wires drawn from the electrodes pass through the shielding layer and are connected to the capacitive voltage conversion circuit.

As shown in Figure 4, the data acquisition circuit is: the digital signal processor is connected with the A/D converter, the programmable gain amplifier, the instrument amplifier, the D/A converter, the complex programmable logic device, and the USB communication module respectively, and the D The /A converter is connected to the instrumentation amplifier, programmable gain amplifier, and A/D converter in turn, and the complex programmable logic device is respectively connected to the D/A converter, instrumentation amplifier, programmable gain amplifier, and A/D converter. .

The original models are respectively: digital signal processor ADSP-2188N, complex programmable logic device XC9572XL, programmable gain amplifier AD526, instrumentation amplifier INA128, A/D converter AD7472BR, D/A converter TL5619.

The sampling control takes the digital signal processor as the core, and the complex programmable logic device is used for auxiliary control. When the system is working, the computer sends the command to the digital signal processor, and then the digital signal processor latches the control signal through the complex programmable logic device. ;The USB communication module adopts a highly integrated USB interface chip, and the intelligent engine of the USB interface chip will automatically send data to the computer. This sending process is parallel to other operations of the digital signal processor. After the collected data signal is sent to the computer, the Analyze and process the signal on the computer.

As shown in Figure 5, the first capacitive voltage conversion circuit and the second capacitive voltage conversion circuit have the same structure, and the connection mode is that one end of the first electronic switch _S1 and one end of the second switch _S2 pass through a capacitive sensor _Cx and a third electronic One end of the switch _S3 , one end of the third capacitor _C3 , and the reverse input end of the first operational amplifier _A1 are connected, the other end of the second switch _S2 is grounded, and the two ends of the capacitive sensor _Cx are respectively connected to one end of the first capacitor _C1 1. One end of the second capacitor C2 is connected, the other end of the first capacitor _C1 and the other end of the second capacitor _C2 are grounded, the output end of the first operational amplifier _A1 is connected to one end of the first resistor _R1 , and the other end of the third capacitor _C3 , The other end of the third switch _S3 is connected, the other end of the first resistor _R1 is connected to one end of the second resistor _R2 , the inverting input end of the second operational amplifier _A2 is connected, and the positive input end of the first operational amplifier _A1 is connected to the first end of the second operational amplifier A1. The positive input terminal of the second operational amplifier _A2 is grounded, the output terminal of the second operational amplifier _A2 is connected to the other end of the second resistor _R2 , the input terminal of the first sample holder _U1 , and the input terminal of the second sample holder _U2 , The output terminal of the first sample-and-hold unit _U1 is connected to one terminal of the fourth capacitor _C4 and the inverting input terminal of the differential amplifier _A3 , and the output terminal of the second sample-and-hold unit _U2 is connected to one terminal of the fifth capacitor _C5 and the positive terminal of the differential amplifier _A3. connected to the input terminal, the output terminal of the differential amplifier _A3 is connected to one terminal of the fourth electronic switch _S4 , and the other terminals of the fourth capacitor _C4 and the fifth capacitor _C5 are grounded.

The on-off control of the electronic switch excites the excitation end of the capacitive sensor, and the detection end of the capacitive sensor is induced to generate an induced charge, which charges the third capacitor _C3 , and the output voltage of the second operational amplifier is sampled and held by the sample holder. The instrumentation amplifier outputs the difference between the voltages held by the two sample-and-hold devices, and this difference, as the result of the capacitance-to-voltage conversion circuit, can reflect the capacitance signal on the sensor. The working sequence of the capacitance-voltage conversion circuit is: (1) S ₃ is disconnected, and charge will be injected into C ₃ when the electronic switch is disconnected, causing the voltage at V ₁ to rise; After a period of time, the first sample-and-hold device U ₁ is held; (3) S ₂ is disconnected and S ₁ is closed, the capacitive sensor is excited, and an induced charge is generated at its detection terminal, and the induced charge charges C ₃ , causing V ₁ to further rise High, according to the principle of voltage superposition, at this time _V1 is caused by the charge generated by the electronic switch disconnection and the charge generated by the excitation to charge _C3 together; (4) The second sample holder _U2 samples and holds _V3 ; (5) The instrumentation amplifier outputs the difference between the voltage held by the two sample holders, which is the voltage change caused by the induced charge generated by the excitation to charge _C3 , that is, the result of the capacitor voltage conversion.

The microtube gas-liquid two-phase velocity measurement method based on the capacitance and cross-correlation method comprises the following steps:

1) Two capacitive sensors C _x with the same structure are installed on the outer wall of the insulated miniature measuring pipe. The sensors generate two sets of independent capacitive signals reflecting the phase holdup distribution information of the gas-liquid two-phase flow, which are measured by the capacitive-voltage conversion circuit, and sent to the computer by the data acquisition circuit;

2) Perform normalization and de-meaning processing on the two sets of capacitance signals first, and perform cross-correlation processing on the processed signals E _x1 and E _x2 . The formula for cross-correlation processing is as follows:

${\mathrm{<span\; class="notranslate">\; R</span>}}_{{\mathrm{<span\; class="notranslate">\; E.</span>}}_{\mathrm{<span\; class="notranslate">\; x</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; E.</span>}}_{\mathrm{<span\; class="notranslate">\; x</span>}\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; j</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; N</span>}}\underset{\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\overset{\mathrm{<span\; class="notranslate">\; N</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}{\mathrm{<span\; class="notranslate">\; E.</span>}}_{\mathrm{<span\; class="notranslate">\; x</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span>{\mathrm{<span\; class="notranslate">\; E.</span>}}_{\mathrm{<span\; class="notranslate">\; x</span>}\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; j</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; j</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1,2,3</span>}<span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; J</span>}$

in:

N——the number of sampling points used for cross-correlation calculation

3) according to the function peak position of the cross-correlation processing result obtained by step 2) establish the transit time τ of the signal, the formula is as follows:

τ=KΔt,

in:

K—the number of signal lag points corresponding to the peak value of the cross-correlation function

Δt——sampling interval

4) According to the transit time τ of the signal and the center-to-center distance L of the two capacitive sensors _Cx , the velocity v of the gas-liquid two-phase fluid in the micropipeline is determined, the formula is as follows:

$\mathrm{<span\; class="notranslate">\; v</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; L</span>}}{\mathrm{<span\; class="notranslate">\; \&tau;</span>}}<span\; class="notranslate">\; .</span>$

The method for normalizing and removing the average value of two groups of capacitance signals includes the following steps:

1) Perform normalization processing on two sets of capacitance signals, the formula of normalization processing is as follows:

${\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; x</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; x</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; 01</span>}}}{{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; 01</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>$

${\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; x</span>}\mathrm{<span\; class="notranslate">\; 2</span>}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; x</span>}\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; 02</span>}}}{{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; 02</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>$

in:

C ₀₁ ——the first group of capacitance signals when the measuring pipeline is all gas,

C ₀₂ ——The second group of capacitance signals when the measuring pipeline is full of gas,

C _m1 ——the first set of capacitance signals when all the pipes are liquid,

C _m2 ——the second set of capacitance signals when all the pipes are liquid,

C′ _x1 ——the normalized result of the first group of capacitive signals,

C′ _x2 ——the normalized result of the second group of capacitance signals,

2) The signal C′ _x1 obtained by step 1), the signal C′ _x2 is carried out to remove the mean value, and the formula for removing the mean value is as follows:

E _x1 ＝C′ _x1 -C′ _x1 (3)

E _x2 ＝C′ _x2 -C′ _x2 (4)

in:

C′ _x1 ——the mean value of the first group of normalized signals,

C′ _x2 ——the mean value of the second group of normalized signals,

E _x1 ——the first group of signals after de-average processing,

_Ex2 ——The second group of signals after de-averaging processing.

It is 1.56mm, 2.65mm, and the test has been carried out on the horizontal glass pipe of 3.96mm for the gas-liquid two-phase flow that the non-conductive medium air and glycerin form now, utilize the device and method mentioned in the present invention, to The fluid velocity range is about 0-0.1m/s, and good results have been obtained.

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:

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

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:

$v=\frac{L}{\mathrm{\&tau;}}.$

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:

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

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

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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