CN108931270B - Two-phase flow parameter detection method based on porous throttling and acoustic emission technology - Google Patents

Abstract

The invention provides a two-phase flow parameter detection method based on porous throttling and acoustic emission technology. The invention realizes the combined measurement of differential pressure measurement based on perforated orifice plate and flow noise measurement based on acoustic emission technology, and solves the problem of noise interference when using acoustic emission to measure two-phase flow. The detection method in the present invention can eliminate or weaken the vibration noise of the pipeline itself, the inherent noise of the power source such as the water pump and air compressor, and also has the effect of reducing or even eliminating the influence of noise sources from other parts. At the same time, through rational design, the present invention fully utilizes the advantages of the porous orifice plate and the acoustic emission technology in their respective measurement methods, makes the combination of the two measurement methods more reasonable and effective, and realizes the two-phase flow quantification based on the acoustic emission technology. Measurement.

Description

Two-phase flow parameter detection method based on porous throttling and acoustic emission technology

technical field

The invention relates to the technical field of gas-liquid two-phase flow detection, in particular to a two-phase flow parameter detection method based on porous throttling and acoustic emission technology.

Background technique

Differential pressure flowmeter is one of the most widely used flowmeters in two-phase flow measurement. It is based on a split-phase or homogeneous model to establish the relationship between flow and pressure drop. Among them, the throttling differential pressure flowmeter has the longest research history, and the differential pressure method is basically found in the throttling flowmeter. The flowmeter has the advantages of convenient installation and reliable operation, and has formed a mature international standard in the course of many years of research. At present, many manufacturers' multiphase flow measurement systems contain differential pressure flowmeters. The widely used throttling differential pressure flowmeters are orifice, venturi, and V-cone flowmeters.

The fluid flows through the orifice plate throttling device in the pipeline, causing local contraction near the orifice plate, and a pressure drop occurs before and after the throttling member, that is, differential pressure. The differential pressure signal is related to the flow rate. There have been many improvements in the design of the orifice flowmeter. Japan SONIC has designed and developed an orifice flowmeter that can select the range of the turndown ratio on the flow computer. Compared with the traditional orifice flowmeter, its The measurement range has been expanded; the newly researched new intelligent orifice flow meter directly sends the temperature and pressure signals into the on-site flow computer, and automatically compensates for the temperature and pressure according to the flow change.

Xu Lijun of Beihang University proposed a wet gas measurement model based on the split-phase flow model by using a long-throat venturi tube; Zhang Qiang et al. of Tianjin University used a long-throat venturi tube for gas-liquid two-phase flow measurement, and established a double differential pressure Moisture gas flow measurement model. The method of using a throttling device and other sensors for combined measurement has also been studied a lot. Huang Zhiyao et al. used Venturi tube combined with capacitance tomography to effectively measure oil and gas two-phase flow; The combined method in this paper proposes a false height model for moisture measurement.

Because of its simple structure and durability, orifice flowmeter has become a kind of flowmeter with a high degree of standardization and the most widely used in the world. There are disadvantages such as unstable outflow coefficient, poor linearity, low repeatability, and large permanent pressure loss. A new type of differential pressure flow measurement device designed and invented by the Marshall Aviation Flight Center in the United States, namely the porous orifice flowmeter. Compared with the traditional differential pressure flowmeter, the perforated orifice flowmeter has the advantages of small permanent pressure loss, high precision, large range ratio and short straight pipe section.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a two-phase flow parameter detection method based on porous throttling and acoustic emission technology, through which quantitative measurement of two-phase flow based on acoustic emission technology can be realized.

The object of the present invention is achieved in this way: a two-phase flow parameter detection method based on porous throttling and acoustic emission technology, comprising the following steps:

a. Build a two-phase flow parameter detection device based on porous throttling and acoustic emission technology;

The two-phase flow parameter detection device based on porous throttling and acoustic emission technology includes a porous balance flowmeter, a differential pressure transmitter, an acoustic emission probe, a data acquisition unit and a data processing unit;

The porous balance flowmeter includes a front straight pipe section, a rear straight pipe section, and a porous orifice plate arranged between the front straight pipe section and the rear straight pipe section; the diameter of the porous orifice plate is larger than the diameter of the two straight pipe sections, A number of throttle holes are opened on the perforated orifice plate at positions opposite to the two sections of straight pipe lumens, and a number of through holes are uniformly opened along the circumference on the edge of the perforated orifice plate extending out of the two sections of straight pipes; The acoustic emission probe is correspondingly placed in the through hole on the edge of the perforated orifice plate; a pressure taking hole is opened on the side walls of the front straight pipe section and the rear straight pipe section, and the differential pressure transmitter is connected to the two take-off holes. Press holes are connected;

b. Make the two-phase flow flow in from the front straight pipe section, and flow into the back straight pipe section after passing through the orifice on the perforated orifice plate;

c. The differential pressure transmitter detects the pressure difference signal in the front straight pipe section and the rear straight pipe section, and at the same time, the acoustic emission probe detects the flow sound signal of the fluid;

d. The data acquisition unit collects the signals detected by the differential pressure transmitter and the acoustic emission probe, and sends the collected signals to the data processing unit;

e. The data processing unit receives the signal sent by the data acquisition unit, and processes and calculates the received flow acoustic signal and pressure difference signal of the two-phase flow, thereby obtaining the flow rate and phase holdup of the two-phase flow.

Step e is as follows:

The data processing unit obtains the characteristic frequency band according to the flow acoustic signal of the two-phase flow, and extracts the energy characteristic value E in the characteristic frequency band, and calculates the gas phase volume fraction β _g according to the energy characteristic value E in combination with the following formula:

β _g = 0.44214ln(E+663.0423)-2.87159

The data processing unit calculates the total mass flow W _m of the two-phase flow according to the following formula according to the gas phase volume fraction β _g and the pressure difference between the front and rear straight pipe sections:

In the above formula, ε is the expansion coefficient of the two-phase flow, C is the outflow coefficient, D is the inner diameter of the front straight pipe section and the rear straight pipe section, β is the equivalent diameter ratio of the perforated orifice plate, and Δp _tp is the two-phase flow in the two-phase flow. The pressure difference in each straight pipe section, x is the mass gas content, x can be obtained from the gas volume content β _g , ρ _g is the density of the gas phase fluid, ρ _l is the density of the liquid fluid;

The formula for calculating the equivalent diameter ratio β of the porous plate is as follows:

In the above formula, d is the diameter of the orifice, D is the inner diameter of the front straight pipe section and the rear straight pipe section, and N is the number of the orifice.

In step a, the inner diameters of the front straight pipe section and the rear straight pipe section are both D, the length L ₁ of the front straight pipe section satisfies: L ₁ ≥D, and the length L ₂ of the rear straight pipe section satisfies: L ₂ ≥ 1.5D; The distance between the pressing hole and the perforated plate is D.

In step a, the throttle holes on the porous orifice plate are evenly distributed on one or more concentric circles centered on the center of the porous orifice plate; and each throttle hole has a front chamfer of 45° and a 45° back chamfer.

In step a, flanges are provided at both ends of the front straight pipe section and the rear straight pipe section, and the porous orifice plate is connected to the front straight pipe section and the rear straight pipe section through the flanges adjacent to the front straight pipe section and the rear straight pipe section. The connection between the pipe sections; the outer edge of the perforated orifice plate extends to the outside of the outer edge of the flange connected to it, and the through hole for placing the acoustic emission probe is opened in the perforated orifice plate and extends to the outside of the flange on the edge of the flange; the flange and the perforated plate are fixedly connected by bolts.

In step a, two small holes located on the extension line of the diameter of the through hole are opened around each through hole on the perforated orifice plate, and the acoustic emission in the through hole can be realized by the nylon tie passing through the two small holes. Fixation of the probe.

The invention is optimized on the basis of the existing porous balance flowmeter, and solves the problem of using the acoustic emission measurement method by combining the differential pressure measurement based on the porous orifice plate and the flow noise measurement based on the acoustic emission technology. The problem of noise interference in phase flow. The detection method in the present invention can eliminate or weaken the vibration noise of the pipeline itself, the inherent noise of the power source such as the water pump and air compressor, and also has the effect of reducing or even eliminating the influence of noise sources from other parts. At the same time, through rational design, the present invention fully utilizes the advantages of the porous orifice plate and the acoustic emission technology in their respective measurement methods, makes the combination of the two measurement methods more reasonable and effective, and realizes the two-phase flow quantification based on the acoustic emission technology. Measurement.

The invention realizes the combination of porous throttling and acoustic emission technology to measure the two-phase flow. The use of perforated orifice plates to measure the flow of two-phase flow not only has the characteristics of good throttling effect and low requirements for upstream and downstream straight pipe sections, but also has good noise reduction characteristics, which can greatly reduce the interference of other noise sources and make the transmission signal is more stable. Two-phase flow is more complicated than single-phase flow, which is related to the distribution and flow pattern of the two-phase. Under the same phase holdup, the distribution state of the two phases is different, and their hydrodynamic properties and heat and mass transfer properties will also be different, and in the same two-phase flow system, the phase interface and phase distribution of the two phases change randomly with the flow process. , which makes the two-phase flow characteristics more complex and changeable, so the flow pattern of the two-phase flow seriously affects the measurement of the two-phase flow. In the porous balance flowmeter of the present invention, on the basis of the original porous orifice plate structure, the size of the orifice plate is extended to achieve the purpose of arranging the acoustic emission probe. The acoustic emission probe for collecting the flow acoustic signal has a simple arrangement, and the entire detection device combined with the porous plate has a compact structure. The detection of the flow acoustic signal by the acoustic emission probe and the differential pressure measurement of the porous balance flowmeter do not interfere with each other. The arrangement position is located on the perforated orifice plate, so it can effectively reduce the interference of noise, the collected flow sound signal has good reliability, and the measurement result is more accurate, and this measurement form is more reasonable and effective.

Description of drawings

FIG. 1 is a schematic structural diagram of a porous balance flowmeter in the present invention.

FIG. 2 is a schematic structural diagram of the porous balance flowmeter in FIG. 1 after being disassembled.

FIG. 3 is a cross-sectional view of FIG. 1 .

Figure 4 is a schematic diagram of the structure of the porous plate in the present invention.

In the figure: 1. Front straight pipe section, 2. Rear straight pipe section, 3. Perforated orifice plate, 4. Flange plate, 5. Pressure pipe, 6. Through hole, 7. Orifice, 8. Bolt hole, 9 , small holes.

Detailed ways

The two-phase flow parameter detection method based on porous throttling and acoustic emission technology provided by the present invention relies on a detection device (the full name is a two-phase flow parameter detection device based on porous throttling and acoustic emission technology), and the detection device includes a porous balance Flow meter, differential pressure transmitter, acoustic emission probe, data acquisition unit and data processing unit. Among them, the structure of the porous balance flowmeter is shown in FIGS. 1 to 3 .

The porous balance flowmeter in the present invention is composed of two straight pipe sections and a porous orifice plate. Specifically, the porous balance flowmeter includes a front straight pipe section 1, a rear straight pipe section 2, and is located between the front straight pipe section 1 and the rear straight pipe section 2. The multi-well plate 3. The front straight pipe section 1 and the rear straight pipe section 2 are both stainless steel straight pipe sections. The front straight pipe section 1 is also called the upstream straight pipe section, and the rear straight pipe section 2 is also called the downstream straight pipe section. The fluid flows from the front straight pipe section 1 to the rear straight pipe section 2, as shown by the arrow in Figure 3 .

The inner diameters of the front straight pipe section 1 and the rear straight pipe section 2 are both D, and the diameter of the perforated orifice plate 3 is larger than the diameters of the front straight pipe section 1 and the rear straight pipe section 2 . The center of the perforated orifice plate 3 is on the axis line of the front straight pipe section 1 and the rear straight pipe section 2 . In the present invention, flanges 4 are provided at both ends of the front straight pipe section 1 and the rear straight pipe section 2, and the perforated orifice plates 3 are in close contact with the flanges 4 at the ends of the front straight pipe section 1 and the rear straight pipe section 2 respectively. , and the porous plate 3 and the flange 4 are fixedly connected by bolts. The outer edge of the perforated orifice plate 3 protrudes to the outside of the outer edge of the adjacent flange plate 4 , that is, the diameter of the perforated orifice plate 3 is larger than the outer diameter of the flange plate 4 . Bolt holes are opened on the flange plate 4, and bolt holes 8 corresponding to the bolt holes on the flange plate 4 are opened on the perforated plate 3 (as shown in Figure 4). The fastened connection between the perforated plate 3 and the flange 4 is realized. The bolt holes are generally evenly located on a circle with the center of the perforated plate 3 (or the center of the flange 4 ) as the center.

As shown in FIG. 4 , a number of throttle holes 7 are provided on the perforated orifice plate 3 at the positions opposite to the lumens of the front straight pipe section 1 and the rear straight pipe section 2. The fluid enters from the front straight pipe section 1 and passes through the holes on the perforated orifice plate 3. The orifice 7 flows into the rear straight pipe section 2 . The orifice 7 is an orifice with a chamfer, specifically: the orifice 7 has a front chamfer of 45° and a rear chamfer of 45°. In this embodiment, there are 13 orifices 7 with the same size. Among them, there is a throttle hole in the center of the perforated orifice plate 3, and the remaining 12 throttle holes are divided into two groups, one group is 8, the other group is 4, and these two groups of throttle holes are located in the On the circle with the perforated orifice plate 3 as the center, the circles where the two groups of orifices are located are concentric circles, and the circle where the eight orifices are located is located outside the circle where the four orifices are located.

A plurality of through holes 6 are evenly opened along the circumference on the edge of the perforated orifice plate 3 extending to the outside of the flange 4, and an acoustic emission probe is placed in each through hole 6. The acoustic emission probe can detect when the fluid passes through the perforated orifice plate 3. flow sound signal. Two small holes 9 on the extension line of the diameter of the through hole are opened around each through hole 6 , and the acoustic emission probe in the through hole 6 can be fixed by a nylon tie passing through the two small holes 9 . The acoustic emission probe is connected to the data acquisition unit, and the data acquisition unit can collect the flow acoustic signal of the fluid detected by the acoustic emission probe, and send the collected fluid flow acoustic signal to the data processing unit.

In the present invention, the inner diameters of the front straight pipe section 1 and the rear straight pipe section 2 are both D, the length L ₁ of the front straight pipe section 1 satisfies: L ₁ ≥D, and the length L ₂ of the rear straight pipe section 2 satisfies: L ₂ ≥ 1.5D. A pressure taking hole is provided on the side walls of the front straight pipe section 1 and the rear straight pipe section 2, and the distances between the two pressure taking holes and the porous orifice plate 3 are both D. A pressure taking pipe 5 is arranged on each pressure taking hole, and the pressure taking pipe 5 is connected with the differential pressure transmitter. The differential pressure transmitter is used to detect the pressure difference signal of the fluid in the front straight pipe section 1 and the rear straight pipe section 2. The differential pressure transmitter is connected with the data acquisition unit at the same time, and the data acquisition unit can collect the differential pressure signal detected by the differential pressure transmitter, and send the collected differential pressure signal to the data processing unit.

The data processing unit processes and calculates the received flow sound signal and pressure difference signal of the two-phase flow, thereby obtaining the flow rate and phase holdup of the two-phase flow.

The two-phase flow parameter detection method based on porous throttling and acoustic emission technology provided by the present invention comprises the following steps:

a. Build a two-phase flow parameter detection device based on porous throttling and acoustic emission technology as described above.

b. The two-phase flow flows in from the front straight pipe section, and flows into the back straight pipe section after passing through the orifice on the perforated orifice plate.

c. The differential pressure transmitter detects the pressure difference signal in the front straight pipe section and the rear straight pipe section, and at the same time, the acoustic emission probe detects the flow acoustic signal of the fluid.

d. The data acquisition unit collects the signals detected by the differential pressure transmitter and the acoustic emission probe, and sends the collected signals to the data processing unit.

e. The data processing unit receives the signal sent by the data acquisition unit, and processes and calculates the received flow acoustic signal and pressure difference signal of the two-phase flow, thereby obtaining the flow rate and phase holdup of the two-phase flow.

The invention tests the two-phase flow through the acoustic emission technology, extracts valuable flow acoustic signals, extracts the signal features, identifies the flow pattern, calculates the gas phase volume content, and establishes a mathematical model. Based on different gas phase volume fractions, combined with the differential pressure signal measured by the porous balance flowmeter, a flow measurement formula is established. The measurement method of the two-phase flow detection device of this model is studied to verify the rationality and feasibility of the measurement device. The phase holdup and total flow measurement models are established as follows:

The characteristic frequency band is obtained by preliminary analysis of the flow acoustic signal, and the energy characteristic value in the characteristic frequency band can effectively reflect the gas phase volume fraction β _g in the two-phase flow. Extract the energy characteristic value E in the characteristic frequency band, and obtain the gas phase volume fraction measurement model (corresponding to the following formula):

β _g = 0.44214ln(E+663.0423)-2.87159

The gas phase volume fraction β _g can be obtained from the gas phase volume fraction measurement model. According to the volume fraction of gas phase β _g , it is easy to obtain the volume fraction of liquid phase: β _l =1-β _g .

According to the gas phase volume fraction β _g and the collected pressure difference signal, compare the existing empirical models of flow measurement, and select the measurement model suitable for this device for optimization. The two-phase flow measurement model based on this detection device can be obtained as follows:

In the above formula, W _m is the total mass flow rate of the two-phase flow, ε is the expansion coefficient of the two-phase flow, C is the outflow coefficient, D is the inner diameter of the front straight pipe section and the rear straight pipe section, and β is the equivalent of the porous orifice plate. Diameter ratio, Δp _tp is the pressure difference between the two-phase flow in the front straight pipe section and the back straight pipe section, x is the mass gas content, x can be obtained from the gas volume content β _g (β _g multiplied by ρ _g is the mass content. Gas rate x), ρ _g is the density of the gas phase fluid, ρ _l is the density of the liquid phase fluid.

The formula for calculating the equivalent diameter ratio β of the porous plate is as follows:

In the above formula, d is the diameter of the orifice, D is the inner diameter of the front straight pipe section and the rear straight pipe section, and N is the number of the orifice.

According to the two-phase flow measurement model, the total mass flow of the two-phase flow can be obtained.

By setting the diameter of the perforated orifice plate to be larger than the diameter of the two straight pipe sections, and arranging a number of acoustic emission probes on the periphery of the perforated orifice plate, the invention can reasonably and effectively combine the measurement of the two-phase flow by the porous balance flowmeter with the acoustic emission technology. Non-separation measurement of two-phase flow.

The principle of acoustic emission detection is: the elastic wave emitted by the internal sound source of the material propagates to the surface of the material, causing surface displacement that can be detected by acoustic emission sensors. These detectors convert the mechanical vibration of the material into electrical signals, which are then amplified and processed. and records. Acoustic emission signal energy mainly comes from the detected object itself, it does not need the excitation of external devices, so it can realize non-invasive measurement. When the two-phase flow fluid flows through the porous balance flowmeter of the present invention, the acoustic signal generated by the fluid hitting the porous plate is received by the acoustic emission probe, and is converted into an electrical signal by the piezoelectric effect in the data processing unit. The data processing method obtains the signal characteristic parameters, which have a quantitative relationship with the gas phase volume fraction, and then establishes a measurement model of the gas phase volume fraction. The pressure taking hole of the porous balance flowmeter is connected with the differential pressure transmitter to obtain the differential pressure signal when the fluid flows through. Based on the continuity equation, Bernoulli equation and the gas volume holdup measurement model, the mathematical model of the two-phase flow is finally established. . The flow rate of each phase can be obtained from the total flow rate and the volume fraction of the gas phase, thereby realizing the online detection of the two-phase flow parameters. Since the acoustic emission probe is located on the porous orifice plate, it can effectively reduce the interference of noise. The flow acoustic signal has good reliability, and this measurement form is more reasonable and effective.

Claims (5)

1. a two-phase flow parameter detection method based on porous throttling and acoustic emission technology, is characterized in that, comprises the steps: a. Build a two-phase flow parameter detection device based on porous throttling and acoustic emission technology; The two-phase flow parameter detection device based on porous throttling and acoustic emission technology includes a porous balance flowmeter, a differential pressure transmitter, an acoustic emission probe, a data acquisition unit and a data processing unit; The porous balance flowmeter includes a front straight pipe section, a rear straight pipe section, and a porous orifice plate arranged between the front straight pipe section and the rear straight pipe section; the diameter of the porous orifice plate is larger than the diameter of the two straight pipe sections, A number of throttle holes are opened on the perforated orifice plate at positions opposite to the two sections of straight pipe lumens, and a number of through holes are uniformly opened along the circumference on the edge of the perforated orifice plate extending out of the two sections of straight pipes; The acoustic emission probe is correspondingly placed in the through hole on the edge of the perforated orifice plate; a pressure taking hole is opened on the side walls of the front straight pipe section and the rear straight pipe section, and the differential pressure transmitter is connected to the two take-off holes. Press holes are connected; b. Make the two-phase flow flow in from the front straight pipe section, and flow into the back straight pipe section after passing through the orifice on the perforated orifice plate; c. The differential pressure transmitter detects the pressure difference signal in the front straight pipe section and the rear straight pipe section, and at the same time, the acoustic emission probe detects the flow sound signal of the fluid; d. The data acquisition unit collects the signals detected by the differential pressure transmitter and the acoustic emission probe, and sends the collected signals to the data processing unit; e. The data processing unit receives the signal sent by the data acquisition unit, and processes and calculates the received flow acoustic signal and pressure difference signal of the two-phase flow, thereby obtaining the flow rate and phase holdup of the two-phase flow; Step e is as follows: The data processing unit obtains the characteristic frequency band according to the flow acoustic signal of the two-phase flow, and extracts the energy characteristic value E in the characteristic frequency band, and calculates the gas phase volume fraction β _g according to the energy characteristic value E in combination with the following formula: β _g = 0.44214ln(E+663.0423)-2.87159 The data processing unit calculates the total mass flow W _m of the two-phase flow according to the following formula according to the gas phase volume fraction β _g and the pressure difference between the front and rear straight pipe sections:

In the above formula, ε is the expansion coefficient of the two-phase flow, C is the outflow coefficient, D is the inner diameter of the front straight pipe section and the rear straight pipe section, β is the equivalent diameter ratio of the perforated orifice plate, and Δp _tp is the two-phase flow in the two-phase flow. The pressure difference in each straight pipe section, x is the mass gas content, x can be obtained from the gas volume content β _g , ρ _g is the density of the gas phase fluid, ρ _l is the density of the liquid fluid; The formula for calculating the equivalent diameter ratio β of the porous plate is as follows:

In the above formula, d is the diameter of the orifice, D is the inner diameter of the front straight pipe section and the rear straight pipe section, and N is the number of the orifice. 2. the two-phase flow parameter detection method based on porous throttling and acoustic emission technology according to claim 1, is characterized in that, in step a, the inner diameter of the front straight pipe section and the back straight pipe section is D, and the inner diameter of the front straight pipe section is D. The length L ₁ satisfies: L ₁ ≥D, the length L ₂ of the rear straight pipe section satisfies: L ₂ ≥ 1.5D; and the distances between the two pressure-taking holes and the porous orifice plate are both D. 3. The two-phase flow parameter detection method based on porous throttling and acoustic emission technology according to claim 1, wherein in step a, the throttling holes on the porous orifice plate are evenly distributed on the porous orifice plate. The center is on one or more concentric circles; and each orifice has a front chamfer of 45° and a rear chamfer of 45°. 4. the two-phase flow parameter detection method based on porous throttling and acoustic emission technology according to claim 1, is characterized in that, in step a, both ends of front straight pipe section and rear straight pipe section are provided with flange plate , the porous orifice plate is connected with the front straight pipe section and the rear straight pipe section through the flanges adjacent to it on the front straight pipe section and the rear straight pipe section; the outer edge of the porous orifice plate protrudes to the adjacent The outer edge of the flange plate is outside, and the through hole for placing the acoustic emission probe is opened on the edge of the porous orifice plate extending to the outside of the flange plate; the flange plate and the porous orifice plate are fixedly connected by bolts. 5. the two-phase flow parameter detection method based on porous throttling and acoustic emission technology according to claim 1, it is characterized in that, in step a, open around each through hole on described porous orifice plate and be located in through hole The two small holes on the diameter extension line can be used to fix the acoustic emission probe in the through hole through the nylon cable ties passing through the two small holes.

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