Gas-water two-phase flow ultrasonic measurement method and device

Abstract

The present invention discloses a method for ultrasonic measurement of gas-water two-phase flow, comprising: performing in-pipe phase separation on the gas-water two-phase flow in the measurement pipeline, obtaining the gas-water two-phase separation cross-sectional content by using an ultrasonic echo reflection method, measuring the true flow velocity of the water phase by using a continuous wave ultrasonic Doppler method, obtaining the flow velocity of the gas-water interface wave by using an ultrasonic cross-correlation method, calculating the true flow velocity of the gas phase by combining a dual-fluid model and the above-obtained parameters, and on this basis, achieving measurement of the phase separation apparent flow velocity and volume flow rate. The present invention also provides an ultrasonic measurement device utilizing the above-mentioned method. The present invention combines in-pipe phase separation, a dual-fluid model, and ultrasonic measurement, which can effectively solve the problem of the influence of flow type on ultrasonic measurement and achieve synchronous measurement of multiple parameters such as phase content, flow velocity, and flow rate.

Description

Technical Field

[0001] The present invention relates to the field of fluid measurement technology, and in particular to a gas-water two-phase flow ultrasonic measurement method and device based on a dual-fluid model combined with in-pipe phase separation. Background Art

[0002] Compared with single-phase flow, two-phase flow has a random phase interface shape and phase distribution. Due to its stability or intermittency, the flow pattern is variable and the parameters are complex, including the flow rate of each phase, phase content, flow velocity, phase distribution, etc., and the accurate measurement of multiple parameters of two-phase flow still remains difficult. Currently, many researchers have conducted research on gas-water two-phase flow, and its flow parameter measurement methods are mainly divided into two categories: direct method and indirect method. The direct method usually uses traditional single-phase flow instruments. This type of instrument performs well when detecting mixed flow, but has large errors when applied to other flow types. Indirect methods require establishing a relationship between the measured value and the object parameter through calculation, such as electrical method, ray method, microwave method, optical method and ultrasonic method.

[0003] Ultrasonic methods offer advantages over other methods. Both ultrasonic and electrical methods offer fast response, low cost, and easy maintenance. Ultrasonic methods are not affected by conductivity. Ultrasonic and microwave methods are non-invasive, radiation-free, and highly stable, resulting in lower costs. Ultrasonic and optical methods offer convenience, speed, contactlessness, and no impact on the measured medium. Ultrasonic methods offer superior penetration and directivity, capable of penetrating optically opaque liquids, covering a wide concentration range, and providing a safer and more stable system. However, ultrasonic methods also have limitations in their application to two-phase flow parameter measurement. Studies have found that varying phase holdup, discrete phase particle size, and position can affect ultrasonic measurement results, leading to nonlinear responses and low resolution. Currently, multi-parameter measurement in two-phase flow using ultrasonic methods mostly employs multimodal detection schemes. These approaches first use specialized flow pattern monitoring devices to determine the two-phase flow pattern, and then develop separate ultrasonic measurement models based on the different flow regimes of the multiphase flow. This results in complex measurement systems and high maintenance costs.

[0004] Therefore, technicians in this field are committed to developing an ultrasonic measurement method and device for gas-water two-phase flow. Combining phase separation in the pipe, a dual-fluid model and ultrasonic measurement can effectively solve the problem of the influence of flow type on ultrasonic measurement and realize the synchronous measurement of multiple parameters such as phase content, flow velocity and flow rate. Summary of the Invention

[0005] In light of the aforementioned shortcomings of the prior art, the present invention provides a method and device for ultrasonic measurement of gas-water two-phase flow. This method combines in-pipe phase separation with ultrasonic measurement. Through in-pipe phase separation, different inlet flow patterns are converted into a flow pattern similar to a "gas-water annular flow," effectively addressing the impact of flow patterns on ultrasonic measurement. The device primarily comprises a phase separation assembly and an ultrasonic measurement assembly. The phase separation assembly comprises a multi-stage swirl structure, installed upstream of the measurement pipeline and downstream of the ultrasonic measurement assembly. The ultrasonic measurement assembly comprises an ultrasonic probe and an ultrasonic transmitter-receiver, with the ultrasonic probe fixed to one axial side of the measurement pipeline.

[0006] The present invention is based on a dual-fluid model and in-pipe phase separation, combined with three ultrasonic measurement methods, to measure the fluid after phase separation of the gas-water two-phase flow, and realize the synchronous measurement of multiple parameters such as phase content, flow velocity and flow rate. The main steps are as follows: First, the in-pipe phase separation is combined with the ultrasonic echo reflection method to realize the measurement of the liquid film thickness of the gas-water two-phase flow, and then obtain the gas-water phase cross-sectional content information; second, the in-pipe phase separation is combined with the continuous wave ultrasonic Doppler method to realize the measurement of the true flow velocity of the water phase of the gas-water two-phase flow; third, the in-pipe phase separation is combined with the ultrasonic cross-correlation method to obtain the transit time of the gas-water interface fluctuation signal, and realize the flow velocity measurement of the gas-water two-phase flow interface wave; fourth, based on the dual-fluid model, the friction coefficient between the gas and water phases is introduced to further calculate the true flow velocity of the gas phase; fifth, based on the parameter information obtained by the above calculations, the gas-water two-phase flow phase apparent flow velocity, flow rate, total apparent flow velocity and total flow rate are measured.

[0007] To achieve the above objectives, the present invention provides a gas-water two-phase flow ultrasonic measurement method based on a two-fluid model combined with in-pipe phase separation, comprising:

[0008] Step 1: Separate the gas-water two-phase flow flowing through the measuring pipe in the pipe;

[0009] Step 2: Using an ultrasonic probe installed on the measuring pipe and combining it with ultrasonic echo reflection method, measure the average liquid film thickness of the gas-water two-phase flow after phase separation. And based on the average liquid film thickness Calculate the water phase cross-sectional content α w and gas phase cross-sectional fraction α g ;

[0010] Step 3: Using another set of single-transmitter and single-receiver ultrasonic probes installed in the measuring pipe, combined with the continuous wave ultrasonic Doppler method, the real flow velocity u of the water phase in the gas-water two-phase flow is measured. w ;

[0011] Step 4: Using two self-transmitting and self-receiving ultrasonic probes installed in the measuring pipe, combined with the ultrasonic cross-correlation method, the velocity u of the air-water interface wave is obtained. i, wherein the distance between the two ultrasonic probes is L;

[0012] Step 5: Based on the two-fluid model, use the gas-water phase cross-section fraction α w and α g , the actual flow rate of the water phase u w , the velocity u of the air-water interface wave i , calculate the true gas flow rate u g ;

[0013] Step 6: Based on the actual flow rate u of the water phase w , the gas phase true flow rate u g , the gas-water two-phase flow phase separation cross-section fraction α w and α g , calculate the gas-water phase apparent velocity J g 、J w and the total apparent velocity J of the two-phase flow;

[0014] Step 7: Based on the actual flow rate u of the water phase w , the gas phase true flow rate u g , and the cross-sectional area A occupied by the gas-water two-phase flow in the measuring pipe w and A g , calculate the gas-water phase volume flow rate Q g , Q w And the total volume flow rate Q of the two-phase flow.

[0015] Furthermore, the step 2 includes:

[0016] Step 2.1: Calculate the dielectric characteristic acoustic impedance using Equation 1:

[0017] Z=ρc Formula 1

[0018] Where Z represents the characteristic acoustic impedance of the medium, ρ represents the density of the medium, and c represents the sound velocity of the medium:

[0019] Step 2.2: Measure the liquid film thickness h using Formula 2:

[0020]

[0021] Where t represents the time it takes for the self-transmitting and self-receiving ultrasonic probe to receive the pulse echo, c w It represents the propagation speed of ultrasound in aqueous medium;

[0022] Step 2.3: According to formula 3, the gas-water two-phase flow in the measuring pipe is sampled for a continuous period of time, and the measured liquid film thickness h is averaged to calculate the average liquid film thickness

[0023]

[0024] Where N represents the number of sampling points;

[0025] Step 2.4: Calculate the cross-sectional area A occupied by the water phase in the measuring pipe according to formula 4 w :

[0026]

[0027] Where A represents the cross-sectional area of ​​the measuring pipe, A g represents the cross-sectional area occupied by the gas phase, and D represents the inner diameter of the measuring pipe;

[0028] Step 2.5: Calculate the instantaneous water phase cross-sectional fraction α of the gas-water two-phase flow in the measuring pipe according to formula 5: w :

[0029]

[0030] Step 2.6: Calculate the gas phase cross-sectional fraction α according to formula 6 g :

[0031]

[0032] Furthermore, the step three includes:

[0033] The average Doppler frequency shift is obtained by analyzing the spectrum of the ultrasonic signal at the receiving end Combined with the speed of sound in water c w , calculate the water phase true velocity u according to formula 7 w :

[0034]

[0035] Where f0 represents the center frequency of the ultrasonic wave emitted by the probe, and θ represents the angle between the incident sound wave and the pipe wall on the probe side.

[0036] Furthermore, the step 4 includes:

[0037] The two self-transmitting and self-receiving ultrasonic probes transmit ultrasonic signals simultaneously;

[0038] When the correlation coefficient R x,y When the maximum value is reached, the cross-correlation velocity v is obtained according to Formula 8 from the delay time σ of the two ultrasonic probes receiving the signal and the center distance L:

[0039]

[0040] Where, σ is the delay time between the two signals, and L is the center distance between the two ultrasonic probes;

[0041] Among them, the correlation coefficient R x,y Determined according to formula 9:

[0042]

[0043] Where Δt is the measurement time, and τ represents the delay time of the upstream and downstream receiving signals;

[0044] The cross-correlation velocity v is equivalent to the flow velocity u of the air-water interface wave i .

[0045] Furthermore, the step five includes:

[0046] The gas column momentum balance equation of the two-fluid model is shown in Formula 10:

[0047]

[0048] The liquid film momentum balance equation of the two-fluid model is shown in Formula 11:

[0049]

[0050] Combining the above formula 10 and the above formula 11, assuming that the pressure drop gradients of the gas and water phases are equal, we get formula 12:

[0051] τ i S i A-τ w S w A g -A w A g (ρ w -ρ g )gsinβ=0 Formula 12

[0052] Where β is the inclination angle. For vertical tube, β = 90°, ρ g is the gas phase density, ρ w is the density of the water phase, g is the acceleration due to gravity;

[0053] Let β = 90° and the cross-sectional area occupied by the gas phase be A. w , cross-sectional area occupied by water phase A g , the gas phase cross-sectional content α g , the water phase cross-sectional content α w , water phase wet perimeter S w =πD, shear force between water phase and wall Air-water interface length Air-water interface shear force τ i =0.5f i ρ g (u i -uw ) 2 Substituting into Formula 12, we obtain Formula 13:

[0054]

[0055] Among them, f w is the friction coefficient of the water phase tube wall, which is expressed by formula 14:

[0056]

[0057] Where μ w is the viscosity of the water phase;

[0058] Friction coefficient between air and water phases f i Expressed by Formula 15:

[0059]

[0060] Gas phase Reynolds number Re g Expressed by formula 16:

[0061]

[0062] Where μ g is the gas phase viscosity;

[0063] The actual flow rate of the water phase u w , the velocity u of the air-water interface wave i , the water phase tube wall friction coefficient f w , the friction coefficient between the air and water phases f i , the gas phase Reynolds number Re g , substitute into formula 13 to obtain formula 17, and calculate the gas phase true flow rate u g :

[0064]

[0065] Furthermore, the step six includes:

[0066] Calculate the superficial velocity J of the gas phase according to formula 18 g :

[0067] J g =u g a g Formula 18

[0068] The superficial flow rate J of the water phase is calculated according to formula 19 w :

[0069] J w =u w α w Formula 19

[0070] The total apparent velocity J of the gas-water two-phase flow is calculated according to formula 20:

[0071] J=J g +J w Formula 20

[0072] Furthermore, the step seven includes:

[0073] The volume flow rate Q of the gas phase is calculated according to formula 21 g :

[0074] Q g =A g u g Formula 21

[0075] The volume flow rate Q of the water phase is calculated according to formula 22 w :

[0076] Q w =A w u w Formula 22

[0077] The total volume flow rate Q of the gas-water two-phase flow is calculated according to formula 23:

[0078] Q=Q g +Q w Formula 23

[0079] The present invention also provides an ultrasonic measuring device using the above-mentioned gas-water two-phase flow ultrasonic measuring method, comprising:

[0080] a measuring pipe through which a gas-water two-phase flow flows;

[0081] a phase separation component, arranged on the measuring pipe;

[0082] an ultrasonic measurement component, arranged on the measurement pipe;

[0083] Wherein, the phase separation component includes a vane swirler, and at least one vane swirler is provided upstream of the measuring pipe and upstream of the ultrasonic measuring component;

[0084] The ultrasonic measurement assembly includes an ultrasonic signal transmitter and receiver, and a plurality of ultrasonic probes electrically connected to the ultrasonic signal transmitter and receiver, wherein the ultrasonic probes are arranged on the measuring pipe, including two single crystal probes and two wedge probes, the two single crystal probes are self-transmitting and self-receiving probes, and the axial spacing along the measuring pipe is 1-3 times the inner diameter of the measuring pipe; the two wedge probes are single-transmitting and single-receiving probes, and are arranged closely on one axial side of the measuring pipe.

[0085] Furthermore, the phase separation component further comprises a orifice plate, and the orifice plate is arranged upstream of the vane swirler in the ultrasonic measurement component.

[0086] Furthermore, the phase separation component further includes a blade-type swirler arranged downstream of the ultrasonic measurement component.

[0087] The gas-water two-phase flow ultrasonic measurement method and device provided by the present invention based on the combination of a dual-fluid model and in-pipe phase separation have the following advantageous technical effects:

[0088] 1. The present invention combines in-tube phase separation with ultrasonic method. Through in-tube phase separation, different inlet flow patterns are converted into gas column-liquid film flow patterns, which can effectively solve the measurement difficulties caused by flow pattern problems such as different phase contents, discrete phase particle size and position, and large bubbles. The arrangement of ultrasonic probes solves the problem of simultaneous multi-parameter measurement using ultrasonic method.

[0089] 2. The present invention utilizes a multi-stage phase separation component. The blade-type cyclone in the first-stage cyclone structure is the core of the phase separation component. After phase separation, the four different flow patterns of the gas-water two-phase flow are separated. Small bubbles in the discrete phase form a continuous central gas column, while the water phase forms a continuous water ring surrounding the gas column. Long bubbles form a rotating annular flow with a thicker liquid film, essentially achieving phase separation within the tube. However, the stable phase section for large bubbles is relatively short. A perforated plate is added to the second-stage cyclone structure as a filter element. Large bubbles, such as air bubbles and irregular lumps of gas in the gas-water mixture, are reduced or decomposed into small bubbles before entering the cyclone. This increases the length of the stable phase section of the post-cyclone gas column. The third-stage cyclone structure not only increases upstream pressure, strengthens the gas column, and forms a stable gas column, but also acts as a rectifier, helping to improve the accuracy of multi-parameter measurements performed by ultrasonic measurement devices. The first, second, or third-stage cyclone structure can be selected to meet various application requirements, demonstrating universal applicability.

[0090] 3. The present invention is based on a dual-fluid model and phase separation in the pipe, combined with three ultrasonic measurement methods, to achieve simultaneous measurement of multiple parameters such as phase holdup, flow velocity and flow rate.

[0091] The concept, specific structure and technical effects of the present invention will be further described below in conjunction with the accompanying drawings to fully understand the purpose, characteristics and effects of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0092] Figure 1 It is a schematic structural diagram of the ultrasonic measuring device of the present invention;

[0093] Figure 2 It is a schematic diagram of the structure of the ultrasonic measurement component;

[0094] Figure 3 This is a schematic diagram of the first installation method of the ultrasonic measurement component;

[0095] Figure 4 This is a schematic diagram of the second installation method of the ultrasonic measurement component;

[0096] Figure 5 It is a schematic diagram of the process of measuring the true velocity of the gas phase based on the two-fluid model.

[0097] Among them, 10-measuring pipe, 11-plane, 12-square coupling block, 20-phase separation component, 21-cyclone, 22-orifice plate, 30-ultrasonic measurement component, 31-ultrasonic signal transmitter and receiver, 32-first single crystal probe, 33-second single crystal probe, 34-first wedge probe, 35-second wedge probe, 40-gas-water two-phase flow. DETAILED DESCRIPTION

[0098] The following describes several preferred embodiments of the present invention with reference to the accompanying drawings to make its technical content clearer and easier to understand. The present invention can be embodied in many different forms of embodiments, and the scope of protection of the present invention is not limited to the embodiments mentioned herein.

[0099] In the drawings, components with identical structures are denoted by the same reference numerals, and components with similar structures or functions are denoted by similar reference numerals. The size and thickness of each component shown in the drawings are arbitrary and are not limited by the present invention. For clarity, the thickness of components in some places in the drawings is exaggerated.

[0100] like Figure 1 As shown, the present invention provides an ultrasonic measurement device for gas-water two-phase flow based on a dual-fluid model combined with phase separation in a pipe, comprising a measuring pipe 10 and a phase separation component 20 and an ultrasonic measurement component 30 arranged on the measuring pipe 10. Gas-water two-phase flow 40 flows through the measuring pipe 10, and the flow direction is X. The phase separation component 20 includes at least one swirl structure, which is installed upstream of the measuring pipe 10 and upstream of the ultrasonic measurement component 30. The phase separation component 20 converts the flow pattern of the gas-water two-phase flow 40 in the measuring pipe 10 into a gas column-liquid film flow pattern. Figure 2As shown, the ultrasonic measurement component 30 is arranged on one side of the measuring pipe 10, including an ultrasonic signal transmitter and receiver 31 and a plurality of ultrasonic probes, and the ultrasonic probes are electrically connected to the ultrasonic signal transmitter and receiver 31. The ultrasonic probe is arranged on the measuring pipe 10, including two single crystal probes (i.e., a first single crystal probe 32 and a second single crystal probe 33) and two wedge probes (i.e., a first wedge probe 34 and a second wedge probe 35), wherein the single crystal probes 32 and 33 are self-transmitting and self-receiving probes, which are arranged on the same axial side of the measuring pipe 10, with a spacing of 1-3 times the inner diameter of the measuring pipe 10; the two wedge probes 34 and 35 are one-transmitting and one-receiving probes, i.e., the wedge probe 34 transmits ultrasonic signals, and the wedge probe 35 receives ultrasonic signals. The two wedge probes 34 and 35 are arranged closely on the same axial side of the measuring pipe 10. The ultrasonic signal transmitter and receiver 31 includes multiple channels, which can be triggered synchronously. For example, as Figure 2 As shown, the ultrasonic signal transmitter and receiver 31 includes three channels.

[0101] There are many ways to install the ultrasonic probe, e.g. Figure 3 As shown, the surface of one side of the measuring pipe 10 downstream of the phase separation component 20 is flattened to form a plane 11, and then the fixed probe is installed on the plane 11. This installation method allows the probe to be installed close to the flat pipe wall, avoiding measurement errors caused by round pipe installation. Figure 4 As shown, a square coupling block 12 is installed on the measurement pipe 10 downstream of the phase separation assembly 20 and secured to the pipe with fasteners. The probe is then mounted and secured to the square coupling block 12. Connecting the probe to the pipe wall via the square coupling block 12 also avoids measurement errors associated with circular pipe installation. It should be understood that other installation methods that effectively reduce ultrasonic measurement errors can also be used in the present invention.

[0102] The phase separation component 20 of the present invention can be provided with a single-stage or multi-stage cyclone structure according to different actual needs, and different cyclone structures can also be selected according to different needs. The details are as follows:

[0103] In some embodiments, as Figure 1 As shown in (a), the phase separation component 20 includes a primary cyclone structure, which is composed of a vane cyclone 21 and is installed upstream of the measuring pipe 10 and the ultrasonic measuring component 30.

[0104] In some embodiments, as Figure 1 As shown in Figure 2 (b), the phase separation assembly 20 comprises a two-stage cyclone structure, specifically, an orifice plate 22 and a vane cyclone 21. The orifice plate 22 and vane cyclone 21 are installed sequentially along the flow direction, both upstream of the measurement pipeline 10 and the ultrasonic measurement assembly 30. Large bubbles, such as air bubbles and irregular gas masses, can be found in the gas-water two-phase flow. When they pass through the orifice plate 22, they rapidly shrink or rupture, forming a bubbly flow that enters the vane cyclone 21.

[0105] In some embodiments, as Figure 1 As shown in (c), the phase separation component 20 includes a three-stage cyclone structure, specifically, an orifice plate 22 and two vane cyclones 21, which are installed in series on the measuring pipe 10 along the flow direction and are both located upstream of the measuring pipe 10 and the ultrasonic measurement component 30.

[0106] In some embodiments, as Figure 1 As shown in Figure (d), the phase separation assembly 20 comprises a three-stage cyclone structure, specifically, an orifice plate 22 and two vane cyclones 21. These are installed in series on the measuring pipe 10 along the flow direction. The orifice plate 22 and one vane cyclone 21 are located upstream of the measuring pipe 10 and the ultrasonic measurement assembly 30, while the other vane cyclone 21 is located downstream of the ultrasonic measurement assembly 30. After the gas-water two-phase flow is separated by the upstream orifice plate 22 and cyclone 21, the downstream cyclone 21 increases the upstream pressure, forming a more stable gas column.

[0107] The present invention also provides a method for ultrasonically measuring gas-water two-phase flow using the ultrasonic measuring device, comprising the following steps:

[0108] Step 1: Separate the gas-water two-phase flow 40 flowing through the measuring pipe 10 in the pipe;

[0109] Step 2: Using the ultrasonic probe 32 and / or 33 installed on the measuring pipe 10, combined with the ultrasonic echo reflection method, measure the average liquid film thickness of the gas-water two-phase flow after phase separation. Based on the average film thickness Calculate the water phase cross-sectional content α w and gas phase cross-sectional fraction α g The measurement can be performed using either of the two single crystal probes 32 and 33 or using both of the two single crystal probes 32 and 33 simultaneously.

[0110] Step 3: Use another set of single-transmitter single-receiver ultrasonic probes 34 and 35 installed in the measuring pipe 10, combined with the continuous wave ultrasonic Doppler method, to measure the true flow velocity u of the water phase in the gas-water two-phase flow. w ;

[0111] Step 4: Using two self-transmitting and self-receiving ultrasonic probes 32 and 33 installed in the measuring pipe 10, combined with the ultrasonic cross-correlation method, the velocity u of the air-water interface wave is obtained. i , where the distance between the two ultrasonic probes is L;

[0112] Step 5: Based on the two-fluid model, the gas-water two-phase flow phase fraction α in step 2 w and α g, the actual flow rate of the water phase in step 3 u w , the velocity u of the air-water interface wave in step 4 i , calculate the true gas flow rate u g ;

[0113] Step 6: Based on the actual flow rate u of the water phase w , gas phase true flow rate u g , gas-water two-phase flow phase separation cross-section fraction α w and α g , calculate the phase separation apparent flow rate J g 、J w and the total apparent velocity J of the two-phase flow;

[0114] Step 7: Based on the actual flow rate u of the water phase w , gas phase true flow rate u g , and the cross-sectional area A of the gas-water two-phase flow in the measuring pipe 10 w and A g , calculate the gas-water phase volume flow rate Q g , Q w And the total volume flow rate Q of the two-phase flow.

[0115] The phase separation in the tube in step 1 can be performed using a phase separation assembly 20 as shown in the figure. After the phase separation, the gas-water two-phase flow can form a gas column-liquid film flow pattern.

[0116] Step 2 combines the phase separation in the pipe with the ultrasonic echo reflection method to obtain the gas-water phase cross-section holdup information, as follows:

[0117] Step 2.1: The self-transmitting and self-receiving single crystal probe 32 and / or 33 installed on the measuring pipe 10 vertically transmits ultrasonic signals. According to the ultrasonic echo reflection method, when the single crystal probe transmits ultrasonic signals, the ultrasonic waves first propagate in the water phase medium. Since the characteristic acoustic impedance of the gas and water media is different, the characteristic acoustic impedance of the medium can be calculated using formula (1):

[0118] Z=ρc (1)

[0119] Where Z represents the characteristic acoustic impedance of the medium, ρ represents the density of the medium, and c represents the sound velocity of the medium:

[0120] Step 2.2: When the single crystal probe 32 transmits an ultrasonic wave that propagates to the gas-water interface, the transmitted acoustic wave signal is very weak, and most of the signal is reflected by the gas-water interface and received by the single crystal probe 33. According to formula (2), the time it takes for the probe to receive the pulse echo and the propagation speed of the ultrasonic wave in the aqueous medium can be used to measure the thickness of the liquid film after the gas-water two-phase flow is separated:

[0121]

[0122] Where h is the thickness of the liquid film, t is the time it takes for the ultrasonic probe to receive the pulse echo, and c w Indicates the propagation speed of ultrasound in aqueous media;

[0123] Step 2.3: According to formula (3), the gas-water two-phase flow 40 in the measuring pipe 10 is sampled for a continuous period of time, and the measured liquid film thickness h is averaged to calculate the average liquid film thickness

[0124]

[0125] Where N represents the number of sampling points.

[0126] Step 2.4: Calculate the cross-sectional area A occupied by the water phase in the measuring pipe 10 according to formula (4): w :

[0127]

[0128] Wherein, A represents the cross-sectional area of ​​the measuring pipe 10, A g represents the cross-sectional area occupied by the gas phase, and D represents the inner diameter of the measuring pipe 10;

[0129] Step 2.5: Calculate the instantaneous water phase cross-sectional fraction α of the gas-water two-phase flow 40 in the measuring pipe 10 according to formula (5): w :

[0130]

[0131] Step 2.6: Calculate the gas phase cross-sectional fraction α according to formula (6): g :

[0132]

[0133] Step three combines the phase separation in the pipe and the continuous wave ultrasonic Doppler method to measure the true flow velocity of the water phase of the gas-water two-phase flow. The gas-water two-phase flow after the phase separation in the pipe flows through the ultrasonic measurement component 30, and two wedge probes 34 and 35 are installed on the same side of the vertical measurement pipe 10. According to the continuous wave ultrasonic Doppler method, the probe 34 transmits an ultrasonic signal, and the ultrasonic signal with Doppler frequency shift information reflected by the gas-water interface is received by the probe 35 on the same side. The measurement space includes the entire water phase cross-section on the probe side. The average Doppler frequency shift is obtained by analyzing the spectrum of the ultrasonic signal at the receiving end. Combined with the speed of sound in water c w , calculate the true velocity of the water phase according to formula (7):

[0134]

[0135] Among them, uw represents the true velocity of the water phase, f0 represents the ultrasonic emission frequency, and θ represents the angle between the incident sound wave and the pipe wall on the probe side.

[0136] Step 4 combines the phase separation in the pipe with the ultrasonic cross-correlation method to realize the flow velocity measurement of the interface wave of the gas-water two-phase flow. The gas-water two-phase flow after the phase separation in the pipe flows through the ultrasonic measurement component 30, and two self-emitting and self-receiving single crystal probes 32 and 33 with a fixed spacing are installed on the same side of the vertical measurement pipe 10. The spacing is 1-3 times the inner diameter of the pipe. Probe 32 and probe 33 simultaneously transmit ultrasonic signals, which are received by them after being reflected by the gas-water interface. According to the ultrasonic cross-correlation method, when the correlation coefficient R x,y When the maximum value is reached, according to formula (8), the cross-correlation velocity v can be obtained from the delay time σ (i.e., the time for the air-water interface fluctuation signal to flow from the upstream probe to the downstream probe) of the two fixed-distance self-transmitting and self-receiving probes 32 and 33 receiving the signal and the center distance L of the two probes (i.e., the liquid film flow distance L):

[0137]

[0138] Correlation coefficient R x,y The expression of is shown in formula (9):

[0139]

[0140] Where Δt is the measurement time, σ is the delay time between the two signals, and τ represents the delay time between the upstream and downstream receiving signals. For a single-phase fluid in a circular pipe, the velocity is the highest closer to the center of the pipe and the velocity decreases closer to the pipe wall. The velocity distribution of a two-phase flow is complex, and the cross-correlation velocity v is theoretically the velocity u of the gas-water interface wave. i .

[0141] Step 5 is based on the two-fluid model and combines the phase content information detected by the ultrasonic echo reflection method and the real water phase velocity u obtained by the continuous wave ultrasonic Doppler method. w The velocity u of the air-water interface wave obtained by ultrasonic cross-correlation method i , introducing the friction coefficient f between air and water phases i , further calculate the true flow rate u of the gas phase g After the phase separation in the tube, the gas-water two-phase flow forms a flow pattern similar to the "gas-water annular flow". This flow pattern is in the form of a gas column-liquid film, the droplets entrained in the gas phase are negligible, the gas-water interface is smooth, the liquid film thickness is uniform, and the surface tension is negligible. Therefore, based on the two-fluid model, the present invention determines the corresponding flow pattern structure equation for the structural characteristics of the above-mentioned "gas-water annular flow" flow pattern to close the hydraulic model and solve the unknown parameters. Figure 5 , the specific calculation process is as follows:

[0142] The five basic equations of the two-fluid model include the gas-water continuity equation, the gas-water momentum conservation equation, and the gas state equation. The "gas-water annular flow" pattern requires consideration of the momentum balance of the gas column and the liquid film.

[0143] The momentum balance of the air column is shown in formula (10):

[0144]

[0145] The liquid film momentum balance is shown in formula (11):

[0146]

[0147] Assuming that the pressure drop gradients of the gas and water phases are equal, combining equations (10) and (11) yields:

[0148] τ i S i A-τ w S w A g -A w A g (ρ w -ρ g )gsinβ=0 (12)

[0149] Where β is the inclination angle. For vertical tube, β = 90°, ρ g is the gas phase density, ρ w is the density of the water phase, and g is the acceleration due to gravity.

[0150] According to step 2, the phase cross-sectional area A of the gas-water two-phase flow is obtained w and A g , and the gas-water phase cross-section fraction α g and α w ; According to step 3, the actual flow rate of the water phase u is calculated w . Set β = 90°, water phase wetted area S w =πD, shear force between water phase and wall Air-water interface length Air-water interface shear force τ i =0.5f i ρ g (u i -u w ) 2 Substituting the above-obtained parameters into formula 12, we get formula 13:

[0151]

[0152] Among them, f w is the friction coefficient of the water phase tube wall, calculated according to formula (14):

[0153]

[0154] Where μ w is the viscosity of the water phase.

[0155] Friction coefficient between air and water phases f i It is expressed by formula (15):

[0156]

[0157] Where, Re g is the gas phase Reynolds number, expressed by formula (16):

[0158]

[0159] Where μ g is the gas phase viscosity.

[0160] The actual flow rate of the water phase u w , velocity u of air-water interface wave i , water phase tube wall friction coefficient f w , friction coefficient between air and water phases f i and gas phase Reynolds number Re g Substituting into formula 13, we can get the true gas flow rate u g , as shown in formula (17):

[0161]

[0162] The specific algorithm process is as follows Figure 5 shown.

[0163] Step 6: The gas-water two-phase flow separation velocity J can be calculated according to formulas (18)-(20): g 、J w And the total apparent velocity J of the two-phase flow:

[0164] J g =u g α g (18)

[0165] J w =u w α w (19)

[0166] J=J g +J w (20)

[0167] Step 7: According to formulas (21)-(23), calculate the phase separation volume flow rate Q of the gas-water two-phase flow g , Q w And the total volume flow rate Q of the two-phase flow:

[0168] Q g =A g u g (twenty one)

[0169] Q w =A w u w (twenty two)

[0170] Q=Q g +Q w (twenty three)

[0171] In the present invention, the parameters in steps 2 to 7 can be measured synchronously.

[0172] The preferred embodiments of the present invention have been described in detail above. It should be understood that numerous modifications and variations based on the concepts of the present invention are possible without inventive effort by those skilled in the art. Therefore, any technical solution that can be derived by one skilled in the art through logical analysis, reasoning, or limited experimentation based on the concepts of the present invention and the prior art should be within the scope of protection defined by the claims.

Claims

1. A method for ultrasonic measurement of gas-water two-phase flow, characterized in that: include: Step 1: Separate the gas-water two-phase flow flowing through the measuring pipe in the pipe; Step 2: Using an ultrasonic probe installed on the measuring pipe and combining it with ultrasonic echo reflection method, measure the average liquid film thickness of the gas-water two-phase flow after phase separation. ; and based on the average liquid film thickness , the water phase cross-sectional content is calculated and gas phase cross-sectional fraction ; Step 3: Using another set of single-transmitter single-receiver ultrasonic probes installed in the measuring pipe, combined with continuous wave ultrasonic Doppler method, measure the true flow velocity of the water phase in the gas-water two-phase flow ; Step 4: Using two self-transmitting and self-receiving ultrasonic probes installed in the measuring pipe, combined with ultrasonic cross-correlation method, the velocity of the air-water interface wave is obtained. , wherein the distance between the two ultrasonic probes is L ; Step 5: Based on the two-fluid model, use the gas-water phase cross-section fraction and , the actual flow rate of the water phase , the velocity of the air-water interface wave , calculate the true gas flow rate , the gas column momentum balance of the two-fluid model is shown in Formula 10: Formula 10 The liquid film momentum balance equation of the two-fluid model is shown in Formula 11: Formula 11 Where, β is the tilt angle, is the gas phase density, is the density of the water phase, is the acceleration due to gravity, is the cross-sectional area occupied by the water phase, is the cross-sectional area occupied by the gas phase, It is a water phase wet periphery. is the wall shear force, is the perimeter of the air-water interface, is the shear force at the air-water interface; Step 6: Based on the actual flow rate of the water phase , the actual gas flow rate , the gas-water two-phase flow phase cross-section fraction and , calculate the gas-water phase apparent velocity 、 and the total superficial velocity of the two-phase flow ; Step 7: Based on the actual flow rate of the water phase , the actual gas flow rate , and the cross-sectional area occupied by the gas-water two-phase flow in the measuring pipe and , calculate the gas-water phase volume flow rate 、 and the total volume flow rate of the two-phase flow .

2. The gas-water two-phase flow ultrasonic measurement method according to claim 1, characterized in that: The second step includes: Step 2.1: Calculate the dielectric characteristic acoustic impedance using Equation 1: Formula 1 Where Z represents the characteristic acoustic impedance of the medium, ρ represents the density of the medium, c represents the medium sound velocity; Step 2.2: Measure the thickness of the liquid film using Formula 2 h : Formula 2 Where, It indicates the time when the self-transmitting and self-receiving ultrasonic probe receives the pulse echo. It represents the propagation speed of ultrasound in aqueous medium; Step 2.3: According to formula 3, the gas-water two-phase flow in the measuring pipe is sampled for a continuous period of time, and the liquid film thickness obtained by the measurement is h Average, calculate the average liquid film thickness : Formula 3 Where N represents the number of sampling points; Step 2.4: Calculate the cross-sectional area occupied by the water phase in the measuring pipe according to formula 4 : Formula 4 Where, represents the cross-sectional area of ​​the measuring pipe, represents the cross-sectional area occupied by the gas phase, Indicates the inner diameter of the measuring pipe; Step 2.5: Calculate the instantaneous water phase cross-sectional fraction of the gas-water two-phase flow in the measuring pipe according to Formula 5: : Formula 5 Step 2.6: Calculate the gas phase cross-sectional fraction according to formula 6 : Formula 6.

3. The gas-water two-phase flow ultrasonic measurement method according to claim 1, characterized in that: The step three includes: The average Doppler frequency shift is obtained by analyzing the spectrum of the ultrasonic signal at the receiving end , combined with the speed of sound in water , calculate the true velocity of the water phase according to formula 7 : Formula 7 Where, Indicates the center frequency of the ultrasonic wave emitted by the probe. Indicates the angle between the incident sound wave and the pipe wall on the probe side.

4. The gas-water two-phase flow ultrasonic measurement method according to claim 1, characterized in that: The fourth step includes: The two self-transmitting and self-receiving ultrasonic probes transmit ultrasonic signals simultaneously; When the correlation coefficient When the maximum value is reached, according to Formula 8, the delay time of the signals received by the two ultrasonic probes is The cross-correlation velocity is obtained from the center distance L. : Formula 8 Where, is the delay time between the two signals, Indicates the center distance between two ultrasonic probes; Among them, the correlation coefficient Determine according to formula 9: Formula 9 Where, To measure time, Indicates the delay time of upstream and downstream receiving signals; The cross-correlation velocity Equivalent to the velocity of the air-water interface wave .

5. The gas-water two-phase flow ultrasonic measurement method according to claim 2, characterized in that: The step five includes: Combining the above formula 10 and the above formula 11, assuming that the pressure drop gradients of the gas and water phases are equal, we get formula 12: Formula 12 Where, β is the tilt angle, when the pipe is vertical β =90°; Will β =90°, cross-sectional area occupied by gas phase , cross-sectional area occupied by water phase , the gas phase cross-sectional content , the aqueous phase cross-sectional content 、Water phase wet periphery , water phase and wall shear force , air-water interface length , air-water interface shear force Substituting into Formula 12, we obtain Formula 13: Formula 13 in, is the friction coefficient of the water phase tube wall, which is expressed by formula 14: Formula 14 Where, is the viscosity of the water phase; Friction coefficient between air and water phases Expressed by Formula 15: Formula 15 Gas phase Reynolds number Expressed by formula 16: Formula 16 Where, is the gas phase viscosity; The actual flow rate of the water phase , the velocity of the air-water interface wave , the friction coefficient of the water phase tube wall , the friction coefficient between the gas and water phases , the gas phase Reynolds number , substitute into formula 13 to obtain formula 17, and calculate the actual gas phase flow rate : Official 17.

6. The gas-water two-phase flow ultrasonic measurement method according to claim 1, characterized in that: The step six comprises: Calculate the superficial velocity of the gas phase according to formula 18 : Official 18 The superficial velocity of the water phase is calculated according to formula 19 : Official 19 The total apparent velocity of the gas-water two-phase flow is calculated according to formula 20 : Official 20.

7. The gas-water two-phase flow ultrasonic measurement method according to claim 1, characterized in that: The step seven comprises: Calculate the volume flow rate of the gas phase according to formula 21 : Official 21 The volume flow rate of the water phase is calculated according to formula 22 : Official 22 The total volume flow rate of the gas-water two-phase flow is calculated according to formula 23 : Official 23.

8. An ultrasonic measuring device using the gas-water two-phase flow ultrasonic measuring method according to any one of claims 1 to 7, characterized in that: include: a measuring pipe through which a gas-water two-phase flow flows; a phase separation component, arranged on the measuring pipe; an ultrasonic measurement component, arranged on the measurement pipe; Wherein, the phase separation component includes a vane cyclone, and at least one vane cyclone is provided upstream of the measuring pipe and upstream of the ultrasonic measuring component; The ultrasonic measurement assembly includes an ultrasonic signal transmitter and receiver, and a plurality of ultrasonic probes electrically connected to the ultrasonic signal transmitter and receiver, wherein the ultrasonic probes are arranged on the measuring pipe, including two single crystal probes and two wedge probes, the two single crystal probes are self-transmitting and self-receiving probes, and the axial spacing along the measuring pipe is 1-3 times the inner diameter of the measuring pipe; the two wedge probes are single-transmitting and single-receiving probes, and are arranged closely on one axial side of the measuring pipe.

9. The ultrasonic measuring device according to claim 8, wherein: The phase separation assembly further includes an orifice plate, which is disposed upstream of the vane swirler in the ultrasonic measurement assembly.

10. The ultrasonic measuring device according to claim 8, wherein The phase separation component further includes a vane swirler disposed downstream of the ultrasonic measurement component.

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