A gas-liquid two-phase flow pattern identification and characterization method, detection device and application

Abstract

The present invention discloses a method for identifying and characterizing the flow pattern of a gas-liquid two-phase flow, a detection device and an application thereof, and relates to the fields of multiphase flow measurement technology and flow pattern identification technology. It uses an ultrasonic detection device to detect the pipeline, collect echo signals, and obtain discrimination parameters; then, it performs flow pattern identification in combination with the discrimination parameters, and the types of flow pattern identification are slug flow, annular flow, and laminar flow; the interface shape is printed according to the results obtained by the flow pattern identification, and finally, the results after flow pattern identification and interface shape printing are output. In addition to slug flow, annular flow, and flat laminar flow, the present invention can also identify laminar flow patterns of the remaining three different interface shapes. At the same time, it accurately depicts the two-phase interface shapes of different flow patterns, solving the problems of incomplete flow pattern identification, incomplete interface shape depiction, and low accuracy in the prior art. The present invention fills the gap in the field of laminar flow pattern identification and interface shape characterization with different interface shapes, and has broad application prospects.

Description

Technical Field

[0001] The present invention relates to the fields of multiphase flow measurement technology and flow pattern identification technology, and in particular to a method and device for gas-liquid two-phase flow pattern identification and two-phase interface shape characterization, which is suitable for two-phase flow pattern identification and liquid accumulation judgment in oil and gas transmission pipelines. Background Art

[0002] The identification of gas-liquid two-phase flow patterns has always been a hot topic in the field of oil and gas pipeline research. Accurate identification of two-phase flow patterns not only helps to accurately characterize the flow characteristics and heat and mass transfer characteristics of the fluid, but also helps to predict the flow state of undetected areas of the pipeline, thereby achieving the purpose of reasonably setting transportation parameters, effectively formulating a cleaning system, and extending the service life of the pipeline. At present, gas-liquid two-phase flow patterns are divided into three types: separation flow, dispersed flow, and intermittent flow. Among them, laminar flow is the main flow pattern in the gas-liquid two-phase in the gas pipeline. According to the different interface shapes, laminar flow can be divided into: flat, annular, curved, and wavy. For example, Figure 2 Ultrasonic testing technology is one of the most widely used and frequently used non-destructive testing technologies at home and abroad. It is widely used in the fields of identifying gas-liquid two-phase flow patterns and measuring liquid level height in pipes.

[0003] At present, existing technologies mainly focus on the identification of three flow patterns: slug flow, laminar flow, and annular flow, and the measurement of the liquid level of flat laminar flow. The main research reports are:

[0004] "Identification Method of Gas-Liquid Two-Phase Flow Patterns in Horizontal Pipes Based on Ultrasonic Technology, Oil and Gas Storage and Transportation, 2014, 01" combines numerical simulation and laboratory experiments to analyze and compare the echo characteristics of three flow patterns: stratified flow, annular flow, and slug flow, as a basis for distinguishing the three flow patterns;

[0005] Ultrasonic Measurement of Liquid Level in Drain Pipes, Nondestructive Testing, February 2019. The liquid level in a flat laminar flow pattern is calculated by analyzing the acoustic path of the wall thickness echo and the water-air interface reflection echo.

[0006] "Research on the Law of Liquid Accumulation and Monitoring Technology of Wet Gas Pipelines with Variable Terrain, China University of Petroleum (East China), June 2015" proposed a method to identify three flow patterns: slug flow, laminar flow, and annular flow, based on the echo characteristics of solid-fluid at different locations and whether the characteristic curve changes with time.

[0007] "Study on Ultrasonic Gas-Liquid Two-Phase Flow Parameter Detection, China University of Petroleum (East China), 2015" In order to avoid the influence of wall thickness echo on the detection of liquid film thickness in the pipe, the probe is embedded in the pipe wall. The detection accuracy is high, but the pipeline structure is damaged.

[0008] Application No. 201810747303.8 discloses a method for measuring the thickness of a gas-liquid two-phase flow liquid film based on ultrasound. The method provides a method for calculating the average liquid film thickness by performing fast Fourier transform on the incident and reflected ultrasonic waves.

[0009] Application No. 201610544478.X discloses a method and device for quantitatively determining the flow pattern of a horizontal gas-liquid two-phase flow. The method uses the liquid film thickness as a known condition, establishes a flow pattern database, forms a quantitative determination basis for flow pattern identification, and ultimately achieves quantitative determination of the flow pattern of the two-phase flow.

[0010] In summary, the existing technology does not distinguish between laminar flows with different interface shapes, and at the same time, the interface shapes of flow types other than flat laminar flow have not been studied. Summary of the Invention

[0011] In view of the shortcomings of the existing technology, one of the purposes of the present invention is to provide a method for identifying and characterizing the flow pattern of gas-liquid two-phase flow. The method covers three categories and six new methods for gas-liquid two-phase flow flow pattern identification and gas-liquid interface characterization. It has the advantages of comprehensive flow pattern identification and comprehensive interface shape characterization with high accuracy, filling the gap in the field of laminar flow pattern identification and interface shape characterization with different interface shapes.

[0012] Its technical solutions include:

[0013] A method for identifying and characterizing gas-liquid two-phase flow patterns comprises the following steps: using an ultrasonic detection device to detect a pipeline, collecting echo signals, and obtaining discrimination parameters; then, combining the discrimination parameters to perform flow pattern identification, wherein the types of flow pattern identification are slug flow, annular flow, and laminar flow; printing an interface shape based on the results of the flow pattern identification; and finally, outputting the results of the flow pattern identification and interface shape printing.

[0014] The above-mentioned gas-liquid two-phase flow pattern identification and characterization method, the ultrasonic detection device includes a probe, a transmitting circuit, a receiving circuit, a processor, a display circuit and a power supply circuit, the above-mentioned receiving circuit includes a same-direction frequency selection amplifier circuit, a filter amplifier circuit and a shaping circuit, and the target object is detected through the above-mentioned probe.

[0015] Then the signal passes through the same-direction frequency-selective amplifier circuit, the filter amplifier circuit and the shaping circuit in sequence and is input into the above-mentioned processor. The above-mentioned transmitting circuit is located between the above-mentioned processor and the probe. The above-mentioned transmitting circuit includes a signal amplification circuit and a transformer component. The signal recorded after being processed by the processor is input into the above-mentioned display circuit. The above-mentioned display circuit includes two parts: a waveform recorder and a display screen. The above-mentioned waveform recorder records the obtained signal and displays it on the above-mentioned display screen; the above-mentioned power supply circuit is used to supply power to all parts.

[0016] In the above-mentioned method for identifying and characterizing the flow pattern of a gas-liquid two-phase flow, the above-mentioned discrimination parameters include determining the mutation point, detecting the liquid film thickness and the stability of the echo characteristic curve.

[0017] The above-mentioned method for identifying and characterizing the flow pattern of a gas-liquid two-phase flow determines the mutation point by distinguishing whether the internal interface is a solid-liquid interface or a solid-gas interface based on the ultrasonic echo curve. When the probe of the ultrasonic detection device moves along the circumferential direction of the pipeline, when the echo characteristic curve on the oscilloscope at a certain position suddenly changes, it indicates that the internal interface at that position has changed from a solid-gas interface to a solid-liquid interface or from a solid-liquid interface to a solid-gas interface. This point is the critical point between the solid-liquid interface and the solid-gas interface.

[0018] In the above-mentioned method for identifying and characterizing the flow pattern of a gas-liquid two-phase flow, the liquid film thickness is determined based on the time interval Δt between the wall thickness echo and the interface echo in the same round reaching the receiving probe and the propagation velocity v of the ultrasonic wave in the liquid phase obtained by query. The liquid film thickness at the detection position is h, h = v × Δt / 2; if no interface echo signal is found, it indicates that the liquid film thickness at this position is 0.

[0019] In the above-mentioned method for identifying and characterizing the flow pattern of a gas-liquid two-phase flow, when confirming the stability of the echo characteristic curve, if the interface results identified at the same position are different each time, it means that the interface state at that position is unstable and the flow state in the pipe is slug flow or wavy stratified flow.

[0020] The above-mentioned method for identifying and characterizing the flow pattern of a gas-liquid two-phase flow distinguishes between slug flow and wavy stratified flow based on the following: since the gas-liquid phase distribution characteristics on the cross-section of the pipe in the slug flow are constantly changing, the interface identified each time at the same position may be different, and this characteristic may appear in the entire detection area; the gas-liquid interface of the wavy stratified flow is composed of several periodic sinusoidal curves, and the shape of the interface shows a periodic change law with the vibration of the sine wave, resulting in the mutation point moving up and down only within a certain range (peak-trough range).

[0021] The above-mentioned method for identifying and characterizing the flow pattern of a gas-liquid two-phase flow is to identify the flow pattern as a slug flow by: the detection results at the same position in the entire detection area are not the same, and the echo characteristic curve changes with time; the method for identifying the flow pattern as an annular flow is to: there is no mutation point, the entire detection area is a solid-liquid interface, the liquid film thickness at each position is not 0, and the echo curve does not change with time.

[0022] The above-mentioned method for identifying and characterizing the flow pattern of a gas-liquid two-phase flow, the identification method for the flow pattern as a flat laminar flow is: there is a mutation point, the liquid film thickness at the mutation point is 0, and the height of the mutation point position is equal to the liquid film thickness at the 6 o'clock position of the pipeline, and the echo curve is stable; the identification method for the flow pattern as a curved laminar flow is: there is a mutation point, the liquid film thickness at the mutation point is 0, and the height of the mutation point position is not equal to the liquid film thickness at the 6 o'clock position of the pipeline, and the echo curve is stable; the identification method for the flow pattern as annular laminar flow is: there is a mutation point, the liquid film thickness at the mutation point is not 0, and the liquid film thickness at the mutation point is equal to the liquid film thickness at the 6 o'clock position of the pipeline, and the echo curve is stable; the identification method for the flow pattern as a wavy laminar flow is: there is a mutation point, but the position of the mutation point is always changing, and the range of change is limited. At the same time, the detection results of the liquid film height at the 6 o'clock direction of the pipeline are also different each time.

[0023] The above-mentioned method for identifying and characterizing the flow pattern of a gas-liquid two-phase flow, when printing the interface shape, for slug flow, its shape cannot be determined, and only needs to be identified; for annular flow, the liquid film thickness at 0 o'clock, 3 o'clock, and 6 o'clock are determined respectively, and then the three points are connected to determine the shape of the right half of the interface; for flat laminar flow, curved laminar flow, and annular laminar flow, the mutation point and the liquid film thickness at 6 o'clock are determined respectively, and then the interface shape can be determined by connecting the two points; for wavy laminar flow, the peak and trough positions of the sine wave are determined through multiple tests, and the period of the sine wave is determined according to the dynamic change of the mutation point, and finally the interface shape in a certain state in the tube is determined; after drawing the interface shape of the 0 o'clock to 6 o'clock area, the interface shape of the 6 o'clock to 0 o'clock area is supplemented according to the principle of symmetry about the line connecting 0 o'clock to 6 o'clock, and finally, the drawing of the entire interface shape is completed.

[0024] Another object of the present invention is to provide a detection device for identifying the flow pattern of gas-liquid two-phase flow, including a probe, a transmitting circuit, a receiving circuit, a processor, a display circuit and a power supply circuit. The above-mentioned detection device is used to detect a pipe that has been polished to expose the metal pipe substrate and is coated with a special ultrasonic coupling agent. The above-mentioned probe is arranged outside the target pipe.

[0025] The above-mentioned detection device for identifying the flow pattern of gas-liquid two-phase flow, the above-mentioned receiving circuit includes a same-direction frequency-selective amplifier circuit, a filter amplifier circuit and a shaping circuit; the above-mentioned transmitting circuit includes a signal amplifier circuit and a transformer assembly; the above-mentioned display circuit includes two parts: a waveform recorder and a display screen.

[0026] The above-mentioned detection device for identifying the flow type of gas-liquid two-phase flow, one end of the above-mentioned probe is connected to the above-mentioned transmitting circuit, and the other end is connected to the above-mentioned same-direction frequency-selective amplifier circuit; the other end of the above-mentioned transmitting circuit is connected to the above-mentioned processor, the other end of the above-mentioned same-direction frequency-selective amplifier circuit is connected to the above-mentioned filtering amplifier circuit, the other end of the above-mentioned filtering amplifier circuit is connected to the above-mentioned shaping circuit, the other end of the above-mentioned shaping circuit is connected to the above-mentioned processor, and the above-mentioned processor is connected to the above-mentioned display circuit.

[0027] The above-mentioned detection method of the detection device for gas-liquid two-phase flow pattern identification, wherein the single detection method comprises the following steps in sequence:

[0028] (1) The processor transmits a pulse signal, which is amplified by the signal amplifier circuit and transformer assembly, and then drives the ultrasonic probe to transmit ultrasonic waves with sufficient energy;

[0029] (2) The probe is driven to emit ultrasonic waves. When the ultrasonic waves encounter the target object, they are reflected and return along the original path until they are absorbed by the receiving probe.

[0030] (3) The reflected signal is amplified by the same-direction frequency-selective amplifier circuit, the filter amplifier circuit, and the shaping circuit. The same-phase AC amplifier circuit is used to amplify the frequency band, and the filter amplifier circuit performs secondary amplification. The shaping circuit solves the tailing problem of the transmitting circuit.

[0031] (4) After the processor detects and obtains the ideal echo signal, it records the waveform and displays it on the display screen;

[0032] (5) Move the probe to the next position and repeat steps (1) to (4).

[0033] The present invention also aims to provide an application of the above method.

[0034] The above-mentioned gas-liquid two-phase flow pattern identification and characterization method is applied in the two-phase flow pattern identification and liquid accumulation situation judgment in oil and gas transmission pipelines.

[0035] Compared with the prior art, the present invention brings the following beneficial technical effects:

[0036] The existing technology mainly focuses on the research of horizontal liquid level detection methods represented by flat laminar flow, and there is little research on the gas-liquid interface shapes of flow types such as annular flow, curved laminar flow, and wavy laminar flow. The present invention overcomes the technical defects of the existing technology. The present invention provides a gas-liquid two-phase flow flow type identification and characterization method. In addition to slug flow, annular flow, and flat laminar flow, it can also identify the other three laminar flow types with different interface shapes. At the same time, it accurately depicts the two-phase interface shapes of different flow types, solving the problems of incomplete flow type identification, incomplete interface shape characterization, and low accuracy in the existing technology.

[0037] The present invention installs the probe outside the pipe without damaging the pipe wall structure. At the same time, in order to solve the influence of the superposition of the wall thickness echo and the gas-liquid interface echo in the pipe on the waveform judgment, the period of the wall thickness echo cycle is calculated in combination with the pipe thickness and the propagation speed of ultrasonic waves in the metal material of the pipe. When the displayed waveform begins to become irregular and chaotic, the arrival time of the interface echo in the pipe can be determined, thereby determining the thickness of the liquid film at the detection position.

[0038] The method for identifying and characterizing gas-liquid two-phase flow patterns provides a promising approach to identifying and characterizing laminar flow patterns and interface shapes, addressing challenges in different interface shapes. The method can be applied to identifying two-phase flow patterns and determining liquid accumulation within oil and gas pipelines. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] The present invention will be further described below with reference to the accompanying drawings:

[0040] Figure 1 This is a schematic structural diagram of a detection device for identifying flow patterns of gas-liquid two-phase flow according to the present invention;

[0041] Figure 2 This is the gas-liquid two-phase flow pattern diagram of the present invention;

[0042] Figure 3 This is a flow chart for gas-liquid two-phase flow pattern identification and interface characterization of the present invention. DETAILED DESCRIPTION

[0043] The present invention proposes a gas-liquid two-phase flow pattern identification and characterization method, detection device and application. In order to make the advantages and technical solutions of the present invention clearer and more specific, the present invention is described in detail below with reference to specific embodiments.

[0044] like Figure 1 As shown, the detection device required by the present invention mainly relates to an ultrasonic detection device. First, the composition of the detection device of the present invention and the detection method thereof are described in detail.

[0045] 1. The detection device of the present invention comprises the following components:

[0046] 1 Sonoscaan probe;

[0047] Transmitting circuit, including: signal amplifying circuit and transformer assembly;

[0048] Receiving circuit: including: same-direction frequency-selective amplifier circuit, filter amplifier circuit, and shaping circuit;

[0049] Processor: integrates functions such as pulse signal transmission, echo signal reception, and data processing;

[0050] Display circuit: consists of two parts: waveform recording and display screen;

[0051] Power supply circuit: provides power to all parts;

[0052] Pipeline treatment: peel off the pipeline anti-corrosion layer, polish to expose the metal pipeline base, and apply ultrasonic special coupling agent.

[0053] Parts of the above detection device that are not described in detail can be implemented by those skilled in the art by referring to existing technologies.

[0054] The above detection device is used for detection, and the single detection steps are as follows:

[0055] (1) The processor transmits a 200MHz pulse signal, which is amplified by the signal amplifier circuit and transformer assembly, and then drives the ultrasonic probe to transmit ultrasonic waves with sufficient energy;

[0056] (2) The ultrasonic probe is driven to emit ultrasonic waves. When the ultrasonic waves encounter the target object, they are reflected and return along the original path until they are absorbed by the receiving probe.

[0057] (3) Since the energy of the ultrasonic wave is constantly absorbed and attenuated during the transmission process, and is mixed with various interference noises, the reflected waveform is so weak that the processor cannot directly identify it. Therefore, it is necessary to perform the same-direction frequency selection amplification, filtering amplification and shaping operations on the reflected signal. A same-phase AC amplifier circuit is selected to amplify the 200MHz frequency band, and a second amplification is performed through a filtering amplifier circuit. The shaping circuit solves the tailing problem of the transmitting circuit, prevents the tail wave from being coupled into the recovered wave, and improves the measurement accuracy.

[0058] (4) After the processor detects and obtains the ideal echo signal, it records the waveform and displays it on the display screen;

[0059] (5) Move the probe to the next position and repeat steps (1) to (4).

[0060] 2. Flow pattern identification method

[0061] As the main innovation of the present invention, in the flow pattern identification method, the gas-liquid two-phase flow pattern includes: slug flow, annular flow, and laminar flow. Among them, laminar flow can be divided into: flat, annular, curved, and wavy due to the different shapes of the two-phase interface. Figure 2 shown.

[0062] The flow pattern identification process is shown in the attached Figure 3 , slowly move the probe between 0 o'clock and 6 o'clock on the pipeline, test back and forth multiple times, collect echo signals, observe the changes in the waveform on the display screen, and record them.

[0063] (1) Obtaining the discrimination parameters

[0064] 1) Determine the mutation point

[0065] Due to the different reflection coefficients of ultrasound at solid-gas and solid-liquid interfaces, the attenuation of wall thickness echoes of the same echo frequency varies. The attenuation rate at the solid-liquid interface is faster than that at the solid-gas interface. As the number of echoes increases, the difference in the ultrasonic echo characteristic curves between the two interfaces becomes increasingly apparent. Furthermore, when the internal interface is a solid-liquid interface, the echo characteristic curve is composed of the wall thickness echo and the echo from the gas-liquid interface within the tube, while when the internal interface is a solid-gas interface, the echo characteristic curve is composed solely of the wall thickness echo. Therefore, based on these two differences, the ultrasonic echo curve can be used to distinguish whether the internal interface is a solid-liquid interface or a solid-gas interface.

[0066] Therefore, when the probe is moving, when the echo characteristic curve on the oscilloscope suddenly changes (hereinafter referred to as the mutation point), it indicates that the interface at that position has changed from a solid-gas interface to a solid-liquid interface or from a solid-liquid interface to a solid-gas interface. This point is the critical point between the solid-liquid interface and the solid-gas interface.

[0067] 2) Detection of liquid film thickness

[0068] From 1), we can see that the liquid film thickness at that location can be calculated based on the propagation time of the transmitted ultrasonic wave within the pipe. For thin liquid films, to address the impact of the superposition of the wall thickness echo and the gas-liquid interface echo on waveform analysis, we first calculate the wall thickness echo cycle period based on the pipe thickness and the ultrasonic wave propagation velocity in the pipe metal. Next, we observe the waveform changes. When the waveform on the display begins to exhibit irregular shapes and become disorganized, it indicates that the interface echo has returned to the receiving probe. Therefore, based on the time interval Δt between the wall thickness echo and the interface echo arriving at the receiving probe in the same cycle and the ultrasonic wave propagation velocity v obtained in the liquid phase, we can ultimately determine the liquid film thickness h at the detection location, where h = v × Δt / 2. Specifically, if no interface echo signal is detected, the liquid film height at that location is zero.

[0069] 3) Echo characteristic curve stability

[0070] If the interface results identified at the same location are different each time, it means that the interface state at that location is unstable, and the flow state in the pipe may be slug flow or wavy stratified flow.

[0071] The distinction between the two is based on the following: in slug flow, the gas-liquid phase distribution characteristics on the cross section of the pipe are constantly changing, and the interface identified at the same position each time may be different. This characteristic may appear in the entire detection area; while the gas-liquid interface of wavy stratified flow can be regarded as a composition of several periodic sinusoidal curves. The interface shape will show a periodic change law with the vibration of the sine wave, resulting in the mutation point moving up and down only within the range of the peak and trough. Figure 2(e).

[0072] (2) Flow pattern identification

[0073] Based on the identification of mutation points, liquid film thickness, and echo characteristic curve stability, the identification methods for each flow type are as follows:

[0074] 1) Slug flow

[0075] The detection results at the same location in the entire detection area are different, and the echo characteristic curve changes over time;

[0076] 2) Annular flow

[0077] There is no mutation point, the entire detection area is a solid-liquid interface, the liquid film thickness at each position is not 0, and the echo curve does not change with time;

[0078] 3) Laminar flow

[0079] There is a mutation point, the thickness of the liquid film at the mutation point is 0, and the height of the mutation point is equal to the thickness of the liquid film at 6 o'clock. At this time, the shape is flat and the echo curve is stable;

[0080] There is a mutation point, the thickness of the liquid film at the mutation point is 0, and the height of the mutation point is not equal to the thickness of the liquid film at 6 o'clock. At this time, the shape is curved and the echo curve is stable;

[0081] There is a mutation point, the liquid film thickness at the mutation point is not 0, and the liquid film thickness at the mutation point is equal to the liquid film thickness at the 6 o'clock position. At this time, the shape is ring-shaped and the echo curve is stable;

[0082] There is a mutation point, but the position of the mutation point is always changing, and the range of change is limited. At the same time, the detection results of the liquid film height at 6 o'clock are also different each time, and the shape is wavy at this time.

[0083] (3) Interface shape printing

[0084] Since the gas-liquid phase distribution characteristics in the slug flow tube are constantly changing, the slug flow shape cannot be determined, so it only needs to be identified;

[0085] For annular flow, determine the liquid film thickness at 0 o'clock, 3 o'clock, and 6 o'clock respectively, and then connect the three points to determine the shape of the right half of the interface;

[0086] For flat laminar flow, curved laminar flow, and annular laminar flow, determine the mutation point and the liquid film thickness at 6 o'clock respectively, and then connect the two points to determine the interface shape;

[0087] For wavy laminar flow, the peak and trough positions of the sine wave are determined through multiple tests, the period of the sine wave is determined based on the dynamic changes of the mutation point, and finally the interface shape under a certain state inside the pipe is determined.

[0088] After the interface shape of the 0 o'clock to 6 o'clock area is drawn, the interface shape of the 6 o'clock to 0 o'clock area is completed according to the principle of symmetry about the 0 o'clock to 6 o'clock line. Finally, the entire interface shape is drawn successfully.

[0089] The present invention will be further described below with reference to specific embodiments.

[0090] Example 1:

[0091] Annular laminar flow, identification method: there is no mutation point, the entire detection area is a solid-liquid interface, the liquid film thickness at each position is not 0, and the echo curve does not change with time;

[0092] Interface characterization: Determine the thickness of the liquid film at 0 o'clock, 3 o'clock, and 6 o'clock respectively, and then connect the three points to determine the shape of the right half of the interface. The interface shape is shown in the attached figure. Figure 2 (a)

[0093] Example 2:

[0094] Flat laminar flow, identification method: there is a mutation point, the liquid film thickness at the mutation point is 0, at the same time, the height of the mutation point is equal to the liquid film thickness at 6 o'clock, and the echo curve is stable;

[0095] Interface characterization: determine the mutation point and the thickness of the liquid film at 6 o'clock respectively, and then connect the two points to determine the shape of the right half of the interface. The left half is completed according to the principle of symmetry about the line from 0 o'clock to 6 o'clock, as shown in the attached figure. Figure 2 (b) shown.

[0096] Example 3:

[0097] Annular laminar flow, identification method: there is a mutation point, the liquid film thickness at the mutation point is not 0, and the liquid film thickness at the mutation point is equal to the liquid film thickness at 6 o'clock, and the echo curve is stable;

[0098] Interface characterization: Determine the thickness of the liquid film at 0 o'clock, 3 o'clock, and 6 o'clock respectively, and then connect the three points to determine the shape of the right half of the interface. The left half is completed according to the principle of symmetry about the line connecting 0 o'clock and 6 o'clock. The interface shape is shown in the attached figure. Figure 2 (c) shown.

[0099] Example 4:

[0100] Curved laminar flow, identification method: there is a mutation point, the liquid film thickness at the mutation point is 0, and the height of the mutation point is not equal to the liquid film thickness at 6 o'clock, and the echo curve is stable;

[0101] Interface characterization: Determine the mutation point and the thickness of the liquid film at 6 o'clock respectively, then connect the two points to determine the shape of the right half of the interface. The left half is completed according to the principle of symmetry about the line from 0 o'clock to 6 o'clock. The interface shape is shown in the attached figure. Figure 2 (d) shown.

[0102] Example 5:

[0103] Identification method for wavy laminar flow: There is a mutation point, but the location of the mutation point is constantly changing, and the range of change is limited. At the same time, the test results of the liquid film height at 6 o'clock are also different each time;

[0104] Interface characterization: Through multiple tests, the peak and trough positions of the sine wave are determined, and the sine wave period is determined according to the dynamic changes of the mutation point, and finally the shape of the liquid film in the tube is determined. The interface shape is shown in the attached figure. Figure 2 (e) shown.

[0105] Example 6:

[0106] For slug flow, the detection results at the same location in the entire detection area are different, and the echo characteristic curve changes with time.

[0107] The preferred embodiments of the present invention are described in detail above with reference to the accompanying drawings; however, the present invention is not limited thereto.

[0108] Although terms such as transmitting circuit, receiving circuit, and processor are frequently used in this document, the possibility of using other terms is not excluded. These terms are used only to more conveniently describe and explain the essence of the present invention; interpreting them as any additional limitations is contrary to the spirit of the present invention.

[0109] It should be further noted that the specific embodiments described herein are merely illustrative of the spirit of the present invention. Persons skilled in the art may make various modifications, additions, or substitutions to the described specific embodiments without departing from the spirit of the present invention or exceeding the scope of the appended claims.

Claims

1. A method for identifying and characterizing gas-liquid two-phase flow patterns, characterized by: The system uses an ultrasonic detection device to detect the pipeline, collect echo signals, and obtain discrimination parameters. Flow pattern identification is then performed based on the discrimination parameters. The ultrasonic detection device's probe is slowly moved between 0 o'clock and 6 o'clock in the pipeline, performing multiple back-and-forth detections. The echo signals are collected and the waveform changes on the display are observed and recorded. The flow pattern identification types are slug flow, annular flow, and laminar flow. Printing the interface shape according to the result obtained by the flow pattern identification, and finally outputting the result after the flow pattern identification and the interface shape printing; The discrimination parameters include determining the mutation point, detecting the thickness of the liquid film and the stability of the echo characteristic curve; When printing the interface shape, for slug flow, its shape cannot be determined and only needs to be identified; For annular flow, determine the liquid film thickness at 0 o'clock, 3 o'clock, and 6 o'clock respectively, and then connect the three points to determine the shape of the right half of the interface; For flat laminar flow, curved laminar flow, and annular laminar flow, determine the mutation point and the liquid film thickness at 6 o'clock respectively, and then connect the two points to determine the interface shape; For wavy laminar flow, the peak and trough positions of the sine wave are determined through multiple tests, and the period of the sine wave is determined according to the dynamic changes of the mutation point, and finally the interface shape in a certain state inside the pipe is determined; After the interface shape of the 0 o'clock to 6 o'clock area is drawn, the interface shape of the 6 o'clock to 0 o'clock area is completed according to the principle of symmetry about the 0 o'clock to 6 o'clock line. Finally, the drawing of the entire interface shape is completed.

2. A method for identifying and characterizing gas-liquid two-phase flow patterns according to claim 1, characterized in that: The ultrasonic detection device includes a probe, a transmitting circuit, a receiving circuit, a processor, a display circuit and a power supply circuit. The receiving circuit includes a same-direction frequency-selective amplifier circuit, a filter amplifier circuit and a shaping circuit. The target object is detected through the probe. Then, the signal is input into the processor after passing through the same-direction frequency-selective amplifier circuit, the filter amplifier circuit and the shaping circuit in sequence. The transmitting circuit is located between the processor and the probe. The transmitting circuit includes a signal amplification circuit and a transformer component. The signal recorded after being processed by the processor is input into the display circuit. The display circuit includes two parts: a waveform recorder and a display screen. The waveform recorder records the obtained signal and displays it on the display screen. The power supply circuit is used to supply power to all parts.

3. The method for identifying and characterizing gas-liquid two-phase flow patterns according to claim 1, characterized in that: When determining the mutation point, the ultrasonic echo curve is used to distinguish whether the internal interface is a solid-liquid interface or a solid-gas interface. When the probe of the ultrasonic detection device moves along the circumference of the pipeline, when the echo characteristic curve on the oscilloscope at a certain position suddenly changes, it indicates that the internal interface at that position has changed from a solid-gas interface to a solid-liquid interface or from a solid-liquid interface to a solid-gas interface. This point is the critical point between the solid-liquid interface and the solid-gas interface.

4. The method for identifying and characterizing gas-liquid two-phase flow patterns according to claim 1, wherein: The liquid film thickness is determined based on the time interval Δ𝑡 between the wall thickness echo and the interface echo in the same round reaching the receiving probe and the ultrasonic wave propagation velocity v in the liquid phase obtained by query. The liquid film thickness at the detection position is h, h = 𝑣 × Δ𝑡 / 2. If no interface echo signal is found, it indicates that the liquid film thickness at this position is 0.

5. The method for identifying and characterizing gas-liquid two-phase flow patterns according to claim 1, wherein: When confirming the stability of the echo characteristic curve, if the interface results identified at the same location are different each time, it means that the interface state at that location is unstable and the flow type in the pipe is slug flow or wavy stratified flow.

6. A gas-liquid two-phase flow pattern identification and characterization method according to claim 5, characterized in that: The distinction between slug flow and wavy stratified flow is based on the following: In slug flow, the gas-liquid distribution characteristics on the cross-section of the pipe constantly change, so the interface identified at the same location may be different each time, and this characteristic can appear throughout the entire detection area. In wavy stratified flow, the gas-liquid interface is composed of several periodic sinusoidal curves, and the interface shape exhibits a periodic change pattern with the vibration of the sine wave, resulting in the mutation point moving up and down only within a certain range.

7. A gas-liquid two-phase flow pattern identification and characterization method according to claim 1, characterized in that: The method for identifying the flow type as slug flow is: the detection results at the same position in the entire detection area are different, and the echo characteristic curve changes with time. The method for identifying the flow type as annular flow is: there is no mutation point, the entire detection area is a solid-liquid interface, the liquid film thickness at each position is not zero, and the echo curve does not change with time.

8. The method for identifying and characterizing gas-liquid two-phase flow patterns according to claim 1, characterized in that: The identification method for the flow type as flat laminar flow is: there is a mutation point, the liquid film thickness at the mutation point is 0, and the height of the mutation point is equal to the liquid film thickness at the 6 o'clock position of the pipeline, and the echo curve is stable; the identification method for the flow type as curved laminar flow is: there is a mutation point, the liquid film thickness at the mutation point is 0, and the height of the mutation point is not equal to the liquid film thickness at the 6 o'clock position of the pipeline, and the echo curve is stable; the identification method for the flow type as annular laminar flow is: there is a mutation point, the liquid film thickness at the mutation point is not 0, and the liquid film thickness at the mutation point is equal to the liquid film thickness at the 6 o'clock position of the pipeline, and the echo curve is stable; the identification method for the flow type as wavy laminar flow is: there is a mutation point, but the position of the mutation point is always changing, and the range of change is limited. At the same time, the detection results of the liquid film height at the 6 o'clock direction of the pipeline are also different each time.

9. A detection device for identifying flow patterns of gas-liquid two-phase flow, characterized in that: The gas-liquid two-phase flow pattern identification and characterization method according to claim 1 includes a probe, a transmitting circuit, a receiving circuit, a processor, a display circuit and a power supply circuit. The detection device is used to detect a pipe that has been polished to expose the metal pipe substrate and is coated with an ultrasonic coupling agent. The probe is set outside the target pipe.

10. The detection device for gas-liquid two-phase flow pattern identification according to claim 9, characterized in that: The receiving circuit includes a same-direction frequency-selective amplifier circuit, a filter amplifier circuit and a shaping circuit; the transmitting circuit includes a signal amplifier circuit and a transformer component; and the display circuit includes a waveform recorder and a display screen.

11. The detection device for gas-liquid two-phase flow pattern identification according to claim 10, characterized in that: One end of the probe is connected to the transmitting circuit, and the other end is connected to the same-direction frequency-selective amplifier circuit; the other end of the transmitting circuit is connected to the processor, the other end of the same-direction frequency-selective amplifier circuit is connected to the filter amplifier circuit, the other end of the filter amplifier circuit is connected to the shaping circuit, the other end of the shaping circuit is connected to the processor, and the processor is connected to the display circuit.

12. The detection method of a detection device for gas-liquid two-phase flow pattern identification according to claim 11, characterized in that: The single detection method includes the following steps in sequence: (1) The processor transmits a pulse signal, which is then amplified by the signal amplifier circuit and transformer assembly, and then drives the ultrasonic probe to transmit ultrasonic waves with sufficient energy; (2) The probe is driven to emit ultrasonic waves. When the ultrasonic waves encounter the target object, they are reflected and return along the original path until they are absorbed by the receiving probe. (3) The reflected signal is amplified by the same-direction frequency-selective amplifier circuit, the filter amplifier circuit and the shaping circuit. The same-phase AC amplifier circuit is used to amplify the frequency band, and the filter amplifier circuit performs secondary amplification. The shaping circuit solves the tailing problem of the transmitting circuit. (4) After the processor detects and obtains the ideal echo signal, it records the waveform and displays it on the screen; (5) Move the probe to the next position and repeat steps (1) to (4).

13. Application of the gas-liquid two-phase flow pattern identification and characterization method according to claim 1 in two-phase flow pattern identification and liquid accumulation judgment in oil and gas transmission pipelines.

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