A detection device and method for identifying gas-liquid two-phase flow pattern

Abstract

The present invention discloses a detection device and method for identifying the flow pattern of a gas-liquid two-phase flow, and relates to the technical field of multiphase flow measurement and flow pattern identification. The detection device proposed in the present invention includes a crawler, a controller, and a crawler travel guide rail. The crawler moves along the pipe wall along the crawler travel guide rail, and is provided with an ultrasonic detection probe, a coupling agent coating device, and a camera. The ultrasonic detection probe is used to monitor the positions of the ultrasonic detection probe and the coupling agent coating device, the coupling agent coating device is used to coat the coupling agent on the pipe wall, and the camera is used to record the ultrasonic detection process. The method for identifying the flow pattern of a gas-liquid two-phase flow proposed in the present invention uses the ultrasonic detection probe on the crawler to collect echo signals, obtain discrimination parameters, perform flow pattern identification, determine the interface morphology based on the flow pattern identification results, and output the flow pattern identification and interface morphology results. The present invention improves the accuracy of flow pattern identification and interface morphology characterization, which is beneficial for judging the liquid accumulation situation in the pipeline.

Description

Technical Field

[0001] The present invention relates to the field of multiphase flow measurement technology and flow pattern identification technology, and specifically to a detection device and method for identifying the flow pattern of gas-liquid two-phase flow, which is suitable for identifying two flow patterns and judging liquid accumulation in oil and gas transmission pipelines. Background Art

[0002] Gas-liquid two-phase flow is a common occurrence in industrial processes. When a gas-liquid mixture flows through a pipeline, the two phases exhibit different distribution patterns, known as flow patterns. Accurately identifying gas-liquid two-phase flow patterns not only helps accurately characterize the flow and heat and mass transfer characteristics of the fluid within the pipeline, but also helps predict the flow state in undetected areas within the pipeline, thereby enabling the rational setting of transmission parameters, the effective formulation of pipeline cleaning systems, and the extension of pipeline service life. Therefore, the identification of gas-liquid two-phase flow patterns has long been a hot topic in the field of oil and gas pipeline research.

[0003] Currently, the most common gas-liquid two-phase flows are slug flow, annular flow, and laminar flow. Laminar flow can be further divided into flat laminar flow, annular laminar flow, curved laminar flow, and wavy laminar flow, based on the shapes of the two gas-liquid interfaces. Common methods for detecting flow patterns within pipelines are categorized as intrusive and non-intrusive. Ultrasonic testing, as a non-destructive testing technology, is currently the most widely used and most frequently used both domestically and internationally. Ultrasonic waves have the characteristic of reflecting different echoes at interfaces with materials of different impedances, enabling them to identify gas-liquid two-phase flow patterns within pipelines and determine the liquid level within them.

[0004] At present, existing technologies mainly focus on the identification of slug flow, laminar flow and annular flow patterns and the measurement of liquid level in flat laminar flow. The main reports include:

[0005] Patent CN 202916242 U discloses an online monitoring device for the flow pattern of a gas-liquid two-phase flow. Six probes of the same length are arranged inside a pipeline and the flow pattern is measured by measuring the output signal of the probes. This method is an intrusive method that affects the flow field in the pipeline. The sensor components are easily contaminated and require adjustments and modifications to the existing pipeline system during measurement. In addition, this method has clear requirements for the medium to be measured. For gas and oil two-phase flows, the device cannot be used because both the gas and liquid phases are non-conductive.

[0006] Patent CN 110160473 A discloses a device for ultrasonically measuring the circumferential liquid film thickness of a gas-liquid two-phase flow. The device includes an ultrasonic transducer, a measuring pipe, and flanges fixed to both ends of the measuring pipe. Multiple openings are arranged circumferentially on the outer wall of the measuring pipe, and a fixing sleeve is provided. Multiple through-holes penetrating the fixing sleeve are also provided at positions on the fixing sleeve relative to the circumference of the outer wall of the measuring pipe. The through-holes on the fixing sleeve are penetrated on one side of the fixing sleeve to lead out the ultrasonic transducer cable port. The fixing sleeve is fixedly connected to the measuring pipe, and the openings of the measuring pipe are aligned one by one with the through-holes of the fixing sleeve. The through-holes of the fixing sleeve can accommodate an ultrasonic heat exchanger and are provided with internal threads. The ultrasonic transducer is fixed in the through-holes by tightening screws.

[0007] Patent CN 106247917 A discloses a method and device for quantitatively determining the flow of horizontal gas-liquid two-phase flow. The device for quantitatively determining the flow pattern of horizontal gas-liquid two-phase flow includes an acquisition module, a processing module, a calculation module, and a judgment module. The acquisition module is used to obtain two-phase flow film thickness data under various flow patterns. The processing module is used to perform signal processing and analysis on the two-phase flow film thickness data under various flow patterns according to the concept of multi-scale entropy, and extract the characteristics of different flow patterns. The calculation module is used to determine the multi-scale entropy arrangement distribution characteristic curve based on the extracted flow pattern characteristics, and calculate the multi-scale entropy rate of different flow pattern curves in the multi-scale entropy arrangement distribution diagram. The judgment module is used to establish flow pattern data based on the two-phase flow film thickness data, the multi-scale entropy arrangement distribution characteristic curve, and the multi-scale entropy rate under various flow patterns. The patent also discloses a method for quantitative determination of flow patterns of horizontal gas-liquid two-phase flows, which obtains the two-phase flow film thickness data under a variety of flow patterns, performs signal analysis and processing on the two-phase flow film thickness data under a variety of flow patterns according to the concept of multi-scale entropy, extracts the characteristics of different flow patterns, obtains the multi-scale entropy arrangement distribution characteristic curve based on the extracted flow pattern characteristics, and calculates the multi-scale entropy rate of different flow pattern curves of the multi-scale entropy arrangement distribution diagram, establishes a flow pattern database based on the two-phase flow film thickness data under a variety of flow patterns, obtains the multi-scale entropy arrangement distribution characteristic curve, and the multi-scale entropy rate, obtains the quantitative determination table of flow pattern identification, and realizes the quantitative determination of the flow pattern of horizontal gas-liquid two-phase flows.

[0008] In summary, the existing technology does not distinguish the laminar flow information of different interface shapes, and has not yet studied the interface shapes of flow types other than flat laminar flow. Summary of the Invention

[0009] In response to the shortcomings of the existing technology, the present invention proposes a detection device and method for identifying the flow pattern of gas-liquid two-phase flow, which realizes the accurate measurement of the flow pattern identification parameters of the gas-liquid two-phase flow inside the pipeline. At the same time, a new method for gas-liquid two-phase flow flow pattern identification and gas-liquid cross-section characterization covering three categories and six types is proposed. It has the characteristics of comprehensive flow pattern identification and accurate interface shape characterization, filling the gaps in the existing technology in the flow pattern identification and interface shape characterization of flow layers with different interface shapes.

[0010] To achieve the above object, the present invention adopts the following technical solutions:

[0011] A detection device for identifying the flow pattern of a gas-liquid two-phase flow, comprising a crawler, a controller, and a pair of crawler travel guide rails;

[0012] The crawler includes a body and an ultrasonic detection probe, a coupling agent application device, and a camera disposed on the body; the body includes a base plate and a fixed bracket, the bottom of the base plate being equipped with a pair of front wheels and a pair of rear wheels, both of which are magnetic wheels, and the rear wheels are connected to a power motor. A detection port is provided at the center of the base plate, and a fixed bracket is provided on the top surface of the base plate. A pair of fixed columns of the fixed bracket are separated on either side of the detection port and connected by a fixed rod. A first motion track and a second motion track are provided in parallel on the fixed rod. The first motion track and the second motion track are both located above the detection port, and the axial direction of the first motion track is perpendicular to the axial direction of the fixed rod. The ultrasonic detection probe and the coupling agent application device are respectively slidably connected to the first motion track via a retractable connecting rod. The ultrasonic detection probe is located on the side of the first motion track near the rear wheel, and the coupling agent application device is located on the side of the first motion track near the front wheel. The camera is slidably connected to the second motion track via a retractable connecting rod and is located on the side of the second motion track near the rear wheel. The ultrasonic detection probe, coupling agent application device, camera, power motor, and retractable connecting rod are all connected to a controller.

[0013] The crawler travel track is arranged along the circumference of the pipeline and is tightly attached to the outer wall of the pipeline. Magnets are embedded on the inner side of the crawler travel track. The front and rear wheels of the crawler are embedded in the crawler travel track and are slidably connected to the crawler travel track.

[0014] Preferably, the controller includes an ultrasonic signal excitation and processing system, a processor, a display circuit and a power supply circuit. The ultrasonic signal excitation and processing device includes a transmitting circuit and a receiving circuit. One end of the transmitting circuit is connected to the ultrasonic detection probe, and the other end is connected to the processor through a receiving circuit. The signal processed by the processor is input into the waveform recording module of the display circuit. The waveform recording module records the acquired signal and displays it on the display screen of the display circuit. The ultrasonic signal excitation and processing system, the processor and the display circuit are all connected to the power supply circuit.

[0015] Preferably, the transmitting circuit includes a signal amplifying circuit and a transformer component.

[0016] Preferably, the receiving circuit includes a same-direction frequency-selective amplifier circuit, a filter amplifier circuit and a shaping circuit.

[0017] Preferably, the spacing between the crawler running tracks is equal to the spacing between the crawler front wheels.

[0018] A method for identifying the flow pattern of a gas-liquid two-phase flow, using the detection device for identifying the flow pattern of a gas-liquid two-phase flow as described above, specifically comprises the following steps:

[0019] Step 1: Fix the crawler track to the outer wall of the pipeline to be inspected, then install the crawler on the crawler track and place it at the 0 o'clock position of the pipeline to be inspected;

[0020] Step 2: Turn on the controller and use it to control the crawler to move along the crawler travel track. The crawler stops after moving to the position to be inspected, and the position of the crawler on the pipeline to be inspected at this time is recorded. The controller controls the coupling agent application device to move along the first motion track to the inspection point. Then, the controller controls the retractable connecting rod connected to the coupling agent application device so that the coupling agent application device is in close contact with the outer wall of the pipeline. The coupling agent application device applies coupling agent to the inspection point.

[0021] Step 3: After the coupling agent is applied, the controller is used to control the coupling agent application device to move along the first motion track to the side of the first motion track close to the front wheel;

[0022] Step 4: Using a controller, the ultrasonic detection probe is controlled to move along the first motion track to the detection point for ultrasonic detection, and an echo signal at the detection point is obtained. At the same time, the controller controls the camera to move along the second motion track to a position parallel to the ultrasonic detection probe, and records the ultrasonic detection process. The ultrasonic detection probe is then controlled to move along the first motion track to the side of the first motion track close to the rear wheel to complete the ultrasonic detection of the detection point.

[0023] Step 5: Use the area between 0 o'clock and 6 o'clock on the outer wall of the pipeline as the detection area, use the controller to control the power motor 8 to drive the crawler to move slowly within the detection area, set multiple detection points in the detection area, measure each detection point separately, repeat steps 2 to 4, and obtain the echo signal at each detection point in the detection area;

[0024] Step 6: Obtain flow pattern discrimination parameters of the gas-liquid two-phase flow based on the echo signals at each detection point, including the mutation point, liquid film thickness, and echo characteristic curve stability; perform flow pattern identification based on the flow pattern discrimination parameters of the gas-liquid two-phase flow, and determine the flow pattern identification result;

[0025] Step 7: Print the interface shape according to the flow pattern recognition result, and output the results of the flow pattern recognition and interface shape printing.

[0026] Preferably, in step 4, ultrasonic detection is performed on the detection point using an ultrasonic detection probe, which specifically includes the following sub-steps:

[0027] Step 4.1: The pulse signal transmitted by the processor is amplified by the signal amplification circuit and the transformer component of the transmitting circuit, and then drives the ultrasonic detection probe to transmit ultrasonic waves;

[0028] Step 4.2: The ultrasonic wave emitted by the ultrasonic detection probe 1 encounters the target object, generating a reflected wave. The reflected wave returns along the original path and is absorbed by the ultrasonic detection probe 1 to generate a reflected signal.

[0029] Step 4.3: The reflected signal is amplified by the same-direction frequency-selective amplifier circuit, the filter amplifier circuit, and the shaping circuit of the receiving circuit, and then transmitted to the display circuit. After the waveform is recorded by the waveform recording module, it is displayed on the display screen.

[0030] Preferably, in step 6, the mutation point is determined based on the ultrasonic echo curve. When the ultrasonic detection probe moves along the circumferential direction of the pipeline, when the echo characteristic curve displayed on the oscilloscope undergoes a mutation, it indicates that the interface in the pipeline at this 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, and this position is determined to be the mutation point.

[0031] Preferably, in step 6, the liquid film thickness is determined based on the time interval Δt between the wall thickness echo and the interface echo reaching the receiving probe and the propagation velocity v of the ultrasonic wave in the liquid phase. 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.

[0032] Preferably, in step 6, if the interface results identified at the same position each time are different, it means that the interface state at that position is unstable, and the flow type in the pipe is slug flow or wavy stratified flow.

[0033] Preferably, the distinction between the slug flow and the wavy stratified flow 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 each time at the same position is different, and this feature appears in the entire detection area; the gas-liquid interface of the wavy stratified flow is composed of several periodic sinusoidal curves, and the interface shape shows a periodic change pattern with the vibration of the sine wave, and the mutation point only moves up and down within a certain range.

[0034] Preferably, in step 6, when identifying the gas-liquid two-phase flow pattern according to the gas-liquid two-phase flow pattern discrimination parameter, the identification characteristics of each flow pattern are:

[0035] The identification characteristics of slug flow are: the detection results at the same location in the entire detection area are different, and the echo characteristic curve changes with time;

[0036] The identification characteristics of annular flow are: there is no mutation point, the entire detection area is a solid-liquid interface, the liquid film thickness at each location is not zero, and the echo curve does not change with time;

[0037] The identification characteristics of flat laminar flow are: the presence of a mutation point, the liquid film thickness at the mutation point is 0, the height of the mutation point is equal to the liquid film thickness at the 6 o'clock position of the pipe, and the echo curve is stable;

[0038] The identification characteristics of curved laminar flow are: the presence of a mutation point, the liquid film thickness at the mutation point is 0, the height of the mutation point is not equal to the liquid film thickness at the 6 o'clock position of the pipe, and the echo curve is stable;

[0039] The identification characteristics of annular laminar flow are: the presence of a mutation point, the liquid film thickness at the mutation point is not zero, 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;

[0040] The identification characteristics of wavy laminar flow are: there is a mutation point, but the position of the mutation point is always changing, the range of change is limited, and the detection results of the liquid film height at the 6 o'clock direction of the pipeline are also different each time.

[0041] Preferably, in the step 7, during the interface shape printing process, for slug flow, its shape cannot be determined, and only the flow type needs to be identified, without the need to print the interface shape;

[0042] For annular flow, the shape of the right half of the interface is determined based on the liquid film thickness at the 0 o'clock, 3 o'clock, and 6 o'clock positions of the pipeline;

[0043] For flat laminar flow, curved laminar flow, and annular laminar flow, the interface shape is determined based on the liquid film thickness at the mutation point and the 6 o'clock position of the pipe;

[0044] For wavy laminar flow, the peak and trough positions of the sine wave are determined through multiple tests, and the sine wave period and the interface shape inside the pipe are determined based on the dynamic changes of the mutation point.

[0045] Preferably, since the interface shape of the 6 o'clock to 12 o'clock area inside the tube is symmetrical with the interface shape of the 0 o'clock to 6 o'clock area, the interface shape of the 6 o'clock to 12 o'clock area is drawn according to the interface shape of the 0 o'clock to 6 o'clock area, the complete interface shape is determined, and the drawing of the interface shape inside the entire tube is completed.

[0046] The beneficial technical effects brought about by the present invention are:

[0047] 1. The present invention proposes a detection device for identifying the flow pattern of gas-liquid two-phase flow. The device uses a crawler to drive the ultrasonic detection probe to move circumferentially along the outer wall of the pipeline, avoiding damage to the pipe wall structure due to detection. At the same time, by controlling the crawler to adjust the detection position of the ultrasonic detection probe, the accuracy of the ultrasonic detection probe's detection results is improved, providing accurate discrimination parameters for identifying the flow pattern of gas-liquid two-phase flow in the pipeline.

[0048] 2. The present invention also proposes a method for identifying the flow pattern of gas-liquid two-phase flow. Compared with the existing technology, which mainly focuses on the research of horizontal liquid level detection methods represented by flat laminar flow, there is little research on the gas-liquid interface morphology of flow patterns such as annular flow, curved laminar flow, and wavy laminar flow. The method of the present invention realizes the identification of laminar flow patterns such as slug flow, annular flow, flat laminar flow, curved laminar flow, annular laminar flow and wavy laminar flow. At the same time, by accurately characterizing the two-phase interface shapes of different flow patterns, it solves the problems of incomplete flow pattern identification, incomplete interface shape characterization, and low accuracy of interface morphology characterization in the existing technology.

[0049] 3. The present invention fills the gap in the field of laminar flow pattern identification and interface shape characterization of different interface shapes, has broad application prospects, and is conducive to the identification of two-phase flow patterns inside oil and gas pipelines and the judgment of liquid accumulation inside oil and gas pipelines. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 The figure is a schematic structural diagram of a detection device for identifying the flow pattern of gas-liquid two-phase flow according to the present invention.

[0051] Figure 2 This is a top view of a detection device for identifying the flow pattern of a gas-liquid two-phase flow according to the present invention; the direction indicated by the arrow in the figure is the movement direction of the camera.

[0052] Figure 3 Schematic diagram of the structure of the controller of the present invention.

[0053] Figure 4 These are the flow pattern diagrams of the gas-liquid two-phase flow of the present invention; among them, (a) is the flow pattern diagram of annular flow, (b) is the flow pattern diagram of flat laminar flow, (c) is the flow pattern diagram of annular laminar flow, (d) is the flow pattern diagram of curved laminar flow, and (e) is the flow pattern diagram of wavy laminar flow.

[0054] Figure 5 The present invention is a flow chart of a method for identifying the flow pattern of gas-liquid two-phase flow.

[0055] In the figure: 1. Ultrasonic detection probe, 2. Couplant coating device, 3. Camera, 4. Bottom plate, 5. Fixed bracket, 6. Front wheel, 7. Rear wheel, 8. Power motor, 9. Detection port, 10. Fixed rod, 11. First moving track, 12. Second moving track, 13. Retractable connecting rod. DETAILED DESCRIPTION

[0056] The present invention is further described in detail below with reference to the accompanying drawings and embodiments.

[0057] The present invention proposes a detection device for identifying the flow pattern of a gas-liquid two-phase flow, which comprises a crawler, a controller and a pair of crawler travel guide rails.

[0058] The crawler includes a vehicle body and an ultrasonic detection probe 1, a coupling agent coating device 2 and a camera 3 arranged on the vehicle body. The ultrasonic detection probe 1 is used to perform ultrasonic detection on the pipeline, the coupling agent coating device 2 is used to apply coupling agent on the pipe wall, and the camera 3 is used to monitor the positions of the ultrasonic detection probe and the coupling agent coating device, so that the coupling agent coating device and the ultrasonic detection probe can be accurately moved to the position to be detected during the detection process. Figure 1 and Figure 2 As shown, the crawler body includes a base plate 4 and a fixed bracket 5. The bottom of the base plate 4 is equipped with a pair of front wheels 6 and a pair of rear wheels 7. The front wheels 6 and the rear wheels 7 are magnetic wheels that can be fixed on the crawler's travel guide rails to achieve fixed-point measurement of the outer wall of the pipeline. The rear wheels 7 are connected to a power motor 8, which is arranged on a transmission rod used to connect the two rear wheels to provide power for the movement of the crawler. A detection port 9 is provided at the center of the base plate 4. The detection port is used to extend the ultrasonic detection probe, coupling agent application device and camera from the interior of the body. A fixed bracket 5 is provided on the top surface of the base plate 4. A pair of fixed columns of the fixed bracket 5 are separated on both sides of the detection port and connected by a fixed rod 10. A first motion track 11 and a second motion track 12 are fixed on the fixed rod 10. The first motion track 11 and the second motion track 12 are arranged parallel to each other above the detection port 9, and the axial direction of the first motion track 11 is perpendicular to the axial direction of the fixed rod 10. The ultrasonic detection probe 1 and the coupling agent application device 2 are respectively slidably connected to the first motion track 11 through a retractable connecting rod 13. The ultrasonic detection probe 1 is located on the side of the first motion track 11 close to the rear wheel 7, and the coupling agent application device 2 is located on the side of the first motion track 11 close to the front wheel 6. The camera 3 is slidably connected to the second motion track 12 through the retractable connecting rod 13 and is located on the side of the second motion track 12 close to the rear wheel 7. The retractable connecting rod 13 can control the position of the connected device by telescoping. The ultrasonic detection probe 1, the coupling agent application device 2, the camera 3, the power motor 8 and the retractable connecting rod 13 are all connected to the controller.

[0059] The controller includes an ultrasonic signal excitation and processing system, a processor, a display circuit and a power supply circuit, such as Figure 3 As shown, the ultrasonic signal excitation and processing device includes a transmitting circuit and a receiving circuit, wherein the transmitting circuit includes a signal amplification circuit and a transformer assembly, the receiving circuit includes a same-direction frequency-selective amplification circuit, a filtering amplification circuit and a shaping circuit, and the display circuit includes a waveform recording module and a display; the transmitting circuit is located between the processor and the ultrasonic detection probe, one end of the transmitting circuit is connected to the ultrasonic detection probe, and the other end is connected to the processor after passing through the same-direction frequency-selective amplification circuit, the filtering amplification circuit and the shaping circuit in sequence, the signal processed by the processor is input into the waveform recording module of the display circuit, the waveform recording module records the acquired signal and displays it on the display screen of the display circuit, the ultrasonic signal excitation and processing system, the processor, and the display circuit are all connected to the power supply circuit, and the power supply circuit is used to power all parts in the controller.

[0060] The crawler's travel track is arranged along the circumference of the pipeline and is tightly attached to the outer wall of the pipeline. Magnets are embedded on the inner side of the crawler's travel track. The front wheels 6 and rear wheels 7 of the crawler are both embedded in the crawler's travel track. The magnets generate magnetic force on the crawler's magnetic wheels. When the power motor 8 does not apply power to the crawler, the crawler can overcome the influence of its own gravity and be fixed on the outer wall of the pipeline under the action of the magnetic force. The crawler's magnetic wheels remain stationary after being adsorbed and fixed by the magnet, effectively preventing the crawler from falling. The crawler can be controlled to move along the crawler's travel track by controlling the power motor 8 using a controller.

[0061] The present invention also proposes a method for identifying the flow pattern of gas-liquid two-phase flow, such as Figure 5 As shown, the above-mentioned detection device for identifying the flow pattern of gas-liquid two-phase flow includes the following steps:

[0062] Step 1: Fix the crawler running track to the outer wall of the pipeline to be inspected, then install the crawler on the crawler running track and place it at the 0 o'clock position of the pipeline to be inspected.

[0063] Step 2: Turn on the controller and record the position of the crawler on the pipeline to be inspected. Use the controller to control the coupling agent application device 2 to move along the first motion track to the inspection point. Then use the controller to control the retractable connecting rod 13 connected to the coupling agent application device 2 so that the coupling agent application device 2 is in close contact with the outer wall of the pipeline. The coupling agent application device 2 applies the coupling agent at the inspection point.

[0064] Step 3: After the coupling agent is applied, the controller is used to control the coupling agent applying device 2 to move along the first motion track 11 to the side of the first motion track 11 close to the front wheel 6.

[0065] Step 4: Use the controller to control the ultrasonic detection probe 1 to move along the first motion track 11 to the detection point for ultrasonic detection. At the same time, the controller controls the camera 3 to move along the second motion track 12 to a position parallel to the ultrasonic detection probe 1 to record the ultrasonic detection process. The ultrasonic detection process includes the following steps:

[0066] In step 4.1, the processor transmits a 200 MHz pulse signal, which is amplified by the signal amplification circuit and transformer assembly of the transmitting circuit and then drives the ultrasonic detection probe to transmit ultrasonic waves.

[0067] Step 4.2: When the ultrasonic wave emitted by the ultrasonic detection probe encounters the target object, it is reflected and then returns along the original path. The ultrasonic detection probe absorbs the reflected wave and generates a reflected signal.

[0068] In step 4.3, since the energy of the ultrasonic wave is constantly absorbed and attenuated during the propagation 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 co-directional frequency selection amplification, filtering amplification, and shaping operations on the reflected signal. A co-phase AC amplifier circuit is selected to amplify the 200MHz frequency band, and a secondary amplification is performed through a filtering amplifier circuit. A shaping circuit is used to solve the tailing problem of the transmitting circuit, prevent the tail wave from being coupled into the recovered wave, and improve the measurement accuracy.

[0069] The signal amplified by the receiving circuit's same-direction frequency-selective amplifier circuit, filtering amplifier circuit and shaping circuit is transmitted to the display circuit, and after the waveform is recorded by the waveform recording module, it is displayed on the display screen.

[0070] The ultrasonic detection probe is used to measure the echo signal at the detection point, and the ultrasonic detection probe is controlled to move along the first motion track 11 to the side of the first motion track 11 close to the rear wheel 7 to complete the ultrasonic detection of the detection point.

[0071] In step 5, the area between 0 o'clock and 6 o'clock on the outer wall of the pipe is used as the detection area. The controller controls the power motor 8 to drive the crawler to move slowly in the detection area. Multiple detection points are set in the detection area, including the 3 o'clock and 6 o'clock positions on the pipe wall. Measurements are taken at each detection point respectively. Steps 2 to 4 are repeated to obtain the echo signals at each detection point in the detection area.

[0072] Step 6: Obtain the flow pattern discrimination parameters of the gas-liquid two-phase flow based on the echo signals at each detection point. The flow pattern discrimination parameters of the gas-liquid two-phase flow include the mutation point, the liquid film thickness, and the stability of the echo characteristic curve. The process of determining the flow pattern discrimination parameters of the gas-liquid two-phase flow is as follows:

[0073] Regarding the mutation point, due to the different reflection coefficients of ultrasound at the solid-gas interface and the solid-liquid interface, the attenuation of the wall thickness echo of the same number will vary. The attenuation rate of the solid-liquid interface is faster than that of the solid-gas interface. As the number of echoes increases, the difference between the ultrasonic echo characteristic curves of the two interfaces will become more and more obvious. In addition, when the internal interface is a solid-liquid interface, the echo characteristic curve is composed of the wall thickness echo and the gas-liquid interface echo in the tube, while when the internal interface is a solid-gas interface, the echo characteristic curve is composed of the wall thickness echo. Therefore, when the echo characteristic curve on the oscilloscope undergoes a mutation (hereinafter referred to as the mutation point) during the movement of the ultrasonic detection probe, it indicates that the internal interface at that location 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.

[0074] Regarding liquid film thickness, the film thickness at that location is 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 interpretation, the wall thickness echo cycle is first calculated based on the pipe thickness and the ultrasonic wave propagation velocity in the pipe metal. The waveform changes are then observed. When the waveform on the display begins to display irregular shapes and become disorganized, it indicates that the interface echo has returned to the receiving probe. Therefore, the liquid film thickness at the detection location is determined as h, based on the time interval Δt between the wall thickness echo and the interface echo reaching the receiving probe and the ultrasonic wave propagation velocity v in the liquid phase. If no interface echo signal is detected, the liquid film thickness at that location is zero.

[0075] Regarding the stability of the echo characteristic curve, if the interface results identified each time at the same position are different, it means that the interface state at that position is unstable, and the flow state in the pipe may be slug flow or wavy stratified flow; further distinction is made between slug flow and wavy stratified flow. In slug flow, the gas-liquid phase distribution characteristics on the cross section of the pipe are constantly changing, and the interface identified each time at the same position is different. This feature appears in the entire detection area; the gas-liquid interface of wavy stratified flow is composed of several periodic sinusoidal curves, and the interface shape shows a periodic change law with the vibration of the sine wave, and the mutation point only moves up and down within a certain range.

[0076] Flow pattern identification is performed based on the flow pattern discrimination parameters of the gas-liquid two-phase flow, and the flow pattern identification results are determined. The identification characteristics of each flow pattern are:

[0077] The identification characteristics of slug flow are: the detection results at the same location in the entire detection area are different, and the echo characteristic curve changes with time.

[0078] The identification characteristics of annular flow are: 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.

[0079] The identification characteristics of flat laminar flow are: there is a mutation point, the liquid film thickness at the mutation point is 0, 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.

[0080] The identification characteristics of curved laminar flow are: there is a mutation point, the liquid film thickness at the mutation point is 0, 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.

[0081] The identification characteristics of annular laminar flow are: the existence of a mutation point, the liquid film thickness at the mutation point is not 0, 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.

[0082] The identification characteristics of wavy laminar flow are: there is a mutation point, but the position of the mutation point is always changing, the range of change is limited, and the detection results of the liquid film height at the 6 o'clock direction of the pipeline are also different each time.

[0083] Step 7: Print the interface shape based on the flow pattern recognition results. For slug flow, its shape cannot be determined, so only the flow pattern needs to be identified and no interface shape printing is required. For annular flow, the shape of the right half of the interface is determined based on the liquid film thickness at the 0 o'clock, 3 o'clock, and 6 o'clock positions of the pipeline. For flat laminar flow, curved laminar flow, and annular laminar flow, the interface shape is determined based on the liquid film thickness at the mutation point and the 6 o'clock position of the pipeline. For wavy laminar flow, the peak and trough positions of the sine wave are determined through multiple tests, and the sine wave period is determined based on the dynamic changes of the mutation point to determine the interface shape inside the pipe.

[0084] After drawing the interface shape of the 0 o'clock to 6 o'clock area, the interface shape of the 6 o'clock to 12 o'clock area is supplemented according to the interface shape of the 0 o'clock to 6 o'clock area to obtain a complete interface shape, and the results of flow pattern recognition and interface shape printing are output.

[0085] Example 1

[0086] The method of the present invention is used to identify annular laminar flow. The identification method is as follows: 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.

[0087] The interface characterization process is: 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 as follows: Figure 4 As shown in (a).

[0088] Example 2

[0089] The method of the present invention is used to identify flat laminar flow. The identification method is as follows: there is a mutation point, the liquid film thickness at the mutation point is 0, and 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.

[0090] The interface characterization process is as follows: 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, and complete the left half according to the principle of symmetry about the line connecting 0 o'clock and 6 o'clock. The interface shape is as follows Figure 4 (b) shown.

[0091] Example 3

[0092] The method of the present invention is used to identify annular laminar flow. The identification method is as follows: there is a mutation point, the liquid film thickness at the mutation point is not 0, 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.

[0093] The interface characterization process is: 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 as follows Figure 4 (c) shown.

[0094] Example 4

[0095] The method of the present invention is used to identify curved laminar flow. The identification method is as follows: there is a mutation point, the liquid film thickness at the mutation point is 0, the height of the mutation point position is not equal to the liquid film thickness at 6 o'clock position, and the echo curve is stable.

[0096] The interface characterization process is as follows: 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, and complete the left half according to the principle of symmetry about the line connecting 0 o'clock and 6 o'clock. The interface shape is as follows Figure 4 (d) shown.

[0097] Example 5

[0098] The method of the present invention is used to identify wavy laminar flow. The identification method 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 6 o'clock are also different each time.

[0099] The interface characterization process is as follows: through multiple tests, the peak and trough positions of the sine wave are determined, 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 as follows: Figure 4 (e) shown.

[0100] Example 6

[0101] When the method of the present invention is used to identify slug flow, the detection results at the same position in the entire detection area are different, and the echo characteristic curve changes with time.

[0102] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "disposed," "installed," "connected," "connected," and "fixed" should be understood in a broad sense. For example, they may refer to fixed connections, detachable connections, or integral connections; they may refer to mechanical connections or electrical connections; they may refer to direct connections or indirect connections through an intermediate medium; and they may refer to internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0103] Of course, the above description is not a limitation of the present invention, and the present invention is not limited to the above examples. Changes, modifications, additions or substitutions made by technicians in this technical field within the essential scope of the present invention should also fall within the scope of protection of the present invention.

Claims

1. A detection device for identifying the flow pattern of gas-liquid two-phase flow, characterized in that: It includes a crawler, a controller and a pair of crawler travel rails; The crawler comprises a vehicle body and an ultrasonic detection probe (1), a coupling agent coating device (2) and a camera (3) arranged on the vehicle body; the vehicle body comprises a bottom plate (4) and a fixed bracket (5); the bottom of the bottom plate (4) is equipped with a pair of front wheels (6) and a pair of rear wheels (7); the front wheels (6) and the rear wheels (7) are magnetic wheels; the rear wheels (7) are connected to a power motor (8); a detection port (9) is provided at the center of the bottom plate (4); and a fixed bracket (5) is provided on the top surface of the bottom plate (4); a pair of fixed columns of the fixed bracket (5) are separated on both sides of the detection port (9) and are connected by a fixed rod (10); a first motion track (11) and a second motion track (12) are provided in parallel on the fixed rod (10); the first motion track (11) and the second motion track (12) are provided in parallel. ) are both located above the detection port (9), and the axial direction of the first motion track (11) is perpendicular to the axial direction of the fixed rod (10); the ultrasonic detection probe (1) and the coupling agent smearing device (2) are respectively slidably connected to the first motion track (11) through a telescopic connecting rod (13); the ultrasonic detection probe (1) is located on the side of the first motion track (11) close to the rear wheel (7), the coupling agent smearing device (2) is located on the side of the first motion track (11) close to the front wheel (6), the camera is slidably connected to the second motion track (12) through a telescopic connecting rod (13), and is located on the side of the second motion track (12) close to the rear wheel (7), and the ultrasonic detection probe (1), the coupling agent smearing device (2), the camera (3), the power motor (8) and the telescopic connecting rod (13) are all connected to the controller; The crawler travel track is arranged along the circumference of the pipeline and is in close contact with the outer wall of the pipeline. A magnet is embedded on the inner side of the crawler travel track. The front wheel (6) and the rear wheel (7) of the crawler are both embedded in the crawler travel track and are slidably connected to the crawler travel track.

2. According to claim 1, a detection device for identifying the flow type of gas-liquid two-phase flow, the controller includes an ultrasonic signal excitation and processing system, a processor, a display circuit and a power supply circuit, the ultrasonic signal excitation and processing device includes a transmitting circuit and a receiving circuit, one end of the transmitting circuit is connected to the ultrasonic detection probe (1), and the other end is connected to the processor through the receiving circuit, the signal processed by the processor is input into the waveform recording module of the display circuit, the waveform recording module records the acquired signal and displays it on the display screen of the display circuit, the ultrasonic signal excitation and processing system, the processor, and the display circuit are all connected to the power supply circuit.

3. A detection device for identifying the flow pattern of gas-liquid two-phase flow according to claim 2, characterized in that: The transmitting circuit includes a signal amplifying circuit and a transformer component.

4. A detection device for identifying the flow pattern of gas-liquid two-phase flow according to claim 2, characterized in that: The receiving circuit includes a same-direction frequency-selective amplifier circuit, a filter amplifier circuit and a shaping circuit.

5. The detection device for identifying the flow pattern of gas-liquid two-phase flow according to claim 1, characterized in that: The spacing between the crawler running tracks is equal to the spacing between the crawler front wheels (6).

6. A method for identifying the flow pattern of a gas-liquid two-phase flow, characterized in that: The detection device for identifying the flow pattern of a gas-liquid two-phase flow according to any one of claims 1 to 5 specifically comprises the following steps: Step 1: Fix the crawler track to the outer wall of the pipeline to be inspected, then install the crawler on the crawler track and place it at the 0 o'clock position of the pipeline to be inspected; Step 2: Turn on the controller and use the controller to control the crawler to move along the crawler travel track. The crawler stops after moving to the position to be detected, and the position of the crawler on the pipeline to be detected at this time is recorded. The controller is used to control the coupling agent smearing device (2) to move along the first motion track (11) to the detection point. Then, the controller is used to control the retractable connecting rod (13) connected to the coupling agent smearing device (2) so that the coupling agent smearing device (2) is in close contact with the outer wall of the pipeline. The coupling agent smearing device (2) smears the coupling agent at the detection point. Step 3: After the coupling agent is applied, the controller is used to control the coupling agent applying device (2) to move along the first motion track (11) to the side of the first motion track (11) close to the front wheel (6); Step 4, using a controller to control the ultrasonic detection probe (1) to move along the first motion track (11) to a detection point to perform ultrasonic detection, and obtain an echo signal at the detection point. At the same time, the controller controls the camera (3) to move along the second motion track (12) to a position parallel to the ultrasonic detection probe (1), records the ultrasonic detection process, and then controls the ultrasonic detection probe (1) to move along the first motion track (11) to the side of the first motion track (11) close to the rear wheel (7), and completes the ultrasonic detection of the detection point. Step 5: Using the area between 0 o'clock and 6 o'clock on the outer wall of the pipeline as the detection area, the controller controls the power motor (8) to drive the crawler to move slowly within the detection area, and multiple detection points are set within the detection area. Measurements are taken at each detection point respectively, and steps 2 to 4 are repeated to obtain echo signals at each detection point within the detection area; Step 6: Obtain flow pattern discrimination parameters of the gas-liquid two-phase flow based on the echo signals at each detection point, including the mutation point, liquid film thickness, and echo characteristic curve stability; perform flow pattern identification based on the flow pattern discrimination parameters of the gas-liquid two-phase flow, and determine the flow pattern identification result; Step 7: Print the interface shape according to the flow pattern recognition result, and output the results of the flow pattern recognition and interface shape printing.

7. The method for identifying the flow pattern of gas-liquid two-phase flow according to claim 6, characterized in that: In step 4, ultrasonic detection is performed on the detection point using an ultrasonic detection probe, which specifically includes the following sub-steps: Step 4.1: The pulse signal transmitted by the processor is amplified by the signal amplification circuit and the transformer component of the transmitting circuit, and then drives the ultrasonic detection probe to transmit ultrasonic waves; Step 4.2, the ultrasonic wave emitted by the ultrasonic detection probe (1) encounters the target object, and is emitted to form a reflected wave, which returns along the original path and is absorbed by the ultrasonic detection probe (1) to generate a reflected signal; Step 4.3: The reflected signal is amplified by the same-direction frequency-selective amplifier circuit, the filter amplifier circuit, and the shaping circuit of the receiving circuit, and then transmitted to the display circuit. After the waveform is recorded by the waveform recording module, it is displayed on the display screen.

8. The method for identifying the flow pattern of gas-liquid two-phase flow according to claim 6, characterized in that: In step 6, the mutation point is determined based on the ultrasonic echo curve. When the ultrasonic detection probe moves along the circumferential direction of the pipeline, when the echo characteristic curve displayed on the oscilloscope undergoes a mutation, the interface in the pipeline at the surface 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 position is the critical point between the solid-liquid interface and the solid-gas interface, and this position is determined to be the mutation point.

9. The method for identifying the flow pattern of gas-liquid two-phase flow according to claim 6, characterized in that: In step 6, the liquid film thickness is determined based on the time interval Δt between the wall thickness echo and the interface echo reaching the receiving probe and the ultrasonic wave propagation velocity v in the liquid phase. 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.

10. The method for identifying the flow pattern of gas-liquid two-phase flow according to claim 6, characterized in that: In step 6, if the interface results identified at the same position are different each time, it means that the interface state at the position is unstable and the flow type in the pipe is slug flow or wavy stratified flow.

11. The method for identifying the flow pattern of gas-liquid two-phase flow according to claim 10, characterized in that: The distinction between slug flow and wavy stratified flow is based on the following: In slug flow, the gas-liquid phase distribution characteristics on the cross-section of the pipe constantly change, so the interface identified at the same location is different each time, and this characteristic appears throughout the entire detection area; in wavy stratified flow, the gas-liquid interface is composed of several periodic sinusoidal curves, and the interface shape shows a periodic change pattern with the vibration of the sine wave, and the mutation point only moves up and down within a certain range.

12. The method for identifying the flow pattern of gas-liquid two-phase flow according to claim 6, characterized in that: In step 6, when identifying the gas-liquid two-phase flow pattern according to the gas-liquid two-phase flow pattern discrimination parameters, the identification characteristics of each flow pattern are: The identification characteristics of slug flow are: the detection results at the same location in the entire detection area are different, and the echo characteristic curve changes with time; The identification characteristics of annular flow are: there is no mutation point, the entire detection area is a solid-liquid interface, the liquid film thickness at each location is not zero, and the echo curve does not change with time; The identification characteristics of flat laminar flow are: the presence of a mutation point, the liquid film thickness at the mutation point is 0, the height of the mutation point is equal to the liquid film thickness at the 6 o'clock position of the pipe, and the echo curve is stable; The identification characteristics of curved laminar flow are: the presence of a mutation point, the liquid film thickness at the mutation point is 0, the height of the mutation point is not equal to the liquid film thickness at the 6 o'clock position of the pipe, and the echo curve is stable; The identification characteristics of annular laminar flow are: the presence of a mutation point, the liquid film thickness at the mutation point is not zero, 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 characteristics of wavy laminar flow are: there is a mutation point, but the position of the mutation point is always changing, the range of change is limited, and the detection results of the liquid film height at the 6 o'clock direction of the pipeline are also different each time.

13. The method for identifying the flow pattern of gas-liquid two-phase flow according to claim 6, characterized in that: In step 7, during the interface shape printing process, for slug flow, its shape cannot be determined, and only the flow type needs to be identified, without the need for interface shape printing; For annular flow, the shape of the right half of the interface is determined based on the liquid film thickness at the 0 o'clock, 3 o'clock, and 6 o'clock positions of the pipeline; For flat laminar flow, curved laminar flow, and annular laminar flow, the interface shape is determined based on the liquid film thickness at the mutation point and the 6 o'clock position of the pipe; For wavy laminar flow, the peak and trough positions of the sine wave are determined through multiple tests, and the sine wave period and the interface shape inside the pipe are determined based on the dynamic changes of the mutation point.

14. The method for identifying the flow pattern of gas-liquid two-phase flow according to claim 13, characterized in that: Since the interface shape of the 6 o'clock to 12 o'clock area in the tube is symmetrical with the interface shape of the 0 o'clock to 6 o'clock area, the interface shape of the 6 o'clock to 12 o'clock area is drawn according to the interface shape of the 0 o'clock to 6 o'clock area, the complete interface shape is determined, and the drawing of the interface shape of the entire tube is completed.

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