A device and method for measuring gas holdup of gas-liquid two-phase flow in a circular pipe

Abstract

The present application belongs to a kind of gas rate measuring device and measuring method, for the gas-liquid two-phase flow cross section gas rate measuring method in existing round pipe, to the high requirement of round pipe material, for the gas-liquid disturbance intense flow type such as slug flow, stirring flow, the gas rate measuring precision of lower, it is difficult to realize the technical problem of industrial application, provide a kind of gas-liquid two-phase flow cross section gas rate measuring device and measuring method in round pipe, main pipeline is connected at the cross section to be measured of the measured round pipe at both ends, under the condition that not affecting the gas-liquid two-phase fluid working condition in round pipe, can carry out real-time measurement to the cross section gas rate of gas-liquid two-phase fluid at cross section to be measured.Main pipeline is provided with flow pattern adjustment device, different flow pattern gas-liquid two-phase fluid can be adjusted to the annular flow or gas column flow of gas-liquid two-phase uniform distribution, then through infrared measuring device, different flow pattern incoming gas-liquid two-phase flow cross section gas rate can be realized on-line measurement, suitable for the cross section gas rate measuring demand of different incoming flow pattern.

Description

Technical Field

[0001] This invention relates to a gas content measuring device and method, specifically to a gas content measuring device and method for a cross-section of a gas-liquid two-phase flow in a circular tube. Background Technology

[0002] Gas-liquid two-phase flow is widely present in natural environments and engineering applications. Among them, gas-liquid two-phase flow within circular pipes is widely used in the petroleum and chemical industries. Accurately determining the gas holdup of the cross-section of a gas-liquid two-phase flow system within a circular pipe is of great significance for the operation, optimization, and monitoring of gas-liquid two-phase flow systems in industry.

[0003] Based on different measurement principles, existing technologies for measuring the gas holdup of gas-liquid two-phase flow sections mainly include the fast-closing valve method, conductivity method, X-ray method, optical method, and process tomography. The fast-closing valve method approximates the cross-sectional phase holdup by measuring the volumetric phase holdup and is mainly used for calibrating measuring devices, but it cannot meet the requirements of real-time, online measurement. The conductivity method can only be applied to conductive fluids, and the probe's penetration into the tube during measurement inevitably affects the flow field, causing measurement deviations. The X-ray method is a mature measurement method, but it involves safety issues such as radiation protection, radioactive source storage, and equipment maintenance. The process tomography method has the advantage of non-invasive measurement; however, the measurement results are highly dependent on the accuracy of the image reconstruction algorithm, and the measurement effect can only be guaranteed at low gas holdup levels. Optical methods based on visible light have high measurement accuracy, but optical measuring equipment is generally expensive, the operation process is complex, and strict requirements are placed on the cleanliness of the measured medium and the application environment. Currently, the measurement of the gas holdup of gas-liquid two-phase flow sections in circular tubes mainly adopts optical measurement methods based on near-infrared light, which can achieve online measurement. However, it is only suitable for measuring the gas content of two-phase gas-liquid flow in transparent plexiglass pipes that do not have pressure-bearing capacity. In addition, the gas content measurement accuracy is low for flow patterns with severe gas-liquid disturbances, such as slug flow and stirred flow, making it difficult to implement in industrial applications. Summary of the Invention

[0004] This invention addresses the technical problems of existing methods for measuring the gas content of gas-liquid two-phase flow cross-sections in circular pipes, which have high requirements for the material of the circular pipe and low measurement accuracy for flow patterns with severe gas-liquid disturbances such as slug flow and stirred flow, making it difficult to achieve industrial applications. The invention provides a device and method for measuring the gas content of gas-liquid two-phase flow cross-sections in circular pipes.

[0005] To achieve the above objectives, the present invention employs the following technical solution:

[0006] A device for measuring the gas content of a cross-section in a circular tube for gas-liquid two-phase flow includes:

[0007] A bypass pipe is provided, with both ends connected to the main pipe. Along the flow direction of the gas-liquid two-phase fluid, the upstream connection is denoted as A, and the downstream connection is denoted as B. A third switch is provided near A and a fourth switch is provided near B in the bypass pipe.

[0008] The main pipeline is connected at both ends to the cross-section of the circular pipe to be measured, and the main pipeline is coaxial with the circular pipe to be measured. A flow pattern adjustment device, a first switch and a second switch are installed inside the main pipeline. The flow pattern adjustment device is located between the upstream end of the main pipeline and A, and is coaxial with the main pipeline. The first switch and the second switch are both located between A and B.

[0009] An infrared measuring device, wherein the measuring end of the infrared measuring device is positioned between the first and second switching components of the main pipeline;

[0010] The first and second venting components are both installed on the main pipeline, located between the first and second switch components, with the first venting component adjacent to the first switch component and the second venting component adjacent to the second switch component.

[0011] The data processing unit is used to acquire the input voltage and output voltage of the infrared measuring device, as well as the volumetric gas content between the first and second switching components in the main pipeline, and to calculate the infrared light intensity attenuation rate, the attenuation coefficient of infrared light in the liquid, and the attenuation coefficient of infrared light in the gas, so as to obtain the gas content of the gas-liquid two-phase flow section in the circular pipe.

[0012] Furthermore, the main pipeline has mounting holes on its side wall, and a transparent viewing window is sealed and installed at the mounting holes; the measuring end of the infrared measuring device includes an infrared light emitting probe and an infrared light receiving probe;

[0013] The infrared measuring device is installed on the outer wall of the main pipeline, with the infrared emitting probe and the infrared receiving probe located within the transparent viewing window.

[0014] Furthermore, the transparent window is made of aluminosilicate glass.

[0015] Furthermore, the flow pattern adjustment device is a swirl starter.

[0016] Furthermore, the first, second, third, and fourth switching components are all ball valves.

[0017] This invention also proposes a method for measuring the gas content of a cross-section in a circular pipe during gas-liquid two-phase flow. Based on the aforementioned device for measuring the gas content of a cross-section in a circular pipe during gas-liquid two-phase flow, the method is characterized by comprising the following steps:

[0018] S1, in the following two cases respectively:

[0019] Scenario 1: Turn on the third and fourth switches;

[0020] Case 2: Open the fourth switch, and at the same time, reduce the opening degree of the third switch compared to Case 1;

[0021] Obtain the difference between the input and output voltages of the infrared measuring device, the corresponding infrared light intensity attenuation rate, and the volumetric gas content between the first and second switching components:

[0022] The first and second switches are turned on, and the first and second venting devices are turned off, allowing the gas-liquid two-phase fluid to flow into the main pipeline and the bypass pipeline. At the same time, the flow pattern adjustment device makes the gas-liquid two-phase fluid form a flow pattern with a stable gas-liquid interface.

[0023] The data processing unit obtains the input voltage of the infrared measuring device, the difference between the input voltage and the output voltage, and calculates the infrared light intensity attenuation rate.

[0024] Close the first and second switches, open the first and second venting devices to discharge the gas and liquid between the first and second switches in the main pipeline, obtain the liquid volume, and calculate the current gas content between the first and second switches by combining the total volume between the first and second switches in the main pipeline.

[0025] S2, open the first and second switches, close the third and fourth switches, close the first and second venting devices, so that the gas-liquid two-phase fluid flows into the main pipeline. At the same time, the flow pattern adjustment device makes the gas-liquid two-phase fluid form a flow pattern with a stable gas-liquid interface.

[0026] The data processing unit obtains the input voltage of the infrared measuring device, the difference between the input voltage and the output voltage, and calculates the infrared light intensity attenuation rate.

[0027] S3. Based on the volumetric gas content between the first and second switching components obtained in step S1, and the corresponding infrared light intensity attenuation rate, calculate the attenuation coefficient of infrared light in liquid and the attenuation coefficient of infrared light in gas.

[0028] S4. Based on the attenuation coefficient of infrared light in liquid and the attenuation coefficient of infrared light in gas, as well as the infrared light intensity attenuation rate obtained in step S2, the gas content of the gas-liquid two-phase flow section inside the circular tube is calculated.

[0029] Furthermore, the infrared light intensity attenuation rate i is calculated using the following formula:

[0030]

[0031] Where a represents the photoelectric conversion slope coefficient, b represents the photoelectric conversion intercept coefficient, and ΔU represents the difference between the input voltage and the output voltage of the infrared measuring device. t This indicates the input voltage of the infrared measuring device.

[0032] Furthermore, the volumetric gas content β between the first and second switching elements is calculated using the following formula:

[0033]

[0034] Among them, V l V represents the volume of liquid discharged between the first and second switching components via the first and second venting components, and V represents the total volume between the first and second switching components in the main pipeline.

[0035] Further, in step S3, the attenuation coefficient of the infrared light in the liquid and the attenuation coefficient of the infrared light in the gas are calculated by the following formula:

[0036]

[0037]

[0038] Where, k l k represents the attenuation coefficient of infrared light in a liquid. g β1 represents the attenuation coefficient of infrared light in gas, D represents the inner diameter of the main pipe, i1 represents the infrared light intensity attenuation rate under case 1, i2 represents the infrared light intensity attenuation rate under case 2, β1 represents the volumetric gas content between the first and second switching components under case 1, and β2 represents the volumetric gas content between the first and second switching components under case 2.

[0039] Further, in step S4, the gas holdup of the gas-liquid two-phase flow section inside the circular tube is calculated using the following formula:

[0040]

[0041] Where φ represents the gas content of the cross section of the gas-liquid two-phase flow inside the circular tube.

[0042] Compared with the prior art, the present invention has the following beneficial effects:

[0043] 1. This invention proposes a device for measuring the gas holdup of a gas-liquid two-phase flow section in a circular pipe. The main pipe is connected at both ends to the section to be measured in the circular pipe. Without affecting the operating conditions of the gas-liquid two-phase fluid within the pipe, the device can measure the gas holdup at the section to be measured in real time. A flow pattern adjustment device is installed inside the main pipe, which can adjust gas-liquid two-phase fluids of different flow patterns into a uniformly distributed annular flow or gas column flow. Then, using an infrared measuring device, online measurement of the gas holdup of the gas-liquid two-phase flow section with different flow patterns can be achieved, avoiding the influence of the incoming flow pattern. There are no restrictions on the placement of the circular pipe during measurement; it can measure the gas holdup of the gas-liquid two-phase flow section in horizontal, vertical, or inclined circular pipes. The device is simple to operate, easy to implement, and has low measurement costs, and can directly guide actual production.

[0044] 2. In this invention, when the infrared measuring device is installed, a transparent viewing window is set at the corresponding position on the side wall of the main pipe, preferably aluminosilicate glass. The light-transmitting and pressure-bearing properties of aluminosilicate glass are utilized, and infrared light has good reflection properties on metal, which improves the measurement effect of the infrared measuring device when applied to opaque circular pipes.

[0045] 3. This invention also proposes a method for measuring the gas content of a cross-section in a circular pipe during gas-liquid two-phase flow. The measurement is achieved using the gas content measuring device for a cross-section in a circular pipe during gas-liquid two-phase flow according to this invention. During measurement, the gas content measuring device is directly connected to the circular pipe being measured. Considering the different fluid properties in various industrial applications and the influence of medium properties on the infrared light intensity attenuation rate, this invention first calibrates the correspondence between the light intensity attenuation rate of infrared light propagating in the gas-liquid fluid within the pipeline and the gas content of the gas-liquid two-phase flow cross-section under actual industrial pressure and temperature conditions. Then, the attenuation coefficients of the infrared light emitted by the infrared measuring device in the liquid and gas phases within the pipe are calculated. Finally, the gas content of the cross-section is measured based on the infrared attenuation coefficients. The measurement method is simple and highly accurate, less susceptible to external interference, has low requirements for the material of the circular pipe, and can achieve high-precision measurement for gas-liquid two-phase fluids of different flow patterns, showing broad industrial application prospects. Attached Figure Description

[0046] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0047] Figure 1 This is a schematic diagram of the structure of Embodiment 1;

[0048] Figure 2 This is a schematic diagram of the infrared measuring device in Example 2.

[0049] Among them: 1-Main pipe, 2-Bypass pipe, 3-Flow pattern adjustment device, 4-Fixed bracket, 5-Infrared measuring device, 6-First venting component, 7-Second venting component, 8-First switch component, 9-Second switch component, 10-Flange, 11-Third switch component, 12-Fourth switch component, 13-Infrared light emitting probe, 14-Infrared light receiving probe, 15-Transparent window, 16-Power interface, 17-Analog signal interface, 18-Data processing unit. Detailed Implementation

[0050] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0051] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0052] In the description of the embodiments of the present invention, it should be noted that if terms such as "upper," "lower," "horizontal," or "inner" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of the invention is in use, they are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention. Furthermore, terms such as "first" and "second" are only used to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0053] Furthermore, the use of the term "horizontal" does not imply that the component must be absolutely horizontal, but rather that it can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal than "vertical," and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0054] In the description of the embodiments of the present invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in the present invention according to the specific circumstances.

[0055] Current methods for measuring the gas holdup of gas-liquid two-phase flow sections within circular pipes have many requirements regarding the pipe material and the flow pattern of the gas-liquid two-phase fluid. Therefore, it is essential to develop an online measurement device and method for the gas holdup of gas-liquid two-phase fluids with arbitrary flow patterns that are not limited by the pipe material. This is a key technology for realizing the measurement of phase holdup of gas-liquid two-phase flow sections within circular pipes in industrial applications.

[0056] The present invention will be further described in detail below with reference to embodiments and accompanying drawings:

[0057] Example 1

[0058] like Figure 1 As shown, a gas content measurement device for a cross-section of a gas-liquid two-phase flow in a circular pipe includes a main pipe 1, a bypass pipe 2, an infrared measuring device 5, a first venting component 6, a second venting component 7, and a data processing unit 18.

[0059] The bypass pipe 2 is connected to the main pipe 1 at both ends. Along the flow direction of the gas-liquid two-phase fluid, the upstream connection is denoted as A, and the downstream connection is denoted as B. If there is a gas-liquid two-phase fluid flowing through the main pipe 1, it can flow into the bypass pipe 2 from point A, and then into the main pipe 1 from point B. A third switch 11 is installed near point A in the bypass pipe 2, and a fourth switch 12 is installed near point B.

[0060] The main pipe 1 is connected at both ends to the cross-section of the tested circular pipe. The main pipe 1 is coaxial with the tested circular pipe. During testing, the gas-liquid two-phase fluid in the tested circular pipe flows into the main pipe 1 from one end, and the flow does not change the cross-sectional phase distribution of the gas-liquid two-phase fluid. A flow pattern adjustment device 3, a first switch 8, and a second switch 9 are installed inside the main pipe 1. The flow pattern adjustment device 3 is located between the upstream end of the main pipe 1 and point A, and is coaxial with the main pipe 1. The flow pattern adjustment device 3 is used to adjust the flow pattern of different gas-liquid two-phase flows. The first switch 8 and the second switch 9 are both located between points A and B. The first switch 8, the second switch 9, the third switch 11, and the fourth switch 12 are used to switch the pipeline.

[0061] The measuring end of the infrared measuring device 5 is positioned between the first switching element 8 and the second switching element 9 of the main pipeline 1. The infrared measuring device 5 can employ an existing measuring device structure and is used to measure the gas-liquid two-phase fluid within the main pipeline 1. Figure 1 In the diagram, X represents the flow direction of the gas-liquid two-phase fluid in the main pipe 1, W represents the flow direction of the gas-liquid two-phase fluid in the bypass pipe, Y represents the direction of the infrared light emitted by the infrared measuring device 5, and Z represents the direction of reflection of the infrared light after passing through the side wall of the main pipe 1.

[0062] The first venting component 6 and the second venting component 7 are both installed on the main pipeline 1, located between the first switch component 8 and the second switch component 9. During measurement, they are used to vent and release the gas-liquid two-phase fluid between the first switch component 8 and the second switch component 9. The first venting component 6 is adjacent to the first switch component 8, and the second venting component is adjacent to the second switch component 9. The first venting component 6 is located directly above the main pipeline 1, on the same side as the infrared measuring device 5. The second venting component 7 is located directly below the main pipeline 1. Here, "above" and "below" refer to... Figure 1 The relative directions in the middle.

[0063] The data processing unit 18 is a data acquisition and calculation unit in the gas content measurement process of the gas content measuring device. It is used to acquire the input voltage and output voltage of the infrared measuring device 5, as well as the volumetric gas content between the first switch 8 and the second switch 9 in the main pipe 1, and to calculate the infrared light intensity attenuation rate, the attenuation coefficient of infrared light in liquid and the attenuation coefficient of infrared light in gas, so as to obtain the gas content of the gas-liquid two-phase flow section in the circular pipe.

[0064] Example 2

[0065] Example 2 is a preferred embodiment of the gas content measurement device for a gas-liquid two-phase flow section in a circular tube according to the present invention, showing the preferred installation structure of the infrared measuring device 5, specifically:

[0066] like Figure 2 As shown, the infrared measuring device 5 is installed on the outer wall of the main pipe 1, downstream of the flow pattern adjustment device 3. An installation hole is formed in the main pipe 1 at the installation location of the infrared measuring device 5. The installation hole is sealed by a transparent window 15, isolating the fluid inside the main pipe 1 from the infrared measuring device 5. As a further preferred embodiment, the transparent window 15 is made of transparent aluminosilicate glass, and its thickness is equal to the wall thickness of the main pipe 1, making the transparent window 15 flush with the wall of the main pipe 1. The infrared measuring device 5 includes an infrared light emitting probe 13 and an infrared light receiving probe 14. The infrared light emitting probe 13 emits infrared light of a fixed wavelength, which enters the main pipe 1 through the transparent window 15. The infrared light receiving probe 14 receives the infrared light reflected from the inner wall of the opposite side of the main pipe 1 and transmitted through the gas-liquid two-phase fluid, and converts the received light intensity signal into a voltage signal.

[0067] The data processing unit 18 supplies power to the infrared measuring device 5 through the power interface 16, receives the input and output voltages of the infrared measuring device 5 through the analog signal interface 17, and obtains and outputs the gas content of the gas-liquid two-phase flow section in the pipe in real time through a series of calculations.

[0068] In addition, the flow pattern adjustment device 3 preferably adopts a vortex starter, which is installed in the main pipe 1 through the fixed bracket 4 and is coaxial with the main pipe 1. The vortex starter has spirally arranged vortex starter blades. After the gas-liquid two-phase flow passes through the vortex starter 3, due to the density difference between the gas and the liquid and the centrifugal force, the liquid will accumulate on the inner wall of the main pipe 1 and the gas will accumulate at the center of the main pipe 1. The vortex starter 3 can transform the flow pattern of the incoming flow without a clear gas-liquid interface into a uniform flow pattern with a stable gas-liquid interface.

[0069] In other embodiments of the present invention, the specific structures of the first switching element 8, the second switching element 9, the third switching element 11 and the fourth switching element 12 can be selected and adjusted according to actual needs. For example, ball valves, electric control valves, etc., or other combined structures can be used, as long as they can control the flow and blockage of liquid at the corresponding positions.

[0070] Similarly, the specific structure of the first venting component 6 and the second venting component 7 can also be adjusted as needed to enable the on / off of venting and drainage between the first switch component 8 and the second switch component 9 in the main pipeline 1.

[0071] In some other embodiments of the present invention, both the main pipe 1 and the bypass pipe 2 can be made of metal pipes with pressure bearing capacity, and both ends of the main pipe 1 can be connected to the tested circular pipe through flanges 10.

[0072] The intensity of infrared light decreases to different degrees in different media. In the same medium, the intensity decreases only with respect to the optical path length in that medium. The change in the intensity of infrared light transmitted through a gas-liquid two-phase flow can reflect the gas content of the gas-liquid two-phase flow cross section.

[0073] The method for measuring the gas content of the gas-liquid two-phase flow section in the above-mentioned circular tube using the aforementioned gas-liquid two-phase flow measuring device is as follows:

[0074] Step 1: In the following two cases respectively:

[0075] Case 1: Turn on the third switch 11 and the fourth switch 12;

[0076] Case 2: Open the fourth switch 12, and at the same time, reduce the opening degree of the third switch 11 compared to Case 1;

[0077] The difference between the input and output voltages of the infrared measuring device 5, the corresponding infrared light intensity attenuation rate, and the volumetric gas content between the first switching element 8 and the second switching element 9 are obtained.

[0078] The first switch 8 and the second switch 9 are turned on, and the first venting device 6 and the second venting device 7 are turned off, so that the gas-liquid two-phase fluid flows into the main pipeline 1 and the bypass pipeline 2. At the same time, the flow pattern adjustment device 3 makes the gas-liquid two-phase fluid form a flow pattern with a stable gas-liquid interface.

[0079] The data processing unit 18 acquires the input voltage of the infrared measuring device 5, as well as the difference between the input voltage and the output voltage, and calculates the infrared light intensity attenuation rate.

[0080] Close the first switch 8 and the second switch 9, open the first venting device 6 and the second venting device 7 to discharge the gas and liquid between the first switch 8 and the second switch 9, obtain the liquid volume, and combine it with the total volume between the first switch 8 and the second switch 9 in the main pipeline 1 to obtain the current gas content in the volume between the first switch 8 and the second switch 9.

[0081] Step 2: Turn on the first switch 8 and the second switch 9, turn off the third switch 11 and the fourth switch 12, and turn off the first venting device 6 and the second venting device 7, so that the gas-liquid two-phase fluid flows into the main pipeline 1. At the same time, the flow pattern adjustment device 3 makes the gas-liquid two-phase fluid form a flow pattern with a gas-liquid interface.

[0082] The data processing unit 18 acquires the input voltage of the infrared measuring device 5, as well as the difference between the input voltage and the output voltage; and calculates the infrared light intensity attenuation rate.

[0083] Step 3: Based on the volumetric gas content between the first switch 8 and the second switch 9 obtained in step S1, and the corresponding infrared light intensity attenuation rate, calculate the attenuation coefficient of infrared light in liquid and the attenuation coefficient of infrared light in gas.

[0084] Step 4: Based on the attenuation coefficient of infrared light in liquid and the attenuation coefficient of infrared light in gas, as well as the infrared light intensity attenuation rate obtained in Step 2, obtain the gas content of the gas-liquid two-phase flow section inside the circular tube.

[0085] In some other embodiments of the present invention, the execution order of steps one and two can be interchanged, as long as the measurements in steps one and two are completed.

[0086] Example 3

[0087] Example 3 is a specific embodiment of a method for measuring the gas content of a cross-section in a circular tube during gas-liquid two-phase flow. The steps are as follows:

[0088] (1) Place the main pipe 1 horizontally and keep the second drain assembly 7 facing downwards (here, "downwards" specifically means...). Figure 1The relative directions shown are intended to ensure that the liquid in the main pipe 1 can flow out smoothly through the vent after the second vent 7 is opened. The first switch 8 and the second switch 9 in the main pipe 1 are both fully open, and the third switch 11 and the fourth switch 12 in the bypass pipe 2 are also fully open. The first vent 6 and the second vent 7 on the main pipe 1 are both closed. The gas-liquid two-phase fluid to be tested is introduced into the main pipe from the end of the main pipe 1 closest to the flow pattern adjustment device 3. The gas-liquid two-phase fluid to be tested forms a uniform flow pattern with a stable gas-liquid interface after passing through the flow pattern adjustment device 3.

[0089] (2) Based on the input voltage U of the infrared measuring device 5 t1 and the output voltage U of the infrared measuring device 5 r1 The difference ΔU1 between the input and output voltages of the infrared measuring device 5 is calculated. Simultaneously, the first switch 8 and the second switch 9 in the main pipeline 1 are closed, and the first venting device 6 and the second venting device 7 are opened to release the gas and liquid between the first switch 8 and the second switch 9 in the main pipeline 1. The volume of the discharged liquid, V, is measured. l1 Based on the total volume V between the first switch element 8 and the second switch element 9 in the main pipeline 1, the gas content β1 of the volume between the first switch element 8 and the second switch element 9 in the main pipeline 1 is calculated.

[0090] The volumetric gas content β can be calculated using the following formula:

[0091]

[0092] Among them, V l V represents the volume of liquid discharged between the first switch element 8 and the second switch element 9, and V represents the total volume between the first switch element 8 and the second switch element 9 in the main pipe 1.

[0093] Specifically:

[0094]

[0095] (3) Close the first venting component 6 and the second venting component 7 on the main pipeline 1, reopen the first switch component 8 and the second switch component 9 on the main pipeline 1, reduce the opening of the third switch component 11 on the bypass pipeline 2, and continue to introduce gas-liquid two-phase fluid.

[0096] (4) The input voltage U through the infrared measuring device 5 t2 and the output voltage U of the infrared measuring device 5 r2 The difference ΔU2 between the input and output voltages of the infrared measuring device 5 is calculated. Simultaneously, the first switch 8 and the second switch 9 on the main pipeline 1 are closed, and the first venting device is opened to release the gas and liquid in the gas-liquid two-phase flow between the first switch 8 and the second switch 9 in the main pipeline 1 through the exhaust device 6 and the second venting device 7. The volume of the discharged liquid, V, is measured.l2 Combining the total volume V between the first switch element 8 and the second switch element 9 within the main pipeline 1, the gas content β2 between the first switch element 8 and the second switch element 9 within the main pipeline 1 is calculated using the same method as in (3):

[0097]

[0098] The total volume V can be calculated using the following formula:

[0099]

[0100] Where D represents the inner diameter of the main pipe 1, and L represents the axial distance between the first switch 8 and the second switch 9 inside the main pipe 1.

[0101] (5) Close the first venting device 6 and the second venting device 7 on the main pipeline 1, reopen the first switch 8 and the second switch 9 on the main pipeline 1, close the third switch 11 and the fourth switch 12 on the bypass pipeline 2, and introduce a gas-liquid two-phase fluid through the main pipeline 1 to obtain the input voltage U of the infrared measuring device 5. t0 And the transient input voltage and output voltage difference ΔU0.

[0102] (6) Establish a model for the relationship between the voltage of infrared measuring device 5 and the infrared light intensity conversion.

[0103] According to the infrared measuring device 5 input voltage U obtained in step (2) t1 The difference between the input voltage and the output voltage ΔU1 is used to calculate the infrared light intensity attenuation rate i1 corresponding to the infrared measuring device 5; based on the input voltage U of the infrared measuring device 5 obtained in step (4), the attenuation rate i1 is calculated. t2 The infrared light intensity attenuation rate i2 corresponding to the infrared measuring device 5 is calculated based on the difference between the input voltage and the output voltage ΔU2; according to the input voltage U of the infrared measuring device 5 obtained in step (5), t0 The infrared light intensity attenuation rate i0 corresponding to the infrared measuring device 5 is calculated by using the difference between the input voltage and the output voltage ΔU0.

[0104] The specific calculation method for the infrared light intensity attenuation rate i1 is as follows:

[0105]

[0106] Where a represents the photoelectric conversion slope coefficient and b represents the photoelectric conversion intercept coefficient.

[0107] The specific calculation method for the infrared light intensity attenuation rate i2 is as follows:

[0108]

[0109] The specific calculation method for the infrared light intensity attenuation rate i0 is as follows:

[0110]

[0111] (7) Based on the gas content β1 between the first switch 8 and the second switch 9 in the main pipe 1 obtained in step (2), the gas content β2 between the first switch 8 and the second switch 9 in the main pipe 1 obtained in step (4), and the infrared light intensity attenuation rate i1 and i2 obtained in step (6), the attenuation coefficient k of infrared light in the liquid is calculated. l and the attenuation coefficient k of infrared light in gas g .

[0112] The specific calculation method is as follows:

[0113]

[0114]

[0115] Where D represents the inner diameter of the main pipe 1.

[0116] (8) Based on the attenuation coefficient k of infrared light in the liquid obtained in step (7) l and the attenuation coefficient k of infrared light in gas g And the infrared light intensity attenuation rate i0 obtained in step (6), the gas content φ of the gas-liquid two-phase flow section inside the circular tube is calculated:

[0117]

[0118] The gas holdup measuring device and method for gas-liquid two-phase flow cross-section in a circular tube according to the present invention can measure the cross-section of the circular tube under test without being limited by the fluid properties of the gas-liquid two-phase flow in the circular tube. It is applicable to gas-liquid inflow conditions in pipes with different flow patterns, and can also meet the requirements for accurate online measurement of the cross-sectional gas holdup of gas-liquid two-phase flow systems in metal pipes with high pressure. There are no restrictions on the placement of the circular tube under test. It can realize the measurement of the cross-sectional gas holdup of gas-liquid two-phase flow in horizontal, vertical or inclined circular tubes. It is simple to operate, easy to implement, and has low measurement cost. It is a key technology for realizing the measurement of phase holdup of gas-liquid two-phase flow in circular tubes in industrial applications and has broad application prospects.

[0119] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A device for measuring the gas content of a cross-section in a circular tube during gas-liquid two-phase flow, characterized in that, include: A bypass pipe (2) is connected to the main pipe (1) at both ends. The connection point located upstream along the flow direction of the gas-liquid two-phase fluid is denoted as A, and the connection point located downstream is denoted as B. A third switch (11) is provided near A in the bypass pipe (2), and a fourth switch (12) is provided near B. The main pipe (1) is connected at both ends to the cross section of the circular pipe to be measured. The main pipe (1) is coaxial with the circular pipe to be measured. The main pipe (1) is equipped with a flow pattern adjustment device (3), a first switch (8) and a second switch (9). The flow pattern adjustment device (3) is located between the upstream end of the main pipe (1) and A, and is coaxial with the main pipe (1). The first switch (8) and the second switch (9) are both located between A and B. The flow pattern adjustment device (3) is a swirl starter. An infrared measuring device (5) is provided, with its measuring end facing the main pipe (1) between the first switch (8) and the second switch (9). The main pipe (1) has a mounting hole on its side wall, and a transparent window (15) is sealed and installed at the mounting hole. The measuring end of the infrared measuring device (5) includes an infrared light emitting probe (13) and an infrared light receiving probe (14). The infrared measuring device (5) is installed on the outer wall of the main pipe (1), and the infrared light emitting probe (13) and the infrared light receiving probe (14) are located within the transparent window (15). The first venting component (6) and the second venting component (7) are both installed on the main pipe (1) and located between the first switch component (8) and the second switch component (9). The first venting component (6) is close to the first switch component (8) and the second venting component (7) is close to the second switch component (9). The data processing unit (18) is used to obtain the input voltage and output voltage of the infrared measuring device (5), as well as the volumetric gas content between the first switch (8) and the second switch (9) in the main pipe (1), and to calculate the infrared light intensity attenuation rate, the attenuation coefficient of infrared light in liquid and the attenuation coefficient of infrared light in gas, so as to obtain the gas content of the gas-liquid two-phase flow section in the circular pipe.

2. The gas content measurement device for a cross-section of a gas-liquid two-phase flow in a circular tube according to claim 1, characterized in that: The transparent window (15) is made of aluminosilicate glass.

3. The gas content measurement device for a cross-section of a gas-liquid two-phase flow in a circular tube according to claim 1 or 2, characterized in that: The first switch (8), the second switch (9), the third switch (11) and the fourth switch (12) are all ball valves.

4. A method for measuring the gas content of a cross-section in a circular pipe during gas-liquid two-phase flow, based on the gas content measuring device for a cross-section in a circular pipe during gas-liquid two-phase flow as described in any one of claims 1 to 3, characterized in that, Includes the following steps: S1, in the following two cases respectively: Case 1: Turn on the third switch (11) and the fourth switch (12); Case 2: Open the fourth switch (12), and at the same time, reduce the opening degree of the third switch (11) compared to Case 1; The difference between the input voltage and output voltage of the infrared measuring device (5), the corresponding infrared light intensity attenuation rate, and the volumetric gas content between the first switch (8) and the second switch (9) are obtained: Turn on the first switch (8) and the second switch (9), and close the first venting device (6) and the second venting device (7) to allow the gas-liquid two-phase fluid to flow into the main pipe (1) and the bypass pipe (2). At the same time, the flow pattern adjustment device (3) makes the gas-liquid two-phase fluid form a flow pattern with a gas-liquid interface. The data processing unit (18) acquires the input voltage of the infrared measuring device (5), as well as the difference between the input voltage and the output voltage, and calculates the infrared light intensity attenuation rate. Close the first switch (8) and the second switch (9), open the first venting device (6) and the second venting device (7), and discharge the gas and liquid between the first switch (8) and the second switch (9) in the main pipeline (1). Obtain the liquid volume, and combine it with the total volume between the first switch (8) and the second switch (9) in the main pipeline (1) to obtain the current gas content between the first switch (8) and the second switch (9). S2, open the first switch (8) and the second switch (9), close the third switch (11) and the fourth switch (12), close the first venting device (6) and the second venting device (7), so that the gas-liquid two-phase fluid flows into the main pipeline (1), and at the same time, the flow pattern adjustment device (3) makes the gas-liquid two-phase fluid form a flow pattern with a gas-liquid interface; The data processing unit (18) obtains the input voltage of the infrared measuring device (5), the difference between the input voltage and the output voltage, and calculates the infrared light intensity attenuation rate. S3. Based on the volumetric gas content between the first switch (8) and the second switch (9) obtained in step S1, and the corresponding infrared light intensity attenuation rate, calculate the attenuation coefficient of infrared light in liquid and the attenuation coefficient of infrared light in gas. S4. Calculate the gas content of the gas-liquid two-phase flow section inside the circular tube based on the attenuation coefficient of infrared light in the liquid and the attenuation coefficient of infrared light in the gas, as well as the infrared light intensity attenuation rate obtained in step S2.

5. The method for measuring the gas content of a cross-section in a circular tube during gas-liquid two-phase flow according to claim 4, characterized in that: The infrared light intensity attenuation rate Calculated using the following formula: in, Indicates the photoelectric conversion slope coefficient. Represents the photoelectric conversion intercept coefficient. This represents the difference between the input voltage and the output voltage of the infrared measuring device (5). This indicates the input voltage of the infrared measuring device (5).

6. The method for measuring the gas content of a cross-section in a circular tube during gas-liquid two-phase flow according to claim 5, characterized in that: Volumetric gas content between the first switch (8) and the second switch (9) Calculated using the following formula: in, This indicates the volume of liquid discharged between the first switch (8) and the second switch (9) via the first drain (6) and the second drain (7). This indicates the total volume between the first switch (8) and the second switch (9) within the main pipe (1).

7. The method for measuring the gas content of a cross-section in a circular tube during gas-liquid two-phase flow according to claim 6, characterized in that: In step S3, the attenuation coefficients of infrared light in liquid and infrared light in gas are calculated using the following formula: in, This represents the attenuation coefficient of infrared light in a liquid. This represents the attenuation coefficient of infrared light in a gas. This indicates the inner diameter of the main pipe (1). This represents the infrared light intensity attenuation rate under condition 1. This represents the infrared light intensity attenuation rate under condition 2. This indicates the volumetric gas content between the first switch (8) and the second switch (9) under condition 1. The volumetric gas content between the first switch (8) and the second switch (9) is indicated under case 2.

8. The method for measuring the gas content of a cross-section in a circular tube during gas-liquid two-phase flow according to claim 7, characterized in that: In step S4, the gas holdup of the gas-liquid two-phase flow section inside the circular pipe is calculated using the following formula: in, This indicates the gas content of the cross section in a circular tube during two-phase gas-liquid flow.

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