Flexible elbow erosion system with adjustable curvature and erosion evaluation method

Abstract

The invention relates to a curvature-adjustable flexible elbow erosion system and an erosion evaluation method, and the system comprises an experiment test loop which is used for carrying out a multi-curvature erosion experiment under the condition that a pipe section is not replaced; the gas phase injection system is connected with the experimental test loop and is used for injecting gas into the experimental test loop; and the liquid-solid phase mixing system is connected with the experimental test loop and is used for injecting a liquid-solid mixture into the experimental test loop. According to the invention, the flexible bent pipe test section with the adjustable curvature radius is adopted, so that the multi-curvature erosion experiment of a single pipe section is realized, and the actual pipeline form is accurately matched; a key erosion area is positioned through CFD simulation, and the position of the sample is dynamically adjusted through the two ends of the flexible bent pipe and in the mode of changing the curvature of the flexible bent pipe; and accurately predicting the actual erosion rate of the seabed flexible bent pipe by comparing an experimental result with a simulation result.

Description

Technical Field

[0001] This invention relates to the field of multiphase flow erosion technology in oil and gas extraction processes, specifically to an adjustable curvature flexible bend erosion system and erosion evaluation method. Background Technology

[0002] During the extraction of oil and gas from subsea oil and gas fields, the produced oil and gas mixtures often carry solid particles. When the mixed fluid flows through flexible subsea pipelines, the continuous impact of these solid particles on the pipe wall triggers an erosion effect, leading to progressive damage to the pipe wall material. Especially in bends where the pipeline flow direction changes abruptly, the frequency and energy of particle impact on the pipe wall increase due to changes in hydrodynamic characteristics, resulting in significantly intensified erosion and wear. This can easily lead to sudden reductions in local wall thickness or even perforation, seriously threatening the structural integrity of the flexible pipeline and the safe operation of the transportation system.

[0003] Flexible bends are one of the commonly used subsea pipelines in offshore oil and gas field development. The core of this system lies in its multi-layered composite structure, specifically the skeleton layer. This skeleton layer is typically composed of multiple layers of thin steel strips arranged in an interlocking geometry. When the pipeline bends, limited relative slippage and slight angular adjustments can occur between adjacent steel strips, but predicting the erosion rate is extremely difficult.

[0004] Existing experimental studies on pipe erosion conventionally use rigid fixed elbows, and there are few studies on the erosion of flexible pipes. Existing erosion studies cannot simulate the change in the radius of curvature of flexible pipes during actual operation. Traditional methods are difficult to accurately locate the maximum erosion area and perform in-situ measurements, resulting in deviations between experimental data and actual operating conditions. Summary of the Invention

[0005] To address the aforementioned problems, the purpose of this invention is to provide an adjustable curvature flexible bend erosion system and erosion evaluation method. This system utilizes a flexible bend test section with an adjustable curvature radius to achieve multi-curvature erosion experiments on a single pipe section, accurately matching the actual pipeline morphology. CFD simulation is used to locate key erosion areas, and the sample position is dynamically adjusted by changing the ends of the flexible bend and altering its curvature. By comparing experimental and simulation results, the actual seabed flexible bend erosion rate can be accurately predicted.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: The adjustable curvature flexible bend erosion system of the present invention comprises: The experimental test loop is used to conduct multi-curvature erosion experiments without replacing the pipe section. A gas injection system, connected to the experimental test loop, is used to inject gas into the experimental test loop; A liquid-solid phase mixing system, connected to the experimental test loop, is used to inject a liquid-solid mixture into the experimental test loop; The experimental test loop includes: a three-phase mixer, a first reducer, a flexible bend test section, a flexible bend sample, a second reducer, and a loop pipe. The gas phase inlet of the three-phase mixer is used to connect to the gas phase injection system, its liquid-solid phase inlet is used to connect to the liquid-solid phase mixing system, its gas-liquid-solid mixed phase outlet is connected to the small diameter end of the first variable diameter pipe, the large diameter end of the first variable diameter pipe is connected to the first end of the flexible bend test section, the second end of the flexible bend test section is connected to the large diameter end of the second variable diameter pipe, the small diameter end of the second variable diameter pipe is connected to the first end of the loop pipe, and the second end of the loop pipe is connected to the inlet of the liquid-solid phase mixing system. The flexible bend test section has a window structure on its pipe wall, and the flexible bend sample is embedded in the window structure.

[0007] The adjustable curvature flexible bend erosion system, preferably, the experimental test loop further includes an adjustment device, and a set of the adjustment devices are respectively provided between the three-phase mixer and the first reducer and between the second reducer and the loop pipe; The regulating device includes a telescopic pipe and an regulating support; The telescopic pipe includes a first fixed section, a second fixed section, and a telescopic section, wherein the telescopic section is disposed between the first fixed section and the second fixed section; The adjusting bracket includes a first transverse slide rail bracket, a second transverse slide rail bracket, a first longitudinal slide rail bracket, a second longitudinal slide rail bracket, and a slider; The first transverse slide rail bracket, the second transverse slide rail bracket, the first longitudinal slide rail bracket, and the second longitudinal slide rail bracket together form a "well" shaped bracket. A slider is set at each of the four corners of the "well" shaped bracket, and each slider can slide horizontally and vertically. The first transverse slide rail bracket passes through the first fixed section, and the second transverse slide rail bracket passes through the second fixed section; When the sliders on both sides of the telescopic pipe are adjusted synchronously in the lateral and longitudinal directions, the radius of curvature of the flexible bend test section is adjusted so as to conduct erosion tests on the flexible bend test sections with different radii of curvature. When the sliders on both sides of the telescopic pipe are adjusted asynchronously in the lateral and longitudinal directions, the angle of the incoming liquid entering the test section of the flexible bend is adjusted so that the current critical erosion area coincides with the opening position.

[0008] The adjustable curvature flexible bend erosion system, preferably, includes a gas phase injection system comprising: a screw compressor, a gas buffer tank, a filter, a vortex flow meter, and a precision regulating valve; The screw compressor, the gas buffer tank, the filter, the vortex flow meter, and the precision regulating valve are connected in series from upstream to downstream through the first pipeline and then connected to the gas phase inlet of the three-phase mixer. The inlet of the screw compressor is in communication with air. The liquid-solid phase mixing system includes: a liquid-solid mixing tank, a liquid-solid phase centrifugal pump, and an electromagnetic flow meter; The outlet of the liquid-solid mixing tank is connected to a liquid-solid phase centrifugal pump via a second pipeline and then splits into two paths. One path is connected to an electromagnetic flow meter via a third pipeline and then connected to the liquid-solid phase inlet of the three-phase mixer to form a liquid-solid injection system. Another route extends into the liquid-solid mixing tank through the fourth pipe via the second inlet, thus forming a self-circulating system for the liquid-solid mixing tank; The first inlet of the liquid-solid mixing tank is used to connect to the loop pipeline; A valve is installed on the second pipeline upstream of the liquid-solid centrifugal pump; Valves are respectively installed on the third pipeline upstream and downstream of the electromagnetic flowmeter; A valve is installed on the fourth pipeline; The outlet of the liquid-solid mixing tank is also connected to a valve via a fifth pipe; The liquid-solid mixing tank includes: a mixing tank body, a shaft, an impeller, a three-phase asynchronous motor, and a frequency converter; The mixing tank body is a container structure with an opening at the top and an outlet at the bottom. The opening at the top of the mixing tank body is covered with a cover plate. The shaft extends into the mixing tank body. Several sets of impellers are movably connected to the shaft. The three-phase asynchronous motor is mounted on the cover plate and connected to the upper end of the shaft. The frequency converter is electrically connected to the three-phase asynchronous motor so that the three-phase asynchronous motor drives the shaft to rotate, thereby driving the impellers to rotate. The impeller is a three-bladed propulsion impeller, with the impeller located in the upper half of the shaft being an upward propulsion type and the impeller located in the lower half of the shaft being a downward propulsion type.

[0009] The adjustable curvature flexible bend erosion system, preferably, the flexible bend sample includes: a sample skeleton structure, a rubber pad and a telescopic steel ring; The sample skeleton structure includes a sample wall and an "S"-shaped interlocking structure. The "S"-shaped interlocking structure is formed by interlocking several "S"-shaped units end to end and connecting them with steel wire. The "S"-shaped interlocking structure is fixedly installed on the inner wall of the sample wall. The sample skeleton structure is fixed to the flexible bending test section by a telescopic steel ring; When the flexible tube sample is embedded in the window structure of the flexible tube test section, there is a wall thickness difference between the flexible tube test section and the sample wall of the sample skeleton structure. The rubber pad is fixedly provided between the sample wall and the flexible tube test section to ensure the continuity of the inner wall surface of the flexible tube test section and the integrity of the flow channel.

[0010] Preferably, in the adjustable curvature flexible bend erosion system, the sample skeleton structure is formed by wire cutting to create a window, so as to ensure the integrity of the sample skeleton structure except for the windowed area.

[0011] This invention also provides a method for evaluating the erosion of a flexible bend erosion system based on adjustable curvature, comprising the following steps: S1. Adjust the radius of curvature of the flexible bend test section to make its structural parameters consistent with the target structural parameters of the actual subsea pipeline. S2: Based on the structural parameters of the flexible bend test section adjusted in step S1 and the actual operating conditions, perform CFD simulation calculation of bend erosion to determine the key erosion area. S3: Open a window on the flexible bend test section at the corresponding position of the critical erosion area described in step S2, process the flexible bend specimen, and maintain the structural integrity of the flexible bend specimen. S4: Install the flexible bend sample processed in step S3 at the window opening to ensure the continuity of the inner wall of the flexible bend test section and the integrity of the flow channel. S5: Conduct erosion test: Start the liquid-solid phase mixing system to ensure that the liquid and solid phases are fully mixed; adjust the gas phase injection system and the liquid-solid phase mixing system so that the experimental conditions, including apparent gas velocity, liquid velocity, sand concentration and sand particle size, are consistent with the actual subsea pipeline operating conditions and the simulated conditions in step S2; run the experimental system to conduct erosion. S6: Process the experimental data, obtain the erosion amount of the flexible bend sample, and calculate the erosion rate; compare and analyze the obtained erosion experimental results with the CFD simulation results of step S2. S7: Remake the sample and repeat steps S4 to S6 multiple times to ensure the reliability of the experimental results; S8: Adjust the radius of curvature of the flexible bend test section according to the actual subsea pipeline, adjust the shape of the flexible bend test section so that the installation position of the flexible bend sample coincides with the high-risk area, repeat steps S5-S7 to conduct experimental tests under different working conditions, in order to predict the erosion rate of the flexible bend test section under different structural parameters.

[0012] The erosion evaluation method, preferably, includes the following steps in step S2: determining the key erosion area, based on the dimensions of the erosion test bend, performing fluid domain modeling and mesh generation, setting the same boundary conditions and particle parameters as the experimental conditions, selecting an appropriate wall rebound coefficient to simulate bend erosion, and determining the location of severe erosion through the erosion cloud map obtained from the simulation calculation.

[0013] The erosion evaluation method, preferably, involves processing a flexible bend sample in step S3, specifically as follows: Wire cutting is used without damaging the surface of the flexible tube sample to ensure the integrity of the sample skeleton structure of the flexible tube “S” type interlocking structure. The sample skeleton structure is fixed by wire threading process to ensure that the sample skeleton structure will not slip and the integrity of the flexible tube sample is maintained. In the erosion evaluation method, preferably, in step S4, the flexible bend sample is installed at the window opening of the flexible bend test section. It is necessary to ensure the integrity of the sample skeleton structure of the remaining flexible bend test sections after the window is opened, and to ensure the consistency between the window size and the flexible bend sample size. The flexible bend sample is embedded in the window position, and a telescopic steel ring and rubber pad are used to fix the flexible bend sample to the window position to ensure the continuity of the inner wall surface of the flexible bend test section and the integrity of the flow channel.

[0014] The erosion evaluation method, preferably, includes the following steps in step S8: adjusting the shape of the flexible bend test section so that the installation position of the flexible bend sample coincides with the high-risk area: The radius of curvature of the flexible bend test section is adjusted by simultaneously adjusting the sliders on both sides of the telescopic pipe in the lateral and longitudinal directions, and by using the changes in their lateral and longitudinal positions. The angle of the incoming liquid entering the test section of the flexible bend is adjusted by asynchronously adjusting the sliders on both sides of the telescopic pipe in the horizontal and vertical directions. By using CFD simulation, a model of pipe erosion under the current curvature radius is established for simulation calculation. By adjusting the inlet angle of the liquid entering the flexible pipe test section, the key erosion area obtained by simulation is made to coincide with the key erosion area under the initial curvature radius condition. This ensures that the inlet angle of the liquid entering the flexible pipe test section in the erosion experiment is consistent with the CFD simulation setting value, so as to achieve the coincidence of the key erosion area and the window position under different curvature radii.

[0015] The present invention has the following advantages due to the adoption of the above technical solutions: (1) A flexible bend test section and variable diameter pipes at both ends are used to match the actual seabed bend conditions. By changing the shape of the test bend, different curvature radii of erosion test conditions are achieved, and the flexible bend erosion test is completed efficiently.

[0016] (2) The flexible bend test section is opened and a replaceable specimen is embedded. The replaceable specimen saves the time of result processing and the cost of replacing the test section.

[0017] (3) The method of combining erosion experiments and numerical simulation can efficiently and quickly determine the key erosion areas, compare and analyze the experimental results and simulation results, and accurately predict the actual erosion rate of the subsea pipeline. The method has simple operation steps and greatly saves research costs. Attached Figure Description

[0018] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Throughout the drawings, the same reference numerals denote the same parts. In the drawings: Figure 1 This is a schematic diagram of the bent pipe erosion test system of the present invention; the adjustment device is not included. Figure 2 This is a schematic diagram of the pipe erosion test system of the present invention, including an adjustment device; Figure 3 This is a schematic diagram of the adjustment device in this invention; Figure 4 This is a schematic diagram of the liquid-solid mixing tank in this invention; Figure 5 This is a schematic diagram of the flexible bend test section opening and the flexible bend sample in this invention. Figure 6 This is a schematic diagram of the specific installation of the flexible bend tube sample in this invention; Figure 7 This is a schematic diagram of adjusting the radius of curvature of the flexible bend test section in this invention.

[0019] The labels for the attached figures are as follows: 1-Screw compressor; 2-Gas buffer tank; 3-Filter; 4-Vortex flow meter; 5-Precision regulating valve; 6-Liquid-solid mixing tank; 601-Mixing tank body; 602-Shaft; 603-Impeller; 604-Three-phase asynchronous motor; 605-Frequency converter; 7-Liquid-solid phase centrifugal pump; 8-Electromagnetic flow meter; 9-Three-phase mixer; 10-Flexible bend test section; 11-First reducing pipe; 12-Loop pipeline; 13-Flexible bend sample; 1301-Sample wall; 1302-“S”-shaped interlocking structure; 1303-Rubber pad; 1304-Extension 14-Second reducing pipe; 15-First pipe; 16-Second pipe; 17-Third pipe; 18-Fourth pipe; 19-Fifth pipe; 20-Adjusting device; 20-1-Telescopic pipe; 20-101-First fixed section; 20-102-Second fixed section; 20-103-Telescopic section; 20-2-Adjusting bracket; 20-201-First transverse slide rail bracket; 20-202-Second transverse slide rail bracket; 20-203-First longitudinal slide rail bracket; 20-204-Second longitudinal slide rail bracket; 20-205-Slider. Detailed Implementation

[0020] Exemplary embodiments of the invention will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the invention are shown in the drawings, it should be understood that the invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of the invention and to fully convey the scope of the invention to those skilled in the art.

[0021] This invention provides an adjustable curvature flexible bend erosion system and erosion evaluation method. It uses a flexible bend test section with an adjustable curvature radius to realize multi-curvature erosion experiments on a single pipe section, accurately matching the actual pipeline morphology. It combines CFD simulation to locate key erosion areas and dynamically adjusts the sample position by changing the ends of the flexible bend and the curvature of the flexible bend. By comparing the experimental results with the simulation results, it accurately predicts the actual seabed flexible bend erosion rate.

[0022] like Figure 1 As shown, the adjustable curvature flexible bend erosion system provided by the present invention includes: The experimental test loop is used to conduct multi-curvature erosion experiments without replacing the pipe section. A gas injection system, connected to the experimental test loop, is used to inject gas into the experimental test loop; A liquid-solid phase mixing system, connected to the experimental test loop, is used to inject a liquid-solid mixture into the experimental test loop; The experimental test loop includes: a three-phase mixer 9, a first reducer 11, a flexible bend test section 10, a flexible bend sample 13, a second reducer 14, and a loop pipe 12. The gas phase inlet of the three-phase mixer 9 is used to connect to the gas phase injection system, and its liquid-solid phase inlet is used to connect to the liquid-solid phase mixing system. Its gas-liquid-solid mixed phase outlet is connected to the small diameter end of the first reducer 11. The large diameter end of the first reducer 11 is connected to the first end of the flexible bend test section 10. The second end of the flexible bend test section 10 is connected to the large diameter end of the second reducer 14. The small diameter end of the second reducer 14 is connected to the first end of the loop pipe 12. The second end of the loop pipe 12 is connected to the inlet of the liquid-solid phase mixing system. A window structure is provided on the pipe wall of the flexible bend test section 10, and the flexible bend sample 13 is embedded in the window structure.

[0023] In the above embodiments, preferably, as follows: Figure 2 and Figure 3 As shown, the experimental test loop also includes an adjustment device 20. A set of the adjustment devices 20 are respectively installed between the three-phase mixer and the first variable diameter pipe and between the second variable diameter pipe and the loop pipeline; of course, the first variable diameter pipe and the second variable diameter pipe can also be replaced by the adjustment device 20.

[0024] The adjusting device 20 includes a telescopic pipe 20-1 and an adjusting bracket 20-2; the telescopic pipe 20-1 includes a first fixed section 20-101, a second fixed section 20-102, and a telescopic section 20-103, the telescopic section 20-103 being disposed between the first fixed section 20-101 and the second fixed section 20-102; the adjusting bracket 20-2 includes a first transverse slide rail bracket 20-201, a second transverse slide rail bracket 20-202, a first longitudinal slide rail bracket 20-203, a second longitudinal slide rail bracket 20-204, and a slider 20-205; the first transverse slide rail bracket 20-201, the second transverse slide rail bracket 20-202, the first longitudinal slide rail bracket 20-203, and the second longitudinal slide rail bracket 20-204 together form a "well". The "well" shaped support has a slider 20-205 at each of its four corners, and each slider 20-205 can slide laterally and longitudinally. The first transverse slide rail support 20-201 passes through the first fixed section 20-101, and the second transverse slide rail support 20-202 passes through the second fixed section 20-102. When the sliders 20-205 on both sides of the telescopic pipe 20-1 are adjusted synchronously in both lateral and longitudinal directions, the radius of curvature of the flexible bend test section is adjusted to conduct erosion tests on the flexible bend test sections with different radii of curvature. When the sliders 20-205 on both sides of the telescopic pipe 20-1 are adjusted asynchronously in both lateral and longitudinal directions, the angle of the incoming liquid entering the flexible bend test section 10 is adjusted so that the current critical erosion area coincides with the opening position.

[0025] It should be noted that when the slider moves to the set position, positioning is achieved by a screw passing through the hole on the slider and the hole on the "well"-shaped bracket. When the sliders 20-205 on both sides of the telescopic pipe 20-1 are adjusted synchronously in both the lateral and longitudinal directions, the sliders on both sides adjust the same distance laterally and longitudinally. When the sliders 20-205 on both sides of the telescopic pipe 20-1 are adjusted asynchronously in both the lateral and longitudinal directions, the sliders on both sides adjust the different distances laterally and longitudinally, so that the telescopic pipe can be deflected.

[0026] In the above embodiments, preferably, the gas phase injection system includes: a screw compressor 1, a gas buffer tank 2, a filter 3, a vortex flow meter 4, and a precision regulating valve 5; the screw compressor 1, the gas buffer tank 2, the filter 3, the vortex flow meter 4, and the precision regulating valve 5 are connected in series from upstream to downstream through the first pipeline 15 and then connected to the gas phase inlet of the three-phase mixer 9, and the inlet of the screw compressor 1 is in communication with air.

[0027] In the above embodiments, preferably, a pressure gauge is provided on the first pipeline 15 between the filter 3 and the vortex flow meter 4; valves are provided upstream and downstream of the pressure gauge respectively; and a valve is provided on the first pipeline 15 between the screw compressor 1 and the gas buffer tank 2.

[0028] In the above embodiments, preferably, the liquid-solid phase mixing system includes: a liquid-solid mixing tank 6, a liquid-solid phase centrifugal pump 7, and an electromagnetic flowmeter 8; the liquid-solid phase mixing system can realize two processes, namely a liquid-solid mixing tank self-circulation system and a liquid-solid injection system. The liquid-solid mixing tank self-circulation system ensures that the liquid and solid phases are fully mixed, which conforms to the actual liquid-solid mixing situation of the subsea pipeline; the liquid-solid injection system is connected to the flexible bend test section via a three-phase mixer.

[0029] The outlet of the liquid-solid mixing tank 6 is connected to the liquid-solid phase centrifugal pump 7 via the second pipeline 16 and then splits into two paths. One path is connected to the electromagnetic flowmeter 8 via the third pipeline 17 and then connected to the liquid-solid phase inlet of the three-phase mixer 9 to form a liquid-solid injection system. The other path extends into the liquid-solid mixing tank 6 from the second inlet via the fourth pipeline 18 to form a liquid-solid mixing tank self-circulation system. In the liquid-solid mixing tank self-circulation system, the liquid-solid phase mixed fluid is pumped from the liquid-solid mixing tank 6 to the liquid-solid phase centrifugal pump 7 and then sent to the liquid-solid mixing tank 6 via the fourth pipeline 18. The entire liquid-solid mixing system ensures that the liquid and solid phases are fully mixed, which is consistent with the actual liquid-solid phase mixing degree of the subsea pipeline.

[0030] The first inlet of the liquid-solid mixing tank 6 is used to connect to the loop pipe 12; A valve is installed on the second pipeline 16 upstream of the liquid-solid centrifugal pump 7; Valves are installed on the third pipeline 17 upstream and downstream of the electromagnetic flowmeter 8; A valve is installed on the fourth pipeline 18; The outlet of the liquid-solid mixing tank 6 is also connected to a valve via the fifth pipe 19.

[0031] In the above embodiments, preferably, as follows: Figure 4 As shown, the liquid-solid mixing tank 6 includes: a mixing tank body 601, a shaft 602, an impeller 603, a three-phase asynchronous motor 604, and a frequency converter 605; the mixing tank body 601 is a container structure with an opening at the top and an outlet at the bottom. The opening at the top of the mixing tank body 601 is covered with a cover plate. The shaft 602 extends into the mixing tank body 601. Several sets of impellers 603 are movably connected to the shaft 602. The three-phase asynchronous motor 604 is mounted on the cover plate and connected to the upper end of the shaft 602. The frequency converter 605 is electrically connected to the three-phase asynchronous motor 604 so that the three-phase asynchronous motor 604 drives the shaft 602 to rotate, thereby driving the impellers 603 to rotate. Among them, impeller 603 is a three-bladed propulsion impeller, the impeller 603 located in the upper half of shaft 602 is an upward propulsion type, and the impeller 603 located in the lower half of shaft 602 is a downward propulsion type.

[0032] In the above embodiments, preferably, as follows: Figure 5 and Figure 6 As shown, the flexible bending tube specimen 13 includes: a specimen skeleton structure, a rubber pad 1303, and a telescopic steel ring 1304. The specimen skeleton structure includes a specimen wall 1301 and an "S"-shaped interlocking structure 1302. The "S"-shaped interlocking structure 1302 is formed by interlocking several "S"-shaped units end to end and connecting them with steel wire. The "S"-shaped interlocking structure is fixedly installed on the inner wall of the specimen wall 1301. Of course, it can also be integrated into one piece. The specimen skeleton structure is fixed to the flexible bending test section 10 by the telescopic steel ring 1304 (see...). Figure 5 ); When the flexible tube sample 13 is embedded into the window structure of the flexible tube test section 10, since there is a difference in wall thickness between the flexible tube test section 10 and the sample wall 1301 of the sample skeleton structure, a rubber pad 1303 is fixedly provided between the sample wall 1301 and the flexible tube test section 10 to ensure the continuity of the inner wall surface of the flexible tube test section 10 and the integrity of the flow channel.

[0033] In the above embodiments, preferably, the sample skeleton structure is formed by wire cutting to open a window, so as to ensure the integrity of the sample skeleton structure except for the windowed area.

[0034] This invention also provides a method for evaluating the erosion of a flexible bend erosion system with adjustable curvature, characterized by comprising the following steps: S1, such as Figure 7 As shown, the radius of curvature of the flexible bend test section 10 is adjusted so that its structural parameters are consistent with the target structural parameters of the actual subsea pipeline. S2: Based on the structural parameters of the flexible bend test section 10 adjusted in step S1 and the actual operating conditions, perform CFD simulation calculation of bend erosion to determine the key erosion area. S3: Open a window on the flexible bend test section 10 at the corresponding position of the critical erosion area described in step S2, process the flexible bend specimen 13, and maintain the structural integrity of the flexible bend specimen 13. S4: Install the flexible bend sample 13 processed in step S3 at the opening to ensure the continuity of the inner wall of the flexible bend test section 10 and the integrity of the flow channel. S5: Conduct erosion test: Start the liquid-solid phase mixing system to ensure that the liquid and solid phases are fully mixed; adjust the gas phase injection system and the liquid-solid phase mixing system so that the experimental conditions, including apparent gas velocity, liquid velocity, sand concentration and sand particle size, are consistent with the actual subsea pipeline operating conditions and the simulated conditions in step S2; run the experimental system to conduct erosion. It should be noted that the specific operation of the erosion experiment is as follows: Deionized water is injected into the mixing tank, and the impeller-equipped shaft is started for stirring. The bypass pipeline is opened, and the liquid-solid phase centrifugal pump 7 is started to form a circulation loop. According to the required particle volume concentration and sand particle size, the required sand particles are screened using a standard sieve and a laser particle size analyzer, and the particles are calculated and weighed. The sand particles are then slowly and evenly added into the mixing tank. The screw compressor 1 is turned on to pressurize the gas phase and then enter the gas buffer tank 2 to achieve pressure buffering and stabilization. Then, pump filling and pump start-up operations are performed. The speed of the liquid-solid phase centrifugal pump 7 is adjusted using the frequency converter 605 to control the liquid phase flow rate. The gas phase flow rate is adjusted using the precision regulating valve 5 to ensure that the experimental conditions are consistent with the simulated conditions. After the flow stabilizes, the data acquisition system is turned on to start collecting data such as flow rate and pressure to conduct the erosion experiment. At the end of the experiment, the gas phase and liquid-solid phase valves are closed simultaneously.

[0035] S6: Process the experimental data, obtain the erosion amount of the flexible bend sample 13, and calculate the erosion rate; compare and analyze the obtained erosion experimental results with the CFD simulation results of step S2. S7: Re-make the sample, install it, and repeat steps S4~S6 multiple times to ensure the reliability of the experimental results; S8: Adjust the radius of curvature of the flexible bend test section 10 according to the actual subsea pipeline, adjust the shape of the flexible bend test section 10 so that the installation position of the flexible bend sample 13 coincides with the high-risk area, repeat steps S5-S7 to conduct experimental tests under different working conditions, in order to predict the erosion rate of the flexible bend test section under different structural parameters.

[0036] In the above embodiment, preferably, the calculation formula for the CFD simulation of pipe erosion in step S2 is as follows:

[0037] In the formula: E L The erosion rate of the bend; m p This refers to the particle mass flow rate; K These are material constants; F ( α () represents the particle impact angle function; U p The particle impact velocity; n The speed index; ρ t This refers to the density of the pipe material. A pipe The erosion area; G This is the particle size correction factor; C geometric factor ( C =2.5); C unit For unit conversion factors, C unit =3.15×10 10 .

[0038] In the above embodiments, preferably, the determination of the key erosion area in step S2 includes the following steps: based on the size of the bend tested in the erosion experiment, perform fluid domain modeling and mesh generation, set the same boundary conditions and particle parameters as the experimental conditions, select an appropriate wall rebound coefficient to simulate the erosion of the bend, and determine the location of severe erosion through the erosion cloud map obtained from the simulation calculation.

[0039] In the above embodiments, preferably, the flexible bend sample is processed in step S3, and the specific steps are as follows: Wire cutting is used without damaging the surface of the flexible tube sample to ensure the integrity of the sample skeleton structure of the flexible tube “S” type interlocking structure. The sample skeleton structure is fixed by wire threading process to ensure that the flexible tube sample skeleton structure will not slip and the integrity of the sample is maintained. In step S4, the flexible tube sample is installed at the window opening of the flexible tube test section. It is necessary to ensure the integrity of the sample skeleton structure of the remaining flexible tube test sections after the window is opened, and to ensure the consistency between the window size and the flexible tube sample size. The flexible tube sample is embedded in the window position, and a telescopic steel ring and rubber pads are used to fix the flexible tube sample to the window position to ensure the continuity of the inner wall surface of the flexible tube test section and the integrity of the flow channel.

[0040] When installing the flexible tube sample into the windowed structure of the flexible tube test section, first measure and obtain the difference in wall thickness between the sample wall and the flexible tube test section at the windowed position. Then, based on this difference in wall thickness, select a rubber pad of appropriate thickness as a compensation pad and place it between the sample wall and the flexible tube test section. The telescopic steel ring is used to apply uniform radial pressure from behind the sample to press and fix the sample skeleton structure and the rubber pad, so that the inner surface of the sample wall is flush with the inner wall of the flexible tube test section, thus ensuring the continuity of the inner wall surface of the test section and the integrity of the flow channel.

[0041] It should be noted that the telescopic steel ring is a ring-shaped tight-fitting steel ring, which can be contracted by bolts. The telescopic steel ring is fitted over the flexible bending test section and the flexible bending sample to form a whole, so as to fix the two together. Since this telescopic steel ring is a mature component that can be purchased directly on the market, its specific structure will not be described in detail here.

[0042] In the above embodiments, preferably, step S6, which processes experimental data to obtain the erosion amount of the flexible bend sample and calculates the erosion rate, includes the following steps: The erosion test results of the flexible bend sample were processed by combining three methods: weight loss method, thickness reduction method, and surface microscopic observation. The method was as follows: the erosion rate of the bend sample was obtained by combining the three methods: mass measurement before and after erosion by balance, thickness change before and after erosion by microscopic measurement, and surface morphology of the flexible bend sample before and after erosion by microscopic observation. The erosion mechanism of sand particles was analyzed by the changes in the erosion appearance before and after erosion.

[0043] In the above embodiments, preferably, step S8, adjusting the shape of the flexible bend test section so that the installation position of the flexible bend sample coincides with the high-risk area, specifically includes the following steps: The radius of curvature of the flexible bend test section is adjusted by simultaneously adjusting the sliders on both sides of the telescopic pipe in the lateral and longitudinal directions, and by using the changes in their lateral and longitudinal positions. The angle of the incoming liquid entering the test section of the flexible bend is adjusted by asynchronously adjusting the sliders on both sides of the telescopic pipe in the horizontal and vertical directions. By using CFD simulation, a model of pipe erosion under the current curvature radius is established for simulation calculation. By adjusting the inlet angle of the liquid entering the flexible pipe test section, the key erosion area obtained by simulation is made to coincide with the key erosion area under the initial curvature radius condition. This ensures that the inlet angle of the liquid entering the flexible pipe test section in the erosion experiment is consistent with the CFD simulation setting value, so as to achieve the coincidence of the key erosion area and the window position under different curvature radii.

[0044] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. An adjustable curvature flexible bend erosion system, characterized in that, include: The experimental test loop is used to conduct multi-curvature erosion experiments without replacing the pipe section. A gas injection system, connected to the experimental test loop, is used to inject gas into the experimental test loop; A liquid-solid phase mixing system, connected to the experimental test loop, is used to inject a liquid-solid mixture into the experimental test loop; The experimental test loop includes: a three-phase mixer, a first reducer, a flexible bend test section, a flexible bend sample, a second reducer, and a loop pipe. The gas phase inlet of the three-phase mixer is used to connect to the gas phase injection system, its liquid-solid phase inlet is used to connect to the liquid-solid phase mixing system, its gas-liquid-solid mixed phase outlet is connected to the small diameter end of the first variable diameter pipe, the large diameter end of the first variable diameter pipe is connected to the first end of the flexible bend test section, the second end of the flexible bend test section is connected to the large diameter end of the second variable diameter pipe, the small diameter end of the second variable diameter pipe is connected to the first end of the loop pipe, and the second end of the loop pipe is connected to the inlet of the liquid-solid phase mixing system. The flexible bend test section has a window structure on its pipe wall, and the flexible bend sample is embedded in the window structure.

2. The adjustable curvature flexible bend erosion system according to claim 1, characterized in that, The experimental test loop also includes adjustment devices, and a set of the adjustment devices is respectively installed between the three-phase mixer and the first variable diameter pipe and between the second variable diameter pipe and the loop pipeline; The regulating device includes a telescopic pipe and an regulating support; The telescopic pipe includes a first fixed section, a second fixed section, and a telescopic section, wherein the telescopic section is disposed between the first fixed section and the second fixed section; The adjusting bracket includes a first transverse slide rail bracket, a second transverse slide rail bracket, a first longitudinal slide rail bracket, a second longitudinal slide rail bracket, and a slider; The first transverse slide rail bracket, the second transverse slide rail bracket, the first longitudinal slide rail bracket, and the second longitudinal slide rail bracket together form a "well" shaped bracket. A slider is set at each of the four corners of the "well" shaped bracket, and each slider can slide horizontally and vertically. The first transverse slide rail bracket passes through the first fixed section, and the second transverse slide rail bracket passes through the second fixed section; When the sliders on both sides of the telescopic pipe are adjusted synchronously in the lateral and longitudinal directions, the radius of curvature of the flexible bend test section is adjusted so as to conduct erosion tests on the flexible bend test sections with different radii of curvature. When the sliders on both sides of the telescopic pipe are adjusted asynchronously in the lateral and longitudinal directions, the angle of the incoming liquid entering the test section of the flexible bend is adjusted so that the current critical erosion area coincides with the opening position.

3. The adjustable curvature flexible bend erosion system according to claim 1, characterized in that, The gas injection system includes: a screw compressor, a gas buffer tank, a filter, a vortex flow meter, and a precision regulating valve; The screw compressor, the gas buffer tank, the filter, the vortex flow meter, and the precision regulating valve are connected in series from upstream to downstream through the first pipeline and then connected to the gas phase inlet of the three-phase mixer. The inlet of the screw compressor is in communication with air. The liquid-solid phase mixing system includes: a liquid-solid mixing tank, a liquid-solid phase centrifugal pump, and an electromagnetic flow meter; The outlet of the liquid-solid mixing tank is connected to a liquid-solid phase centrifugal pump via a second pipeline and then splits into two paths. One path is connected to an electromagnetic flow meter via a third pipeline and then connected to the liquid-solid phase inlet of the three-phase mixer to form a liquid-solid injection system. Another route extends into the liquid-solid mixing tank through the fourth pipe via the second inlet, thus forming a self-circulating system for the liquid-solid mixing tank; The first inlet of the liquid-solid mixing tank is used to connect to the loop pipeline; A valve is installed on the second pipeline upstream of the liquid-solid centrifugal pump; Valves are respectively installed on the third pipeline upstream and downstream of the electromagnetic flowmeter; A valve is installed on the fourth pipeline; The outlet of the liquid-solid mixing tank is also connected to a valve via a fifth pipe; The liquid-solid mixing tank includes: a mixing tank body, a shaft, an impeller, a three-phase asynchronous motor, and a frequency converter; The mixing tank body is a container structure with an opening at the top and an outlet at the bottom. The opening at the top of the mixing tank body is covered with a cover plate. The shaft extends into the mixing tank body. Several sets of impellers are movably connected to the shaft. The three-phase asynchronous motor is mounted on the cover plate and connected to the upper end of the shaft. The frequency converter is electrically connected to the three-phase asynchronous motor so that the three-phase asynchronous motor drives the shaft to rotate, thereby driving the impellers to rotate. The impeller is a three-bladed propulsion impeller, with the impeller located in the upper half of the shaft being an upward propulsion type and the impeller located in the lower half of the shaft being a downward propulsion type.

4. The adjustable curvature flexible bend erosion system according to claim 1, characterized in that, The flexible tube sample includes: a sample skeleton structure, a rubber pad, and a telescopic steel ring; The sample skeleton structure includes a sample wall and an "S"-shaped interlocking structure. The "S"-shaped interlocking structure is formed by interlocking several "S"-shaped units end to end and connecting them with steel wire. The "S"-shaped interlocking structure is fixedly installed on the inner wall of the sample wall. The sample skeleton structure is fixed to the flexible bending test section by a telescopic steel ring; When the flexible tube sample is embedded in the window structure of the flexible tube test section, there is a wall thickness difference between the flexible tube test section and the sample wall of the sample skeleton structure. The rubber pad is fixedly provided between the sample wall and the flexible tube test section to ensure the continuity of the inner wall surface of the flexible tube test section and the integrity of the flow channel.

5. The adjustable curvature flexible bend erosion system according to claim 4, characterized in that, The sample skeleton structure is formed by wire cutting to create a window, in order to ensure the integrity of the sample skeleton structure except for the windowed area.

6. A method for evaluating the erosion of a flexible bend erosion system with adjustable curvature based on any one of claims 1 to 5, characterized in that, Includes the following steps: S1. Adjust the radius of curvature of the flexible bend test section to make its structural parameters consistent with the target structural parameters of the actual subsea pipeline. S2: Based on the structural parameters of the flexible bend test section adjusted in step S1 and the actual operating conditions, perform CFD simulation calculation of bend erosion to determine the key erosion area. S3: Open a window on the flexible bend test section at the corresponding position of the critical erosion area described in step S2, process the flexible bend specimen, and maintain the structural integrity of the flexible bend specimen. S4: Install the flexible bend sample processed in step S3 at the window opening to ensure the continuity of the inner wall of the flexible bend test section and the integrity of the flow channel. S5: Conduct erosion test: Start the liquid-solid phase mixing system to ensure that the liquid and solid phases are fully mixed; adjust the gas phase injection system and the liquid-solid phase mixing system so that the experimental conditions, including apparent gas velocity, liquid velocity, sand concentration and sand particle size, are consistent with the actual subsea pipeline operating conditions and the simulated conditions in step S2; run the experimental system to conduct erosion. S6: Process the experimental data, obtain the erosion amount of the flexible bend sample, and calculate the erosion rate; compare and analyze the obtained erosion experimental results with the CFD simulation results of step S2. S7: Remake the sample and repeat steps S4 to S6 multiple times to ensure the reliability of the experimental results; S8: Adjust the radius of curvature of the flexible bend test section according to the actual subsea pipeline, adjust the shape of the flexible bend test section so that the installation position of the flexible bend sample coincides with the high-risk area, repeat steps S5-S7 to conduct experimental tests under different working conditions, in order to predict the erosion rate of the flexible bend test section under different structural parameters.

7. The erosion evaluation method according to claim 6, characterized in that, The determination of the key erosion area in step S2 includes the following steps: based on the dimensions of the erosion test bend, perform fluid domain modeling and mesh generation, set the same boundary conditions and particle parameters as the experimental conditions, select an appropriate wall rebound coefficient to simulate the erosion of the bend, and determine the location of severe erosion through the erosion cloud map obtained from the simulation calculation.

8. The erosion evaluation method according to claim 6, characterized in that, The specific steps for processing the flexible bend sample in step S3 are as follows: Wire cutting is used without damaging the surface of the flexible tube sample to ensure the integrity of the sample skeleton structure of the flexible tube "S" type interlocking structure. The sample skeleton structure is then fixed using a wire threading process to ensure that the sample skeleton structure will not slip and to maintain the integrity of the flexible tube sample.

9. The erosion evaluation method according to claim 6, characterized in that, In step S4, the flexible tube sample is installed at the window opening of the flexible tube test section. It is necessary to ensure the integrity of the sample skeleton structure of the remaining flexible tube test sections after the window is opened, and to ensure the consistency between the window size and the flexible tube sample size. The flexible tube sample is embedded in the window position, and a telescopic steel ring and rubber pad are used to fix the flexible tube sample to the window position to ensure the continuity of the inner wall surface of the flexible tube test section and the integrity of the flow channel.

10. The erosion evaluation method according to claim 6, characterized in that, In step S8, adjusting the shape of the flexible bend test section to align the installation position of the flexible bend sample with the high-risk area specifically includes the following steps: The radius of curvature of the flexible bend test section is adjusted by simultaneously adjusting the sliders on both sides of the telescopic pipe in the lateral and longitudinal directions, and by using the changes in their lateral and longitudinal positions. The angle of the incoming liquid entering the test section of the flexible bend is adjusted by asynchronously adjusting the sliders on both sides of the telescopic pipe in the horizontal and vertical directions. By using CFD simulation, a model of pipe erosion under the current curvature radius is established for simulation calculation. By adjusting the inlet angle of the liquid entering the flexible pipe test section, the key erosion area obtained by simulation is made to coincide with the key erosion area under the initial curvature radius condition. This ensures that the inlet angle of the liquid entering the flexible pipe test section in the erosion experiment is consistent with the CFD simulation setting value, so as to achieve the coincidence of the key erosion area and the window position under different curvature radii.

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