An experimental pipeline for wall erosion of an inner tube, an experimental system and an experimental method

Abstract

This invention discloses an experimental pipeline, system, and method for erosion corrosion testing of the outer wall of an inner tube. The experimental pipeline includes an experimental pipe and a sample fixing assembly. The sample fixing assembly is used to fix the sample in the inner cavity of the experimental pipe. After the sample is fixed, an annular gap is formed between the outer wall of the sample and the inner wall of the experimental pipe, and the annular gap is used for the flow of fluid medium. The experimental system for erosion corrosion testing of the outer wall of an inner tube includes the above-mentioned experimental pipeline, a power circulation device, and a signal processing device. The power circulation device is used to drive the fluid medium to flow in the experimental pipe, and the signal processing device is used to analyze the state parameters of the fluid medium and / or the corrosion state parameters of the sample. By setting up the sample fixing device to fix the sample in the inner cavity of the experimental pipe and forming an annular gap between the outer wall of the sample and the inner wall of the experimental pipe, an annular flow channel consistent with the geometric characteristics of the casing structure is directly constructed, providing an experimental environment consistent with actual working conditions for erosion corrosion testing of the outer wall of the inner tube.

Description

Technical Field

[0001] This invention relates to the field of erosion corrosion testing technology, and in particular to an experimental pipeline, experimental system and experimental method for erosion corrosion testing of the outer wall of an inner pipe. Background Technology

[0002] Erosion corrosion is one of the main failure modes of materials in fluid machinery, oil and gas transportation, marine engineering, chemical equipment, power plant thermal systems, and nuclear industry equipment. Essentially, it is the result of the synergistic coupling effect of fluid mechanical forces and electrochemical corrosion. Under the influence of media containing solid particles, gas-liquid two-phase, liquid-liquid two-phase, or multiphase mixtures, the material surface is simultaneously subjected to the combined effects of shear stress, localized turbulent impact, particle impaction, and corrosive media erosion. This leads to wall thinning, pitting corrosion, groove wear, and even perforation failure, seriously threatening the safe operation of equipment.

[0003] In practical engineering, shell-and-tube or double-walled tube structures are widely used in heat exchangers, condensers, reactors, oil and gas pipelines, marine risers, pump and valve systems, and thermal management devices. Existing research and testing equipment for erosion corrosion mostly focuses on single-tube structures with exposed inner and outer walls or simple flat plate samples, primarily used to study the erosion wear and electrochemical corrosion behavior of the outer wall or open surfaces. Unlike traditional single-tube structures, the outer wall of the inner tube in a shell-and-tube structure is simultaneously affected by fluid erosion, the constraint and disturbance of the outer tube, and local flow field reconstruction. The outer wall of the inner tube is subjected to both direct erosion by the multiphase fluid within the annular channel and constraint and disturbance of the flow field by the outer tube wall. Its flow boundary layer characteristics, particle / bubble distribution, and wall shear force distribution differ fundamentally from those of single-tube flow or conventional container walls. This complex flow field distribution directly determines the non-uniformity of the erosion corrosion morphology of the outer wall of the inner tube and the characteristics of locally accelerated damage. However, due to limitations such as narrow structural space, difficulty in constructing flow fields, challenges in visualization observation, and inconvenience in setting up online electrochemical tests, existing single-tube or reactor-type experimental devices cannot construct a real annular flow field in the sleeve, and it is even more difficult to conduct in-situ, online electrochemical monitoring and damage morphology visualization observation of the outer wall of the inner tube within this confined space. Summary of the Invention

[0004] This invention provides an experimental pipeline, system, and method for scouring corrosion of the outer wall of an inner tube, aiming to solve the technical problem that existing scouring corrosion experimental devices and methods cannot construct a real annular channel flow field in a casing.

[0005] To achieve the above objectives, the first aspect of the present invention provides an experimental pipeline for erosion corrosion of the inner wall of a tube, comprising an experimental pipeline and a sample fixing assembly;

[0006] The sample fixing assembly is used to fix the sample in the inner cavity of the experimental pipe. After the sample is fixed, an annular gap is formed between the outer wall of the sample and the inner wall of the experimental pipe. The annular gap is used to allow the flow of fluid medium.

[0007] This invention fixes the sample to the inner cavity of the experimental pipe by setting a sample fixing device and forming an annular gap between the outer wall of the sample and the inner wall of the experimental pipe, thereby directly constructing an annular flow channel consistent with the geometric features of the sleeve structure, providing an experimental environment that matches the actual working conditions for the erosion corrosion of the outer wall of the inner pipe.

[0008] Preferably, the sample fixing assembly includes two fixing rings, which are spaced apart along the axial direction of the experimental pipe;

[0009] The fixing ring includes an outer ring and an inner ring. The outer ring and the inner ring are fixedly connected by several connecting posts. The outer ring is fixedly connected to the experimental pipe. The inner ring is located in the inner cavity of the experimental pipe. The two ends of the sample are respectively fixedly connected to the inner rings of the two fixing rings.

[0010] The sample is secured by two fixing rings, ensuring its stability in the central axis position within the experimental pipe cavity. The hollowed-out connecting column structure minimizes the disturbance of the fixing rings to the flow field within the annular gap, thus more realistically simulating the annular flow channel.

[0011] Preferably, the sample fixing assembly further includes a first connecting rod and a second connecting rod, wherein the first end of the first connecting rod and the first end of the second connecting rod are respectively fixedly connected to the inner rings of the two fixing rings, and the second end of the first connecting rod and the second end of the second connecting rod are respectively fixedly connected to both ends of the sample.

[0012] The first and second connecting rods increase the distance between the sample and the fixing ring, further avoiding interference from the fixing ring to the flow field near the sample. At the same time, by replacing the connecting rods of different lengths, the axial position of the sample can be adjusted to test the corrosion at different locations.

[0013] Preferably, it further includes a first detection component, which includes a reference electrode, an auxiliary electrode, a conductor, and an electrochemical workstation. The reference electrode and the auxiliary electrode are both connected to the inner cavity of the experimental pipe, and the conductor is electrically connected to the sample.

[0014] The electrochemical workstation is electrically connected to the reference electrode, the auxiliary electrode, and the conductor. The electrochemical workstation is used to perform electrochemical tests on the sample and convert the test results into quantifiable electrical signals.

[0015] By using electrodes and an electrochemical workstation, in-situ, online electrochemical testing of samples in an annular flow field can be performed, solving the problem that existing devices are difficult to deploy electrodes for real-time corrosion monitoring due to limited space.

[0016] Preferably, the end of the auxiliary electrode that communicates with the inner cavity of the experimental pipe is bent downstream of the fluid medium.

[0017] By bending the end of the auxiliary electrode downstream, the disturbance of the flow field in the annular gap by the auxiliary electrode is reduced, making the test environment closer to the actual working conditions of the sleeve annular gap.

[0018] Preferably, it further includes a second detection component, the second detection component including an image monitoring device, and the sidewall of the experimental pipe is at least partially made of a transparent material;

[0019] The image monitoring device can monitor the state of the fluid medium within the annular gap through the transparent portion of the experimental pipe.

[0020] The image monitoring equipment can directly visualize and observe samples and flow fields through the transparent pipe wall, providing a basis for the correlation analysis of flow field characteristics and corrosion behavior.

[0021] The second aspect of the present invention provides an inner pipe outer wall erosion corrosion test system, including the inner pipe outer wall erosion corrosion test pipeline as described in the first aspect, and further including a power circulation device and a signal processing device, wherein the power circulation device is used to drive the fluid medium to flow in the test pipeline;

[0022] The power circulation device includes a circulation pipeline, a liquid storage tank, and a power pump. The inlet end of the circulation pipeline is connected to the liquid storage tank, and the power pump and the experimental pipeline are connected in series on the circulation pipeline.

[0023] The signal processing device is communicatively connected to the image monitoring equipment and / or the electrochemical workstation, and is used to analyze the state parameters of the fluid medium and / or the corrosion state parameters of the sample.

[0024] This experimental system can simulate the flow field conditions in actual working conditions and directly observe and analyze the corrosion behavior and flow field characteristics of the samples.

[0025] Preferably, the power circulation device further includes a gas storage cylinder and a gas pipeline, wherein a first end of the gas pipeline is connected to the gas storage cylinder, and a second end is connected to the liquid storage tank and / or the circulation pipeline.

[0026] The gas phase is injected into the liquid phase through gas storage cylinders and gas pipelines to simulate gas-containing multiphase flow in actual engineering.

[0027] A third aspect of the present invention provides a method for testing the erosion corrosion of the outer wall of an inner pipe, using the erosion corrosion testing system for the outer wall of an inner pipe as described in the second aspect, comprising the following steps:

[0028] S1: The sample is fixed in the inner cavity of the experimental pipe by the sample fixing assembly;

[0029] S2: Add the fluid medium to the storage tank;

[0030] S3: Adjust the frequency of the power pump to stabilize the flow rate of the fluid medium within a predetermined range; adjust the gas supply flow rate of the gas storage cylinder to stabilize the gas content of the fluid medium within a preset range;

[0031] S4: Record the start time of scouring corrosion, monitor the flow rate and pressure parameters of the fluid medium, and use the image monitoring device to capture the fluid state and particle and bubble distribution of the fluid medium in the experimental pipeline, and analyze and obtain the collision and aggregation rules of particles and bubbles.

[0032] S5: Connect the sample, the reference electrode, and the auxiliary electrode to the electrochemical workstation. Use the sample as the working electrode, and the reference electrode and the auxiliary electrode to form a three-electrode system. The electrochemical workstation tests the electrochemical parameters of the sample online and outputs the electrochemical test curve simultaneously.

[0033] S6: After the scouring corrosion is completed, the sample is taken out; the scouring corrosion morphology of the sample is observed and the corrosion product composition is analyzed; the mass loss of the sample before and after the experiment is measured, and the corrosion rate is calculated by the weight loss method.

[0034] This method comprehensively analyzes the erosion and corrosion behavior of samples through three methods: image recording, electrochemical testing, and weight loss measurement, which can more fully reveal the damage mechanism of the outer wall of the inner tube under multiphase flow conditions.

[0035] Preferably, steps S1-S6 are repeated two or more times, and the sample and the fluid medium in the storage tank are replaced before each start of S1.

[0036] By conducting multiple parallel experiments, the reliability and repeatability of the experimental results were improved. Attached Figure Description

[0037] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0038] Figure 1 This is a schematic diagram of the structure of the experimental pipeline for erosion corrosion of the inner tube outer wall provided in an embodiment of the present invention.

[0039] Figure 2 This is a cross-sectional view of the experimental pipeline for erosion corrosion of the inner tube outer wall provided in an embodiment of the present invention.

[0040] Figure 3 This is a schematic diagram of the structure of the fixing ring provided in an embodiment of the present invention.

[0041] Figure 4 This is a schematic diagram showing the connection between the connecting rod and the sample provided in an embodiment of the present invention.

[0042] Figure 5 This is a schematic diagram of the experimental system for scouring corrosion of the outer wall of an inner tube provided in an embodiment of the present invention.

[0043] Figure 6 This is a flowchart of the experimental method for erosion corrosion of the outer wall of the inner tube provided in an embodiment of the present invention.

[0044] Explanation of reference numerals in the attached figures:

[0045] Experimental pipe 1, fixed ring 2, outer ring 3, inner ring 4, connecting column 5, first connecting rod 6, second connecting rod 7, reference electrode 8, auxiliary electrode 9, conductor 10, electrochemical workstation 11, image monitoring equipment 12, signal processing device 13, circulation pipe 14, liquid storage tank 15, power pump 16, first pressure gauge 17, second pressure gauge 18, electromagnetic flowmeter 19, exhaust valve 20, exhaust back pressure valve 21, stirring device 22, gas storage bottle 23, gas pipe 24, pressure reducing valve 25, gas flowmeter 26, one-way valve 27, sample 28. Detailed Implementation

[0046] 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. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0047] To enable those skilled in the art to better understand the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0048] The following provides some embodiments of the experimental pipeline for erosion corrosion testing of the inner tube outer wall of the present invention.

[0049] refer to Figure 1 and Figure 2In some embodiments, the inner tube outer wall erosion corrosion test pipeline includes an experimental pipe 1 and a sample fixing assembly. The sample fixing assembly is used to fix the sample 28 in the inner cavity of the experimental pipe 1. After the sample 28 is fixed, an annular gap is formed between the outer wall of the sample 28 and the inner wall of the experimental pipe 1. The annular gap is used for the flow of fluid medium.

[0050] Optionally, the experimental pipe 1 can be made of transparent materials such as PMMA (polymethyl methacrylate), polycarbonate, or fiberglass to allow for visual observation of the inside of the pipe. Alternatively, if there is no need for visual observation of the sample 28 and flow field inside the pipe, the experimental pipe 1 can also be made of opaque materials such as engineering plastics. It should be noted that, while meeting the experimental and testing requirements, the experimental pipe 1 is preferably made of the same material and diameter as the outer pipe of the actual casing to more realistically simulate the actual casing working conditions. Preferably, the ends of the experimental pipe 1 are provided with flanges for connection to external pipelines. Preferably, the experimental pipe 1 can be set in multiple sections connected in series to conduct multiple sets of comparative experiments simultaneously, improving experimental efficiency; furthermore, the materials, specifications, surface treatments, etc., of the samples in different sections of the experimental pipe can be exactly the same or different.

[0051] It should be noted that, normally, after being fixed by the sample fixing assembly, sample 28 is coaxial with experimental pipe 1. However, when simulating the annular flow field of some eccentric sleeves, sample 28 may not be coaxial with experimental pipe 1. In short, the relative position of sample 28 and experimental pipe 1 is not specifically limited and needs to be set according to the actual working conditions of the sleeve being simulated. Optionally, the relative position of sample 28 and experimental pipe 1 can be adjusted by setting various specifications of sample fixing assemblies, or by designing adjustable sample fixing assemblies. In addition, the form of sample fixing assemblies is also diverse. For example, sample 28 can be supported and fixed by radial support rods or by support rings, as long as an annular gap is maintained between sample 28 and the inner wall of experimental pipe 1, while minimizing the interference of sample fixing assemblies on the flow field. The connection method between sample 28 and sample fixing assemblies is also diverse, such as by insertion, bonding, magnetic attraction, clamping, etc.

[0052] It should be noted that the above embodiment constructs an annular flow field to simulate the erosion and corrosion environment of the outer wall of the inner pipe. As for measuring the erosion and corrosion of sample 28, it can be done by setting a detection interface on the experimental pipe 1 and connecting it to an external detection device or by observing or detecting it online during the experiment. However, online detection is not necessary, so the detection interface is not necessary either. After simulating erosion for a preset time under specific flow field conditions, sample 28 can be taken out of the experimental pipe 1 and the erosion and corrosion can be measured. For example, sample 28 can be weighed and the corrosion rate can be calculated by the weight loss method.

[0053] refer to Figure 2 and Figure 3 In some embodiments, the sample fixing assembly includes two fixing rings 2, which are spaced apart along the axial direction of the experimental pipe 1. Each fixing ring 2 includes an outer ring 3 and an inner ring 4, which are fixedly connected by several connecting posts 5. To minimize the interference of the connecting posts 5 on the annular flow field, the number of connecting posts 5 is usually no more than three, and they are evenly distributed circumferentially. Furthermore, the radial dimension of the connecting posts 5 is kept as small as possible while still being able to stably support the inner ring 4, the sample 28, and the impact force of the flow field. Further, the cross-section of the connecting posts 5 is circular or streamlined to reduce interference with the flow field.

[0054] The outer ring 3 is fixedly connected to the experimental pipe 1. For example, the end of the experimental pipe 1 is provided with a flange, and a circular fitting groove is opened on the flange. The diameter of the fitting groove is larger than the inner diameter of the experimental pipe 1. The outer ring 3 is fitted into the fitting groove, and the inner diameter of the outer ring 3 is equal to the inner diameter of the experimental pipe 1. That is, the inner wall of the outer ring 3 is flush with the inner wall of the experimental pipe 1 to reduce interference with the annular flow field. Alternatively, the end face of the outer ring 3 mates with the end face of the experimental pipe 1, and the outer ring 3 is connected and fixed to the experimental pipe by means of clamps or waterproof tape, etc., with the inner wall of the outer ring 3 flush with the inner wall of the experimental pipe 1. In some simplified embodiments, the outer wall of the outer ring 3 can directly contact and fit with the inner wall of the experimental pipe 1, supporting the fixing ring 2 inside the experimental pipe 1. However, this method, because the outer ring 3 protrudes from the inner wall of the experimental pipe 1, will interfere with the flow field to some extent. Therefore, the radial thickness of the outer ring 3 should be minimized.

[0055] The inner ring 4 is located inside the cavity of the experimental pipe 1, and both ends of the sample 28 are fixedly connected to the inner ring 4 of the two fixed rings 2 respectively. Exemplarily, both ends of the sample 28 are inserted into the inner ring 4 to support the sample 28. To make the outer wall of the inner ring 4 flush with the outer wall of the sample 28, a connector can be provided at the end of the sample 28. The diameter of the connector is smaller than the diameter of the sample 28, and the diameter of the inner ring 4 is equal to the diameter of the sample 28. After the connector is inserted into the annular hole of the inner ring 4, the outer wall of the sample 28 is flush with the outer wall of the inner ring 4. Alternatively, a threaded head can be provided at the end of the sample 28, and the inner wall of the inner ring 4 can be provided with internal threads. After the threaded head is screwed into the internal threads, the outer wall of the sample 28 is flush with the outer wall of the inner ring 4. Alternatively, the sample 28 can be fixedly connected to the inner ring 4 by adhesive bonding, after which the outer wall of the sample 28 is flush with the outer wall of the inner ring 4.

[0056] Furthermore, the inner ring 4 of the fixing ring 2 can be configured in various sizes to accommodate samples 28 of different diameters. In addition, the relative positions of the inner ring 4 and the outer ring 3 of the fixing ring 2 can be configured as concentric or in various eccentric sizes to accommodate different relative positions of the sample 28 and the test pipe.

[0057] refer to Figure 2and Figure 4 In some embodiments, the sample fixing assembly further includes a first connecting rod 6 and a second connecting rod 7. Preferably, the diameter of the connecting rod is the same as the diameter of the sample 28. The first end of the first connecting rod 6 and the first end of the second connecting rod 7 are respectively fixedly connected to the inner rings 4 of the two fixing rings 2, and the second end of the first connecting rod 6 and the second end of the second connecting rod 7 are respectively fixedly connected to both ends of the sample 28. Exemplarily, the fixed connection between the connecting rod and the sample 28 and the fixed connection between the connecting rod and the inner ring 4 can be achieved by insertion, threaded connection, bonding, etc. The first connecting rod 6 and the second connecting rod 7 increase the distance between the sample 28 and the fixing rings 2, further avoiding interference of the fixing rings 2 on the flow field near the sample 28. Furthermore, the connecting rod can be provided with various different length specifications. By changing the connecting rod of different lengths, the axial position of the sample 28 can be adjusted, for example, making the sample 28 closer to the upstream or downstream, to achieve the testing of corrosion conditions at different locations.

[0058] Preferably, the fixing ring 2 and the connecting rod can be made of insulating materials such as PLA, ABS, or UV-cured resin to avoid galvanic corrosion caused by conductive materials or interference with electrochemical test signals.

[0059] refer to Figure 1 and Figure 2 In some embodiments, the experimental pipeline for erosion corrosion of the inner tube outer wall includes a first detection component. The first detection component includes a reference electrode 8, an auxiliary electrode 9, a conductor 10, and an electrochemical workstation 11. The reference electrode 8 and the auxiliary electrode 9 are both connected to the inner cavity of the experimental pipeline 1. The conductor 10 is electrically connected to the sample 28. An insulating layer is provided on the outside of the conductor 10 to insulate the conductor 10 from the fluid medium. Exemplarily, three threaded holes are pre-set on the side wall of the experimental pipeline 1. A mating nut is screwed into each threaded hole. The mating nut has an axially penetrating central hole. The reference electrode 8, the auxiliary electrode 9, and the conductor 10 respectively pass through the central holes on the three mating nuts into the inner cavity of the experimental pipeline 1.

[0060] Exemplarily, conductor 10 and sample 28 are electrically connected by welding, and the welded area is sealed with epoxy resin to avoid galvanic corrosion and electrical signal distortion. Further, a sealing ring is provided in the central hole, or it is sealed with adhesive after the electrode or wire is inserted. Preferably, the mating nut and experimental pipe 1 are made of the same material, such as PMMA, polycarbonate, or fiberglass. Preferably, the reference electrode 8 and auxiliary electrode 9 are installed downstream of sample 28 to reduce interference of the electrodes on the flow field around sample 28.

[0061] In this embodiment, sample 28 serves as the working electrode, and the oxidation / reduction reaction occurring on its surface is the target of the electrochemical test. Optionally, the reference electrode 8 can be any one of a saturated calomel electrode, a silver / silver chloride electrode, or a copper / copper sulfate electrode. Since the reference electrode 8 carries virtually no current, its potential remains largely unchanged during the test, providing a stable and known electrode potential as a benchmark for measuring or controlling the potential of the working electrode. The auxiliary electrode 9 can be made of materials such as platinum sheet or graphite, possessing high conductivity, chemical inertness that prevents oxidation or reduction under test conditions, and a large surface area to reduce polarization effects. The auxiliary electrode 9 forms a current loop with the working electrode.

[0062] Preferably, the end of the auxiliary electrode 9 that connects to the inner cavity of the experimental pipe 1 is bent downstream of the fluid medium to be parallel to the axis of the sample 28, so as to reduce the obstruction of the auxiliary electrode 9 to the flow. The reference electrode 8 itself is small in size and has minimal interference with the flow field, so it does not need to be bent.

[0063] The electrochemical workstation 11 is electrically connected to the reference electrode 8, the auxiliary electrode 9, and the conductor 10. The electrochemical workstation 11 is used to perform electrochemical tests on the sample 28 and convert the test results into quantifiable electrical signals. The electrochemical workstation 11 monitors the potential difference between the reference electrode 8 and the working electrode, and adjusts the output of the auxiliary electrode 9 to stabilize the working electrode potential at a set value; simultaneously, it acquires the current between the working electrode and the auxiliary electrode 9 and converts it into a quantifiable electrical signal.

[0064] For example, the electrochemical workstation 11 acquires the potential difference between the reference electrode 8 and the sample 28 in real time through a high-impedance measurement circuit. At the same time, it automatically adjusts the output current of the auxiliary electrode 9 according to the preset test mode to keep the potential of the sample 28 precisely at the target value. The output current flows through the auxiliary electrode 9, the electrolyte solution and the sample 28 to form a closed loop. The electrochemical workstation 11 measures the current response in the loop simultaneously and converts the measured potential and current signals into digital electrochemical parameters after analog-to-digital conversion, filtering and amplification. Finally, it outputs the quantifiable electrical signal to the host computer for analysis and storage.

[0065] In some embodiments, the sidewall of the experimental pipe 1 is at least partially made of a transparent material. Optionally, the experimental pipe 1 may be entirely made of a transparent material, or it may only have a transparent material in a localized area to form a transparent observation window. The inner pipe outer wall erosion corrosion experimental pipeline includes a second detection component, which includes an image monitoring device 12. Exemplarily, the image monitoring device 12 may be a high-speed camera, an industrial camera, or a camera system with a telephoto lens. The image monitoring device 12 can monitor the state of the fluid medium within the annular gap through the transparent portion of the experimental pipe 1, such as the particle and bubble distribution, flow pattern transition, and corrosion morphology changes on the surface of the sample 28 during multiphase flow erosion corrosion.

[0066] The following are some embodiments of the experimental system for scouring corrosion of the inner tube outer wall of the present invention.

[0067] refer to Figure 5 In some embodiments, the inner pipe outer wall erosion corrosion test system includes the inner pipe outer wall erosion corrosion test pipeline described in the above embodiments, and further includes a power circulation device and a signal processing device 13. The power circulation device is used to drive the fluid medium to flow within the test pipeline 1. The power circulation device includes a circulation pipeline 14, a liquid storage tank 15, and a power pump 16. The inlet end of the circulation pipeline 14 is connected to the liquid storage tank 15, and the power pump 16 and the test pipeline 1 are connected in series on the circulation pipeline 14. Exemplarily, the power pump 16 can be a centrifugal pump, a screw pump, a diaphragm pump, or an axial flow pump.

[0068] Preferably, the circulation pipeline 14 is sequentially equipped with a first pressure gauge 17 located at the outlet end of the power pump 16, a second pressure gauge 18 located at the inlet end of the experimental pipeline, and an electromagnetic flowmeter 19. The storage tank 15 is equipped with a third pressure gauge. Each pressure gauge is used to monitor the pressure at various points in the circulation pipeline and the storage tank 15. The electromagnetic flowmeter 19 is used to monitor the flow rate within the circulation pipeline 14. Furthermore, the storage tank 15 is also equipped with an exhaust valve 20 and an exhaust back pressure valve 21 for depressurizing the system in case of overpressure. Furthermore, the storage tank 15 is equipped with a stirring device 22, including a stirring shaft and stirring blades, to ensure thorough mixing of the different phases of the fluid medium.

[0069] Preferably, the power circulation device includes a control box, which adjusts the flow rate in the circulation pipe 14 by adjusting the power of the power pump 16, and adjusts the start / stop and speed of the stirring device 22.

[0070] Preferably, the outlet end of the circulation pipe 14 is also connected to the liquid storage tank 15 to realize the circulation of the fluid medium. Of course, the outlet end of the circulation pipe 14 may not be connected to the liquid storage tank 15, and the fluid medium may flow through the circulation pipe 14 in a single pass.

[0071] The signal processing device 13 is communicatively connected to the image monitoring device 12 and / or the electrochemical workstation 11 for analyzing the state parameters of the fluid medium and / or the corrosion state parameters of the sample 28. Exemplarily, the signal processing device 13 can be a computer with a software platform installed, capable of simultaneously acquiring electrical signals and image data and performing correlation analysis. Further, the signal processing device 13 can convert the electrical signals into open-circuit potential diagrams, Nyquist plots, Bode plots, and polarization curves, and can select different equivalent circuit diagrams according to the material to fit the electrical signals, determine their polarization resistance Rp, and apply the Stern-Geary equation: Where B is the Stern-Geary coefficient, determined by the Tafel slopes ba and bc of the cathode and anode polarization curves: And using Faraday's law, the annual corrosion rate is obtained: Where M is the atomic weight of the metal, n is the number of transferred electrons, and ρ is the density of the test sample 28.

[0072] Simultaneously, the signal processing device 13 can use image processing software to analyze the relationship between fluid dynamic parameters such as flow pattern, flow state, and flow velocity inside the experimental pipe section of the test sample 28 on the outer wall of the inner pipe and the erosion corrosion behavior. Simultaneously, numerical simulation software can be used to construct a relevant simulation model based on the shape of the experimental pipe 1. By setting boundary conditions according to parameters such as the multiphase flow medium and flow velocity, information such as flow velocity, wall shear force, and flow corrosion amount at different locations within the pipe cross-section can be obtained. By comparing the experimental results with the numerical simulation results, the mechanism of multiphase flow erosion corrosion on the outer wall of the pipe can be studied in depth from both fluid dynamics and electrochemistry perspectives and their coupling effects.

[0073] Optionally, the signal processing device 13 may also include a data storage module and a display module to display corrosion rate and flow field images in real time.

[0074] In some embodiments, the power circulation device further includes a gas storage cylinder 23 and a gas pipeline 24. A first end of the gas pipeline 24 is connected to the gas storage cylinder 23, and a second end is connected to a liquid storage tank 15 or a circulation pipeline 14, or both. Further, the gas pipeline 24 is equipped with a pressure reducing valve 25, a gas flow meter 26, and a check valve 27. The pressure reducing valve 25 and the gas flow meter 26 are used to control the inlet pressure and flow rate, and the check valve 27 is used to prevent backflow. Dissolved gases or insoluble gas phases can be added to the fluid medium through the gas storage cylinder 23 and the gas pipeline 24.

[0075] The following are some examples of the experimental method for scouring corrosion of the outer wall of the inner tube according to the present invention.

[0076] refer to Figure 6In some embodiments, the inner tube outer wall erosion corrosion test method adopts the inner tube outer wall erosion corrosion test system in the above embodiments, including the following steps:

[0077] S1: The sample 28 is fixed in the inner cavity of the experimental pipe 1 by the sample fixing assembly, so that an annular gap is formed between the outer wall of the sample 28 and the inner wall of the experimental pipe 1.

[0078] S2: Add the fluid medium to the storage tank 15; the fluid medium contains one or more liquid phase substances, or particles can be added to the liquid phase to form a liquid-solid mixture; for example, the fluid medium can be a corrosive solution without sand particles, deionized water with sand particles added, a corrosive solution with sand particles added, etc.

[0079] S3: Based on the monitoring values ​​of each pressure gauge and electromagnetic flowmeter 19, the flow rate of the fluid medium is stabilized within a predetermined range by adjusting the frequency of the power pump 16; at the same time, the gas supply flow rate of the gas storage cylinder 23 is adjusted by adjusting the opening of the pressure reducing valve 25 and according to the monitoring value of the gas flowmeter 26, so that the gas content of the fluid medium is stabilized within a preset range.

[0080] S4: Record the start time of scouring corrosion, monitor the flow rate and pressure parameters of the fluid medium, and use the image monitoring device 12 to capture the fluid state and particle and bubble distribution of the fluid medium in the experimental pipeline 1. Then, use image processing software to analyze and obtain the collision and aggregation patterns of particles and bubbles.

[0081] S5: Connect sample 28, reference electrode 8, and auxiliary electrode 9 to electrochemical workstation 11. With sample 28 as the working electrode, the reference electrode and auxiliary electrode 9 form a three-electrode system. Electrochemical workstation 11 tests the electrochemical parameters of sample 28 online and outputs the electrochemical test curve simultaneously. It should be noted that steps S4 and S5 can be performed simultaneously, i.e., through visual monitoring and electrochemical monitoring.

[0082] S6: After completing the scouring corrosion, take out sample 28, observe the scouring corrosion morphology and analyze the composition of corrosion products; remove the corrosion products from the surface of sample 28, clean and dry it and weigh it; measure the mass loss of sample 28 before and after the experiment, and calculate the corrosion rate using the weight loss method.

[0083] The formula for calculating weightlessness is: Where CR is the corrosion rate of the sample, mm / a; m0 is the sample mass before the experiment, g; m1 is the sample mass after corrosion and removal of corrosion products, g; and S is the exposed area of ​​the sample, cm². 2 t is the corrosion time, in hours; ρ is the density of the sample, in g / cm³. 3 .

[0084] To ensure the reliability of experimental data, in some embodiments, steps S1-S6 are repeated more than twice, i.e., multiple parallel experiments are performed to meet statistical requirements and reduce random errors; before each start of S1, the fluid medium in sample 28 and storage tank 15 is changed to avoid inconsistencies in experimental conditions caused by changes in the state of sample 28 and fluid medium after the previous experiment.

[0085] It should be noted that in this specification, relational terms such as first and second are used only to distinguish one entity from several other entities, and do not necessarily require or imply any such actual relationship or order between these entities.

[0086] This article uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. It should be noted that those skilled in the art can make several improvements and modifications to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the protection scope of the present invention.

Claims

1. A test pipeline for erosion corrosion of the outer wall of an inner tube, characterized in that, Includes experimental tubing (1) and sample fixing components; The sample fixing assembly is used to fix the sample (28) in the inner cavity of the experimental pipe (1). After the sample (28) is fixed, an annular gap is formed between the outer wall of the sample (28) and the inner wall of the experimental pipe (1). The annular gap is used to allow the flow of fluid medium.

2. The experimental pipeline for erosion corrosion testing of the inner tube's outer wall according to claim 1, characterized in that, The sample fixing assembly includes two fixing rings (2), which are spaced apart along the axial direction of the experimental pipe (1); The fixing ring (2) includes an outer ring (3) and an inner ring (4). The outer ring (3) and the inner ring (4) are fixedly connected by several connecting posts (5). The outer ring (3) is fixedly connected to the experimental pipe (1). The inner ring (4) is located in the inner cavity of the experimental pipe (1). The two ends of the sample (28) are respectively fixedly connected to the inner rings (4) of the two fixing rings (2).

3. The experimental pipeline for erosion corrosion testing of the inner tube's outer wall according to claim 2, characterized in that, The sample fixing assembly further includes a first connecting rod (6) and a second connecting rod (7). The first end of the first connecting rod (6) and the first end of the second connecting rod (7) are respectively fixedly connected to the inner rings (4) of the two fixing rings (2). The second end of the first connecting rod (6) and the second end of the second connecting rod (7) are respectively fixedly connected to the two ends of the sample (28).

4. The experimental pipeline for erosion corrosion testing of the inner tube's outer wall according to any one of claims 1-3, characterized in that, It also includes a first detection component, which includes a reference electrode (8), an auxiliary electrode (9), a conductor (10) and an electrochemical workstation (11). The reference electrode (8) and the auxiliary electrode (9) are both connected to the inner cavity of the experimental pipe (1), and the conductor (10) is electrically connected to the sample (28). The electrochemical workstation (11) is electrically connected to the reference electrode (8), the auxiliary electrode (9) and the conductor (10). The electrochemical workstation (11) is used to perform electrochemical tests on the sample (28) and convert the test results into quantifiable electrical signals.

5. The experimental pipeline for erosion corrosion testing of the inner tube's outer wall according to claim 4, characterized in that, The auxiliary electrode (9) is connected to the inner cavity of the experimental pipe (1) at one end, which is bent downstream of the fluid medium.

6. The experimental pipeline for erosion corrosion testing of the inner tube's outer wall according to claim 4, characterized in that, It also includes a second detection component, which includes an image monitoring device (12), and the sidewall of the experimental pipe (1) is at least partially made of transparent material; The image monitoring device (12) can monitor the state of the fluid medium in the annular gap through the transparent part of the experimental pipe (1).

7. A test system for erosion corrosion of the outer wall of an inner pipe, characterized in that, The test pipeline for scouring corrosion of the inner tube outer wall as described in claim 6, also includes a power circulation device and a signal processing device (13), wherein the power circulation device is used to drive the fluid medium to flow in the test pipeline (1); The power circulation device includes a circulation pipe (14), a liquid storage tank (15) and a power pump (16). The inlet end of the circulation pipe (14) is connected to the liquid storage tank (15), and the power pump (16) and the experimental pipe (1) are connected in series on the circulation pipe (14). The signal processing device (13) is communicatively connected to the image monitoring device (12) and / or the electrochemical workstation (11) for analyzing the state parameters of the fluid medium and / or the corrosion state parameters of the sample (28).

8. The experimental system for erosion corrosion of the outer wall of an inner tube according to claim 7, characterized in that, The power circulation device also includes a gas storage cylinder (23) and a gas pipeline (24). The first end of the gas pipeline (24) is connected to the gas storage cylinder (23), and the second end is connected to the liquid storage tank (15) and / or the circulation pipeline (14).

9. A method for testing the erosion corrosion of the outer wall of an inner pipe, characterized in that, The test system for erosion corrosion of the inner tube outer wall as described in claim 8 includes the following steps: S1: The sample (28) is fixed in the inner cavity of the experimental tube (1) by the sample fixing assembly; S2: Add the fluid medium to the storage tank (15). S3: Adjust the frequency of the power pump (16) to stabilize the flow rate of the fluid medium within a predetermined range; adjust the gas supply flow rate of the gas storage cylinder (23) to stabilize the gas content of the fluid medium within a preset range; S4: Record the start time of scouring corrosion, monitor the flow rate and pressure parameters of the fluid medium, and use the image monitoring device (12) to capture the fluid state and particle and bubble distribution of the fluid medium in the experimental pipeline (1), and analyze and obtain the collision and aggregation rules of particles and bubbles; S5: Connect the sample (28), the reference electrode (8), and the auxiliary electrode (9) to the electrochemical workstation (11). Use the sample (28) as the working electrode, and the reference electrode (8) and the auxiliary electrode (9) to form a three-electrode system. The electrochemical workstation (11) tests the electrochemical parameters of the sample (28) online and outputs the electrochemical test curve simultaneously. S6: After the scouring corrosion is completed, the sample (28) is taken out; the scouring corrosion morphology of the sample (28) is observed and the corrosion product composition is analyzed; the mass loss of the sample (28) before and after the experiment is measured, and the corrosion rate is calculated by the weight loss method.

10. The test method for erosion corrosion of the outer wall of the inner tube according to claim 9, characterized in that, Repeat steps S1-S6 more than twice, replacing the fluid medium in the sample (28) and the storage tank (15) before each start of S1.

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