A multi-phase erosion and flow corrosion coupling damage accelerated test unit and test structure

Abstract

The application provides a multi-phase erosion and flow corrosion coupling damage accelerated test unit and test structure, which comprises a circulating main pipeline and a central cone arranged concentrically and separately in the circulating main pipeline; the central cone has tapered heads at two ends and a body between the two tapered heads; a circle of sample mounting grooves is arranged on the inner side wall of the circulating main pipeline or the outer wall of the central cone in a circumferential direction, the sample mounting grooves are stepped grooves with wide groove bottoms and narrow groove openings, and a plurality of sample pieces arranged in a circumferential direction are embedded and clamped in the sample mounting grooves, and adjacent sample pieces are insulated by insulation fixing pieces; a probe is installed on the inner wall opposite to the body of the central cone.

Description

TECHNICAL FIELD

[0001] The present application mainly relates to the field of petrochemical and coal chemical safety, in particular to a multi-working-condition multiphase erosion and flow corrosion coupling damage accelerated test unit and test structure, which is used for quickly researching single or coupling mechanism and law of multiphase erosion, flow corrosion and cavitation in complex environment, providing data support for damage safety boundary setting and risk assessment of pressure-bearing equipment, and guiding damage rate prediction and safety prevention and control of pressure-bearing equipment in complex environment. BACKGROUND

[0002] The service environment in the pressure-bearing equipment of petrochemical and coal chemical plants is harsh, and there are multiple mechanism coupling damages such as multiphase erosion, cavitation and multi-medium flow corrosion, which often cause unplanned shutdown of the plant and seriously affect the long-period safe operation of the plant. At present, in order to prevent multiple mechanism coupling damages, the corrosion rate and critical prevention value under different process parameters (such as flow rate and corrosion medium concentration) of each damage mechanism are often queried based on API 571, GB / T 30579 and other standards and metal corrosion manuals. However, the existing data are mostly for single damage mechanism, and there is a lack of prediction data and models of multiple mechanism coupling damage rate such as multiphase erosion, cavitation and multi-medium flow corrosion, and the mechanism of multiple mechanism coupling is also unknown. Therefore, it is necessary to simulate the harsh service environment on site through experiments, to study the mechanism of these multiple mechanism couplings, to measure the damage boundary and damage rate under coupling damage, so as to effectively guide the corrosion prediction and safety prevention and control of pressure-bearing equipment in complex environment.

[0003] At present, there are three kinds of experimental test devices commonly used at home and abroad, namely rotating stirring type, jet type and loop type. The rotating stirring type and jet type sample devices cannot simulate the influence of flow conditions on damage, and there are some differences from the real damage process. The loop type test device is mostly used for simulating erosion and flow corrosion under different flow conditions in the water sand / oil sand system of actual long-distance pipelines and natural gas / oil gas exploitation pipelines, and there is rarely a device for simulating erosion and corrosion under harsh conditions of petrochemical and coal chemical plants; at the same time, the experimental period of the device is long, and different branch test pipelines are mostly used for synchronous test of multiple working conditions, which leads to large equipment, difficult operation and control, and low experimental efficiency; in addition, the existing loop type test device mostly cannot do experimental research on multiphase cavitation and erosion under high flow rate of more than 20 m / s. SUMMARY

[0004] In order to greatly improve the experimental efficiency of the loop test device and shorten the experimental period, efficiently study the multi-mechanism coupling damage mechanism and law of multiphase erosion, cavitation erosion, multi-medium flow corrosion and the like under multiple working conditions, and without increasing the volume of the loop test device, a multiphase erosion and flow corrosion coupling damage accelerated test unit and test structure are designed, the problem of long experimental period caused by multiple experimental working conditions is effectively solved, the multiphase erosion and flow corrosion damage pipeline accelerated test under multiple working conditions is realized, data support is provided for setting of a damage safety boundary of a pressure-bearing equipment and risk assessment, and corrosion prediction and safety control of the pressure-bearing equipment under a complex environment are guided.

[0005] The technical scheme adopted by the present application is as follows:

[0006] A multiphase erosion and flow corrosion coupling damage accelerated test unit is characterized by comprising a circulating main pipeline and a central cone body arranged concentrically and separately in the circulating main pipeline.

[0007] The central cone body has tapered heads at two ends and a body part between the two tapered heads.

[0008] A circle of sample mounting grooves is arranged on the inner side wall of the circulating main pipeline or the outer wall of the central cone body in the circumferential direction, the sample mounting groove is a stepped groove with a wide groove bottom and a narrow groove opening, a plurality of sample pieces arranged in the circumferential direction are embedded and clamped in the sample mounting groove, and adjacent sample pieces are insulated by insulation fixing pieces.

[0009] A probe is installed on the inner wall opposite to the body part of the circulating main pipeline and the central cone body.

[0010] The multiphase erosion and flow corrosion coupling damage accelerated test unit, wherein a sample fixing groove for a single sample piece and a single insulation fixing piece to enter and exit alternately is arranged on one side of the axial direction of the sample mounting groove, the sample fixing piece is fixed in the sample fixing groove, and a rubber pad is used to insulate the side of the sample fixing piece in contact with the sample piece, so that the sample piece in the sample mounting groove cannot be separated from the axial direction.

[0011] The multiphase erosion and flow corrosion coupling damage accelerated test unit, wherein the circulating main pipeline is composed of an inlet test section and an outlet test section, or is composed of an inlet test section, an outlet test section and at least one intermediate test section connected between the inlet test section and the outlet test section.

[0012] The multiphase erosion and flow corrosion coupling damage accelerated test unit, wherein the inlet end of the inlet test section is connected with a pipeline diameter reduction structure, and the outlet end of the outlet test section is connected with a pipeline diameter expansion structure.

[0013] The polyphase erosion and flow corrosion coupling damage accelerated test unit, wherein the center cone has two tapered heads at two ends and a body between the two tapered heads, at least three protrusions are arranged on the outer side wall of the body in the circumferential direction corresponding to the inlet test section and the outlet test section, and a fixing nut is arranged corresponding to each protrusion of the inlet test section and the outlet test section, the fixing nut is screwed into the protrusion, and the center cone is fixed in the inlet test section and the outlet test section in a concentric and separated state.

[0014] The polyphase erosion and flow corrosion coupling damage accelerated test unit, wherein the probe is a wall shear force probe and / or a three-electrode corrosion probe.

[0015] The polyphase erosion and flow corrosion coupling damage accelerated test unit, wherein the center cone is a center tapered expansion cone, a center tapered contraction cone, a center tapered expansion-contraction cone or a center tapered contraction-expansion cone, and the sample piece mounting groove is arranged on each tapered expansion surface and / or tapered contraction surface.

[0016] The polyphase erosion and flow corrosion coupling damage accelerated test unit, wherein the bottom surface of the sample piece mounting groove arranged on each tapered expansion surface and / or tapered contraction surface is planar or curved.

[0017] A polyphase erosion and flow corrosion coupling damage accelerated test structure, comprising a pressurizing pump, a stirring pump and a circulating pipeline connecting the pressurizing pump and the stirring pump in a loop, and the polyphase erosion and flow corrosion coupling damage accelerated test unit is connected to the stable straight pipe area of the circulating pipeline.

[0018] The polyphase erosion and flow corrosion coupling damage accelerated test unit and the test structure do not increase the volume of the loop test device, effectively solve the problem of long test period caused by multiple test conditions, realize the polyphase erosion and flow corrosion damage pipeline accelerated test under multiple conditions, provide data support for the damage safety boundary setting and risk assessment of pressure-bearing equipment, and guide the corrosion prediction and safety prevention and control of pressure-bearing equipment in complex environments. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 is a sectional view of the first embodiment of the polyphase erosion and flow corrosion coupling damage accelerated test unit;

[0020] Figure 2 , Figure 3 are respectively Figure 1 the perspective view of the inlet test section and the outlet test section in

[0021] Figure 4 is the perspective view of the center cone in Figure 1

[0022] ​Figure 5 、 Figure 6 、 Figure 7 、 Figure 8 are respectively the perspective view of shear force probe, sample sheet, insulating fixing part, sample fixing part;

[0023] Figure 9 、 Figure 10 are respectively the schematic diagram of two different cross-sectional shapes of pipeline sample installation groove;

[0024] Figure 11 is the sectional view of the second embodiment of the multiphase erosion and flow corrosion coupling damage accelerated test unit;

[0025] Figure 12 is the perspective view of the central vertebral body in Figure 11 ;

[0026] Figure 13 is the A-A sectional view of the first sample sheet installation structure of Figure 12 ;

[0027] Figure 14 、 Figure 15 、 Figure 16 are respectively the perspective view of the bevel sample sheet, bevel insulating fixing part, bevel sample fixing part used by the first sample sheet installation structure of Figure 12 ;

[0028] Figure 17 is the A-A sectional view of the second sample sheet installation structure of Figure 12 ;

[0029] Figure 18 、 Figure 19 、 Figure 20 are respectively the perspective view of the curved sample sheet, curved insulating fixing part, curved sample fixing part used by the second sample sheet installation structure of Figure 12 ;

[0030] Figure 21 is the sectional view of the third embodiment of the multiphase erosion and flow corrosion coupling damage accelerated test unit;

[0031] Figure 22 is the sectional view of the fourth embodiment of the multiphase erosion and flow corrosion coupling damage accelerated test unit;

[0032] Figure 23 is the sectional view of the fifth embodiment of the multiphase erosion and flow corrosion coupling damage accelerated test unit;

[0033] Figure 24 is the sectional view of the sixth embodiment of the multiphase erosion and flow corrosion coupling damage accelerated test unit;

[0034] Figure 25 is a schematic diagram of a test structure of the present application.

[0035] Reference signs: 1 - pipe diameter reducing structure; 2 - flange; 3 - inlet test section; 4 - central cone; 5 - shear force probe; 6 - wall shear force probe; 7 - pipe sample installation groove; 8 - outlet test section; 9 - fixing nut; 10 - pipe diameter expanding structure; 11 - sample fixing groove; 12 - sample piece; 13 - insulation fixing piece; 14 - sample fixing piece; 15 - cone sample installation groove; 16 - bevel sample piece; 17 - bevel insulation fixing piece; 18 - bevel sample fixing groove; 19 - bevel sample fixing piece; 20 - curved surface sample piece; 21 - curved surface insulation fixing piece; 22 - curved surface sample fixing groove; 23 - curved surface sample fixing piece; 24 - central protruding expanding cone; 25 - intermediate test section; 26 - central protruding reducing cone; 27 - central protruding reducing and expanding cone; 28 - central protruding expanding and reducing cone; 29 - circulating pipe; 30 - screw pressurizing pump; 31 - heating and stirring kettle. DETAILED DESCRIPTION

[0036] As shown in Figure 1 , it is a sectional structure diagram of a first embodiment of a multiphase erosion and flow corrosion coupling damage accelerated test unit of the present application, which comprises a circulating main pipe composed of an inlet test section 3 and an outlet test section 8 connected together (in fact, the circulating main pipe can also be extended, as shown in Figure 21 , an intermediate test section 25 is added between the inlet test section 3 and the outlet test section 8), the inlet test section 3 and the outlet test section 8 are connected through a flange 2; the inlet test section 3 is also connected with a pipe diameter reducing structure 1 through the flange 2, and the outlet test section 8 is also connected with a pipe diameter expanding structure 10 through the flange 2;

[0037] A circle of pipe sample installation grooves 7 is arranged on the inner wall of the pipe at the joint of the inlet test section 3 and the outlet test section 8, as shown in Figure 9 , Figure 10 The pipe sample installation groove 7 is a stepped groove with a wide groove bottom and a narrow groove opening, as shown in Figure 6 The sample piece 12 has wings on both sides and is stepped, which can be clamped into the pipe sample installation groove 7 and cannot be separated), and a hard insulation fixing piece 13 (such as polyethylene or polytetrafluoroethylene) is used between adjacent sample pieces 12, as shown in Figure 7As shown, the two sides of the insulation fixing member 13 have flaps and are stepped, capable of being clamped into the pipeline sample installation groove 7 and cannot be separated for insulation; a sample fixing groove 11 is arranged on the axial side of the pipeline sample installation groove 7, for the single sample piece 12 and the single insulation fixing member 13 to enter alternately, the sample fixing groove 11 is also a stepped groove with a wide groove bottom and a narrow groove opening, and the sample fixing member 14 is clamped and fixed therein, one side of the sample fixing member 14 is insulated and abuts against the sample piece 12 through a soft rubber pad, and the other side of the sample fixing member 14 abuts against the flange 2 wall surface between the inlet test section 3 and the outlet test section 8, so that the sample piece 12 in the sample installation groove 7 cannot be separated from the axial direction; through the arrangement of the hard insulation fixing member 13 and the soft rubber pad, the accelerated corrosion of dissimilar steel contact can be prevented, so as to avoid affecting the corrosion damage measurement accuracy.

[0038] A central cone 4 is arranged concentrically and separately in the circulating main pipeline, the central cone 4 has tapered heads at two ends and a body part between the two tapered heads, at least three protrusions are arranged on the outer wall of the body part in the circumferential direction corresponding to the inlet test section 3 and the outlet test section 8 respectively, and the inlet test section 3 and the outlet test section 8 are respectively provided with a fixing nut 9 corresponding to each protrusion, the fixing nut 9 is screwed into the protrusion, and the central cone 4 is fixed inside the inlet test section 3 and the outlet test section 8 in a concentric and separate state.

[0039] According to the test content, different types of probes can be selected to be installed on the inner wall of the inlet test section 3 and / or the outlet test section 8, such as a wall shear force probe 6 (the inner end of which is a shear force probe head 5), a three-electrode corrosion probe, etc., for measuring wall shear force, corrosion current density, corrosion potential, etc. parameters; on the structure of the present application, wall shear force measurement, electrochemical test and weight loss test can be carried out at the same time, the sample piece 12 needs to be cut, polished, polished and weighed before the test, and then uniformly installed in the pipeline sample installation groove 7 (or the cone sample installation groove 15, such as Figure 2 ); during the test, the flow rate, particle concentration, phase, temperature and pressure at each sample piece need to be calibrated, and after stabilization, long-time continuous operation test is carried out, and wall shear force and electrochemical corrosion parameters can be measured online; after the test, the sample piece is removed, soaked in acetone for stain removal, washed with deionized water, dried, and then taken out, weighed and observed for damage morphology.

[0040] In the structure of the present application, the inner diameter and length of the inlet test section 3 are designed according to the test flow rate, the inner diameter is not more than the inner diameter of the circulating main pipeline, the wall thickness is not less than 3 mm, and the length l0 is recommended to be not less than 5 times the inner diameter of the circulating main pipeline; the distance l1 between the inlet side inlet of the inlet test section 3 and the center cone body 4 is not less than 2 times the inner diameter d1 of the inlet test section 3; the distance l2 between the installation position of the wall shear force probe 6 and the maximum diameter position of the inlet cone head of the center cone body 4 is not less than 2d1; 3-6 fixed nuts 9 are installed on the inlet test section 3 in the circumferential direction, the number corresponds to the protrusions of the center cone body 4, the inner diameter of the inlet test section 3 at this position is at least 1 mm larger than d1, which is used to fix the center cone body 4 and prevent sliding and vibration; the sample installation groove 7 of the inlet test section 3 is not less than 2 cm in axial length, and the thickness of the soft rubber pad is not less than 0.5 mm; the sample installation groove 7 and the sample fixing groove 11 are designed as stepped clamping grooves in the circumferential direction, and the clamping groove width l4 is not less than 0.5 mm; the sample piece 12 in the sample installation groove 7 adopts an arc surface, the width of the sample piece 12 in the circumferential direction is not less than 2 cm, the installation number is 4-16 pieces, each sample piece 12 is uniformly distributed, and the sample pieces 12 are isolated by the hard insulating fixing piece 13 made of polyethylene and polytetrafluoroethylene; the width of the sample fixing groove 11 in the circumferential direction is recommended to be the width of a single sample piece 12+insulating fixing piece 13, and the axial length is not less than 1 cm; the sample fixing piece 14 is isolated by a soft rubber pad on the side in contact with the sample; the above-mentioned hard insulating fixing piece 13 and soft rubber pad setting are used to prevent heterogeneous steel contact from accelerating corrosion, so as to avoid affecting the corrosion damage measurement accuracy.

[0041] The size and setting position of the outlet test section 8 are symmetrically arranged with the inlet test section 3, which will not be described here.

[0042] The fluid entering the inlet test section 3 (especially at the pipeline sample installation groove 7) is controlled as much as possible within the laminar flow range, and the Reynolds number is less than 2300; the test flow rate can reach 80 m / s at most, the particle volume fraction can reach 20% at most, and the gas volume fraction can reach 20% at most; the distance l5 from the inlet cone head of the center cone body 4 to the outlet of the inlet test section 3 is not less than 3 times the inner diameter of the inlet test section 3.

[0043] Looking at Figure 11 , Figure 12 , which is the second embodiment of the present application, compared with the first embodiment, the main difference is that the shape of the center cone body 4 has changed, the inlet side of the body of the center cone body 4 is thinner and the outlet side is thicker, so that a sudden expansion surface is formed at the joint position;

[0044] Among them, as Figures 13-16As shown, a conical sample mounting groove 15 with a flat bottom is formed circumferentially on the protruding surface. The conical sample mounting groove 15 is a stepped groove with a wide bottom and a narrow opening. Several inclined sample pieces 16 are embedded and fixed in each conical sample mounting groove 15. Adjacent inclined sample pieces 16 are isolated from each other by inclined insulating fasteners 17. On one axial side of the conical sample mounting groove 15, there is an inclined sample fixing groove 18 for individual inclined sample pieces 16 and individual inclined insulating fasteners 17 to enter and exit alternately. The inclined sample fixing groove 18 is also a stepped groove with a wide bottom and a narrow opening. An inclined sample fastener 19 is embedded and fixed in it. One side of the inclined sample fastener 19 is isolated and abutted against the inclined sample piece 16 by a soft rubber pad, and then fixed in the inclined sample fixing groove 18 by screws so that the inclined sample piece 16 in the conical sample mounting groove 15 cannot be detached from the axial direction.

[0045] like Figures 17-20 As shown, a conical sample mounting groove 15 with a curved bottom surface is formed circumferentially on the protruding surface. The conical sample mounting groove 15 is a stepped groove with a wide bottom and a narrow opening. Several curved sample pieces 20 are embedded and fixed in each conical sample mounting groove 15. Adjacent curved sample pieces 20 are isolated from each other by curved insulating fasteners 21. On one axial side of the conical sample mounting groove 15, there is a curved sample fixing groove 22 for individual curved sample pieces 20 and individual curved insulating fasteners 21 to enter and exit alternately. The curved sample fixing groove 22 is also a stepped groove with a wide bottom and a narrow opening. A curved sample fastener 23 is embedded and fixed in it. The curved sample fastener 23 is embedded and fixed in the curved sample fixing groove 22 and fixed with screws. The side of the curved sample fastener 23 that contacts the curved sample piece 20 is isolated by a soft rubber pad, so that the curved sample piece 20 in the conical sample mounting groove 15 cannot be detached from the axial direction.

[0046] In the structure of this invention, each inclined sample piece 16 (or curved sample piece 20) has a circumferential width of not less than 2 cm and an axial length of not less than 2 cm. The number of pieces installed is 4 to 12. Different sample pieces need to be evenly distributed in the slot. Adjacent inclined sample pieces 16 (or curved sample pieces 20) are isolated by a rigid inclined insulating fastener 17 (or curved insulating fastener 21) made of polyethylene or polytetrafluoroethylene. The width of the inclined sample fixing groove 18 (or curved sample fixing groove 22) is recommended to be the width of a single sample piece plus the width of the insulating fastener. The contact side between the inclined sample fastener 19 (or curved sample fastener 23) and the inclined sample piece 16 (or curved sample piece 20) is isolated by a soft rubber pad. The above-mentioned rigid insulating fastener and soft rubber pad are used to prevent the contact between dissimilar steels from accelerating corrosion and to avoid affecting the measurement accuracy of corrosion damage.

[0047] In the structure of the application, the center cone 4 can also be designed and selected according to the common multiphase scouring, flow corrosion and cavitation service conditions of pressure-bearing equipment in the fields of on-site petrochemical industry, coal chemical industry, etc., and can be designed as a center sudden expansion cone 24 (such as Figure 12 ), a center sudden contraction cone 26 (such as Figure 22 ), a center sudden contraction and expansion cone 27 (such as Figure 23 ), a center sudden expansion and contraction cone 28 (such as Figure 24 ), etc.; and the sample pieces can be arranged on the sudden expansion surfaces and / or sudden contraction surfaces.

[0048] Among them, the middle inclined surface / curved surface of the center sudden expansion cone 24 and the center sudden contraction cone 26 has an angle α Figure 12 ) with the main flow direction in the range of 0-90°, which can be used to test the single or coupled damage law of liquid-solid scouring and flow corrosion under different impact angles; the center sudden contraction and expansion cone 27 can be used to test the single or coupled damage law of multiphase scouring and flow corrosion in the sudden opening process of the valve core; and the center sudden expansion and contraction cone 28 can be used to test the single or coupled damage law of multiphase scouring, flow corrosion and cavitation in the sudden closing of the valve core or the local sharp contraction of the pipeline cross section.

[0049] As shown in Figure 21 , the application can also be installed with an intermediate test section 25 between the inlet test section 3 and the outlet test section 8, and the intermediate test section 25 is connected with the adjacent test sections through flanges at both ends, and the circumferential direction of the connection position can be installed with different sample pieces; the distance between the inlet connection position of the intermediate test section 25 and the maximum diameter position of the inlet tapered head of the center cone 4 is not less than 2d1; and the distance between the outlet connection position of the intermediate test section 25 and the sudden expansion surface of the center cone 4 is also not less than 2×(d1-d2). In addition, the number of the intermediate test section 25 can be increased according to the needs, and if the number exceeds 2, a protrusion is recommended to be added to the middle part of the center cone 4 to prevent vibration.

[0050] As shown in Figure 25 , the structure of the application is installed in the stable straight pipe area of the circulating test pipeline, and the length l6 of the inlet side stable straight pipe of the inlet test section 3 is not less than five times the inner diameter of the inlet side stable straight pipe. The circulating test pipeline mainly consists of a circulating pipeline 29, a screw pressurizing pump 30, a heating and stirring kettle 31 and an auxiliary control system, wherein the flow velocity in the circulating pipeline 29 is recommended to be in the range of 0.5-2 m / s, the higher the particle concentration, the greater the recommended flow velocity, and the material can be selected from 304L, 316L, Hastelloy alloy and 825 alloy; the auxiliary control system needs to use PID precise control of flow, pressure and temperature; and the heating and stirring kettle 31 automatically adjusts and controls the liquid temperature, particle concentration and corrosion medium concentration of the circulating pipeline.

[0051] In the measuring method of the application, the test method of the structure of the application adopts two kinds of electrochemical test and weight loss test. The electrochemical test mainly tests the corrosion process current density and the corrosion potential to qualitatively judge the corrosion condition. The weight loss test mainly causes local damage through fluid corrosion, erosion and cavitation, calculates the damage weight loss rate, and measures the length, width and depth of the damage morphology through a microscope to guide the damage degree evaluation. For flow corrosion, the damage rate test is carried out by controlling the concentration, temperature and flow of the corrosion medium. For pure liquid phase / liquid-solid erosion, the damage rate test is carried out by controlling the particle concentration, temperature and flow. For cavitation, the damage rate test is carried out by controlling the flow and pressure. For coupled damage, the above single damage rate test method is used for regulation.

Claims

1. A multiphase erosion and flow corrosion coupled damage accelerated test unit, characterized by, The circulating main pipeline and the center cone arranged concentrically and separately in the circulating main pipeline; The center cone has two tapered heads at two ends and a body between the two tapered heads; A circle of sample mounting grooves is arranged circumferentially on the inner side wall of the circulating main pipeline or the outer wall of the center cone, the sample mounting grooves are stepped grooves with wide groove bottoms and narrow groove openings, a plurality of sample pieces arranged circumferentially are clamped and fixed in the sample mounting grooves, and adjacent sample pieces are insulated by insulation fixing pieces; wherein the fluid entering the sample mounting groove is controlled in the range of laminar flow, and the Reynolds number is less than 2300; A probe is installed on the inner wall of the circulating main pipeline opposite to the body of the center cone; A sample fixing groove is arranged on the axial side of the sample mounting groove for the entry and exit of a single sample piece and a single insulation fixing piece alternately, the sample fixing groove is fixed with the sample fixing piece, and the side of the sample fixing piece in contact with the sample piece is insulated by a rubber pad, so that the sample piece in the sample mounting groove cannot be separated from the axial direction.

2. The multi-phase erosion and flow corrosion coupling damage accelerated test unit of claim 1, wherein, The circulating main pipeline is composed of an inlet test section and an outlet test section, or is composed of an inlet test section, an outlet test section and at least one intermediate test section connected between the inlet test section and the outlet test section.

3. The multi-phase erosion and flow corrosion coupling damage accelerated test unit of claim 2, wherein, The inlet end of the inlet test section is connected with a pipeline diameter reduction structure, and the outlet end of the outlet test section is connected with a pipeline diameter expansion structure.

4. The multi-phase erosion and flow corrosion coupling damage accelerated test unit of claim 2, wherein, At least three protrusions are arranged circumferentially on the outer side wall of the body of the center cone corresponding to the inlet test section and the outlet test section respectively, and the inlet test section and the outlet test section are respectively provided with fixing nuts corresponding to the protrusions, the fixing nuts are screwed into the protrusions, and the center cone is fixed in the inlet test section and the outlet test section in a concentric and separate state.

5. The multi-phase erosion and flow corrosion coupling damage accelerated test unit of claim 1, wherein, The probe is a wall shear force probe and / or a three-electrode corrosion probe.

6. The multi-phase erosion and flow corrosion coupling damage accelerated test unit of claim 1, wherein, The center cone is a center protrusion expansion cone, a center protrusion contraction cone, a center protrusion expansion and contraction cone, or a center protrusion contraction and expansion cone; the sample mounting grooves are arranged on the protrusion expansion surface and / or the protrusion contraction surface.

7. The multi-phase erosion and flow-erosion coupling damage accelerated test unit of claim 6, wherein, The bottom surface of the sample mounting groove arranged on the protrusion expansion surface and / or the protrusion contraction surface is planar or curved.

8. A multiphase erosion and flow corrosion coupled damage accelerated test structure, characterized in that, The circulating pipeline connecting the pressurizing pump and the stirring pump, a multiphase erosion and flow corrosion coupling damage accelerated test unit as claimed in any one of claims 1-7 is connected in the stable straight pipe region of the circulating pipeline.

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