A cyclic experimental system for fatigue and leakage testing of flexible connection components

Abstract

This invention provides a cyclic experimental loop system for fatigue and leakage testing of flexible connection components, including a main experimental loop, a pressurized bypass, a control system, and a data acquisition system. The control system includes a first shut-off valve, a second shut-off valve, a third shut-off valve, a fourth shut-off valve, a fifth shut-off valve, and a sixth shut-off valve. The main experimental loop includes a molten salt tank, a regulating valve, a flow meter, a second heater, a test section, and a cooling system, all connected in sequence to form the loop. The experimental loop provided by this invention can perform accelerated fatigue testing on flexible connection components currently available domestically and internationally, and the experimental loop is safe and reliable. Furthermore, in addition to conducting dynamic molten salt fatigue and leakage testing of flexible connections, the experimental loop can also be used to study the fatigue and leakage characteristics of flexible connection components in static molten salt conditions.

Description

Technical Field

[0001] This invention relates to the field of fatigue testing of flexible connection components, and in particular to an experimental research system for the fatigue and leakage characteristics of flexible connection components in a parabolic trough solar thermal power generation system using high-temperature molten salt as the working fluid in the heat collection tube. More particularly, it relates to a cyclic experimental loop system for testing the fatigue and leakage of flexible connection components. Background Technology

[0002] Currently, to continuously improve the operating efficiency of generator units in parabolic trough solar thermal power plants, the heat transfer medium within the collector tubes is being developed towards higher temperatures and higher pressures. Flexible connection components used in solar thermal power systems employing heat transfer oil as the heat transfer medium have reached a relatively mature stage both domestically and internationally. However, because molten salt has a higher operating temperature than heat transfer oil, a set of flexible connection components suitable for heat transfer oil is no longer applicable. Domestic and international manufacturers have been continuously researching flexible connection components suitable for high-temperature molten salt, but a suitable experimental testing platform is lacking for accelerated fatigue testing of these components. Therefore, researching and developing a cyclic loop experimental system for fatigue and leakage testing of flexible connection components for high-temperature molten salt is of great significance for the subsequent development of parabolic trough solar thermal power generation technology and the stable operation of parabolic trough solar thermal power generation systems. Summary of the Invention

[0003] The technical problem to be solved by the present invention is: in order to overcome the shortcomings of the prior art, the present invention provides a cyclic experimental system for fatigue and leakage testing of flexible connection components, so as to solve the problem that the existing flexible connection components applied to high temperature molten salt lack sufficient testing conditions and cause molten salt leakage in subsequent solar thermal power plants, as well as the problem that there is currently no relevant testing experimental platform at home and abroad.

[0004] The technical solution adopted by this invention to solve its technical problem is: a cyclic experimental circuit system for fatigue and leakage testing of flexible connection components, including a main experimental circuit, a pressurized bypass, a control system, and a data acquisition system; the control system includes a first shut-off valve, a second shut-off valve, a third shut-off valve, a fourth shut-off valve, a fifth shut-off valve, and a sixth shut-off valve; the main experimental circuit includes a molten salt tank, a regulating valve, a flow meter, a second heater, a test section, and a cooling system, which are connected in sequence to form a circuit; the first heater is arranged inside the molten salt tank. A third heater is arranged outside the test section pipeline. The working fluid in the main experimental circuit is molten solar salt. The test section has a flexible component and a moving component that drives the flexible component. The pressurization bypass includes a nitrogen cylinder and a pressure reducing valve connected in sequence. The outlet pipeline of the pressure reducing valve is split into two: one connected to the molten salt tank pipeline, and the other connected to a fifth shut-off valve. The pressurization bypass also includes a vacuum pump. The inlet of the vacuum pump is connected to the molten salt tank pipeline after passing through a sixth shut-off valve. The first shut-off valve is located on the pipeline between the test section and the second heater. The second shut-off valve is located on the pipeline between the test section and the cooler. The third shut-off valve is located on the main experimental circuit. One end of the third shut-off valve is connected to the pipeline between the flow meter and the second heater, and the other end is connected to the pipeline between the cooling system and the molten salt tank. The pipeline formed by the second heater, the test section, and the third pressure sensor is connected to the third... The pipeline containing the shut-off valve is connected in parallel; the fourth shut-off valve is installed on the pipeline between the outlet of the pressure reducing valve and the molten salt tank; the outlet pipeline of the fifth shut-off valve is split into two to form two air-sealed pipelines connected in parallel with the test section, and the outlets of the two air-sealed pipelines converge and are connected to a drain valve; the data acquisition system includes temperature sensors and pressure sensors; the pipeline between the first shut-off valve and the test section is equipped with a first temperature sensor and a first pressure sensor; the pipeline between the test section and the second shut-off valve is equipped with a second temperature sensor and a second pressure sensor; the pipeline between the cooling system and the molten salt tank is equipped with a third temperature sensor and a third pressure sensor; the inlet pipeline of the regulating valve, the pipeline between the regulating valve and the flow meter, and the outlet pipeline of the flow meter are all equipped with a fourth temperature sensor and a fourth pressure sensor, respectively; the pipeline between the molten salt tank and the pressure reducing valve is equipped with a fifth pressure sensor, and the outlet pipeline of the fifth shut-off valve is equipped with a sixth pressure sensor.

[0005] Furthermore, to facilitate the reflux of the working fluid in the main experimental loop, the molten salt tank is installed at the lowest position in the main experimental loop, the pipes at both ends of the flow meter are arranged horizontally, and all other pipes in the main experimental loop except for the pipes at both ends of the flow meter are inclined towards the molten salt tank.

[0006] Preferably, the motion component includes a rotating shaft, a hydraulic cylinder for rotating the flexible component, and a hydraulic push rod for translating the flexible component. The hydraulic cylinder and the hydraulic push rod are respectively connected to the flexible component via the rotating shaft. The flexible component includes a test pipeline with flexible hoses connected to both ends. The ends of the flexible hoses away from the test pipeline are connected to the main experimental circuit via a rotary joint. Sensors are installed at both ends of the test pipeline near the flexible hoses. The rotary joint is also connected to a rotating shaft for rotating the corresponding flexible hoses. A torque sensor is installed on the rotating shaft.

[0007] Preferably, the main experimental circuit containing the first and second shut-off valves is a downward-opening "∩"-shaped bend. The first and second shut-off valves are located at the top of the opening of the "∩"-shaped bend, and the connection between the gas-sealing pipeline and the corresponding "∩" pipeline is located on the side of the shut-off valve closer to the test section. The "∩"-shaped bend is designed at the section positions of the first and second shut-off valves. At this location, the bend's shape facilitates the interception of molten salt, achieving the purpose of salt injection. Simultaneously, it facilitates gas interception during static molten salt testing, forming an effective gas-sealing structure at both ends of the test section.

[0008] Preferably, the bottom of the molten salt tank is equipped with a molten salt pump for pumping molten salt into the main experimental circuit. The molten salt pump is a molten salt submersible pump with a centrifugal impeller. A level gauge, a pressure gauge, and an insertion thermocouple are respectively installed above the molten salt tank.

[0009] The above-described cyclic experimental system for fatigue and leakage testing of flexible connection components can be used for fatigue testing of flexible connections in dynamic molten salt, and includes the following steps:

[0010] S1: Open the sixth shut-off valve, turn on the vacuum pump to remove excess air from the molten salt tank, and simultaneously open the fourth and fifth shut-off valves. Open the pressure reducing valve to replace the air with nitrogen from the nitrogen cylinder and use it as the pressurizing medium for the main experimental circuit. Then close the vacuum pump and the sixth shut-off valve, and only pressurize the inside of the main experimental circuit. When the readings of each pressure sensor in the main experimental circuit reach the test pressure reading, close the fifth shut-off valve.

[0011] S2: Close the third shut-off valve, open the first shut-off valve and the second shut-off valve, adjust the rotating test section so that the test section is at the lowest position in the rotation direction, turn on the first heater to heat and melt the molten salt, turn on the molten salt pump, adjust the opening of the regulating valve so that the flow rate of the main experimental circuit reaches the actual working condition flow rate, and turn on the second heater to reheat the molten salt to reach the set test temperature.

[0012] S3: After the temperature and pressure in the experimental circuit have stabilized, activate the motion component of the test section to perform fatigue testing on the flexible connection component, and record the number of tests by the terminal.

[0013] S4: During the test experiment, observe the readings of the first pressure sensor and the second pressure sensor, calculate and record the pressure difference between them;

[0014] S5: After the test, shut off the molten salt pump, the first heater, the second heater, the pressure reducing valve and the fourth shut-off valve, and adjust the test section to the highest position during its rotation. After the molten salt has completely refluxed and dropped to a safe temperature, and the internal pressure of the experimental circuit has dropped to standard atmospheric pressure, disassemble the flexible connection component of the test section, collect the molten salt leakage particles, and analyze the leakage and fatigue characteristics by combining the numerical changes of the first pressure sensor, the second pressure sensor, the force sensor and the torque sensor.

[0015] S6: If a large amount of molten salt leaks out uncontrollably during the experiment, immediately open the third shut-off valve to disconnect the test section, and then shut off the molten salt pump, the first heater, the second heater, the pressure reducing valve, and the fourth shut-off valve in sequence.

[0016] The above-described cyclic experimental system for fatigue and leakage testing of flexible connection components can also be used for fatigue testing of flexible connections in static molten salt, including the following steps:

[0017] S1: Keep the first and second shut-off valves open and the third shut-off valve closed in the main experimental circuit. Adjust the rotating test section so that the test section is at the lowest position in the rotation direction.

[0018] S2: Turn on the first heater, heat the molten salt to a certain temperature, and then turn on the molten salt pump;

[0019] S3: After the test circuit is filled with molten salt, turn off the molten salt pump, then turn on the third heater and close the first and second shut-off valves;

[0020] S4: Open the pressure reducing valve and the fifth shut-off valve to pressurize both ends of the test section, so that the working medium is sealed in the test section by gas. After reaching the specified pressure, close the pressure reducing valve and the fifth shut-off valve.

[0021] S6: Perform fatigue testing on the flexible connection components, and record the number of tests by the terminal.

[0022] S7: After the test is completed, turn off the third heater, adjust the rotating test section so that the test section is at the highest position in the rotation direction, and after the molten salt has finished flowing back, open the drain valve to remove the remaining molten salt inside the test section. After the temperature of the test section drops to a safe temperature, disassemble the flexible connection component of the test section, collect the molten salt leakage particles, and analyze the leakage and fatigue characteristics by combining the numerical changes of the first pressure sensor, the second pressure sensor, the force sensor and the torque sensor.

[0023] The beneficial effects of this invention are that it provides a cyclic experimental circuit system for fatigue and leakage testing of flexible connection components. Using molten binary solar salt as the working medium, it studies the fatigue and leakage characteristics of flexible connection components composed of rotary joints and flexible hoses. This allows the experimental circuit of this invention to perform accelerated fatigue testing on flexible connection components currently used both domestically and internationally. Compared to traditional heat transfer oil, molten binary solar salt has a higher operating temperature. Furthermore, the secondary heating design using a first and second heater effectively avoids potential damage to the flow meter caused by high temperatures, making the experimental circuit safe and reliable. In addition, the cyclic experimental circuit for fatigue and leakage testing of flexible connections of this invention also includes a data acquisition and control system, enabling remote data acquisition and control, which greatly improves the safety of the experimental platform. Besides conducting fatigue and leakage tests on flexible connections using dynamic molten salt, this cyclic experimental circuit for fatigue and leakage testing of flexible connections can also be used to study the fatigue and leakage characteristics of flexible connection components using static molten salt. Attached Figure Description

[0024] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0025] Figure 1 This is a schematic diagram of the experimental circuit in this invention.

[0026] Figure 2 This is a partial structural diagram of the test section in the experimental circuit of this invention.

[0027] In the diagram: 1. Molten salt tank; 2. Molten salt pump; 3. Regulating valve; 4. Flow meter; 5. Test section; 6. Cooling system; 7. Safety valve; 8. Level gauge; 9. Pressure gauge; 10. Insertion thermocouple; 11. First heater; 12. Second heater; 13. Third heater; 14. First shut-off valve; 15. Second shut-off valve; 16. Third shut-off valve; 17. First pressure sensor; 18. First temperature sensor; 19. Second pressure sensor; 20. Second temperature sensor; 21. Third pressure sensor; 22. Third temperature sensor; 23. Fourth pressure sensor; 24. Fourth temperature sensor; 25. Nitrogen cylinder; 26. Fifth pressure sensor; 27. Pressure reducing valve; 28. Fourth shut-off valve; 29. ​​Fifth shut-off valve; 30. Sixth pressure sensor; 31. Vacuum pump; 32. Sixth shut-off valve; 33. Drain valve; 501. Rotary joint; 502. Flexible hose; 503. Force sensor; 504. Torque sensor; 505. Rotating shaft; 506. "∩" shaped bend. Detailed Implementation

[0028] The invention will be described in further detail with reference to the accompanying drawings. These drawings are simplified schematic diagrams, illustrating only the basic structure of the invention in a schematic manner. Therefore, they only show the components relevant to the invention, and the orientations and references (e.g., up, down, left, right, etc.) are only used to aid in the description of the features in the drawings. Therefore, the following specific embodiments are not intended to be limiting, and the scope of the claimed subject matter is defined solely by the appended claims and their equivalents.

[0029] like Figure 1 The present invention discloses a cyclic experimental system for fatigue and leakage testing of flexible connection components. The internal working fluid is molten binary solar salt with a melting point of 240℃ and an upper limit temperature of 600℃, which meets the requirements of this test experiment.

[0030] like Figure 1 This invention presents a cyclic experimental loop system for fatigue and leakage testing of flexible connection components. The internal working fluid is molten binary solar salt with a melting point of 240℃ and an upper temperature limit of 600℃, meeting the requirements of this test experiment. Based on flexible connection components applied to high-temperature molten salt, this invention provides a cyclic experimental loop system for fatigue and leakage testing of flexible connection components. In the design process of this experimental loop, the realization of the motion unit of the test section was considered. Finite element analysis was performed on each experimental component using numerical simulation software to ensure the mechanical stability of each component. Simultaneously, thermal analysis was performed on the experimental loop pipeline to ensure the safety and stability of the entire loop.

[0031] The fatigue and leakage test loop of the flexible connection component includes a main test loop with molten salt as the heat transfer medium and a pressurized bypass with nitrogen as the pressurizing medium. The main test loop and the pressurized bypass are connected to an external data acquisition and control system. Since the data acquisition and control system is a common technology in conventional test platforms, it will not be described in detail here.

[0032] The main experimental circuit includes a molten salt tank 1, a first heater 11, a molten salt pump 2, a regulating valve 3, a flow meter 4, a second heater 12, a test section 5, and a cooling system 6, which are connected sequentially in the direction of molten salt flow.

[0033] In this main experimental circuit, the molten salt tank 1 is positioned at the lowest point. Except for the horizontally arranged pipes at both ends of the flow meter 4, all other pipes are inclined at a certain angle towards the molten salt tank 1 to facilitate the backflow of molten salt after the test. A safety valve 7 is installed at the top of the molten salt tank 1 to prevent danger caused by excessive internal pressure. The molten salt tank 1 is equipped with a level gauge 8, a pressure gauge 9, and an insertion thermocouple 10 to monitor the internal state of the molten salt tank 1.

[0034] The molten salt tank 1 is equipped with a first heater 11 located at the bottom. This heater arrangement maximizes the uniform temperature distribution of the molten salt inside the tank when it is activated. A flange-type electric heater is used for cost-effectiveness and uniform heating. A second heater 12 is positioned between the flow meter 4 and the test section 5 to reheat the molten salt flowing through the flow meter 4. Since the current flow meter 4 has a maximum operating temperature of only 450℃, and the mainstream molten salt is generally solar salt (60% NaNO3 + 40% KNO3) with an operating temperature of 260℃~600℃, while the upper limit of the molten salt operating temperature of this test bench is 540℃, a second heater 12 is used to prevent damage to the instruments inside the molten salt tank 1 and the flow meter 4 due to excessively high molten salt temperatures. In the main experimental loop, the cooling system 6 is located between the molten salt inlet of molten salt tank 1 and the molten salt outlet of test section 5. Its purpose is to cool the heating medium output from test section 5 before it flows back into molten salt tank 1. In the experimental loop, the first heater 11 initially heats the medium in the molten salt tank, and then the second heater 12 performs secondary heating to ensure the molten salt enters the test section at an appropriate temperature. Based on this, a third heater 13 is installed outside test section 5 to compensate for heat loss in test section 5 and for temperature compensation during static molten salt testing. The cooling system 6 is located between the outlet of test section 5 and the inlet of molten salt tank 2 to cool the high-temperature molten salt. Since the maximum temperature resistance of the molten salt pump 2 and level gauge 8 located in molten salt tank 1 is approximately 450℃, this system prevents damage to internal components of molten salt tank 1 due to excessively high molten salt temperature exiting test section 5, and also prevents uncontrollable molten salt temperature in subsequent cycles, which could lead to damage to the flow meter in the main loop and other related problems.

[0035] The pressurized bypass includes a nitrogen cylinder 25 and a pressure reducing valve 27 connected in sequence. The outlet pipe of the pressure reducing valve 27 is split into two: one is connected to the molten salt tank 1, and the other is connected to the fifth shut-off valve 29. The outlet pipe of the fifth shut-off valve is split into two to form two gas-sealed pipes connected in parallel with the test section, and the outlets of the two gas-sealed pipes converge and are connected to a drain valve.

[0036] The pressurized bypass also includes a vacuum pump 31, whose inlet is connected to the molten salt tank pipeline via a sixth shut-off valve 32. The vacuum pump 31 is used to extract gas from the molten salt tank and, in conjunction with a nitrogen cylinder 25 and a pressure reducing valve 27, converts the gas in the main experimental circuit to nitrogen. This gas replacement design is to prevent residual air in the molten salt tank 1 from oxidizing the working medium, thus avoiding instability and affecting the overall experimental accuracy. Extracting and replacing the air with nitrogen, an inert gas, is less likely to oxidize the working medium inside the tank, which is beneficial for the stability of the working medium's properties. Simultaneously, the pressurized bypass, combined with the specific structural design of the gas-sealed pipeline and the test section 5, can provide a gas seal at both ends of the test section 5 during static testing, further improving experimental accuracy.

[0037] The partial structural diagram of test section 5 in the main experimental circuit is shown below. Figure 2 As shown, test section 5 is used to simulate the translational motion caused by the thermal expansion of the collector tubes and the rotational motion caused by the solar tracker in a parabolic trough solar thermal power generation system. It is a key component of the entire test circuit. Specifically, test section 5 includes a motion component and a flexible component. The motion component includes a rotating shaft 505, a hydraulic cylinder that drives the flexible component to rotate, and a hydraulic push rod that drives the flexible component to translate. The hydraulic cylinder and the hydraulic push rod are respectively connected to the flexible component via the rotating shaft. A torque sensor 504 is installed on the rotating shaft 505. The flexible component is symmetrically arranged, with each side including a rotary joint 501, a flexible hose 502, and a force sensor 503. The rotary joint 501 and the flexible hose 502 are connected by a metal elbow. The upper end of the flexible hose 502 is the test pipeline, which is connected to the flexible connection component on the other side to form the complete test section 5. In this experimental circuit, a straight pipe can preferably be used for the test pipeline. The straight pipe, together with the flexible components on both sides, forms an approximately "U"-shaped pipeline. The third heater 13 is wrapped around the outside of this pipeline to compensate for heat loss in test section 5 and for temperature compensation during static molten salt testing. Force sensor 503 is used to monitor the force on flexible hose 502, and torque sensor 504 is used to monitor the rotational torque of rotary joint 501. During the experiment, the failure of the flexible connection component can be determined by the changes in the values ​​output by force sensor 503 and torque sensor 504. The first pressure sensor 16 and the second pressure sensor 18 at both ends of test section 5 can monitor the pressure changes at the inlet and outlet of test section 5. During the experiment, the pressure difference between the two sensors can be used to determine whether the flexible connection component is leaking.

[0038] Test section 5 is connected to the main experimental circuit at both ends by "∩"-shaped bends 506. During static molten salt testing, the downward-facing "∩"-shaped bends facilitate the interception of molten salt, achieving the purpose of salt injection. Simultaneously, two gas-sealed pipelines connected from the fifth shut-off valve 29 are used. Since these two gas-sealed pipelines are connected in parallel with the test section, during static testing, nitrogen gas can enter the gas-sealed pipelines in parallel with the test section through the nitrogen cylinder 25, pressure reducing valve 27, and the fifth shut-off valve 29, forming a gas-sealed structure at both ends of the test section. This increases airtightness and prevents valve leakage from affecting experimental observations.

[0039] In this main experimental circuit, regulating valve 3, first shut-off valve 13, second shut-off valve 14, third shut-off valve 15, and drain valve 33 are all electrically operated valves. Automation of the experimental circuit ensures the safety of personnel during operation and testing. In this pressurized bypass, fourth shut-off valve 27, fifth shut-off valve 28, and sixth shut-off valve 31 are all manually operated valves.

[0040] In the main experimental circuit, the first pressure sensor 16, the first temperature sensor 17, the second pressure sensor 18, the second temperature sensor 19, the third pressure sensor 20, the third temperature sensor 21, the fourth pressure sensor 22, the fourth temperature sensor 23, the fifth pressure sensor 25, and the sixth pressure sensor 29 are used to monitor the status of the main experimental circuit and the pressurized bypass, ensuring the stable operation of the experimental circuit.

[0041] Meanwhile, in order to maintain the working fluid temperature, in this experimental circuit, except for the flexible hose 502, all other pipes in the main experimental circuit are wrapped with aerogel felt as insulation material, and aluminum sheets are covered on the outside of the insulation material to reduce the heat loss of the system and maximize the heating efficiency.

[0042] Using the above experimental circuit, a fatigue test of a flexible connection in dynamic molten salt can be designed, including the following steps:

[0043] S1: Open the sixth shut-off valve 32, turn on the vacuum pump 31 to remove excess air from the molten salt tank 1, and simultaneously open the fourth shut-off valve 28 and the fifth shut-off valve 29, and open the pressure reducing valve 27. After a period of time, turn off the vacuum pump 31 and the sixth shut-off valve 32, and only pressurize the main experimental circuit. When the pressure sensor reading in the main experimental circuit reaches the test pressure value of 6MPa, close the fifth shut-off valve 29.

[0044] S2: Close the third shut-off valve 16, open the first shut-off valve 14 and the second shut-off valve 15, adjust the rotating test section 5 so that the test pipeline is at its lowest position in the rotation direction, turn on the first heater 11 to melt the molten salt and heat it to a certain temperature, turn on the molten salt pump 2, adjust the opening of the regulating valve 3 so that the flow rate of the main experimental circuit reaches the actual working condition flow rate, and turn on the second heater 12 to reheat the molten salt to reach the set test temperature of 600℃.

[0045] S3: After the temperature and pressure in the experimental circuit have stabilized, activate the motion component of test section 5 to perform fatigue testing on the flexible connection component, and record the number of tests by the terminal.

[0046] S4: During the test experiment, focus on observing the readings of the first pressure sensor 17 and the second pressure sensor 19, and calculate and record the pressure difference between them.

[0047] S5: After the test, shut off the molten salt pump 2, the first heater 11, the second heater 12, the pressure reducing valve 27, and the fourth shut-off valve 28. Adjust the rotating test section 5 so that the test pipeline is at its highest position in the rotation direction. After the molten salt has completely refluxed and dropped to a safe temperature, and the internal pressure of the experimental circuit has dropped to standard atmospheric pressure, disassemble the flexible connection component of the test section 5, collect the molten salt leakage particles, and analyze the leakage and fatigue characteristics by combining the numerical changes of the first pressure sensor 17, the second pressure sensor 19, the force sensor 503, and the torque sensor 504.

[0048] S6: If a large amount of molten salt leaks out uncontrollably during the experiment, immediately open the third shut-off valve 16 to disconnect part of the test section 5 to avoid greater harm and loss. Then, shut off the molten salt pump 2, the first heater 11, the second heater 12, the pressure reducing valve 27, and the fourth shut-off valve 28 in sequence.

[0049] Furthermore, using the above experimental circuit, a fatigue test of a flexible connection in static molten salt can be designed, including the following steps:

[0050] S1: Keep the first shut-off valve 14 and the second shut-off valve 15 open in the main experimental circuit, and the third shut-off valve 16 closed. Adjust the rotating test section 5 so that the test pipeline is at the lowest position in the rotation direction.

[0051] S2: Turn on the first heater 11, heat the molten salt to a certain temperature, and then turn on the molten salt pump 2.

[0052] S3: After the test circuit is filled with molten salt, turn off the molten salt pump, then turn on the third heater 13, and close the first shut-off valve 14 and the second shut-off valve 15.

[0053] S4: Open pressure reducing valve 27 and fifth shut-off valve 29 to pressurize the closed test section. After reaching the specified pressure, close pressure reducing valve 27 and fifth shut-off valve 29.

[0054] S6: Activate the motion component of test segment 5 to perform fatigue testing on the flexible connection component, and record the number of tests by the terminal.

[0055] S7: After the test is completed, turn off the third heater 13 and adjust the position of the straight pipe on the test section 5 to the highest position. After the molten salt has finished refluxing, open the drain valve 33 to remove the remaining molten salt inside the test section 5. After the temperature of the test section drops to a safe temperature, disassemble the flexible connection assembly of the test section 5, collect the molten salt leakage particles, and analyze the leakage and fatigue characteristics by combining the numerical changes of the first pressure sensor 17, the second pressure sensor 19, the force sensor 503, and the torque sensor 504.

[0056] Based on the above-described preferred embodiments of the present invention, and through the foregoing description, those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. A cyclic experimental system for fatigue and leakage testing of flexible connection components, characterized in that: This includes the main experimental circuit, pressurized bypass, control system, and data acquisition system. The control system includes a first shut-off valve (14), a second shut-off valve (15), a third shut-off valve (16), a fourth shut-off valve (28), a fifth shut-off valve (29), and a sixth shut-off valve (32). The main experimental circuit includes a molten salt tank (1), a regulating valve (3), a flow meter (4), a second heater (12), a test section (5), and a cooling system (6) connected in sequence to form a circuit. The molten salt tank (1) is equipped with a first heater (11), and the test section (5) is equipped with a third heater (13) outside the pipeline. The working fluid in the main experimental circuit is molten binary solar salt. The test section (5) has a flexible component and a motion component that drives the flexible component to move. The pressurized bypass includes a nitrogen cylinder (25) and a pressure reducing valve (27) connected in sequence by pipelines. The outlet pipeline of the pressure reducing valve (27) is split into two, one of which is connected to the pipeline of the molten salt tank (1), and the other is connected to the fifth shut-off valve (29). The pressurized bypass also includes a vacuum pump (31), the inlet of which is connected to the pipeline of the molten salt tank (1) through the sixth shut-off valve (32). The first shut-off valve (14) is installed on the pipeline between the test section (5) and the second heater (12); The second shut-off valve (15) is located on the pipeline between the test section (5) and the cooler; The third shut-off valve (16) is installed on the main experimental circuit. One end of the third shut-off valve (16) is connected to the pipeline between the flow meter (4) and the second heater (12), and the other end is connected to the pipeline between the cooling system (6) and the molten salt tank (1). The pipeline formed by the second heater (12), the test section (5) and the third pressure sensor (21) is connected in parallel with the pipeline where the third shut-off valve (16) is located. The fourth shut-off valve (28) is installed on the pipeline between the outlet of the pressure reducing valve (27) and the molten salt tank (1); The outlet pipeline of the fifth shut-off valve (29) is split into two to form two air-sealed pipelines connected in parallel with the test section (5), and the outlets of the two air-sealed pipelines converge and are connected to a drain valve (33). The data acquisition system includes a temperature sensor and a pressure sensor; a first temperature sensor (18) and a first pressure sensor (17) are provided on the pipeline between the first shut-off valve (14) and the test section (5); a second temperature sensor (20) and a second pressure sensor (19) are provided on the pipeline between the test section (5) and the second shut-off valve (15); a third temperature sensor (22) and a third pressure sensor (21) are provided on the pipeline between the cooling system (6) and the molten salt tank (1); a fourth temperature sensor (24) and a fourth pressure sensor (23) are provided on the inlet pipeline of the regulating valve (3), the pipeline between the regulating valve (3) and the flow meter (4), and the outlet pipeline of the flow meter (4); a fifth pressure sensor (26) is provided on the pipeline between the molten salt tank (1) and the pressure reducing valve (27), and a sixth pressure sensor (30) is provided on the outlet pipeline of the fifth shut-off valve (29).

2. The cyclic experimental loop system for fatigue and leakage testing of flexible connection components as described in claim 1, characterized in that: The molten salt tank (1) is installed at the lowest position of the main experimental circuit. The pipes at both ends of the flow meter (4) are arranged horizontally. All other pipes in the main experimental circuit except for the pipes at both ends of the flow meter (4) are inclined towards the molten salt tank (1).

3. The cyclic experimental loop system for fatigue and leakage testing of flexible connection components as described in claim 1, characterized in that: The motion component includes a rotating shaft (505), a hydraulic cylinder that drives the flexible component to rotate, and a hydraulic push rod that drives the flexible component to translate. The hydraulic cylinder and the hydraulic push rod are respectively connected to the flexible component via the rotating shaft (505). The flexible component includes a test pipeline, with flexible hoses (502) connected to both ends of the test pipeline. The end of the flexible hose (502) away from the test pipeline is connected to the main experimental circuit via a rotary joint (501). Force sensors are respectively installed at both ends of the test pipeline near the flexible hoses (502). The rotary joint (501) is also connected to a rotating shaft (505) that drives the corresponding flexible hose (502) to rotate. A torque sensor (504) is installed on the rotating shaft (505).

4. The cyclic experimental loop system for fatigue and leakage testing of flexible connection components as described in claim 1, characterized in that: The main experimental circuit where the first shut-off valve (14) and the second shut-off valve (15) are located is a downward-opening "∩" shaped bend (506). The first shut-off valve (14) and the second shut-off valve (15) are located at the top of the opening of the "∩" shaped bend (506). The connection position between the gas seal pipeline and the corresponding side "∩" pipeline is located on the side of the shut-off valve near the test section (5).

5. The cyclic experimental loop system for fatigue and leakage testing of flexible connection components as described in claim 1, characterized in that: The bottom of the inner cavity of the molten salt tank (1) is equipped with a molten salt pump (2) for pumping molten salt into the main experimental circuit. The molten salt pump (2) is a molten salt submersible pump with a centrifugal impeller. The upper part of the inner cavity of the molten salt tank (1) is equipped with a level gauge (8), a pressure gauge (9) and an insertion thermocouple (10).

6. An experimental method for a fatigue testing loop of a flexible connection component, characterized in that: A cyclic experimental circuit system for fatigue and leakage testing of flexible connection components as described in any one of claims 1 to 5 is used for fatigue testing of flexible connections in dynamic molten salt. Includes the following steps: S1: Open the sixth shut-off valve (32), turn on the vacuum pump (31), remove excess air from the molten salt tank (1), and at the same time open the fourth shut-off valve (28) and the fifth shut-off valve (29), open the pressure reducing valve (27), replace the air with nitrogen in the nitrogen cylinder (25) and use it as the pressurizing medium for the main experimental circuit, and then close the vacuum pump (31) and the sixth shut-off valve (32), pressurize only the inside of the main experimental circuit, and close the fifth shut-off valve (29) when the readings of each pressure sensor in the main experimental circuit reach the test pressure reading. S2: Close the third shut-off valve (16), open the first shut-off valve (14) and the second shut-off valve (15), adjust the rotating test section (5) so that the test section (5) is at the lowest position in the rotation direction, turn on the first heater (11) to heat and melt the molten salt, turn on the molten salt pump (2), adjust the opening of the regulating valve (3) so that the flow rate of the main experimental circuit reaches the actual working condition flow rate, turn on the second heater (12) to reheat the molten salt to reach the set test temperature; S3: After the temperature and pressure in the experimental circuit have stabilized, the motion component of the test section (5) is turned on to perform fatigue testing on the flexible connection component, and the number of tests is recorded by the terminal. S4: During the test experiment, observe the readings of the first pressure sensor (17) and the second pressure sensor (19), calculate and record the pressure difference between them; S5: After the test, shut off the molten salt pump (2), the first heater (11), the second heater (12), the pressure reducing valve (27) and the fourth shut-off valve (28), and adjust the test section (5) to its highest position during rotation. After the molten salt has finished flowing back and dropped to a safe temperature, and the internal pressure of the experimental circuit has dropped to the standard atmospheric pressure, disassemble the flexible connection component of the test section (5), collect the molten salt leakage particles, and analyze the leakage and fatigue characteristics by combining the numerical changes of the first pressure sensor (17), the second pressure sensor (19), the force sensor (503) and the torque sensor (504). S6: If a large amount of molten salt leaks out uncontrollably during the experiment, immediately open the third shut-off valve (16) to disconnect part of the test section (5), and then shut off the molten salt pump (2), the first heater (11), the second heater (12), the pressure reducing valve (27) and the fourth shut-off valve (28) in sequence.

7. An experimental method for a fatigue testing loop of a flexible connection component, characterized in that: A flexible connection component fatigue and leakage test cyclic experimental loop system as described in any one of claims 1 to 5 is used for static molten salt fatigue testing of flexible connections, comprising the following steps: S1: Keep the first shut-off valve (14) and the second shut-off valve (15) open in the main experimental circuit, and the third shut-off valve (16) closed. Adjust the rotating test section (5) so that the test section (5) is at the lowest position in the rotation direction. S2: Turn on the first heater (11), heat the molten salt to a certain temperature, and then turn on the molten salt pump (2). S3: After the test circuit is filled with molten salt, turn off the molten salt pump (2), then turn on the third heater (13), and close the first shut-off valve (14) and the second shut-off valve (15). S4: Open the pressure reducing valve (27) and the fifth shut-off valve (29) to pressurize both ends of the test section (5) so that the working medium is sealed in the test section (5). After reaching the specified pressure, close the pressure reducing valve (27) and the fifth shut-off valve (29). S5: Perform fatigue testing on the flexible connection components, and record the number of tests by the terminal. S6: After the test is completed, turn off the third heater (13), adjust the rotating test section (5) so that the test section (5) is at the highest position in the rotation direction. After the molten salt has finished flowing back, open the drain valve (33) to remove the remaining molten salt inside the test section (5). After the temperature of the test section (5) drops to a safe temperature, disassemble the flexible connection assembly of the test section (5), collect the molten salt leakage particles, and analyze the leakage and fatigue characteristics by combining the numerical changes of the first pressure sensor (17), the second pressure sensor (19), the force sensor (503), and the torque sensor (504).

Images