Device and method for testing high-temperature mechanical properties of shell structure of fused salt storage tank

Abstract

The invention provides a molten salt storage tank shell structure high-temperature mechanical property test method and a test device, the test device comprises a gate-type reaction frame, an electric cylinder and a high-temperature molten salt pond, the gate-type reaction frame is fixedly provided with a base of the electric cylinder, the telescopic end of the electric cylinder is fixedly connected with a bearing box, and a molten salt storage tank test piece is placed in the bearing box; a high-temperature molten salt pond is arranged under the bearing box, a molten salt input pipe is arranged in the molten salt storage tank test piece, a thermocouple temperature sensor used for temperature monitoring and a high-temperature strain gauge used for strain monitoring are arranged on the molten salt storage tank test piece, and deformation monitoring equipment right facing the molten salt storage tank test piece is arranged on the inner wall of the bearing box. A heating device is arranged at the bottom of the high-temperature molten salt pond. The device is scientific and reasonable in structural design, high in practicability, simple to operate and accurate and reliable in test result, and provides high-reliability data support for material selection, service life prediction and structural optimization of the fused salt storage tank.

Description

Technical Field

[0001] The present invention belongs to the technical field of equipment for solar thermal power plants, and particularly relates to a high-temperature mechanical property testing device for a molten salt storage tank shell structure and a testing method therefor. Background Art

[0002] The molten salt storage tank is a core device in the energy storage system of a solar thermal power plant (CSP plant), and its function is to store the liquid high-temperature molten salt heated by solar energy. The shell structure of the molten salt storage tank works in a high-temperature environment above 500°C for a long time, and at the same time bears the thermo-mechanical coupling load caused by the periodic fluctuation of the molten salt liquid level. The existing testing methods for storage tanks are mainly based on conventional pressure vessel standards, which stipulate that the working temperature of the storage tank does not exceed 200°C. However, the high-temperature working state of the molten salt storage tank makes it impossible for the traditional hydrostatic test to reflect the high-temperature mechanical behavior of the molten salt storage tank shell structure under actual working conditions. For example, in the hydrostatic test, the temperature field is decoupled from the mechanical load, and it is impossible to simulate the thermal shock effect of the liquid high-temperature molten salt on the tank wall shell and the fatigue and stability problems of the storage tank shell structure caused by the circulation of the high-temperature molten salt, which will lead to significant deviations between the test results and the actual loading conditions of the molten salt storage tank. Moreover, the numerical simulation analysis method based on the traditional high-temperature material property test extended to the shell structure also has a large difference from the actual stress conditions of the molten salt storage tank. In addition, the existing methods lack quantitative measurement and analysis means for key parameters such as weld defects between the plates of the storage tank shell, geometric defects of the shell, and overall creep and progressive deformation of the shell structure. Therefore, it is difficult to capture the stress distribution at key parts and the high-temperature creep behavior of the overall molten salt storage tank shell structure. At the same time, it is difficult for the existing testing devices to synchronously achieve temperature field control, cyclic loading, and multi-dimensional deformation monitoring. For example, the non-contact optical measurement technology has poor data stability and large measurement errors in a high-temperature water vapor environment. In response to the above problems, although some researchers have tried to improve, there are still large differences from the actual stress conditions of the molten salt storage tank shell structure. Therefore, there is an urgent need to develop a testing method and device that can accurately simulate the dynamic load of high-temperature molten salt and support multi-parameter coupling analysis to provide a reliable basis for the life prediction and optimal design of molten salt storage tanks. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a high-temperature mechanical property testing device for a molten salt storage tank shell structure in view of the deficiencies of the above-mentioned prior art. The testing device has a scientific and reasonable structural design, strong practicability, simple operation, accurate and reliable test results, and provides high-reliability data support for the material selection, life prediction, and structural optimization of molten salt storage tanks.

[0004] To solve the above technical problems, the technical solution adopted by the present invention is as follows: A high-temperature mechanical property testing device for the shell structure of a molten salt storage tank, characterized in that it includes a gantry reaction frame, an electric cylinder, and a high-temperature molten salt pool. The base of the electric cylinder is fixedly installed on the gantry reaction frame. The telescopic end of the electric cylinder is fixedly connected to a load-bearing box. A molten salt storage tank specimen is placed in the load-bearing box. A high-temperature molten salt pool is arranged directly below the load-bearing box. A molten salt input pipe is arranged in the molten salt storage tank specimen. A thermocouple temperature sensor for temperature monitoring and a high-temperature strain gauge for strain monitoring are arranged on the molten salt storage tank specimen. A deformation monitoring device facing the molten salt storage tank specimen is arranged on the inner wall of the load-bearing box. A heating device is arranged at the bottom of the high-temperature molten salt pool.

[0005] Preferably, a salt distribution ring pipe is arranged in the molten salt storage tank specimen. One end of the molten salt input pipe is communicated with the salt distribution ring pipe, and the other end of the molten salt input pipe passes through the bottom surface of the load-bearing box and is communicated with a molten salt inlet. A plurality of injection nozzles are arranged on the salt distribution ring pipe.

[0006] Preferably, two circles of injection nozzles are arranged on the upper and lower sides of the salt distribution ring pipe, and the upper and lower rows of injection nozzles are arranged in a staggered manner.

[0007] Preferably, the upper row of injection nozzles is arranged to be inclined upward by 45° relative to the salt distribution ring pipe, and the lower row of injection nozzles is arranged to be inclined downward by 45° relative to the salt distribution ring pipe. The injection direction of the injection nozzle forms an included angle of 15-30° with the tangential direction of the inner wall of the molten salt storage tank specimen. The spacing between the injection nozzles in the same row is 1.2-1.5 times the diameter of the salt distribution ring pipe.

[0008] Preferably, a pressure relief valve is arranged at the top of the molten salt storage tank specimen to balance the internal and external pressures, and a one-way drain valve is arranged at the bottom of the molten salt storage tank specimen to drain the molten salt during the lifting process of the molten salt storage tank specimen.

[0009] Preferably, the scaling ratio of the molten salt storage tank specimen to the actual molten salt storage tank is 1:20 to 1:40. A plurality of the high-temperature strain gauges are arranged spirally along the side wall of the molten salt storage tank specimen. A plurality of the thermocouple temperature sensors are arranged on the side wall of the molten salt storage tank specimen in a 10×10 grid pattern. Four deformation monitoring devices are arranged at equal intervals on the periphery of the molten salt storage tank specimen. The measuring range of the high-temperature strain gauge is ±5%, and the temperature resistance limit is 800°C. The deformation monitoring device is a laser scanner with an accuracy of 0.01 mm.

[0010] A method for testing the high-temperature mechanical properties of the shell structure of a molten salt storage tank includes the following steps: S1. Cut and roll the steel and then weld it to make molten salt storage tank specimens of different specifications; S2. After the molten salt storage tank specimen is placed in the loading box and fixed, heat the high-temperature molten salt pool, set the molten salt temperature to 565 °C, control the electric cylinder to contract uniformly and reciprocally to drive the molten salt storage tank specimen to repeatedly enter and leave the high-temperature molten salt pool. When the electric cylinder moves downward, the molten salt in the high-temperature molten salt pool enters the salt distribution ring pipe through the molten salt inlet and flows out from the nozzles on the salt distribution ring pipe. When the electric cylinder moves upward, the molten salt is discharged through the one-way drain valve, so that the molten salt repeatedly enters and flows out of the molten salt storage tank specimen, simulating the no-load-full load-no-load cycle; S3. The high-temperature strain gauge collects data at fixed time intervals, and the deformation monitoring device scans the molten salt storage tank specimen at a fixed duration within each no-load-full load-no-load cycle; S4. Compare the deformation amounts of different molten salt storage tank specimens after the same number of cycles, and evaluate the integrity of the weld connection area and the progressive deformation of the overall molten salt storage tank specimen and the stability of the structure.

[0011] The present invention has the following advantages compared with the prior art: 1. The present invention can realize the dynamic high-precision reproduction of the high-temperature molten salt circulation process in the molten salt storage tank shell structure, and solves the core problems such as the non-coupling distortion of thermal-mechanical loads and the long test period existing in the traditional high-temperature test methods. The present invention does not rely on a molten salt pump to circulate the molten salt, so the high-temperature molten salt circulation process can be realized efficiently and at low cost, laying a foundation for the long-term and high-frequency cyclic test of the molten salt storage tank shell structure; since the molten salt circulation pump system is not used, the test cost can be fully reduced, and the damage of the molten salt to the equipment due to low-temperature phase change in the circulation system can be avoided. By dynamically monitoring the temperature, strain and overall deformation, the detection of the molten salt storage tank shell structure can be realized, and the temperature and strain of the key parts of the storage tank shell structure, as well as the structural overall deformation data such as the high-temperature creep of the shell and the progressive deformation of the overall structure, which cannot be obtained by traditional material property test methods, can be directly obtained, providing high-reliability data support for the material selection, life prediction and structural optimization of the molten salt storage tank, and meeting the strict requirements of the molten salt storage tank safety in the solar thermal power generation system.

[0012] 2. The present invention drives the molten salt storage tank specimen to move vertically in the molten salt pool through the electric cylinder, and can efficiently realize the continuous cyclic loading of the molten salt storage tank from an empty tank to a full tank without the aid of a molten salt pump in the laboratory; a ring-shaped salt distribution ring pipe is provided at the bottom of the storage tank specimen. When the electric cylinder moves downward, the molten salt in the high-temperature molten salt pool enters the salt distribution ring pipe through the holes at the bottom of the storage tank specimen and uniformly flows out from the nozzles on the salt distribution ring pipe. When the electric cylinder moves upward, the one-way valve provided at the bottom of the molten salt storage tank can be opened to discharge all the molten salt at the bottom of the tank, realizing the dynamic and uniform loading of the molten salt and solving the problem of the molten salt flow dead zone in the traditional test (molten salt pump cyclic loading).

[0013] 3. In the present invention, thermocouples and high-temperature strain gauges are arranged on the molten salt storage tank test piece to monitor the temperature and deformation of the tank wall with high precision during the loading process, and a laser scanner is combined to detect the progressive deformation and high-temperature creep of the molten salt storage tank shell structure after several cycles; a heating device is provided at the bottom of the high-temperature molten salt pool to achieve precise control of the molten salt temperature and ensure that the molten salt does not undergo a phase change.

[0014] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Description of the Drawings

[0015] Figure 1 is a schematic diagram of the overall structure of the present invention.

[0016] Figure 2 is a schematic front view of the cross-section of the molten salt storage tank test piece in the present invention.

[0017] Figure 3 is a schematic axonometric sectional view of the molten salt storage tank test piece in the present invention.

[0018] Description of the Reference Numerals: Detailed Embodiment

[0019] Embodiment 1 As Figures 1 to 3 shown, this embodiment provides a high-temperature mechanical property test device for the molten salt storage tank shell structure, including a gantry reaction frame 1, an electric cylinder 2, and a high-temperature molten salt pool 5. The base of the electric cylinder 2 is fixedly installed on the gantry reaction frame 1, and the telescopic end of the electric cylinder 2 is fixedly connected to a load-bearing box 3. A molten salt storage tank test piece 4 is placed in the load-bearing box 3. A high-temperature molten salt pool 5 is arranged directly below the load-bearing box 3. A molten salt input pipe 7 is arranged in the molten salt storage tank test piece 4. A thermocouple temperature sensor 12 for temperature monitoring and a high-temperature strain gauge 13 for strain monitoring are arranged on the molten salt storage tank test piece 4. A deformation monitoring device 14 facing the molten salt storage tank test piece 4 is arranged on the inner wall of the load-bearing box 3. A heating device is arranged at the bottom of the high-temperature molten salt pool 5.

[0020] In this embodiment, a salt distribution ring pipe 9 is arranged in the molten salt storage tank test piece 4. One end of the molten salt input pipe 7 is communicated with the salt distribution ring pipe 9, and the other end of the molten salt input pipe 7 passes through the bottom surface of the load-bearing box 3 and is communicated with a molten salt inlet 6. A plurality of spray nozzles 8 are arranged on the salt distribution ring pipe 9.

[0021] In this embodiment, two circles of spray nozzles 8 are arranged on the upper and lower sides of the salt distribution ring pipe 9, and the upper and lower rows of spray nozzles 8 are arranged in a staggered manner.

[0022] In this embodiment, the upper row of injection nozzles 8 is arranged obliquely upward at 45° relative to the salt distribution ring pipe 9, and the lower row of injection nozzles 8 is arranged obliquely downward at 45° relative to the salt distribution ring pipe 9. The injection direction of the injection nozzles 8 forms an included angle of 15° to 30° with the tangential direction of the inner wall of the molten salt storage tank specimen 4. The spacing between the injection nozzles 8 in the same row is 1.2 to 1.5 times the diameter of the salt distribution ring pipe 9.

[0023] In this embodiment, a pressure relief valve 10 is provided at the top of the molten salt storage tank specimen 4 to balance the internal and external pressures, and a one-way drain valve 11 is provided at the bottom of the molten salt storage tank specimen 4 to drain the molten salt during the lifting process of the molten salt storage tank specimen 4.

[0024] In this embodiment, the scaling ratio of the molten salt storage tank specimen 4 to the actual molten salt storage tank is 1:20 to 1:40. A plurality of the high-temperature strain gauges 13 are arranged spirally along the side wall of the molten salt storage tank specimen 4. A plurality of the thermocouple temperature sensors 12 are arranged on the side wall of the molten salt storage tank specimen 4 in a 10×10 grid pattern. Four deformation monitoring devices 14 are equidistantly arranged on the periphery of the molten salt storage tank specimen 4. The measuring range of the high-temperature strain gauge 13 is ±5%, and the temperature resistance limit is 800°C. The deformation monitoring device 14 is a laser scanner with an accuracy of 0.01 mm.

[0025] Embodiment 2 This embodiment provides a method for testing the high-temperature mechanical properties of the molten salt storage tank shell structure, including the following steps: S1. Laser cut stainless steel, determine the curvature of the steel according to the designed diameter of the molten salt storage tank specimen 4, and curl the steel. The curled steel is welded through vertical and circumferential welds to fabricate molten salt storage tank specimens 4 of different specifications. S2. After loading the molten salt storage tank specimen 4 into the loading box 3 and fixing it, when arranging the high-temperature strain gauges 13, focus on setting them at the weld positions. Heat the high-temperature molten salt pool 5, set the molten salt temperature to 565°C, and control the electric cylinder 2 to contract and drive the molten salt storage tank specimen 4 to repeatedly enter and leave the high-temperature molten salt pool 5 at a constant speed in a cyclic manner. When the electric cylinder 2 moves downward, the molten salt in the high-temperature molten salt pool 5 enters the salt distribution ring pipe 9 through the molten salt inlet 6 and flows out from the injection nozzles 8 on the salt distribution ring pipe 9. When the electric cylinder 2 moves upward, the molten salt is discharged through the one-way drain valve 11, so that the molten salt repeatedly enters and flows out of the molten salt storage tank specimen 4, simulating the cycle of no-load - full-load - no-load. The movement speed of the electric cylinder 2 can be controlled by the controller.

[0026] S3. The high-temperature strain gauges 13 collect data at fixed time intervals, and the deformation monitoring device 14 scans the molten salt storage tank specimen 4 at a fixed duration within each no-load - full-load - no-load cycle period. S4. Compare the deformation amounts of different molten salt storage tank specimens 4 after the same number of cycles, and evaluate the integrity of the weld connection area, the progressive deformation of the overall molten salt storage tank specimen 4, and the stability of the structure.

[0027] As described above, it is only a preferred embodiment of the present invention and does not impose any limitation on the present invention. Any simple modification, change, and equivalent variation made to the above embodiments according to the technical essence of the invention still fall within the protection scope of the technical solution of the present invention.

Claims

1. A high temperature mechanical properties testing device for a molten salt storage tank shell structure, characterized in that: The invention comprises a portal reaction frame (1), an electric cylinder (2) and a high-temperature molten salt pool (5), wherein a base of the electric cylinder (2) is fixedly mounted on the portal reaction frame (1), a telescopic end of the electric cylinder (2) is fixedly connected to a bearing box (3), a molten salt storage tank specimen (4) is placed in the bearing box (3), a high-temperature molten salt pool (5) is arranged directly below the bearing box (3), a molten salt input pipe (7) is arranged in the molten salt storage tank specimen (4), a thermocouple temperature sensor (12) for temperature monitoring and a high-temperature strain gauge (13) for strain monitoring are arranged on the molten salt storage tank specimen (4), and a deformation monitoring device (14) facing the molten salt storage tank specimen (4) is arranged on the inner wall of the bearing box (3).

2. A high temperature mechanical properties testing device for a molten salt storage tank shell structure according to claim 1, characterized in that: A salt distribution ring pipe (9) is arranged in the molten salt storage tank specimen (4); one end of the molten salt input pipe (7) is connected to the salt distribution ring pipe (9); the other end of the molten salt input pipe (7) passes through the bottom surface of the bearing box (3) and is connected to the molten salt inlet (6); and a plurality of injection nozzles (8) are arranged on the salt distribution ring pipe (9).

3. A high temperature mechanical properties testing device for a molten salt storage tank shell structure according to claim 2, characterized in that: Two circles of injection nozzles (8) are arranged on the upper and lower sides of the salt distribution ring pipe (9), and the upper and lower rows of injection nozzles (8) are arranged in a staggered manner.

4. A high temperature mechanical properties testing device for a molten salt storage tank shell structure according to claim 3, characterized in that: The upper row of injection nozzles (8) are arranged at an angle of 45° upward relative to the salt distribution ring tube (9), and the lower row of injection nozzles (8) are arranged at an angle of 45° downward relative to the salt distribution ring tube (9). The injection direction of the injection nozzles (8) and the tangential angle of the inner wall of the molten salt storage tank specimen (4) are 15 to 30 degrees, and the spacing between the injection nozzles (8) in the same row is 1.2 to 1.5 times the diameter of the salt distribution ring tube (9).

5. A high temperature mechanical properties testing device for a molten salt storage tank shell structure according to claim 1, characterized in that: A pressure relief valve (10) is arranged at the top of the molten salt storage tank specimen (4), and a one-way emptying valve (11) is arranged at the bottom of the molten salt storage tank specimen (4).

6. A high temperature mechanical properties testing device for a molten salt storage tank shell structure according to claim 1, characterized in that: The scale ratio of the molten salt storage tank specimen (4) to the actual molten salt storage tank is 1:20-1:40, a plurality of the high-temperature strain gauges (13) are spirally arranged along the side wall of the molten salt storage tank specimen (4), a plurality of the thermocouple temperature sensors (12) are arranged on the side wall of the molten salt storage tank specimen (4) in a 10×10 grid pattern, four deformation monitoring devices (14) are equidistantly arranged around the circumference of the molten salt storage tank specimen (4), the high-temperature strain gauge (13) has a range of ±5% and a temperature resistance limit of 800°C, and the deformation monitoring device (14) is a laser scanner with an accuracy of 0.01 mm.

7. A method for testing the high temperature mechanical properties of a molten salt storage tank shell structure using the high temperature mechanical properties testing device for the molten salt storage tank shell structure according to claims 1-6, characterized in that: The following steps are involved: S1, cutting steel, curling and welding to produce molten salt storage tank specimens of different specifications (4); S2, placing the molten salt storage tank specimen (4) into the carrying box (3), heating the high-temperature molten salt pool (5), setting the molten salt temperature to 565° C., controlling the electric cylinder (2) to uniformly reciprocate and contract to drive the molten salt storage tank specimen (4) to repeatedly enter and leave the high-temperature molten salt pool (5), so that the molten salt repeatedly enters and flows out of the molten salt storage tank specimen (4), simulating a cycle of no-load-full-load-no-load; S3, the high temperature strain gauge (13) collects data once at a fixed time interval, and the deformation monitoring device (14) scans the molten salt storage tank specimen (4) for a fixed time in each no-load-full-load-no-load cycle; S4. Compare the deformation of different molten salt storage tank specimens (4) after the same number of cycles to evaluate the integrity of the weld connection area and the overall progressive deformation and structural stability of the molten salt storage tank specimen (4).

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