Device and method for testing performance of T-shaped connection node in fused salt storage tank under corrosion and load effects

Abstract

The invention provides a device and a method for testing the performance of a T-shaped connection node in a fused salt storage tank under the action of corrosion and load. The testing device comprises a vertical actuator, a horizontal actuator, a high-temperature fused salt pond and a leveling frame system, a loading system base is arranged at the bottom of the leveling frame system, the high-temperature molten salt pond is installed on the leveling frame system, a T-shaped test piece is further arranged in the high-temperature molten salt pond and is a T-shaped connecting node formed by welding a storage tank bottom plate and a storage tank wall plate, the outer side of the high-temperature molten salt pond is transversely connected with a horizontal actuator, and the horizontal actuator is connected with the high-temperature molten salt pond. And a vertical actuator is arranged above the high-temperature molten salt pond and corresponds to the T-shaped test piece. According to the testing device and the testing method, the effect of high-temperature fused salt on the T-shaped connecting part in the storage tank can be efficiently and conveniently simulated, stress corrosion and corrosion fatigue data of the T-shaped test piece are obtained, and experimental conditions are laid for life evaluation of an existing fused salt storage tank and development and design work of a new generation of fused salt storage tanks.

Description

Technical Field

[0001] The present invention belongs to the technical field of supporting testing equipment for molten salt storage tanks, and in particular relates to a device and method for testing the performance of a T-shaped connection node in a molten salt storage tank under corrosion and load. Background Art

[0002] Developing and utilizing renewable energy for power generation is essential for achieving carbon neutrality. Deploying large-scale thermal energy storage systems (TES) is the most promising technological solution for overcoming their intermittent and volatile nature. Large-scale TES, due to their high cost-effectiveness, large-scale feasibility, long lifespan, environmental friendliness, and low geographic location requirements, are widely applicable in waste power utilization, grid peak regulation, centralized heating, and combined heat, power, and cooling (CHCC) applications. High-temperature molten salt storage tanks are the core equipment for storing thermal energy in large-scale TES systems, storing heated, high-temperature liquid molten salt. The operating temperature of the high-temperature molten salt in currently commercially available molten salt tanks is 560°C. The heat storage medium, primarily binary nitrate, has an upper temperature limit of 600°C. However, there is a lack of experimental data to support the fatigue performance of the T-junction between the tank wall and bottom under normal operating conditions and after earthquakes, as well as the lifespan prediction of the tank structure. The operating temperature of the new generation of high-temperature molten salt storage tanks currently in the research and development stage will exceed 700°C, and the heat storage medium molten salt will be replaced by chloride salt instead of nitrate. However, chloride salt is more corrosive than nitrate under high temperature conditions. Therefore, it is urgent to develop a testing system that can take into account the impact of molten salt corrosion on the stress performance of the tank structure.

[0003] The molten salt tank body is a vertical, variable-wall-thickness cylindrical thin-shell structure, constructed by welding steel plates together using vertical and circumferential welds. The tank roof is a fixed thin-shell dome, and the tank wall and bottom are connected using T-shaped butt welds. The connection between the tank bottom and the foundation is non-anchored, relying on the friction of the tank floor to limit the horizontal displacement of the structure. The most common failure of molten salt tanks is molten salt leakage, which occurs when cracks appear in the steel plate welds, leading to the leakage of liquid molten salt. The most critical weld in the tank is the T-shaped connection between the tank wall and bottom. Its stress corrosion and corrosion fatigue performance under the action of molten salt media and loads requires systematic analysis and research.

[0004] Currently, the main method for studying the effects of molten salt corrosion and loads on steel is stress corrosion testing. This type of testing differs significantly from the actual stress conditions and structural state under the action of corrosive media, resulting in a discrepancy between the material life predicted by the test results and the actual working conditions. There is also no good method for testing the effects of welds and their residual stresses under corrosive conditions. In actual tank bottom plate joints, the radial and circumferential welds reduce material ductility due to the heat-affected zone, reducing the fatigue life of the connection by approximately 30%. However, existing experiments and specifications do not consider the effects of such welds. Furthermore, under earthquake action, the tank bottom plate is subjected to a multiaxial stress state (radial tensile stress coupled with circumferential compressive stress) due to the pull-out effect, which significantly exacerbates the accumulation of plastic strain. However, traditional experimental studies have only focused on uniaxial tensile loads, resulting in deviations in fatigue life predictions. Existing testing technologies cannot accurately evaluate the stress performance of T-type connection nodes of storage tanks because they ignore the details of welds, the correlation and coupling between multi-axial loads and material corrosion damage mechanisms. It is urgent to establish a refined test method that integrates weld types, stress states and corrosion damage to lay the experimental foundation for accurately evaluating the stress and fatigue performance of T-type connection nodes of molten salt storage tanks and accurately predicting their lifespan.

[0005] Based on this, a performance testing device and method for T-type connection nodes in molten salt storage tanks under corrosion and load were proposed. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to address the deficiencies of the above-mentioned prior art and provide a performance testing device and method for T-type connection nodes in molten salt storage tanks under corrosion and load, so as to solve the problems raised in the above-mentioned background technology.

[0007] In order to solve the above technical problems, the technical solution adopted by the present invention is: In a first aspect, a performance testing device for a T-type connection node in a molten salt storage tank under corrosion and load includes a vertical actuator, a horizontal actuator, a high-temperature molten salt pool, and a leveling frame system; Among them, a loading system base is provided at the bottom of the leveling frame system, the high-temperature molten salt pool is installed on the leveling frame system, and a T-shaped test piece is also provided in the high-temperature molten salt pool. The T-shaped test piece is welded by the tank bottom plate and the tank wall plate. A horizontal actuator is laterally connected to the outside of the high-temperature molten salt pool, and a vertical actuator is provided above the high-temperature molten salt pool corresponding to the T-shaped test piece.

[0008] As a further explanation of the present invention, the leveling frame system consists of a leveling frame column, a leveling frame top plate and a leveling frame bottom plate. The leveling frame bottom plate is installed on the loading system base. The leveling frame top plate and the leveling frame bottom plate are arranged parallel to each other, and four leveling frame columns are symmetrically connected on both sides of the leveling frame top plate and the leveling frame bottom plate.

[0009] As a further explanation of the present invention, two high-temperature molten salt pool fixed beams are fixed to the outside of the high-temperature molten salt pool, a high-temperature molten salt pool fixed pad is fixed between one end of the two high-temperature molten salt pool fixed beams, and a high-temperature molten salt pool horizontal loading pad is fixed between one end of the two high-temperature molten salt pool fixed beams, and the horizontal actuator is connected to the high-temperature molten salt pool horizontal loading pad.

[0010] As a further illustration of the present invention, the top plate of the leveling frame is connected to the lower parts of the horizontal loading pad and the fixed pad of the high-temperature molten salt pool by bolts, and the connection between the high-temperature molten salt pool and the leveling frame system is completed through the horizontal loading pad and the fixed pad of the high-temperature molten salt pool and the top plate of the leveling frame.

[0011] As a further illustration of the present invention, the inner side of the horizontal loading pad is connected to a specimen loading plate through a pad, a specimen fixing plate is fixed on the specimen loading plate, and one end of the T-shaped test piece is fixed on the specimen fixing plate.

[0012] As a further illustration of the present invention, the tank bottom plate specimen is fixed on a specimen fixing plate, and the tank wall plate specimen is connected to a vertical actuator.

[0013] In a second aspect, a method for testing the performance of a T-type connection node in a molten salt storage tank under corrosion and load comprises the following steps: First, a T-shaped test piece is designed based on the T-shaped connection node between the wall and bottom of the existing molten salt storage tank in a 1:1 ratio. Then, the T-shaped test piece is installed in a high-temperature molten salt pool, and the vertical actuator and the horizontal actuator are connected. The vertical actuator applies a constant vertical force to the tank wall panel specimen of the T-shaped test piece to simulate the load of the molten salt tank superstructure on the T-shaped connection node. After the horizontal actuator applies the load, the T-shaped test piece reaches the actual load condition of the T-shaped connection node. After placing the molten salt in the high-temperature molten salt pool and heating the molten salt to a predetermined temperature, the horizontal actuator applies a unidirectional constant load to test the stress corrosion performance of the T-shaped connection node. The horizontal actuator applies a reciprocating load to test the corrosion fatigue performance of the T-shaped connection node to complete the test.

[0014] Compared with the prior art, the present invention has the following advantages: The present invention can analyze the influence of multiple factors such as different molten salt types, different molten salt temperatures, different weld types, and different plate thicknesses on the corrosion effect of high-temperature molten salt. Through the bidirectional loading system, it can simulate the stress corrosion cracking and corrosion fatigue fracture of components to simulate the complex alternating stress state of the molten salt storage tank during the molten salt circulation process and the coupled damage caused to the tank by the high-temperature molten salt medium. The cyclic loading mode can also simulate the stress performance and plasticity of the T-type connection node of the molten salt storage tank under extreme disaster conditions such as earthquakes, and evaluate the rotation capacity. The stress corrosion and corrosion fatigue data of the T-type test piece obtained by using this test device and method are closer to the effect of high-temperature molten salt on the tank, laying an experimental foundation for the life evaluation of existing molten salt storage tanks and the development and design of a new generation of molten salt storage tanks.

[0015] The horizontal actuator and leveling frame system in the present invention ensure that the high-temperature molten salt pool and the tank bottom plate specimen always remain horizontal during the loading process. This can not only ensure that the stress state of the T-type connection node is consistent with the actual working conditions, but also ensure that the liquid high-temperature molten salt does not overflow from the high-temperature molten salt pool during the experimental loading process, which is safe and practical.

[0016] The test device and test method in the present invention realize the direct coupling of molten salt corrosion and specimen stress, improve the traditional indirect coupling test method of immersion corrosion followed by loading, make the experimental test results closer to the operating status of the molten salt storage tank in actual engineering, and the experimental test results have greater application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a schematic diagram of the overall structure of the present invention; Figure 2 This is a front view of the overall structure of the present invention; Figure 3 This is a schematic diagram of another perspective of the present invention as a whole; Figure 4 This is a schematic diagram of the explosion of part of the structure of the high-temperature molten salt pool of the present invention; Figure 5 is a schematic diagram of the leveling frame system of the present invention; Figure 6 This is a schematic diagram of the oblique adjustment of the leveling frame system of the present invention; Figure 7 This is another schematic diagram of the oblique adjustment of the leveling frame system of the present invention; Figure 8 is a schematic diagram of a first type T-shaped test piece in an embodiment of the present invention; Figure 9 is a schematic diagram of a second type of T-shaped test piece in an embodiment of the present invention; Figure 10 Schematic diagram of the third type of T-shaped test piece in an embodiment of the present invention.

[0018] Description of reference numerals: 1. Vertical actuator; 2. Horizontal actuator; 3. T-type test piece; 3-1. Tank bottom plate; 3-2. Tank wall plate; 4. High-temperature molten salt pool; 5. High-temperature molten salt pool fixed beam; 6. High-temperature molten salt pool horizontal loading pad; 7. High-temperature molten salt pool fixed pad; 8. Leveling frame system; 8-1. Leveling frame column; 8-2. Leveling frame top plate; 8-3. Leveling frame bottom plate; 9. Loading system base; 10. Pad; 11. Specimen loading plate; 12. Specimen fixing plate. DETAILED DESCRIPTION

[0019] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0020] like Figure 1-7 As shown, the present invention provides a technical solution: a performance testing device for a T-type connection node in a molten salt storage tank under corrosion and load, comprising a vertical actuator 1, a horizontal actuator 2, a high-temperature molten salt pool 4 and a leveling frame system 8; Among them, the leveling frame system 8 is composed of a leveling frame column 8-1, a leveling frame top plate 8-2 and a leveling frame bottom plate 8-3. The leveling frame bottom plate 8-3 is installed on the loading system base 9. The leveling frame top plate 8-2 and the leveling frame bottom plate 8-3 are arranged parallel to each other, and four leveling frame columns 8-1 are symmetrically connected on both sides of the leveling frame top plate 8-2 and the leveling frame bottom plate 8-3. The relative positions of the leveling frame top plate 8-2 and the leveling frame bottom plate 8-3 can be adjusted through the leveling frame columns 8-1.

[0021] A loading system base 9 is provided at the bottom of the leveling frame system 8, and the high-temperature molten salt pool 4 is installed on the leveling frame system 8. The high-temperature molten salt pool 4 stores molten salt and is provided with a heating device to achieve precise control of the molten salt temperature of 300-800°C and ensure that the high-temperature liquid molten salt does not undergo phase change during the experiment. During use, the top of the high-temperature molten salt pool 4 is also covered with an anti-overflow cover.

[0022] Two high-temperature molten salt pool fixed beams 5 are fixed to the outside of the high-temperature molten salt pool 4, a high-temperature molten salt pool fixed pad 7 is fixed between one end of the two high-temperature molten salt pool fixed beams 5, and a high-temperature molten salt pool horizontal loading pad 6 is fixed between one end of the two high-temperature molten salt pool fixed beams 5, and the horizontal actuator 2 is connected to the high-temperature molten salt pool horizontal loading pad 6.

[0023] The top plate 8-2 of the leveling frame is connected to the lower part of the horizontal loading pad 6 and the fixed pad 7 of the high-temperature molten salt pool by bolts, and the connection between the high-temperature molten salt pool 4 and the leveling frame system 8 is completed through the horizontal loading pad 6 and the fixed pad 7 of the high-temperature molten salt pool and the top plate 8-2 of the leveling frame. A T-shaped test piece 3 is also provided in the high-temperature molten salt pool 4. The T-shaped test piece 3 includes a tank bottom plate 3-1 and a tank wall plate 3-2. The tank wall plate 3-2 is vertically fixed to the tank bottom plate 3-1. High-temperature strain gauges with a temperature resistance of 800°C are arranged in the welds and connection areas of the T-shaped test piece. Dynamic strain is collected synchronously in real time. During the test, a resistance probe immersed in the high-temperature liquid molten salt pool reflects the corrosion thickness loss by measuring the resistance change of the metal sheet.

[0024] A horizontal actuator 2 is laterally connected to the outside of the high-temperature molten salt pool 4, and a vertical actuator 1 is provided above the high-temperature molten salt pool 4 corresponding to the T-shaped test piece 3. The inner side of the horizontal loading pad 6 is connected to a specimen loading plate 11 through a pad 10, and a specimen fixing plate 12 is fixed on the specimen loading plate 11. The tank bottom plate 3-1 is fixed on the specimen fixing plate 12, and the tank wall plate 3-2 is connected to the vertical actuator 1.

[0025] The test method of the performance test device of the T-type connection node in the molten salt storage tank under corrosion and load includes the following steps: First, a T-type test piece 3 is designed at a 1:1 ratio based on the T-type connection node between the wall and the bottom of the existing molten salt storage tank. Since the weld is an important factor affecting the mechanical performance and stress corrosion of the T-type connection node, three different types of T-type test pieces 3 are designed to study the influence of this factor.

[0026] The first type of T-shaped test piece 3 is as follows Figure 8 As shown; only the butt weld between the tank bottom plate 3-1 and the tank wall plate 3-2 is provided; The second type of T-type test piece 3 is as follows Figure 9 As shown; add a butt weld of the tank bottom plate 3-1 arranged along the radial direction of the tank body, which intersects with the butt weld of the T-type connection node to achieve the reproduction of the two-way intersecting welds of the tank bottom in the project; The third type of T-type test piece 3 is as follows Figure 10 As shown; a circumferential weld is added at 3-1 of the tank bottom plate, and the bottom plates on both sides of the weld are designed to have variable thickness to achieve the reproduction of the weld at the thickened part of the tank wall plate in the project.

[0027] The steel used for T-type test piece 3 is 347H and Q345R, two types of steel commonly used in high-temperature and low-temperature tanks in actual projects. The molten salt is composed of the currently commercially available binary nitrate and the chloride salt proposed for the next generation of high-temperature molten salt storage tanks.

[0028] Then, the T-shaped test piece 3 is installed in the high-temperature molten salt pool 4, and the vertical actuator 1 and the horizontal actuator 2 are connected. A constant vertical force is applied to the tank wall plate 3-2 through the vertical actuator 1 to simulate the load of the molten salt tank superstructure on the T-shaped connection node. After the load is applied through the horizontal actuator 2, the T-shaped test piece 3 reaches the actual load condition of the T-shaped connection node. After the molten salt is placed in the high-temperature molten salt pool 4 and heated to a predetermined temperature; The horizontal actuator 2 applies and maintains a unidirectional constant load to test the stress corrosion performance of the T-type connection node, and the horizontal actuator 2 applies a reciprocating load to test the corrosion fatigue performance of the T-type connection node; During the loading process, the strain values ​​of the plate and weld areas in the T-type test piece 3 are continuously measured by high-temperature resistance strain gauges; by performing long-term loading under the condition of keeping the load constant, the high-temperature creep of the T-type test piece 3 can be measured.

[0029] Fiber Bragg grating corrosion sensors (FBGs) were deployed in key corrosion areas of the T-shaped test piece 3, and the monitoring results were used to distinguish between load and corrosion expansion stress. After loading was completed according to the loading procedure, the T-shaped test piece 3 was cut. The surface morphology of the components after high-temperature molten salt corrosion was observed using an electron microscope (SEM) at key stress-bearing areas such as plates and welds to evaluate the stress corrosion of the T-shaped test piece 3 under the action of high-temperature molten salt and load, completing the test.

[0030] Experimental example: A tank bottom plate 3-1 and a tank wall plate 3-2 with different thickness ratios were welded to form a T-shaped test piece 3 to analyze the effect of plate thickness on the mechanical performance of the T-shaped connection node; Unidirectional horizontal loading (stress corrosion): The horizontal actuator 2 applies a unidirectional horizontal displacement to achieve a tensile loading state on the tank bottom plate 3-1, and then applies a horizontal displacement in the opposite direction to achieve a compressive loading state on the tank bottom plate 3-1. The magnitude of the stress on the tank bottom plate 3-1 is controlled by setting different displacement values.

[0031] Cyclic horizontal loading (corrosion fatigue): A cyclic load from elastic to plastic is applied to the tank bottom plate 3-1 through the horizontal actuator 2. The relationship between the T-connection node angle and the displacement of the horizontal actuator 2 is obtained through geometric conversion. Loading is performed according to horizontal displacement control. The T-connection node angle increases by 0.02 radians during each cycle until the load reaches the maximum angle of 0.4 radians.

[0032] When the bidirectional loading system is loaded stably, solid molten salt at room temperature is added to the high-temperature molten salt pool 4 and then heated to reach the design temperature of the molten salt. At the same time, a control group is set up, that is, no molten salt is added and only load is applied for comparison.

[0033] Data acquisition: The loading data of vertical actuator 1 and horizontal actuator 2 are automatically recorded by the loading system, and the strain data of different areas of the specimen are collected using high-temperature strain gauges.

[0034] Result analysis: The classical weight loss method was used to calculate the corrosion rate of T-type connection nodes under different stress levels, molten salt temperatures and molten salt types under unidirectional horizontal loading conditions, and the influence of different factors on the stress corrosion of T-type connection nodes was analyzed.

[0035] The corrosion morphology of the components and welds was observed using a scanning electron microscope (SEM) to assess the differential effects of high-temperature molten salt on the base metal and weld consumables. The effects of high-temperature molten salt on the elastic-plastic rotational capacity and corrosion fatigue performance of the unanchored tank shell and bottom were compared with experimental results of uncorroded T-joints under cyclic horizontal loading.

[0036] It should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that includes a list of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus.

[0037] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A performance testing device for T-type connection nodes in molten salt storage tanks under corrosion and load, characterized by: It includes a vertical actuator (1), a horizontal actuator (2), a high-temperature molten salt pool (4), and a leveling frame system (8); The loading system base (9) is provided at the bottom of the leveling frame system (8), the high-temperature molten salt pool (4) is installed on the leveling frame system (8), and a T-shaped test piece (3) is also provided in the high-temperature molten salt pool (4). The T-shaped test piece (3) is welded to a tank bottom plate (3-1) and a tank wall plate (3-2). A horizontal actuator (2) is laterally connected to the outside of the high-temperature molten salt pool (4), and a vertical actuator (1) is provided above the high-temperature molten salt pool (4) at a position corresponding to the T-shaped test piece (3).

2. The performance testing device for a T-type connection node in a molten salt storage tank under corrosion and load according to claim 1 is characterized in that: The leveling frame system (8) is composed of a leveling frame column (8-1), a leveling frame top plate (8-2) and a leveling frame bottom plate (8-3); the leveling frame bottom plate (8-3) is mounted on a loading system base (9); the leveling frame top plate (8-2) and the leveling frame bottom plate (8-3) are arranged parallel to each other, and four leveling frame columns (8-1) are symmetrically connected on both sides of the leveling frame top plate (8-2) and the leveling frame bottom plate (8-3).

3. The performance testing device for a T-type connection node in a molten salt storage tank under corrosion and load according to claim 1 is characterized in that: Two high-temperature molten salt pool fixed beams (5) are fixed on the outside of the high-temperature molten salt pool (4), a high-temperature molten salt pool fixed pad (7) is fixed between one ends of the two high-temperature molten salt pool fixed beams (5), a high-temperature molten salt pool horizontal loading pad (6) is fixed between one ends of the two high-temperature molten salt pool fixed beams (5), and the horizontal actuator (2) is connected to the high-temperature molten salt pool horizontal loading pad (6).

4. The performance testing device for a T-type connection node in a molten salt storage tank under corrosion and load according to claim 3 is characterized in that: The leveling frame top plate (8-2) is connected to the lower parts of the high-temperature molten salt pool horizontal loading pad (6) and the high-temperature molten salt pool fixed pad (7) by bolts, and the connection between the high-temperature molten salt pool (4) and the leveling frame system (8) is completed through the high-temperature molten salt pool horizontal loading pad (6), the high-temperature molten salt pool fixed pad (7) and the leveling frame top plate (8-2).

5. The performance testing device for a T-type connection node in a molten salt storage tank under corrosion and load according to claim 3 is characterized in that: The inner side of the horizontal loading pad (6) is connected to a specimen loading plate (11) via a pad (10), a specimen fixing plate (12) is fixed on the specimen loading plate (11), and one end of the T-shaped test piece (3) is fixed on the specimen fixing plate (12).

6. The performance testing device for a T-type connection node in a molten salt storage tank under corrosion and load according to claim 5, characterized in that: The tank bottom plate (3-1) is fixed on a specimen fixing plate (12), and the tank wall plate (3-2) is connected to a vertical actuator (1).

7. A method for testing the performance of a T-type connection node in a molten salt storage tank under corrosion and load, using a performance testing device for a T-type connection node in a molten salt storage tank under corrosion and load according to any one of claims 1 to 6, characterized in that: The steps include: First, a T-type test piece (3) is designed with the T-type connection node between the existing molten salt storage tank wall and the tank bottom in a 1:1 ratio. Then, the T-type test piece (3) is installed in a high-temperature molten salt pool (4), and the vertical actuator (1) and the horizontal actuator (2) are connected. A constant vertical force is applied to the tank wall plate (3-2) of the T-type test piece (3) through the vertical actuator (1) to simulate the load of the upper structure of the molten salt storage tank on the T-type connection node. After the load is applied by the horizontal actuator (2), the T-type test piece (3) reaches the actual load condition of the T-type connection node. After the molten salt is placed in the high-temperature molten salt pool (4) and heated to a predetermined temperature, the horizontal actuator (2) applies a unidirectional constant load to test the stress corrosion performance of the T-type connection node. The horizontal actuator (2) applies a reciprocating load to test the corrosion fatigue performance of the T-type connection node, and the test is completed.

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