A method for constructing a scale model of flexible foundation settlement of a molten salt storage tank

Abstract

The present application relates to a kind of analog molten salt storage tank flexible foundation settlement scale model construction method, belong to molten salt heat storage technical field, to the foundation of molten salt storage tank establishes physical scale model, simulates the settlement of original model foundation under corresponding condition, to provide reference for foundation structure optimization design.The present application successively includes the following steps: simplification model and selection key parameter, derivation similarity criterion, select model material, determine similarity coefficient, build scale model, determination and conversion.The scale model in the present application uses the same foundation material as original model, and according to similarity relationship and correction formula, the settlement result of scale model is converted into the result of original model, which helps to replace the full-size test of molten salt storage tank flexible foundation settlement, improves the operability of test, and provides effective test method for molten salt storage tank flexible foundation settlement measurement.

Description

Technical Field

[0001] This invention belongs to the field of molten salt thermal energy storage technology, specifically relating to a method for constructing a scaled model to simulate the settlement of flexible foundations for molten salt storage tanks. Background Technology

[0002] With the continued advancement of the "dual carbon" target, the installed capacity of new energy power generation such as wind and solar power has continued to grow. However, due to the intermittent, volatile, and random characteristics of new energy power generation, the new power system faces significant regulation pressure during operation. To address the challenges brought about by the large-scale grid connection of new energy sources, energy storage, as an important regulation technology, has become a key supporting technology for improving the stability and flexibility of the new power system.

[0003] Molten salt energy storage technology is a medium-to-high temperature energy storage method characterized by high thermal density, low steam pressure, and a wide applicable temperature range. It enables large-capacity, long-term energy storage by heating molten salt with solar energy, electricity, or industrial waste heat to store and release energy. It plays a crucial role in peak shaving, frequency regulation, power ramping, and green energy consumption in new power systems. For example, molten salt energy storage technology is currently widely used in solar thermal power plants, large-scale integrated wind-solar-thermal-storage energy bases, flexible retrofitting of thermal power units, and industrial park heating.

[0004] Molten salt thermal storage tanks are key equipment in molten salt energy storage systems, used to store high-temperature and low-temperature molten salt media and coupled with steam generation systems to achieve the storage and release of thermal energy. During operation, due to the high operating temperature (565℃) and large load-bearing capacity (10,000~35,000t) of molten salt tanks, the high temperature and mechanical loads acting on the flexible foundation of the tanks can easily lead to non-uniform settlement, which can result in serious safety accidents such as tank leaks. Reports indicate that the Gema Solar power plant in Spain and the Crescent Dunes power plant in the United States both experienced molten salt tank leaks due to non-uniform foundation settlement, resulting in significant economic losses.

[0005] Although numerous tests have been conducted on the non-uniform settlement around large storage tanks, the settlement test research on flexible foundations for molten salt storage tanks containing multi-layer composite materials under high-temperature and heavy-load service still has the following shortcomings:

[0006] (1) Molten salt storage tanks have high operating temperatures and large structural dimensions, making it difficult to install settlement monitoring devices in the bottom plate and foundation of molten salt storage tanks in actual projects that have been put into operation.

[0007] (2) Considering manufacturing, processing and material factors, the cost of constructing a full-size molten salt tank model is high and the construction is difficult. Therefore, it is necessary to construct a scaled physical model of the molten salt tank foundation in a laboratory environment to accurately simulate the settlement change law of the foundation.

[0008] (3) There are already scaled models built in laboratory testing environments for foundation structures such as buildings, bridges and ambient temperature oil tanks, mainly based on the geometric and load similarity principle under ambient temperature conditions, and related research work has been carried out. However, this method cannot be applied to the flexible foundation structure requirements of high temperature molten salt storage tanks.

[0009] (4) In actual engineering, the technology for monitoring the settlement around the tank is relatively mature, but there are few tests on the settlement of the tank bottom plate.

[0010] Therefore, in order to address the shortcomings of existing technologies, a scaled-down model construction method for simulating the settlement of flexible foundations of molten salt storage tanks is proposed. This method facilitates the testing of foundation settlement characteristics in a subsequent laboratory environment, thereby guiding the optimized design of molten salt storage tank foundations in practical engineering. Summary of the Invention

[0011] The present invention aims to provide a method for constructing a scaled model to simulate the settlement of flexible foundations of molten salt storage tanks, so as to overcome the shortcomings of the prior art. It establishes a physical scaled model of the foundation of molten salt storage tanks and simulates the settlement of the original model foundation under corresponding conditions, thereby providing a reference for the optimized design of foundation structures.

[0012] To achieve the above objectives, the present invention provides the following technical solution: a method for constructing a scaled model to simulate the settlement of a flexible foundation for a molten salt storage tank, comprising the following steps:

[0013] S1. Simplify the model and select key parameters: First, based on the geometric structure of the flexible foundation of the molten salt storage tank, simplify the physical model to obtain the original model; then, based on the settlement characteristics of the tank foundation, select the key physical quantities that affect the foundation settlement in the original model for later use; the key physical quantities include the mechanical and thermal properties of the foundation material, as well as the flow heat transfer parameters of the cooling duct.

[0014] S2. Derive similarity criteria: Using the similarity π theorem and dimensional analysis, construct dimensional matrices for the key physical quantities selected in step S1 and conduct dimensional analysis. Construct dimensional matrices to determine the mechanical dimensionless criteria and the convective heat transfer dimensionless criteria for cooling and ventilation of the key physical quantities. The mechanical dimensionless criteria and the convective heat transfer dimensionless criteria form the similarity criteria between the scaled model and the original model.

[0015] S3. Selecting Model Materials: First, determine the material selection method for the scaled-down model based on the similarity criteria determined in step S2; then, assume that the foundation of the original model and the corresponding scaled-down model uses the same material, and set the similarity coefficients of the material's elastic modulus, Poisson's ratio, thermal conductivity, material density, and coefficient of thermal expansion to be 1.

[0016] S4. Determine the similarity coefficient: Based on the structural dimensions of the foundation of the flexible molten salt storage tank, and on the premise of ensuring the thickness of the key structural layer inside the foundation and the smooth laying of the corresponding scale model, determine the geometric scaling ratio. Derive the similarity coefficients of physical quantities other than the foundation thickness from the similarity criteria determined in step S2, and determine the similarity coefficient between foundation settlement and geometric scaling ratio.

[0017] S5. Construct a scaled-down model: Based on the similarity criteria and similarity coefficients determined in steps S3 and S4, obtain the thickness of each structural layer of the foundation, the size and spacing of the ventilation ducts, and determine the uniformly distributed load, temperature boundary, ventilation heat transfer boundary and gravity load on the top surface according to the similarity relationship. Construct a scaled-down model and simulate the settlement change law of the tank foundation under high temperature and heavy load under laboratory conditions.

[0018] S6. Measurement and Conversion: Due to the scaled-down model of the molten salt storage tank's flexible foundation, the settlement caused by the self-weight stress of the scaled-down model cannot be directly converted using the geometric scaling ratio under the simultaneous action of temperature, uniformly distributed surface load, and gravitational acceleration. To calculate the settlement of the original model foundation, the incremental settlement caused by temperature load and uniformly distributed surface load, as well as the self-weight settlement, in the scaled-down model should be corrected separately. This includes the following steps: First, after the settlement of the scaled-down model under its own weight tends to stabilize, record the self-weight settlement. Then, apply the temperature load, uniformly distributed surface load, and boundary conditions corresponding to the original model. Next, after the temperature field of the scaled-down model reaches a steady state and the settlement change tends to stabilize, measure the temperature and settlement at each point of the physical scaled-down model, and convert and correct the settlement of the original model tank foundation according to the similarity criteria determined in step S2, thus completing the construction of the scaled-down model of the molten salt storage tank's flexible foundation settlement. The correction formula is:

[0019] ; (1)

[0020] In equation (1), This represents the total settlement of the foundation of the original model; This represents the settlement of the foundation of the scaled model under its own weight settlement stability caused by temperature load, uniformly distributed surface load, and boundary conditions. This represents the settlement of the foundation of the scaled-down model under its own weight. It represents the geometric scaling ratio.

[0021] Further, in step S1, the mechanical and thermophysical parameters of the foundation material include: uniformly distributed surface load q, foundation thickness H, elastic modulus E, and Poisson's ratio ν. s Foundation settlement The coefficient of thermal expansion α s The ground temperature difference ΔT, the density of the ground material ρ, and the gravitational acceleration g;

[0022] The flow and heat transfer parameters of the cooling duct include: duct diameter d, air velocity u. air air kinematic viscosity ν air air thermal diffusivity α air air thermal conductivity λ air The air convection heat transfer coefficient h and the foundation thermal conductivity λ s .

[0023] Furthermore, in step S2, deriving the similarity criterion includes the following steps:

[0024] S2-1. The mechanical and thermal properties of the foundation material involve four fundamental dimensions: mass, length, time, and temperature. The dimensional matrix is ​​obtained and simplified to its simplest row matrix:

[0025] ; (2)

[0026] (3)

[0027] S2-2. Based on the similarity π theorem and combined with dimensional analysis, the dimensionless criteria for mechanics and the dimensionless criteria for convective heat transfer are obtained as follows:

[0028] The ratio π1 of foundation thickness to foundation settlement is:

[0029] (4)

[0030] The ratio π² of the elastic modulus of the foundation material to the uniformly distributed surface load on the foundation surface is:

[0031] (5)

[0032] The dimensionless criterion π3 for thermal strain inside the foundation is:

[0033] (6)

[0034] The ratio π4 of the transverse strain to the longitudinal strain within the foundation is:

[0035] (7)

[0036] The ratio π5 of the self-weight stress inside the foundation to the elastic modulus of the foundation material is:

[0037] (8)

[0038] The ratio of the inertial force to the viscous force of the air inside the cooling ventilation duct, π / 6 (i.e., the Reynolds number), is:

[0039] (9)

[0040] The ratio of the momentum diffusion capacity to the heat diffusion capacity of air inside a cooling ventilation duct, π / 7 (i.e., Prandtl number), is:

[0041] (10)

[0042] The ratio π / 8 (i.e., the Nusselt number) of the convective heat transfer intensity of the air in the cooling ventilation duct to the thermal conductivity of the fluid is:

[0043] (11)

[0044] The ratio π⁹ (i.e., the Biot number) of the thermal resistance of the foundation's internal thermal conductivity to the convective heat transfer resistance of the ventilation duct surface is:

[0045] ;(12)

[0046] In equations (2) to (12):

[0047] H is the thickness value of the foundation model, used to characterize the geometric dimensions of the foundation soil in the vertical direction, in meters;

[0048] s represents the settlement of the molten salt storage tank foundation, used to characterize the settlement of the foundation under high temperature and heavy load, and the unit is m;

[0049] q is the uniformly distributed load acting on the upper surface of the foundation, mainly generated by the self-weight of the molten salt storage tank and the self-weight of the molten salt inside the tank, and the unit is Pa;

[0050] E is the elastic modulus of the foundation model material, which is used to characterize the ability of the foundation soil to resist elastic deformation. It is a basic parameter describing the mechanical deformation characteristics of the foundation, and its unit is Pa.

[0051] α s The coefficient of thermal expansion of the foundation model material is used to characterize the ability of the foundation material to undergo thermal deformation under temperature conditions, and the unit is °C. -1 ;

[0052] ΔT is the temperature difference experienced by the foundation model, used to characterize the temperature difference caused by the transfer of heat from the molten salt tank to the interior of the foundation, in °C;

[0053] νs Poisson's ratio is the ratio of the absolute values ​​of the transverse normal strain to the longitudinal normal strain of the foundation material under stress. It is a dimensionless quantity.

[0054] ρ is the density of the foundation material, used to characterize the mass of a unit volume of foundation material, with units of kg / m³;

[0055] g represents gravitational acceleration, which is used to characterize the acceleration of foundation materials under the action of Earth's gravity, and the unit is m / s².

[0056] u air The air velocity in the cooling duct inside the foundation is used to characterize the air flow speed inside the duct, and the unit is m / s;

[0057] d is the diameter of the ventilation duct, used to characterize the geometric dimensions of the ventilation duct, and the unit is m;

[0058] ν air The kinematic viscosity of air in the cooling duct is used to characterize the momentum diffusion capacity and internal friction characteristics of air during flow, and the unit is m² / s;

[0059] α air is the thermal diffusivity of air in the cooling duct, used to characterize the relationship between the heat diffusion capacity and heat storage capacity of the air, with units of m² / s;

[0060] h is the convective heat transfer coefficient between the air inside the cooling duct and the duct wall, which is used to characterize the intensity of convective heat transfer between the air and the duct wall during the airflow process, and the unit is W / (m²·℃).

[0061] λ air Thermal conductivity is the thermal conductivity of air in a cooling duct, used to characterize the air's ability to conduct heat, and is expressed in W / (m·℃).

[0062] λ s is the thermal conductivity of the foundation material, used to characterize the ability of the solid foundation material to conduct heat, and the unit is W / (m·℃);

[0063] Furthermore, regarding the structure of the cooling duct, to ensure that the Reynolds number of the scaled-down model is similar to that of the original model, the scaled-down model should prioritize satisfying the similarity relationship of the air velocity in the duct. When the duct diameter and air velocity are limited, it will be difficult for the scaled-down model and the original model to meet the requirement of completely similar Reynolds numbers. Therefore, the scaled-down model and the original model should be kept in the same flow state (laminar or turbulent). In this case, parameters such as the air inlet pressure and temperature should be adjusted so that the equivalent convective heat transfer coefficient in the ventilation duct of the scaled-down model satisfies the similarity relationship.

[0064] Furthermore, in step S6, several radial measuring lines are uniformly arranged along the circumference below the bottom plate of the molten salt storage tank, and measuring points are uniformly arranged radially on each measuring line to form a grid of settlement measuring points for the bottom plate of the storage tank, which is used to measure the settlement distribution of the bottom plate of the scaled model storage tank.

[0065] Furthermore, in step S6, if only the settlement of the flexible foundation of the molten salt storage tank under operating conditions is investigated, the settlement caused by self-weight stress can be considered. After stabilization, this is recorded as the initial reference state. At this point, the displacement sensor readings are reset to zero, a temperature load and a uniformly distributed surface load are applied, the settlement relative to the initial reference state is measured, and the settlement of the original model foundation is converted according to the similarity relationship.

[0066] (13)

[0067] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0068] 1. This invention uses a scaled-down model to replace the full-scale test, reducing the test cost and implementation difficulty, enhancing the operability and economy of the test, and providing a reliable test method for the study of non-uniform settlement of molten salt storage tank foundations;

[0069] 2. When constructing the scaled-down model, this invention comprehensively considers the similarity requirements of the flexible foundation of the molten salt storage tank under high temperature and heavy load operation conditions. The scaled-down model uses the same materials as the original model foundation, without the need to screen or configure materials that simultaneously meet the requirements of heat transfer similarity and mechanical similarity, so as to accurately reflect the settlement characteristics of the original model foundation under the same conditions.

[0070] 3. This invention can convert and correct the foundation settlement distribution measured by the scaled model to the settlement distribution of the original model foundation through similarity relationships, thus making up for the inability to directly monitor the settlement of the tank bottom plate in actual engineering. Attached Figure Description

[0071] Figure 1 Schematic diagram of the foundation of a molten salt storage tank; in the diagram, 1 is a fine sand cushion layer, 2 is the first coarse sand cushion layer, 3 is a ceramsite layer, 4 is the second coarse sand cushion layer, 5 is a soil layer, 6 is a ventilation duct, 7 is a heat insulation wall, and 8 is a protective ring.

[0072] Figure 2 A flowchart for constructing a scaled-down model according to this invention;

[0073] Figure 3 Comparison of average settlement between the original model and the scaled model; in the figure, "uncorrected" indicates the settlement of the scaled model, "simple correction" indicates that the settlement is uniformly converted according to the geometric scaling ratio, and "partial correction" indicates that the settlement is converted according to formula (13). Detailed Implementation

[0074] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments.

[0075] In this embodiment, the following is adopted: Figure 1 The foundation structure of the molten salt storage tank shown is studied using the entire flexible foundation structure and the surrounding soil as the subjects.

[0076] like Figure 2 The method for constructing a scaled model to simulate the settlement of a flexible foundation for a molten salt storage tank, as shown, includes the following steps:

[0077] S1. Simplify the model and select key parameters:

[0078] First, based on the geometric structure of the flexible foundation of the molten salt storage tank, the physical model is simplified to obtain the original model. The geometric simplification process is as follows: structures with the same material or similar structural functions are merged to reduce model complexity. For example, the thinner fine sand cushion layer 1 and the first coarse sand cushion layer 2, with similar materials and structures, can be considered equivalent to a single sand cushion layer. Simultaneously, when constructing the scaled-down model, the influence range of the surrounding soil should also be taken into account.

[0079] Then, based on the settlement characteristics of the tank foundation, key physical quantities affecting foundation settlement are selected in the original model for later use; the key physical quantities include the mechanical and thermal properties of the foundation material, as well as the flow heat transfer parameters of the cooling duct.

[0080] The mechanical and thermophysical parameters of the foundation material include: uniformly distributed surface load q, foundation thickness H, elastic modulus E, and Poisson's ratio ν. s Foundation settlement The coefficient of thermal expansion α s The ground temperature difference ΔT, the density of the ground material ρ, and the gravitational acceleration g;

[0081] The flow and heat transfer parameters of the cooling duct include: duct diameter d, air velocity u. air air kinematic viscosity ν air air thermal diffusivity α air air thermal conductivity λ air The air convection heat transfer coefficient h and the foundation thermal conductivity λ s .

[0082] S2. Derivation of Similarity Criteria: Using the similarity π theorem and dimensional analysis, construct dimensional matrices for the key physical quantities selected in step S1 and conduct dimensional analysis. Construct the dimensional matrices to determine the dimensionless mechanical criteria and the dimensionless convective heat transfer criteria for cooling and ventilation of the key physical quantities. The dimensionless mechanical criteria and the dimensionless convective heat transfer criteria form the similarity criteria between the scaled model and the original model. The derivation of the similarity criteria includes the following steps:

[0083] S2-1. The mechanical and thermal properties of the foundation material involve four fundamental dimensions: mass, length, time, and temperature. The dimensional matrix is ​​obtained and simplified to its simplest row matrix:

[0084] ; (2)

[0085] (3)

[0086] S2-2. Based on the similarity π theorem and combined with dimensional analysis, the dimensionless criteria for mechanics and the dimensionless criteria for convective heat transfer are obtained as follows:

[0087] The ratio π1 of foundation thickness to foundation settlement is:

[0088] (4)

[0089] The ratio π² of the elastic modulus of the foundation material to the uniformly distributed surface load on the foundation surface is:

[0090] (5)

[0091] The dimensionless criterion π3 for thermal strain inside the foundation is:

[0092] (6)

[0093] The ratio π4 of the transverse strain to the longitudinal strain within the foundation is:

[0094] (7)

[0095] The ratio π5 of the self-weight stress inside the foundation to the elastic modulus of the foundation material is:

[0096] (8)

[0097] The ratio of the inertial force to the viscous force of the air inside the cooling ventilation duct, π / 6 (i.e., the Reynolds number), is:

[0098] (9)

[0099] The ratio of the momentum diffusion capacity to the heat diffusion capacity of air inside a cooling ventilation duct, π / 7 (i.e., Prandtl number), is:

[0100] (10)

[0101] The ratio π / 8 (i.e., the Nusselt number) of the convective heat transfer intensity of the air in the cooling ventilation duct to the thermal conductivity of the fluid is:

[0102] (11)

[0103] The ratio π⁹ (i.e., the Biot number) of the thermal resistance of the foundation's internal thermal conductivity to the convective heat transfer resistance of the ventilation duct surface is:

[0104] ;(12)

[0105] In equations (2) to (12):

[0106] H is the thickness value of the foundation model, used to characterize the geometric dimensions of the foundation soil in the vertical direction, in meters;

[0107] s represents the settlement of the molten salt storage tank foundation, used to characterize the settlement of the foundation under high temperature and heavy load, and the unit is m;

[0108] q is the uniformly distributed load acting on the upper surface of the foundation, mainly generated by the self-weight of the molten salt storage tank and the self-weight of the molten salt inside the tank, and the unit is Pa;

[0109] E is the elastic modulus of the foundation model material, which is used to characterize the ability of the foundation soil to resist elastic deformation. It is a basic parameter describing the mechanical deformation characteristics of the foundation, and its unit is Pa.

[0110] α s The coefficient of thermal expansion of the foundation model material is used to characterize the ability of the foundation material to undergo thermal deformation under temperature conditions, and the unit is °C. -1 ;

[0111] ΔT is the temperature difference experienced by the foundation model, used to characterize the temperature difference caused by the transfer of heat from the molten salt tank to the interior of the foundation, in °C;

[0112] ν s Poisson's ratio is the ratio of the absolute values ​​of the transverse normal strain to the longitudinal normal strain of the foundation material under stress. It is a dimensionless quantity.

[0113] ρ is the density of the foundation material, used to characterize the mass of a unit volume of foundation material, with units of kg / m³;

[0114] g represents gravitational acceleration, which is used to characterize the acceleration of foundation materials under the action of Earth's gravity, and the unit is m / s².

[0115] u air The air velocity in the cooling duct inside the foundation is used to characterize the air flow speed inside the duct, and the unit is m / s;

[0116] d is the diameter of the ventilation duct, used to characterize the geometric dimensions of the ventilation duct, and the unit is m;

[0117] ν airThe kinematic viscosity of air in the cooling duct is used to characterize the momentum diffusion capacity and internal friction characteristics of air during flow, and the unit is m² / s;

[0118] α air is the thermal diffusivity of air in the cooling duct, used to characterize the relationship between the heat diffusion capacity and heat storage capacity of the air, with units of m² / s;

[0119] h is the convective heat transfer coefficient between the air inside the cooling duct and the duct wall, which is used to characterize the intensity of convective heat transfer between the air and the duct wall during the airflow process, and the unit is W / (m²·℃).

[0120] λ air Thermal conductivity is the thermal conductivity of air in a cooling duct, used to characterize the air's ability to conduct heat, and is expressed in W / (m·℃).

[0121] λ s is the thermal conductivity of the foundation material, used to characterize the ability of the solid foundation material to conduct heat, and the unit is W / (m·℃).

[0122] All temperature units above can be replaced with Kelvin.

[0123] S3. Selecting Model Materials: First, the material selection method for the scaled-down model is determined according to the similarity criteria established in step S2. Then, the foundations of the original model and the corresponding scaled-down model are assumed to use the same material, and the similarity coefficients of the material's elastic modulus, Poisson's ratio, thermal conductivity, material density, and coefficient of thermal expansion are all set to 1. In this embodiment, considering that the flexible foundation of the molten salt storage tank consists of multiple layers such as soil, sand cushion, insulation layer, and bearing layer, different materials have different mechanical and thermal properties under high temperature and heavy load. If similar materials are used as substitutes, it is difficult to meet the similarity requirements of heat and force under similar conditions. Therefore, in step S3 of this embodiment, the scaled-down model uses the same material as the foundation of the original model.

[0124] In cooling ventilation ducts, to maintain Prandtl and Reynolds numbers, the scaled-down model uses the same air medium at the same temperature and pressure as the original model to ensure similarity in convective heat transfer. For the structure of the cooling duct, to ensure similarity in Reynolds numbers between the scaled-down and original models, the model should prioritize the similarity of air velocity within the duct. When duct diameter and air velocity are limited, the scaled-down model may struggle to achieve complete Reynolds number similarity with the original model. Therefore, the scaled-down model should maintain the same flow state (laminar or turbulent) as the original model. In this case, parameters such as air inlet pressure and temperature are adjusted to ensure the equivalent convective heat transfer coefficient within the ventilation duct of the scaled-down model satisfies the similarity relationship.

[0125] S4. Determine the similarity coefficient: Based on the structural dimensions of the foundation of the flexible molten salt storage tank, and on the premise of ensuring the thickness of the key structural layer inside the foundation and the smooth laying of the corresponding scale model, determine the geometric scaling ratio. Derive the similarity coefficients of physical quantities other than the foundation thickness from the similarity criteria determined in step S2, and determine the similarity coefficient between foundation settlement and geometric scaling ratio.

[0126] In this embodiment, the similarity coefficient of the model's geometric dimensions is set to C. H =H P / H m The similarity coefficients for the remaining operating parameters, thermal performance parameters, and mechanical parameters are defined as C. X =X P / X m As shown in Table 1.

[0127] .

[0128] S5. Construct a scaled-down model: Based on the similarity criteria and similarity coefficients determined in steps S3 and S4, obtain the thickness of each structural layer of the foundation, the size and spacing of the ventilation ducts, and determine the uniformly distributed load on the top surface, the temperature boundary, the ventilation and heat transfer boundary, and the gravity load according to the similarity relationship. Construct a scaled-down model and simulate the settlement change law of the tank foundation under high temperature and heavy load under laboratory conditions.

[0129] S6. Measurement and Conversion: First, to obtain the self-weight settlement of the scaled model, after the scaled model is built, it is left to stand still without applying temperature load or uniformly distributed surface load, and the settlement of each measuring point on the bottom plate of the tank is measured. After the settlement of the scaled model under its own weight tends to stabilize (i.e., the settlement rate of each measuring point is close to 0), the self-weight settlement is recorded. Subsequently, temperature loads, uniformly distributed surface loads, and boundary conditions corresponding to the original model are applied. Then, after the temperature field of the scaled model reaches a steady state and the settlement change tends to stabilize, the temperature and settlement at each point of the physical scaled model are measured, and the incremental settlement of each measuring point relative to the steady state of self-weight settlement is recorded. This settlement is the operational incremental settlement under the conditions of temperature load, uniformly distributed surface load, and ventilation cooling boundary conditions. The settlement of the original model tank foundation is converted and corrected according to the similarity criteria determined in step S2, thus completing the scaled-down model of the molten salt tank flexible foundation settlement. The total settlement of the original model is obtained through the correction formula, which is:

[0130] ; (1)

[0131] In equation (1), This represents the total settlement of the foundation of the original model; This represents the settlement of the foundation of the scaled model under its own weight settlement stability caused by temperature load, uniformly distributed surface load, and boundary conditions. This represents the settlement of the foundation of the scaled-down model under its own weight. It represents the geometric scaling ratio.

[0132] Furthermore, if we only investigate the settlement of the flexible foundation of the molten salt storage tank under operating conditions, we can consider the settlement caused by its own weight stress. After stabilization, this is recorded as the initial reference state. At this point, the displacement sensor readings are reset to zero, a temperature load and a uniformly distributed surface load are applied, the settlement relative to the initial reference state is measured, and the settlement of the original model foundation is converted according to the similarity relationship.

[0133] (13)

[0134] In this embodiment, in order to measure the settlement distribution of the bottom plate of the scaled model tank, in step S6, several radial measuring lines are uniformly arranged along the circumference below the bottom plate of the molten salt tank, and measuring points are uniformly arranged along the radial direction on each measuring line to form a grid of settlement measuring points for the bottom plate of the tank, which is used to measure the settlement distribution of the bottom plate of the scaled model tank, for example in the directions of 0°, 45°, 90°, 135°, 180°, 225°, 270° and 315°.

[0135] In this embodiment, to keep the boundary conditions of the scaled-down model the same as the original model, load and temperature constraints are applied in the following ways: a heating film is used to apply temperature to the top of the scaled-down model, and an insulation structure is set around the scaled-down model to reduce the interference of lateral heat dissipation on the test results; a hydraulic device is used to apply a uniformly distributed load to the upper surface of the scaled-down model, and the bottom boundary of the scaled-down model is set as a fixed boundary according to the constraint state of the original model.

[0136] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for constructing a scaled model to simulate the settlement of a flexible foundation for a molten salt storage tank, characterized in that, Includes the following steps: S1. Simplify the model and select key parameters: First, based on the geometric structure of the flexible foundation of the molten salt storage tank, simplify the physical model to obtain the original model; then, based on the settlement characteristics of the tank foundation, select the key physical quantities that affect the foundation settlement in the original model for later use; the key physical quantities include the mechanical and thermal properties of the foundation material, as well as the flow heat transfer parameters of the cooling duct. S2. Derive similarity criteria: Using the similarity π theorem and dimensional analysis, construct dimensional matrices for the key physical quantities selected in step S1 and conduct dimensional analysis. Construct dimensional matrices to determine the mechanical dimensionless criteria and the convective heat transfer dimensionless criteria for cooling and ventilation of the key physical quantities. The mechanical dimensionless criteria and the convective heat transfer dimensionless criteria form the similarity criteria between the scaled model and the original model. S3. Selecting Model Materials: First, determine the material selection method for the scaled-down model based on the similarity criteria determined in step S2; then, assume that the foundation of the original model and the corresponding scaled-down model uses the same material, and set the similarity coefficients of the material's elastic modulus, Poisson's ratio, thermal conductivity, material density, and coefficient of thermal expansion to be 1. S4. Determine the similarity coefficient: Based on the structural dimensions of the foundation of the flexible molten salt storage tank, and on the premise of ensuring the thickness of the key structural layer inside the foundation and the smooth laying of the corresponding scale model, determine the geometric scaling ratio. Derive the similarity coefficients of physical quantities other than the foundation thickness from the similarity criteria determined in step S2, and determine the similarity coefficient between foundation settlement and geometric scaling ratio. S5. Construct a scaled-down model: Based on the similarity criteria and similarity coefficients determined in steps S3 and S4, obtain the thickness of each structural layer of the foundation, the size and spacing of the ventilation ducts, and determine the uniformly distributed load, temperature boundary, ventilation heat transfer boundary and gravity load on the top surface according to the similarity relationship. Construct a scaled-down model and simulate the settlement change law of the tank foundation under high temperature and heavy load under laboratory conditions. S6. Measurement and Conversion: First, after the settlement of the scaled model under its own weight tends to stabilize, record the self-weight settlement. Then, apply the temperature load, uniformly distributed surface load, and boundary conditions corresponding to the original model. Next, after the temperature field of the scaled model reaches a steady state and the settlement change tends to stabilize, measure the temperature and settlement at each point of the physical scaled model. Then, convert and correct the settlement of the original model's tank foundation according to the similarity criteria determined in step S2, completing the construction of the scaled model for the settlement of the molten salt tank's flexible foundation. The correction formula is: ； （1） In equation (1), This represents the total settlement of the foundation of the original model; This represents the settlement of the foundation of the scaled model under its own weight settlement stability caused by temperature load, uniformly distributed surface load, and boundary conditions. This represents the settlement of the foundation of the scaled-down model under its own weight. It represents the geometric scaling ratio.

2. The method for constructing a scaled model to simulate the settlement of a flexible foundation for a molten salt storage tank according to claim 1, characterized in that: In step S1, the mechanical and thermophysical parameters of the foundation material include: uniformly distributed surface load q, foundation thickness H, elastic modulus E, and Poisson's ratio ν. s Foundation settlement The coefficient of thermal expansion α s The ground temperature difference ΔT, the density of the ground material ρ, and the gravitational acceleration g; The flow and heat transfer parameters of the cooling duct include: duct diameter d, air velocity u. air air kinematic viscosity ν air air thermal diffusivity α air air thermal conductivity λ air The air convection heat transfer coefficient h and the foundation thermal conductivity λ s .

3. A method for constructing a scaled model to simulate the settlement of a flexible foundation for a molten salt storage tank according to claim 1 or 2, characterized in that: In step S2, deriving the similarity criterion includes the following steps: S2-1. The mechanical and thermal properties of the foundation material involve four fundamental dimensions: mass, length, time, and temperature. The dimensional matrix is ​​obtained and simplified to its simplest row matrix: ； （2） ；（3） S2-2. Based on the similarity π theorem and combined with dimensional analysis, the dimensionless criteria for mechanics and the dimensionless criteria for convective heat transfer are obtained as follows: The ratio π1 of foundation thickness to foundation settlement is: ；（4） The ratio π² of the elastic modulus of the foundation material to the uniformly distributed surface load on the foundation surface is: ；（5） The dimensionless criterion π3 for thermal strain inside the foundation is: ；（6） The ratio π4 of the transverse strain to the longitudinal strain within the foundation is: ；（7） The ratio π5 of the self-weight stress inside the foundation to the elastic modulus of the foundation material is: ；（8） The ratio π6 of the inertial force to the viscous force of the air inside the cooling ventilation duct is: ；（9） The ratio π7 of the momentum diffusion capacity to the heat diffusion capacity of air inside the cooling ventilation duct is: ；（10） The ratio π8 of the convective heat transfer intensity of the air in the cooling ventilation duct to the thermal conductivity of the fluid is: ；（11） The ratio π9 of the internal thermal conductivity resistance of the foundation to the convective heat transfer resistance of the ventilation duct surface is: ； （12） In equations (2) to (12): H is the thickness of the foundation model in meters; s is the settlement of the molten salt tank foundation in meters; q is the uniformly distributed surface load acting on the upper surface of the foundation in Pa; E is the elastic modulus of the foundation model material in Pa; α s The coefficient of thermal expansion of the foundation model material is given in °C. -1 ΔT represents the temperature difference experienced by the foundation model, in °C; ν s ρ is the Poisson's ratio of the foundation model material, a dimensionless quantity; ρ is the density of the foundation material, in kg / m³; g is the acceleration due to gravity, in m / s²; u air ν represents the air velocity in the cooling ducts inside the foundation, in m / s; d represents the diameter of the ventilation duct, in m; air α is the kinematic viscosity of the air in the cooling duct, expressed in m² / s. air λ is the thermal diffusivity of the air in the cooling duct, in m² / s; h is the convective heat transfer coefficient between the air and the duct wall, in W / (m²·℃); air λ is the thermal conductivity of the air in the cooling duct, expressed in W / (m·℃); s is the thermal conductivity of the foundation material, expressed in W / (m·℃).

4. The method for constructing a scaled model to simulate the settlement of a flexible foundation for a molten salt storage tank according to claim 1, characterized in that: In step S6, several radial measuring lines are uniformly arranged along the circumference below the bottom plate of the molten salt storage tank, and measuring points are uniformly arranged radially on each measuring line to form a grid of settlement measuring points for the bottom plate of the storage tank, which is used to measure the settlement distribution of the bottom plate of the scaled model storage tank.

5. The method for constructing a scaled model to simulate the settlement of a flexible foundation for a molten salt storage tank according to claim 1, characterized in that, In step S6, if only the settlement of the flexible foundation of the molten salt storage tank under operating conditions is investigated, the settlement caused by self-weight stress can be considered. Once stabilized, this is recorded as the initial reference state; At this point, the displacement sensor readings are reset to zero, a temperature load and a uniformly distributed surface load are applied, the settlement relative to the initial reference state is measured, and the settlement of the original model foundation is converted according to the similarity relationship: (13).

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