An optimized design method for the wall panels of a molten salt storage tank with variable wall thickness and the storage tank

Abstract

The present invention belongs to the field of storage tanks, and discloses a method for optimizing the design of the wall panels of a molten salt storage tank with variable wall thickness and the storage tank. First, based on the finite element calculation method, the thickness of the dome is optimized to obtain the optimal wall thickness of the dome that meets the stability requirements under axial compression. Then, the minimum wall thickness that meets the stability requirements is obtained from the stress-strain curve of the single-layer wall panel under the combined action of axial compression and hydrostatic pressure and used as the optimal thickness of the bottom layer wall panel. Finally, based on the optimal thickness of the bottom layer wall panel and the thickness change range of adjacent two-layer wall panels, the optimal thickness and optimal height of each layer of wall panel are calculated layer by layer from bottom to top, and the condition that the current wall panel thickness is less than the optimal thickness of the dome is used as the iteration termination condition to obtain the optimal thickness of the top layer wall panel and the number of wall panel layers, thereby completing the optimization design of the wall panels of the molten salt storage tank with variable wall thickness. By using the stress-strain curve as the stability criterion, this method not only meets the structural stability requirements, but also saves the use of materials, taking into account both stability and cost.

Description

Technical Field

[0001] The present invention belongs to the technical field of heat storage, specifically to the technical field of storage tanks, and particularly relates to an optimized design method for the wall plates of a molten salt storage tank with variable wall thickness and a storage tank. Background Art

[0002] In a solar thermal power generation system, a concentrator focuses sunlight onto a receiver to generate high temperatures. The molten salt in the receiver is heated to a high-temperature liquid state and then transported through pipelines to a molten salt storage tank for storage. The high temperature of the molten salt can reach several hundred degrees Celsius, so a large amount of thermal energy can be stored to ensure continuous power generation even when there is no sunlight. Storage tanks are usually divided into high-temperature tanks and low-temperature tanks, and the molten salt is circulated and stored at different temperatures. When power generation is required, the high-temperature molten salt is pumped out of the storage tank, and the thermal energy is transferred to a working medium (water or other fluids) through a heat exchanger to generate high-temperature and high-pressure steam. The steam drives a steam turbine to generate electricity, and the cooled molten salt is returned to the low-temperature storage tank to wait for reheating.

[0003] The molten salt storage tank is the most core part of the heat storage system in a solar thermal power station. At the same time, the operating environment of the storage tank is extremely harsh. High temperature, variable liquid level, and generated thermal stress may all cause damage to the structure of the storage tank, resulting in leakage and posing serious safety hazards. Due to the huge size of the storage tank, in order to meet the strength requirements and economic requirements, the wall plates of the storage tank are usually designed as variable wall thickness wall plates. In the prior art, the common design methods for variable wall thickness wall plates are the fixed-point method or the variable-point method. Both the fixed-point method and the variable-point method are ideal theoretical design methods. However, the actual structure of the storage tank is relatively complex, and there are large errors when using the theoretical design method, which cannot ensure a uniform stress distribution; and in actual situations, if the strength performance is required to be met, using the above methods will result in a large amount of material consumption and a lot of material waste due to large errors; therefore, there are many difficulties in the structural design process of the storage tank.

[0004] It can be seen that the existing design methods for the wall plates of a molten salt storage tank with variable wall thickness, due to the actual structure of the storage tank and the large error between the design method and the actual situation, result in the problem that it is impossible to simultaneously meet the strength performance requirements and save materials. Summary of the Invention

[0005] The present invention provides an optimized design method for the wall plates of a molten salt storage tank with variable wall thickness and a storage tank to solve the technical problem that the existing design methods for the wall plates of a molten salt storage tank with variable wall thickness, due to the actual structure of the storage tank and the large error between the design method and the actual situation, result in the problem that it is impossible to simultaneously meet the strength performance requirements and save materials.

[0006] To achieve the above object, the present invention adopts the following technical content:

[0007] An optimized design method for the wall plates of a molten salt storage tank with variable wall thickness includes the following steps:

[0008] Obtain the optimal thickness of the dome of the physical model of a molten salt storage tank with variable wall thickness based on the finite element calculation method; wherein, the physical model of the molten salt storage tank with variable wall thickness is constructed from the actual tank dimensions;

[0009] Based on the stress-strain curve of the single-layer wall panel of the physical model of the molten salt storage tank with variable wall thickness under the combined action of axial compression and hydrostatic pressure, obtain the optimal thickness of the single-layer wall panel, and use the optimal thickness of the single-layer wall panel as the optimal thickness of the bottom layer wall panel;

[0010] Based on the optimal thickness of the bottom layer wall panel and the thickness change range of adjacent two layers of wall panels, iteratively calculate the optimal thickness and optimal height of each layer of wall panel layer by layer from bottom to top until the currently calculated wall panel thickness is less than the optimal thickness of the dome; use the wall panel thickness of the previous iteration before the iteration calculation stops as the optimal thickness of the top layer wall panel of the physical model of the molten salt storage tank with variable wall thickness, and simultaneously obtain the number of wall panel layers of the physical model of the molten salt storage tank with variable wall thickness.

[0011] Furthermore, the physical model of the molten salt storage tank with variable wall thickness includes a dome, multiple layers of wall panels with variable wall thickness, and a bottom plate; the material of the physical model of the molten salt storage tank with variable wall thickness is stainless steel 347H; during the modeling process of the physical model of the molten salt storage tank with variable wall thickness, the influence of the dome thickness change, wall panel thickness, and wall panel height change on the overall mechanical properties of the storage tank is considered, and the gravity of the storage tank, the axial pressure on the dome of the storage tank, and the hydrostatic pressure on the working medium in the storage tank are used as the boundary conditions of the physical model of the molten salt storage tank with variable wall thickness.

[0012] Furthermore, the specific steps for obtaining the optimal thickness of the dome of the physical model of the molten salt storage tank with variable wall thickness based on the finite element calculation method are as follows:

[0013] Calculate the dome of the physical model of the molten salt storage tank with variable wall thickness based on the finite element calculation method to obtain the corresponding stress-strain curve of the dome;

[0014] According to the corresponding stress-strain curve of the dome, obtain the optimal thickness of the dome under axial compression through structural stability judgment;

[0015] Among them, the judgment basis for structural stability is: when the stress-strain curve shows a linear change, it indicates that the structure is in the elastic deformation stage and has high stability; when the stress-strain curve shows a non-linear change, it means that the structure is in the plastic damage stage and has poor stability; use the minimum thickness within the elastic deformation range of the structure as the optimal thickness of the dome.

[0016] Furthermore, the specific steps for obtaining the optimal thickness of the single-layer wall panel based on the stress-strain curve of the single-layer wall panel of the physical model of the molten salt storage tank with variable wall thickness under the combined action of axial compression and hydrostatic pressure are as follows:

[0017] The variable-wall-thickness molten salt storage tank in the physical model of the variable-wall-thickness molten salt storage tank is regarded as an equal-wall-thickness molten salt storage tank;

[0018] Combined with the finite element calculation method, obtain the stress-strain curve of the single-layer wall panel of the equal-wall-thickness molten salt storage tank under the combined action of axial compression and hydrostatic pressure;

[0019] According to the stress-strain curve of the single-layer wall panel under the combined action of axial compression and hydrostatic pressure, obtain the minimum wall thickness that satisfies stability at the single-layer wall thickness, and use the minimum wall thickness that satisfies stability at the single-layer wall thickness as the optimal thickness of the single-layer wall panel.

[0020] Furthermore, the specific steps for layer-by-layer iterative calculation of the optimal thickness and optimal height of each layer of wall panel based on the optimal thickness of the bottom wall panel and the thickness change range of adjacent two layers of wall panels are as follows:

[0021] S1: Obtain the preliminary wall thickness of the second-layer wall panel according to the optimal thickness of the bottom wall panel and the thickness change range of adjacent two layers of wall panels;

[0022] S2: According to the preliminary wall thickness of the second-layer wall panel and the optimal thickness of the bottom wall panel, obtain the stress-strain curve of the bottom wall panel at different heights, and use the minimum height that satisfies stability as the optimal height of the bottom wall panel;

[0023] S3: According to the stress-strain curve of the thickness of the second-layer wall panel, use the minimum thickness that satisfies stability as the optimal thickness of the second-layer wall panel;

[0024] S4: Iteratively calculate the optimal thickness and optimal height of each layer of wall panel layer by layer until the currently calculated wall panel thickness is less than the optimal thickness of the arch top. Use the wall panel thickness of the previous iteration before the iteration calculation is terminated as the optimal thickness of the top layer wall panel of the variable-wall-thickness molten salt storage tank physical model and obtain the number of wall panel layers of the variable-wall-thickness molten salt storage tank physical model.

[0025] Furthermore, the optimal height of the top layer wall panel is calculated according to the preset total wall panel height and the optimal heights of each layer of wall panel. The specific formula is as follows:

[0026] Optimal height of the top layer wall panel = Preset total wall panel height - Sum of the optimal heights of each layer of wall panel.

[0027] Furthermore, the thickness change range of adjacent two layers of wall panels is 5% - 25%.

[0028] A variable-wall-thickness molten salt storage tank, the variable-wall-thickness molten salt storage tank includes multiple layers of variable-wall-thickness wall panels, and is designed by using the above-mentioned variable-wall-thickness molten salt storage tank wall panel optimization design method.

[0029] Furthermore, it includes a tank body surrounded by multiple layers of variable-wall-thickness wall panels; a bottom plate is arranged at the bottom of the tank body, and an arch top is covered at the top; a wind girder is sleeved axially on the tank body.

[0030] Furthermore, the vault includes radial beams, circumferential beams and diagonal braces; among them, the radial beams and the circumferential beams are made of HN350×170 H-shaped steel; the diagonal braces are made of HN250×125 H-shaped steel.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] The present invention provides a method for optimizing the design of the wall plates of a variable-wall-thickness molten salt storage tank. First, based on the finite element calculation method, the thickness of the vault is optimized to obtain the optimal wall thickness of the vault that meets the stability requirements under axial compression. Then, the minimum wall thickness that meets the stability requirements is obtained from the stress-strain curve of the single-layer wall plate under the combined action of axial compression and hydrostatic pressure and used as the optimal thickness of the bottom layer wall plate. Finally, based on the optimal thickness of the bottom layer wall plate and the thickness change range of adjacent two layers of wall plates, the optimal thickness and optimal height of each layer of wall plates are calculated layer by layer from bottom to top, and the iteration is terminated when the current wall plate thickness is less than the optimal thickness of the vault, so as to obtain the optimal thickness of the top layer wall plate and the number of wall plate layers, thereby completing the optimization design of the variable-wall-thickness molten salt storage tank wall plates. By using the stress-strain curve as the stability criterion, this method not only meets the structural stability requirements, but also saves the use of materials under the premise of stability, taking into account both stability and cost. By combining the finite element calculation method and the layer-by-layer iteration strategy, this method can accurately determine the optimal thickness and height of each layer of wall plates of the storage tank, maximize the utilization of materials, reduce material waste and cost on the premise of ensuring the structural stability of the storage tank, and has good popularization and application value.

[0033] Preferably, in the present invention, the physical model of the variable-wall-thickness molten salt storage tank uses stainless steel 347H, which ensures the corrosion resistance and structural strength of the storage tank in the high-temperature molten salt environment. At the same time, various factors affecting the mechanical properties of the storage tank are considered during the modeling process, and reasonable boundary conditions are set, making the model closer to the actual working conditions and improving the accuracy and reliability of the optimization design.

[0034] Preferably, in the present invention, through finite element calculation and structural stability judgment, the safety performance of the vault under axial compression is ensured, and the risk of structural failure caused by insufficient thickness is avoided, which provides important basic data support for the optimization design of the entire wall plate.

[0035] Preferably, in the present invention, the optimal thickness of the single-layer wall plate is obtained through finite element calculation. This step fully considers the stress conditions during the actual operation of the storage tank, ensures the stability and safety of the single-layer wall plate in the complex stress environment, and provides an important basis for the subsequent optimization design of the multi-layer wall plates.

[0036] Preferably, in the present invention, by gradually optimizing the thickness and height of each layer of wall panels, a refined design of the entire storage tank wall panel structure is achieved; this method not only improves the mechanical properties of the storage tank, but also reduces the manufacturing cost and weight.

[0037] Preferably, in the present invention, the optimal height of the top layer wall panel is determined by the difference between the preset total height of the wall panel and the optimal height of each layer of wall panel, ensuring that the height of the top layer wall panel not only meets the structural requirements but is not overly redundant, thus further improving the optimization design process of the storage tank wall panel and enhancing the scientificity and rationality of the design.

[0038] Preferably, in the present invention, the thickness change range between adjacent two layers of wall panels is 5% - 25%; this helps to maintain a reasonable change gradient of the wall panel thickness in the optimization design, avoiding problems such as stress concentration or structural mutation caused by excessive thickness change; at the same time, it also provides a guiding basis for the processing accuracy in the actual manufacturing process.

[0039] The present invention also provides a molten salt storage tank with variable wall thickness, designed based on the above-mentioned optimization design method for the wall panels of the molten salt storage tank with variable wall thickness. This storage tank can significantly improve the mechanical properties of the storage tank, reduce the manufacturing cost and extend the service life through the optimized wall panel structure, while taking into account the advantages of good structural performance and material saving; this storage tank has broad application prospects and important economic value in the molten salt energy storage system.

[0040] Preferably, in the present invention, the storage tank includes components such as a tank body surrounded by multiple layers of wall panels with variable wall thickness, a bottom plate, a dome, and a wind girder; the coordinated action of these components enables the storage tank to operate stably in a harsh natural environment, improving the safety and reliability of the storage tank.

[0041] Preferably, in the present invention, the dome adopts radial beams, circumferential beams, and diagonal braces made of HN steel, which not only improves the strength and stiffness of the dome, but also ensures the stability and durability of the dome, and is of great significance for improving the mechanical properties and safety performance of the entire storage tank. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 Schematic diagram of the overall structure of the storage tank provided by the embodiment of the present invention;

[0043] Figure 2 Schematic diagram of the dome structure provided by the embodiment of the present invention;

[0044] Figure 3 Schematic diagram of the relationship curve between the maximum deformation and the maximum stress under different dome thicknesses provided by the embodiment of the present invention; among them, (a) is the schematic diagram of the maximum deformation and the maximum stress under different dome thicknesses; (b) is the deformation nephogram of the dome; (c) is the stress nephogram of the dome;

[0045] Figure 4 Schematic diagram of the maximum deformation and maximum stress curves of the equal-wall-thickness tank wall under the combined action of axial compression and hydrostatic pressure provided by an embodiment of the present invention;

[0046] Figure 5 Schematic diagram of the maximum deformation and stress change curves of adjacent wall thickness changes provided by an embodiment of the present invention;

[0047] Figure 6 Schematic diagram of the maximum deformation and stress change curves of different wall plate heights in the first layer provided by an embodiment of the present invention;

[0048] Figure 7 Schematic diagram of the maximum deformation and stress change curves of different wall plate thicknesses in the second layer provided by an embodiment of the present invention;

[0049] Figure 8 Schematic diagram of the maximum deformation and stress change curves of different wall plate heights in the second layer provided by an embodiment of the present invention;

[0050] Figure 9 Schematic diagram of the maximum deformation and stress change curves of different wall plate thicknesses in the third layer provided by an embodiment of the present invention;

[0051] Figure 10 Schematic diagram of the maximum deformation and stress change curves of different wall plate heights in the third layer provided by an embodiment of the present invention;

[0052] Figure 11 Schematic diagram of the maximum deformation and stress change curves of different wall plate thicknesses in the fourth layer provided by an embodiment of the present invention;

[0053] Figure 12 Schematic diagram of the maximum deformation and stress change curves of different wall plate heights in the fourth layer provided by an embodiment of the present invention;

[0054] Figure 13 Schematic diagram of the maximum deformation and stress change curves of different wall plate thicknesses in the fifth layer provided by an embodiment of the present invention;

[0055] Figure 14 Schematic diagram of the maximum deformation and stress change curves of different wall plate heights in the fifth layer provided by an embodiment of the present invention;

[0056] Figure 15 Schematic diagram of the maximum deformation and stress change curves of different wall plate thicknesses in the sixth layer provided by an embodiment of the present invention;

[0057] Figure 16 Schematic diagram of the maximum deformation and stress change curves of different wall plate heights in the sixth layer provided by an embodiment of the present invention;

[0058] Figure 17Schematic diagram of the maximum deformation and stress change curves of the seventh layer with different wall panel thicknesses provided by the embodiments of the present invention;

[0059] Figure 18 Flow chart of an optimized design method for the wall panels of a molten salt storage tank with variable wall thickness provided by the embodiments of the present invention.

[0060] Reference numerals:

[0061] Bottom plate - 1; Wall panel - 2; Wind girder - 3; Dome - 4; Radial beam - 5; Circumferential beam - 6; Inclined support - 7. Detailed implementation manners

[0062] In order to make the technical problems, technical solutions and beneficial effects solved by the present invention clearer and more understandable, the following specific embodiments are used to further elaborate on the present invention in detail. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0063] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. Usually, the components of the embodiments of the present invention described and illustrated in the accompanying drawings herein can be arranged and designed in various different configurations.

[0064] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed present invention, but merely represents selected embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the scope of protection of the present invention.

[0065] It should be noted that: Similar reference numerals and letters denote similar items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings.

[0066] In the description of the embodiments of the present invention, it should be noted that if terms such as "upper", "lower", "horizontal", "inner", etc. are used to indicate the orientation or positional relationship, it is based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship in which the product of the invention is usually placed during use. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be construed as a limitation of the present invention. In addition, terms such as "first", "second", etc. are only used for differential description and cannot be construed as indicating or implying relative importance.

[0067] In addition, when the term "horizontal" appears, it does not mean that the component is required to be absolutely horizontal, but it can be slightly inclined. For example, "horizontal" only means that its direction is more horizontal relative to "vertical", and it does not mean that the structure must be completely horizontal, but it can be slightly inclined.

[0068] In the description of the embodiments of the present invention, it should also be noted that unless otherwise clearly specified and limited, when the terms "set", "installed", "connected", and "connected" appear, they should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected, or indirectly connected through an intermediate medium, and it can be the communication inside two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0069] Embodiment 1

[0070] Combined with what is mentioned in the background art, the operating environment of the storage tank is extremely harsh. High temperature, variable liquid level, and the generated thermal stress may all cause damage to the structure of the storage tank, resulting in leakage and posing serious potential safety hazards. Due to the huge size of the storage tank, in order to meet the strength requirements and economic requirements, the wall panels of the storage tank are designed as variable wall thickness wall panels. At present, the design of the storage tank mainly refers to the variable point method design. Especially for the height design of the storage tank wall panels, most of them use 1.8m - 2.8m as a fixed value. Therefore, optimizing the design of the storage tank can effectively improve the operating stability and reduce the material cost. In the prior art, the common design methods are the fixed point method or the variable point method. However, the actual structure of the storage tank is relatively complex, and there are large errors in using the theoretical design method. There are many difficulties in the structural design process of the storage tank. In addition, more importantly, the existing design methods for the wall panels of variable wall thickness molten salt storage tanks are difficult to balance the structural performance and the problem of saving materials.

[0071] To solve the above problems, the present invention provides an optimized design method for the wall panels of a variable wall thickness molten salt storage tank. This method is a variable wall thickness molten salt storage tank design optimization method based on the finite element calculation method and using the stress-strain curve for stability criterion. The storage tank designed by this method can improve the structural stability, save manufacturing materials, and reduce the manufacturing cost.

[0072] The following further describes the present invention in detail with reference to the drawings and embodiments:

[0073] As Figure 18 shown, this embodiment provides an optimized design method for the wall panels of a variable wall thickness molten salt storage tank. The specific steps include:

[0074] Obtain the optimal thickness of the dome 4 of the physical model of the variable wall thickness molten salt storage tank based on the finite element calculation method; wherein, the physical model of the variable wall thickness molten salt storage tank is constructed from the actual storage tank size;

[0075] Based on the stress-strain curve of a single-layer wall panel under the combined action of axial compression and hydrostatic pressure in a molten salt storage tank with variable wall thickness, obtain the optimal thickness of the single-layer wall panel, and use the optimal thickness of the single-layer wall panel as the optimal thickness of the bottom wall panel;

[0076] Based on the optimal thickness of the bottom wall panel and the thickness change range of adjacent two layers of wall panels, iteratively calculate the optimal thickness and optimal height of each layer of wall panel layer by layer from bottom to top until the currently calculated wall panel thickness is less than the optimal thickness of the dome 4; use the wall panel thickness of the previous iteration before the termination of the iterative calculation as the optimal thickness of the top wall panel of the molten salt storage tank with variable wall thickness physical model, and at the same time obtain the number of wall panel layers of the molten salt storage tank with variable wall thickness physical model.

[0077] In this embodiment, a physical model of a molten salt storage tank with variable wall thickness corresponding to the actual storage tank size is established. This model considers structures such as the storage tank dome, variable wall thickness wall panels, and bottom plates. The material is selected as the commonly used material stainless steel 347H for actual molten salt storage tanks in solar thermal power plants. Considering material nonlinearity, the inside of the storage tank is a homogeneous medium, and it is assumed that the density and elastic modulus do not change with temperature. For the boundary conditions, the gravity of the storage tank, the axial pressure on the storage tank dome, and the hydrostatic pressure of the working fluid in the storage tank are considered, and a fixed constraint is applied to the bottom surface of the tank bottom plate. In addition, during the modeling process, the influence of the dome thickness change, wall panel thickness, and wall panel height change on the overall mechanical properties of the storage tank is considered.

[0078] In this embodiment, for the physical model of the molten salt storage tank with variable wall thickness, based on the finite element calculation method, first, determine the optimal thickness of the dome under axial compression. The optimal thickness is obtained by judging the stability through the stress-strain curve obtained from the finite element analysis. The judgment basis for structural stability is: when the stress-strain curve is linearly changing, it indicates that the structure is in elastic deformation and has high stability; when the stress-strain curve shows non-linear changes, it indicates that the structure is in the plastic damage stage and the structure is very likely to become unstable and should be avoided. When the minimum thickness of the dome is determined, this thickness is used as the critical thickness for the change of the wall panel thickness, that is, the thickness of the topmost wall panel should be greater than or equal to the dome thickness.

[0079] Then, considering the mechanical stability of the variable-wall-thickness wall panels under axial compression + hydrostatic pressure, first determine the optimal wall thickness that satisfies stability when the overall wall thickness is a single layer, and use this optimal wall thickness as the thickness of the bottom layer of the variable-wall-thickness storage tank. Secondly, through the method of layer-by-layer iteration, determine the optimal thickness and optimal height of the second-layer wall panel, and then perform iterative calculations layer by layer upwards to obtain the optimal thickness and optimal height of each layer of wall panel. The determination basis for the number of layers is: when the thickness of the wall panel is less than or equal to the thickness of the arch top, the iteration terminates. At this time, the height of the topmost wall panel is the design height minus the optimal heights of each wall panel. Finally, obtain the optimal wall panel combination that satisfies the stability of the storage tank. Idea of the layer-by-layer iteration method: First, conduct research on different thicknesses of the overall storage tank under axial compression + hydrostatic pressure load, and determine the thickness range of the wall panel. The minimum wall panel thickness should be greater than the thickness of the arch top under axial compression. For different wall thicknesses under axial compression + hydrostatic pressure, use the minimum wall thickness that satisfies the stability condition as the thickness of the first layer of wall panel (bottom layer wall panel) of the storage tank. At the same time, obtain the stress-strain curve of the thickness change of adjacent wall panels through finite element calculation, and obtain that the thickness change between adjacent two layers of wall panels should be 5% - 25% through the stability criterion. Assume that the thickness change of the second-layer wall panel is 5% of the thickness change of the first layer, and use this as the basis. Then change the height of the first-layer wall panel, determine the height of the first-layer wall panel through the stress-strain curve, and then determine the wall thickness of the second layer. The maximum wall thickness change of the second layer is 25% of the wall thickness of the first layer. Similarly, the number of layers of the wall panel can be determined; that is, when the currently calculated wall panel thickness is less than the optimal thickness of the arch top 4, the iteration calculation terminates. Use the wall thickness of the previous wall panel as the optimal thickness of the topmost wall panel of the variable-wall-thickness molten salt storage tank physical model and obtain the number of wall panels of the variable-wall-thickness molten salt storage tank physical model.

[0080] Example 2

[0081] This embodiment provides a specific implementation process of a method for optimizing the design of the wall panels of a variable-wall-thickness molten salt storage tank and a variable-wall-thickness molten salt storage tank. The technical solutions mentioned in this embodiment will be specifically described below with reference to the accompanying drawings:

[0082] As Figure 1 and Figure 2 shown, this embodiment provides a variable-wall-thickness molten salt storage tank, including a tank bottom plate 1, which is a thin-walled circular structure; the wall panel 2 of the tank body adopts a stepped wall panel, and each layer adopts a variable-wall-thickness design. The bottom layer wall panel is the thickest, and the topmost wall is covered with an arch top structure 3; a wind-resistant ring 4 is sleeved on the wall panel 2 axially; the wind-resistant ring 4 is composed of two circular wall panels to reinforce the wall panel 2. The arch top structure 3 includes radial beams 5, circumferential beams 6, and diagonal braces 7; the radial beams 5 are composed of 60 HN350×170 H-shaped steels, equally spaced along the spherical circumference; the circumferential beams 6 are also composed of 11 HN350×170 H-shaped steels; the diagonal braces 7 are composed of 4 groups of HN250×125 H-shaped steels.

[0083] This variable-wall-thickness molten salt storage tank is designed by using the following optimized design method for the variable-wall-thickness molten salt storage tank wall panels.

[0084] This embodiment also provides an optimized design method for the variable-wall-thickness molten salt storage tank wall panels, which is as follows:

[0085] First, a physical model of the variable-wall-thickness molten salt storage tank is constructed according to the actual storage tank dimensions, and the wall thickness and height of each layer are optimized in the physical model of the variable-wall-thickness molten salt storage tank, and the number of layers of the final wall panels is determined.

[0086] As Figure 3 shown, specifically as Figure 3 shown in Figures (a), (b), and (c) therein, the relationship curves of the maximum deformation and the maximum stress under different vault thicknesses. It can be obtained from Figure (a) that when the vault thickness is less than 14 mm, the stress-strain curve shows a non-linear change, that is, the stress change is very small and the deformation change is very large. When the vault thickness is greater than 14 mm, the maximum deformation and the maximum stress curve is a straight line, within the elastic range, and the structural stability is good. Therefore, it can be obtained from Figure (a) that the thickness of the vault should be greater than 14 mm, and the designed vault thickness in this embodiment is selected as 14 mm. It can be obtained from the displacement and stress nephograms in Figures (b) and (c) that the maximum deformation occurs at the central position of the vault, and the maximum stress appears at the edge position.

[0087] As Figure 4 shown, it is the stress-strain curve of the equal-wall-thickness storage tank considering the combined action of axial compression and hydrostatic pressure. It can be obtained from the stress-strain curve that when the wall panel thickness is less than 48 mm, the stress-strain curve shows a non-linear change. When the tank wall thickness is greater than or equal to 48 mm, the linearity of the stress-strain curve is good, and the storage tank is within the elastic deformation range and the structure is stable. Therefore, the maximum wall thickness of the variable-wall-thickness storage tank designed in this article is selected as 48 mm.

[0088] Figure 5 shown, it is the stress-strain curve of the adjacent wall thickness change. When the adjacent wall thickness change is 25%, the stress-strain curve shows a non-linear change and does not meet the stability requirements. Therefore, in this embodiment, it is specified that the change in the thickness of adjacent two layers of wall panels is within 5%-25%.

[0089] As Figure 6 shown, it is the stress-strain curve of the first layer of wall panel (i.e., the bottom layer wall panel) at different heights. When the height of the first layer of wall panel changes between 0.05 and 2 m, when the wall panel height is greater than 0.5 m, the stress-strain curve shows a linear change relationship and meets the stability requirements. Therefore, the height of the first layer is determined to be 0.5 m. From Figure 4 it can be obtained that the wall thickness of the first layer is 48 mm, and from Figure 5The change range of the wall thickness of the second layer can be obtained as 5% - 25%, and the change range of the wall thickness of the second layer is 38 mm - 46 mm. At this time, it is assumed that the thickness of the second layer wall panel is 46 mm.

[0090] As Figure 7 shown in the stress-strain curves of different wall thicknesses of the second layer wall panel, the change range of the wall thickness of the second layer wall panel is 38 mm - 46 mm. From Figure 7 the stress-strain curves, it can be obtained that when the thickness of the second layer wall panel is 46 mm, the stress-strain curve is basically linear. Through the stability criterion, it can be obtained that the thickness of the second layer wall panel is 46 mm. At this time, the change range of the thickness of the third layer wall panel is 35 mm - 44 mm, and it is assumed that the wall thickness of the third layer is 44 mm.

[0091] Figure 8 Shown in the stress-strain curves of different heights of the second layer wall panel, when the height of the second layer wall panel changes between 0.05 m and 2 m, from the stress-strain curves, it can be obtained that when the height of the second layer wall panel is greater than or equal to 0.1 m, the stress-strain curve basically satisfies linear change. Therefore, the height of the second layer wall panel is selected as 0.1 m.

[0092] Figure 9 Shown in the stress-strain curves of different wall thicknesses of the third layer wall panel, when the thickness of the third layer wall panel is greater than 41 mm, the stress-strain curve basically satisfies linear relationship. Therefore, the optimal thickness of the third layer wall panel is selected as 41 mm. At this time, the change range of the thickness of the fourth layer wall panel is 31 mm - 39 mm, and it is assumed that the thickness of the fourth layer wall panel is 39 mm.

[0093] Figure 10 Shown in the stress-strain curves of different heights of the third layer wall panel, through the stability criterion, it can be obtained that when the height of the third layer wall panel is greater than or equal to 0.5 m, the stress-strain curve basically satisfies linear relationship. Therefore, the height of the third layer wall panel is determined as 0.5 m.

[0094] Figure 11 Shown in the stress-strain curves of different thicknesses of the fourth layer wall panel, it can be obtained that the stress-strain curves at different thicknesses basically satisfy linear relationship, that is, the minimum wall panel thickness can still meet the stability requirements. Therefore, the thickness of the fourth layer wall panel is determined as 31 mm. At this time, the change range of the thickness of the fifth layer wall panel is 24 mm - 30 mm, and it is assumed that the thickness of the fifth layer wall panel is 30 mm.

[0095] Figure 12 Shown in the stress-strain curves of the height change of the fourth layer wall panel, at different wall panel heights, the stress-strain curve is linear. Therefore, the optimal wall panel height of the fourth layer wall panel is selected as 0.05 m.

[0096] Figure 13As shown, the stress-strain curves of the fifth-layer wall panel under different thicknesses are presented. It can be obtained that the stress-strain curves under different thicknesses basically satisfy the linear relationship. Therefore, the minimum wall thickness is the optimal wall thickness, which is 24 mm. At this time, the change range of the thickness of the sixth-layer wall panel is 18 mm - 23 mm. Assume the thickness of the sixth-layer wall panel is 23 mm.

[0097] Figure 14 As shown, the stress-strain curves of the fifth-layer wall panel at different heights are presented. It can be obtained that the stress-strain curves at different heights basically satisfy the linear relationship. Therefore, the height of the fifth-layer wall panel is selected as 0.05 m.

[0098] Figure 15 As shown, the stress-strain curves of the sixth-layer wall panel under different thicknesses are presented. It can be obtained that the stress-strain curves under different thicknesses basically satisfy the linear relationship. Therefore, the minimum wall thickness is the optimal wall thickness, which is 18 mm. At this time, the change range of the thickness of the seventh-layer wall panel is 14 mm - 17 mm. Assume the thickness of the seventh-layer wall panel is 17 mm.

[0099] Figure 16 As shown, the stress-strain curves of the sixth-layer wall panel at different heights are presented. It can be obtained that the stress-strain curves at different heights basically satisfy the linear relationship. Therefore, the height of the sixth-layer wall panel is selected as 0.05 m.

[0100] Figure 17 As shown, the stress-strain curves of the seventh-layer wall panel under different thicknesses are presented. It can be obtained that the stress-strain curves under different thicknesses basically satisfy the linear relationship. Therefore, the optimal wall thickness of the seventh layer is determined to be 14 mm. Since the thickness of the arch top 4 under axial compression is determined to be 14 mm, the minimum thickness of the tank wall cannot be less than 14 mm. When the thickness of the highest layer is less than 14 mm, to ensure that the design capacity remains unchanged, the height is the design height minus the height of the determined wall panel.

[0101] Here, when calculating the thickness of the eighth-layer wall panel again, since the thickness of the eighth-layer wall panel is less than the thickness of the arch top 4, it cannot meet the requirements of structural stability, and the iteration terminates. Therefore, the wall panel thickness of 14 mm from the previous iteration calculation is used as the optimal thickness of the top-layer wall panel, and it can be confirmed that the number of wall panel layers of this variable-wall-thickness molten salt storage tank physical model is seven.

[0102] Using this variable-wall-thickness molten salt storage tank wall panel optimization design method compared with the variable-point method design, the finite element calculation method meets the stability conditions of the storage tank, and it also reduces the material cost. The tank wall material of a single hot molten salt storage tank is reduced by 165.34 tons, as shown in Table 1 specifically.

[0103] Table 1 is the comparison table of storage tank designs

[0104]

[0105] It can be seen that the advantages of an optimized design method for the wall panels of a variable-wall-thickness molten salt storage tank provided in this embodiment are as follows:

[0106] (A)For the vault structure under axial compression conditions, the optimal vault thickness to meet stability is determined.

[0107] (B)Compared with the thickness of the equal-wall-thickness wall panels, the minimum wall panel thickness to meet stability is determined by this method.

[0108] (C)Compared with the thickness and height of the variable-wall-thickness wall panels, the optimal combination of variable-wall-thickness wall panels to meet stability is determined.

[0109] (D)The design of the variable-wall-thickness storage tank wall panel is reasonable, the structure is simple, and it is easy to implement, and can be widely applied in practical engineering.

[0110] In summary, the present invention provides an optimized design method for the wall panels of a variable-wall-thickness molten salt storage tank. Compared with the existing design methods, it has the following advantages:

[0111] First, this method optimizes the vault thickness and selects the minimum wall thickness that meets the stability requirements under axial compression.

[0112] Second, this method optimizes the thickness of the equal-wall-thickness wall panels and selects the optimal wall thickness that meets the stability requirements under the coupled action of axial compression and hydrostatic pressure, and uses this wall thickness as the maximum thickness of the variable-wall-thickness wall panels.

[0113] Third, this method optimizes the thickness and height of the variable wall panels, conducts stability criteria through stress-strain curves, and obtains a result that not only meets the stability requirements but also saves materials.

[0114] The above embodiments are only one of the implementation manners that can implement the technical solution of the present invention. The scope of protection required by the present invention is not limited only by this embodiment, but also includes any changes, substitutions and other implementation manners that are easily conceivable by any person skilled in the art within the technical scope disclosed by the present invention.

Claims

1. An optimized design method for the wall panel of a molten salt storage tank with variable wall thickness, characterized in that, The steps are as follows: Obtain the optimal thickness of the dome (4) of the variable-wall-thickness molten salt storage tank physical model based on the finite element calculation method; wherein, the variable-wall-thickness molten salt storage tank physical model is constructed from the actual storage tank dimensions; Based on the stress-strain curve of the single-layer wall panel of the variable-wall-thickness molten salt storage tank physical model under the combined action of axial compression and hydrostatic pressure, obtain the optimal thickness of the single-layer wall panel, and use the optimal thickness of the single-layer wall panel as the optimal thickness of the bottom wall panel; Based on the optimal thickness of the bottom wall panel and the thickness change range of adjacent two layers of wall panels, iteratively calculate the optimal thickness and optimal height of each layer of wall panel from bottom to top until the currently calculated wall panel thickness is less than the optimal thickness of the dome (4); use the wall panel thickness of the previous iteration before the iteration calculation ends as the optimal thickness of the top wall panel of the variable-wall-thickness molten salt storage tank physical model, and simultaneously obtain the number of wall panels of the variable-wall-thickness molten salt storage tank physical model; The specific steps of iteratively calculating the optimal thickness and optimal height of each layer of wall panel from bottom to top based on the optimal thickness of the bottom wall panel and the thickness change range of adjacent two layers of wall panels are as follows: S1: Obtain the preliminary wall thickness of the second layer of wall panel according to the optimal thickness of the bottom wall panel and the thickness change range of adjacent two layers of wall panels; S2: According to the preliminary wall thickness of the second layer of wall panel and the optimal thickness of the bottom wall panel, obtain the stress-strain curve of the bottom wall panel at different heights, and use the minimum height that satisfies stability as the optimal height of the bottom wall panel; S3: According to the stress-strain curve of the thickness of the second layer of wall panel, use the minimum thickness that satisfies stability as the optimal thickness of the second layer of wall panel; S4: Iteratively calculate the optimal thickness and optimal height of each layer of wall panel layer by layer until the currently calculated wall panel thickness is less than the optimal thickness of the dome (4), and use the wall panel thickness of the previous iteration before the iteration calculation ends as the optimal thickness of the top wall panel of the variable-wall-thickness molten salt storage tank physical model and obtain the number of wall panels of the variable-wall-thickness molten salt storage tank physical model.

2. The optimized design method for the wall panel of a molten salt storage tank with variable wall thickness according to claim 1, wherein The variable-wall-thickness molten salt storage tank physical model includes a dome (4), multiple layers of variable-wall-thickness wall panels (2) and a bottom plate (1); the material of the variable-wall-thickness molten salt storage tank physical model is stainless steel 347H; during the modeling process of the variable-wall-thickness molten salt storage tank physical model, the influence of the change in dome thickness, wall panel thickness and wall panel height on the overall mechanical properties of the storage tank is considered, and the gravity of the storage tank, the axial pressure received by the storage tank dome and the hydrostatic pressure received by the working medium in the storage tank are used as the boundary conditions of the variable-wall-thickness molten salt storage tank physical model.

3. The optimized design method of the variable wall thickness molten salt storage tank wall panel according to claim 1, wherein The specific steps of obtaining the optimal thickness of the dome (4) of the variable-wall-thickness molten salt storage tank physical model based on the finite element calculation method are as follows: Calculate the dome (4) of the variable-wall-thickness molten salt storage tank physical model based on the finite element calculation method to obtain the corresponding stress-strain curve of the dome (4); According to the corresponding stress-strain curve of the dome (4), obtain the optimal thickness of the dome (4) under axial compression through structural stability judgment; Among them, the judgment basis for structural stability is as follows: when the stress-strain curve shows a linear change, it indicates that the structure is in elastic deformation and has relatively high stability; when the stress-strain curve shows a non-linear change, it means that the structure is in the plastic damage stage and has relatively poor stability; the thickness of the crown (4) at the minimum thickness within the range of elastic deformation of the structure is taken as the optimal thickness of the crown (4).

4. The optimized design method for the wall panels of a molten salt storage tank with variable wall thickness according to claim 1, wherein The specific steps for obtaining the optimal thickness of the single-layer wall panel based on the stress-strain curve of the single-layer wall panel of the variable-wall-thickness molten salt storage tank under the combined action of axial compression and hydrostatic pressure are as follows: Regard the variable-wall-thickness molten salt storage tank in the physical model of the variable-wall-thickness molten salt storage tank as an equal-wall-thickness molten salt storage tank; Combined with the finite element calculation method, obtain the stress-strain curve of the single-layer wall panel of the equal-wall-thickness molten salt storage tank under the combined action of axial compression and hydrostatic pressure; According to the stress-strain curve of the single-layer wall panel under the combined action of axial compression and hydrostatic pressure, obtain the minimum wall thickness that satisfies the stability when the single-layer wall thickness is used, and take the minimum wall thickness that satisfies the stability when the single-layer wall thickness is used as the optimal thickness of the single-layer wall panel.

5. The optimized design method of the wall panel of the variable-wall-thickness molten salt storage tank according to claim 1, characterized in that, The optimal height of the top wall panel is calculated based on the preset total height of the wall panel and the optimal heights of each layer of wall panels. The specific formula is as follows: Optimal height of the top wall panel = Preset total height of the wall panel - Sum of the optimal heights of each layer of wall panels.

6. The optimized design method for the wall panel of a molten salt storage tank with variable wall thickness according to claim 1, characterized in that The thickness change range between adjacent two layers of wall panels is 5% - 25%.

7. A molten salt storage tank with variable wall thickness, characterized in that, The variable-wall-thickness molten salt storage tank includes multiple layers of variable-wall-thickness wall panels (2) and is designed by using the variable-wall-thickness molten salt storage tank wall panel optimization design method described in claims 1 - 6.

8. The variable-wall-thickness molten salt storage tank according to claim 7, wherein It includes a tank body surrounded by multiple layers of variable-wall-thickness wall panels (2); a bottom plate (1) is provided at the bottom of the tank body, and a crown (4) is covered on the top; a wind girder (3) is sleeved on the tank body axially.

9. The variable-wall-thickness molten salt storage tank according to claim 8, characterized in that, The crown (4) includes radial beams (5), circumferential beams (6) and diagonal braces (7); among them, the radial beams (5) and the circumferential beams (6) adopt H-shaped steel of HN350×170; the diagonal braces (7) adopt H-shaped steel of HN250×125.

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