A Design Method for Cryogenic High-Pressure Hydrogen Storage Cylinders

Abstract

The present invention discloses a design method for cryogenic high-pressure hydrogen storage cylinders, which includes: obtaining the service condition parameters of cryogenic high-pressure hydrogen storage cylinders according to the filling final state, hydrogen supply control, cylinder body structure and heat transfer model equations; calculating the target parameter domain of the laminate under low temperature, checking the mechanical properties of the existing laminate, and constructing a composite material performance database for the design of cryogenic high-pressure hydrogen storage cylinders; performing mechanical analysis on the winding layer; according to the results of the mechanical analysis of the winding layer, carrying out optimization design of the winding layup to obtain the optimal winding process parameters. The present invention realizes the reliability design of hydrogen storage cylinders under the dual extreme working conditions of cryogenic and high pressure, will provide a new design method for the development of on-vehicle cryogenic high-pressure hydrogen storage equipment, promote the demonstration application of cryogenic high-pressure hydrogen storage technology on heavy-duty transportation equipment, and has important theoretical value and application prospects for assisting the "dual carbon" development goal and upgrading green transportation equipment.

Description

Technical Field

[0001] The present invention belongs to the field of liquid hydrogen storage, and particularly relates to a design method for a cryogenic high-pressure hydrogen storage cylinder. Background Art

[0002] Efficient and safe on-vehicle hydrogen storage technology is the focus of attention in transportation equipment. Cryogenic high-pressure hydrogen, with outstanding hydrogen storage efficiency and safety, has become the optimal solution for transportation equipment to use clean energy. Cryogenic high-pressure hydrogen storage refers to storing hydrogen in a supercritical state in an adiabatic and pressure-resistant cylinder under low temperature (20 - 50K) and high pressure (35MPa) composite conditions. Compared with on-vehicle liquid hydrogen, it has significant advantages such as long lossless maintenance time, fast filling speed, and high pressure resistance performance, and can solve the difficulties faced in current on-vehicle liquid hydrogen research, such as high heat leakage evaporation rate, large filling loss, and low hydrogen supply pressure. However, the combined action of two extreme conditions of cryogenic and high pressure poses extremely high requirements for the material properties, structural design, and test conditions of the hydrogen storage cylinder, which is the current forefront hot spot in the field of on-vehicle hydrogen storage equipment. Summary of the Invention

[0003] In view of the defects or deficiencies in the prior art, it is desirable to provide a design method for a cryogenic high-pressure hydrogen storage cylinder. By establishing a thermodynamic lumped parameter model to predict the whole process conditions of cryogenic high-pressure hydrogen storage and hydrogen supply, the boundary loads for the cylinder design are obtained, and through the mechanical analysis of the composite material layer and the optimized design of the winding layer, the optimal design scheme for the cryogenic high-pressure hydrogen storage cylinder is obtained.

[0004] The technical solution adopted by the present invention to achieve the above object is as follows:

[0005] A design method for a cryogenic high-pressure hydrogen storage cylinder, characterized by comprising the following steps:

[0006] Step 1: Obtain the service condition parameters of the cryogenic high-pressure hydrogen storage cylinder according to the filling final state, hydrogen supply control, cylinder structure, and heat transfer model equation;

[0007] Step 2: Calculate the target parameter domain suffered by the laminate at low temperature according to the service condition parameters of the cryogenic high-pressure hydrogen storage cylinder obtained in Step 1; check the mechanical properties of the existing laminate according to the calculated target parameter domain. If the requirements are met, it is used for manufacturing the cryogenic high-pressure hydrogen storage cylinder. If the requirements are not met, modify the composite material properties of the laminate according to the calculation results to meet the requirements; test the mechanical properties of the modified laminate, and the test results are used to construct a composite material property database for the design of the cryogenic high-pressure hydrogen storage cylinder;

[0008] Step 3: Perform mechanical analysis on the winding layer according to the constructed composite material property database for the design of the cryogenic high-pressure hydrogen storage cylinder; perform optimized design of the winding layup according to the results of the mechanical analysis of the winding layer to obtain the optimal winding process parameters.

[0009] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0010] The design method of cryogenic high-pressure hydrogen storage cylinders proposed by the present invention comprehensively considers the influence of the dual extreme environments of cryogenic and high pressure on the cylinders, uses the boundary conditions predicted by the service conditions to guide the design of the composite material layer of the cylinders, conducts modification treatment and optimization design on the composite material layer, introduces the influence of low temperature on the stress of the composite material, and constructs a new mechanical model of fiber-reinforced composite materials in a cryogenic environment, making the design steps of cryogenic high-pressure hydrogen storage cylinders more perfect and the design calculation results more accurate. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Other features, objects, and advantages of the present application will become more apparent by reading the detailed description of the non-limiting embodiments with reference to the following drawings:

[0012] Figure 1 It is a flowchart of a design method for a cryogenic high-pressure hydrogen storage cylinder of the present invention;

[0013] Figure 2 It is an axial and circumferential stress balance diagram of a design method for a cryogenic high-pressure hydrogen storage cylinder of the present invention;

[0014] Figure 3 It is a circumferential winding and helical winding line type diagram of a design method for a cryogenic high-pressure hydrogen storage cylinder of the present invention;

[0015] Figure 4 It is the distribution of stress and strain on the wall thickness under three ply stacking methods (Type A, Type B, and Type C) of a design method for a cryogenic high-pressure hydrogen storage cylinder of the present invention, where (a) is the circumferential stress diagram corresponding to each layer under the three ply stacking methods; (b) is the axial stress diagram corresponding to each layer under the three ply stacking methods; (c) is the shear stress diagram corresponding to each layer under the three ply stacking methods; (d) is the radial stress and radial displacement diagram corresponding to each layer under the three ply stacking methods;

[0016] Figure 5 It is the distribution of the failure judgment coefficient and circumferential / axial stress of a design method for a cryogenic high-pressure hydrogen storage cylinder of the present invention; where (a) is the Tsai-Wu failure criterion coefficient diagram corresponding to different helical winding angles; (b) is the circumferential and axial stress diagram corresponding to different helical winding angles. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0017] The following further describes the present application in detail with reference to the drawings and embodiments. It can be understood that the specific embodiments described herein are only used to explain the relevant invention and are not intended to limit the invention. Additionally, it should be noted that only the parts related to the invention are shown in the drawings for the sake of convenience of description.

[0018] It should be noted that, without conflict, the embodiments in the present application and the features in the embodiments can be combined with each other. The following will describe the present application in detail with reference to the drawings and in combination with the embodiments.

[0019] Please refer to Figure 1 , a cryogenic high-pressure hydrogen storage cylinder design method, which includes four steps, specifically theoretical modeling of the hydrogen storage and supply process, composite material design, fiber winding design, and modeling verification.

[0020] Step 1: Theoretical modeling of the hydrogen storage and supply process: According to the established theoretical model of the hydrogen storage and supply process, the service condition parameters of the cryogenic high-pressure hydrogen storage cylinder are obtained.

[0021] The specific steps include:

[0022] 11. Considering the effects of throttling effect, cylinder structure, and insulation layer, construct a heat transfer model for the cryogenic high-pressure hydrogen storage cylinder;

[0023]

[0024] Among them, is the heat input term in the energy conservation equation; is the heat output term in the energy conservation equation; m s is the saturated hydrogen mass; C s is the saturated hydrogen energy density; ΔT is the temperature difference; m is the mass of hydrogen stored in the cylinder; U is the internal energy of hydrogen; h is the enthalpy value; t is the time.

[0025] In the cylinder heat transfer model, considering the vacuum insulation layer between the cylinder and the outer shell and the heat leakage law of the support structure, combined with the auxiliary heating power required for the gas-phase hydrogen supply process, form the heat input term According to the cryogenic insulation requirements of the cylinder, optimize the hydrogen supply temperature and determine the throttling refrigeration capacity to form the heat output term Establish a system heat transfer model.

[0026] 12. According to the cylinder heat transfer model, construct a lumped parameter model for the cylinder hydrogen supply process;

[0027]

[0028]

[0029] In the formula, h is the enthalpy value, P is the internal pressure received by the cylinder, t is the time, T is the liquid hydrogen temperature in the cylinder, and ρ is the mass density.

[0030] A thermodynamic transient model consisting of multiple equilibrium states is established based on the differential concept, namely the lumped parameter model. Using the hydrogen supply mass flow as the system mass source term, the transient temperature and pressure of the system are calculated by using the enthalpy value and the density (mass) change rate. The mass distribution of each phase state in the gas-liquid-supercritical multiphase flow model is determined by the saturation state curve in the range of 20 - 293K and 0.1 - 20MPa. Taking the mass conservation equation as the judgment basis for iterative calculation, the mass transfer result of multiphase flow is determined, and a lumped parameter thermodynamic model describing the cryogenic high-pressure hydrogen storage and supply process is formed.

[0031] 13. Derive the mass transfer model of the cryogenic high-pressure hydrogen storage cylinder based on the force balance of the composite material layer of the cylinder in the lumped parameter model;

[0032]

[0033]

[0034] In the formula, P is the internal pressure of the cylinder, t is the time, T is the temperature of liquid hydrogen in the cylinder, σ is the stress on the composite material layer, T′ is the temperature of the composite material layer, and Φ and Ψ are the equation correction coefficients.

[0035] 14. According to the mass transfer model of the cryogenic high-pressure hydrogen storage cylinder, output the service conditions of the cryogenic high-pressure hydrogen storage cylinder, and the service conditions include pressure, temperature, etc.

[0036]

[0037]

[0038] In the formula, P is the internal pressure of the cylinder, t is the time, T is the temperature of liquid hydrogen in the cylinder, σ is the stress on the composite material layer, T′ is the temperature of the composite material layer, and Φ and Ψ are the equation correction coefficients. Step 2: Composite material design: According to the service condition parameters of the cryogenic high-pressure hydrogen storage cylinder obtained in Step 1, calculate the target parameter domains such as the stress and deformation of the laminate at low temperature; according to the calculated target parameter domains, check the mechanical properties of the existing laminate. If the requirements are met, it is used for the manufacture of the cryogenic high-pressure hydrogen storage cylinder. If the requirements are not met, the composite material properties of the laminate are modified according to the calculation results to meet the requirements; test the mechanical properties of the modified laminate, and the test results are used to construct a composite material property database for the design of the cryogenic high-pressure hydrogen storage cylinder.

[0039] The specific steps include:

[0040] 21. According to the service condition parameters of the cryogenic high-pressure hydrogen storage cylinder obtained in Step 1, calculate the target parameter domains of the stress and deformation of the laminate at low temperature;

[0041] 22. Check the mechanical properties of the existing laminate according to the calculated target parameter domain.

[0042] The target parameter domain is obtained according to the service conditions. For example, during service, the tensile stress on the composite layer of the gas cylinder is 1500 - 2000 MPa, and the tensile strength of the existing laminate is 1300 or 1700 MPa. If the tensile strength of the laminate is less than the maximum value of the target parameter domain (<2000 MPa), it means that the material limit will be exceeded during use, there is a possibility of failure, and it does not meet the use requirements, so modification treatment is needed.

[0043] The modification methods include fiber modification and resin modification. Fiber modification uses surface oxidation, plasma treatment or chemical deposition to form grooves or protrusions on the fiber surface and increase the surface roughness of the fiber; resin modification is achieved by adding organic modifiers and inorganic modifiers to the resin. Organic modifiers include polyethersulfone, polyurethane or polyethylene glycol, etc., and inorganic modifiers include carbon nanotubes, graphene or silica. And a variable temperature test is carried out on the modified resin using an X-ray diffractometer to obtain the low-temperature thermal expansion coefficients of the resin and fibers in different directions.

[0044] 24. Establish a low-temperature mechanical model of the fiber-reinforced resin-based laminate. Then, according to the test results of the thermal expansion coefficients of the resin and fibers, construct a static equilibrium equation to solve the longitudinal and transverse thermal expansion coefficients of the laminate. The solution formula is:

[0045]

[0046] α 2 =v f (1 + μ f )α f + v m (1 + μ m )α m -(μ f v f + μ m v m )α 1

[0047] Among them, α 1 is the longitudinal thermal expansion coefficient of the laminate; α 2 is the transverse thermal expansion coefficient of the laminate; α f1 is the longitudinal thermal expansion coefficient of the fibers in the laminate; α m is the thermal expansion coefficient of the resin in the laminate; α f is the thermal expansion coefficient of the fibers in the laminate; E f1 is the longitudinal elastic modulus of the fibers in the laminate; v f1 is the longitudinal volume fraction of the fibers in the laminate; v m is the volume fraction of the resin in the laminate; vf is the volume fraction of fibers in the laminate; μ m is the Poisson's ratio of the resin in the laminate; μ f is the Poisson's ratio of the fibers in the laminate.

[0048] 25. The mechanical properties of the modified laminate are tested. The test results include mechanical property parameters such as the tensile strength, elastic modulus, and compressive strength of the laminate. The test results are used to construct a performance database of composite materials for the design of cryogenic high-pressure hydrogen storage cylinders. During the operation of the cylinder, the operating conditions will change. For example, the internal pressure fluctuates between 30 - 35 MPa, corresponding to stresses of 1000 - 1200 Mpa and x - y strains generated inside the composite material. These are the target parameter domains, and through material modification, it is hoped that the material can meet this region. For example, in this process, it is required that the tensile strength is at least greater than 1200 MPa.

[0049] The third step: Fiber winding design: Based on the laminate design, introduce the temperature load term caused by cryogenic conditions into the fiber winding theory, construct the static equilibrium equation of anisotropic composite materials, determine the basic dimensions of the cryogenic high-pressure hydrogen storage cylinder, and then calculate the stresses and strains at each point and in each direction of the fiber winding layer, and optimize and improve the winding process.

[0050] 31. Thermodynamic modeling of the fiber winding layer of the container and its external thermal insulation structure: The temperature on the surface of the composite material is determined by the performance of multiple layers of vacuum insulation materials, which is mainly calculated by heat convection and heat radiation. The temperature near the carbon fiber composite material layer is actually very low, and its heat transfer form is mainly heat conduction. The heat conduction calculation formula for the fiber composite layer is:

[0051] dQ c +dQ g =dQ

[0052] where dQ c represents the net heat input into the microelement in the form of heat conduction, dQ g represents the heat generated by the heat source in the microelement, and dQ represents the increment of the internal energy in the microelement, where:

[0053]

[0054] where x, y, z are the spatial coordinate directions; q is the heat, and t is the time.

[0055] According to Fourier's law:

[0056]

[0057] where λ is the heat transfer coefficient; T is the ambient temperature.

[0058] dQ can be further written asc Cheng:

[0059]

[0060] Meanwhile, the heat generated by the heat source in the infinitesimal element per unit time can be expressed as:

[0061] dQ g = q V dxdydzdt

[0062] where q V is the heat per unit volume, and t refers to time.

[0063] The increment of internal energy in the infinitesimal element per unit time per unit area is:

[0064]

[0065] where ρ is a constant, u refers to momentum, and c is the energy density.

[0066] By combining the above equations, we can obtain:

[0067]

[0068] Let Substituting the above into the equation, we get:

[0069]

[0070] When written in cylindrical coordinate form, the equation can be expressed as:

[0071]

[0072] where r is any radius from the inner wall to the outer wall, r 0 <r<r a , is the helical winding angle.

[0073] Therefore, the heat conduction control equation of the cryogenic high-pressure hydrogen storage container in the cylindrical coordinate system can be written as:

[0074]

[0075] where, represents the rate of internal energy generation, k represents the thermal conductivity, ξ represents the thermal diffusivity, and its physical meaning is to describe the thermal inertia of an object. The larger the thermal diffusivity, the smaller the thermal inertia, and the faster the object reaches the thermal equilibrium state with the surrounding environment.

[0076] Due to the long, axisymmetric, and steady-state conditions of the pipeline, in the case of no heat generation, the temperature distribution in the pipeline is only a function of the radius. The heat conduction control equation can be simplified to:

[0077]

[0078] It is expressed in integral form as:

[0079] T = A + Blnr

[0080] Where A and B are integration constants.

[0081] The outer surface is exposed to free convection at the ambient temperature T, and the inner surface is exposed to forced convection of the hot fluid at the inner wall temperature T f Under. According to the convective heat transfer equation, the heat transfer equations at the two boundaries can be listed as:

[0082]

[0083] Where T is the ambient temperature, T f Is the inner wall temperature of the gas cylinder, T ∞ Is the external temperature of the gas cylinder, h 0 , h a Are the average convective heat transfer coefficients of the inner and outer surfaces of the composite material layer respectively, k represents the thermal conductivity, r 0 And r a Represent the inner and outer radii of the cryogenic high-pressure hydrogen storage gas cylinder respectively; the integration constants A and B can be obtained using the above boundary conditions.

[0084] The internal temperature is set to T f , Using cryogenic high-pressure hydrogen at 20K, the external temperature T ∞ Is the temperature of the nearest layer of thermal insulation material close to the carbon fiber composite material layer, which is 50K.

[0085] 32. Introduction of the temperature load term into the calculation:

[0086] The carbon fiber is wound in a specific direction in each layer. The internal temperature of the hydrogen storage container is represented by T f , The reference temperature is set to T ref , Which represents the initial temperature of the container, set here to 298K, and the working temperature at any radial position is represented by T(r), so the temperature difference along the radial direction can be expressed as:

[0087] ΔT(r) = T(r) - T ref

[0088] The strain generated on the outer wall of the container is caused by the combined action of the applied internal pressure and the thermal stress caused by the temperature difference, and can be expressed as:

[0089] {ε i} = [S]{σ i} + αΔT(r)

[0090]

[0091]

[0092] Among them, represents the strain matrix in cylindrical coordinates under thermo-mechanical coupling; {ε i} represents the matrix composed of the strain ε i of the i-th layer of fibers in the radial direction of the hydrogen storage container; [S] represents the compliance matrix of the composite material in cylindrical coordinates; {σ i} represents the matrix composed of the stress σ i of the i-th layer of fibers in the radial direction of the hydrogen storage container; α is the coefficient of thermal expansion; ΔT is the temperature difference; d represents the differential symbol; u represents the displacement; represents the stress in the radial direction of the i-th layer; represents the stress in the circumferential direction of the i-th layer; represents the strain in the radial direction of the i-th layer; represents the strain in the circumferential direction of the i-th layer; represents the strain in the radial direction of the i-th layer.

[0093] Use the high-order matrix fast algorithm to solve the above equations:

[0094]

[0095] Among them, a, b, d, k are coefficients; n is the number of fiber winding layers; ε 0 is the axial strain; γ 0 is the shear strain.

[0096] The inner and outer radii of the cryogenic high-pressure hydrogen storage cylinder are represented by r 0 and r a respectively. In addition, the surface temperature of the container is fixed at the ambient temperature T ra . Due to the forced convection of the hydrogen fluid, it is assumed that the inner surface temperature is consistent with the fluid temperature T r0 . According to the heat conduction control equation of the thin-walled cylinder in the cylindrical coordinate system, the temperature distribution along the radius direction on the wall of the hydrogen storage container is as follows:

[0097]

[0098] Among them, h 0 represents the average convective heat transfer coefficient on the outer surface, which is determined by the absolute pressure on the outer surface of the hydrogen storage container and is taken as 0.1653 W / (m 2 ℃) according to the empirical results; h a is the convective heat transfer coefficient on the inner wall surface and is taken as 50 W / (m 2 ℃); k is the thermal conductivity of the composite material.

[0099] 33. Construction of the static equilibrium equation of the composite material:

[0100] As Figure 2 shown in the force condition of the container, the force balance equations of the axial and circumferential internal forces can be listed. The axial balance is expressed as:

[0101]

[0102] The circumferential balance is expressed as:

[0103]

[0104] where P represents the working pressure borne by the container, d is the outer radius of the container, t is the thickness of the winding layer, N l is the axial internal force of the film, N θ is the circumferential internal force of the film, is the spiral winding angle, r i is the radius of the i-th layer. Simplifying the above two equations gives:

[0105] N l = 1 / 2rP, N θ = rP

[0106] N θ = 2N l

[0107] where r is the radius of the container.

[0108] In the design process, a combination of circumferential winding and spiral winding is adopted, as Figure 3 shown. Considering that the liner of the cryogenic high-pressure hydrogen storage bottle bears about 5% of the mechanical load, first calculate the thickness of the spiral and circumferential fibers:

[0109] Decompose the circumferential and spiral fiber stresses into axial and circumferential stresses and superimpose them to obtain the balance equation

[0110]

[0111]

[0112] where α is the spiral winding angle, σ f is the axial tensile force of the fiber, t θ is the thickness of the circumferential winding fiber, is the thickness of the spiral winding fiber.

[0113] Considering the balance formula at the ultimate pressure of the container, at this time the fiber reaches its design stress. Substitute the equations N l = 1 / 2rP, N θ = rP into it to get:

[0114]

[0115] Among them, P m is the ultimate pressure borne by the container, R is the outer radius of the container, and σ d is the design strength of the fiber.

[0116]

[0117] The fiber thickness is obtained by solving:

[0118]

[0119]

[0120] 34. Optimization of winding process

[0121] By using the methods of controlling variables and comparative experiments, the orthogonal experiment method is used to analyze the influence laws of various factors such as fiber winding angle, thickness, tension, and ply arrangement on the strength of the gas cylinder winding layer, and to solve the relationship between the winding angle and the in-plane stress distribution of the composite material under thermo-mechanical coupling. Further, strength failure criteria such as Tsai-Wu, Tsai-Hill, and Hoffman are used to carry out gas cylinder failure prediction, analyze the failure location and failure reasons of the hydrogen storage gas cylinder under extreme working conditions, and according to the failure analysis results, strengthen the dangerous areas and carry out lightweight design for the safe areas.

[0122] Fourth step: Modeling verification

[0123] Furthermore, the design of auxiliary components, three-dimensional modeling and simulation verification of the cryogenic high-pressure hydrogen storage gas cylinder are carried out. Finite element simulation is used to simulate the stress and deformation behaviors between dissimilar materials of aluminum alloy and carbon fiber, define different element properties, reduce the amount of aluminum alloy while ensuring the support strength, and further reduce the mass of the hydrogen storage gas cylinder. Secondly, the interfacial adhesion force and load distribution of the aluminum alloy-carbon fiber double-layer structure are tested, and the prestress to be applied during carbon fiber winding is determined in combination with the thermal expansion coefficients of the two materials to reduce the thermal stress generated between them due to low temperature. The adiabatic layer adopts the method of high-vacuum variable-density multi-layer insulation. A larger layer density is used on the high-temperature side where radiative heat flux dominates to reduce radiative heat transfer, while a smaller layer density is used on the low-temperature side to reduce solid material heat conduction, optimizing the overall performance of the multi-layer insulation material. A special support structure for the cryogenic high-pressure hydrogen storage cylinder is designed. The support structure is designed in a spiral shape to increase the heat conduction length, reduce the volume at both ends, thereby reducing the contact area. A flexible contact is adopted between the support structure and the composite material layer, which is beneficial to reducing the stress generated due to the deformation of the hydrogen storage gas cylinder. Further, according to the lightweight design results and winding process parameters, three-dimensional modeling of the body of the cryogenic high-pressure hydrogen storage gas cylinder is carried out, the environmental settings are made in the finite element analysis software according to the service condition parameters, and sample bottle pressure resistance experiments, burst experiments, shaking experiments, etc. are carried out under the said environmental settings.

[0124] Example: The container volume is 141 L, the working pressure of the container is 35 MPa, and the lowest working temperature of the container is 20 K. Correspondingly, the bursting pressure is set to 78.75 MPa, which is 2.25 times the working pressure. A 1 / 2 standard ellipsoidal head is adopted, and the aspect ratio of the container is set to 4.8. The radius can be derived from the volume of the container. Its length and diameter are calculated to be 1568 mm and 410 mm respectively.

[0125] To obtain the circumferential winding angle, 5% of the container diameter is selected as the width of the carbon fiber winding tape:

[0126]

[0127] where α hoop is the circumferential winding angle, and d w is the width of the carbon fiber winding tape.

[0128] Before starting the stress analysis, the grid theory is used to determine the thickness of the required fiber layer wall thickness and use it as the initial value of the cyclic calculation. The thicknesses in the circumferential and helical directions are as follows:

[0129]

[0130]

[0131] where k represents the proportion of the mechanical load borne by the composite material (less than 95%), R is the inner radius of the container, P m is the minimum bursting pressure, v f is the fiber volume fraction, σ d is the design pressure of the carbon fiber (i.e., the tensile strength of the fiber), is the helical winding angle, and here 5° is selected.

[0132] The Halpin-Tsai method is selected to predict the elastic mechanical properties of the composite material. The elastic properties of the carbon fiber are constant in the temperature range of 20 - 293 K, and the elastic modulus of the epoxy resin matrix varies linearly from room temperature (3.6 GPa) to 20 K (8.2 GPa). The fiber volume ratio of the T300 / 914 carbon fiber / resin composite material is 0.57.

[0133] Substituting the above parameters, the number of composite material layers in the example is:

[0134]

[0135]

[0136] According to the failure analysis calculation formula, it can be known that the cryogenic high-pressure hydrogen storage container in the embodiment will fail when using a 58-layer structure. When the number of layers increases to 75 layers, the design conditions can be met.

[0137] Furthermore, the winding layer and winding direction are analyzed, and a total of three winding structures are designed. Type A uses the same winding angle every 25 layers, and each layer includes two winding layers with the same positive and negative angles relative to the axis of the cylinder. Type B forms a cycle every 3 layers, and the ratio of the helical winding layer to the circumferential winding layer in these two winding methods is 1:2. Type C makes corresponding adjustments to the number of layers on the basis of Type A, and uses the same winding angle every 26 layers. Figure 4 The stress and displacement of the cryogenic high-pressure hydrogen storage containers with three different layup sequences are shown. The stress ranges received by the hydrogen storage containers formed by the three layup sequences are the same, but the distributions are different. Figure 4 (a) It can be seen that for Type C, the circumferential stress is smaller in the 26-49 layer, and the part with smaller stress occurs in the helical winding part. From Figure 4 (b) It can be seen that the middle layer of Type C bears a large axial stress, which also occurs in the helical winding part. If the helical winding and circumferential winding bear more axial stress and circumferential stress respectively, the strength of the carbon fiber will be fully utilized. From Figure 4 (d) It can be seen that the radial displacement of Type C is reduced by about 5.27-6.29% compared with that of Type A.

[0138] In this embodiment, the Type A winding method is always the first choice. However, at the 30th layer, the Tsai-Wu failure judgment coefficient of Type A exceeds 1. Therefore, in this embodiment, the number of layers in the Type A winding method is simply adjusted to Type C. At this time, the Tsai-Wu failure judgment coefficient of Type C is enveloped between A and B, and the stability is relatively high. When Type C is selected, the Tsai-Wu failure judgment coefficient is less than 1, which can ensure the strength of the container.

[0139] Furthermore, the design results of the embodiment are optimized. In the embodiment, the angle of the helical winding is constantly changing. The maximum value of the Tsai-Wu failure judgment coefficient at each angle of each layer is selected, and a trend diagram of the Tsai-Wu failure judgment coefficient changing with the winding angle is drawn, as Figure 5 shown. Figure 5(a), the Tsai-Wu failure judgment coefficient increases with the increase of the longitudinal winding angle. This value is less than 1 within the angle range of 0-14°, meeting the container design requirements. Therefore, the helical winding angle should be selected within the range of 0-14°. In the subsequent calculations, the helical winding angle is selected as 5°, and the corresponding Tsai-Wu failure judgment coefficient is 0.984. As the helical winding angle increases, the Tsai-Wu failure judgment coefficient increases rapidly. When it is completely circumferentially wound, the axial stress of the container is borne by the direction perpendicular to the carbon fiber. At this time, the load-bearing capacity of the container is the weakest. Figure 5 (b) shows the curves of the axial stress and circumferential stress on the outermost layer of carbon fiber varying with the angle. Within the range of 0-14°, the difference between the outermost axial stress and circumferential stress is the most significant. When the circumferential winding angle is 89°, the circumferential stress is mainly borne by the carbon fiber direction, while the axial stress is mainly borne by the direction perpendicular to the carbon fiber. Therefore, the range of 0-14° with a smaller axial stress should be preferentially selected in the container design. Finally, the optimized winding angle selected in this embodiment is 5°.

Claims

1. A design method for cryogenic high-pressure hydrogen storage cylinders, characterized in that, it includes the following steps: Step 1: Obtain the service condition parameters of the cryogenic high-pressure hydrogen storage cylinder according to the filling final state, hydrogen supply control, cylinder structure and heat transfer model equation; Step 2: According to the service condition parameters of the cryogenic high-pressure hydrogen storage cylinder obtained in Step 1, calculate the target parameter domain that the laminate is subjected to at low temperature; according to the calculated target parameter domain, check the mechanical properties of the existing laminate. If the requirements are met, it is used for the manufacture of the cryogenic high-pressure hydrogen storage cylinder. If the requirements are not met, modify the composite material properties of the laminate according to the calculation results to meet the requirements; test the mechanical properties of the modified laminate, and the test results are used to construct a composite material property database for the design of the cryogenic high-pressure hydrogen storage cylinder; Step 3: According to the constructed composite material property database for the design of the cryogenic high-pressure hydrogen storage cylinder, conduct a mechanical analysis of the winding layer; According to the results of the mechanical analysis of the winding layer, conduct an optimized design of the winding ply to obtain the optimal winding process parameters; Step 1, obtain the service condition parameters of the cryogenic high-pressure hydrogen storage cylinder according to the throttling effect, cylinder structure and energy conservation equation, including: Construct a heat transfer model of the cryogenic high-pressure hydrogen storage cylinder according to the throttling effect, cylinder structure and insulation layer; Taking the filling final state as the initial condition, construct a lumped parameter model of the hydrogen supply process of the cryogenic high-pressure hydrogen storage cylinder according to the energy conservation equation and the constructed heat transfer model; Derive a mass transfer model of the cryogenic high-pressure hydrogen storage cylinder according to the lumped parameter model; According to the mass transfer model of the cryogenic high-pressure hydrogen storage cylinder, output the service conditions of the cryogenic high-pressure hydrogen storage cylinder, and the service conditions include pressure and temperature; In Step 1, the heat transfer model equation is: Among them, is the heat input term in the energy conservation equation; is the heat output term in the energy conservation equation; m s is the mass of saturated hydrogen; C s is the energy density of saturated hydrogen; ΔT is the temperature difference; m is the mass of hydrogen stored in the bottle; U is the internal energy of hydrogen; h is the enthalpy value; In Step 2, the modification of the composite material properties is divided into fiber modification and resin modification; for fiber modification, surface oxidation, plasma treatment or chemical deposition is used to form grooves or protrusions on the fiber surface to increase the surface roughness of the fiber; for resin modification, organic modifiers and inorganic modifiers are added to the resin. The organic modifiers include polyethersulfone, polyurethane or polyethylene glycol, and the inorganic modifiers include carbon nanotubes, graphene or silica; Test the thermal expansion coefficients of the modified fiber and the modified resin. The calculation formula for the thermal expansion coefficient of the modified composite material is: α 2 = v f (1 + μ f )α f + v m (1 + μ m )α m -(μ f v f + μ m v m )α 1 Among them, α 1 is the longitudinal thermal expansion coefficient of the laminate; α 2 is the transverse thermal expansion coefficient of the laminate; α f1 is the longitudinal thermal expansion coefficient of the fibers in the laminate; α m is the thermal expansion coefficient of the resin in the laminate; α f is the thermal expansion coefficient of the fibers in the laminate; E f1 is the longitudinal elastic modulus of the fibers in the laminate; v f1 is the longitudinal volume fraction of the fibers in the laminate; v m is the volume fraction of the resin in the laminate; v f is the volume fraction of the fibers in the laminate; μ m is the Poisson's ratio of the resin in the laminate; μ f is the Poisson's ratio of the fibers in the laminate.

2. A design method for a cryogenic high-pressure hydrogen storage cylinder according to claim 1, characterized in that, in Step 3, the mechanical analysis of the winding layer includes: Calculate the working temperature at any radial position according to the heat conduction control equation, where the heat conduction control equation is: T(r) = A + Blnr where r is any radius from the inner wall to the outer wall of the gas cylinder, r 0 < r < r a ; T(r) is the temperature of the wall surface at a radius of r; A and B are integration constants; Determine the temperature difference along the radial direction: ΔT(r) = T(r) - T ref where ΔT(r) is the temperature difference along the radial direction; T ref is the reference temperature, which is the room temperature; Determine the strain generated on the outer wall of the container: {ε i} = [S]{σ i} + αΔT(r) Among them, {ε i} represents the matrix composed of the strain ε i of the i-th layer of fibers in the radial direction of the hydrogen storage container; [S] represents the compliance matrix of the composite material in cylindrical coordinates; {σ i} represents the matrix composed of the stress σ i of the i-th layer of fibers in the radial direction of the hydrogen storage container; α is the coefficient of thermal expansion; According to the results of the mechanical analysis of the winding layer, conduct an optimized design of the winding ply to obtain the optimal winding process parameters, including: Calculate the thicknesses of the helical and circumferential fibers according to the force condition of the container; where t θ is the thickness of the circumferentially wound fibers; is the thickness of the helically wound fibers; P m is the ultimate pressure that the container can withstand; R is the outer radius of the container; σ d is the design strength of the fibers; θ is the angle of the helical winding.

3. A design method for a cryogenic high-pressure hydrogen storage cylinder according to claim 2, characterized in that, the working temperature T(r) at any radial position is: Among them, h 0 represents the average convective heat transfer coefficient of the outer surface; h a is the convective heat transfer coefficient of the inner wall surface; k is the thermal conductivity of the composite material; r 0 and r a are the inner and outer radii of the hydrogen storage cylinder respectively; T ra and T r0 are the inner and outer temperatures of the hydrogen storage cylinder respectively.

4. A design method for a cryogenic high-pressure hydrogen storage cylinder according to any one of claims 1-3, characterized in that, Step 3 further includes: According to the obtained optimal winding process parameters, a winding layer model is constructed, and a thermo-mechanical coupling failure analysis is carried out on the winding layer model to complete the lightweight bottle body design; The design method of cryogenic high-pressure hydrogen storage cylinders further includes: Step 4: Perform three-dimensional modeling of the bottle body of the cryogenic high-pressure hydrogen storage cylinder according to the lightweight design results and service condition parameters, set the environment in the finite element analysis software according to the service condition parameters, and conduct pressure resistance tests, burst tests and shaking tests on the sample bottle under the set environment.

5. A design method of a cryogenic high-pressure hydrogen storage cylinder according to claim 4, characterized in that, In step 3, the method for completing the lightweight bottle body design by performing a thermo-mechanical coupling failure analysis on the winding layer model includes: Perform a thermo-mechanical coupling failure analysis on the winding layer model to obtain the gas cylinder structure damage mechanism and failure law under the combined action of material-temperature-stress; Then, perform lightweight design of the cryogenic high-pressure hydrogen storage cylinder according to the damage mechanism and failure law; The failure criterion for the thermo-mechanical coupling failure analysis is: Among them, F 11 , F 12 , F 22 , F 33 , F 1 , and F 2 are coefficients; σ 1 is the tensile and compressive stress in the x direction; σ 2 is the tensile and compressive stress in the y direction; τ 12 is the shear strength of the material in the positive axis direction. The calculation method for each coefficient is: Among them, X t and X c represent the tensile strength and compressive strength of the carbon fiber composite material in the fiber direction, Y t and Y c represent the tensile strength and compressive strength of the carbon fiber composite material in the direction perpendicular to the fiber, and S is the shear strength.

6. A design method of a cryogenic high-pressure hydrogen storage cylinder according to claim 4, characterized in that, Step 4 specifically includes: Use finite element simulation to simulate the stress and deformation behavior between dissimilar materials of aluminum alloy and carbon fiber, define different element properties, reduce the amount of aluminum alloy while ensuring the support strength, and further reduce the mass of the hydrogen storage cylinder; Test the interfacial adhesion force and load distribution of the aluminum alloy-carbon fiber double-layer structure, and determine the prestress that needs to be applied during carbon fiber winding in combination with the thermal expansion coefficients of the two materials to reduce the thermal stress generated between the two due to low temperature; The adiabatic layer adopts the method of high-vacuum variable-density multi-layer insulation. A larger layer density is used on the high-temperature side where radiative heat flux dominates to reduce radiative heat transfer, and a smaller layer density is used on the low-temperature side to reduce solid material heat conduction, optimizing the overall performance of the multi-layer insulation material; Design a special support structure for the cryogenic high-pressure hydrogen storage bottle. The support structure is designed in a spiral shape to increase the heat conduction length, reduce the volume at both ends, thereby reducing the contact area. A flexible contact is adopted between the support structure and the composite material layer, which is beneficial to reducing the stress generated due to the deformation of the hydrogen storage cylinder.

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