A method for predicting damage of hydrogen storage cylinders under fire extreme conditions

Abstract

The present application relates to high-pressure hydrogen storage cylinder failure prediction, aiming to provide a kind of fire extreme conditions hydrogen storage cylinder damage prediction method.It includes the following processes: establishing fire condition hydrogen storage cylinder fire scene numerical model;Establish finite element model of hydrogen storage cylinder based on flow-heat-solid multi-physical field coupling;Hydrogen storage cylinder damage state analysis based on maximum stress failure criterion fire process.The present application is realized by associating ANSYS fluid analysis module, thermal analysis module and structural analysis module, flow-heat-solid multi-physical field coupling and hydrogen storage cylinder damage state analysis in fire process, which makes up for the problems of traditional hydrogen storage cylinder fire test, such as high risk, high cost and long time-consuming, and can systematically and efficiently predict the damage state of hydrogen storage cylinder under extreme fire conditions.

Description

Technical Field

[0001] The present invention belongs to the field of failure prediction of high-pressure hydrogen storage cylinders, and particularly relates to a method for predicting the damage of hydrogen storage cylinders under extreme fire conditions. Background Art

[0002] As the most commonly used on-vehicle hydrogen storage method in the field of hydrogen fuel cell vehicles at present, composite hydrogen storage cylinders have broad application prospects. Due to the flammability and explosiveness of hydrogen, during the use of on-vehicle hydrogen storage cylinders, fire accidents caused by hydrogen leakage are likely to occur, and then the cylinders are extremely damaged by fire. To improve the safety of hydrogen storage cylinders, it is necessary to analyze the damage state of the cylinders during the fire process, and predict the fire resistance time and burst pressure of the cylinders, which serves as the evaluation basis for optimizing the design of improving the fire resistance performance of hydrogen storage cylinders.

[0003] At present, the research on the damage of hydrogen storage cylinders under fire conditions mainly focuses on the fire tests of cylinders. [Halm D, et al. Composite pressure vessels for hydrogen storage in fire conditions: Fire tests and burst simulation [J]] Conducted fire tests on 36L hydrogen storage cylinders. By monitoring the thermocouples in the composite material layer of the cylinders, the temperature change law and explosion time of the composite material layer were recorded, so as to obtain the fire resistance performance of the cylinders under different internal pressures. [Kashkarov S, et al. Effect of a heat release rate on reproducibility of fire test for hydrogen storage cylinders [J]] Used cylinders of 36L / 700bar, 72.4L / 350bar and 100L / 700bar, and selected fire source types including premixed methane-air burners, non-premixed propane burners and heptane pool fires to study the influence of cylinder volume, filling pressure and fire source type on the fire resistance limit of the cylinders. [Tamura Y, et al. The residual strength of automotive hydrogen cylinders after exposure to flames [J]] Conducted fire tests on hydrogen storage cylinders without safety relief devices. Before the cylinders were close to leakage or explosion, the fire was stopped and the cylinders were quickly cooled, and the damage state and remaining burst pressure of the cylinders at this time were obtained.

[0004] Existing fire testing methods can accurately determine the damage state and fire resistance performance of hydrogen storage cylinders during fire, but these methods are highly dangerous, costly, and time-consuming. Furthermore, there is a lack of numerical simulation studies on the damage state of hydrogen storage cylinders under fire conditions, and a lack of damage analysis methods based on fluid-thermal-structure interaction (FTH) during cylinder fire processes. Consequently, it is impossible to systematically and efficiently predict the fire resistance time and burst pressure of cylinders. Therefore, proposing a method for predicting the damage of hydrogen storage cylinders under extreme fire conditions has significant engineering application value. Summary of the Invention

[0005] To overcome the shortcomings of existing technologies, this invention provides a method for predicting damage to hydrogen storage cylinders under extreme fire conditions.

[0006] To achieve the objective of this invention, a method for predicting damage to hydrogen storage cylinders under extreme fire conditions is provided, comprising the following steps:

[0007] Step 1: Establish a numerical model of the hydrogen storage cylinder fire scenario under fire conditions, solve the numerical model of the hydrogen storage cylinder fire scenario, and obtain the overall temperature and pressure distribution of the internal and external flow fields of the hydrogen storage cylinder during the fire process.

[0008] Step 2: Establish a finite element model of the gas cylinder based on fluid-thermal-solid multiphysics coupling, and perform mechanical response analysis of the gas cylinder based on the finite element model to calculate the maximum stress in the fiber direction of the hydrogen storage cylinder during the fire process.

[0009] Step 3: Analyze the damage state of the hydrogen storage cylinder during the fire process based on the maximum stress failure criterion to obtain the cylinder fire resistance time and cylinder burst pressure.

[0010] Preferably, step 1 specifically includes the following steps:

[0011] Step 1.1: Based on the ANSYS fluid analysis module, establish a geometric model of the gas cylinder fire scene containing the solid domain of the hydrogen storage cylinder and the fluid domain inside and outside the cylinder, and perform mesh generation;

[0012] Step 1.2: Define material properties, establish turbulence model, combustion model and radiation model of gas cylinder fire process, and set solution method, boundary conditions and initialization conditions;

[0013] Step 1.3: Solve the established numerical model to obtain the overall temperature and pressure distribution of the flow field inside and outside the gas cylinder during the combustion process.

[0014] Preferably, in step 1.1, a geometric model can also be created using 3D modeling software.

[0015] Preferably, step 1.2 includes the following sub-steps:

[0016] Step 1.2.1: Define material properties, including the thermophysical parameters of the fuel-air mixture, the gas inside the cylinder, and the solid materials of the cylinder;

[0017] Step 1.2.2: Establish a Realizable k-ε turbulence model, introduce an enhanced wall function for near-wall treatment, and consider pressure gradient and thermal effects; perform curvature correction on the turbulence model and consider the influence of buoyancy effects.

[0018] Step 1.2.3: Establish the Eddy-Dissipation combustion model

[0019] Step 1.2.4: Establish the DO radiation model;

[0020] Step 1.2.5: Set the solution method to SIMPLE algorithm, use a second-order scheme for pressure, and use a first-order upwind scheme for density, momentum, turbulent kinetic energy, turbulent dissipation rate, material composition, energy, and radiation; boundary conditions include inlet fuel velocity and temperature, outlet pressure and temperature, boundary material composition mass fraction, and ground temperature; initialization conditions include initial component mass fraction, initial ambient temperature, and initial pressure inside the gas cylinder.

[0021] Preferably, the Realizable k-ε turbulence model in step 1.2.2 is...

[0022]

[0023]

[0024] In the formula: t is time, ρ is density, k is turbulent kinetic energy, and x is... y Let u be the axial coordinate in the y-direction. y Let μ be the axial velocity component in the y-direction, and μ be the molecular viscosity. t S is the turbulent viscosity, S is a scalar measure of the deformation tensor, v is the molecular kinematic viscosity, and σ is the turbulent viscosity. k and σ ε Let G be the Prandtl constant corresponding to k and ε, respectively. k G is the turbulent kinetic energy generated due to the average velocity gradient. b Y is the turbulent kinetic energy generated by buoyancy, ε is the turbulent dissipation rate, and Y is the turbulent kinetic energy generated by buoyancy. M S represents the effect of wave expansion on the total dissipation rate in compressible turbulent flow. k Sε is a user-defined source item, C1, C2, C 1ε and C 3ε All are constants.

[0025] Preferably, the Eddy-Dissipation combustion model described in step 1.2.3 is...

[0026] The rate of formation R of substance i in reaction r i,r The smaller of the following two expressions is used to derive:

[0027]

[0028]

[0029] In the formula, i represents a reactant, r represents a reaction, and v represents a reaction. i ′ ,r M is the stoichiometric coefficient of reactant i in reaction r. w,i Let be the molecular weight of reactant i, A be an empirical constant with a value of 4.0, R be the reactant, and Y be the molecular weight of reactant i. R v′ is the mass fraction of reactant R. R,r M is the stoichiometric coefficient of reactant R in reaction r. w,R Let R be the molecular weight of reactant R, B be an empirical constant with a value of 0.5, P be any product, and Y be the molecular weight of reactant R. P Let v' be the mass fraction of any product P, j be a specific product, N be the total number of chemical substances, and v' be the mass fraction of any product P. j ′ ,r M is the stoichiometric coefficient of a certain product j in reaction r. w,j Let be the molecular weight of a certain product j.

[0030] Preferably, the DO radiation model in step 1.2.4 is...

[0031]

[0032] In the formula: Let be the partial derivative of a quantity with respect to all directions in the selected coordinate system. For position vectors, It is a direction vector. Let s be the scattering direction vector, s be the path length, a be the absorption coefficient, n be the refractive index, and σ be the scattering direction vector. s denoted as scattering coefficient, σ as Stephen-Boltzmann constant, I as radiation intensity, which is related to position r and s, T as local temperature, Φ as phase function, and Ω′ as solid angle.

[0033] Preferably, step 2 specifically includes the following steps:

[0034] Step 2.1: Establish a geometric model of the hydrogen storage cylinder based on the ANSYS thermal analysis module and perform mesh generation;

[0035] Step 2.2: Connect the ANSYS material module, fluid analysis module, thermal analysis module, and structural analysis module. Based on the data transfer between modules, achieve the coupling of fluid-thermal-solid multiphysics to obtain a fluid-thermal-solid multiphysics coupled finite element model of the gas cylinder. Specifically: transfer the thermophysical parameters and mechanical property parameters of the solid material of the gas cylinder defined in the material module to the thermal analysis module; transfer the finite element model of the gas cylinder with mesh generation and material property settings established in the thermal analysis module to the structural analysis module; transfer the inner and outer wall temperatures of the gas cylinder obtained from the fluid analysis module to the thermal analysis module, and the thermal analysis module performs thermal response analysis based on the inner and outer wall temperatures of the gas cylinder to obtain the overall thermal load of the gas cylinder, and transfers the overall thermal load of the gas cylinder to the structural analysis module; transfer the inner wall pressure of the gas cylinder obtained from the fluid analysis module to the structural analysis module.

[0036] Step 2.3: Based on the ANSYS structural analysis module, set boundary conditions and constraints for the finite element model of the gas cylinder, perform mechanical response analysis of the gas cylinder, and calculate the maximum stress in the fiber direction of the gas cylinder during the fire process.

[0037] Preferably, the constraints in step 2.3 include the overall thermal load of the gas cylinder, the pressure load on the inner wall of the gas cylinder, and the displacement constraints in three directions (x, y, z) of the gas cylinder opening.

[0038] Preferably, step 3 specifically includes the following sub-steps:

[0039] Step 3.1: Establish a gas cylinder damage criterion based on the maximum stress failure criterion:

[0040] |σ x |<X t (X c )

[0041] Where: σ x X represents the maximum stress in the fiber direction. t X represents the tensile strength in the fiber direction. c The compressive strength is σ in the fiber direction. Under fire conditions, the gas cylinder is subjected to the combined effects of thermal load on the outer wall and pressure load on the inner wall, and its failure mode mainly manifests as fiber tensile fracture. Therefore, the maximum stress σ in the fiber direction of the gas cylinder is taken as the compressive strength. x As the primary failure criterion, it is related to the fiber-direction tensile strength X. t For comparison, when σ x ≥X t When this happens, the gas cylinder is determined to have malfunctioned;

[0042] Step 3.2: Establish a method for predicting damage to hydrogen storage cylinders during the fire process. Specifically: First, import the cylinder's inner and outer wall temperatures at the initial fire time point into the thermal analysis module to obtain the overall thermal load of the cylinder at the initial fire time point; second, import the overall thermal load of the cylinder and the pressure load on the cylinder's inner wall at the initial fire time point into the structural analysis module; third, set the cylinder's boundary conditions and constraints, and determine the maximum stress σ in the cylinder's fiber direction. x The calculation was performed; then, the burning time was increased, and the above steps were repeated to obtain the maximum stress σ in the fiber direction of the gas cylinder during the burning process. x The relationship curve between burning time and internal pressure of the gas cylinder; finally, the failure state of the gas cylinder is judged based on the maximum stress failure criterion, when the maximum stress σ in the fiber direction of the gas cylinder... x ≥ Fiber direction tensile strength X t If the cylinder fails, the burning time corresponding to the failure point is the cylinder's fire resistance time, and the corresponding internal pressure is the cylinder's burst pressure.

[0043] Compared with the prior art, the present invention has at least the following beneficial technical effects:

[0044] (1) This invention realizes the multi-physics field coupling simulation of the hydrogen storage cylinder fire process by associating the ANSYS flow-heat-structure analysis module. The system restores the cylinder fire process, the cylinder thermal response process under heat load, and the cylinder mechanical response process under the combined action of heat-structure load. Based on the maximum stress failure criterion, the damage state of the cylinder fire process is analyzed, and the prediction of the cylinder fire resistance time and burst pressure is realized.

[0045] (2) The method of the present invention makes up for the problems of high risk, high cost and long time consumption of traditional fire test methods. Compared with the existing technology, it is more systematic, efficient and widely applicable. It provides an evaluation basis for improving the fire resistance performance of hydrogen storage cylinders and has important engineering application value. Attached Figure Description

[0046] Figure 1 A schematic flowchart of a method for predicting the damage state of hydrogen storage cylinders under fire conditions provided by an embodiment of the present invention;

[0047] Figure 2 This is a geometric model diagram of the solid domain and the inner and outer fluid domains of the hydrogen storage cylinder according to an embodiment of the present invention;

[0048] Figure 3 This is a mesh partitioning diagram of the solid domain and the inner and outer fluid domains of the hydrogen storage cylinder according to an embodiment of the present invention;

[0049] Figure 4 This is a cloud map showing the flow field temperature distribution during the combustion process of a hydrogen storage cylinder according to an embodiment of the present invention.

[0050] Figure 5This is a comparison diagram of the simulated gas pressure and the experimental pressure inside the bottle during the burning process according to an embodiment of the present invention;

[0051] Figure 6 This is a graph showing the relationship between the maximum stress in the fiber direction and the burning time of the hydrogen storage cylinder according to an embodiment of the present invention.

[0052] Figure 7 This is a graph showing the relationship between the maximum stress in the fiber direction and the internal pressure of the hydrogen storage cylinder according to an embodiment of the present invention. Detailed Implementation

[0053] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings, but the implementation of the present invention is not limited thereto. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0054] Please see Figure 1 The present invention provides a method for predicting the damage state of hydrogen storage cylinders under fire conditions, comprising the following steps:

[0055] Step 1: Establish a numerical model of a hydrogen storage cylinder fire scenario under fire conditions, solve the numerical model of the hydrogen storage cylinder fire scenario, and obtain the overall temperature and pressure distribution of the flow field inside and outside the cylinder during the fire process.

[0056] This step specifically includes the following sub-steps:

[0057] Step 1.1: Based on the ANSYS fluid analysis module, establish a geometric model of the gas cylinder fire scene, including the solid domain of the hydrogen storage cylinder and the fluid domain inside and outside the cylinder, and perform mesh generation.

[0058] In some embodiments of the present invention, based on the specific scenario of the hydrogen storage cylinder fire test [Tamura Y, et al. Development and Characteristics of a Burner for Localized Fire Tests and an Evaluation of Those Fire Tests[J] (Development, Characteristics and Evaluation of Burners for Localized Fire Tests)], a geometric model of the cylinder fire scenario is established using the ANSYS fluid analysis module, which includes the solid domain of the hydrogen storage cylinder and the fluid domains inside and outside the cylinder. Considering the complexity of the geometric model shape, the hydrogen storage cylinder and its internal flow field domain are divided into hexahedral meshes, and the external flow field domain is divided into tetrahedral meshes. After the meshing is completed, the boundary conditions of the ground, fuel inlet and external flow field boundary are named.

[0059] In some embodiments of the present invention, the established geometric model of the gas cylinder fire scene is as follows: Figure 2 As shown in the figure. The hydrogen storage cylinder consists of an aluminum alloy inner liner and a carbon fiber epoxy resin composite material layer. The cylinder is 800mm long, 150mm in outer diameter, with a composite material layer thickness of 11mm, an inner liner thickness of 3.1mm, an outer diameter of 80mm at the cylinder opening, and an inner diameter of 51.8mm at the cylinder opening. The external flow field of the cylinder is a hemispherical region with a diameter of 10000mm. Fuel enters the flow field region from the fuel inlet at the center of the bottom surface of the hemispherical region. The cylinder is placed horizontally 100mm above the fuel inlet region. It should be understood that the aforementioned specific values ​​are merely a concrete example and do not constitute a limitation on the protection range. The model after mesh generation is shown below. Figure 3 As shown.

[0060] In some embodiments of the present invention, three-dimensional modeling software, such as SolidWorks and ProE, can also be used to create geometric models.

[0061] Step 1.2: Define material properties, establish turbulence, combustion, and radiation models for the gas cylinder fire process, and set the solution method, boundary conditions, and initialization conditions. Specifically:

[0062] (a) Define material properties, including selecting propane-air mixture from the Fluent Mixed Materials Database, importing helium from the NIST Real Gas Materials Library as the bottle gas, adding aluminum alloy material and setting its density, specific heat capacity and thermal conductivity to constant values, and adding carbon fiber epoxy resin material and setting its density, specific heat capacity and thermal conductivity to piecewise linear values.

[0063] (b) Establish a Realizable k-ε turbulence model, introduce an enhanced wall function for near-wall treatment, and consider pressure gradient and thermal effects; and perform curvature correction on the turbulence model and consider the influence of buoyancy. The enhanced wall function, consideration of pressure gradient and thermal effects, curvature correction of the turbulence model, and consideration of the influence of buoyancy effects can all be set directly in the Fluent software.

[0064] The Realizable k-ε turbulence model is as follows:

[0065]

[0066]

[0067] In the formula: t is time, ρ is density, k is turbulent kinetic energy, and x is... y Let u be the axial coordinate in the y-direction. y Let μ be the axial velocity component in the y-direction, and μ be the molecular viscosity. tS is the turbulent viscosity, S is a scalar measure of the deformation tensor, v is the molecular kinematic viscosity, and σ is the turbulent viscosity. k and σ ε Let G be the Prandtl constant corresponding to k and ε, respectively. k G is the turbulent kinetic energy generated due to the average velocity gradient. b Y is the turbulent kinetic energy generated by buoyancy, ε is the turbulent dissipation rate, and Y is the turbulent kinetic energy generated by buoyancy. M S represents the effect of wave expansion on the total dissipation rate in compressible turbulent flow. k Sε is a user-defined source item, C1, C2, C 1ε and C 3ε All are constants.

[0068] (c) Establish the Eddy-Dissipation combustion model

[0069] The reaction rate R of reactant i in reaction r i,r The smaller of the following two expressions is used to derive:

[0070]

[0071]

[0072] In the formula, i represents a reactant, r represents a reaction, and v represents a reaction. i ′ ,r M is the stoichiometric coefficient of reactant i in reaction r. w,i Let be the molecular weight of reactant i, A be an empirical constant with a value of 4.0, R be a specific reactant, and Y be the molecular weight of reactant i. R v′ represents the mass fraction of a specific reactant R. R,r M is the stoichiometric coefficient of a specific reactant R in reaction r. w,R Let R be the molecular weight of reactant R, B be an empirical constant with a value of 0.5, P be any product, and Y be the molecular weight of reactant R. P Let v' be the mass fraction of any product P, j be a specific product, N be the total number of chemical substances, and v' be the mass fraction of any product P. j ′ ,r M is the stoichiometric coefficient of a certain product j in reaction r. w,j Let be the molecular weight of a certain product j.

[0073] (d) Establishing the DO radiation model

[0074]

[0075] In the formula: Let be the partial derivative of a quantity with respect to all directions in the selected coordinate system. For position vectors, It is a direction vector. Let s be the scattering direction vector, s be the path length, a be the absorption coefficient, n be the refractive index, and σ be the scattering direction vector. s Let σ be the scattering coefficient, σ be the Stephen-Boltzmann constant, and I be the radiation intensity, which is related to position. It is related to s, T is the local temperature, Φ is the phase function, and Ω′ is the solid angle.

[0076] (e) The solution method is set to the SIMPLE algorithm. Pressure is calculated using a second-order scheme, while density, momentum, turbulent kinetic energy, turbulent dissipation rate, material composition, energy, and radiation are calculated using a first-order upwind scheme. Boundary conditions are set as follows: inlet fuel velocity 1.2 m / s, temperature 1000 K, fuel C3H8 with a mass fraction of 1; outlet pressure 1 atmosphere, temperature 273 K, O2 mass fraction 0.21; ground temperature 273 K. Initial mass fractions of C3H8 are 0, O2 0.21, CO2 and H2O 0.01, initial ambient temperature 273 K, and initial internal cylinder pressure 35.1 MPa.

[0077] Step 1.3: After completing the model parameter settings, solve the established numerical model to obtain the overall temperature and pressure distribution of the internal and external flow fields of the hydrogen storage cylinder during the combustion process.

[0078] In some embodiments of the present invention, the overall temperature distribution of the internal and external flow fields of the hydrogen storage cylinder during the combustion process is as follows: Figure 4 As shown.

[0079] The obtained data on the change of gas pressure inside the bottle with the burning time were compared with the experimental results, such as... Figure 5 As shown, the maximum relative error between the simulation results and the experimental results is 3.01%, which is within the scope of engineering applications.

[0080] Step 2: Establish a finite element model of the gas cylinder based on the coupling of fluid-thermal-solid multiphysics fields, and perform mechanical response analysis of the gas cylinder based on the finite element model to calculate the maximum stress in the fiber direction of the gas cylinder during the fire process.

[0081] This step includes the following sub-steps:

[0082] Step 2.1: Based on the ANSYS thermal analysis module, perform the same process as in Step 1.1 to establish the gas cylinder geometric model and generate the mesh.

[0083] Step 2.2: Connect the ANSYS material module, fluid analysis module, thermal analysis module, and structural analysis module. Based on the data transfer between modules, achieve the coupling of fluid-thermal-solid multiphysics fields to obtain a fluid-thermal-solid multiphysics coupled finite element model of the gas cylinder. Specifically: transfer the thermophysical parameters and mechanical property parameters of the solid material of the gas cylinder defined in the material module to the thermal analysis module; transfer the finite element model of the gas cylinder with mesh generation and material property settings established in the thermal analysis module to the structural analysis module; transfer the inner and outer wall temperatures of the gas cylinder obtained from the fluid analysis module to the thermal analysis module, and the thermal analysis module performs thermal response analysis based on the inner and outer wall temperatures of the gas cylinder to obtain the overall thermal load of the gas cylinder, and transfers the overall thermal load of the gas cylinder to the structural analysis module; transfer the inner wall pressure of the gas cylinder obtained from the fluid analysis module to the structural analysis module.

[0084] Step 2.3: Based on the ANSYS structural analysis module, set boundary conditions and constraints for the finite element model of the gas cylinder, perform mechanical response analysis of the gas cylinder, and calculate the maximum stress in the fiber direction of the gas cylinder during the fire process.

[0085] In some embodiments of the present invention, the constraint settings include overall thermal load of the gas cylinder, pressure load on the inner wall of the gas cylinder, and displacement constraints in three directions (x, y, z) of the gas cylinder opening.

[0086] Step 3: Analyze the damage state of the hydrogen storage cylinder during the fire process based on the maximum stress failure criterion.

[0087] This step includes the following sub-steps:

[0088] Step 3.1: Establish a cylinder damage criterion based on the maximum stress failure criterion, specifically as follows:

[0089] σ x |<X t (X c )

[0090] Where: σ x X represents the maximum stress in the fiber direction. t X represents the tensile strength in the fiber direction. c Let σ represent the compressive strength along the fiber direction. Under fire conditions, hydrogen storage cylinders are subjected to the combined effects of thermal loads on the outer wall and pressure loads on the inner wall, and their failure mode mainly manifests as fiber tensile fracture. Therefore, the maximum stress σ along the fiber direction of the cylinder is taken as the compressive strength. x As the primary failure criterion, it is compared with the fiber-direction tensile strength X of carbon fiber epoxy resin composites investigated in the literature. t(2480MPa) [Kim EH, et al. Low-Velocity Impact and Residual Burst-Pressure Analysis of Cylindrical CompositePressure Vessels[J]] was compared with that of σ x ≥X t When this happens, the gas cylinder is determined to have malfunctioned.

[0091] Step 3.2: Establish a method for predicting damage to hydrogen storage cylinders during the fire process. Specifically, based on the maximum stress failure criterion, predict the cylinder's fire resistance time and burst pressure: First, import the cylinder's inner and outer wall temperatures at the initial fire time point into the thermal analysis module to obtain the overall thermal load of the cylinder at the initial fire time point; second, import the overall thermal load of the cylinder and the pressure load on the inner wall of the cylinder at the initial fire time point into the structural analysis module; third, set the cylinder's boundary conditions and constraints, and determine the maximum stress σ in the cylinder's fiber direction. x The calculation was performed; then, the burning time was increased, and the above steps were repeated to obtain the maximum stress σ in the fiber direction of the gas cylinder during the burning process. x The relationship curve between burning time and internal pressure of the gas cylinder; finally, the failure state of the gas cylinder is judged based on the maximum stress failure criterion 1. When the maximum stress σ in the fiber direction of the gas cylinder x ≥ Fiber direction tensile strength X t If the cylinder fails at a certain point, it is considered to have malfunctioned. The burning time corresponding to the point of failure is the cylinder's fire resistance time, and the corresponding internal pressure is the cylinder's burst pressure.

[0092] In some embodiments of the present invention, such as Figure 6 and Figure 7 As shown, the simulation results were compared with the experimental results according to the above method [Tamura Y, et al. Development and Characteristics of a Burner for Localized Fire Tests and an Evaluation of Those Fire Tests[J] (Development, Characteristics and Evaluation of a Burner for Localized Fire Tests)]: The predicted fire resistance time of the gas cylinder was 275.6s, with a maximum relative error of 6.26% compared with the experimental result (294s); the predicted burst pressure of the gas cylinder was 50.2MPa, with a maximum relative error of 5.64% compared with the experimental result (53.2MPa), which is within the scope of engineering applications.

[0093] Finally, it should be noted that the contents not described in detail in the embodiments of the present invention belong to the prior art known to those skilled in the art. The above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention can have various modifications and variations. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for predicting damage of a hydrogen storage cylinder under fire extreme conditions, characterized in that, The method comprises the following steps: Step 1, a numerical model of a hydrogen storage cylinder fire scene under fire conditions is established, the numerical model of the hydrogen storage cylinder fire scene is solved, and overall temperature and pressure distribution of an inner and outer flow field of the hydrogen storage cylinder in the fire process is obtained; Step 2, a finite element model of the cylinder based on flow-heat-solid multi-physical field coupling is established, and mechanical response analysis of the cylinder is carried out based on the finite element model of the cylinder, and the maximum stress of the hydrogen storage cylinder in the fire process is calculated; Step 3, damage state analysis of the hydrogen storage cylinder in the fire process is carried out based on the maximum stress failure criterion, and the fire resistance time and the burst pressure of the hydrogen storage cylinder are obtained; Wherein, step 1 specifically comprises the following steps: Step 1.1: based on the ANSYS fluid analysis module, a geometric model of the hydrogen storage cylinder fire scene containing a solid domain and a fluid domain inside and outside the cylinder is established and meshed; Step 1.2: define material properties, establish a turbulent flow model, a combustion model and a radiation model for the hydrogen storage cylinder fire process, and set the solution method, boundary conditions and initial conditions; Step 1.3: the numerical model is solved to obtain the overall temperature and pressure distribution of the inner and outer flow field of the hydrogen storage cylinder in the fire process; Step 1.2 comprises the following sub-steps: Step 1.2.1: define material properties, including thermal physical parameters of fuel-air mixture, gas in the cylinder and solid material of the cylinder; Step 1.2.2: establish a Realizable k-ε turbulent flow model, and introduce an enhanced wall function for near-wall treatment, and consider the pressure gradient effect and thermal effect; curvature correction is performed on the turbulent flow model, and the influence of buoyancy effect is considered: Step 1.2.3: establish an Eddy-Dissipation combustion model; Step 1.2.4: establish a DO radiation model; Step 1.2.5: set the solution method as SIMPLE algorithm, the pressure adopts second-order format, the density, momentum, turbulent kinetic energy, turbulent dissipation rate, material composition, energy and radiation adopt first-order upwind format; the boundary conditions include inlet fuel velocity and temperature, outlet pressure and temperature, boundary material composition mass fraction, ground temperature; the initial conditions include initial composition mass fraction, ambient initial temperature, initial pressure in the cylinder; The Realizable k-ε turbulent flow model in step 1.2.2 is: where: t is time, Rho is density, k is turbulent kinetic energy, x y is y is the axial coordinate in the direction, u y is y is the axial velocity component in the direction, Mu is the molecular viscosity, Mu t is the turbulent viscosity, S is the scalar measure of the deformation tensor, v is the kinematic viscosity of the fluid, Sigma k and Sigma ε are k and Epsilon are the corresponding Prandtl numbers, G k is the turbulent kinetic energy due to the mean velocity gradient, G b is the turbulent kinetic energy due to buoyancy forces, Epsilon is the turbulent dissipation rate, Y M is the effect of fluctuation dilatation in compressible turbulence on the overall dissipation rate, S k and Se are user-defined source terms, C 1, C 2, C 1ε and C 3ε are constants.

2. The method of claim 1, wherein the method is characterized by: In step 1.1, a geometric model is also established by a three-dimensional modeling software.

3. The method of claim 1, wherein the method further comprises: The Eddy-Dissipation combustion model in step 1.2.3 is: Rate of formation of substance i in reaction r R i,r The smaller of the two expressions is taken: wherein i is the stoichiometric coefficient of a reactant i in a reaction r, r is the stoichiometric coefficient of a reactant i in a reaction r, is the stoichiometric coefficient of a reactant i in a reaction r, is the molecular weight of a reactant i, A is an empirical constant, R is the stoichiometric coefficient of a reactant i in a reaction r, Y R is the mass fraction of a reactant R, is the stoichiometric coefficient of a reactant R in a reaction r, is the molecular weight of a reactant R, B is an empirical constant, P is an arbitrary product, Y P is the mass fraction of an arbitrary product P, j is the stoichiometric coefficient of a reactant i in a reaction r, N is the total number of chemical species, is the stoichiometric coefficient of a reactant i in a reaction r, is the molecular weight of a reactant i.

4. The method of claim 1, wherein the method is characterized by: The DO radiation model in step 1.2.4 is where: is the partial derivative of a quantity with respect to all directions in the chosen coordinate system, is the position vector, is the direction vector, is the scattering direction vector, s is the path length, is the absorption coefficient, is the refractive index, is the scattering coefficient, is the Stefan-Boltzmann constant, is the radiance, related to the position and s , is the local temperature, is the phase function, is the solid angle.

5. The method for predicting damage of a hydrogen storage cylinder in a fire extreme condition according to claim 1, characterized in that, Step 2 specifically comprises the following steps: Step 2.1: based on the ANSYS thermal analysis module, a geometric model of the hydrogen storage cylinder is established and meshed; Step 2.2: associate ANSYS material module, fluid analysis module, thermal analysis module and structural analysis module, based on data transmission between modules, realize the coupling of flow-thermal-solid multi-physical field, get the finite element model of gas cylinder of flow-thermal-solid multi-physical field coupling, specifically: the thermal physical parameters and mechanical performance parameters of gas cylinder solid material defined by material module are transmitted to thermal analysis module; the finite element model of gas cylinder with grid division and material attribute setting established by thermal analysis module is transmitted to structural analysis module; the inner and outer wall temperature of gas cylinder obtained by fluid analysis module is transmitted to thermal analysis module, and thermal analysis module carries out thermal response analysis based on the inner and outer wall temperature of gas cylinder to obtain the overall thermal load of gas cylinder, and the overall thermal load of gas cylinder is transmitted to structural analysis module; the inner wall pressure of gas cylinder obtained by fluid analysis module is transmitted to structural analysis module; Step 2.3: based on ANSYS structural analysis module, set boundary conditions and constraints for gas cylinder finite element model, carry out mechanical response analysis of gas cylinder, calculate the maximum stress of gas cylinder in fiber direction in fire process.

6. The method for predicting damage of a hydrogen storage cylinder in a fire extreme condition according to claim 5, characterized in that, The constraints in step 2.3 include overall thermal load of gas cylinder, inner wall pressure load of gas cylinder and displacement constraints in three directions (x, y, z) of gas cylinder mouth.

7. The method of claim 1-6, wherein the method is characterized by, Step 3 specifically includes the following sub-steps: Step 3.1: establish gas cylinder damage criterion based on maximum stress failure criterion: wherein: σ x is the maximum stress in the fiber direction, X t is the tensile strength in the fiber direction, X c is the compressive strength in the fiber direction; Under fire conditions, the gas cylinder is subjected to the combined action of thermal load on the outer wall and pressure load on the inner wall, and its failure mode is fiber tensile fracture, so the maximum stress in the fiber direction of the gas cylinder is taken as the failure criterion σ x The fiber tensile strength in the fiber direction is taken as the failure criterion X t When σ x ≥ X t , it is determined that the gas cylinder has failed. Step 3.2: Establish a hydrogen storage cylinder damage prediction method for the fire process, specifically: first, import the initial fire time point cylinder inner and outer wall temperature into the thermal analysis module to obtain the initial fire time point cylinder overall thermal load; second, import the initial fire time point cylinder overall thermal load and the cylinder inner wall surface pressure load into the structural analysis module; third, set the cylinder boundary conditions and constraints, and solve the calculation of the maximum stress of the cylinder fiber direction σ x ; then, increase the fire time, repeat the above steps, and obtain the relationship curve of the maximum stress of the cylinder fiber direction, the fire time and the internal pressure of the cylinder σ x ; finally, based on the maximum stress failure criterion, the failure state of the cylinder is judged, when the maximum stress of the cylinder fiber direction σ x ≥ tensile strength of fiber direction X t , it is considered that the cylinder has failed, at this time, the fire time corresponding to the failure point of the cylinder is the fire resistance time of the cylinder, and the internal pressure corresponding to the cylinder is the burst pressure of the cylinder.

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