A method for analyzing the compressive performance of fuel cell bipolar plates based on finite element technology

Abstract

The present invention relates to a method for analyzing the compressive performance of fuel cell bipolar plates based on finite element technology. The method comprises the following steps: S1, constructing a 3D model of the bipolar plate and sealing ring; S2, importing the 3D model of the bipolar plate and sealing ring into finite element analysis software; S3, configuring the models of the bipolar plate and sealing ring accordingly; and S4, performing finite element analysis on the bipolar plate during compression to obtain the stress distribution of the bipolar plate. Compared with the prior art, the present invention uses computer finite element analysis technology to analyze the mechanical properties of the bipolar plate under assembly pressure. This not only reduces a significant amount of experimental time and material waste, eliminates the tedious process of manufacturing actual bipolar plate models, calculates the stress distribution of the bipolar plate, but also allows the design of a 3D model of the bipolar plate based on the relationship between geometric structural features and performance, providing a scientific basis for the development of high-performance fuel cell bipolar plates.

Description

Technical Field

[0001] The present invention relates to the technical field of fuel cells, and in particular to a method for analyzing the compressive performance of a fuel cell bipolar plate based on finite element technology. Background Art

[0002] Proton exchange membrane fuel cell (PEMFC) is a device that uses hydrogen as fuel and converts its chemical energy into electrical energy through chemical reactions. It has the advantages of a high energy conversion rate of 85-90%, no pollution to the environment and no noise. It has a wide range of applications in transportation, national defense and energy fields.

[0003] Bipolar plates are a key component of PEMFCs, accounting for approximately 80% of the volume and mass of a proton exchange membrane cell and 30% of its cost. They isolate the fuel from the oxidant, provide a space for gas reactions, support the cell electrodes, and conduct current. Batteries often operate in high-temperature, highly acidic environments with a pH of 2-3 and temperatures of 80-100°C. Therefore, bipolar plates must possess strong corrosion resistance and thermal conductivity. Furthermore, they primarily bear the internal loads of the cell, requiring high mechanical strength. There are currently three common bipolar plate materials: graphite, metal and composite graphite composite bipolar plates. Although graphite has good electrical conductivity, thermal conductivity and corrosion resistance, it is a brittle material with low mechanical strength, making it difficult to apply to actual battery working environments; metal bipolar plate materials have good electrical conductivity, thermal conductivity and mechanical strength, but under acidic conditions a passivation layer will form on the surface, reducing its thermal and electrical conductivity; the most widely used composite bipolar plate is composed of graphite conductive materials interconnected to form a conductive network, and the matrix formed by resin curing is filled to provide bending strength and airtightness and other properties. It has both certain electrical conductivity and corrosion resistance, and certain mechanical strength.

[0004] Currently, a large number of researchers focus on experimental studies of the corrosion resistance and airtightness of bipolar plates, but have largely ignored the mechanical strength and stress distribution of bipolar plates during use. For example, CN202110686853.5 discloses a test device for the airtightness of fuel cell bipolar plates; CN202011181009.9 and CN202010747313.9 disclose a fuel cell anti-corrosion layer and its preparation method.

[0005] As fuel cell bipolar plates are required to be thinner and thinner in practical engineering applications, in addition to meeting basic material performance requirements, they must also be resistant to damage and destruction during assembly. Experimental exploration is time-consuming, costly, and involves numerous uncontrollable factors. Combining computer simulation not only saves significant resources and reveals the stress distribution of bipolar plates under load in a working environment, but also allows for the design of 3D models of bipolar plates based on the relationship between geometric structural characteristics and performance, providing a scientific basis for the development of high-performance fuel cell bipolar plates.

[0006] Therefore, it is of great research significance to study the stress distribution of fuel cell bipolar plates after they are subjected to assembly pressure through computer simulation methods, and it has become more urgent to establish a systematic computational simulation method to study the stress distribution of bipolar plates. Summary of the Invention

[0007] The purpose of the present invention is to overcome the defects of the above-mentioned prior art and provide a method for analyzing the compressive performance of fuel cell bipolar plates based on finite element technology.

[0008] The purpose of the present invention can be achieved by the following technical solutions:

[0009] A method for analyzing the compressive performance of a fuel cell bipolar plate based on finite element technology, the method comprising the following steps:

[0010] S1. Build 3D models of bipolar plates and sealing rings;

[0011] S2. Importing the 3D model of the bipolar plate and the sealing ring into the finite element analysis software;

[0012] S3. Setting the models of the bipolar plate and the sealing ring accordingly;

[0013] S4. Perform finite element analysis on the bipolar plate compression process to obtain the stress distribution of the bipolar plate.

[0014] Preferably, step S3 is specifically:

[0015] S301, assigning corresponding parameter attributes to the 3D model of the bipolar plate model and the sealing ring;

[0016] S302, assembling the bipolar plate 3D model and the sealing ring 3D model;

[0017] S303, simulating the bipolar plate compression process, setting corresponding analysis step parameters, and controlling the bipolar plate force loading time;

[0018] S304, configuring the contact surface between the bipolar plate and the sealing ring, applying corresponding loads and setting boundary conditions for constraints;

[0019] S305: Mesh the assembled model.

[0020] Preferably, the parameter attributes in S301 include density, Young's modulus, Poisson's ratio, bipolar plate plasticity, and sealing ring hyperelasticity.

[0021] Preferably, during assembly in S302 , the bipolar plate 3D model and the sealing ring 3D model are cut into two parts from the middle, and only one part is assembled.

[0022] Preferably, in the analysis step setting process in S303, a static and general analysis step is adopted, the total time is 10, the maximum incremental step is 1, the minimum incremental step is 1E-10, and the large deformation setting is turned on.

[0023] Preferably, S304 specifically includes:

[0024] Apply Tie binding to the contact surface between the bipolar plate and the sealing ring, selecting the sealing ring as the primary surface and the bipolar plate as the secondary surface;

[0025] A downward load along the normal line is applied to the top sealing ring, and the bottom sealing ring is constrained by boundary conditions to keep it fixed, simulating the compression process of the bipolar plate.

[0026] Preferably, S305 specifically includes:

[0027] The bipolar plate model is divided into three regions: the bipolar plate air inlet, water inlet, and the connecting holes or flow channels are one region, recorded as the air inlet region; the middle parallel flow channel is one region, recorded as the parallel flow channel region; the contact part between the sealing ring and the bipolar plate near the parallel flow channel is one region, recorded as the sealing ring contact region;

[0028] The different areas of the bipolar plate and the sealing ring are meshed separately.

[0029] Preferably, the air inlet area is divided by a tetrahedral grid with the highest grid density; the sealing ring contact area is divided by a hexahedral grid with a grid density less than that of the air inlet area; the parallel flow channel area model is divided by a hexahedral grid with a grid density less than that of the sealing ring contact area.

[0030] Preferably, the mesh type of the sealing ring is hexahedron, and the mesh density is the smallest.

[0031] Preferably, the method further comprises the steps of:

[0032] S5. Optimize the bipolar plate model based on the bipolar plate stress distribution obtained through finite element analysis, and repeat steps S1 to S4 until the analysis results meet the expected standards.

[0033] Compared with the prior art, the present invention has the following advantages:

[0034] (1) The present invention uses finite element analysis technology to assign material properties to the 3D model of the fuel cell bipolar plate and assemble it, sets the contact between the bipolar plate and the sealing rubber ring it contacts, applies a load in the normal direction to the protruding sealing rubber ring, and constrains and fixes the sealing ring at the lower end, simulates the bipolar plate in the compression process, calculates information such as the stress concentration point, and can provide an effective reference for the design of the bipolar plate model, thereby further optimizing the designed plate model.

[0035] (2) The present invention uses computer finite element analysis technology to analyze the stress conditions of the bipolar plates, which not only reduces a lot of experimental time and material costs, eliminates the tedious process of manufacturing actual bipolar plate models, and obtains the stress distribution of the bipolar plates in the working environment, but also can simulate multiple models, assign various material properties, and study more diverse situations, providing a broader perspective for future bipolar plate material research. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 This is a flowchart of a method for analyzing the compressive performance of a fuel cell bipolar plate based on finite element technology according to the present invention;

[0037] Figure 2 Schematic diagram of the structure of the bipolar plate model in the present invention, wherein (a) is the A plate (anode plate) model, and (b) is the C plate (cathode plate) model.

[0038] Figure 3 Schematic diagram of the structure of the sealing rubber ring model in the present invention, wherein (a) is the sealing ring model at the groove on the outer side of plate A, (b) is the sealing ring model connecting plate A and plate C, and (c) is the sealing ring model connected to the outer side of plate C.

[0039] Figure 4 It is a schematic diagram of the assembly structure of the bipolar plate model and the sealing ring model in the present invention.

[0040] Figure 5 It is a schematic diagram of the corresponding load conditions applied to the sealing ring model during the compression process of the present invention, wherein (a) is the fixed constraint at the bottom of the outer sealing ring of the C plate, and (b) is a schematic diagram of the load applied to the outer sealing ring of the A plate.

[0041] Figure 6 It is a schematic diagram of the grid division of the bipolar plate model and the sealing ring model in the present invention.

[0042] Figure 7 It is a stress cloud diagram of the bipolar plate in the present invention under a certain load condition.

[0043] Figure 8 It is a schematic diagram of the stress concentration points of the bipolar plate of the present invention during the stress-bearing process. DETAILED DESCRIPTION

[0044] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. Note that the following embodiments are merely illustrative in nature and the present invention is not intended to limit its applicable objects or uses, and the present invention is not limited to the following embodiments.

[0045] Example

[0046] like Figure 1As shown, this embodiment provides a method for analyzing the compressive performance of a fuel cell bipolar plate based on finite element technology, comprising the following steps:

[0047] S1. Build a 3D model of the bipolar plate and three-layer sealing ring;

[0048] S2. Importing the 3D model of the bipolar plate and the sealing ring into the finite element analysis software;

[0049] S3. Setting the models of the bipolar plate and the sealing ring accordingly;

[0050] S4. Perform finite element analysis on the bipolar plate compression process.

[0051] In this embodiment, the characteristics of the bipolar plate and sealing ring model constructed in step S1 are as follows:

[0052] The 3D model of the bipolar plate contains parallel flow channels composed of several straight or S-shaped ridges and grooves, as well as two air inlet holes and one water inlet hole. The air inlet holes and the parallel flow channels are connected by corresponding flow channels. The air inlet holes are distributed around the model, and the water inlet holes are distributed on both sides of the model. There is a pair of common air channels, a pair of hydrogen channels and a pair of water channels between the cathode plate and the anode plate. The sealing grooves on the hydrogen side and the sealing grooves on the air side are sealed with elastic rubber materials respectively, and bridges are laid between the gas inlet and outlet and the gas flow channels to support the components and seal the gas, etc. Figure 2 and Figure 3 The bipolar plate dimensions are shown in Table 1. This model is based on a high current density discharge fuel cell stack flow field plate designed in a patent publication (CN 108172857 A).

[0053] Table 1 Bipolar plate size parameters

[0054]

[0055] In step S2, the 3D model of the bipolar plate and the sealing ring is imported, which includes the following steps:

[0056] Input the bipolar plate and seal ring models created using 3D modeling software into corresponding .stp files;

[0057] In the finite element analysis software, select the import type as part, select the .stp format for the file, and find the corresponding file to import.

[0058] Step S3 sets the model of the bipolar plate and the sealing ring, including the following steps:

[0059] S301. Assign corresponding properties to the bipolar plate model and the sealing ring model, including density, Young's modulus, and Poisson's ratio, and input the bipolar plate plasticity and sealing rubber ring hyperelastic properties based on experimental data.

[0060] S302, assemble the bipolar plate model and the three-layer sealing ring model. Since the bipolar plate and sealing ring models are structurally symmetrical, the model can be simplified to only half of the model for assembly analysis during the finite element analysis process to improve the calculation speed. The size of the groove of the bipolar plate and the size of the sealing rubber ring are structurally consistent. During assembly, only the corresponding model needs to be selected. The computer will intelligently match the position between the bipolar plate and the sealing ring and automatically complete the assembly. Figure 4 shown.

[0061] S303, set the load time to 10, the maximum increment to 1, the minimum increment to 1E-10, and enable the large deformation setting;

[0062] The sealing ring is made of rubber and will deform significantly when subjected to load. Enabling the large deformation setting can improve the convergence of the calculation process.

[0063] S304, apply a load of 0.5 MPa in the opposite direction to the Y axis to the XZ plane of the sealing ring at one end, such as Figure 5 (b) and impose boundary condition constraints on the sealing ring at the other end, as shown in Figure 5 (a)

[0064] When configuring the contact surface between the bipolar plate and the sealing ring, it is assumed that the bipolar plate and the sealing ring do not slide relative to each other during the compression process, and the following configuration is applied:

[0065] Apply Tie binding to the four contact surfaces between the bipolar plate and the sealing ring, select the sealing ring as the master surface and the bipolar plate as the slave surface, and set the binding deviation range to 0.01.

[0066] S305. When meshing the bipolar plate and sealing ring model, the bipolar plate model is divided into three regions, including the bipolar plate air inlet, water inlet, and connecting holes or flow channels therebetween as one region, the middle parallel flow channel as one region, and the contact portion between the sealing ring and the bipolar plate near the parallel flow channel as one region;

[0067] The model of the air inlet area uses a tetrahedron mesh with the largest mesh density. The model of the sealing ring contact area uses a hexahedron mesh with a mesh density smaller than that of the air inlet area. The model of the parallel flow channel area uses a hexahedron mesh with a mesh density smaller than that of the sealing ring contact area. Figure 6 As shown, the mesh type of the sealing ring model is hexahedron, and the mesh density is the smallest;

[0068] The finite element model of the bipolar plate uses a tetrahedral mesh to increase the convergence of the simulation; the finite element model of the sealing ring uses a hexahedral mesh and a hybrid calculation method.

[0069] Before conducting finite element analysis, it is necessary to review the set data to ensure that all data are correct before conducting finite element analysis.

[0070] S4. Finite element analysis is performed on the bipolar plate model during compression to obtain the stress distribution of the bipolar plate after compression, such as Figure 7 As shown; the stress concentration point of the bipolar plate after compression can also be obtained, as shown Figure 8 shown.

[0071] After analysis, it was found that in addition to the compressed parts of the plates, stress concentration would occur at the corners of the air inlet grooves of the plates, and large stress would also appear at the connection between the water inlet and the air inlet. No stress concentration occurred in other parts. According to the results, improvements and optimizations can be made at the structures where stress concentration occurs. The structure of the bipolar plate design can be adjusted through 3D modeling software, and then simulated through the finite element method until there are no such dangerous stress concentration points, so as to avoid cracking or even damage of the bipolar plate due to stress concentration during actual use.

[0072] In summary, the present invention uses 3D modeling software to establish the bipolar plate model required for actual design, and then uses finite element analysis software to assign material properties to the model, divide and assemble it, and configure the corresponding contact surfaces. One end is constrained and fixed, and the other end is loaded to simplify the simulated stress conditions. The mechanical properties information such as stress concentration points and strains of the double-polar plate after compression can be analyzed. The double-polar plate model is improved based on the information obtained, and the above process is repeated until the analysis results reach the expected standard.

[0073] The above embodiments are merely examples and do not limit the scope of the present invention. These embodiments can be implemented in various other ways, and various omissions, replacements, and changes can be made without departing from the technical concept of the present invention.

Claims

1. A method for analyzing the compressive performance of fuel cell bipolar plates based on finite element technology, characterized in that: The method comprises the following steps: S1. Build 3D models of bipolar plates and sealing rings; S2. Importing the 3D model of the bipolar plate and the sealing ring into the finite element analysis software; S3. Setting the models of the bipolar plate and the sealing ring accordingly; S4, performing finite element analysis on the bipolar plate during compression to obtain the stress distribution of the bipolar plate; Step S3 is specifically as follows: S301, assigning corresponding parameter attributes to the 3D model of the bipolar plate model and the sealing ring; S302, assembling the bipolar plate 3D model and the sealing ring 3D model; S303, simulating the bipolar plate compression process, setting corresponding analysis step parameters, and controlling the bipolar plate force loading time; S304, configuring the contact surface between the bipolar plate and the sealing ring, applying corresponding loads and setting boundary conditions for constraints; S305, meshing the assembled model; S304 is specifically: Apply Tie binding to the contact surface between the bipolar plate and the sealing ring, selecting the sealing ring as the primary surface and the bipolar plate as the secondary surface; A downward load along the normal line is applied to the top sealing ring, and the bottom sealing ring is constrained by boundary conditions to keep it fixed, simulating the compression process of the bipolar plate.

2. The method for analyzing the compressive performance of a fuel cell bipolar plate based on finite element technology according to claim 1, characterized in that: The parameter attributes in S301 include density, Young's modulus, Poisson's ratio, bipolar plate plasticity, and seal ring hyperelastic properties.

3. The method for analyzing the compressive performance of a fuel cell bipolar plate based on finite element technology according to claim 1, characterized in that: During assembly in S302 , the bipolar plate 3D model and the sealing ring 3D model are cut into two parts from the middle, and only one part is assembled.

4. The method for analyzing the compressive performance of a fuel cell bipolar plate based on finite element technology according to claim 1, characterized in that: In S303, the analysis step is set to static and general, with a total time of 10, a maximum incremental step of 1, a minimum incremental step of 1E-10, and the large deformation setting is turned on.

5. The method for analyzing the compressive performance of a fuel cell bipolar plate based on finite element technology according to claim 1, characterized in that: S305 is specifically: The bipolar plate model is divided into three regions: the bipolar plate air inlet, water inlet, and the connecting holes or flow channels are one region, recorded as the air inlet region; the middle parallel flow channel is one region, recorded as the parallel flow channel region; the contact part between the sealing ring and the bipolar plate near the parallel flow channel is one region, recorded as the sealing ring contact region; The different areas of the bipolar plate and the sealing ring are meshed separately.

6. The method for analyzing the compressive performance of a fuel cell bipolar plate based on finite element technology according to claim 5, characterized in that: The air inlet area is divided by tetrahedral mesh, which has the highest mesh density. The sealing ring contact area is divided by hexahedral mesh, which has a smaller mesh density than the air inlet area. The parallel flow channel area model is divided by hexahedral mesh, which has a smaller mesh density than the sealing ring contact area.

7. The method for analyzing the compressive performance of a fuel cell bipolar plate based on finite element technology according to claim 6, characterized in that: The mesh type of the sealing ring is hexahedron, and the mesh density is the smallest.

8. The method for analyzing the compressive performance of a fuel cell bipolar plate based on finite element technology according to claim 1, characterized in that: The method further comprises the steps of: S5. Optimize the bipolar plate model based on the bipolar plate stress distribution obtained through finite element analysis, and repeat steps S1 to S4 until the analysis results meet the expected standards.

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