A lightning-imitating hierarchical fuel cell bipolar plate flow field structure and a detection method thereof

Abstract

The application discloses an imitated thunder and lightning hierarchical fuel cell bipolar plate flow channel field structure and a detection method thereof. The structure comprises a reaction gas inlet, a reaction gas outlet, a gas inlet flow channel field and a gas outlet flow channel field. The method comprises the following steps: step 1, designing the imitated thunder and lightning hierarchical fuel cell bipolar plate flow channel field structure; step 2, establishing a three-dimensional geometric model of the imitated thunder and lightning hierarchical fuel cell bipolar plate and a proton exchange membrane fuel cell; step 3, carrying out mesh division on the geometric model of the imitated thunder and lightning hierarchical fuel cell; step 4, simulating the performance of the imitated thunder and lightning hierarchical fuel cell and the bipolar plate flow field; and step 5, extracting the performance data of the imitated thunder and lightning hierarchical fuel cell and the bipolar plate flow field, and analyzing different bipolar plate flow channel field structures based on the performance simulation data. The application can solve the problems of low fuel cell working efficiency and difficulty in discharging water in the bipolar plate.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of bionic structure engineering, and particularly relates to a lightning-imitating hierarchical fuel cell bipolar plate flow channel field structure and a detection method thereof. BACKGROUND

[0002] With the development of human science and technology and civilization, people's life becomes convenient, but at the same time, people's demand for energy is getting larger and larger, which brings an irreconcilable contradiction to human beings, mainly reflected in two aspects: first, fossil fuels such as oil, coal and natural gas, as the main source of current energy, have the characteristics of non-renewability, which is contrary to the concept of human demand for energy and long-term social development; second, the environmental problems caused by fossil fuels are becoming increasingly serious, which seriously endangers the human living environment. Hydrogen energy, as a clean energy that can store waste energy and promote the transformation of traditional fossil energy to green energy, has an energy density (140 MJ / kg) that is 3 times that of oil and 4.5 times that of coal, and is regarded as a disruptive technology for future energy revolution. Proton exchange membrane fuel cell is a device that directly converts hydrogen energy into electrical energy without going through Carnot cycle, so the proton exchange membrane fuel cell has the advantages of no pollution, low noise, high energy conversion efficiency, etc. The bipolar plate, as a key component of the fuel cell, accounts for about 80% of the weight of the fuel cell, and its main functions include supporting the fuel cell stack, conducting current and uniformly distributing the reaction gas through the flow channel field, etc. The surface flow field structure of the bipolar plate affects the distribution of the reaction gas in the bipolar plate and directly affects the working performance of the fuel cell.

[0003] The traditional fuel cell bipolar plate flow field structure mainly includes parallel flow channels, serpentine flow channels, mesh flow channels and the like. The main features of the traditional bipolar plate flow channel field structure are simple structure and good formability, but the simple flow field structure leads to problems such as limited transmission, gas blockage and difficulty in timely discharge of water in the bipolar plate, ultimately resulting in low performance of the bipolar plate flow field and low working efficiency of the fuel cell. Therefore, high-efficiency and complex bipolar plate flow channel field structure is a key technology to obtain high-performance proton exchange membrane fuel cells.

[0004] The structure designed by nature is to achieve the optimal energy solution, which is suitable in features, adapts to the environment, light in weight, and optimal in performance and function. The essence of bionics is to learn the design method and material layout of natural structure. Therefore, through the bionic strategy, the design of new structures or the optimization of existing workpieces can be realized as needed. Lightning is a natural discharge phenomenon widely existing in nature, and the condition for generating lightning is that there is charge accumulation in thundercloud and polarity is generated, the upper part of the cloud is mainly positive charge, and the lower part is mainly negative charge, and a potential difference is formed between the upper and lower parts of the cloud. When the potential difference reaches a certain degree due to the accumulation of electric charge, a large amount of electric charge is discharged through the channel to form lightning. This method of electric charge discharge along the preferred path has strong reference value for bionics and material transmission. SUMMARY

[0005] The technical problem to be solved by the present application is to provide a lightning-imitating hierarchical fuel cell bipolar plate flow field structure and a detection method thereof, which can solve the problems of low fuel cell working efficiency and difficulty in discharging water from the bipolar plate.

[0006] To solve the above technical problem, the present application provides a lightning-imitating hierarchical fuel cell bipolar plate flow field structure, which comprises a reaction gas inlet, a reaction gas outlet, an inlet gas flow field, and an outlet gas flow field; the inlet gas flow field comprises an inlet gas main flow channel and an inlet gas branch flow channel, and the outlet gas flow field comprises an outlet gas main flow channel and an outlet gas branch flow channel; the reaction gas inlet is connected to the inlet gas main flow channel, the reaction gas outlet is connected to the outlet gas main flow channel, the outlet gas flow field is distributed at the end of the inlet gas branch flow channel and is mirror-distributed, and the outlet gas branch flow channel converges and extends to the outlet.

[0007] Preferably, the inlet gas flow field is determined according to the hierarchical characteristics and distribution rules of natural lightning, and the coverage range is a 90°-angle sector.

[0008] Preferably, the flow channel of the inlet gas flow field is composed of multiple straight flow channels, and the inclination angle between the multiple straight flow channels is 15°-45°, and the inclination angle of the inlet gas branch flow channel relative to the main flow channel is 30°-90°.

[0009] Preferably, the outlet gas flow field is distributed symmetrically along the diagonal of a rectangle, the outlet gas flow channel is composed of straight flow channels, is distributed between the edge of the rectangular bipolar plate and the end of the inlet gas branch flow channel, and the end of the inlet gas branch flow channel has a gap with the outlet gas flow channel on the same side.

[0010] Preferably, the cross-sectional shape of the inlet gas flow field and the outlet gas flow field is rectangular, the height is 1 mm, the width of the flow channel at a non-branch position is 1 mm, and the width of the flow channel at a branch position is 1-2 mm.

[0011] Correspondingly, a detection method of the lightning-imitating hierarchical fuel cell bipolar plate flow field structure comprises the following steps:

[0012] Step 1: design a lightning-imitating hierarchical fuel cell bipolar plate flow field structure;

[0013] Step 2: establish a three-dimensional geometric model of the lightning-imitating hierarchical fuel cell bipolar plate and the proton exchange membrane fuel cell;

[0014] Step 3: perform meshing on the geometric model of the lightning-imitating hierarchical fuel cell;

[0015] Step 4: simulate the performance of the lightning-imitating hierarchical fuel cell and the bipolar plate flow field;

[0016] Step 5, extract the performance data of the lightning-imitating staged fuel cell and bipolar plate flow field, and analyze the different bipolar plate flow field structures based on the performance simulation data.

[0017] Preferably, in step 2, the three-dimensional geometric model of the lightning-imitating staged fuel cell bipolar plate and the proton exchange membrane fuel cell is established as follows: using Rhino three-dimensional modeling software to establish a two-dimensional model of the lightning-imitating bipolar plate flow field structure, and using extrusion, stretching, and Boolean operation methods to establish a three-dimensional geometric model of the lightning-imitating staged fuel cell bipolar plate and its flow field structure, wherein the geometric model of the flow field structure and the surface flow channel structure of the bipolar plate are in close contact; according to the sizes of different components of the proton exchange membrane fuel cell and the structure of the bipolar plate, three-dimensional cubic geometric models of the gas diffusion layer, the catalyst layer, and the proton exchange membrane with different structural sizes are established. Among them, the cathode gas diffusion layer 4 and the anode gas diffusion layer 8 are in contact with one side of the cathode bipolar plate 5 and the anode bipolar plate 7 with flow channel structure, to realize the stable diffusion of the reaction gas in the bipolar plate flow channel; the back side of the cathode gas diffusion layer 4 and the anode gas diffusion layer 8 is in contact with the cathode catalyst layer 3 and the anode catalyst layer 9, to realize the reaction of the reaction gas into the catalyst layer; the back side of the cathode catalyst layer 3 and the anode catalyst layer 9 is in contact with the proton exchange membrane 6, to realize the migration of hydrogen ions from the anode to the cathode in the reaction process; finally, each component is assembled and connected by geometric assembly, and the three-dimensional geometric model of the proton exchange membrane fuel cell in step format is exported.

[0018] Preferably, in step 3, the geometric model of the lightning-imitating staged fuel cell is meshed as follows: the fuel cell geometric file in step format is imported into ICEM, the topological inspection of the geometric model is performed, the problems existing in the geometry are repaired, the initial block is established, the block is divided according to the calculation domain, the block and the geometric model are established according to the different components of the fuel cell and the boundary conditions, and the block is divided and associated according to the structural characteristics of the geometric model; the generation parameters of the geometric grid are set, the grid model of the fuel cell is established, and the grid parameters are adjusted according to the grid quality of the geometric model; after the grid quality meets the simulation conditions, the grid is converted into a non-structural grid for application in Fluent simulation operation; finally, the msh format grid file is output and imported into Fluent for simulation calculation of the performance of the fuel cell and the bipolar plate flow field.

[0019] Preferably, in step 4, the performance of the lightning-imitating staged fuel cell and the bipolar plate flow field is simulated as follows: the msh file of the fuel cell is imported into the Fluent module in Ansys, the proton exchange membrane fuel cell module is opened, and the fuel cell simulation parameters are set, as shown in the following table:

[0020] Parameter table

[0021]

[0022]

[0023] The present application can effectively exert the advantage of the charge preferred orientation flow of the lightning structure in nature, can significantly improve the distribution uniformity of oxygen in the bipolar plate flow field structure, and can make the pressure in the bipolar plate flow field structure stable in a smaller range, reduce the pressure difference inside the flow channel, make the reaction as fully as possible, and further improve the hydrogen utilization rate; meanwhile, the present application also combines the bionic lightning layered structure with the zigzag type flow field, the bionic lightning graded gas inlet flow field end is not connected with the gas outlet flow channel, this design can force the reaction gas in the bionic lightning graded gas inlet flow field to enter the gas diffusion layer, so that the reaction is more sufficient, and the water produced by the reaction and the unreacted gas are discharged through the gas outlet flow field, the shorter gas outlet channel accelerates the discharge of water, avoids the problem of uneven distribution of reaction gas caused by the existence of water in the gas inlet flow field, and greatly improves the power generation efficiency of the fuel cell. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 It is a three-dimensional geometric model diagram of the proton exchange membrane fuel cell of the present application.

[0025] Figure 2 It is a bionic lightning layered fuel cell bipolar plate flow field structure diagram of the present application.

[0026] Figure 3 It is an oxygen distribution diagram in the gas diffusion layer of the traditional serpentine flow field fuel cell of the present application.

[0027] Figure 4 It is a gas pressure distribution diagram in the traditional serpentine flow field bipolar plate flow channel of the present application.

[0028] Figure 5 It is a water distribution diagram in the traditional serpentine flow field bipolar plate flow channel of the present application.

[0029] 1, cathode bipolar plate gas inlet flow field; 2, anode bipolar plate gas outlet flow field; 3, cathode catalyst layer; 4, cathode gas diffusion layer; 5, cathode bipolar plate; 6, proton exchange membrane; 7, anode bipolar plate; 8, anode gas diffusion layer; 9, anode catalyst layer; 10, cathode bipolar plate gas outlet flow field; 11, anode bipolar plate gas inlet flow field; 12, reaction gas inlet; 13, gas inlet flow field; 14, gas outlet flow field; 15, reaction gas outlet. DETAILED DESCRIPTION

[0030] The application discloses a lightning-imitating hierarchical fuel cell bipolar plate flow field structure, which comprises a reaction gas inlet, a reaction gas outlet, an inlet gas flow field and an outlet gas flow field; the inlet gas flow field comprises an inlet gas main flow channel and an inlet gas branch flow channel, the outlet gas flow field comprises an outlet gas main flow channel and an outlet gas branch flow channel, the reaction gas inlet is connected with the inlet gas main flow channel, the reaction gas outlet is connected with the outlet gas main flow channel, the outlet gas flow field is distributed at the end of the inlet gas branch flow channel in a mirror image mode, and the outlet gas branch flow channel is gathered and extended to the outlet.

[0031] The inlet gas flow field is determined according to the hierarchical characteristics and distribution rules of natural lightning, and the coverage range is a 90°-angle sector. The flow channel of the inlet gas flow field is composed of multiple straight flow channels, and the inclination angles between the multiple straight flow channels are 15°-45°, and the inclination angle of the inlet gas branch flow channel relative to the main flow channel is 30°-90°.

[0032] The outlet gas flow field is distributed along the diagonal lines of a rectangle, the outlet gas flow channel is composed of straight flow channels, is distributed between the edge of the rectangular bipolar plate and the end of the inlet gas branch flow channel, and the end of the inlet gas branch flow channel has a gap with the outlet gas flow channel on the same side.

[0033] The cross-sectional shape of the inlet gas flow field and the outlet gas flow field is a rectangle, the height is 1 mm, the width of the flow channel at a non-branch position is 1 mm, and the width of the flow channel at a branch position is 1-2 mm.

[0034] A detection method of the lightning-imitating hierarchical fuel cell bipolar plate flow field structure, which comprises the following steps:

[0035] Step one: designing the lightning-imitating hierarchical fuel cell bipolar plate flow field structure: based on the lightning structure, the lightning-imitating hierarchical fuel cell bipolar plate flow field structure is designed, the number of sections and the flow channel area of different lightning-imitating hierarchical fuel cell bipolar plate flow field structures are different, wherein the flow channel area / bipolar plate area of example 1 is 22.5% (as shown in Figure 2 a), the flow channel area / bipolar plate area of example 2 is 26.5% (as shown in Figure 2 b), and the flow channel area / bipolar plate area of example 3 is 30.5% (as shown in Figure 2 c), and the contrast example is a serpentine flow field structure, and the flow channel area / bipolar plate area is 26.5% (as shown in Figure 2 d), which is consistent with example 2.

[0036] Step two: as shown in Figure 1As shown, the three-dimensional geometric model of the biomimetic lightning hierarchical fuel cell bipolar plate and proton exchange membrane fuel cell is established: the two-dimensional plane structure of the biomimetic lightning hierarchical bipolar plate flow field is constructed using Rhino modeling software, the plane structure is composed of multiple straight lines rotating and offsetting, the flow channel cross section is designed as a rectangle of 1mm×1mm, the straight lines are converted into three-dimensional cuboids using lofting, extrusion and other tools, and multiple cuboids are combined and merged through translation, Boolean operation and other methods to build the three-dimensional geometric structure of the biomimetic lightning hierarchical bipolar plate flow field. A cuboid with a size of 40mm×40mm×3mm is established, and the gas inlet and outlet of the bipolar plate flow field are located at the diagonal positions of the cuboid plane, and the bipolar plate component with a surface biomimetic flow field is established by Boolean operation. The three-dimensional geometric models of the gas diffusion layer, the catalyst layer and the proton exchange membrane are established, with sizes of 40mm×40mm×0.3mm, 40mm×40mm×0.02mm and 40mm×40mm×0.05mm respectively. The components are assembled by positioning and moving to form the biomimetic lightning hierarchical fuel cell geometric model.

[0037] Step three, meshing the geometric model of the biomimetic lightning hierarchical fuel cell: import the fuel cell geometric file in step format into ICEM, perform topological inspection on the geometric model, and repair the problems in the geometry. Establish the initial block, then divide the block according to the calculation domain. According to the different components of the fuel cell and the boundary conditions, the block and the geometric model are established. According to the structural characteristics of the geometric model, the block is divided and associated. Set the generation parameters of the geometric grid, establish the grid model of the fuel cell, and adjust the grid parameters according to the grid quality of the geometric model. After the grid quality meets the simulation conditions, the grid is converted into a non-structured grid for application in Fluent simulation operation. Finally, output the grid file in msh format and import it into Fluent for simulation calculation of the performance of the fuel cell and the bipolar plate flow field.

[0038] Step four, simulation of the performance of the biomimetic lightning hierarchical fuel cell and the bipolar plate flow field: import the msh file of the fuel cell into the Fluent module in Ansys, open the proton exchange membrane fuel cell module, and set the fuel cell simulation parameters as shown in Table 1.

[0039] Table 1 Specific parameter table

[0040] Parameter name Value Parameter name Value Anode inlet mass flow (kg / s) 2.0468e-07 Cathode inlet mass flow (kg / s) 3.9231e-06 Anode H2 / O2 component ratio 0.4051 / 0.5948 Cathode O2 / H2O2 component ratio 0.1690 / 0.1948 Operating pressure / Pa 2e+05 Outlet pressure / Pa 0 Operating temperature / K 353 Air temperature / K 353 Hydrogen diffusion coefficient (m 2 / s) 3e-05 Oxygen diffusion coefficient (m 2 / s) 3e-05 Anodic exchange current density (A / m 3 )]]> 2e+09 Cathodic exchange current density (A / m 3 )]]> 1e+05 Anode excess factor 1.5 Cathode excess factor 2 Porosity of diffusion layer 0.5 Porosity of catalytic layer 0.5 Diffusion layer viscous resistance coefficient (1 / m 2 )]]> 1e+12 Membrane molar mass (kg / kmol) 1100 Contact resistance (Ω-m 2 )]]> 2e-06 Open circuit voltage / V 0.95 Water content in reference membrane 0.1 Membrane proton conductivity coefficient 1

[0041] Step five, extracting the performance data of the biomimetic lightning hierarchical fuel cell and the bipolar plate flow field: according to the simulation results, the oxygen content distribution in the gas diffusion layer of the fuel cell with different bipolar plate structures, the pressure distribution in the cathode bipolar plate flow channel, and the water distribution cloud map in the cathode bipolar plate are extracted, such as Figure 3 、 Figure 4 andFigure 5 The simulation results are analyzed as follows: according to the oxygen content distribution in the gas diffusion layer of the fuel cell with different bipolar plate structures, the pressure distribution in the cathode bipolar plate flow channel, and the water distribution cloud in the cathode bipolar plate, it is concluded that compared with the traditional serpentine flow channel bipolar plate fuel cell, the bionic lightning hierarchical bipolar plate can obtain more uniform oxygen content distribution in the gas diffusion layer, improve the power generation stability of the fuel cell, and the shorter gas outlet flow channel can improve the self-drainage performance of the proton exchange membrane fuel cell bipolar plate, so that the water produced by the reaction is discharged as soon as possible, avoiding the waterlogging phenomenon affecting the performance of the fuel cell. The performance simulation of the bionic lightning hierarchical fuel cell bipolar plate with different flow channel areas shows that when the flow channel area is 26.5%, the oxygen distribution in the gas diffusion layer of the fuel cell, the gas pressure in the flow channel, and the water content distribution are better, and the fuel cell performance and the flow field performance of the bipolar plate are more excellent.

Claims

1. A lightning-imitating hierarchical fuel cell bipolar plate flow field channel field structure, characterized in that, include: Reaction gas inlet, reaction gas outlet, inlet flow channel field and outlet flow channel field; the inlet flow channel field includes an inlet main channel and an inlet branch channel, the outlet flow channel field includes an outlet main channel and an outlet branch channel, the reaction gas inlet is connected to the inlet main channel, the reaction gas outlet is connected to the outlet main channel, the outlet flow channel field is distributed at the end of the inlet branch channel in a mirror image distribution, and the outlet branch channels converge and extend to the outlet; The intake airflow field is determined based on the classification characteristics and distribution patterns of natural lightning, and its coverage area is a 90° fan-shaped area. The flow channel of the intake airflow field is composed of multiple sections of straight flow channels, and the inclination angle between the multiple straight flow channels is 15°-45°. The inclination angle of the intake branch flow channel relative to the main flow channel is 30°-90°. The outlet flow channel field is symmetrically distributed along the diagonal line of the rectangle. The outlet flow channel is composed of a straight flow channel and is distributed between the edge of the rectangular bipolar plate and the end of the intake branch channel. There is a gap between the end of the intake branch channel and the outlet flow channel on the same side.

2. The lightning-simulating staged fuel cell bipolar plate flow field pattern structure of claim 1, wherein, The cross-sectional shapes of the inlet and outlet flow passages are both rectangular, with a height of 1 mm. The width of the flow passage at the non-branching position is 1 mm, and the width of the flow passage at the branching position is 1 to 2 mm.

3. A method of inspecting a flow field pattern of a bipolar plate for a simulated lightning hierarchical fuel cell according to claim 1, wherein The steps include: Step 1: Design a lightning-like hierarchical fuel cell bipolar plate flow field structure; Step 2: Establish a three-dimensional geometric model of the bipolar plate and proton exchange membrane fuel cell of the lightning-simulated hierarchical fuel cell; Step 3, meshing the geometric model of the lightning-simulating hierarchical fuel cell; Step 4, simulating the flow field performance of the lightning-like hierarchical fuel cell and bipolar plate; Step 5: Extract the lightning-simulated hierarchical fuel cell and bipolar plate flow field performance data, and analyze different bipolar plate flow field structures based on the performance simulation data.

4. The method of claim 3, wherein the method further comprises: determining the flow field channel pattern of the bipolar plate by comparing the first and second images. In step 2, the three-dimensional geometric model of the bipolar plate of the lightning-simulating hierarchical fuel cell and the proton exchange membrane fuel cell is established as follows: the two-dimensional model of the flow field structure of the lightning-simulating bipolar plate is established using Rhino three-dimensional modeling software, and the three-dimensional geometric model of the bipolar plate of the lightning-simulating hierarchical fuel cell and its flow field structure is established by using extrusion, stretching, and Boolean operation methods, wherein the flow field structure is in close contact with the geometric model of the flow channel structure on the surface of the bipolar plate; according to the size of different components of the proton exchange membrane fuel cell and the bipolar plate structure, a three-dimensional cubic geometric model of the gas diffusion layer, the catalyst layer, and the proton exchange membrane with different structural sizes is established; wherein, the cathode gas diffusion layer (4) and The anode gas diffusion layer (8) contacts one side of the cathode bipolar plate 5 and the anode bipolar plate (7) having a flow channel structure to achieve stable diffusion of the reaction gas in the bipolar plate flow channel; the back sides of the cathode gas diffusion layer (4) and the anode gas diffusion layer (8) contact the cathode catalyst layer (3) and the anode catalyst layer (9) to achieve the reaction gas entering the catalyst layer for reaction; the back sides of the cathode catalyst layer (3) and the anode catalyst layer (9) contact the proton exchange membrane (6) to achieve the migration of hydrogen ions from the anode to the cathode during the reaction; finally, the various components are assembled and connected by means of geometric assembly, and a three-dimensional geometric model of the proton exchange membrane fuel cell in step format is derived.

5. The method of claim 3, wherein the step of detecting the flow field pattern of the bipolar plate of the simulated lightning hierarchical fuel cell is characterized by: In step 3, the grid division of the geometric model of the lightning-imitating staged fuel cell is specifically: the fuel cell geometric file in step format is imported into ICEM, the topological inspection of the geometric model is performed, the problems existing in the geometry are repaired, the initial blocks are established, the blocks are divided according to the calculation domain, the blocks and the geometric model are respectively established according to the different components of the fuel cell and the boundary conditions, and the blocks are divided and associated according to the structural characteristics of the geometric model; The generation parameters of the geometric grid are set, the grid model of the fuel cell is established, the grid parameters are adjusted according to the grid quality of the geometric model, the grid is converted into a non-structural grid after the grid quality meets the simulation conditions, so as to be applied to the Fluent simulation operation; finally, the grid file in msh format is output and imported into Fluent for the simulation calculation of the fuel cell and the bipolar plate flow field performance.

6. The method of detecting a flow field pattern of a bipolar plate of a simulated lightning hierarchical fuel cell according to claim 3, wherein In step 4, the simulation of the fuel cell and the bipolar plate flow field performance is specifically: the msh file of the fuel cell is imported into the Fluent module in Ansys, the proton exchange membrane fuel cell module is opened, and the fuel cell simulation parameters are set, as shown in the following table: Specific parameter table

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