A method for optimizing the contact resistance distribution of a fuel cell

Abstract

The application discloses a kind of fuel cell contact resistance distribution optimization design method, comprising the following steps: according to the actual size of fuel cell component, establish three-dimensional model, divide finite element grid, construct fuel cell assembly interface contact resistance analysis finite element model, then carry out contact analysis, output the contact pressure value on mating surface, according to contact pressure value calculation each node contact resistivity;With the deviation of the ideal distribution of the polar plate-gas diffusion layer interface contact resistivity distribution as the optimization design target, if the optimization design target is less than the threshold value, output the polar plate outer end surface topography data;Otherwise, update the fuel cell assembly interface contact resistance analysis finite element model.The application realizes the optimization of target contact resistivity distribution through the topography design of key assembly interface, avoids the problem of high space and weight ratio of battery assembly structure caused by the traditional method of increasing end plate thickness, can effectively improve the space utilization of fuel cell and reduce the ohmic loss of fuel cell.

Description

Technical Field

[0001] This invention belongs to the field of fuel cell design, specifically relating to a method for optimizing the design of fuel cell contact resistance distribution. Background Technology

[0002] As a device that converts the chemical energy in fuel into electrical energy, fuel cells have promising application prospects in aerospace, automotive and other fields due to their cleanliness, high efficiency, fast start-up and good environmental adaptability.

[0003] A typical hydrogen fuel cell consists of a current collector, bipolar plates, a gas diffusion layer, a catalyst layer, a proton exchange membrane, end plates, and bolts or straps for fixation. The inherent characteristics of a fuel cell—requiring sealed reaction chambers and series connection between units—dictate a structure where the cell is clamped between end plates, with the assembly force acting on the outer edges of these end plates. This assembly structure often leads to bending deformation of the end plates, and the clamping force acting on the outer edges of each layer results in uneven contact resistance at the critical interface between the cell's bipolar plates and the gas diffusion layer. This significantly increases ohmic losses and substantially impacts the actual operating efficiency of the fuel cell.

[0004] Existing battery contact resistance homogenization design methods mainly adopt the approach of increasing the thickness of the end plate. However, the limitation is that the end plate thickness is too large, which occupies too much space and weight, and the optimization effect is limited, thus restricting the improvement of battery efficiency. Summary of the Invention

[0005] The purpose of this invention is to provide a method for optimizing the design of fuel cell contact resistance distribution. By using finite element analysis and optimizing the design of the fuel cell assembly interface morphology, the method aims to homogenize the contact resistance of key fuel cell interfaces or make its distribution approach an ideal distribution, thereby reducing ohmic losses and improving battery performance.

[0006] To achieve the objectives of this invention, the technical solution adopted is as follows:

[0007] A method for optimizing the contact resistance distribution of a fuel cell includes the following steps:

[0008] 1) Establish a three-dimensional model based on the actual dimensions of the fuel cell components;

[0009] 2) Divide the 3D model into finite element meshes and construct a finite element model for analyzing the contact resistance of the fuel cell assembly interface;

[0010] 3) Perform contact analysis on the finite element model of the fuel cell assembly interface, output the contact pressure value on the mating surface, and calculate the contact resistivity of each node based on the contact pressure value;

[0011] 4) Using the deviation between the contact resistivity distribution at the electrode-gas diffusion layer interface and the ideal distribution as the optimization design objective, if the optimization design objective is less than the threshold, output the morphology data of the outer end face of the electrode; otherwise, update the finite element model of the fuel cell assembly interface contact resistance analysis in step 2) and proceed to step 3).

[0012] Furthermore, the contact resistivity of each node is calculated using a contact resistance fractal network model based on the contact pressure value.

[0013] Furthermore, the optimized design objective δ is calculated using the following formula:

[0014]

[0015] Where i is the serial number of the contact node between the electrode and the gas diffusion layer, and n is the total number of contact interface nodes. The deviation of the node contact resistivity from the expected value. This represents the average deviation between the contact resistivity of each node and the target distribution.

[0016] Furthermore, the deviation of the contact resistivity from the expected value is calculated using the following formula:

[0017]

[0018] Where, ρ ie Let ρ be the desired value of the target contact resistivity distribution at the node. i This is the calculated value for the contact resistivity of the node.

[0019] Furthermore, the finite element model for analyzing the contact resistance of the fuel cell assembly interface in step 2) is updated using node coordinate correction.

[0020] Furthermore, the node coordinate correction amount is determined through the following process:

[0021] If the proportion of nodes on the outer end face of the electrode that are not in contact with the current collector to the total number of nodes on the outer end face of the electrode reaches a set value, then the gap between the nodes on the outer end face of the electrode and the current collector is used as the node coordinate correction amount; if the proportion of nodes on the outer end face of the electrode that are not in contact with the current collector to the total number of nodes on the outer end face of the electrode is lower than a set value, then the node coordinate correction amount z1 is used as the node coordinate correction amount.

[0022] The node coordinate correction z1 is calculated by the following formula: Based on the evaluation surrogate value of the contact resistivity of the outer end face node and the range of the deformation of the outer end face of the electrode in the normal direction obtained from the finite element analysis, the node coordinate correction z1 is calculated.

[0023] Furthermore, the node coordinate correction z1 is calculated using the following formula:

[0024]

[0025] Where R is the surrogate value for evaluating the contact resistivity of the outer end face of the electrode plate. max R is the maximum value among all the proxy values ​​evaluated by the nodes. min v is the minimum value among all node evaluation proxy values; v is the range of deformation of the outer end face of the electrode in the normal direction obtained from the finite element analysis; c k To iteratively optimize the rate control parameters.

[0026] Furthermore, the proxy value for evaluating the contact resistivity of the nodes on the outer end face of the electrode is determined through the following process: the nodes of the contact surface between the electrode and the gas diffusion layer of the battery layer with the largest deviation from the ideal distribution of the contact resistivity distribution at the electrode-gas diffusion layer interface are projected along the electrode normal onto the outer end face of the electrode; for the nodes on the outer end face of the electrode, the average value of the contact resistivity projected from the surrounding nodes is used as the proxy value for evaluating the contact resistivity of the nodes on the outer end face of the electrode.

[0027] Furthermore, the evaluation proxy value R of the contact resistivity of the outer end face of the electrode plate is calculated by the following formula;

[0028]

[0029] Where m is the number of node projections within the area surrounding the node on the outer end face of the electrode plate. This represents the deviation between the contact resistivity and the expected value at the outer end face node.

[0030] Furthermore, the range of the value c is set to 0 ≤ c ≤ 0.3.

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

[0032] This invention considers the fuel cell electrode-gas diffusion layer contact interface as a key interface affecting overall performance. Based on the finite element method, it actively designs the contact resistance distribution of this key interface instead of simply homogenizing it. This reduces ohmic losses, improves fuel cell energy efficiency, and reduces the space occupancy of the assembly structure within the fuel cell, thereby promoting the widespread application of fuel cells. Through the design of the key assembly interface morphology, this invention optimizes the target contact resistivity distribution, avoiding the problem of excessive space and weight proportions in the battery assembly structure caused by traditional methods of increasing endplate thickness. This effectively improves the space utilization of the fuel cell and reduces ohmic losses. Furthermore, the design method of this invention separates the design interface and the target interface, avoiding interference between the interface contact resistance optimization design and the electrode flow channel structure design and processing, making the contact resistance optimization design more feasible. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the structure of a fuel cell.

[0034] Figure 2 This is a schematic diagram of the deflection problem of a fuel cell under clamping force.

[0035] Figure 3 This is a flowchart of the optimized design process for the contact resistance distribution of a fuel cell.

[0036] Figure 4 This is a schematic diagram of the grid flow field of the electrode plate.

[0037] Figure 5 This is a diagram of the finite element mesh model of a fuel cell.

[0038] Figure 6 This is a schematic diagram of the projection of the electrode-gas diffusion layer node onto the outer end face of the electrode.

[0039] Figure 7 This is a schematic diagram of the outer surface morphology of the electrode plate optimized according to the embodiment of the fuel cell.

[0040] In the figure, 1 is the end plate, 2 is the current collector, 3 is the electrode plate, 4 is the sealing gasket, 5 is the gas diffusion layer, 6 is the proton exchange membrane, 7 is the outer end face of the electrode plate, 8 is the inner side of the end plate, and 9 is the fuel cell. Detailed Implementation

[0041] To make the objectives, methods, and advantages of this invention clearer, the technical solutions in the embodiments of this invention will be described in more detail below. The described examples are some, but not all, examples of this invention, and are exemplary and intended to explain this invention rather than limit the scope of the invention. The examples of this invention will be described in detail below.

[0042] The present invention provides a method for optimizing the contact resistance distribution of a fuel cell, comprising the following steps:

[0043] 1) Establish a three-dimensional model based on the actual dimensions of the fuel cell components;

[0044] A fuel cell includes an end plate, a current collector, a reaction gas inlet pipe structure, electrode plates 3, a gas inlet and outlet channel, a current outlet structure, and a catalyst layer.

[0045] The end plate is considered as an insulator, and the insulating layer structure between the end plate and the collector plate is ignored; the structure of the gas inlet pipe is simplified, and the gas inlet and outlet channels on the electrode 3 are unified into a grid channel structure; the current outlet structure of the collector plate is ignored, and it is considered as a metal plate that contacts the electrode plate and the end plate respectively; the catalyst layer is considered as part of the gas diffusion layer.

[0046] 2) Divide the 3D model into finite element meshes and construct a finite element model for analyzing the contact resistance of the fuel cell assembly interface;

[0047] 3) Perform contact analysis on the finite element model of the fuel cell assembly interface contact resistance analysis, output the contact pressure value on the mating surface, and calculate the contact resistivity, contact resistance and total interface contact resistance of each node using the contact resistance fractal network model based on the contact pressure value; according to the design requirements, the deviation δ of the contact resistivity distribution of the electrode-gas diffusion layer interface from the ideal distribution is taken as the design target parameter, and the optimization design target is min(δ).

[0048] If the deviation from the ideal distribution of contact resistivity is used for evaluation, then δ=δ1;

[0049]

[0050] Where i is the serial number of the contact node between the electrode and the gas diffusion layer, n is the total number of contact interface nodes, and ρ i This is the calculated value of the nodal contact resistivity. ρ represents the deviation of the contact resistivity from the expected value at that location. ie Let this be the desired value of the target contact resistivity distribution at this node. This represents the average deviation between the contact resistivity of each node and the target distribution.

[0051] 4) Project the nodes of the contact surface between the electrode and the gas diffusion layer of the battery layer with the largest deviation from the ideal distribution of the contact resistivity distribution at the electrode-gas diffusion layer interface onto the outer end face 7 of the electrode along the electrode normal; for the nodes on the outer end face of the electrode, take the average value of the contact resistivity of the surrounding nodes as the proxy value for evaluating the influence of the node on the contact resistance of the electrode-gas diffusion layer, that is, the proxy value R of the contact resistivity evaluation of the nodes on the outer end face of the electrode.

[0052] The contact resistivity evaluation proxy value R of the outer end face node of the electrode plate is calculated as needed by the following formula based on the contact resistivity of the node projection in the polygonal area formed by the outer end face node and its adjacent nodes.

[0053]

[0054] Where m is the number of node projections within the area surrounding the node on the outer end face of the electrode plate. This represents the deviation between the contact resistivity and the expected value at the outer end face node.

[0055] 5) Calculate the node coordinate correction z1 based on the surrogate value R of the contact resistivity of the node on the outer end face of the electrode and the range v of the deformation of the outer end face of the electrode in the normal direction obtained by finite element analysis.

[0056] The nodal coordinate correction z1 on the outer end face of the plate in a single iteration is as follows:

[0057]

[0058] Where R is the surrogate value for evaluating the contact resistivity of the outer end face of the electrode plate. max R is the maximum value among all the proxy values ​​evaluated by the nodes. min v is the minimum value among all node evaluation proxy values; v is the range of deformation of the outer end face of the electrode in the normal direction obtained from the finite element analysis; c k The rate control parameter is set to a value between 0 and 1 for iterative optimization.

[0059] 6) If the proportion of nodes on the outer end face of the electrode that are not in contact with the current collector to the total number of nodes on the outer end face of the electrode reaches the set value c, then the gap z2 between the nodes on the outer end face of the electrode and the current collector is used as the node coordinate correction amount to correct the shape of the outer end face of the electrode; if the proportion of nodes on the outer end face of the electrode that are not in contact with the current collector to the total number of nodes on the outer end face of the electrode is lower than the set value c, then the node coordinate correction amount z1 obtained in step 5) is still used.

[0060] During steps 4) to 6), the design domain can be extended from the outer end face morphology of the electrode plate to the inner side morphology of the end plate.

[0061] The control parameter setting value c for the start gap compensation is taken in the range of 0≤c≤0.3, depending on the actual battery structure complexity.

[0062] 7) Evaluate the optimization design objective δ: If the optimization design objective δ is less than the threshold ε, or the number of optimization iterations k reaches the upper limit of the number of iterations N, then stop the optimization iteration, output and save the topography data of the outer end face of the electrode plate; otherwise, update the finite element model of the fuel cell assembly interface contact resistance analysis constructed in step 2) according to the node coordinate correction obtained in step 6), and proceed to steps 3)-6).

[0063] Example 1

[0064] This invention uses the optimized design of contact resistance distribution in a single-layer proton exchange membrane fuel cell as an example. The fuel cell 9 includes an end plate 1, a current collector 2, electrode plates 3, a sealing gasket 4, a gas diffusion layer 5, a proton exchange membrane 6, and bolts for fixing. Figure 1 As shown in the figure. Among them, the electrode plate 3, the sealing gasket 4, the gas diffusion layer 5, and the proton exchange membrane 6 together form a fuel cell stack unit.

[0065] Under the preload of the bolts, end plate 1 deflects, causing the clamping force to act mainly through the end plate on the outer edge of the battery cell, while the centers of each layer of fuel cell 9 fail to make good contact. Figure 2 As shown, this leads to uneven distribution of battery contact resistance, exacerbates ohmic losses caused by excessive contact resistance inside fuel cell 9, increases power loss of fuel cell 9, and reduces the working efficiency of fuel cell 9.

[0066] The embodiments of this invention take the homogenization of the contact resistance at the critical interface between the fuel cell electrode plate and the gas diffusion layer as the design objective, and perform optimization design with the outer end face of the electrode plate as the design domain. The optimization design process is as follows: Figure 3 As shown, the specific steps are as follows:

[0067] 1) Establish a 3D model based on the actual dimensions of the fuel cell components. Ignore the insulation layer structure between the end plates and the current collector; simplify the structure of the reactant gas inlet pipe; unify the gas inlet and outlet channels on electrode 3 into a grid channel structure, such as... Figure 4 As shown; the current-out structure of the current collector is ignored; the catalyst layer is considered as part of the gas diffusion layer.

[0068] 2) Based on the battery symmetry, using the 1 / 8 scale model of the battery as the object, a finite element mesh is generated, and a finite element model for analyzing the contact resistance of the fuel cell assembly interface is constructed, such as... Figure 5 As shown.

[0069] 3) Perform contact analysis on the finite element model of the fuel cell, output the contact pressure value on the mating surface, and calculate the contact resistivity and contact resistance of each node, and calculate the total contact resistance of the interface; according to the design requirements, the ideal contact resistivity distribution is uniform, so the dispersion of the obtained contact resistance is used to calculate the target deviation δ, and the optimization design target is min(δ).

[0070] The design goal of this embodiment is to homogenize the key interface contact resistance of the battery. The dispersion of the interface contact resistance distribution is evaluated using the following formula:

[0071]

[0072] Where i is the serial number of the contact node between the electrode and the gas diffusion layer, n is the total number of contact interface nodes, and ρ i Let ρ be the contact resistivity of the node. A This represents the average contact resistivity.

[0073] 4) Project the nodes of the contact area between the battery layer with the most uneven contact resistance distribution and the gas diffusion layer along the normal direction onto the outer end face of the electrode, such as... Figure 6 As shown, the average contact resistivity of the nodes projected around the outer end face node is used as the proxy value for evaluating the influence of the node on the contact resistance of the electrode-gas diffusion layer. That is, the proxy value R for evaluating the contact resistivity of the outer end face node of the electrode is calculated as follows:

[0074]

[0075] Where m is the number of node projections in the area surrounding the node on the outer end face of the electrode plate, and ρ i The contact resistivity is the projected value of each node.

[0076] 5) Evaluate the surcharge value R and the range of deformation of the outer end face of the electrode in the normal direction based on the contact resistivity of the nodal contact on the outer end face of the electrode. ν The coordinate correction z1 of the node is calculated as follows: For a single node on the outer end face of the electrode plate, the coordinate correction can be calculated as follows:

[0077]

[0078] Among them, R,R max ,R min The surrogate values ​​for the contact resistivity evaluation of the outer end face node and the maximum and minimum surrogate values ​​among all node evaluation values; v is the range of the electrode deformation in the normal direction obtained from the finite element analysis; c k The rate control parameter is set to 0.2 for iterative optimization.

[0079] 6) If the proportion of nodes on the outer end face of the electrode that are not in contact with the current collector to the total number of nodes on the outer end face of the electrode reaches the set value c (taken as 0.2), the gap z2 between the nodes on the outer end face of the electrode and the current collector is used as the node coordinate correction amount to correct the shape of the outer end face of the electrode. If the proportion of nodes on the outer end face of the electrode that are not in contact with the current collector to the total number of nodes on the outer end face of the electrode is less than c, the coordinate correction amount z1 obtained in step 5) is still used.

[0080] 7) Evaluate the optimization design target parameter δ. If δ≤ε, or the number of optimization iteration steps k satisfies k≥N, then stop the optimization iteration, output and save the topography data of the outer end face of the electrode plate. The condition for stopping the iteration is that ε is 10% of the initial dispersion and N is 1000. Otherwise, update the fuel cell finite element model constructed in step 2) according to the node coordinate correction obtained in step 6) and execute a new finite element analysis process.

[0081] The contact resistance dispersion described in this invention can be characterized by the variance and standard deviation of the contact resistivity on the mating surface, or by the range of the contact resistivity.

[0082] The embodiments involve fuel cells employing the optimized design method of this invention, achieving full-area effective contact at the critical assembly interface between the electrode plate and the gas diffusion layer. Compared to previous endplate thickness optimization results, the total contact resistance at the target contact interface is reduced by 38.9%, effectively reducing ohmic losses in the fuel cell and improving overall battery performance. The optimized outer end face morphology of the fuel cell electrode plate is shown below. Figure 7 As shown.

[0083] The fuel cell electrode-gas diffusion layer contact interface is a key interface affecting overall performance. By actively designing the surface morphology of the outer end face of the electrode, the contact resistance between the fuel cell electrode and the gas diffusion layer can be effectively reduced, thus lowering the ohmic loss of the fuel cell and significantly improving its overall performance. The morphology optimization design method includes steps such as finite element analysis of battery contact resistance distribution, model morphology correction and iterative optimization, and optimization effect evaluation.

[0084] The above embodiments are merely illustrative of the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solutions based on the technical concept proposed in this invention shall also fall within the scope of protection of this invention. Technologies not covered in this invention can be implemented using existing technologies.

Claims

1. A method for optimizing the design of contact resistance distribution in a fuel cell, characterized in that, Includes the following steps: 1) Establish a three-dimensional model based on the actual dimensions of the fuel cell components; 2) Divide the 3D model into finite element meshes and construct a finite element model for analyzing the contact resistance of the fuel cell assembly interface; 3) Perform contact analysis on the finite element model of the fuel cell assembly interface, output the contact pressure value on the mating surface, and calculate the contact resistivity of each node based on the contact pressure value; 4) The deviation between the contact resistivity distribution at the electrode-gas diffusion layer interface and the ideal distribution is used as the optimization design target. If the optimization design target is less than the threshold, the morphology data of the outer end face of the electrode is output. Otherwise, update the finite element model of the fuel cell assembly interface contact resistance analysis in step 2) and proceed to step 3). The finite element model for the contact resistance analysis of the fuel cell assembly interface in step 2) is updated using node coordinate correction. The node coordinate correction is determined through the following process: If the proportion of nodes on the outer end face of the electrode that are not in contact with the current collector to the total number of nodes on the outer end face of the electrode reaches a set value, then the gap between the nodes on the outer end face of the electrode and the current collector is used as the node coordinate correction amount; if the proportion of nodes on the outer end face of the electrode that are not in contact with the current collector to the total number of nodes on the outer end face of the electrode is lower than the set value, then the node coordinate correction amount is used. z 1 is used as a correction value for node coordinates; Node coordinate correction z 1. Calculate the node coordinate correction using the following formula: Based on the evaluation surrogate value of the contact resistivity of the outer end face node and the range of the deformation of the outer end face of the electrode in the normal direction obtained from the finite element analysis. z 1; Node coordinate correction z 1. Calculate using the following formula: in, The proxy value is used to evaluate the contact resistivity of the nodal surface on the outer end face of the electrode plate. Evaluate the maximum value among all the proxy values ​​for all nodes. Evaluate the minimum value among all node proxy values; The range of deformation of the outer end face of the electrode plate in the normal direction, obtained from finite element analysis; To iteratively optimize the rate control parameters; Evaluation of contact resistivity at the outer end face of the electrode plate (proxy value) R Calculate using the following formula; in, This represents the number of node projections within the area surrounding the nodes on the outer end face of the electrode plate. This represents the deviation between the contact resistivity and the expected value at the outer end face node.

2. The fuel cell contact resistance distribution optimization design method according to claim 1, characterized in that, The contact resistivity of each node is calculated using a contact resistance fractal network model based on the contact pressure value.

3. The fuel cell contact resistance distribution optimization design method according to claim 1, characterized in that, Optimize design goals Calculated using the following formula: in, i This represents the serial number of the contact node between the electrode plate and the gas diffusion layer. n This represents the total number of nodes on the interface. The deviation of the node contact resistivity from the expected value. This represents the average deviation between the contact resistivity of each node and the target distribution.

4. The fuel cell contact resistance distribution optimization design method according to claim 3, characterized in that, The deviation of the contact resistivity from the expected value is calculated using the following formula: in, Let the target contact resistivity distribution at the node be the desired value. This is the calculated value for the contact resistivity of the node.

5. The fuel cell contact resistance distribution optimization design method according to claim 1, characterized in that, Setting value c The range is .

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