A design method for under-ridge corner to improve the service conditions of gas diffusion layer

Abstract

The present invention relates to a method for designing a ridge corner for improving the service conditions of a gas diffusion layer, the method comprising: obtaining basic parameters, including the width of the ridge, the thickness of the GDL, and the expected compression of the GDL, assuming that the arc of the ridge corner is AB, the end point A of the arc AB is the tangent point of the ridge corner and the GDL layer, the projection point of the end point B of the arc AB on the GDL layer is C, the distance between points B and C is a, and the distance between points A and C is b; constructing a GDL compression simulation analysis model, setting a as a fixed value, and obtaining the contact pressure of the upper surface of the GDL corresponding to different b values; determining the optimal value of b according to the corresponding relationship between the maximum contact pressure of the upper surface of the GDL and the b value; and determining the radius of the ridge corner according to the optimal value of b. Compared with the prior art, the present invention can eliminate the local stress concentration under the ridge, improve the service conditions, and extend the service life, while ensuring sufficient effective contact between the bipolar plate and the gas diffusion layer.

Description

Technical Field

[0001] The invention relates to the technical field of fuel cells, and in particular to a method for designing a ridge corner for improving the service conditions of a gas diffusion layer. Background Art

[0002] As global energy develops towards low-carbonization, fuel cell technology has received more and more attention. Fuel cells are mainly composed of bipolar plates (BPP), gas diffusion layers (GDL), catalyst layers, proton exchange membranes, etc. Their performance and service life depend on the material transport and electrical and thermal conductivity within the gas diffusion layer (GDL). Existing studies have shown that under assembly pressure, the gas diffusion layer is embedded in the flow channel, and stress concentration is formed at the corner under the ridge, showing significant uneven deformation. Local stress concentration will cause carbon fiber breakage, affect the discharge of generated water from the GDL and electrical and thermal conductivity, and uneven deformation will affect the material transport in the gas diffusion layer. Although studies have shown that increasing the radius of the corner under the ridge can effectively alleviate the local stress concentration phenomenon, due to the limited width of the ridge, in order to ensure good contact between the fuel cell bipolar plate and the gas diffusion layer, the traditional fuel cell ridge corner design such as Figure 1 As shown, A is the end point of the corner under the ridge, A is the tangent point between the corner under the ridge and the upper surface of the gas diffusion layer, B is the starting point of the corner under the ridge, C is the vertical projection point of point A on the gas diffusion layer, the distance between points B and C is a, the distance between points A and C is b, a is the expected compression of GDL, and in the design of the corner under the ridge of traditional fuel cells, b is directly designed to be equal to a. Under this design method, the radius of the corner under the ridge is very small, and it is not possible to effectively avoid local stress concentration under the ridge and improve uneven deformation. Summary of the invention

[0003] The purpose of the present invention is to overcome the defects of the above-mentioned prior art and provide a method for designing the under-ridge corner to improve the service conditions of the gas diffusion layer.

[0004] The purpose of the present invention can be achieved by the following technical solutions:

[0005] A method for designing a ridge corner for improving the service condition of a gas diffusion layer, the method comprising:

[0006] Get basic parameters, including ridge width, GDL thickness, and expected GDL compression. Assume that the arc of the ridge corner is AB, the endpoint A of arc AB is the tangent point between the ridge corner and the GDL layer, the projection point of the endpoint B of arc AB on the GDL layer is C, the distance between points B and C is a, and the distance between points A and C is b;

[0007] A GDL compression simulation analysis model was constructed, a was set as a fixed value, and the contact pressure on the GDL upper surface corresponding to different b values ​​was obtained;

[0008] According to the corresponding relationship between the maximum contact pressure on the upper surface of the GDL and the b value, the optimal value of b is determined;

[0009] The radius of the corner under the ridge is determined according to the optimal value of b.

[0010] Preferably, a is set equal to the amount of compression expected for the GDL.

[0011] Preferably, constructing the GDL compression simulation analysis model specifically includes: setting the length of b to be n times of a, n=1-6, using arc AB as the corner under the ridge to determine the corner radius, and obtaining the GDL compression simulation analysis models under different b values.

[0012] Preferably, the optimal value of b is determined in the following manner: the size of b corresponding to the minimum maximum contact pressure on the upper surface of the GDL is selected as the optimal value of b.

[0013] Preferably, the corner radius under the ridge is obtained by connecting points A and B, drawing a perpendicular bisector l1 of line segment AB, drawing a perpendicular line l2 of line segment AC through point A, l1 and l2 intersecting at point O, and the length of line segment OA is the corner radius under the ridge.

[0014] Preferably, when constructing the GDL compression simulation analysis model, a correspondence table between the ridge corner radius and the b value is constructed, and then the ridge corner radius is determined according to the optimal value of b by looking up the table.

[0015] Compared with the prior art, the present invention has the following advantages:

[0016] (1) The present invention increases the b value to eliminate the local stress concentration under the ridge, reduce the risk of fiber breakage in the GDL, and alleviate the uneven deformation of the GDL under compression, which is beneficial to the uniformity of mass and heat transfer in the GDL, improves its service conditions, and prolongs its service life. At the same time, the value of b cannot be increased indefinitely. The optimal value of b is obtained by simulation, which can ensure that there is sufficient effective contact between the BPP and the GDL, and ensure electrical and thermal conductivity at the interface;

[0017] (2) The present invention analyzes the contact pressure on the upper surface of the GDL corresponding to different b values. As the b value increases, the local stress concentration phenomenon under the ridge is gradually alleviated. At the same time, the maximum contact pressure decreases first and then increases as the b value increases. The value of b is optimized by selecting the size of b corresponding to the minimum maximum contact pressure on the upper surface of the GDL as the optimal value of b. This method ensures the accuracy of the optimization. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 Schematic diagram of the design for the conventional fuel cell under-ridge corner;

[0019] Figure 2It is a schematic flow chart of a method for designing a ridge corner for improving the service conditions of a gas diffusion layer according to the present invention;

[0020] Figure 3 A schematic diagram of the design of the under-ridge corner of the fuel cell of the present invention;

[0021] Figure 4 Schematic diagram of the change of contact pressure on the upper surface of GDL with displacement under different b values;

[0022] Figure 5 Schematic diagram of the change of the maximum contact pressure on the upper surface of the GDL under different b values ​​of the present invention;

[0023] Figure 6 Schematic diagram of mises stress of GDL before and after optimization;

[0024] Figure 7 Schematic diagram of the maximum nominal principal strain of GDL before and after optimization.

[0025] In the figure, 1 is a bipolar plate and 2 is a gas diffusion layer. DETAILED DESCRIPTION

[0026] The present invention is described in detail below in conjunction with 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.

[0027] Example

[0028] like Figure 2 As shown, this embodiment provides a method for designing a ridge corner to improve the service conditions of a gas diffusion layer, the method comprising:

[0029] Get basic parameters, including ridge width, GDL thickness, and expected GDL compression. Let the arc of the ridge corner be AB, the endpoint A of arc AB be the tangent point between the ridge corner and the GDL layer, the projection point of the endpoint B of arc AB on the GDL layer be C, the distance between points B and C be a, and the distance between points A and C be b. Set a to be equal to the expected GDL compression.

[0030] A GDL compression simulation analysis model was constructed, a was set as a fixed value, and the contact pressure on the GDL upper surface corresponding to different b values ​​was obtained;

[0031] According to the corresponding relationship between the maximum contact pressure on the upper surface of the GDL and the b value, the optimal value of b is determined;

[0032] The radius of the corner under the ridge is determined according to the optimal value of b.

[0033] The specific steps of constructing the GDL compression simulation analysis model are as follows: setting the length of b to be n times of a, n=1-6, using arc AB as the corner under the ridge to determine the corner radius, and obtaining the GDL compression simulation analysis models under different b values. Figure 3 As shown, the radius of the corner under the ridge is obtained by the following method: connect points A and B, make a perpendicular bisector l1 of line segment AB, make a perpendicular line l2 of line segment AC through point A, l1 and l2 intersect at point O, and the length of line segment OA is the radius of the corner under the ridge. When b = a, it is the traditional design method of the corner under the ridge.

[0034] The optimal value of b is determined by the following method: the value of b corresponding to the minimum maximum contact pressure on the upper surface of the GDL is selected as the optimal value of b. When constructing the GDL compression simulation analysis model, a corresponding table between the ridge corner radius and the b value is constructed, and then the ridge corner radius is determined according to the optimal value of b by looking up the table. As shown in Table 1, the corresponding table of b and the ridge corner radius R shows that under a certain assembly pressure, as b increases, the ridge corner radius gradually increases.

[0035] Table 1 Correspondence table between b and R

[0036] b / mm 0.04 0.08 0.12 0.14 0.16 0.20 0.24 R / mm 0.04 0.09 0.2 0.26 0.34 0.52 0.74

[0037] The design example of the corner under the ridge of a fuel cell bipolar plate shown in this embodiment is as follows. The initial geometric dimensions include the expected compression a = 0.04 mm, the ridge width w rib =0.5mm, GDL thickness t GDL =0.19mm; the length of b is 1 to 6 times of a, and the sub-ridge turning angle R gradually increases with the maximum of b.

[0038] exist Figure 3 A uniformly distributed pressure P is applied to the upper edge of the bipolar plate, and the two sides and the lower edge of the gas diffusion layer are set as symmetrical boundary conditions. The contact pressure on the upper edge of the GDL is obtained by simulation calculation as follows: Figure 4 As the b value increases, the local stress concentration under the ridge gradually decreases; when b = 6a, the local stress concentration disappears. The schematic diagram of the change of the maximum contact pressure on the upper surface of the GDL is shown in Figure 5 As shown in the figure, the contact pressure under the ridge decreases first and then increases with the b value. According to the variation trend of the maximum contact pressure on the upper surface of the GDL, when b=4a=0.16mm, the maximum contact pressure on the upper surface of the GDL is the smallest, and the corresponding corner radius under the ridge R=0.34mm is the optimal design value under this specific implementation.

[0039] The mises stress of GDL before and after optimization is as follows Figure 6 As shown in the figure, the maximum nominal principal strain of GDL before and after optimization is as follows: Figure 7As shown in the figure: the mises stress disappears in the stress concentration area at the corner under the ridge, and is replaced by a smooth transition from the high stress area under the ridge to the low stress area under the groove; the maximum mises stress decreases from 0.6316MPa to 0.4645MPa, a decrease of 26.5%; the maximum nominal principal strain decreases from 0.22 to 0.14, a decrease of 36%. Through the above analysis, it can be seen that the under-ridge optimization design method demonstrated by the present invention can significantly alleviate the uneven deformation of GDL, improve the service conditions of GDL, and extend its service life.

[0040] The above embodiments are merely examples and do not limit the scope of the present invention. These embodiments can also be implemented in various other ways, and various omissions, substitutions, and changes can be made without departing from the technical concept of the present invention.

Claims

1. A method for designing a ridge corner to improve the service conditions of a gas diffusion layer, characterized in that: The method includes: Get basic parameters, including ridge width, GDL thickness, and expected GDL compression. Assume that the arc of the ridge corner is AB, the endpoint A of arc AB is the tangent point between the ridge corner and the GDL layer, the projection point of the endpoint B of arc AB on the GDL layer is C, the distance between points B and C is a, and the distance between points A and C is b; A GDL compression simulation analysis model was constructed, a was set as a fixed value, and the contact pressure on the GDL upper surface corresponding to different b values ​​was obtained; According to the corresponding relationship between the maximum contact pressure on the upper surface of the GDL and the b value, the optimal value of b is determined; Determine the corner radius under the ridge according to the optimal value of b; The optimal value of b is determined by: selecting the value of b corresponding to the minimum maximum contact pressure on the upper surface of the GDL as the optimal value of b; When constructing the GDL compression simulation analysis model, a corresponding table between the ridge corner radius and the b value is constructed, and then the ridge corner radius is determined according to the optimal value of b by looking up the table.

2. A method for designing a ridge corner for improving the service condition of a gas diffusion layer according to claim 1, characterized in that: Set a equal to the amount of compression you want in GDL.

3. A method for designing a ridge corner for improving the service condition of a gas diffusion layer according to claim 2, characterized in that: The specific steps of constructing the GDL compression simulation analysis model are as follows: the length of b is set to be n times of a, n=1-6, arc AB is used as the corner under the ridge to determine the corner radius, and the GDL compression simulation analysis models under different b values ​​are obtained respectively.

4. A method for designing a ridge corner for improving the service condition of a gas diffusion layer according to any one of claims 1 to 3, characterized in that: The corner radius under the ridge is obtained as follows: connect points A and B, draw the perpendicular bisector l1 of line segment AB, draw the perpendicular line l2 of line segment AC through point A, l1 and l2 intersect at point O, and the length of line segment OA is the corner radius under the ridge.

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