A method for designing stress uniformity of a fuel cell bipolar plate

Abstract

The application discloses a design method of stress uniform distribution of a fuel cell bipolar plate, and comprises the following steps: putting forward the stress uniform distribution performance requirement of a fuel cell stack bipolar plate; designing a hydrogen fuel cell end plate model; determining the total number N of the fuel cell stack bipolar plates; designing a model of the bipolar plate with protrusions according to the total number N of the fuel cell stack bipolar plates, and the design parameters comprise the protrusion size and the number of protrusions; performing finite element simulation analysis on the improved design of the fuel cell stack structure, extracting the stress borne by all the bipolar plates for chart analysis; setting evaluation criteria; according to the chart analysis, confirming whether the stress uniform distribution performance requirement and the evaluation criteria are met, if yes, calculating the maximum stress of the first piece of the bipolar plate with protrusions and the last piece of the bipolar plate with protrusions, and if not, returning to the step of designing the model of the protrusion bipolar plate; the stress borne by the bipolar plate in the application is more uniform, and the slippage of the bipolar plate in the middle part of the fuel cell stack during use is reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of hydrogen fuel cell polar plate design, and particularly to a design method for stress uniform distribution of fuel cell bipolar plates. BACKGROUND

[0002] Fuel cells are power generation devices that directly convert the chemical energy of hydrogen and oxygen into electrical energy, and do not cause any impact on the environment. Fuel cells are gradually receiving more attention. The membrane electrode layer in each cell unit of a fuel cell requires a pair of conductive separators, which are referred to as electrode plates. The stress on the electrode plates affects the service life of the entire cell. In the existing fuel cell structure technology, the bipolar plates at both ends of the fuel cell stack are subjected to a large stress, while the bipolar plates in the middle part of the fuel cell stack are often subjected to a small stress, which causes the bipolar plates in the middle part to slip during use, thereby reducing the service life and use efficiency of the fuel cell stack. SUMMARY

[0003] This section is intended to summarize some aspects of the embodiments of the present application and briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this section and the abstract and title of the specification to avoid obscuring the purpose of this section, the abstract and the title, and such simplifications or omissions cannot be used to limit the scope of the present application.

[0004] In view of the above-mentioned problems existing in the existing fuel cell, the present application is proposed.

[0005] Therefore, the present application provides a design method for stress uniform distribution of fuel cell bipolar plates, which can design a fuel cell with stress uniform distribution.

[0006] To solve the above technical problems, the present application provides the following technical solutions: comprising the following steps,

[0007] Proposing performance requirements for stress uniform distribution of bipolar plates of a fuel cell stack;

[0008] Designing a model of a hydrogen fuel cell end plate;

[0009] Determining the total number N of bipolar plates of the fuel cell stack;

[0010] Designing a model of a bipolar plate with protrusions according to the total number N of bipolar plates of the fuel cell stack, and the design parameters include the size of the protrusions and the number of protrusions;

[0011] Performing finite element simulation analysis on the improved design of the fuel cell stack structure, and extracting the stress on all bipolar plates for chart analysis;

[0012] Setting evaluation criteria;

[0013] If the stress uniformity performance requirement and evaluation criterion are met according to the chart analysis, the maximum stress of the first and last bipolar plates with protrusions is calculated, and if not, the step of designing the model of the protrusion bipolar plate is returned.

[0014] As a preferred solution of the fuel cell bipolar plate stress uniformity design method of the present application, the outer surface of the end plate is outwardly protruded.

[0015] As a preferred solution of the fuel cell bipolar plate stress uniformity design method of the present application, the end plate is arranged with bolt holes, and the bolt holes gradually increase in height from the two ends of the end plate in the direction of the center.

[0016] As a preferred solution of the fuel cell bipolar plate stress uniformity design method of the present application, the maximum height difference of the bolt holes is 14.88 mm.

[0017] As a preferred solution of the fuel cell bipolar plate stress uniformity design method of the present application, the radius of curvature R of the outward protrusion of the end plate is 1760 mm, and the height AH is 12 mm.

[0018] As a preferred solution of the fuel cell bipolar plate stress uniformity design method of the present application, the N bipolar plates are composed of i first bipolar plates and N-i second bipolar plates, and the two ends of the second bipolar plate have a connecting protrusion beyond the outer edge of the first bipolar plate.

[0019] As a preferred solution of the fuel cell bipolar plate stress uniformity design method of the present application, the thickness Ah of the single-side outward protrusion of the second bipolar plate is evaluated as a percentage of the original thickness h of the bipolar plate, and the total number N of the bipolar plates is different, the number of the second bipolar plates is different, and the percentages are different.

[0020] As a preferred solution of the fuel cell bipolar plate stress uniformity design method of the present application, when the total number N of the bipolar plates is 20, there is one second bipolar plate, the thickness h of the first bipolar plate is 4 mm, the percentage is 15%, and from one end of the cell stack in the length direction to the other end in the length direction, one second bipolar plate is inserted every 9 first bipolar plates.

[0021] As a preferred solution of the fuel cell bipolar plate stress uniformity design method of the present application, when the total number N of the bipolar plates is 40, there are three second bipolar plates, the thickness h of the first bipolar plate is 4 mm, the percentage is 15%, and from one end of the cell stack in the length direction to the other end in the length direction, one second bipolar plate is inserted every 9 first bipolar plates.

[0022] As a preferred solution of the design method for stress distribution of the fuel cell bipolar plate, when the total number of the bipolar plates N is 81, there are 7 second bipolar plates, the thickness of the first bipolar plate is 4mm, the percentage is 25%, and every 9 first bipolar plates are inserted with one second bipolar plate from one end to the other end of the length direction of the fuel cell stack.

[0023] The present application has the following beneficial effects: the present application improves the structure of the fuel cell stack, increases the clamping force of the bipolar plates in the middle part, makes the stress distribution of the bipolar plates tend to be the same level, makes the stress of the bipolar plates more uniform, reduces the slippage of the bipolar plates in the middle part of the fuel cell stack during use, and prolongs the service life of the fuel cell stack. BRIEF DESCRIPTION OF DRAWINGS

[0024] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed in the embodiment description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor. Among them:

[0025] Figure 1 It is a fuel cell stack model schematic diagram when the number of bipolar plates in the present application is 20.

[0026] Figure 2 It is a fuel cell stack model schematic diagram when the number of bipolar plates in the present application is 40.

[0027] Figure 3 It is a fuel cell stack model schematic diagram when the number of bipolar plates in the present application is 81.

[0028] Figure 4 It is a model schematic diagram of the end plate in the present application.

[0029] Figure 5 It is a bolt hole distribution schematic diagram of the end plate in the present application.

[0030] Figure 6 It is a model schematic diagram of the second bipolar plate in the present application.

[0031] Figure 7 It is a front view of the second bipolar plate in the present application.

[0032] Figure 8 It is a stress simulation maximum stress scatter plot of each bipolar plate when N=20 in the present application.

[0033] Figure 9 It is a stress simulation maximum stress scatter plot of each bipolar plate when N=40 in the present application.

[0034] Figure 10 Figure 20 is a stress simulation of each plate for the fuel cell stack with N = 40.

[0035] Figure 11 Figure 21 is a schematic diagram of the original structure (without protrusions) model of the fuel cell stack.

[0036] Figure 12 Figure 22 is a stress simulation of each plate for the original structure (without protrusions) fuel cell with N = 20.

[0037] Figure 13 Figure 23 is a stress simulation of each plate for the original structure (without protrusions) fuel cell with N = 40.

[0038] Figure 14 Figure 24 is a stress simulation of each plate for the original structure (without protrusions) fuel cell with N = 81.

[0039] Figure 15 Figure 25 is a pressure application method for the fuel cell stack model.

[0040] Wherein, 100 end plate, 101 bolt hole, 200 second bipolar plate, 300 first bipolar plate. DETAILED DESCRIPTION

[0041] In order to make the above objectives, features and advantages of the present application more apparent, specific embodiments of the present application will be described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without creative work should fall within the scope of protection of the present application.

[0042] In the following description, a large number of specific details are set forth in order to facilitate a thorough understanding of the present application, but the present application can also be implemented in other ways different from those described herein, and those skilled in the art can make similar generalizations without departing from the spirit of the present application, therefore the present application is not limited to the specific embodiments disclosed below.

[0043] Secondly, the "one embodiment" or "embodiment" referred to herein can include specific features, structures or characteristics contained in at least one implementation of the present application. "In one embodiment" appearing in different places in the specification does not mean the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments.

[0044] The present application is described in detail in conjunction with the schematic diagram, in the detailed description of the embodiments of the present application, for the convenience of description, the cross-sectional view of the device structure will be partially enlarged without the general proportion, and the schematic diagram is only an example, which should not limit the scope of protection of the present application. In addition, the three-dimensional spatial dimensions of length, width and depth should be included in actual production.

[0045] Meanwhile, in the description of the present application, it should be noted that the terms "upper, lower, inner and outer" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, which is only for the convenience of describing the present application and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, therefore cannot be understood as a limitation on the present application. In addition, the terms "first, second or third" are only for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0046] Unless otherwise specifically defined and limited in the present application, the terms "mounting, connecting, connecting" should be broadly understood, for example: it can be fixed connection, detachable connection or integral connection; It can also be mechanical connection, electrical connection or direct connection, it can also be indirectly connected through intermediate medium, or it can be the communication between two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0047] Embodiment 1

[0048] Reference Figure 1 、 Figures 5-8 、 Figure 12 and Figure 15 , the present embodiment of the invention provides a design method for stress distribution of fuel cell bipolar plate, the designed fuel cell stack structure makes the clamping force of the middle part of the bipolar plate increase, the stress distribution of the bipolar plate tends to be on the same horizontal line, the stress of the bipolar plate is more uniform, reduces the slip of the bipolar plate in the middle part of the fuel cell stack during use, and prolongs the service life of the fuel cell stack.

[0049] A design method for stress distribution of fuel cell bipolar plate, comprising the following steps,

[0050] S1, the performance requirement of stress distribution of fuel cell stack bipolar plate is proposed;

[0051] S2, design the model of hydrogen fuel cell end plate;

[0052] S3, determine the total number N of fuel cell stack bipolar plates;

[0053] S4, design the model of bipolar plate with protrusions according to the total number N of fuel cell stack bipolar plates, the design parameters include the size of the protrusions and the number of protrusions;

[0054] S5, finite element simulation analysis is performed on the improved design of the fuel cell stack structure, and the stress borne by all bipolar plates is extracted for chart analysis;

[0055] S6, evaluation criteria are set;

[0056] S7, whether the stress uniformity performance requirement and the evaluation criteria are met is confirmed according to the chart analysis, if yes, the process goes to step S8, otherwise, the process returns to step S4;

[0057] S8, the maximum stress of the first raised bipolar plate and the last raised bipolar plate is calculated, and the calculation formula of the stress is:

[0058]

[0059] wherein, σ H is the contact stress (Mpa), F n is the normal force (N), L is the contact line length (mm), R1 is the curved surface radius (mm), E1 and E2 are the elastic modulus of the contact surface materials (MPa), and μ1 and μ2 are the Poisson's ratios of the contact surface materials.

[0060] Further, the outer surface of the end plate is outwardly raised, a plurality of bolt holes are arranged on the end plate, and the bolt holes gradually increase in height from the two ends of the end plate in the direction of the center; the maximum height difference of the bolt holes is 14.88 mm, the radius R of the outwardly raised arc of the end plate is 1760 mm, and the height ΔH is 12 mm.

[0061] Further, the N bipolar plates are composed of i first bipolar plates and N-i second bipolar plates, and the two ends of the second bipolar plate have a connecting protrusion beyond the outer edge of the first bipolar plate.

[0062] Further, the thickness Δh of the outwardly raised single side of the second bipolar plate is taken as the percentage of the original thickness h of the bipolar plate as the evaluation standard, the total number N of the bipolar plates is different, the number of the second bipolar plates contained is different, and the percentages are different; in the embodiment, the total number N of the bipolar plates is 20, there is one second bipolar plate in the 20 bipolar plates, the thickness h of the first bipolar plate is 4 mm, and the percentage is 15%.

[0063] The fuel cell bipolar plates with N=20 are simulated using the finite element simulation analysis software, the data obtained after the simulation are compared with the data obtained from the original structure (without second bipolar plate) fuel cell, and the maximum stress of the first raised bipolar plate and the last raised bipolar plate is verified for the second time by using a mathematical model, that is, the improved results are compared by using scientific demonstration means to verify the real effect of the method.

[0064] For a fuel cell with N=20 electrodes, according to step S2, the end plate model is designed with a 60% bulge on one side (ΔH=12mm), a bulge radius of R=1760mm, and bolt hole heights distributed in a stepped manner, with a maximum height difference of 14.88mm. According to step S4, a bulging bipolar plate model is designed, and a bipolar plate with a 15% bulge (Δh=0.6mm) is inserted, according to... Figure 15 The diagram shows that a pressure of 500 N is applied to each bolt hole, i.e., F. n =500N. According to steps S5 and S6, the scatter plot of the maximum stress of each bipolar plate of the fuel cell stack after finite element simulation is as follows. Figure 8 As shown, the deviation coefficient ε is used for judgment.

[0065] Given σ max =2.71 MPa; σ min =1.81 MPa;

[0066] It is assumed that the stress distribution of the bipolar plates in the fuel cell stack is within a reasonable range, satisfying the stress uniformity requirement; from the comparison... Figure 12 It can be seen that the maximum stress distribution of the bipolar plates in the improved fuel cell stack is within a reasonable range, and the stress is relatively increased, indicating that the bipolar plates in the fuel cell stack satisfy the requirements of clamping and stress uniformity.

[0067] Then, according to step S8, verify the stress σ on the second bipolar plate again. H In the formula, F n =500N; When the bipolar plate protrudes by 15%, the radius of the protrusion arc of the bipolar plate is R1 = 35535.2mm; Since the second bipolar plate is in planar contact with the first bipolar plate, R2 = +∞; L = 96.1mm; The plate material is simulated using structural steel, so E1 = E2 = 2.06 × 10 5 MPa; Poisson's ratio μ1=μ2=0.3;

[0068] By substituting the known parameters into the stress calculation formula, the stress σ on the second bipolar plate can be estimated. H , σ H =2.29MPa;

[0069] The simulation results of the second bipolar plate show the maximum stress σ'. H =1.82 MPa, compared with the result σ calculated using Hertz's formula. H In comparison, the simulation results show that the maximum stress σ' H The pressure is too low because the protruding bipolar plate is located in the fuel cell stack, and the end plate and part of the non-protruding bipolar plate offset some of the pressure. In the simulation, the actual pressure on the second bipolar plate is less than 500N.

[0070] Example 2

[0071] Referring to Figure 2 , Figures 4-7 , Figure 9 , Figure 13 and Figure 15 , in order to verify the technical effects adopted in the method, the N=40 hydrogen fuel cell plates are simulated by using finite element simulation analysis software, and the data obtained after simulation is compared with the data obtained by the original structure (without the second bipolar plate) fuel cell. At the same time, the maximum stress of the first and last convex bipolar plates is verified by using mathematical model, that is, the improved results are compared by using scientific demonstration method, so as to verify the real effect of the method.

[0072] Among the 40 bipolar plates, there are 3 second bipolar plates, the thickness h of the first bipolar plate is 4mm, and the percentage is 15%.

[0073] According to step S2, the end plate model is designed to be single convex 60%(△H=12mm), the convex arc radius is R=1760mm, the bolt hole height is ladder distribution, and the maximum height difference of the bolt hole is 14.88mm. According to step S4, the convex bipolar plate model is designed, and 3 convex 15%(△h=0.6mm) bipolar plates are inserted, that is, one convex bipolar plate is inserted every 9 bipolar plates. According to the method shown in Figure 15 , 500N pressure is applied to each bolt hole, that is, F n =500N. Further, according to steps S5 and S6, the maximum stress scatter diagram of each bipolar plate of the fuel cell stack after finite element simulation is shown in Figure 9 , and the deviation coefficient ε is used for judgment:

[0074] It is known that σ max =2.82Mpa; σ min =1.61Mpa;

[0075] It is considered that the stress of the bipolar plate in the fuel cell stack meets the evaluation standard, that is, it meets the stress uniformity. By comparing Figure 13 , it can be seen that the maximum stress of the improved bipolar plate of the fuel cell stack is distributed in a reasonable range, and the stress is relatively improved, which shows that the bipolar plate in the fuel cell stack meets the clamping and stress uniformity.

[0076] According to step S8, the stress σ H of the first and third second bipolar plates is verified again:

[0077]

[0078] In the formula, F n= 500 N; when the bipolar plate is raised by 15%, the radius of curvature of the raised arc of the bipolar plate R1 = 35535.2 mm; since the raised bipolar plate is in contact with the flat bipolar plate, R2 = +∞; L = 96.1 mm; the bipolar plate material is simulated using structural steel, so E1 = E2 = 2.06 x 10 5 MPa; Poisson's ratio μ1 = μ2 = 0.3;

[0079] The known parameters are brought into the above formula to estimate the stress σ H experienced by the second bipolar plate of the first piece and the raised bipolar plate of the third piece

[0080] σ H = 2.29 MPa;

[0081] The maximum stress σ' H1 of the simulation result of the first raised bipolar plate is 1.96 MPa, and the maximum stress σ' H3 of the simulation result of the third raised bipolar plate is 2.03 MPa, which is smaller than the calculation result σ H of the Hertz formula, and the maximum stress σ' H of the simulation result is smaller, which is because the raised bipolar plate is located in the fuel cell stack, and the end plate and part of the bipolar plate offset part of the pressure, and in the simulation, the actual pressure received by the raised bipolar plate is smaller than 500 N.

[0082] The maximum stress of the second piece of the second bipolar plate is estimated, and since the end plate and part of the bipolar plate offset most of the pressure, the intermediate pressure F n is small, and there will be a large deviation when calculated using the above formula.

[0083] Example 3

[0084] Referring to Figures 3-7 , Figure 10 , Figure 14 and Figure 15 , the third embodiment of the present application uses finite element simulation analysis software to simulate N = 81 pieces of hydrogen fuel cell bipolar plates, and compares the data obtained after simulation with the data obtained from the original structure (without second bipolar plate) fuel cell, and at the same time, uses a mathematical model to perform a second verification of the maximum stress of the first raised bipolar plate and the last raised bipolar plate, i.e. to compare the improved results by scientific demonstration means, in order to verify the real effect of the method.

[0085] When the total number of bipolar plates N is 81, there are 7 pieces of second bipolar plates in the 81 pieces of bipolar plates, the thickness h of the first bipolar plate is 4 mm, the percentage is 25%, and from one end of the cell stack in the length direction to the other end in the length direction, every 9 pieces of first bipolar plate inserts a piece of second bipolar plate.

[0086] According to step S2, the end plate model is designed with a single side protrusion of 60% (△H=12mm), the protrusion arc radius is R=1760mm, the bolt hole height is in a step distribution, the maximum height difference of the bolt hole is 14.88mm, according to step S4, the protrusion bipolar plate model is designed, 7 pieces of protrusion 25% (△h=1mm) bipolar plates are inserted, i.e. every 9 pieces of bipolar plates are inserted with a piece of protrusion bipolar plate, and 500N pressure is applied to each bolt hole according to the formula F Figure 15 n =500N, further, according to steps S5 and S6, the maximum stress scatter diagram of each bipolar plate of the fuel cell stack is obtained after finite element simulation, as shown in the formula Figure 10 , and the deviation coefficient ε is used for judgment:

[0087] It is known that σ max =3.65Mpa; σ min =0.84Mpa;

[0088] The stress distribution of the bipolar plate in the fuel cell stack is within a reasonable range, and the stress distribution is uniform; by comparison Figure 14 It can be seen that the maximum stress distribution of the improved bipolar plate of the fuel cell stack is within a reasonable range, and the stress is relatively improved, which indicates that the bipolar plate in the fuel cell stack meets the clamping and stress distribution.

[0089] According to step S8, the stress σ H of the first and seventh second bipolar plates can be verified again according to the mathematical model:

[0090]

[0091] In the formula, F n =500N; when the bipolar plate protrusion is 25%, the bipolar plate protrusion arc radius R1=21321.5mm; since the protrusion bipolar plate is in contact with the non-protrusion bipolar plate, R2=+∞; L=96.1mm; the bipolar plate material uses structural steel for simulation, so E1=E2=2.06×10 5 MPa; Poisson's ratio μ1=μ2=0.3;

[0092] The known parameters are brought into the formula to estimate the stress σ H of the first and seventh second bipolar plates:

[0093] σ H =2.96MPa;

[0094] The maximum stress σ' H1 of the first protrusion bipolar plate simulation result is 2.91MPa, and the maximum stress σ' H3 ​= 2.15 MPa, and the calculated result of the Hertz formula σ H In comparison, the maximum stress σ' H The simulation result is smaller, because the convex bipolar plate is located in the fuel cell stack, and the end plate and part of the bipolar plate offset part of the pressure, so that the actual pressure received by the convex bipolar plate is smaller than 500 N during simulation;

[0095] If the maximum stress of the 2nd-6th convex bipolar plate is to be estimated, because the end plate and part of the bipolar plate offset most of the pressure, the middle pressure F n is smaller, and there will be a larger deviation when using the Hertz formula to calculate.

[0096] As can be seen from the above examples, the bipolar plate of the fuel cell stack designed by the method of the present application can significantly improve the clamping property and stress distribution of the bipolar plate of the fuel cell stack, and provides a basis for the design of the clamping structure of the fuel cell stack.

[0097] It should be noted that the above examples are only used to illustrate the technical solutions of the present application and are not limiting. Although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present application, and all should be covered in the scope of the claims of the present application.

Claims

1. A method of designing a fuel cell bipolar plate for stress uniformity, the method comprising: The method comprises the following steps, ​ Proposing stress uniformity performance requirements for fuel cell stack bipolar plates; Designing a hydrogen fuel cell end plate model; Determining the total number N of fuel cell stack bipolar plates; Designing a model of bipolar plates with protrusions according to the total number N of fuel cell stack bipolar plates, the design parameters including protrusion size and number of protrusions; Performing finite element simulation analysis on the improved fuel cell stack structure, and extracting the stress on all bipolar plates for chart analysis; Setting evaluation criteria; According to the chart analysis, it is determined whether the stress uniformity performance requirements and the evaluation criteria are met. If yes, the maximum stress of the first and last bipolar plates with protrusions is calculated. If not, return to the step of designing a model of bipolar plates with protrusions. The N bipolar plates are composed of i first bipolar plates and N-i second bipolar plates, the two ends of the second bipolar plate have connecting protrusions beyond the outer edge of the first bipolar plate, the thickness△h of the single-side outward protrusion of the second bipolar plate is the percentage of the original thickness h of the bipolar plate, the total number N of the bipolar plates is different, the number of the second bipolar plates contained is different, and the percentage is different, when the total number N of the bipolar plates is 20, there is one second bipolar plate, the thickness h of the first bipolar plate is 4mm, and the percentage is 15%, from one end of the stack in the length direction to the other end in the length direction, one second bipolar plate is inserted every 9 first bipolar plates.

2. The method of claim 1, wherein: The outer surface of the end plate is outwardly protruding.

3. The method of claim 2, wherein: the bipolar plate is made of a material having a yield strength of at least 200 MPa; the thickness of the bipolar plate is at least 1 mm; and the thickness of the bipolar plate is at least 2 times the thickness of the flow field channels. A plurality of bolt holes are arranged on the end plate, and the bolt holes gradually increase in height from the two ends of the end plate in the length direction to the center.

4. The method of claim 3, wherein: the fuel cell bipolar plate is made of a material having a yield strength of at least 200 MPa. The maximum height difference of the bolt holes is 14.88 mm.

5. The method of claim 2, wherein: the fuel cell bipolar plate is made of a material having a yield strength of at least 35 ksi. The radius R of the outward protrusion of the end plate is 1760 mm, and the height△H is 12 mm.

6. The method of claim 1-5, wherein: When the total number N of the bipolar plates is 40, there are three second bipolar plates, the thickness h of the first bipolar plate is 4mm, and the percentage is 15%, from one end of the stack in the length direction to the other end in the length direction, one second bipolar plate is inserted every 9 first bipolar plates.

7. The method of claim 1-5, wherein: When the total number N of the bipolar plates is 81, there are seven second bipolar plates, the thickness h of the first bipolar plate is 4mm, and the percentage is 25%, from one end of the stack in the length direction to the other end in the length direction, one second bipolar plate is inserted every 9 first bipolar plates.

Images