Fuel cell stack elastic element, selection method thereof, and fuel cell stack

Abstract

The application provides a fuel cell stack elastic element, a selection method thereof and a fuel cell stack. The selection method of the fuel cell stack elastic element of the application compresses the stack in a preset state to an EOL state, obtains a stiffness coefficient of the stack in the EOL state and a stack core creep variable of the stack in the EOL state, and calculates the stiffness coefficient of the elastic element based on the minimum packaging force of the stack and the initial packaging force of the stack, the stiffness coefficient of the stack in the EOL state and the stack core creep variable of the stack in the EOL state. The selection method of the fuel cell stack elastic element of the application can improve the accuracy of the calculation of the stiffness coefficient of the elastic element by compressing the stack to the EOL state, thereby providing support for the selection of the elastic element.

Description

Technical Field

[0001] This invention relates to the field of fuel cell technology, and in particular to a method for selecting elastic elements for fuel cell stacks. This invention also relates to an elastic element for a fuel cell stack and a fuel cell stack itself. Background Technology

[0002] Fuel cell stacks typically consist of hundreds of bipolar plates and MEAs (membrane electrode assemblies), offering advantages such as high power generation efficiency, low environmental pollution, and high specific energy. During use, to improve the performance of the fuel cell stack, it is necessary to reduce contact resistance; therefore, encapsulation is required to provide a certain level of sealing force.

[0003] For existing fuel cell stacks, the sealing force is generally required to be within a certain range (30-50 kN). The magnitude of the sealing force directly affects the performance and durability of the stack. If the sealing force is too small, it will lead to an increase in contact resistance, thereby increasing ohmic losses, reducing performance, and posing a risk of seal failure leading to gas leakage. Therefore, the sealing force of the stack must be greater than the minimum acceptable sealing force during its lifespan (under this sealing force condition, ohmic losses and sealing performance must also meet requirements). However, during the actual operation of the stack, due to the plastic deformation of the gas diffusion layer, the sealing force of the stack decreases, ohmic losses increase, and the risk of gas leakage increases.

[0004] To compensate for the degradation of sealing force during long-term operation of fuel cell stacks, elastic elements are typically added. These elastic elements are placed between the end plates and the floating plate, storing elastic potential energy during stack assembly. When the sealing force of the stack weakens, the elastic element releases some of this potential energy to compensate for the reduction in sealing force. Given the crucial role of elastic elements in fuel cell stacks, selecting suitable elastic elements is a pressing issue. However, existing methods for selecting elastic elements have significant room for improvement in terms of accuracy. Summary of the Invention

[0005] In view of this, the present invention aims to propose a method for selecting elastic elements of fuel cell stacks, so as to improve the accuracy of calculating the stiffness coefficient of elastic elements, thereby providing support for the selection of elastic elements.

[0006] To achieve the above objectives, the technical solution of the present invention is implemented as follows:

[0007] A method for selecting elastic elements of a fuel cell stack includes: compressing the stack in a preset state to an EOL (Extended Operating Length) state; obtaining the stiffness coefficient and core creep of the stack in the EOL state; and calculating the stiffness coefficient of the elastic element based on the minimum packing force and the initial packing force of the stack, using the stiffness coefficient and core creep of the stack in the EOL state.

[0008] Furthermore, compressing the fuel cell stack in the preset state to the EOL state includes: repeatedly applying a preset pressure to the fuel cell stack in the preset state at preset time intervals until the size of the fuel cell stack is stable.

[0009] Furthermore, the preset pressure is the maximum sealing force during the operation of the fuel cell stack.

[0010] Furthermore, obtaining the stiffness coefficient and core creep of the fuel cell stack in the EOL state includes: measuring the pressure and displacement curves of the fuel cell stack in the EOL state; the stiffness coefficient of the fuel cell stack in the EOL state is the slope of the pressure and displacement curves of the fuel cell stack, and the core creep of the fuel cell stack in the EOL state is the displacement of the fuel cell stack.

[0011] Furthermore, the calculation of the stiffness coefficient of the elastic element based on the minimum packing force and initial packing force of the fuel cell stack, using the stiffness coefficient of the fuel cell stack in the EOL state and the core creep of the fuel cell stack in the EOL state, includes: using...

[0012]

[0013] Calculate the stiffness coefficient of the elastic element; where ΔF is the stack decay encapsulation force, F axsembly F is the initial encapsulation force of the fuel cell stack. min K is the minimum encapsulation force of the fuel cell stack. disc K is the stiffness coefficient of the elastic element. core δ is the stiffness coefficient of the fuel cell stack in the EOL state, and δ is the core creep of the fuel cell stack in the EOL state.

[0014] Furthermore, based on the performance of the fuel cell stack under different test pressures and the airtightness test results of the fuel cell stack, the minimum encapsulation force of the fuel cell stack is determined.

[0015] Furthermore, the elastic element of the fuel cell stack is a disc spring.

[0016] Compared with the prior art, the present invention has the following advantages:

[0017] The method for selecting elastic elements in a fuel cell stack as described in this invention compresses the stack from a preset state to an EOL (End-of-Life) state, making the stack closer to its actual operating condition. Then, the stiffness coefficient and core creep of the stack in the EOL state are obtained. Based on the minimum and initial encapsulation forces of the stack, the stiffness coefficient of the elastic element is calculated using the stiffness coefficient and core creep of the stack in the EOL state. This improves the accuracy of the stiffness coefficient calculation and provides support for the selection of elastic elements.

[0018] Furthermore, by repeatedly applying a preset pressure to a fuel cell stack in a preset state at preset time intervals until the stack size stabilizes, the plastic deformation of the gas diffusion layer can be quickly removed, thereby reducing the cost of obtaining an EOL-state fuel cell stack and improving efficiency.

[0019] In addition, the preset pressure is set as the maximum sealing force during the operation of the fuel cell stack. This takes into account the situation where the actual working pressure of the fuel cell stack is greater than the initial sealing force due to the presence of gas pressure and thermal expansion during actual operation. This makes the fuel cell stack in the EOL state more similar to the fuel cell stack in actual use, thus providing a basis for improving the accuracy of the stiffness coefficient calculation of the elastic element.

[0020] Secondly, by using the pressure and displacement curves of the fuel cell stack in the EOL (Extended Operating Range) state, the stiffness coefficient and core creep of the fuel cell stack in the EOL state can be accurately obtained. Furthermore, the calculation of the stiffness coefficient of the elastic element is simplified to a spring model, specifically through...

[0021]

[0022] The stiffness coefficient of an elastic element is easy to calculate and accurate.

[0023] Furthermore, disc springs are selected as the elastic element of fuel cell stacks because they can withstand large loads with small deformations, have short strokes, require little space, are easy to combine and use, are easy to maintain and replace, are economical and safe, and have a long service life.

[0024] Another object of the present invention is to provide a fuel cell stack elastic element, which is selected using the selection method of the fuel cell stack elastic element.

[0025] Compared with existing technologies, the fuel cell stack elastic element described in this invention has good adaptability, can effectively compensate for some of the attenuation of the encapsulation force, and has good practicality.

[0026] The present invention also proposes a fuel cell stack, including a stack assembly, and a fuel cell stack elastic element selected using the selection method of the fuel cell stack elastic element.

[0027] Compared with existing technologies, the fuel cell stack described in this invention can effectively address the problem of encapsulation force attenuation during use, and has good practicality. Attached Figure Description

[0028] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0029] Figure 1 This is a schematic flowchart illustrating the selection method for the elastic elements of a fuel cell stack according to an embodiment of the present invention.

[0030] Figure 2 This is a graph showing the number of cyclic compressions versus core size as described in an embodiment of the present invention.

[0031] Figure 3 This is a pressure-displacement curve as described in an embodiment of the present invention;

[0032] Figure 4 This is a schematic diagram of a spring model without elastic elements according to an embodiment of the present invention;

[0033] Figure 5 This is a schematic diagram of a spring model with elastic elements according to an embodiment of the present invention;

[0034] Figure 6 This is a schematic diagram of the structure of the fuel cell stack according to an embodiment of the present invention.

[0035] Explanation of reference numerals in the attached figures:

[0036] 1. First pressure plate; 2. Elastic element; 3. Second pressure plate; 4. Core; 5. End plate. Detailed Implementation

[0037] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0038] In the description of this invention, it should be noted that the use of terms such as "upper," "lower," "inner," and "outer," indicating orientation or positional relationship, is based on the orientation or positional relationship shown in the accompanying drawings and is only for the convenience of describing the invention and simplifying the description. It does not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the use of terms such as "first" and "second" is also for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0039] Furthermore, in the description of this invention, unless otherwise explicitly defined, the terms "installation," "connection," "joining," and "connector" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention in light of the specific circumstances.

[0040] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0041] Example 1

[0042] This embodiment relates to a method for selecting elastic elements in a fuel cell stack. Please refer to [link / reference]. Figure 1 The selection method for the elastic elements of the fuel cell stack includes:

[0043] Step S101: Compress the fuel cell stack in the preset state to the EOL (End-of-life) state.

[0044] Step S102: Obtain the stiffness coefficient and core creep of the fuel cell stack in the EOL state.

[0045] Step S103: Based on the minimum packing force and the initial packing force of the fuel cell stack, calculate the stiffness coefficient of the elastic element using the stiffness coefficient of the fuel cell stack in the EOL state and the core creep of the fuel cell stack in the EOL state.

[0046] In this embodiment, the stiffness coefficient and core creep of the fuel cell stack differ significantly between the BOL (Begin-Of-Life) and EOL (End-of-Life) states. Using the stiffness coefficient and core creep of the fuel cell stack in the BOL state would significantly impact the calculation of the stiffness coefficient of the elastic element and the subsequent selection of the elastic element, thereby affecting the effectiveness of the elastic element in compensating for the attenuation of the encapsulation force. Therefore, the fuel cell stack in a preset state is compressed to the EOL state to improve the accuracy of calculating the stiffness coefficient of the elastic element and provide support for further selection of the elastic element. It should be noted that the preset state of the fuel cell stack mentioned above can be selected according to the actual application scenario; for example, it can be a fuel cell stack in the BOL state.

[0047] In some embodiments, step S101 may include: repeatedly applying a preset pressure to a fuel cell stack in a preset state at preset time intervals until the size of the fuel cell stack is in a stable state.

[0048] In this embodiment, considering that the core creep of the fuel cell stack mainly originates from the plastic deformation of the gas diffusion layer, this embodiment employs an accelerated testing method to rapidly remove the plastic deformation of the gas diffusion layer, thereby obtaining a fuel cell stack in the EOL (Exhaust-in-Time) state. For details, please refer to... Figure 2 A preset pressure can be applied to the fuel cell stack in a preset state at preset time intervals until the size of the fuel cell stack is stable. At this point, the pressure can be stopped. During this process, as the number of compression cycles N increases, the core size L continuously decreases until it no longer changes.

[0049] It should be noted that the preset pressure can be a fixed pressure, the preset time interval can be selected according to the actual operating scenario and requirements, and the fuel cell stack size being in a stable state means that the size of the fuel cell stack no longer changes. The step of compressing the fuel cell stack to the EOL state provided in this embodiment has the advantages of high efficiency and low cost compared to making the fuel cell stack closer to the state of the actual application scenario through durability testing.

[0050] Preferably, a preset pressure can be set as the maximum encapsulation force during the fuel cell stack's operation. During actual operation, due to gas pressure and thermal expansion (operating temperature 70-90℃), the actual operating pressure is greater than the initial encapsulation force. Setting the preset pressure as the maximum encapsulation force during operation allows the obtained EOL-state fuel cell stack to more closely resemble the stack in actual use, thus providing a basis for improving the accuracy of subsequent calculations of the stiffness coefficient of the elastic element. It is possible to obtain the maximum pressure during fuel cell stack operation, i.e., the maximum encapsulation force during operation, using stress-strain gauges or pressure-sensitive blankets.

[0051] In some embodiments, step S102 may include: measuring the pressure and displacement curves of the fuel cell stack in the EOL state; the stiffness coefficient of the fuel cell stack in the EOL state is the slope of the pressure and displacement curves of the fuel cell stack, and the core creep of the fuel cell stack in the EOL state is the displacement of the fuel cell stack.

[0052] In this embodiment, please refer to Figure 3 As the pressure on the fuel cell stack increases, the compression of the stack, i.e., the displacement of the stack, also gradually increases. Based on the two variables of pressure and displacement, a pressure-displacement curve of the fuel cell stack is constructed. In the specific implementation process, the size of the fuel cell stack in the EOL state can be restored to the size of the fuel cell stack in the BOL state. At this time, the pressure is gradually increased on the fuel cell stack, and the applied pressure value and the displacement of the fuel cell stack are recorded to construct the pressure-displacement curve of the fuel cell stack.

[0053] Specifically, the displacement of the fuel cell stack corresponding to the applied pressure being the stack encapsulation force in the BOL state can be selected as the core creep variable of the fuel cell stack in the EOL state. The stiffness coefficient of the fuel cell stack in the EOL state can be selected based on actual needs, such as the slope of the point on the pressure-displacement curve corresponding to the preset remaining encapsulation force during fuel cell operation. Alternatively, the average slope over a range of this curve can be used as the stiffness coefficient of the fuel cell stack in the EOL state. Furthermore, if the preset remaining encapsulation force during fuel cell operation is a range, a segment of the pressure-displacement curve corresponding to this range of remaining encapsulation force can be selected, fitted to a straight line, and the slope of this straight line can be used as the stiffness coefficient of the fuel cell stack in the EOL state.

[0054] In some embodiments, step S103 may include: via

[0055]

[0056] Calculate the stiffness coefficient of the elastic element; where ΔF is the stack decay encapsulation force, F assembly F is the initial encapsulation force of the fuel cell stack. min K is the minimum encapsulation force of the fuel cell stack. disc K is the stiffness coefficient of the elastic element. core δ is the stiffness coefficient of the fuel cell stack in the EOL state, and δ is the core creep of the fuel cell stack in the EOL state.

[0057] In this embodiment, please refer to Figure 4 and Figure 5 In this embodiment, the fuel cell stack is simplified as a spring model. Figure 4 This is a schematic diagram of a spring model without elastic elements. In this case, components such as the reactor core are simplified into a spring model, with the spring constant being K. core This refers to the stiffness coefficient of the fuel cell stack. When the spring is compressed and displaced, it is equivalent to core creep occurring in the fuel cell stack; the spring displacement δ is the core creep. Understandably, the attenuation of the packing force is K. core *δ. Figure 5 This is a schematic diagram of a spring model with elastic elements. Similarly, it can be deduced that the stiffness coefficient of the fuel cell stack in the EOL state is... The core creep of the fuel cell stack in the EOL state is δ, and the encapsulation force decay is... Then we can construct the equation:

[0058]

[0059] In the above equation, the fuel cell attenuation sealing force, i.e., the difference between the initial sealing force and the minimum sealing force, can be calculated in advance. The initial sealing force is set based on actual conditions, while the minimum sealing force can be determined through the fuel cell's performance under different test pressures and the results of its airtightness tests. In practice, based on actual usage and design requirements, the fuel cell's performance can be its polarization performance, and the airtightness test results can be its leakage rate. Thus, the minimum fuel cell sealing force, which satisfies both the polarization performance and leakage rate requirements under different test pressures, is the smallest possible fuel cell sealing force.

[0060] After obtaining the stiffness coefficient and core creep of the fuel cell stack in the EOL state, the stiffness coefficient range of the elastic element can be calculated using the above equations. It should be noted that the smaller the stiffness coefficient of the elastic element, the greater the compensating force it can provide, but the larger the space it occupies. Therefore, it is necessary to select a suitable elastic element based on actual requirements.

[0061] As a preferred option, the elastic element of the fuel cell stack can be a disc spring. A disc spring is a spring with a hole in the center of a disc to form a conical disc shape. Unlike traditional springs, disc springs have special functions. For example, disc springs have the characteristics of being able to withstand large loads with small deformation, short stroke, small space requirement, convenient combination and use, easy maintenance and replacement, high economy and safety, and long service life.

[0062] The method for selecting elastic elements in a fuel cell stack according to this embodiment compresses the stack from a preset state to an EOL (End-of-Life) state, making the stack closer to its actual operating state. Then, it obtains the stiffness coefficient and core creep of the stack in the EOL state. Based on the minimum and initial encapsulation forces of the stack, it calculates the stiffness coefficient of the elastic element using the stiffness coefficient and core creep of the stack in the EOL state, thereby improving the accuracy of the stiffness coefficient calculation and providing support for the selection of elastic elements.

[0063] Example 2

[0064] This embodiment relates to a fuel cell stack elastic element. The fuel cell stack elastic element is selected using the fuel cell stack elastic element selection method in Embodiment 1 and applied to the fuel cell stack. It has good adaptability, can effectively compensate for some of the attenuation of the encapsulation force, and has good practicality.

[0065] Example 3

[0066] This embodiment relates to a fuel cell stack, including a stack assembly and a fuel cell stack elastic element selected using the fuel cell stack elastic element selection method of Embodiment 1.

[0067] In some embodiments, such as Figure 6 As shown, similar to the stack structure in existing fuel cells, the fuel cell stack in this embodiment includes a core 4, a second pressure plate 3, an elastic element 2, and a first pressure plate 1 arranged sequentially on the end plate 5. The elastic element 2 is the fuel cell stack elastic element selected using the fuel cell stack elastic element selection method of Embodiment 1.

[0068] The fuel cell stack of this embodiment is equipped with a fuel cell stack elastic element selected using the fuel cell stack elastic element selection method in Embodiment 1. This can effectively address the problem of encapsulation force attenuation during use and has good practicality.

[0069] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for selecting elastic elements in a fuel cell stack, characterized in that, include: Compress the fuel cell stack, which is in a preset state, to the end-of-life (EOL) state; Obtain the stiffness coefficient and core creep of the fuel cell stack in the EOL state; Based on the minimum packing force and initial packing force of the fuel cell stack, the stiffness coefficient of the elastic element is calculated using the stiffness coefficient of the fuel cell stack in the EOL state and the core creep of the fuel cell stack in the EOL state. The acquisition of the stiffness coefficient and core creep of the fuel cell stack in the EOL state includes: Measure the pressure and displacement curves of the fuel cell stack in the EOL state; The stiffness coefficient of the fuel cell stack in the EOL state is the slope of the pressure-displacement curve of the fuel cell stack, and the core creep of the fuel cell stack in the EOL state is the displacement of the fuel cell stack. The calculation of the stiffness coefficient of the elastic element based on the minimum packing force and initial packing force of the fuel cell stack, using the stiffness coefficient of the fuel cell stack in the EOL state and the core creep of the fuel cell stack in the EOL state, includes: pass Calculate the stiffness coefficient of the elastic element; wherein, For the stack attenuation packaging force, F assembly F is the initial encapsulation force of the fuel cell stack. min K is the minimum encapsulation force of the fuel cell stack. disc K is the stiffness coefficient of the elastic element. core δ is the stiffness coefficient of the fuel cell stack in the EOL state, and δ is the core creep of the fuel cell stack in the EOL state.

2. The method for selecting elastic elements in a fuel cell stack according to claim 1, characterized in that, The step of compressing the fuel cell stack in a preset state to an EOL state includes: A preset pressure is repeatedly applied to the fuel cell stack in the preset state at preset time intervals until the size of the fuel cell stack is stable.

3. The method for selecting elastic elements in a fuel cell stack according to claim 2, characterized in that, The preset pressure is the maximum sealing force during the operation of the fuel cell stack.

4. The method for selecting elastic elements in a fuel cell stack according to claim 1, characterized in that, Based on the performance of the fuel cell stack under different test pressures and the results of the fuel cell stack's airtightness test, the minimum encapsulation force of the fuel cell stack is determined.

5. The method for selecting the elastic element of a fuel cell stack according to any one of claims 1-4, characterized in that, The elastic element of the fuel cell stack is a disc spring.

6. A fuel cell stack elastic element, characterized in that, The fuel cell stack elastic element is selected using the selection method for fuel cell stack elastic elements as described in any one of claims 1-5, and is applied to the fuel cell stack.

7. A fuel cell stack, characterized in that, It includes fuel cell stack assemblies and fuel cell stack elastic elements selected using the selection method for fuel cell stack elastic elements as described in any one of claims 1-5.

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