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

Abstract

The invention provides a fuel cell stack elastic element, a model selection method thereof and a fuel cell stack. According to the fuel cell stack elastic element type selection method, a stack in a preset state is compressed to an EOL state, the rigidity coefficient of the stack in the EOL state and the core creep of the stack in the EOL state are obtained, and based on the minimum packaging force and the initial packaging force of the stack, the elastic element of the stack is selected. And calculating the rigidity coefficient of the elastic element according to the rigidity coefficient of the electric pile in the EOL state and the core creep of the electric pile in the EOL state. According to the fuel cell stack elastic element type selection method disclosed by the invention, the stack is compressed to the EOL state, so that the accuracy of calculating the rigidity coefficient of the elastic element can be improved, and support is provided for the type selection of the elastic element.

Description

Technical Field

[0001] The present invention relates to the field of fuel cell technology, and in particular to a method for selecting an elastic element for a fuel cell stack. The present invention also relates to an elastic element for a fuel cell stack and a fuel cell stack. Background Art

[0002] Fuel cell stacks are typically composed of hundreds of bipolar plates and MEAs (membrane electrode assemblies), offering advantages such as high power generation efficiency, minimal environmental pollution, and high specific energy. To improve fuel cell stack performance, contact resistance must be reduced, requiring packaging to provide sufficient strength.

[0003] For existing fuel cell stacks, the packaging force is generally required to be within a certain range (30-50KN), and the size of the packaging force directly affects the performance and durability of the stack. If the packaging force is too small, the contact resistance will increase, thereby increasing the ohmic loss and reducing performance. There is also a risk of sealing failure, resulting in stack leakage. Therefore, the packaging force of the stack must be greater than the minimum packaging force that the stack can accept during its life cycle (under this packaging force condition, the ohmic loss and sealing performance must also meet the requirements). However, during the actual operation of the stack, due to plastic deformation of the gas diffusion layer, the stack packaging force is reduced, the ohmic loss is increased, and the risk of leakage increases.

[0004] To compensate for the attenuation of the packaging force caused by long-term operation of the fuel cell stack, elastic elements are usually added to the stack. By placing the elastic elements between the end plates and the floating plate, the elastic elements store a certain amount of elastic potential energy during stack assembly. When the packaging force of the fuel cell stack decays, the elastic elements release some of this elastic potential energy to compensate for the attenuation of the packaging force. Given the important role of elastic elements in fuel cell stacks, how to select the right elastic elements has become an urgent problem to be solved. However, the existing methods for selecting elastic elements have considerable 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 a fuel cell stack to improve the accuracy of calculating the stiffness coefficient of the elastic elements, thereby providing support for the selection of the elastic elements.

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

[0007] A method for selecting an elastic element for a fuel cell stack comprises: compressing a fuel cell stack in a preset state to an EOL state; obtaining a stiffness coefficient of the fuel cell stack and a core creep amount of the fuel cell stack in the EOL state; and calculating a stiffness coefficient of the elastic element based on a minimum packaging force of the fuel cell stack and an initial packaging force of the fuel cell stack using the stiffness coefficient of the fuel cell stack in the EOL state and the core creep amount of the fuel cell stack in the EOL state.

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

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

[0010] Furthermore, obtaining the stiffness coefficient of the fuel cell stack in the EOL state and the core creep amount of the fuel cell stack in the EOL state includes: measuring the pressure and displacement curve 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 curve of the fuel cell stack, and the core creep amount 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 packaging force and the initial packaging force of the stack by the stiffness coefficient of the stack in the EOL state and the core creep of the stack in the EOL state includes:

[0012]

[0013] Calculate the stiffness coefficient of the elastic element; where ΔF is the stack attenuation packaging force, F axsembly is the initial packaging force of the stack, F min is the minimum packaging force of the stack, K disc is the stiffness coefficient of the elastic element, K core 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 packaging force of the fuel cell stack is determined.

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

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

[0017] The method for selecting elastic elements of a fuel cell stack described in the present invention compresses the stack in a preset state to an EOL state, so that the stack is closer to the actual usage state, and then obtains the stiffness coefficient of the stack in the EOL state and the core creep of the stack in the EOL state. Based on the minimum packaging force and the initial packaging force of the stack, the stiffness coefficient of the elastic element is calculated by the stiffness coefficient of the stack in the EOL state and the core creep of the stack in the EOL state, thereby improving the accuracy of the calculation of the stiffness coefficient of the elastic element, thereby providing support for the selection of the elastic element.

[0018] In addition, by repeatedly applying a preset pressure to the stack in a preset state at preset time intervals until the size of the stack is in a stable state, the plastic deformation of the gas diffusion layer can be quickly removed, thereby reducing the cost of obtaining the stack in the EOL state and improving efficiency.

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

[0020] Secondly, the stiffness coefficient of the stack and the amount of core creep of the stack in the EOL state can be accurately obtained through the pressure and displacement curve of the stack in the EOL state. The calculation of the stiffness coefficient of the elastic element is further simplified to a spring model, specifically through

[0021]

[0022] Calculate the stiffness coefficient of elastic elements, easy to calculate and accurate.

[0023] Furthermore, disc springs are selected as the elastic elements of fuel cell stacks, which can withstand large loads with small deformation, have short strokes, require small spaces, are easy to combine and use, are easy to repair 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 fuel cell stack elastic element selection method.

[0025] Compared with the prior art, the fuel cell stack elastic element of the present invention has good adaptability, can well compensate for the attenuation of part of the packaging force, and has good practicality.

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

[0027] Compared with the prior art, the fuel cell stack described in the present invention can effectively deal with the problem of attenuation of packaging force during use and has good practicality. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0029] Figure 1 A schematic flow chart of a method for selecting an elastic element for a fuel cell stack according to an embodiment of the present invention;

[0030] Figure 2 A curve chart showing the relationship between the number of compression cycles and the core size according to an embodiment of the present invention;

[0031] Figure 3 A pressure-displacement curve diagram according to an embodiment of the present invention;

[0032] Figure 4 Schematic diagram of a spring model of an inelastic element according to an embodiment of the present invention;

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

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

[0035] Description of reference numerals:

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

[0037] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0038] In the description of the present invention, it should be noted that if terms such as "upper," "lower," "inner," and "outer" appear to indicate orientation or positional relationships, these are based on the orientation or positional relationships shown in the accompanying drawings and are intended solely to facilitate and simplify the description of the present invention. They do not indicate or imply that the devices or components referred to must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limitations on the present invention. Furthermore, if terms such as "first" and "second" appear, they are used solely for descriptive purposes and should not be construed as indicating or implying relative importance.

[0039] Furthermore, in the description of the present invention, unless otherwise expressly defined, the terms "mounted," "connected," "connect," and "connector" should be interpreted broadly. For example, they may refer to fixed, removable, or integral connections; mechanical or electrical connections; direct or indirect connections through an intermediary; and internal communication between two components. Those skilled in the art will appreciate the specific meanings of these terms in the present invention based on the specific circumstances.

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

[0041] Example 1

[0042] This embodiment relates to a method for selecting a fuel cell stack elastic element. Figure 1 The method for selecting the fuel cell stack elastic element includes:

[0043] Step S101 , compressing the battery stack in a preset state to an EOL (End-of-life) state.

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

[0045] Step S103 , calculating the stiffness coefficient of the elastic element based on the minimum packaging force of the stack and the initial packaging force of the stack, by using the stiffness coefficient of the stack in the EOL state and the core creep amount of the stack in the EOL state.

[0046] In this embodiment, the stiffness coefficient of the battery stack and the amount of core creep of the battery stack differ greatly under the BOL (Begin-Of-Life) state and the EOL state. If the stiffness coefficient of the battery stack and the amount of core creep of the battery stack in the BOL state are used, it will have a great impact on the calculation of the stiffness coefficient of the elastic element and the subsequent selection of the elastic element, thereby affecting the effect of the elastic element in compensating for the attenuation of the packaging force. Therefore, the battery stack in the 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 the further selection of the elastic element. It should be noted that the preset state of the battery stack described above can be selected according to the actual usage scenario, for example, it can be a battery stack in the BOL state.

[0047] In some embodiments, step S101 may include: repeatedly applying a preset pressure to the 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 creep of the core of the fuel cell stack mainly comes from the plastic deformation of the gas diffusion layer, this embodiment uses an accelerated test method to quickly remove the plastic deformation of the gas diffusion layer to obtain the fuel cell stack in the EOL state. Figure 2 , a preset pressure can be cyclically applied to the fuel cell stack in a preset state at preset time intervals until the size of the fuel cell stack is in a stable state. At this time, the application of pressure to the fuel cell stack can be stopped. During this process, as the number of cyclic compression times N increases, the core size L continues to decrease 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 based on actual operating scenarios and requirements, and the stable state of the stack size can mean that the stack size no longer changes. The step of compressing the stack from the preset state to the EOL state provided in this embodiment has the advantages of high efficiency and low cost, compared to performing endurance testing on the stack to bring it closer to the state of actual application scenarios.

[0050] Preferably, the preset pressure can be set as the maximum packaging force during the operation of the battery stack. During the actual operation of the battery stack, due to the existence of gas pressure and thermal expansion (operating temperature 70-90°C), its actual working pressure is greater than the initial packaging force. Setting the preset pressure as the maximum packaging force during the operation of the battery stack can make the obtained EOL state of the battery stack closer to the battery stack in actual use, thereby providing a basis for subsequently improving the calculation accuracy of the stiffness coefficient of the elastic element. It can be considered that the maximum pressure during the operation of the battery stack, that is, the maximum packaging force during the operation of the battery stack, can be obtained by using a stress strain gauge or a pressure-sensitive blanket.

[0051] In some embodiments, step S102 may include: measuring the pressure and displacement curve 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 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.

[0052] In this embodiment, please refer to Figure 3 As the pressure on the stack increases, the stack compression, or displacement, also gradually increases. Based on these two variables, a stack pressure-displacement curve is constructed. In a specific implementation, the stack dimensions at EOL can be restored to those at BOL. At this point, pressure is gradually applied to the stack, and the applied pressure and stack displacement are recorded to construct a stack pressure-displacement curve.

[0053] Specifically, the displacement of the battery stack corresponding to the battery stack packaging force in the BOL state can be selected as the core creep of the battery stack in the EOL state. For the selection of the stiffness coefficient of the battery stack in the EOL state, it can be based on actual needs. For example, based on the preset packaging force remaining during the working process of the battery stack, the slope of the point on the pressure and displacement curve of the battery stack corresponding to the remaining packaging force is selected as the stiffness coefficient of the battery stack in the EOL state. In addition, the slope within a section of the curve can be averaged as the stiffness coefficient of the battery stack in the EOL state. And, if the preset packaging force remaining during the working process of the battery stack is an interval value, a section of the curve on the pressure and displacement curve of the battery stack corresponding to the remaining packaging force interval value can also be selected, and the curve section is fitted into a straight line, and the slope of the straight line is used as the stiffness coefficient of the battery stack in the EOL state.

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

[0055]

[0056] Calculate the stiffness coefficient of the elastic element; where ΔF is the stack attenuation packaging force, F assembly is the initial packaging force of the stack, F min is the minimum packaging force of the stack, K disc is the stiffness coefficient of the elastic element, K core 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 battery stack is simplified into a spring model. Figure 4 This is a schematic diagram of a spring model without elastic elements. In this case, the core and other components are simplified into a spring model, and the elastic coefficient of the spring is K core , which is the stiffness coefficient of the stack. When the spring is compressed and produces displacement, it is equivalent to the core creep of the stack. The displacement of the spring δ is the core creep amount. It can be understood that the packaging force attenuation is K core *δ. Figure 5 This is a schematic diagram of a spring model with elastic elements. By analogy, the stiffness coefficient of the stack in the EOL state is: The core creep of the stack at EOL is δ, and the packaging force decay is Then we can construct the equation:

[0058]

[0059] In the above equation, the attenuated packaging force of the battery stack, that is, the difference between the initial packaging force of the battery stack and the minimum packaging force of the battery stack can be calculated in advance. Among them, the initial packaging force of the battery stack is set based on the actual situation, and the minimum packaging force of the battery stack can be determined by the performance of the battery stack under different test pressures and the airtightness test results of the battery stack. In specific implementation, based on actual usage and design requirements, the performance of the above-mentioned battery stack can be the polarization performance of the battery stack, and the airtightness test results of the battery stack can be the leakage of the battery stack. In this way, the minimum battery stack packaging force among the battery stack packaging forces that can meet the polarization performance requirements of the battery stack and the leakage requirements of the battery stack under different test pressures is the minimum packaging force of the battery stack.

[0060] After obtaining the stiffness coefficient and core creep of the fuel cell stack at EOL, the stiffness coefficient range of the elastic element can be calculated using the above equation. It should be noted that the smaller the stiffness coefficient of the elastic element, the greater the packaging force it can compensate for, but the more space it occupies. Therefore, it is necessary to select an appropriate elastic element based on actual needs.

[0061] Preferably, the fuel cell stack's elastic element can be a disc spring. A disc spring is a spring formed by cutting a hole in the center of a circular disk into a conical disc shape. Unlike traditional springs, disc springs have unique functional characteristics. For example, disc springs can withstand large loads with minimal deformation, have short strokes, require minimal space, are easy to use and assemble, are easily repaired and replaced, are economical and safe, and have a long service life.

[0062] The method for selecting elastic elements for fuel cell stacks in this embodiment compresses the stack in a preset state to an EOL state, so that the stack is closer to the actual usage state, and then obtains the stiffness coefficient of the stack in the EOL state and the amount of core creep of the stack in the EOL state. Based on the minimum packaging force of the stack and the initial packaging force of the stack, the stiffness coefficient of the elastic element is calculated by the stiffness coefficient of the stack in the EOL state and the amount of core creep of the stack in the EOL state, thereby improving the accuracy of the calculation of the stiffness coefficient of the elastic element, thereby providing support for the selection of the elastic element.

[0063] Example 2

[0064] This embodiment relates to a fuel cell stack elastic element, which is selected using the fuel cell stack elastic element selection method in Example 1 and is applied to the fuel cell stack. It has good adaptability, can well compensate for the attenuation of part of the packaging force, and has good practicality.

[0065] Example 3

[0066] This embodiment relates to a fuel cell stack, including a fuel cell stack assembly and a fuel cell stack elastic element selected using the method for selecting a fuel cell stack elastic element of the first embodiment.

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

[0068] The fuel cell stack of this embodiment is provided with a fuel cell stack elastic element selected using the method for selecting the fuel cell stack elastic element in the first embodiment, which can effectively deal with the problem of attenuation of packaging force 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 in the scope of protection of the present invention.

Claims

1. A method for selecting an elastic element for a fuel cell stack, characterized in that: include: Compressing the battery stack in a preset state to an EOL state; Obtain the stiffness coefficient of the fuel cell stack at the EOL state and the core creep amount of the fuel cell stack at the EOL state; Based on the minimum packaging force of the fuel cell stack and the initial packaging force of the fuel cell stack, the stiffness coefficient of the elastic element is calculated by the stiffness coefficient of the fuel cell stack in the EOL state and the core creep amount of the fuel cell stack in the EOL state.

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

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

4. The method for selecting a fuel cell stack elastic element according to claim 1, characterized in that: The obtaining of the stiffness coefficient of the fuel cell stack in the EOL state and the amount of core creep of the fuel cell stack in the EOL state comprises: Measure the pressure and displacement curves of the 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 amount of the fuel cell stack in the EOL state is the displacement of the fuel cell stack.

5. The method for selecting a fuel cell stack elastic element according to claim 1, characterized in that: The calculating of the stiffness coefficient of the elastic element based on the minimum packaging force of the battery stack and the initial packaging force of the battery stack by the stiffness coefficient of the battery stack in the EOL state and the amount of core creep of the battery stack in the EOL state includes: pass Calculate the stiffness coefficient of the elastic element; where ΔF is the stack attenuation packaging force, F assembly is the initial packaging force of the battery stack, F min is the minimum packaging force of the battery stack, K disc is the stiffness coefficient of the elastic element, K core 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.

6. The method for selecting a fuel cell stack elastic element according to claim 1, characterized in that: 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 packaging force of the fuel cell stack is determined.

7. The method for selecting a fuel cell stack elastic element according to any one of claims 1 to 6, characterized in that: The fuel cell stack elastic element is a disc spring.

8. A fuel cell stack elastic element, characterized in that: The fuel cell stack elastic element is selected using the fuel cell stack elastic element selection method as described in any one of claims 1 to 7, and is applied to a fuel cell stack.

9. A fuel cell stack, characterized in that: It comprises a fuel cell stack assembly, and a fuel cell stack elastic element selected by using the method for selecting a fuel cell stack elastic element as described in any one of claims 1 to 7.

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