Bipolar plate and method for producing bipolar plate
By designing a bipolar plate structure with multiple ports and multiple flow fields in the fuel cell stack, the flow path of the fluid is optimized, the problem of insufficient flow distribution in the prior art is solved, and the efficiency and performance of the fuel cell stack are improved.
Patent Information
- Application Number
- CN202380041212.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Priority Date
- 2022-06-29
- Filing Date
- 2023-05-02
- Publication Date
- 2025-01-03
AI Technical Summary
There are insufficient flow distribution and reactant flow efficiency of bipolar plates in existing fuel cell stacks, resulting in greater flow resistance and affecting the overall performance of the battery stack.
A bipolar plate structure is designed, consisting of two superimposed half plates, with three adjacently arranged ports for supplying or discharge of fluids, and for distributing fluids through four flat flow fields, including a coolant flow field, Dual and triple dielectric flow fields, the flow path of the fluid is optimized with the imprinted structure and support to reduce drag.
The uniform distribution of fluids and the optimization of flow paths are achieved, the flow resistance is reduced, and the efficiency and performance of the fuel cell stack are improved.
Smart Images
Figure CN119256415A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to a bipolar plate intended for use in an electrochemical cell stack according to the preamble of claim 1. The invention also relates to a method for producing such a bipolar plate. Background Art
[0002] For example, DE 10 2005 057 045 A1 discloses a universal bipolar plate and a fuel cell unit constructed therewith. The known bipolar plate consists of a cathode-side partial plate and an anode-side partial plate, i.e. two half plates. An inner space through which a flow can pass is formed between the half plates. Other fluids, i.e. the working medium of the fuel cell unit, flow around the outer side of the bipolar plate. In the distribution area of the bipolar plate, the two half plates are supported against each other by means of a raised negative support point.
[0003] As with the bipolar plate according to DE 10 2005 057 045 A1, in many other possible designs of bipolar plates, three ports, i.e. one port for the coolant and two ports for the working medium, are arranged adjacent to one another. In this context, reference is made by way of example to the documents US 10,381,675 B2 and DE 10 2014 206 333 A1. In both cases, there is an overlap between the different channels formed between the inlet or outlet, i.e. the ports, and the active field of the fuel cell. Other possible designs of bipolar plates including flow channels are described, for example, in the documents DE 10 2013 210 542 A1, US 9,685,664 B4 and US 9,337,498 B2.
[0004] The design of bipolar plates and entire fuel cells disclosed in documents EP 3 577 708 B1 and EP 3 167 505 B1 is intended to achieve improved flow distribution and reactant flow. Both documents relate to fuel cells with gas diffusion layers and catalytic substances. For example, another fuel cell with a flow distributor is described in EP 2 926 399 B1. Summary of the invention
[0005] The object of the present invention is to further develop a bipolar plate suitable for use in a fuel cell stack in terms of flow-related aspects as well as production-related aspects compared to the above-mentioned prior art.
[0006] According to the invention, this object is achieved by a bipolar plate having the features of claim 1. The bipolar plate can be produced according to the method of claim 10.
[0007] Bipolar plates suitable for use in electrochemical cell stacks, in particular fuel cell stacks, consist of two superimposed, interconnected half-plates according to known basic concepts. The bipolar plate has three ports arranged adjacent to each other for supplying or discharging a fluid. For example, a first arrangement of three ports is provided for supplying a fluid, and a second arrangement of three ports is provided for discharging a fluid. The fluid can also flow in countercurrent, so that in the three ports arranged adjacent to each other, a single port is provided for guiding the fluid, which flows through or around the bipolar plate in the opposite direction to the fluid passing through the other two ports in the same row of ports. These ports are also referred to as manifold openings or simply manifolds.
[0008] The substantially centrally located extension section of the bipolar plate is assigned to the effective field of each electrochemical cell, i.e., the area where the desired electrochemical reaction occurs, wherein the term "effective field" is also used for the corresponding section of the bipolar plate. In many designs, the effective field of the bipolar plate has a rectangular basic shape. In addition, there is a distribution field of the bipolar plate, which connects the port to the effective field, i.e., the distribution field is designed to conduct three different fluids between the port and the effective field. A flow space for one of the three fluids is formed between the half plates. This is usually a flow space for a coolant, in particular cooling water. On the outer side of the half plate, a flow space for two other fluids, i.e., a working medium usually used for electrochemical cells, is formed at the same time.
[0009] According to the claim, the distribution field comprises, in a plan view of the half-plate, four flat flow fields, each of which has a triangular basic shape:
[0010] - a coolant flow field leading to a central port among the three ports;
[0011] - two dual-medium flow fields, each of which adjoins the coolant flow field at one end and opens into one of the two external ports at the other end, and which are designed to allow the coolant to flow through together with the working medium as another fluid in layers parallel to each other;
[0012] A three-medium flow field, which adjoins the two two-medium flow fields, opens into the effective field and is designed for the coolant to flow through together with the working medium as the other fluid in three mutually parallel superimposed layers.
[0013] Here, the half-plates consist of embossed structures, in particular annular structures, which are designed as points in each of the four flow fields, i.e. in an island-like form, so that the half-plates bear both against each other and against flat parts arranged outside the half-plates. In addition to flow fields having a basic triangular shape, flow fields having other shapes, such as squares or pentagons, are also possible. This applies in particular to the coolant flow field and the two lateral flow fields, i.e., dual-medium flow fields. In a typical method, all four flow fields act as pressure loss control flow fields during operation of the electrochemical cell stack. With regard to the use of parallel layers in which the medium flows in each layer, this should be understood to mean that the layers are arranged substantially parallel to each other, i.e., one of them is located above the other, wherein flow components perpendicular to the planes given by the individual layers may also occur.
[0014] In the plan view of the bipolar plate, there can be a single point where all four flow fields meet. This is especially true for designs with triangular flow fields. The first flow field connected to the central port and the fourth flow field can present an isosceles triangle, all three media flow through the fourth flow field and the fourth flow field is arranged closest to the effective field. Two dual-medium flow fields that do not usually present an isosceles triangle can have a similar design.
[0015] In each of the four flow fields that are part of the distribution field, the fluid in this flow field is diffused, or two or three different fluids flowing in separate, superimposed layers are diffused on the surface. The stacking of these layers is always consistent. This means, for example, that the medium, i.e. the fluid, located in the uppermost layer is only conducted in this layer. The lack of transfer of the medium from one layer to another, for example from the top side of the bipolar plate to its bottom side, is particularly advantageous for the flow resistance that occurs during the operation of the cell stack, in particular the fuel cell stack.
[0016] According to one possible embodiment, the half-plates in the region of the coolant flow field are arranged to support similarly flat surrounding components lying against the battery stack. The proportion of the area in the region of the coolant flow field in which circular, in particular annular, supports are formed is relatively small compared to the area adjacent to the components, which keep the half-plates at a certain distance from each other. The height of these supports corresponds to half of the maximum distance between the two half-plates, provided that the embossing depth of the two half-plates is the same. In the flow space through which the coolant flows, the supports represent pin-shaped barriers, which on the one hand do not significantly reduce the free flow cross section, and on the other hand ensure uniform distribution of the coolant. This also applies to variants in which the coolant is supplied or discharged through multiple ports.
[0017] As far as the dual medium flow field is concerned, according to a possible embodiment, the half-plate in the area of these flow fields is arranged exactly on one outer side for supporting flat against a similarly flat surrounding part, while the half-plate forming the opposite outer side is arranged for being arranged substantially spaced apart from the similarly flat surrounding part. Thus, three planes are provided that can be distinguished from each other, namely a central plane in which the two half-plates are tangential to each other, a plane in which one of the two half-plates is in flat contact with the surrounding part, and another plane described by the other half-plate, which is raised in a defined manner from the flat surrounding part in order to provide a free flat flow cross section for the working medium. The distance between the latter planes is at most half of the maximum distance between the two half-plates. At the same time, the same half-plate defining the flow cross section is formed with a support, which protrudes beyond the plane parallel to the central plane and is intended to support the bipolar plate relative to the flat part that is greatly raised from the half-plate.
[0018] The mid-plane is generally understood to mean the plane in which the two half-plates bear flat against each other. This also applies to designs in which the different half-plates have different depths of drawing. In this case, the two half-plates protrude from the mid-plane by different distances.
[0019] In a three-medium flow field, each of the two half-plates can have a profile that corresponds substantially to the profile of a half-plate of a two-medium flow field that rises substantially flat from the surrounding components in terms of the presence of areas that rise flat from the central plane and of the supports that face outwards, wherein in the three-medium flow field, the distance of the areas of the half-plate that rise flat from the central plane and from the surrounding components is in each case smaller than the distance between the central plane in the two-medium flow field and a plane defined by one of the half-plates and spaced parallel to the surrounding components. Even in a three-medium flow field, in a typical design, the sum of the areas of all supports—in a plan view of the bipolar plate—is less than half of the total area of the corresponding flow field.
[0020] In dual and triple flow fields, there are different possibilities for the design and arrangement of the supports: for example, the layout of the bipolar plates can be designed so that the inward and outward facing supports of the half plates are offset from each other. Alternatively, the inward and outward facing supports of the half plates can also be arranged concentrically.
[0021] According to another possible improvement, a channel guide area of a distribution field is connected between the three-medium flow field and the effective field of the bipolar plate, and thus the entire electrochemical cell is connected, wherein the width of the distribution field can correspond to the width of the effective field and the width of the three-medium flow field. In this design, the various medium flows on the cathode side and the anode side and the coolant flow can be distributed in a uniform manner and well approximated over the width of the entire effective field. Specifically, the channel guide area can be designed using channels with uneven widths so as to achieve uniform flow distribution over the entire width.
[0022] The metal bipolar plate according to the invention can generally be produced by three-dimensionally structuring two half-plates, in particular two half-plates made of steel sheet or, for example, of a titanium alloy, by means of a forming process according to claim 10 and then joining them together. For example, the connection can be made by welding, welding or gluing. The half-plates can be formed using continuous and / or discontinuous processes. BRIEF DESCRIPTION OF THE DRAWINGS
[0023] Two exemplary embodiments of the present invention are described in more detail below with reference to the accompanying drawings. The drawings show the following in a partial, roughly simplified manner:
[0024] Figure 1 A cross section of a bipolar plate of an electrochemical cell stack is shown in a symbolic plan view,
[0025] Figure 2 Shown according to Figure 1 The structure of the coolant flow field in the distribution field area of the bipolar plate,
[0026] Figure 3 Shown according to Figure 1 The structure of the two-medium flow field and the three-medium flow field of the bipolar plate,
[0027] Figure 4 Shows the cross-attribution according to Figure 1 The flow field of the distribution field of the bipolar plate, that is, the cross section of the coolant flow field,
[0028] Figure 5 Shown through the Figure 1 A cross section of one of the two similarly designed dual-medium flow fields of a bipolar plate.
[0029] Figure 6 Shown through the Figure 1 The cross section of the three-medium flow field of the bipolar plate,
[0030] Figure 7 A cross section of another embodiment of a bipolar plate for an electrochemical cell stack is shown in simplified plan view,
[0031] Figure 8 Shown from the Figure 7 The cross section of the arrangement structure,
[0032] Fig. 9 Shown through the Figure 7 The cross section of the coolant flow field of the bipolar plate,
[0033] Fig.10 Shown through the Figure 7The cross section of the dual medium flow field of the bipolar plate, which dual medium flow field is intended for conducting coolant and one of the two working media,
[0034] Fig.11 Shown according to Figure 7 Cross section of the three-medium flow field of the bipolar plate. DETAILED DESCRIPTION
[0035] Unless otherwise stated, the following description relates to two exemplary embodiments.In all figures, components which correspond to one another or have substantially the same function are identified with the same reference numerals.
[0036] The bipolar plate marked with reference numeral 1 is a part of a PEM fuel cell stack that is not further shown. With regard to the basic structure and function of such a fuel cell system, reference is made to the prior art cited at the beginning. The bipolar plate 1 can be intended for fixed or mobile use, in particular in motor vehicles. If terms such as "top side" or "bottom side" are used below, this does not mean any statement about the actual installation position of the bipolar plate 1 in the adjacent structure. In particular, unlike what is shown in the figures, the bipolar plate 1 can be aligned vertically.
[0037] The bipolar plate 1 consists of two profiled half-plates 2, 3. The embossed structure of the half-plates 2, 3 is generally designated 4. In the present case, the bipolar plate 1 has an overall rectangular rather than square basic shape, wherein Figure 1 and Figure 7 Only one of the narrow sides and a portion of the long sides can be seen. Other designs of the bipolar plate 1, such as a square or bone shape are also possible.
[0038] There are a plurality of ports 5, 6, 7 on the narrow sides of the drawn bipolar plate 1. These are the port 5 for the cathode chamber of the fuel cell, the port 6 for the coolant and the port 7 for the anode chamber. The ports 5, 6, 7 are arranged in a row next to each other, wherein the port 6 for the coolant is located between the ports 5, 7 for the working medium. In an embodiment, the ports 5, 7 are square, i.e., trapezoidal in shape, while the port 6 has an elongated rectangular shape extending along the narrow sides of the half-plates 2, 3, in a plan view.
[0039] The arrangement of the three ports 5, 6, 7 adjoins a distribution field, referenced as a whole by 8, which is fluidically connected between the ports 5, 6, 7 of the bipolar plate 1 and the active field 9. The widths of the individual ports 5, 6, 7 measured at the transition to the distribution field 8 are referenced by b5, b6, b7, respectively. The distribution field 8 comprises a channel guide region, referenced by 18, which adjoins the active field 9. Furthermore, the distribution field 8 is designed without any channel guides, as will be explained in more detail below.
[0040] Adjacent the port 6 is a coolant flow field 10 which represents one of four distinguishable flow fields 10, 12, 14, 16 of which the distribution field 8 consists except for the channel guide area 18. Each of the flow fields 10, 12, 14, 16 has a triangular basic shape.
[0041] Figure 4 and Fig. 9 A possible cross-sectional design of the coolant flow field 10 is shown in FIG. The two half-plates 2, 3 are raised significantly from the central plane ME in which the half-plates 2, 3 touch each other, in order to provide the largest possible flow cross section for the coolant. The plane in which the half-plates 2, 3 are mainly located is at a distance h from the central plane ME. a最大 (anode side) or h k最大 (Cathode side). Other similar flat parts of the fuel cell stack (not shown) bear against continuous flat areas of the half-plates 2, 3, which are spaced a certain distance h from the central plane ME. a最大 or k最大 A pin-shaped support 11 which is circular in plan view is formed directly through the half-plates 2, 3 and holds the half-plates 2, 3 at a distance from each other.
[0042] In addition to the coolant, one of the two working media of the fuel cell also flows in the flow field 12. Therefore, the flow field 12 represents a dual-medium flow field. The same applies to the flow field 14. Compared with the coolant flow field 10, the free flow cross section of the coolant in the dual-medium flow fields 12, 14 is significantly smaller. In the case outlined in the figure, the two dual-medium flow fields 12, 14 are constructed identically and are arranged point-symmetrically to each other. On the contrary, for example, the anode port can be smaller than the cathode port, so that there is no symmetry.
[0043] One of the two half plates 2, 3 is constructed in the dual medium flow field 12, 14 in the same manner as in the coolant flow field 10. Figure 5 This applies to the upper half 2; Fig.10 This applies to the lower half 3. The aforementioned point symmetry does not necessarily exist and can be Figure 1 and Figure 7 As can be seen in FIG. 1 , it refers to the point where all flow fields 10 , 12 , 14 , 16 meet.
[0044] The second half plates 3, 2 are mostly located in a plane in the dual medium flow field 12, 14, which is offset from the central plane ME by a certain amount h. k1 、h a1 , where h k1 or a1 Less than h k最大 or a最大 . In accordance with Figure 5In the design of k1 , a support 13 is formed, which supports the half plate 3 both inwardly, i.e. towards the other half plate 2, and outwardly, i.e. towards the flat surrounding parts. The cathode gas passes through the flow field 12. The support 13 is annular in plan view. The same applies to the support 15 located in the flow field 14 through which the anode gas passes.
[0045] According to Figure 1 In contrast to the design of Figure 7 In the design, different local supports 19, 20, 21, 22 are provided in the dual-medium flow fields 12, 14 configured to conduct cathode or anode gas and in the three-medium flow field 16, which support the half plates 2, 3 in different directions and are arranged adjacent to each other in a plan view.
[0046] The three-medium flow field 16, which is the same as the flow fields 10, 12, and 14, is also based on Figure 1 The three-medium flow field is designed as an open flow field in the design of the three-medium flow field, which adjoins the two two-medium flow fields 12, 14 and the channel guide area 18 of the distribution field 8. In the exemplary embodiment, the width of the three-medium flow field 16, indicated as b16, corresponds to the width b9 of the effective field 9 and also corresponds to the width of the area 18. Figure 1 In the case of the three-medium flow field 16, a plurality of support members 17 are formed, which are annular in plan view like the support members 13 and 15.
[0047] In the three-medium flow field 16, the flows of the working medium and the cooling medium are projected into three layers one above the other, wherein the coolant flow represents the central layer. The flow cross section available to the coolant is limited at the top and bottom by the plane defined by the half plates 2, 3 and is reduced from the central plane ME by an amount h a2 or k2 Here, h a2 Less than h a1 And h k2 Less than h k1 In an exemplary embodiment, h a1 With h k1 Same and h a2 With h k2 same.
[0048] Reference numerals list
[0049] 1 Bipolar Plate
[0050] 2 half board
[0051] 3 Half Board
[0052] 4 Imprinted structure
[0053] 5 Cathode chamber port
[0054] 6 Coolant port
[0055] 7 Anode chamber port
[0056] 8 Distribution Field
[0057] 9 Effective Field
[0058] 10 Coolant flow field
[0059] 11 Supports in the coolant flow field
[0060] 12 Coolant and cathode side flow field
[0061] 13 Support in flow field 12
[0062] 14 Coolant and anode side flow field
[0063] 15 Support in flow field 14
[0064] 16 Flow fields of three fluids
[0065] 17 Support in flow field 16
[0066] 18 Channel guide area of the distribution field
[0067] 19 Partial support in flow field 12
[0068] 20 Partial support in flow field 12
[0069] 21 Partial support in flow field 16
[0070] 22 Partial support in flow field 16
[0071] b5 Width of port 5
[0072] b6 Width of port 6
[0073] b7 Width of port 7
[0074] b9 Width of the effective field
[0075] b16 Width of flow field 16
[0076] h a最大 Maximum embossing depth on the anode side
[0077] ha1, ha2: embossing depth on the anode side
[0078] hk1, hk2 Imprint depth on cathode side
[0079] h k最大 Maximum embossing depth on cathode side
[0080] ME midplane.
Claims
1. A bipolar plate (1) for an electrochemical cell, the bipolar plate consisting of two half-plates (2, 3) sitting one on the other, the bipolar plate having: three ports (5, 6, 7) arranged adjacent to one another; an active field (9); and a distribution field (8) connecting the ports (5, 6, 7) to the active field (9) and being designed to conduct three different fluids between the ports (5, 6, 7) and the active field (9), wherein: A flow space for one of the fluids is formed between the half plates (2, 3), and flow spaces for the other two fluids are formed on the outer sides of the half plates (2, 3), characterized in that the distribution field (8) comprises four flow fields (10, 12, 14, 16) of flat design, namely - a coolant flow field (10), said coolant flow field leading to said port (6) in the center; - two dual-medium flow fields (12, 14), each of which is adjacent to the coolant flow field (10) at one end and opens to one of the two ports (5, 7) at the other end, and each of which is designed to allow the coolant and the working medium as another fluid to flow through in layers parallel to each other; - a three-medium flow field (16) which is adjacent to the two two-medium flow fields (10), opens into the effective field (9), and is designed to allow a coolant and a working medium as another fluid to flow through in three layers parallel to each other, The half-plates (2, 3) are structured by means of an embossed structure (4), which is designed as a point, i.e. an island, in each of the four flow fields (10, 12, 14, 16), so that the half-plates (2, 3) bear both against each other and against a flat part arranged outside the half-plates (2, 3).
2. The bipolar plate (1) according to claim 1, characterized in that: The four flow fields (10, 12, 14, 16) of the distribution field (8) each have a triangular basic shape in a plan view of the half-plates (2, 3), wherein all four flow fields (10, 12, 14, 16) meet at a single point.
3. The bipolar plate (1) according to claim 1 or 2, characterized in that: The two dual-medium flow fields (12, 14) have similar designs.
4. The bipolar plate (1) according to any one of claims 1 to 3, characterized in that: The half plates (2, 3) are arranged in the region of the coolant flow field (10) for bearing against similarly flat surrounding components, wherein a circular, in particular annular, bearing element (11) is formed in a relatively small part of the region of the coolant flow field (10), which bearing element keeps the half plates (2, 3) at a certain distance from each other, the height (h a最大 ,h k最大 ) corresponds to half of the maximum distance between the half plates (2, 3).
5. The bipolar plate (1) according to any one of claims 1 to 4, characterized in that: The half-plates (2, 3) in the region of the dual-medium flow field (12, 14) are arranged exactly on one outer side for bearing against a similarly flat surrounding part, while the half-plates (3, 2) forming the respective opposite outer side are arranged for being arranged substantially spaced apart from the similarly flat surrounding part, wherein, measured from a central plane (ME) in which the two half-plates (2, 3) are tangential to each other, the majority of the half-plates (3, 2) which are substantially elevated from the surrounding part are located offset relative to the central plane (ME) by an amount (h) which is at most half of the maximum distance between the two half-plates. k1 ,h a1 ), and wherein the same half-plates (3, 2) simultaneously form supports (13, 15) which protrude beyond a plane parallel to the central plane (ME) and are arranged to bear against a flat part which rises significantly from the half-plates (3, 2).
6. The bipolar plate (1) according to claim 5, characterized in that: In the three-medium flow field (16), each of the two half-plates (2, 3) has a profile (4), which corresponds to the profile (4) of the half-plate (3, 2) of the two-medium flow field (12, 14) which is substantially raised flat from the surrounding parts in terms of the presence of the area raised flat from the central plane (ME) and the outwardly facing supports (17, 22), wherein in the three-medium flow field (16), the distance (h) of the half-plate (3, 2) from the central plane (ME) and the area raised flat from the surrounding parts is k2 ,h a2 ) is in each case smaller than the distance (h) between the central plane (ME) in the dual-medium flow field (12, 14) and a plane defined by one of the half plates (3, 2) and spaced parallel to the surrounding components. k1 ,h a1 ).
7. The bipolar plate (1) according to claim 5 or 6, characterized in that: The inwardly facing and outwardly facing supports (19, 20, 21, 22) of the half-plates (2, 3) are arranged offset to one another.
8. The bipolar plate (1) according to claim 5 or 6, characterized in that: The inwardly facing and outwardly facing supports (11, 13, 15, 17) of the half-plates (2, 3) are arranged concentrically with respect to one another.
9. The bipolar plate (1) according to any one of claims 1 to 8, characterized in that: The channel guide area (18) of the distribution field (8) is connected between the three-medium flow field (16) and the effective field (9), wherein the width of the channel guide area corresponds to the width (b9) of the effective field (9) and the width (b16) of the three-medium flow field (16).
10. A method for producing a bipolar plate (1) for an electrochemical cell, wherein: The two half-plates (2, 3) are three-dimensionally structured by means of a method according to claim 1 and are then permanently connected to one another.