A flow field structure of a fuel cell bipolar plate

Abstract

The present invention discloses a flow field structure of a fuel cell bipolar plate, including a bipolar plate body, which is composed of two plates, an anode plate and a cathode plate, which are bonded together. A "cross"-shaped boss array is provided on the surface of each plate. The "net-shaped cross grooves" between the bosses on the "convex side" of the cathode plate are the cathode flow path; the cross-shaped cross grooves between the bosses on the "convex side" of the anode plate are the anode flow path; the "concave sides" of the anode plate and the cathode plate are staggered and bonded, and the three-dimensional flow channel formed by the staggered overlap of the "concave cavity" array is the cooling flow path. The "cross"-shaped boss array design of the present invention connects all the flow channels on the cathode and anode flow paths, thereby improving the uniformity of fluid distribution; the forced convection effect of the "net-shaped cross grooves" between the bosses can enhance the mass transfer effect inside the fuel cell, has a high heat exchange efficiency, and effectively improves the reliability and durability of the fuel cell.

Description

Technical Field

[0001] The present invention relates to the technical field of fuel cells, and in particular to a flow field structure of a bipolar plate of a fuel cell. Background Art

[0002] Fuel cells are considered to be the most promising clean energy power generation devices. Due to their advantages such as zero emissions, high power density, high electrical efficiency and low noise, they are very suitable as a power source for electric vehicles, unmanned aerial vehicles, underwater submersibles, signal base stations, etc.

[0003] The mass transfer, heat transfer and drainage capabilities of the flow field are the main factors affecting the reliability, durability and output efficiency of fuel cells.

[0004] Generally, the mass transfer, heat transfer and drainage capabilities of fuel cells can be improved by improving materials, flow field design, operating conditions and other measures, among which improving flow field design is the most common method.

[0005] In the existing fuel cell technology, the bipolar plate cooling side flow field configuration is divided into parallel flow field, serpentine flow field, mixed flow field, point flow field and bionic flow field, etc. The basic characteristics of the above flow field configurations are: the flow channel mostly adopts a microchannel structure with a small cross section and a long flow path; and along the flow channel direction, the shape and area of ​​the cross-sectional area of ​​the flow channel do not change; due to the obstruction of the ridge, the flow channels are not connected, and the flow state is usually laminar.

[0006] In terms of the mass transfer performance of existing fuel cells, taking proton membrane fuel cells as an example, for the cathode and anode flow paths, the gas transmission mainly relies on diffusion. When the gas moves in laminar flow, the gas transfer to the MEA is relatively weak, and the mass transfer capacity is not strong.

[0007] As far as the heat transfer performance of existing fuel cells is concerned, taking proton membrane fuel cells as an example, for the cooling flow path, because the flow of the coolant is usually in a laminar state, the heat exchange between the coolant and the bipolar plate is laminar heat exchange, and the heat exchange efficiency is low; in addition, since each flow channel is relatively closed and the flow distribution consistency is poor, it is easy to cause uneven temperature distribution and local overheating, which in turn affects the reliability and durability of the fuel cell.

[0008] As far as the drainage performance of existing fuel cells is concerned, taking proton membrane fuel cells as an example, for the cathode flow path, especially under high current density conditions, the amount of liquid water generated in the fuel cell cathode increases significantly, and water flooding failures are prone to occur. Water flooding will hinder the transmission of gas reactants to the reaction site, and the oxidant gas supply will be seriously insufficient, resulting in a sharp increase in fuel cell output voltage fluctuations, reduced performance stability, and even shortened remaining life. The general way to improve the uniformity of the temperature field and reduce the temperature extremes is to increase the flow rate of the cooling solution, but theoretically under laminar conditions, due to the existence of the thermal boundary layer, simply increasing the flow rate will not only fail to effectively transfer heat, but will also inevitably lead to an exponential increase in auxiliary power consumption.

[0009] The current common flow field has certain limitations in improving mass transfer, heat transfer and drainage capabilities, so it is necessary to develop a new type of fuel cell bipolar plate structure. Summary of the invention

[0010] In view of the above shortcomings and deficiencies of the prior art, the present invention provides a flow field structure of a fuel cell bipolar plate, which has better mass transfer, heat transfer capacity and drainage effect. The plate structure of the present invention is simple, easy to process and form, and is very suitable for large-scale production.

[0011] The present invention adopts the following technical scheme: a flow field structure of a bipolar plate of a fuel cell, comprising a bipolar plate body, the bipolar plate body is composed of a cathode plate and an anode plate, and a "cross" shaped boss array is provided on the surface of the cathode plate and the anode plate;

[0012] Preferably, the "cross" boss has four corners A, B, C, and D, wherein the corners A and B have the same geometric features, and the corners C and D have the same geometric features. The mass transfer, heat transfer, and drainage characteristics of the flow field can be optimized by changing the geometric features of the boss corners. Preferably, the longitudinal half-length a, the transverse half-length b, and the height h of the "cross" boss can be adjusted according to the mechanical properties of the plate, and the edge of the top surface of the boss is rounded to avoid physical damage to the fuel cell membrane electrode. Preferably, the "cross" boss array arrangement is specifically an array composed of a cross-row arrangement, and its density can be adjusted by changing the row spacing and column spacing values; the values ​​of the row spacing and column spacing are set according to the mechanical and electrical properties of the plate and the thermal management requirements of the fuel cell.

[0013] Preferably, the cathode plate has a "cross"-shaped boss array arranged in a staggered manner, and on its "convex side", the "cross"-shaped boss array is arranged in a staggered manner, so that a mesh-like cross "groove" is formed between the bosses, which is called the cathode flow path, through which the oxidant gas passes; the flow field structure of the bipolar plate of the fuel cell described above can connect all the flow channels on the cathode flow path inside the fuel cell, improve the uniformity of fluid distribution, and the fluid continuously performs a forced convection flow of "diversion-confluence-diversion-confluence" during the flow process. In a proton membrane fuel cell, the membrane electrode will cover the top surface of the boss to form an air flow channel. The forced convection flow can promote the mixing of the consumption layer gas and the enrichment layer gas, and can promote the mixing of air and liquid water generated by the reaction, which on the one hand has the effect of enhancing mass transfer; on the other hand, it can promote the discharge of water generated under the ridge and in the diffusion layer, which can effectively avoid and alleviate the occurrence of flooding failures.

[0014] Preferably, the anode plate is also provided with an array of "cross"-shaped bosses arranged in a staggered pattern, and a mesh of cross-shaped "grooves" are formed between the bosses on the "convex side" thereof, which is referred to as the second flow path for the fuel gas. For example, in a proton membrane fuel cell, the membrane electrode will cover the top surface of the bosses to form a flow channel for hydrogen. The flow field structure of the bipolar plate of a fuel cell described above can connect all the flow channels on the anode flow path inside the fuel cell, thereby improving the uniformity of fluid distribution. During the flow process, the fluid continuously undergoes a forced convection flow of "diversion-merger-diversion-merger", which can promote the mixing of the consumption layer gas and the enrichment layer gas, thereby enhancing the effect of mass transfer.

[0015] Preferably, the "concave sides" of the cathode plate and the anode plate are staggered and bonded together, and the three-dimensional flow channel formed by the staggered overlap of the "cavity" array is a cooling flow path, through which the cooling medium passes. The flow field structure of a fuel cell bipolar plate can effectively induce the generation of micro-vortices in the cooling flow path, enhance heat exchange, and have a very high heat exchange efficiency. If the base material for the plate is metal, the anode plate and the cathode plate are welded together at the bonding surface position of the "concave side", which can reduce the contact resistance between the plates, improve the conductivity, and improve the structural strength of the bipolar plate.

[0016] Preferably, the shapes, specifications and parameters of the bosses respectively arranged on the anode plate and the cathode plate may be the same or different.

[0017] Preferably, when the bipolar plate substrate is made of metal, it may be stainless steel, titanium alloy, aluminum alloy, etc., and may be manufactured by stamping, rolling, or etching forming processes.

[0018] Preferably, when the bipolar plate substrate is made of graphite, it can be manufactured using a machine carving process.

[0019] Preferably, when the bipolar plate substrate is made of a graphite composite resin material, it can be manufactured using a molding or roll forming process.

[0020] As described above, the present invention has the following beneficial effects:

[0021] 1. It has good forced convection and drainage functions. While strengthening the mass transfer effect of the cathode and anode inside the fuel cell, it can promote the discharge of water generated under the ridge and in the diffusion layer, which can effectively avoid and alleviate the occurrence of flooding failures and improve the reliability and durability of the fuel cell.

[0022] 2. In the cooling flow path, it can effectively induce the generation of secondary eddy currents, intensify the heat convection exchange between the mainstream area and the near-wall area, enhance heat transfer, and thus improve heat exchange efficiency; at the same time, the coolant has good distribution consistency, which is conducive to reducing the extreme difference of the temperature field value and improving the uniformity of the temperature distribution of the flow field plate.

[0023] 3. The plate structure is simple and thin, and can well balance the interference problem between the three paths of "cathode flow path-anode flow path-cooling flow path" in the plate design, so that the physical function of each path can be optimally exerted. This structure is easy to process and form, suitable for batch manufacturing, with obvious cost advantages, and can greatly improve the specific power density of fuel cells. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is the structural diagram of the bipolar plate body;

[0025] Figure 2 (a)-(b) is a structural diagram of a boss style;

[0026] Figure 3 (a)-(b) is a structural diagram of boss style 2;

[0027] Figure 4 for Figure 1 Schematic diagram of the “AA” section;

[0028] Figure 5 Schematic diagram of the "concave side" of the anode plate;

[0029] Figure 6 Schematic diagram of cathode flow path cavity;

[0030] Figure 7 It is a schematic diagram of the cooling flow path cavity;

[0031] Figure 8 Schematic diagram of the anode flow path cavity;

[0032] In the figure: 1. bipolar plate body; 2. cathode plate; 3. anode plate; 4. boss; 5. groove; 6. top surface of boss; 7. fillet; 8. fitting surface; 9. welding point; 10. cavity; 11. groove plane; 12. side surface of boss. DETAILED DESCRIPTION

[0033] The present invention is described in detail below in conjunction with specific embodiments and drawings. It should be understood that the embodiments are only used to illustrate the present invention rather than to limit the present invention, and any modifications, equivalent substitutions, etc. made on the basis of the present invention are within the protection scope of the present invention.

[0034] like Figure 1 As shown, a flow field structure of a bipolar plate of a fuel cell includes a bipolar plate body 1, which is composed of a cathode plate 2 and an anode plate 3. The surfaces of the cathode plate 2 and the anode plate 3 are provided with an array of "cross" shaped bosses 4; the "convex side" of the cathode plate 2, the grooves 5 formed by the mesh cross between the bosses are the cathode flow path, through which the oxidant gas passes, such as Figure 6 As shown; the "convex side" of the anode plate 3, the groove 5 formed by the mesh cross between the bosses is the anode flow path, through which the fuel gas passes, such as Figure 8 As shown; the area formed by the "concave platform" array of the "concave side" of the cathode plate 2 and the anode plate 3 is a cooling flow path, through which the cooling medium passes, such as Figure 4 and Figure 7 shown.

[0035] Example 1

[0036] The shape specifications and array arrangement of the bosses in this embodiment are shown in Figure 2. The longitudinal half-length a, transverse half-length b, and height h of the "cross" boss 4 can be adjusted according to the mechanical properties of the electrode plate. Rounded corners 7 are set on the edge and bottom edge of the top surface 6 of the boss. The ratio a / b of the longitudinal half-length a to the transverse half-length b can be 0.2-5, and the height h of the boss can be 0.1-3mm; the array arrangement is specifically arranged in a cross-row form, and the density can be adjusted by changing the row spacing and column spacing values; the values ​​of the row spacing and column spacing are set according to the mechanical and electrical properties of the electrode plate and the thermal management requirements of the fuel cell.

[0037] On the "convex side" of the cathode plate 2, the "cross" bosses 4 are arranged in a cross-row arrangement, so that a mesh of cross grooves 5 are formed between the bosses, which is called the cathode flow path; in the hydrogen-oxygen fuel cell, the membrane electrode will cover the top surface 6 of the boss to form an air flow channel, and the air and the liquid water generated by the reaction will mix and flow together, such as Figure 6 shown.

[0038] The anode plate 3 also has a cross-shaped array of bosses arranged in a cross pattern. On its "convex side", a mesh of cross-shaped "grooves" is formed between the bosses, which is called the second flow path. For example, in a hydrogen-oxygen fuel cell, the membrane electrode will cover the top surface of the boss to form a flow channel for hydrogen, such as Figure 8 shown.

[0039] The "concave cavities" of the "concave side" of the cathode plate and the anode plate are overlapped and bonded to form a cooling flow path. If the plate substrate is made of metal, the bonding surfaces 8 of the "concave side" of the anode plate and the cathode plate are welded together through welding points 9. This can reduce the contact resistance between the plates, improve the conductivity, and improve the structural strength of the bipolar plate. Figure 5 shown.

[0040] It should be noted that the shape specifications and parameters of the bosses arranged on the anode plate and cathode plate of the fuel cell can be the same or different; the fluid flow direction of the cathode flow path and the anode flow path of the fuel cell can be countercurrent or parallel flow, and preferably, the fluid flow direction of the cooling flow path is cross flow.

[0041] Example 2

[0042] The shape specifications and array arrangement of the bosses of this embodiment are shown in FIG3. Compared with Embodiment 1, this embodiment adjusts the geometric features of the four corners A, B, C, and D of the bosses, which is specifically reflected in that the four corners A, B, C, and D of the boss style 2 are relatively "blunt", and the four corners A, B, C, and D of the boss style 1 are relatively "sharp", which can reduce the flow resistance of the cooling flow path and enhance the heat exchange capacity of the cooling flow path. A fillet 7 is set at the edge of the boss top surface 6, and a fillet 7 is set at the junction of the boss side and the groove plane. The ratio a / b of the longitudinal half length a to the transverse half length b is 0.2-5mm, and the height value h of the boss is 0.1-3mm. The rest is the same as Embodiment 1.

[0043] Example 3

[0044] In this embodiment, when the material of the bipolar plate substrate is metal, such as stainless steel, titanium alloy, aluminum alloy, etc., it can be manufactured by stamping, rolling, and etching processes.

[0045] Example 4

[0046] When the material for making the bipolar plate substrate described in this embodiment is graphite, it can be manufactured using a mechanical processing and molding process.

[0047] Example 5

[0048] When the bipolar plate substrate in this embodiment is made of a graphite composite resin material, it can be manufactured using a molding or roll forming process.

[0049] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made according to the scope of the patent application of the present invention should fall within the scope of the present invention.

Claims

1. A flow field structure of a fuel cell bipolar plate, characterized in that: The bipolar plate body comprises a cathode plate and an anode plate, wherein the surfaces of the cathode plate and the anode plate are provided with a "cross"-shaped boss array; the "convex side" of the cathode plate, the mesh-shaped cross "grooves" between the bosses are cathode flow paths, through which oxidant gas flows; the "convex side" of the anode plate, the mesh-shaped cross "grooves" between the bosses are anode flow paths, through which fuel gas flows; the "concave side" of the cathode plate and the anode plate are staggered and fitted, and the three-dimensional flow channel formed by the staggered overlap of the "cavity" array is a cooling flow path, through which cooling medium flows, and the cooling flow path can effectively induce the generation of secondary vortex; The "cross"-shaped boss has four corners and a cross-sectional shape. The ratio a / b of the longitudinal half length a and the transverse half length b of the boss is 0.2-5, and the height h of the boss is 0.1-3 mm. The "cross" shaped bosses are arranged in a cross-row to form an array; The fluid flow direction of the cathode flow path and the anode flow path of the fuel cell is countercurrent or parallel flow, and the fluid flow direction of the cooling flow path is cross flow; The mating surfaces of the "concave side" of the anode and cathode plates are connected together by welds.

2. The flow field structure of a fuel cell bipolar plate according to claim 1, characterized in that: Rounded corners are provided at the junctions of the edge of the boss top surface, the boss side surface and the groove plane.

3. The flow field structure of a fuel cell bipolar plate according to claim 1, characterized in that: The bipolar plate body substrate manufacturing material includes any one of stainless steel, titanium alloy, aluminum alloy, graphite, and composite graphite resin material.

4. A fuel cell using a polymer having ion exchange capability as an electrolyte, characterized in that: A flow field structure of a bipolar plate according to any one of claims 1 to 3 is adopted.

5. The fuel cell according to claim 4, characterized in that The fuel cells include direct formic acid fuel cells, microbial fuel cells, renewable fuel cells, direct methanol fuel cells, reformed methanol fuel cells, direct ethanol fuel cells, ammonia fuel cells, and proton membrane fuel cells.

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