Fuel cell flow field structure and bipolar plate

Abstract

The present invention discloses a fuel cell flow field structure and a bipolar plate, belonging to the field of fuel cell technology. The present invention includes a body, the surface of the body is provided with several first ridges extending along a first direction, the first ridges are wavy; a second ridge is provided between adjacent first ridges, the second ridge is a wave-like broken line; a first groove is formed between the first ridge and the second ridge along the second direction, a second groove is formed between the second ridge and the first ridge along the second direction, the shape of the second groove is axially symmetrical with the shape of the first groove, the second groove is staggered relative to the first groove along the first direction, and the second direction is perpendicular to the first direction. The flow field structure in the present invention can improve the water management ability and battery performance of the battery, and has a simple design and convenient processing, which is conducive to the large-scale production and application of fuel cells.

Description

Technical Field

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

[0002] Fuel cells have attracted more and more attention in modern society because they are not restricted by the Carnot cycle in the energy conversion process, have high energy conversion efficiency, low pollution emissions, and are environmentally friendly. They are considered to be the preferred clean and efficient power generation technology in the 21st century. Among them, bipolar plates, gas diffusion layers, catalyst layers and membranes are indispensable components of fuel cells, and their optimized design may directly affect the performance and life of fuel cells. In the actual application of fuel cells, optimizing the bipolar plate structure by flow field design is one of the most common methods to improve the hydrothermal management of fuel cells and improve battery performance. The flow field structure of fuel cells can be divided into two-dimensional flow fields and three-dimensional flow fields according to whether it can generate velocity components facing the membrane electrode direction. Among them, the three-dimensional flow field structure has received widespread attention from researchers since it was used in the Mirai series fuel cell vehicles of Toyota Motor Corporation in Japan. However, compared with the two-dimensional flow field, the structural design of the three-dimensional flow field is complex, and there are higher requirements for the treatment and processing technology of the flow field plate, which greatly increases the cost of the fuel cell stack and is not conducive to its large-scale commercial promotion. Compared with the three-dimensional flow field, the traditional two-dimensional flow field (such as the straight flow channel, S-shaped flow channel, serpentine flow channel, etc.) is simple to process, which can greatly reduce the processing cost of the fuel cell and is more suitable for large-scale production. However, the turbulence of the reaction gas in the traditional two-dimensional flow field structure is low, and the mass transfer mainly depends on diffusion. In addition, under high flow density, it is easy to cause local raw gas shortage and water management problems in the battery, which limits the performance of the fuel cell. The Chinese patent application with application number: 202010440995.9 and invention name "A fuel cell bipolar plate" discloses a fuel cell S-shaped flow field structure: by setting a trapezoidal protrusion in the S-shaped flow channel to improve the mass transfer performance of the fuel cell under high current density, but this method can only improve the mass transfer capacity above the protrusion on the one hand, and has limited effect on improving battery performance; on the other hand, due to the trapezoidal protrusion obstacle in the flow channel, it will seriously hinder the flow of gas in the flow channel, increase the kinetic energy loss of the flowing gas, increase the energy consumption of auxiliary systems such as compressors, and increase the difficulty of flow field processing. The technical solution disclosed in the Chinese patent application with application number: 201911311163.0, and the invention name is "An air-cooled fuel cell cathode flow field structure and its manufacturing" also has the same problem as above. Therefore, it is necessary to develop a two-dimensional flow field structure with simple processing, good mass transfer effect and low flow field pressure drop to meet the large-scale commercialization needs of fuel cells. Summary of the invention

[0003] The purpose of the present invention is to provide a fuel cell flow field structure to compensate for the above-mentioned technical defects, which is used to improve the oxygen mass transfer capacity of the traditional two-dimensional flow channel, which is beneficial to the fuel cell, especially the water management process under the flow channel ridge, and promotes the mass transfer process of reactants in the flow field under high current density without significantly increasing the flow field pressure drop, thereby improving the performance of the fuel cell.

[0004] The first aspect of the present invention protects a fuel cell flow field structure, including a main body, a surface of the main body is provided with several first ridges extending along a first direction, the first ridges are wavy; second ridges are provided between adjacent first ridges, the second ridges are wavy broken line type; a first groove is formed between the first ridge and the second ridge along the second direction, a second groove is formed between the second ridge and the first ridge along the second direction, the shape of the second groove is axially symmetrical with the shape of the first groove, the second groove is staggered relative to the first groove along the first direction, and the second direction is perpendicular to the first direction.

[0005] Furthermore, the first groove is composed of a plurality of identical groove units arranged along the first direction, and the groove unit is formed by sequentially connecting a semicircular wide groove, a connecting groove and a rectangular narrow groove.

[0006] Furthermore, the wide groove is an axisymmetric structure, the wide groove has a first axis of symmetry, and the width of the wide groove on the first axis of symmetry is d1; the narrow groove is also an axisymmetric structure, the narrow groove has a second axis of symmetry, and the narrowness of the narrow groove on the second axis of symmetry is d2; d1>d2>0.2mm.

[0007] Furthermore, the first ridge is composed of a plurality of arc units forming the wave-shaped structure, the outer arc radius of the arc unit is r1, the inner arc radius of the arc unit is r2, the width of the second ridge is d3, and d3=r1-r2=(d1+d2) / 2.

[0008] Furthermore, the depth of the wide groove and the narrow groove is not less than 0.2 mm.

[0009] Furthermore, the widths of the first ridge and the second ridge are equal.

[0010] The present invention also protects a bipolar plate comprising any one of the fuel cell flow field structures described above.

[0011] The present invention has the following advantages:

[0012] (1) The fuel cell flow field structure described in the present invention can effectively increase the turbulence of the reaction gas in the flow field through the combination of wide grooves and narrow grooves without significantly increasing the pressure drop of the flow field structure, thereby improving the mass transfer capacity inside the battery, reducing the concentration polarization of the fuel cell under high current density, and improving the performance of the fuel cell.

[0013] (2) The flow channels described in the present invention are arranged in a staggered structure, with narrow grooves on both sides of a wide groove or wide grooves on both sides of a narrow groove. The flow velocity difference between different flow channels is utilized to generate a pressure difference between different flow channels, which can discharge liquid water under the ridges between adjacent flow channels, further improve the mass transfer process under the ridges of the flow channels, and enhance the water management capability of the fuel cell.

[0014] (3) The flow field structure of the present invention is simple in design and easy to process, which is conducive to the large-scale production and application of fuel cells. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 Schematic diagram of the structure of the fuel cell flow field in an embodiment of the present invention.

[0016] Figure 2 for Figure 1 A partial enlarged schematic diagram of .

[0017] Figure 3 Schematic diagram of the arc unit structure.

[0018] Figure 4 The IV curves of the batteries of the embodiments and comparative examples are shown in FIG.

[0019] In the figure, 1, first groove; 11, wide groove; 12, connecting groove; 13, narrow groove; 2, first ridge; 3, second ridge; 4, second groove; 5, body. DETAILED DESCRIPTION

[0020] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail in combination with the following specific embodiments and with reference to the accompanying drawings, but the present invention is not limited to these embodiments.

[0021] The specific technical solutions proposed by the present invention are as follows:

[0022] A fuel cell flow field structure, the flow field structure includes a main body 5; a plurality of first ridges 2 extending along a first direction are formed on the surface of the main body 5; the first ridges 2 are wavy or corrugated along their extension direction; a plurality of second ridges 3 arranged along a second direction are also formed on the surface of the main body 5, and first grooves 1 and second grooves 4 are formed between adjacent first ridges 2 and second ridges 3; first ridges 2 and second ridges 3.

[0023] Based on the above scheme, preferably, the widths of the first ridge 2 and the second ridge 3 are equal, and the widths of the first ridge 2 and the second ridge 3 along the first direction remain unchanged, which is conducive to controlling the structural parameters of the flow field and ensuring that the contact resistance between each flow channel is relatively consistent.

[0024] Based on the above scheme, preferably, the wide groove 11 and the narrow groove 13 are symmetrical structures; the distance on the symmetric midline of the wide groove 11 is d1, and the distance on the symmetric midline of the narrow groove 13 is d2. The change in the groove size can increase the turbulence of the reaction gas in the flow channel, which is beneficial to the mass transfer process of the reaction gas toward the membrane electrode; d1>d2>0.2mm, to prevent the design size of the flow channel from being too narrow to increase the pressure drop of the flow field.

[0025] Based on the above scheme, preferably, the depth of the wide groove 11 and the narrow groove 13 can be a constant value or a non-constant value, and the flow channel depth should be greater than 0.2 mm to prevent the design size of the flow channel from being too narrow to increase the pressure drop of the flow field.

[0026] Based on the above scheme, preferably, multiple flow channels extending along the first direction are arranged in a staggered structure, with narrow grooves 13 on both sides of the wide groove 11 or wide grooves 11 on both sides of the narrow groove 13; the staggered arrangement can effectively utilize the flow velocity difference of the gas between different flow channels, thereby generating a pressure difference between different flow channels, discharging liquid water under the ridges between adjacent flow channels, thereby improving the water management capability of the fuel cell and further improving the mass transfer process under the flow channel ridges.

[0027] The present invention also provides a bipolar plate of a fuel cell flow field structure for use.

[0028] Example 1

[0029] The embodiment of the present invention provides a fuel cell flow field plate using a fuel cell flow field structure, such as Figure 1 As shown, the flow field plate uses a 3 mm thick graphite plate as a substrate material, namely the body 5, and the flow field structure area is composed of multiple rows or columns of repeated unit flow channels that are alternately connected.

[0030] , where d1 is 1.5mm and d2 is 0.5mm. The change in the flow channel size can increase the turbulence of the reaction gas in the flow channel, which is beneficial to the mass transfer process of the reaction gas to the membrane electrode; and d2 is 0.5mm, which is greater than 0.2mm, to prevent the design size of the flow channel from being too narrow to increase the pressure drop of the flow field.

[0031] Based on the above solution, preferably, the depth of the wide groove 11 and the narrow groove 13 is 0.4 mm, which is greater than 0.2 mm, to prevent the overly narrow flow channel design size from increasing the pressure drop of the flow field.

[0032] Based on the above solution, preferably, the first ridge 2 and the second ridge 3 have the same width of 1 mm to ensure that the contact resistance between the flow channels is relatively consistent.

[0033] Based on the above solution, preferably, r1 is 9.0 mm, r2 is 8.0 mm, d3 is 1.0 mm, and has the following relationship d3=r1-r2=(d1+d2) / 2.

[0034] The anode flow field plate of this embodiment uses a straight channel structure, and the channel depth and width are both 1 mm. The test conditions of the embodiment are as follows: the battery pressure is 50 kPa, the battery temperature is 60°C, the anode uses dry gas, the cathode uses 80% humidified air, the cathode stoichiometric ratio is 3.0, and the anode pulse exhaust is used. The polarization curve is shown in Figure 3 .

[0035] Comparative Example 1

[0036] As a comparison, this comparative example will demonstrate a fuel cell flow field plate using a traditional corrugated flow channel flow field structure.

[0037] The fuel cell flow field plate with a corrugated flow channel structure uses a 3mm thick graphite plate as a substrate material, a flow channel processing depth of 0.4mm, and a flow channel width of 1mm, and is used as the flow field plate on the cathode side of the fuel cell.

[0038] The anode flow field plate of this comparative example uses a straight channel structure, and the channel depth and width are both 1 mm. The test conditions of the embodiment are as follows: the battery pressure is 50 kPa, the battery temperature is 60°C, the anode uses dry gas, the cathode uses 80% humidified air, the cathode stoichiometric ratio is 3.0, and the anode pulse exhaust is used. The polarization curve is shown in Figure 3 .

[0039] The above are only preferred specific implementation methods of the present invention and are not intended to limit the present application. Any technician familiar with the profession, without departing from the technical scope disclosed by the present invention, making slight changes or modifications using the above-disclosed technical contents are equivalent to equivalent implementation cases and should be covered within the protection scope of the present invention.

Claims

1. A fuel cell flow field structure, characterized in that: The invention comprises a body (5), wherein a surface of the body is provided with a plurality of first ridges (2) extending along a first direction, wherein the first ridges (2) are wavy; second ridges (3) are provided between adjacent first ridges (2), wherein the second ridges (3) are quasi-wavy broken line-shaped; a first groove (1) is formed between the first ridge (2) and the second ridge (3) along the second direction, and a second groove (4) is formed between the second ridge (3) and the first ridge (2) along the second direction, wherein the second groove (4) is staggered relative to the first groove (1) along the first direction, and the second direction is perpendicular to the first direction; The first groove (1) is composed of a plurality of identical groove units arranged along the first direction, wherein the groove unit is formed by sequentially connecting a semicircular wide groove (11), a connecting groove (12) and a rectangular narrow groove (13); The wide groove (11) is an axisymmetric structure, the wide groove (11) has a first axis of symmetry, and the width of the wide groove (11) on the first axis of symmetry is d1; the narrow groove (13) is also an axisymmetric structure, the narrow groove (13) has a second axis of symmetry, and the width of the narrow groove (13) on the second axis of symmetry is d2; d1>d2>0.2 mm; The first ridge (2) is composed of a plurality of arc-shaped units forming the wave-shaped structure, the outer arc radius of the arc-shaped unit is r1, the inner arc radius of the arc-shaped unit is r2, the width of the second ridge (3) is d3, and d3=r1-r2=(d1+d2) / 2.

2. The fuel cell flow field structure according to claim 1, characterized in that: The depth of the wide groove (11) and the narrow groove (13) are both not less than 0.2 mm.

3. The fuel cell flow field structure according to claim 1, characterized in that: The widths of the first ridge (2) and the second ridge (3) are equal.

4. A bipolar plate, characterized in that: A fuel cell flow field structure comprising any one of claims 1 to 3.

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