A gas distribution structure in the flow field transition zone of a graphite bipolar plate

Abstract

A graphite bipolar plate flow field transition zone gas distribution structure belongs to the field of fuel cell technology. The graphite bipolar plate is provided with gas inlets and outlets, a flow field transition zone, and a working flow field. Layered gas guide strips are provided within the flow field transition zone to guide the gas. This graphite bipolar plate flow field transition zone gas distribution structure utilizes multiple layers of guide strips in the flow field transition zone, combined with support points to assist in flow guidance. This ensures a more uniform flow of working gas into the working flow field, thereby improving fuel cell performance. It also significantly enhances the fuel cell's thermal control capabilities, ensuring fuel cell safety.

Description

Technical Field

[0001] The present invention belongs to the technical field of fuel cells, and in particular relates to a gas distribution structure in a flow field transition zone of a graphite bipolar plate. Background Art

[0002] Currently, the battery industry, including lithium-ion, lead-acid, nickel-metal hydride, and nickel-cadmium batteries, faces significant environmental and safety risks. With today's technological advancements, these batteries are no longer able to meet the demands of green energy. The development of new alternatives is urgent. Fuel cells, a power generation device that converts the chemical energy of fuel and oxygen into electricity through an electrochemical reaction under isothermal conditions without combustion, are considered the ultimate solution to the energy and environmental crisis.

[0003] Proton membrane fuel cells, with their excellent low-temperature and environmentally friendly properties, have become an ideal alternative for automotive power sources and energy storage power plants. Graphite bipolar plates, with their excellent corrosion resistance and good electrical conductivity, are currently a preferred choice for proton membrane fuel cell bipolar plates. However, the uniformity of gas distribution in the bipolar plate flow field is a key factor limiting fuel cell performance.

[0004] The flow field transition zones of graphite bipolar plates of proton membrane fuel cells currently on the market mainly include dot matrix, added guide strips, and no transition zone. When there are a large number of flow channels and the width of the inlet and outlet holes is smaller than the width of the parallel flow channels, adding guide strips to improve the uniformity of gas distribution is a common solution. Currently, the guide strips are all single-layer structures, and any slight change to any guide strip can affect the overall gas distribution. Summary of the Invention

[0005] In response to the above-mentioned problems existing in the prior art, the purpose of the present invention is to design and provide a technical solution for the gas distribution structure in the flow field transition zone of a graphite bipolar plate. The method adopts a layered gas guiding method and utilizes multi-layer gas guide strips, which significantly reduces the influence of changes in individual guide strips on the uniformity of gas distribution in the overall flow field, reduces the design difficulty, and reduces the influence of gas pressure fluctuations on gas distribution uniformity. In addition, the membrane electrode support points between the guide strips are arranged along the gas flow direction, which not only reduces the resistance to the gas, but also allows the gas to flow freely between points, and at the same time supports and fixes the membrane electrode, preventing the membrane electrode from being damaged by changes in gas pressure or flow rate.

[0006] The gas distribution structure in the flow field transition zone of a graphite bipolar plate includes a graphite bipolar plate, which is characterized in that gas inlets and outlets, a flow field transition zone, and a working flow field are arranged on the graphite bipolar plate, and gas guide strips for guiding gas in a graded manner are arranged in the flow field transition zone.

[0007] The gas distribution structure in the flow field transition zone of a graphite bipolar plate is characterized in that a plurality of membrane electrode support points are also provided on the flow field transition zone.

[0008] The gas distribution structure in the flow field transition zone of a graphite bipolar plate is characterized in that the width of the gas guide strip is 0.3-2 mm, preferably 0.5-1.5 mm, and more preferably 0.8-1 mm.

[0009] The gas distribution structure in the flow field transition zone of a graphite bipolar plate is characterized in that the gas guide strip is a convex rib structure.

[0010] The gas distribution structure in the flow field transition zone of a graphite bipolar plate is characterized in that the gas guide strips are multi-layer graded guide strips, including a first layer of gas guide strips, a second layer of gas guide strips, a third layer of gas guide strips...an Nth layer of gas guide strips, each layer of gas guide strips divides the blocks formed by the gas guide strips of the previous layer into several sub-blocks, and the number, position, length, spacing, etc. of the gas guide strips in the same layer are set separately.

[0011] The gas distribution structure of the flow field transition zone of the graphite bipolar plate is characterized in that the flow field transition zone includes an inlet flow field transition zone at the front end of the graphite bipolar plate and an outlet flow field transition zone at the rear end.

[0012] The gas distribution structure in the flow field transition zone of a graphite bipolar plate is characterized in that both the gas guide strip and the membrane electrode support point are provided with a draft angle, the cross-section of the gas guide strip is a trapezoidal structure, the top width is 0.3mm-2mm, preferably 0.5-1.2mm, more preferably 0.8-1mm, and the angle is 10-40°, preferably 20-30°; the membrane electrode support point is a truncated cone structure with a trapezoidal cross-section, the top diameter of the truncated cone is φ0.3mm-φ2mm, preferably φ0.5mm-φ1.2mm, more preferably φ0.8mm-φ1mm, and the taper is 10°-40°, preferably 20°-30°.

[0013] The gas distribution structure in the flow field transition zone of a graphite bipolar plate is characterized in that the spacing between the gas guide strips and the membrane electrode support points and between the membrane electrode support points is ≤3 mm, preferably 1.8-2.5 mm.

[0014] The gas distribution structure of the flow field transition zone of a graphite bipolar plate is characterized in that the membrane electrode support points are arranged in the gaps between the gas guide strips in a suitable arrangement and spacing, and the membrane electrode support points are arranged along the gas flow direction or evenly arranged in an array manner in the plane of the flow field transition zone.

[0015] The gas distribution structure of the flow field transition zone of a graphite bipolar plate is characterized in that the number of gas guide strips in the first layer is several, and the two ends of the gas guide strips in the first layer are respectively connected to the inlet and outlet and the working flow field, dividing the flow field transition zone into several blocks, so that the average flow rate of the fluid flowing into the working flow channel is equal between the blocks; the number of gas guide strips in the second layer is several, and the second layer of gas guide strips are led from the working flow field to a suitable position in the flow field transition zone, and the large blocks divided by the first layer of gas guide strips are further divided into small blocks, and the average flow rate of the fluid flowing into the working flow channel is equal between the small blocks; the above process can be repeated to perform the third division... the Nth division until all gases flowing into the working flow channel are evenly distributed.

[0016] The above-mentioned gas distribution structure in the flow field transition zone of the graphite bipolar plate adopts a layered gas guiding method and utilizes multi-layer gas guide strips, which significantly reduces the impact of changes in individual guide strips on the uniformity of gas distribution in the overall flow field, simplifies the design difficulty, and reduces the impact of gas pressure fluctuations on gas distribution uniformity; in addition, the membrane electrode support points between the guide strips are arranged along the gas flow direction, which not only reduces their resistance to the gas, but also allows the gas to flow freely between points, and at the same time supports and fixes the membrane electrode, preventing the membrane electrode from being damaged by changes in gas pressure or flow rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a schematic diagram of the partial structure of the flow field transition zone of the graphite bipolar plate of the present invention;

[0018] Figure 2 for Figure 1 Cross-sectional structural view of middle AA;

[0019] In the figure: 1-graphite bipolar plate, 2-membrane electrode support point, 3-gas guide strip, 301-first layer gas guide strip, 302-second layer gas guide strip, 303-third layer gas guide strip, 4-flow field transition zone, 5-working flow field, 6-gas inlet and outlet. DETAILED DESCRIPTION

[0020] The present invention will be further described below with reference to the accompanying drawings.

[0021] like Figure 1As shown, the gas distribution structure of the flow field transition zone of the graphite bipolar plate includes a graphite bipolar plate 1, which is provided with gas inlet and outlet ports 6, a flow field transition zone 4, and a working flow field 5. The flow field transition zone 4 is provided with gas guide strips 3 for layered gas guidance. The flow field transition zone 4 includes an inlet flow field gas distribution area at the front end of the graphite bipolar plate 1 and an outlet flow field gas concentration area at the rear end. The gas guide strips 3 are three-layer graded guide strips, including three first-layer gas guide strips 301, six second-layer gas guide strips 302, and 20 third-layer gas guide strips 303. Each layer of guide strips divides the block formed by the guide strips of the previous layer into several sub-blocks. Specifically, one end of the first-layer gas guide strip 301 is connected to the vicinity of the gas inlet and outlet 6, and the other end is connected to the working flow field 5. When the working gas flows from the gas inlet and outlet 6 of the bipolar plate flow field to the inlet flow field transition zone 4, the first-layer gas guide strip 301 guides and separates the working gas into four large blocks, and ensures that the gas flow rate between the large blocks relative to the working flow channel is equal. The gas flow rate of the working flow channel is monitored using existing technology and obtained through computer fluid analysis, which will not be described in detail here. Specifically, the large blocks guided by the first-layer gas guide strip 301 are subjected to a second block diversion according to the gas distribution situation, and a second-layer gas guide strip 302 is set. The second-layer gas guide strip 302 further evenly distributes the gas in the large block, so that the gas flow rate between the small blocks in the large block relative to the working flow channel is equal. Specifically, the small blocks after the second diversion can be diverted for the third time according to the gas distribution, and a third layer of gas guide strips 303 are set. The third layer of gas guide strips 303 once again evenly distributes the gas in the small blocks so that the gas evenly enters the working flow channel.

[0022] Furthermore, several membrane electrode support points 2 are provided in the flow field transition zone 4. When arranged in the direction of gas flow, these support points 2 effectively complement the gas guide strips 3. The gaps between these points create conditions for gas redistribution due to pressure differentials. The number of membrane electrode support points 2 can be adjusted based on actual needs. The gas guide strips 3 and membrane electrode support points 2 support the membrane electrode, increasing its rigidity and preventing it from vibrating and tearing under the influence of gas pressure and airflow.

[0023] Furthermore, the membrane electrode support points 2 are truncated cone-shaped structures with a trapezoidal cross-section, with a top diameter of φ0.3mm-φ2mm, preferably φ0.5mm-φ1.2mm, and more preferably φ0.8mm-φ1.0mm, and a taper of 10-40°, preferably 20-30°. The spacing between the gas guide strips 3 and the membrane electrode support points 2, and between the membrane electrode support points 2, is ≤3mm, preferably 1.8-2.5mm. Both the gas guide strips 3 and the membrane electrode support points 2 are provided with a draft angle. The membrane electrode support points 2 are arranged in the gaps between the gas guide strips 3 with appropriate arrangement and spacing, and are arranged along the gas flow direction or evenly arranged in an array within the plane of the flow field transition zone 4.

[0024] Furthermore, the cross-section of the gas guide strip 3 is a trapezoidal structure, with a top width of 0.3-2 mm, preferably 0.5-1.2 mm, more preferably 0.8-1 mm, and an angle of 10-40°, preferably 20-30°; the gas guide strip 3 is a convex rib structure, and its top is tightly sealed with the proton membrane or membrane electrode.

[0025] In the present invention, the number, position, length, and spacing of the gas guide strips 3 in the same layer can also be set individually as needed. The number of the first-layer gas guide strips 301 is several, which divide the flow field over-plating area into several parts. The number of the second-layer gas guide strips 302 is several, and the second-layer gas guide strips 302 are led from the working flow field 5 to a suitable position in the flow field transition zone 4, and the large blocks divided by the first-layer gas guide strips 301 are divided again to form small blocks, and the average flow rate of the fluid in the flow channel between small blocks is equal; repeating the above process can be performed for the third division... the Nth division, until all flow channel gases are evenly distributed. The shape of the gas guide strips 3 can be set individually or uniformly, and changes in the shape of the guide strips in a small block do not affect the flow of flow channel gas in other large blocks.

[0026] The working process of the present invention is as follows:

[0027] When the working gas enters the flow field transition zone 4 from the inlet and outlet 6, the first layer of gas guide strips 301 distributes the gas into multiple blocks, so that the gas is evenly distributed regionally and prevents gas from flowing in the transition zone; after the first layer of guide and before the second layer of guide, the membrane electrode support points 2 are arranged to assist in guiding the airflow, and redistribute it according to the pressure and appropriate adjustment of the flow rate. After reaching the second layer of gas guide strips 302, the gas is isolated again to make the secondary distribution of the gas evenly distributed. Then the second layer of gas guide strips 303 repeats the distribution method of the previous layer until the gas is evenly distributed to a single flow channel. After each gas distribution is completed by the gas guide strips 3, the evenly distributed gas will no longer be allowed to flow arbitrarily, preventing uneven gas distribution caused by pressure, distance, etc. Changes in the shape of the gas guide strips 3 of the latter layer and the position of the membrane electrode support points 2 will not change the gas distribution in the flow field in another area.

[0028] The above technical solutions have been described in detail for the present invention, but are not intended to limit the scope of the present invention. It should be understood that any obvious changes or substitutions of the present invention by those skilled in the art based on the teachings of the present invention should also be considered as falling within the scope of protection of the present invention.

Claims

1. A gas distribution structure in a flow field transition zone of a graphite bipolar plate, comprising a graphite bipolar plate (1), characterized in that The graphite bipolar plate (1) is provided with gas inlet and outlet ports (6), a flow field transition zone (4), and a working flow field (5), and a gas guide strip (3) for guiding gas in a graded manner is provided in the flow field transition zone (4); the flow field transition zone (4) includes an inlet flow field transition zone at the front end of the graphite bipolar plate (1) and an outlet flow field transition zone at the rear end; The gas guide strips (3) are multi-layer graded guide strips, including a first layer of gas guide strips (301), a second layer of gas guide strips (302), a third layer of gas guide strips (303) ... an Nth layer of gas guide strips, each layer of gas guide strips divides the block formed by the gas guide strips of the previous layer into a plurality of sub-blocks, and the number, position, length and spacing of the gas guide strips in the same layer are set separately; The number of the first-layer gas guide strips (301) is several, and the two ends of the first-layer gas guide strips (301) are respectively connected to the gas inlet and outlet (6) and the working flow field (5), dividing the flow field transition zone (4) into several blocks, so that the average flow rate of the fluid flowing into the working flow channel between the blocks is equal; the number of the second-layer gas guide strips (302) is several, and the second-layer gas guide strips (302) are led from the working flow field (5) to a suitable position in the flow field transition zone (4), and the large blocks divided by the first-layer gas guide strips (301) are divided again to form small blocks, and the average flow rate of the fluid flowing into the working flow channel between the small blocks is equal; repeat the above process for the third division...Nth division, until all gases flowing into the working flow channel are evenly distributed; A plurality of membrane electrode support points (2) are also provided on the flow field transition zone (4). The membrane electrode support points (2) are arranged in the gaps between the gas guide strips (3) in a suitable arrangement manner and spacing. The membrane electrode support points (2) are arranged along the gas flow direction or are evenly arranged in an array manner in the plane of the flow field transition zone (4).

2. A graphite bipolar plate flow field transition zone gas distribution structure according to claim 1, characterized in that The width of the gas guide strip (3) is 0.3-2 mm.

3. A graphite bipolar plate flow field transition zone gas distribution structure according to claim 1, characterized in that The width of the gas guide strip (3) is 0.5-1.5 mm.

4. A graphite bipolar plate flow field transition zone gas distribution structure according to claim 1, characterized in that The width of the gas guide strip (3) is 0.8-1 mm.

5. The gas distribution structure of the flow field transition zone of the graphite bipolar plate according to claim 1, characterized in that The gas guide strip (3) is a convex rib structure.

6. A graphite bipolar plate flow field transition zone gas distribution structure according to claim 1, characterized in that The gas guide strip (3) and the membrane electrode support point (2) are both provided with a draft angle. The cross section of the gas guide strip (3) is a trapezoidal structure, the width of the top is 0.3mm-2mm, and the angle is 10-40°. The membrane electrode support point (2) is a truncated cone structure with a trapezoidal cross section, the diameter of the truncated cone top is φ0.3mm-φ2mm, and the taper is 10°-40°.

7. The gas distribution structure of the flow field transition zone of the graphite bipolar plate according to claim 1, characterized in that The gas guide strip (3) and the membrane electrode support point (2) are both provided with a draft angle. The cross section of the gas guide strip (3) is a trapezoidal structure, the top width is 0.5-1.2 mm, and the included angle is 20-30°. The membrane electrode support point (2) is a truncated cone structure with a trapezoidal cross section, the top diameter of the truncated cone is φ0.8 mm-φ1 mm, and the taper is 20°-30°.

8. The gas distribution structure of the flow field transition zone of a graphite bipolar plate according to claim 1, characterized in that The spacing between the gas guide strip (3) and the membrane electrode support point (2) and the membrane electrode support point (2) is ≤3 mm.

9. The gas distribution structure of the flow field transition zone of a graphite bipolar plate according to claim 1, characterized in that The distance between the gas guide strip (3) and the membrane electrode support point (2) and between the membrane electrode support point (2) is 1.8-2.5 mm.

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