Gas flow channel forming assembly for fuel cell and fuel cell

Abstract

The present invention discloses a gas flow channel forming assembly for a fuel cell and a fuel cell. The gas flow channel forming assembly includes at least two stacked gas flow channel forming plates, each gas flow channel forming plate is provided with through holes arranged at intervals, and each corresponding group of through holes on each gas flow channel forming plate overlaps and penetrates end to end to form a gas flow channel extending from one end of the gas flow channel forming assembly to the other end. The gas flow channel forming assembly for the fuel cell of the present invention is assembled into a gas flow channel forming assembly by using at least two stacked gas flow channel forming plates. When the gas flows in the gas flow channel, it alternates up and down between the gas flow channel forming plates to achieve a flow component perpendicular to the flow channel surface. Compared with the structure formed by stamping a metal microporous mesh, the preparation difficulty is greatly reduced, the cost is reduced, and no complex anti-corrosion treatment process is required, and the formed surface does not have warping.

Description

Technical Field

[0001] The present invention relates to the technical field of fuel cells, and in particular to a gas flow channel forming component for a fuel cell and a fuel cell. Background Art

[0002] The structure of a fuel cell includes a fuel cell unit for power generation, a guide plate for current output of the fuel cell, etc. The fuel cell unit consists of a membrane electrode assembly (MEA) and bipolar plates and sealing wires that clamp and fix the membrane electrode assembly. The membrane electrode assembly includes an electrolyte layer and a carbon paper or carbon cloth diffusion layer that sandwiches the electrolyte layer. The bipolar plates are mostly metal surface coated plates, or graphite and graphite composite plates. The sealing wires are elastic sealing materials.

[0003] The surface of the bipolar plate is provided with a gas flow channel for passing gas. In the prior art, the gas flow channel is generally a groove arranged on the surface of the bipolar plate. For example, the invention with publication number CN104795574A discloses a metal bipolar plate for a fuel cell, including an anode metal plate and a cathode metal plate. The anode metal plate and the cathode metal plate are metal plates with the same structure; the metal plate has a first surface and a second surface, the first surface has a first flow channel formed by stamping and arranged in parallel, and the second surface has a second flow channel formed by stamping and arranged in parallel; the cathode metal plate and the anode metal plate are stacked, and the second flow channel on the second surface of the cathode metal plate is buckled with the second flow channel on the second surface of the anode metal plate to form a coolant flow channel; the first flow channel on the anode metal plate is a fuel gas flow channel, and the first flow channel on the cathode metal plate is an oxidizing gas flow channel. However, the gas flow channel with a structure similar to that in this technical solution cannot efficiently diffuse the gas to the membrane electrode assembly, and the power generation efficiency is low.

[0004] In order to improve the power generation efficiency of fuel cells, the invention patent application with publication number CN109616683A proposes a new stamped microporous flow field, which can improve the diffusion of gas in the membrane electrode diffusion layer by generating a flow component perpendicular to the flow channel surface. The specific structure is: a gas flow channel forming plate for a fuel cell, which is arranged between a membrane electrode assembly and a separator and constitutes a separator of a single cell of the fuel cell, and has: a plurality of protrusions, which are arranged in a first direction and a second direction intersecting the first direction, and the protrusions protrude toward the membrane electrode assembly; a gas flow channel portion, which is composed of a portion on the side of the gas flow channel forming plate corresponding to the membrane electrode assembly, including a portion between adjacent protrusions among the plurality of protrusions; a water flow channel portion, which is composed of a portion on the side of the gas flow channel forming plate corresponding to the separator, including the inside of the protrusion; and an opening portion, which is formed on the side wall of the protrusion and connects the inside and outside of the protrusion, and the opening portion is only provided in one place in one protrusion. However, the flow component perpendicular to the flow channel surface in this technical solution is realized by using a metal microporous mesh stamping structure. This structure requires high molding precision and high anti-corrosion treatment requirements, and the mesh flow channel surface after molding is warped, which increases the difficulty of fuel cell assembly. Summary of the Invention

[0005] In response to the above-mentioned deficiencies in the prior art, the present application provides a gas flow channel forming assembly and a fuel cell for a fuel cell that are relatively easy to prepare and assemble.

[0006] A gas flow channel forming assembly for a fuel cell, wherein the gas flow channel forming assembly is arranged between a membrane electrode assembly and a gas separator plate and is used to form a gas flow channel. The gas flow channel forming assembly includes at least two stacked gas flow channel forming plates, each gas flow channel forming plate is provided with through holes arranged at intervals, and the through holes on each gas flow channel forming plate are divided into multiple groups, each group of through holes includes a plurality of through holes arranged in sequence from one end of the gas flow channel forming plate to the other opposite end, and the corresponding groups of through holes on each gas flow channel forming plate overlap and penetrate end to end to form a gas flow channel extending from one end of the gas flow channel forming assembly to the other end.

[0007] The gas flow path forming assembly of the present application can be formed by stacking two gas flow path forming plates together, or by stacking two or more gas flow path forming plates together. Of course, for the sake of structural simplicity and ease of assembly, preferably, the gas flow path forming assembly includes two stacked gas flow path forming plates, with corresponding sets of through holes on the two gas flow path forming plates overlapping end to end and connecting to form a gas flow path.

[0008] More preferably, the through-holes are waist-shaped holes, with the length ratio of the waist-shaped holes on the gas flow channel forming plate on the side away from the membrane electrode assembly to the waist-shaped holes on the gas flow channel forming plate on the side close to the membrane electrode assembly being 1:1-2.5. Generally, the waist-shaped holes on the side close to the membrane electrode assembly need to be slightly longer. The waist-shaped holes are 0.5-2 mm wide and 1-5 mm long.

[0009] It is further preferred that the length directions of the waist-shaped holes on the two gas flow channel forming plates are respectively biased to both sides. Biased to both sides means that the length direction of the waist-shaped holes is not along the same straight line direction, but that the formed gas flow channel is not only transformed up and down, but also bends left and right in the horizontal direction, so that a longer gas flow channel can be formed on a gas flow channel forming component of the same length. A longer gas flow channel means a longer gas residence time, which improves the gas participation reaction rate in terms of reaction efficiency. At the same time, a relatively unstable gas turbulence will be formed at the gas corner, which is conducive to the gas diffusion in all directions to participate in the reaction, and will also increase the pressure loss of the gas. Among them, in the preferred case, the angle between the length directions of the two waist-shaped holes overlapping end to end on the two gas flow channel forming plates is not less than 120°.

[0010] Preferably, the thickness ratio of the two gas flow channel forming plates is 1:1 / 2 to 2. The thickness of the gas flow channel forming plate will affect the air intake and drainage functions of the membrane electrode assembly. Generally, the thickness of a single gas flow channel forming plate is 0.15 to 0.3 mm for a water-cooled reactor; 1 to 1.5 mm can be used on the air side of an air-cooled reactor. Since the hydrogen and air flow channels of a water-cooled reactor and the hydrogen side flow channels of an air-cooled reactor are driven by relatively high-pressure gas at the inlet, a small cross-sectional area can ensure the efficiency of the intake gas participating in the reaction; the air side of an air-cooled reactor is generally driven by a fan for air intake and exhaust, and it is impossible to drive the gas through a thin flow channel with a large pressure loss. At the same time, cooling must be taken into account, so a larger flow channel cross-sectional area is required. Therefore, a thick gas flow channel forming plate is used, and the width of the through hole forming the flow channel should be appropriately enlarged, taking a width of 2 mm or even 2.5 mm.

[0011] Preferably, the gas flow channel forming plate is made of carbon paper or metal plate.

[0012] The present invention also provides a fuel cell comprising the gas flow channel forming assembly.

[0013] The fuel cell comprises several single cells, each of which comprises a membrane electrode assembly and the gas flow channel forming assemblies respectively arranged on both sides of the membrane electrode assembly. The gas flow channel forming assembly is provided with a gas separator on the side away from the membrane electrode assembly.

[0014] The gas flow channel forming assembly for the fuel cell of the present invention is assembled into a gas flow channel forming assembly by using at least two stacked gas flow channel forming plates. The gas flow channel is formed by a corresponding group of through holes on each gas flow channel forming plate that overlap and penetrate each other end to end. When the gas flows in the gas flow channel, it alternates up and down between the gas flow channel forming plates to achieve a flow component perpendicular to the flow channel surface. Compared with the structure formed by stamping a metal microporous mesh, the preparation difficulty is greatly reduced, the cost is reduced, and no complicated anti-corrosion treatment process is required, and there is no warping on the formed surface. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 Exploded view of the assembly forming the gas flow path.

[0016] Figure 2 Schematic diagram of the gas flow route in the gas flow channel forming component.

[0017] Figure 3 for Figure 2 A partial enlarged view.

[0018] Figure 4 Schematic diagram of the structure of a single cell of the present invention.

[0019] Figure 5 A is a schematic diagram of the structure of the gas flow channel of the present application in Example 3.

[0020] Figure 5 B is a diagram showing the pressure loss detection results of the gas flow channel of the present application in Example 3.

[0021] Figure 6 A is a schematic diagram of the structure of the gas flow channel of the control group in Example 3.

[0022] Figure 6 B is the pressure loss test result diagram of the gas flow channel of the control group in Example 3.

[0023] Figure 7 This is a polarization curve diagram of a single cell with an active area of 50 square centimeters in Example 3 for the present application and the control group. DETAILED DESCRIPTION

[0024] Example 1

[0025] like Figures 1 to 3As shown, a gas flow channel forming assembly for a fuel cell is arranged between a membrane electrode assembly and a gas separator plate and is used to form a gas flow channel. The gas flow channel forming assembly includes at least two stacked gas flow channel forming plates 1, each gas flow channel forming plate 1 is provided with through holes 2 arranged at intervals, and the through holes 2 on each gas flow channel forming plate 1 are divided into multiple groups, each group of through holes 2 includes a plurality of through holes 2 arranged in sequence from one end of the gas flow channel forming plate 1 to the other opposite end, and the corresponding groups of through holes 2 on each gas flow channel forming plate 1 overlap and penetrate end to end to form a gas flow channel extending from one end of the gas flow channel forming assembly to the other end.

[0026] The gas flow path forming assembly of the present application can be formed by stacking two gas flow path forming plates 1 together, or by stacking more than two gas flow path forming plates 1 together. Of course, based on the simplicity of the structure and the ease of assembly, preferably, the gas flow path forming assembly includes two stacked gas flow path forming plates 1, and the corresponding sets of through holes 2 on the two gas flow path forming plates 1 overlap and penetrate end to end to form a gas flow path. One end of one of the gas flow path forming plates 1 has a gas inlet 3, and the other gas flow path forming plate 1 has a gas outlet 4 on the end opposite to the gas inlet 3.

[0027] The through holes 2 are waist-shaped holes, with the length ratio of the waist-shaped holes on the gas flow channel forming plate 1 on the side away from the membrane electrode assembly to the waist-shaped holes on the gas flow channel forming plate 1 on the side close to the membrane electrode assembly being 1:1-2.5. Each waist-shaped hole is 0.5-2 mm wide and 1-5 mm long.

[0028] like Figures 1 to 3 As shown, the length directions of the waist-shaped holes on the two gas flow channel forming plates 1 that constitute the gas flow channel forming assembly are respectively biased to both sides. Biased to both sides means that the length direction of the waist-shaped holes is not along the same straight line direction, but the formed gas flow channel is not only transformed up and down, but also bends left and right in the horizontal direction, so that a longer gas flow channel can be formed on the gas flow channel forming assembly of the same length. A longer gas flow channel means a longer gas residence time, which improves the gas participation reaction rate in terms of reaction efficiency. At the same time, relatively unstable gas turbulence will be formed at the gas corner, which is conducive to the gas diffusion in all directions to participate in the reaction, and will also increase the pressure loss of the gas. Among them, under the better condition, the angle in the length direction of the two waist-shaped holes that overlap head to tail on the two gas flow channel forming plates 1 ( Figure 3 The included angle α) is not less than 120°. Of course, if the included angle α reaches 180°, it is equivalent to the waist-shaped hole not being deflected in the length direction, and the gas flow channel flows in a straight line in the horizontal direction.

[0029] like Figure 2 and 3 As shown, a gas flow line 5 is drawn, from Figure 2The gas enters from the upper middle end and flows out from the lower end. When passing through the overlapping portion 6 of the two through holes 2, the gas enters the through hole 2 on the upper gas flow channel forming plate 1 into the through hole 2 on the lower gas flow channel forming plate 1; then when passing through the adjacent overlapping portion 7, the gas enters the through hole 2 on the lower gas flow channel forming plate 1 into the through hole 2 on the upper gas flow channel forming plate 1, and the gas moves up and down in this way.

[0030] The thickness ratio of the two gas flow channel forming plates 1 is 1:1 / 2 to 2. The thickness of the gas flow channel forming plates 1 affects the air intake and drainage functions of the membrane electrode assembly. Generally, the thickness of a single gas flow channel forming plate 1 is 0.15 to 0.3 mm for water-cooled reactors. For air-cooled reactors, the air side can be 1 to 1.5 mm.

[0031] The gas flow channel forming plate 1 uses carbon paper or metal plate as a substrate. When carbon paper is used as a substrate, the gas diffusion in the gas flow channel can be made more reasonable and the pressure drop can be reduced. Figure 3 As shown, the pressure drop can be adjusted by adjusting the substrate thickness and the angle α. When using a metal plate as the substrate, to address the diffusion area issue, the lengths of L1 and L2 can be appropriately adjusted to increase the diffusion area. When preparing the gas flow channel forming plate 1 of the present application, the corresponding through holes 2 can be directly cut into two substrates, and then the two substrates are overlapped to form the gas flow channel.

[0032] Example 2

[0033] like Figure 4 The figure shows a single cell structure assembled using the gas flow channel forming assembly (formed by two overlapping gas flow channel forming plates 1) of Example 1. Gas flow channel forming assemblies are provided on both sides of the intermediate membrane electrode assembly 9 to form gas flow channels for the two gases, respectively. Gas separator plates 8 are provided on the side of the gas flow channel forming assembly facing away from the membrane electrode assembly 9. The separator plates 8 on both sides enclose the gas flow channel forming assembly and the membrane electrode assembly 9 in an inner layer, and glue lines 10 are used for sealing.

[0034] Several single cells make up a fuel cell.

[0035] Example 3

[0036] like Figure 5 As shown, a gas flow channel extracted separately in Example 1 is extracted from the embodiment. A single flow channel model is extracted from the embodiment for boundary editing. The single layer thickness of the model is 0.2 mm, the width is 0.8 mm, one end is set as the inlet, the condition is an average flow velocity of 10 m / s, the outlet condition is set to 0 Pa, and air is selected as the fluid medium. After meshing, steady-state analysis is performed. The analysis results are shown in the figure. Figure 5 As shown, Figure 5 A is a streamline diagram, and Figure 5B is the pressure distribution contour; Figure 6 The figure shows the gas flow channel of the control group. The model flow channel has a thickness of 0.2 mm, a width of 0.8 mm, and a flow channel stagger angle of 120°. The inlet condition at one end is also set to an average flow velocity of 10 m / s, the outlet condition is 0 Pa, and the fluid medium is air. After meshing, a steady-state analysis is performed. The analysis results are shown in the figure. Figure 6 As shown, Figure 6 A is a streamline diagram. Figure 6 B is the pressure distribution contour line. The pressure loss of the flow field of this application is about 2kPa, while the pressure loss of the control flow channel is about 800Pa.

[0037] In the experiment, a pair of rollers was used to cut PTFE-impregnated hydrophobic carbon paper (available on the market) into the flow channel structure shown in the figure using a circular die cutter as the air side flow field. The control flow channel was carved out of graphite. The hydrogen flow channels were all carved and consistent. They were loaded into a single cell test fixture for fuel cell electrochemical experiments. The membrane electrode used was a membrane electrode with an active area of 50 square centimeters produced from the same batch. The results after averaging multiple tests are shown below. Figure 7 As shown, it can be seen that the electrochemical performance of a single cell using the flow channel of the present application is generally improved, with the average peak power increased from 34.6W watts to 39.3W, and the performance improved by about 13.6%. Due to the complexity of the calculation of the internal pressure loss of the porous flow channel, the pressure loss of the actual control group is about 23kPa, and the pressure loss of a single cell with the flow channel structure of the present application is about 38kPa.

[0038] Compared with the existing single-plane flow channel, its diversion flow in the direction perpendicular to the flow channel surface can effectively increase the diffusion of gas in the membrane electrode diffusion layer and improve the performance of the fuel cell. It reflects the gas pressure drop of the two flow channels. The pressure decreases from left to right. It can be seen that the pressure drop of the new double-layer flow channel is higher than that of the ordinary flow channel.

Claims

1. A gas flow channel forming assembly for a fuel cell, the gas flow channel forming assembly being arranged between a membrane electrode assembly and a gas separator plate and used to form a gas flow channel, characterized in that: The gas flow channel forming assembly includes at least two stacked gas flow channel forming plates, each of which is provided with through holes arranged at intervals, and the through holes on each gas flow channel forming plate are divided into multiple groups, each group of through holes includes multiple through holes arranged in sequence from one end of the gas flow channel forming plate to the other opposite end, and the corresponding groups of through holes on each gas flow channel forming plate overlap and penetrate end to end to form a gas flow channel extending from one end of the gas flow channel forming assembly to the other end.

2. The gas flow channel forming assembly according to claim 1, wherein: The gas flow channel forming assembly includes two stacked gas flow channel forming plates, and corresponding groups of through holes on the two gas flow channel forming plates overlap and penetrate each other end to end to form a gas flow channel.

3. The gas flow channel forming assembly according to claim 2, wherein: The through holes are waist-shaped holes, and the length ratio of the waist-shaped holes on the gas flow channel forming plate on the side away from the membrane electrode assembly to the waist-shaped holes on the gas flow channel forming plate on the side close to the membrane electrode assembly is 1:1-2.

5.

4. The gas flow channel forming assembly according to claim 3, wherein: The width of the waist-shaped hole is 0.5~2mm and the length is 1~5mm.

5. The gas flow channel forming assembly according to claim 3, wherein: The length directions of the waist-shaped holes on the two gas flow channel forming plates are respectively biased to both sides. Biased to both sides means that the length directions of the waist-shaped holes are not along the same straight line direction, but the formed gas flow channel not only changes up and down, but also bends left and right in the horizontal direction.

6. The gas flow channel forming assembly according to claim 5, wherein: The included angle in the length direction of the two waist-shaped holes on the two gas flow channel forming plates that overlap end to end is not less than 120 degrees.

7. The gas flow channel forming assembly according to claim 2, wherein: The thickness ratio of the two gas flow channel forming plates is 1:1 / 2~2.

8. The gas flow channel forming assembly according to claim 1, wherein: The gas flow channel forming plate uses carbon paper or a metal plate.

9. A fuel cell comprising the gas flow channel forming assembly according to any one of claims 1 to 8.

10. The fuel cell according to claim 9, wherein It comprises several single cells, each of which comprises a membrane electrode assembly and the gas flow channel forming assemblies respectively arranged on both sides of the membrane electrode assembly. A gas separator is arranged on the side of the gas flow channel forming assembly away from the membrane electrode assembly.

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