Fuel Cells
The fuel cell design addresses low flow path resistance by using non-continuous gas passages and bypass passages to enhance gas distribution and water drainage, improving efficiency and reducing energy consumption.
Patent Information
- Application Number
- JP2021064013
- Authority / Receiving Office
- JP · JP
- Patent Type
- Patents
- Current Assignee / Owner
- Filing Date
- 2021-04-05
- Publication Date
- 2024-12-17
- Estimated Expiration
- 2041-04-05
AI Technical Summary
Conventional gas diffusion layer electrode base materials in fuel cells have low flow path resistance for reactive gases, necessitating increased flow rates to manage generated water accumulation, which affects both reaction gas supply and drainage efficiency.
A fuel cell design incorporating a membrane electrode assembly with gas diffusion layers and separators, featuring non-continuous gas passages and bypass passages that enhance gas distribution and water drainage by reducing pressure loss and promoting active convection.
The design achieves efficient reaction gas supply and effective water drainage, improving the fuel cell's performance and reducing energy consumption by minimizing pressure loss and enhancing gas diffusion.
Smart Images
Figure 0007600834000001 
Figure 0007600834000002 
Figure 0007600834000003
Abstract
Description
[Technical field]
[0001] The present invention relates to a fuel cell. [Background technology]
[0002] A known fuel cell that generates electricity by reacting a fuel gas with an oxidant gas has a gas diffusion layer electrode substrate that has a plurality of through holes extending from one side to the other side, and at least one of the through hole density and hole diameter varies in the planar direction. In this fuel cell, the gas diffusion layer electrode substrate has a structure in which gas flow paths are provided in both the gas diffusion layer and the plate (see, for example, Patent Document 1). [Prior art documents] [Patent documents]
[0003] [Patent Document 1] Patent No. 5165353 Summary of the Invention [Problem to be solved by the invention]
[0004] Conventional gas diffusion layer electrode substrates have through holes, which reduces the flow resistance of the reactant gas, making it necessary to increase the flow rate of the reactant gas to expedite the drainage of generated water that accumulates in the gas diffusion layer.
[0005] SUMMARY OF THE PRESENT DISCLOSURE An object of the present invention is to provide a fuel cell capable of satisfying both the requirements for supplying reactant gases and discharging generated water. [Means for solving the problem]
[0006] In order to achieve the above object, a fuel cell according to the present invention comprises a membrane electrode assembly in which an anode, a solid polymer membrane, and a cathode are integrated together, a pair of gas diffusion layers that sandwich the membrane electrode assembly, and a pair of separators that sandwich the membrane electrode assembly from the front and back via the pair of gas diffusion layers, each of the separators has a flat surface facing the corresponding gas diffusion layer, each of the gas diffusion layers is porous and has a plurality of gas passages for circulating a gas supplied to the anode or the cathode, and a blocking portion for diffusing the gas, the plurality of gas passages including an upstream passage extending from an opening located on one edge of the gas diffusion layer and terminated inside the gas diffusion layer, and a downstream passage extending from the inside of the gas diffusion layer to an opening located on the other edge of the gas diffusion layer, and each of the separators has a groove-shaped bypass passage provided on the flat surface, connected to either the upstream passage or the downstream passage and extending to the blocking portion. Effect of the Invention
[0007] According to the present invention, it is possible to provide a fuel cell that is capable of satisfying both the supply of reactant gases and the drainage of generated water. [Brief description of the drawings]
[0008] [Figure 1] 1 is a schematic perspective view of a fuel cell according to an embodiment of the present invention; [Diagram 2] 1 is an exploded perspective view of a fuel cell according to an embodiment of the present invention; [Diagram 3] 3 is a partial cross-sectional view taken along the flow direction of the reactant gas flowing through the fuel cell of FIG. 2. [Figure 4] Schematic diagram of the gas diffusion layer of the fuel cell in Figure 2 as viewed from the separator side. [Diagram 5] FIG. 5 is an enlarged view showing a main part of the gas diffusion layer of FIG. 4. [Figure 6] FIG. 6 is a cross-sectional view showing the AA view of FIG. 5 . [Figure 7] FIG. 6 is a cross-sectional view showing the B-B field of view in FIG. 5 . [Figure 8] FIG. 6 is a cross-sectional view showing the CC field of view in FIG. 5 . [Figure 9] FIG. 11 is a schematic diagram of a gas diffusion layer viewed from the separator side of a fuel cell according to a modified example of an embodiment of the present invention. [Figure 10] FIG. 11 is a schematic diagram of a gas diffusion layer viewed from the separator side of a fuel cell according to a modified example of an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0009] An embodiment of a fuel cell separator according to the present invention will be described with reference to Figures 1 to 10. In addition, the same reference numerals are used to designate the same or corresponding components in the various drawings.
[0010] FIG. 1 is a schematic perspective view of a fuel cell according to an embodiment of the present invention.
[0011] 1, a fuel cell 1 according to this embodiment generates power by reacting hydrogen gas as a fuel gas with oxygen (oxygen contained in air) as an oxidant gas. The fuel cell 1 includes a stack 5 having a plurality of stacked fuel cells 2, a pair of end plates 6 that sandwich the stack 5 from the outside in the stacking direction H of the plurality of fuel cells 2, and a plurality of fastening members 8 that are bridged across the pair of end plates 6 to integrate the stack 5 and the pair of end plates 6.
[0012] The fuel gas and the oxidant gas are collectively referred to simply as reactant gases.
[0013] The fuel cell 1 comprises a large number of stacked fuel cells 2. For this reason, the fuel cell 1 is also called a fuel cell stack. The fuel cell 1 has a fuel cell 2 as its smallest unit, and comprises tens to hundreds of stacked fuel cells 2. The number of stacked fuel cells 2 depends on the power generation capacity required of the fuel cell 1.
[0014] The pair of end plates 6 have a rectangular shape that is larger than the fuel cell 2. The pair of end plates 6 are connected by a fastening member 8 that spans between them.
[0015] The fastening members 8 apply a load inward in the stacking direction H to the multiple fuel cells 2 via the pair of end plates 6. This load acts in a direction that brings the pair of end plates 6 closer to each other, compressing the stack 5 in the stacking direction H.
[0016] FIG. 2 is an exploded perspective view of a fuel cell according to an embodiment of the present invention.
[0017] As shown in FIG. 2, the fuel cell 2 of the fuel cell 1 according to this embodiment includes a membrane electrode assembly 11 (MEA: Membrane Electrode Assembly), a pair of gas diffusion layers 12, 13 (GDL: Gas Diffusion Layer) that sandwich the membrane electrode assembly 11, and a pair of separators 15, 16 that sandwich the membrane electrode assembly 11 from the front and back via the pair of gas diffusion layers 12, 13.
[0018] Furthermore, the fuel cell 2 has coolant flow passages (not shown) between the separators 15, 16 adjacent to each other in the stacking direction, through which air or water as a coolant for cooling the fuel cell 1 flows.
[0019] FIG. 3 is a partial cross-sectional view taken along the flow direction of the reactant gas flowing through the fuel cell of FIG.
[0020] FIG. 4 is a schematic diagram of the gas diffusion layer of the fuel cell of FIG. 2 as viewed from the separator side.
[0021] FIG. 5 is an enlarged view showing a main part of the gas diffusion layer of FIG.
[0022] FIG. 6 is a cross-sectional view showing a view AA of FIG.
[0023] FIG. 7 is a cross-sectional view showing the BB field of view of FIG.
[0024] FIG. 8 is a cross-sectional view showing the CC field of FIG.
[0025] 3 is a cross-sectional view of the fuel cell 2 in the vicinity of an air inlet 41, which will be described later. The air outlet 42, the hydrogen gas inlet 31, and the hydrogen gas outlet 32 also have the same structure. Therefore, a cross-sectional view of the fuel cell 2 in the vicinity of the air outlet 42, a cross-sectional view of the fuel cell 2 in the vicinity of the hydrogen gas inlet 31, and a cross-sectional view of the fuel cell 2 in the vicinity of the hydrogen gas outlet 32 are omitted here.
[0026] 4 is a schematic diagram of the gas diffusion layer 13 seen from the separator 16 side facing the cathode 19 as an air electrode, and Fig. 5 is an enlarged view of a main part of the gas diffusion layer 13 seen from the separator 16 side facing the cathode 19. Figs. 6 to 8 are partial cross-sectional views of the separator 16 and the gas diffusion layer 13 facing the cathode 19. The gas diffusion layer 12 seen from the separator 15 side facing the anode 18 as a fuel electrode may also be configured similarly to Figs. 4 to 8.
[0027] 2 and 3, the membrane electrode assembly 11 of the fuel cell 1 includes a solid polymer membrane 17 as an electrolyte, an anode 18, and a cathode 19. The membrane electrode assembly 11 is an integrated solid polymer membrane 17, anode 18, and cathode 19. The pair of electrodes 18, 19 sandwich the solid polymer membrane 17 from the front and back.
[0028] The pair of gas diffusion layers 12, 13 are porous membranes. The pair of gas diffusion layers 12, 13 supply hydrogen gas and air to the pair of electrodes 18, 19, collect electrons generated by chemical reactions, keep the solid polymer membrane 17 moist, and drain generated water.
[0029] A pair of subgaskets 21 are disposed around the pair of gas diffusion layers 12, 13. The pair of subgaskets 21 are thin films having a smaller gas permeability coefficient than the gas diffusion layers 12, 13, for example, made of polyethylene naphthalate (PEN) resin.
[0030] Each fuel cell 2 has a hydrogen gas flow path 22 (gas passage) that supplies hydrogen gas to the anode 18, and a gas passage 23 (gas passage) that supplies air to the cathode 19. The hydrogen gas flow path 22 is defined between the gas diffusion layer 12 facing the anode 18 and the separator 15. The gas passage 23 is defined between the gas diffusion layer 13 facing the cathode 19 and the separator 16.
[0031] 4 to 7, the gas diffusion layer 13 has a plurality of gas passages 23 for circulating gas supplied to the cathode 19 (see FIGS. 2 and 3). The plurality of gas passages 23 are open to a surface 13a of the gas diffusion layer 13 facing the separator 16, and have a groove shape closed by the separator 16.
[0032] The gas passages 23 include a plurality of upstream passages 25 extending from an opening 23i disposed on one edge of the gas diffusion layer 13 and terminated inside the gas diffusion layer 13, and a plurality of downstream passages 26 extending from the inside of the gas diffusion layer 13 and reaching an opening 23o disposed on the other edge of the gas diffusion layer 13. In other words, the upstream passages 25 and the downstream passages 26 are disconnected passages that are not continuously connected from one edge to the other edge of the gas diffusion layer 13, and do not penetrate between one edge and the other edge of the gas diffusion layer 13. Note that the gas flow direction X is indicated by a solid arrow in Figs. 4 and 5.
[0033] The upstream passages 25 and the downstream passages 26 extend in parallel without being connected to each other. The upstream passages 25 and the downstream passages 26 may be straight passages as shown in FIG. 4, or may be meandering passages.
[0034] Furthermore, the multiple upstream passages 25 and the multiple downstream passages 26 may be arranged in a staggered manner as shown in FIG. 4, or may be arranged in a straight line.
[0035] The plurality of gas passages 23 also includes closed intermediate passages 71 at the edge of the gas diffusion layer 13 that extend away from the upstream passages 25 and the downstream passages 26 .
[0036] The intermediate passages 71 , like the upstream passages 25 and the downstream passages 26 , have a groove shape that opens to the surface 13 a of the gas diffusion layer 13 facing the separator 16 and is closed by the separator 16 .
[0037] The intermediate passage 71 does not reach any edge of the gas diffusion layer 13, and is not directly connected to the upstream passage 25 or the downstream passage 26 within the gas diffusion layer 13. In the gas diffusion layer 13, the portions between the upstream passage 25 and the intermediate passage 71, and between the intermediate passage 71 and the downstream passage 26 function as blocked portions 13A where these gas passages 23 are not formed.
[0038] The length dimension LX of the blocking portion 13A in the flow direction X of the gas indicated by the solid arrow in FIG. 4 is larger than the width dimension W of the blocking portion 13A in the direction Y perpendicular to the flow direction X. Also, the interval between the upstream passage 25, the intermediate passage 71, and the intermediate passage 71 in the direction Y perpendicular to the flow direction X, that is, the alignment interval, is smaller than the length dimension LX of the blocking portion 13A. In other words, the length dimension LX of the blocking portion 13A is larger than the width dimension W of the blocking portion 13A and is larger than the alignment interval between the upstream passage 25, the intermediate passage 71, and the intermediate passage 71. Therefore, when the gas flowing in the flow direction X flows into the blocking portion 13A at the downstream end of the upstream passage 25 and the downstream end of the intermediate passage 71, it is prevented from moving in the flow direction X and diffuses widely in the direction Y perpendicular to the flow direction X. This diffusion of the gas allows moisture accumulated in the gas passage 23 and the blocking portion 13A to be drained.
[0039] In other words, by providing the blocked portion 13A, the gas diffusion layer 13 generates an active flow in a direction Y intersecting the gas flow direction X shown by the solid arrow in FIG. 4, and pushes away the water accumulated in the blocked portion 13A into the downstream passage 26.
[0040] Therefore, if the gap in the gas flow direction X between the upstream passage 25 and the intermediate passage 71 or the intermediate passage 71 and the downstream passage 26, i.e., the size of the blocking portion 13A in the flow direction X, is reduced, the pressure loss is reduced and the water flow in the flow direction X is also reduced. Therefore, it is preferable to leave a gap between the upstream passage 25 and the intermediate passage 71 or the intermediate passage 71 and the downstream passage 26 that are adjacent to each other in the flow direction X among the multiple gas passages 23. In other words, it is preferable to ensure a wide dimension of the blocking portion 13A in the flow direction X.
[0041] The intermediate passage 71 extends parallel to the multiple upstream passages 25 and the multiple downstream passages 26. The intermediate passage 71 may be a straight passage as shown in Fig. 4, or may be a serpentine passage.
[0042] Furthermore, the intermediate passage 71 does not have to be on an extension line of the upstream passage 25 and the downstream passage 26 as shown in FIG. 4 , but may be parallel to the upstream passage 25 and the downstream passage 26, or may be disposed on an extension line of either the upstream passage 25 or the downstream passage 26, or may be aligned in a straight line on an extension line of the upstream passage 25 and the downstream passage 26.
[0043] Furthermore, as shown in FIG. 4, the intermediate passage 71 may or may not overlap both the upstream passage 25 and the downstream passage 26 in the direction Y intersecting the gas flow. Also, the intermediate passage 71 may or may not overlap either the upstream passage 25 or the downstream passage 26 in the direction Y intersecting the gas flow. Furthermore, adjacent intermediate passages 71 may or may not overlap in the direction Y intersecting the gas flow. Also, the intermediate passages 71, the upstream passages 25, and the downstream passages 26 that overlap in the direction Y intersecting the gas flow, and the intermediate passages 71, the upstream passages 25, and the downstream passages 26 that do not overlap may be mixed. The direction Y intersecting the gas flow is also the alignment direction of the intermediate passages 71, the upstream passages 25, and the downstream passages 26.
[0044] The upstream passages 25, downstream passages 26, and intermediate passages 71 arranged in this manner have a portion separated by the gas diffusion layer 13 between the downstream end of each upstream passage 25 and the upstream end of the intermediate passage 71, and between the downstream end of each intermediate passage 71 and the upstream end of the downstream passage 26. This portion has a large number of pores (not shown) in the gas diffusion layer 13. In other words, the upstream passage 25, the downstream passages 26, and the intermediate passages 71 are connected via a large number of pores in the gas diffusion layer 13. This portion has an extremely high pressure loss compared to the upstream passages 25 and the downstream passages 26. Therefore, this portion is called a high pressure loss portion 27 for convenience.
[0045] That is, the gas supplied to the cathode 19 flows from the upstream passages 25 into the high pressure loss section 27, passes through the high pressure loss section 27 into the intermediate passages 71, and then passes through the high pressure loss section 27 to the downstream passages 26. In the high pressure loss section 27, the flow velocity of the gas flowing in from the upstream passages 25 and the flow velocity of the gas flowing in from the intermediate passages 71 increase. The gas with the increased flow velocity easily drains the generated water accumulated in the pores of the high pressure loss section 27 into the intermediate passages 71 and downstream passages 26.
[0046] Adjacent upstream passages 25 are also connected via a large number of pores in the gas diffusion layer 13. Therefore, the gas supplied to the cathode 19 easily drains the generated water accumulated in the pores between adjacent upstream passages 25. The same applies to the intermediate passages 71 and the downstream passages 26.
[0047] As shown in FIG. 3, the gas passage 23 is connected to an air inlet 41 and an air outlet 42 (see FIG. 2) provided in the separator 16.
[0048] An air inlet side manifold 45 is provided between the air inlet 41 and the gas passage 23. The air inlet side manifold 45 guides the air flowing in from the air inlet 41 to the gas passage 23. The air inlet side manifold 45 branches the air flowing in from the air inlet 41 to each of the upstream side passages 25. An air outlet side manifold (not shown) is provided between the air outlet 42 and the gas passage 23. The air outlet side manifold guides the air flowing out from the gas passage 23 to the air outlet 42. The air outlet side manifold collects the air flowing out from the gas passage 23 from each of the downstream side passages 26 to the air outlet 42.
[0049] The gas diffusion layer 12 has a plurality of hydrogen gas flow paths 22 through which gas is supplied to the anode 18. By configuring the hydrogen gas flow paths 22 as in the gas passages 23 of Fig. 4, the drainage of water generated by back diffusion from the cathode 19 is improved, and the effective reaction area of the anode 18 can be expected to be improved.
[0050] The hydrogen gas flow path 22 is connected to a hydrogen gas inlet 31 and a hydrogen gas outlet 32 provided in the separator 15 .
[0051] A hydrogen gas inlet side manifold 35 is provided between the hydrogen gas inlet 31 and the hydrogen gas flow path 22. The hydrogen gas inlet side manifold 35 guides hydrogen gas flowing from the hydrogen gas inlet 31 to the hydrogen gas flow path 22. The hydrogen gas inlet side manifold 35 branches the hydrogen gas flowing from the hydrogen gas inlet 31 to each upstream passage. A hydrogen gas outlet side manifold 36 is provided between the hydrogen gas outlet 32 and the hydrogen gas flow path 22. The hydrogen gas outlet side manifold 36 guides hydrogen gas flowing out from the hydrogen gas flow path 22 to the hydrogen gas outlet 32. The hydrogen gas outlet side manifold 36 collects hydrogen gas flowing out from the hydrogen gas flow path 22 from each downstream passage to the hydrogen gas outlet 32.
[0052] The separators 15, 16 are made of, for example, carbon fiber reinforced plastic, conductive resin, or metal. Each separator 15, 16 has a flat surface 15a, 16a facing the corresponding gas diffusion layer 12, 13. These flat surfaces 15a, 16a close the groove-shaped gas passages of the corresponding gas diffusion layer 12, 13.
[0053] The separator 15 facing the gas diffusion layer 12 facing the anode electrode 18 has an air inlet 51 for supplying air to the separator 16 facing the gas diffusion layer 13 facing the cathode electrode 19, and an air outlet 52 for discharging air from the separator 15.
[0054] A hydrogen gas side seal 59 protruding toward the membrane electrode assembly 11 is provided on the surface 15 a of the separator 15 .
[0055] The separator 16 facing the gas diffusion layer 13 facing the cathode electrode 19 has a hydrogen gas inlet 61 for supplying hydrogen gas to the separator 15 facing the gas diffusion layer 12 facing the anode electrode 18, and a hydrogen gas outlet 62 for discharging hydrogen gas from the separator 15.
[0056] An air-side seal 69 that protrudes toward the membrane electrode assembly 11 is provided on the surface 16 a of the separator 16 .
[0057] As shown in Figs. 5 to 7, the separator 16 of the fuel cell 1 according to this embodiment has a plurality of bypass passages 16b that are provided at a portion facing the blocked portion 13A of the gas diffusion layer 13, open to a surface 16a facing the gas diffusion layer 13, and allow gas to flow to the cathode 19 (see Figs. 2 and 3). The plurality of bypass passages 16b open to the surface 13a of the gas diffusion layer 13 facing the separator 16. The plurality of bypass passages 16b have a groove shape that is closed by the blocked portion 13A of the gas diffusion layer 13 at a portion that does not overlap with the upstream passage 25 or the intermediate passage 71. The bypass passages 16b include at least one of a first bypass passage 16ba that connects the upstream passage 25 and the intermediate passage 71, and a second bypass passage 16bb that connects the intermediate passage 71 and the downstream passage 26. 8, the bypass passage 16b connects the upstream passage 25 and the intermediate passage 71 by bypassing the blocked portion 13A. Note that, here, the portion centered on the blocked portion 13A between the upstream passage 25 and the intermediate passage 71 is enlarged and described as the main portion of the gas diffusion layer 13, but the portion centered on the blocked portion 13A between the intermediate passage 71 and the downstream passage 26 also has a similar structure. Also, the bypass passage 16b is formed by a method such as a pressing method or an etching method.
[0058] The bypass passage 16b preferably connects the gas passages 23 adjacent to each other in the gas flow direction X. Specifically, the first bypass passage 16ba connects the upstream passage 25 and the intermediate passage 71 adjacent to each other in the gas flow direction X, and the second bypass passage 16bb connects the intermediate passage 71 and the downstream passage 26 adjacent to each other in the gas flow direction X. Since the pressure loss is small in the multiple gas passages 23 (including the upstream passage 25, the downstream passage 26, and the intermediate passage 71), the pressure loss in the blocking portion 13A can be reduced by providing the bypass passage 16b to connect them. In addition, the upstream passage 25 and the intermediate passage 71 adjacent to each other in the gas flow direction X are connected by the bypass passage 16b so as to bypass the blocking portion 13A, so that the multiple gas passages 23 (including the upstream passage 25, the downstream passage 26, and the intermediate passage 71) are shortened, and the catalyst gas flows to the gas diffusion layer 13 side, thereby improving the diffusibility of the catalyst gas.
[0059] The gas passage 23 and the bypass passage 16b do not connect the opening 23i arranged on one edge of the gas diffusion layer 13 to the opening 23o arranged on the other edge of the gas diffusion layer 13 in a continuous manner without passing through the blocking portion 13A of the gas diffusion layer 13. That is, the gas flowing in from the opening 23i arranged on one edge passes through the blocking portion 13A of the gas diffusion layer 13 at least once before reaching the opening 23o arranged on the other edge. Also, the overlapping of the upstream passage 25, the downstream passage 26, and the intermediate passage 71 with the bypass passage 16b may be large or small within a range in which the gas flowing in from the opening 23i arranged on one edge passes through the blocking portion 13A of the gas diffusion layer 13 at least once before reaching the opening 23o arranged on the other edge. Also, the bypass passage 16b may be interrupted at a location facing the blocking portion 13A. For example, the first bypass passage 16 ba may extend from the upstream passage 25 to the intermediate passage 71 and extend beyond the intermediate passage 71 to reach the vicinity of the other edge of the gas diffusion layer 13 .
[0060] 6, the cross-sectional area L2 of the bypass passage 16b is preferably smaller than the cross-sectional area L1 of the multiple gas passages 23 (including the upstream passage 25, the downstream passage 26, and the intermediate passage 71). The cross-sectional area L2 of the bypass passage 16b is narrow, and the catalyst gas is diffused in the blocked portion 13A to improve drainage, while reducing pressure loss.
[0061] 7, the bypass passage 16b is preferably disposed in the center of the blocked portion 13A in the direction Y intersecting the gas flow. Generated water is likely to accumulate in the contact area between the separator 16 and the gas diffusion layer 13, but the flow rate is fast and the drainage tends to be good in the area where the gas diffusion layer 13 and the separator 16 are not in contact. Therefore, by providing the bypass passage 16b in the center of the blocked portion 13A in the direction Y intersecting the gas flow, which tends to have the poorest drainage, the drainage can be improved.
[0062] Here, a fuel cell 2 according to a modification of the present embodiment will be described.
[0063] FIG. 9 is a schematic diagram of a gas diffusion layer viewed from the separator side of a fuel cell according to a modified example of an embodiment of the present invention.
[0064] FIG. 10 is a schematic diagram of a gas diffusion layer viewed from the separator side of a fuel cell according to a modified example of an embodiment of the present invention.
[0065] It is preferable that the bypass passage 16b has, at both ends in the gas flow direction X, an inclined portion 16c inclined in the thickness direction of the separator 16. This allows the gas to flow smoothly into the bypass passage 16b.
[0066] In addition, the bypass passage 16b is preferably provided with an agitation portion 16d composed of recesses, protrusions, etc. for agitating the flow of gas, which generates turbulence in the gas flow in the bypass passage 16b and agitates the air, thereby enabling the reactive gas to be diffused more effectively in the gas diffusion layer 13.
[0067] As described above, the fuel cell 1 according to this embodiment includes a plurality of gas passages 23, including an upstream passage 25 extending from an opening 23i disposed on one edge of the gas diffusion layer 13 and interrupted inside the gas diffusion layer 13, and a downstream passage 26 extending from the inside of the gas diffusion layer 13 to an opening 23o disposed on the other edge of the gas diffusion layer 13. The gas diffusion layer 13 is porous, and there is no passage that is continuously connected from the opening 23i as the inlet of the gas passage 23 to the opening 23o as the outlet of the gas passage 23, and air as a reactant gas can flow through interrupted passages such as the upstream passage 25 and the downstream passage 26. Therefore, the gas passage 23 includes a high pressure loss portion 27. In this high pressure loss portion 27, the generated water accumulated in the pores is easily drained to the downstream passage 26 by the air as a reactant gas flowing in from the upstream passage 25. Moreover, the separator 16 has a plurality of bypass passages 16b that open to the surface 16a facing the gas diffusion layer 13 at a portion facing the blocked portion 13A of the gas diffusion layer 13 and that allow gas to flow to the cathode 19 (see Figs. 2 and 3). The plurality of bypass passages 16b open to the surface 13a of the gas diffusion layer 13 facing the separator 16, and have a groove shape that is closed by the blocked portion 13A of the gas diffusion layer 13 at a portion that does not overlap with the upstream passage 25 or the intermediate passage 71. The bypass passage 16b connects at least one of the upstream passage 25 and the intermediate passage 71, or the intermediate passage 71 and the downstream passage 26, by bypassing the blocked portion 13A. Therefore, the fuel cell 1 can achieve both the supply of reactant gas and the drainage of generated water.
[0068] If the separator 16 does not have the bypass passage 16b, the upstream passage 25 and the downstream passage 26 of the gas diffusion layer 13 are separated at the blocked portion 13A. However, by providing the bypass passage 16b in the separator 16 facing the blocked portion 13A, the pressure loss can be reduced compared to when the separator 16 does not have the bypass passage 16b. Although not shown, the fuel cell 1 drives a compressor to supply reactant gas. Therefore, by providing the bypass passage 16b in the separator 16 facing the blocked portion 13A, the fuel cell 1 can reduce the supply pressure of the reactant gas by the amount of the reduced pressure loss, thereby enabling the compressor to be made more energy-efficient and more compact.
[0069] In addition, the upstream passage 25 and the downstream passage 26 of the fuel cell 1 according to this embodiment overlap in a direction intersecting the flow of the reactant gas. In this overlapping portion, the linear distance between the downstream end of the upstream passage 25 and the upstream end of the downstream passage 26 is the shortest, and the influence of the pressure loss in the high pressure loss section 27 is small. That is, in the overlapping portion, the reactant gas easily flows from the upstream passage 25 to the downstream passage 26. Therefore, in the overlapping portion, the deceleration caused by the reactant gas diffusing too much into the gas diffusion layer 13 is suppressed, and the generated water accumulated in the high pressure loss section 27 can be drained more efficiently. Therefore, the fuel cell 1 can achieve both the supply of the reactant gas and the drainage of the generated water.
[0070] The gas diffusion layer 13 is expected to generate active convection in the direction Y intersecting the gas flow by providing the blocking portion 13A, and to have the effect of pushing the generated water that accumulates in the blocking portion 13A to the downstream passage 26. Therefore, if the gap in the flow direction X between the upstream passage 25 and the intermediate passage 71 or between the intermediate passage 71 and the downstream passage 26, that is, the size of the flow direction X of the blocking portion 13A, is reduced, the pressure loss is reduced and the flow of water in the flow direction X is also reduced. Therefore, it is preferable to leave a gap between the upstream passage 25 and the intermediate passage 71 or between the intermediate passage 71 and the downstream passage 26 that are adjacent to each other in the flow direction X among the multiple gas passages 23. In other words, it is preferable to ensure a large dimension in the flow direction X of the blocking portion 13A.
[0071] Moreover, the fuel cell 1 according to this embodiment has a non-open intermediate passage 71 at the edge of the gas diffusion layer 13, which extends away from the multiple gas passages 23, i.e., the upstream passage 25 and the downstream passage 26. The intermediate passage 71 is not connected to either the upstream passage 25 or the downstream passage 26, and is separated from them. The bypass passage 16b connects at least one of the upstream passage 25 and the intermediate passage 71, or the intermediate passage 71 and the downstream passage 26. Therefore, compared to the case where only the upstream passage 25 and the downstream passage 26 are provided, the intermediate passage 71 allows the reactant gas to be diffused over a wider range of the gas diffusion layer 13, while suppressing a decrease in the flow rate of the reactant gas. Therefore, the fuel cell 1 can achieve both the supply of the reactant gas and the drainage of the generated water.
[0072] In addition, by configuring the hydrogen gas flow path 22 in the same manner as the gas passage 23 in Figures 3 to 10, the drainage of water generated by back diffusion from the cathode electrode 19 can be improved, and the effective reaction area of the anode electrode 18 can be expected to be improved.
[0073] Therefore, the fuel cell 1 according to the present invention can easily achieve both the supply of reactant gases and the drainage of generated water. [Explanation of symbols]
[0074] 1...fuel cell, 2...fuel cell, 5...laminated body, 6...end plate, 8...fastening member, 11...membrane electrode assembly, 12, 13...gas diffusion layer, 13A...blocking portion, 13a...surface of gas diffusion layer, 15, 16...separator, 15a, 16a...surface of separator, 16b...bypass passage, 16ba...first bypass passage, 16bb...second bypass passage, 16c...inclined portion, 16d...agitating portion, 17...solid polymer membrane, 18...anode electrode, 19...cathode electrode, 21...subgasket, 22...hydrogen Gas flow path, 23...gas passage, 23i...opening, 23o...opening, 25...upstream passage, 26...downstream passage, 27...high pressure loss section, 31...hydrogen gas inlet, 32...hydrogen gas outlet, 35...hydrogen gas inlet side manifold, 36...hydrogen gas outlet side manifold, 41...air inlet, 42...air outlet, 45...air inlet side manifold, 51...air inlet, 52...air outlet, 59...hydrogen gas side seal, 61...hydrogen gas inlet, 62...hydrogen gas outlet, 69...air side seal, 71...intermediate passage.
Claims
1. a membrane electrode assembly in which an anode electrode, a solid polymer membrane, and a cathode electrode are integrated; A pair of gas diffusion layers sandwiching the membrane electrode assembly; a pair of separators sandwiching the membrane electrode assembly from the front and back via the pair of gas diffusion layers; Each of the separators has a flat surface facing the corresponding gas diffusion layer, Each of the gas diffusion layers is porous and has a plurality of gas passages through which a gas supplied to the anode or the cathode flows, and a blocking portion through which the gas diffuses, the plurality of gas passages include an upstream passage extending from an opening disposed on one edge of the gas diffusion layer and terminated inside the gas diffusion layer, and a downstream passage extending from the inside of the gas diffusion layer and reaching an opening disposed on the other edge of the gas diffusion layer; a bypass passage in the form of a groove, the bypass passage being connected to either the upstream passage or the downstream passage and extending to the blocking portion;
2. the plurality of gas passages includes an intermediate passage that is not open to an edge of the gas diffusion layer and extends away from the upstream passage and the downstream passage; 2. The fuel cell according to claim 1, wherein the bypass passage includes at least one of a first bypass passage connecting the upstream passage and the intermediate passage and a second bypass passage connecting the intermediate passage and the downstream passage.
3. the first bypass passage connects the upstream passage and the intermediate passage adjacent to each other in a flow direction of the gas, The fuel cell according to claim 2 , wherein the second bypass passage connects the intermediate passage and the downstream passage adjacent to each other in a flow direction of the gas.
4. 4. The fuel cell according to claim 1, wherein a cross-sectional area of the bypass passage is smaller than cross-sectional areas of the plurality of gas passages.
5. 5. The fuel cell according to claim 1, wherein the bypass passage is disposed at a center of the blocking portion in a direction intersecting a flow direction of the gas.
6. 6. The fuel cell according to claim 1, wherein the bypass passage is provided at both ends in a flow direction of the gas and has an inclined portion inclined in a thickness direction of the separator.
7. The fuel cell according to claim 1 , wherein the bypass passage includes an agitating portion that agitates the flow of the gas.
Citation Information
Patent Citations
Denkikiki
JP1976065353A