JP6747214B2 - Fuel cell, fuel cell gas flow channel structure, and fuel cell separator - Google Patents

Description

The present invention relates to a fuel cell used as a power source for stationary (household, industrial), transportation or portable equipment, a gas channel structure of a fuel cell, and a fuel cell separator.

As a gas flow channel structure for a fuel cell, an opposed comb flow channel (IDFF) has been proposed. In the facing comb-shaped flow channel, a gas supply flow channel whose downstream end is blocked and a gas discharge flow channel whose upstream end is blocked are alternately arranged on the gas diffusion layer of the membrane electrode assembly at intervals. It is set up. Patent Document 1 describes a related technique.

The gas supplied to the gas supply flow path of the facing comb-shaped flow path digs into the gas diffusion layer from the gas supply flow path, passes through the inside in the surface direction, and then flows into the adjacent gas discharge flow path (hereinafter , The flow of gas passing through the gas diffusion layer is referred to as "cross flow". In the opposed comb-shaped flow path, forced convection is generated in a region closer to the electrode catalyst layer in the gas diffusion layer, so that the concentration gradient of the gas in the vicinity of the electrode catalyst layer can be increased and the gas diffusibility can be improved. Therefore, the opposed comb-shaped channel can obtain relatively good power generation efficiency as compared with the parallel channel and the serpentine channel.

JP2012-64483A

However, since the gas supplied to the gas supply channel is supplied to the electrochemical reaction while flowing down the gas supply channel (before diving into the gas diffusion layer as a cross flow), the gas supply channel The concentration of the cross-flow gas flowing out from the lower side region becomes lower. For this reason, the gas diffusivity is relatively low in the region on the downstream side of the opposed comb-shaped channel, which hinders the improvement of the power generation efficiency of the fuel cell.

An object of the present invention is to suppress a decrease in gas diffusibility in the downstream region of the opposed comb-shaped flow path and improve the power generation efficiency of the fuel cell.

One aspect of the present invention is that the flow path resistance from the upstream end to the downstream end of each gas discharge flow path is more than the flow path resistance from the upstream end to the downstream end of each gas supply flow path adjacent to the gas discharge flow path. the size rather, the flow path length from the upstream end of the gas discharge channel to the downstream end is longer fuel cell than the flow path length from the upstream end of the gas supply channel adjacent to the gas discharge channel to the downstream end It is a gas flow path structure.

According to the gas flow channel structure described above, it is possible to suppress a decrease in gas diffusibility in the downstream region of the opposed comb-shaped flow channel and improve the power generation efficiency of the fuel cell.

FIG. 1 is a perspective view of a fuel cell stack according to an embodiment of the present invention. FIG. 2 is a side view of the fuel cell stack of FIG. FIG. 3 is a cross-sectional view showing the configuration of the fuel cell according to the first embodiment. FIG. 4 is a front view of a separator including the gas flow channel structure according to the first embodiment. FIG. 5 shows that the relationship between the flow resistances of the gas supply flow path and the gas discharge flow path adjacent to each other in the opposed comb-shaped flow path is such that the gas pressure distribution in both flow paths, the differential pressure distribution between the flow paths, and the cross flow It is a graph which shows typically the influence which it has on flow distribution. FIG. 6 is a transverse cross-sectional view of the gas supply passage and the gas discharge passage according to the first modification. FIG. 7 is a transverse cross-sectional view of a gas supply passage and a gas discharge passage according to the second modification. FIG. 8 is a vertical cross-sectional view of the gas exhaust flow path according to the third modification. FIG. 9: is a front view of the separator provided with the gas flow path structure which concerns on a 4th modification. FIG. 10 is a front view of a separator including the gas flow channel structure according to the second embodiment. FIG. 11 is a front view of a separator including the gas flow channel structure according to the third embodiment.

Hereinafter, some embodiments of the present invention will be described with reference to the drawings.

<First Embodiment>
As shown in FIGS. 1 and 2, the fuel cell stack S according to the first embodiment has a plurality of fuel cells 1 stacked in the stacking direction X, a pair of current collecting plates 2, and a pair of insulating plates 3. And a pair of end plates 4 and four tension rods 5.

The pair of current collecting plates 2 are arranged outside the stacking direction X of the plurality of fuel cells 1, respectively. Each current collecting plate 2 is formed of a gas impermeable conductive material such as dense carbon, and an output terminal 2a is formed on the outer peripheral edge thereof. The electric power generated by the plurality of fuel cells 1 is taken out from the output terminal 2a.

An insulating plate 3 is arranged outside each current collecting plate 2 in the stacking direction X. The insulating plate 3 is made of an insulating material such as rubber. The end plates 4 are arranged outside the insulating plates 3 in the stacking direction X. The end plate 4 is made of a highly rigid material such as steel.

A sub-end plate 6 and an elastic member 7 such as a disc spring are arranged in this order from the inner side in the stacking direction X between the end plate 4 and the insulating plate 3 on one side in the stacking direction X (right side in the drawing). ing.

A fuel gas supply port 4a, an oxidant gas supply port 4b, and a refrigerant supply port 4c are provided at one end of the longitudinal direction Y of the end plate 4 on the other side (left side in the drawing) in the stacking direction X. There is. On the other hand, a fuel gas exhaust port 4d, an oxidant gas exhaust port 4e, and a refrigerant exhaust port 4f are provided at the other end of the longitudinal direction Y. Fuel gas such as hydrogen-containing gas is supplied to the fuel gas supply port 4a. An oxidant gas such as air is supplied to the oxidant gas supply port 4b. Cooling water, for example, is supplied to the coolant supply port 4c.

At the four corners of the end plate 4, four through holes that penetrate the plurality of fuel cells 1 in the stacking direction X are provided, and the tension rods 5 are inserted into the through holes, respectively. A nut 5b is screwed and fastened to the threaded portion 5a of the tension rod 5, whereby a pressure in the stacking direction X is applied to the fuel cells 1 arranged between the end plates 4. ing. The tension rod 5 and the nut 5b are made of a highly rigid material such as steel. The surface of the tension rod 5 is subjected to an insulation treatment in order to prevent a short circuit between elements having different potentials such as between the fuel cells 1 and between the fuel cells 1 and the current collector plate 2. ..

As shown in FIG. 3, each fuel cell 1 (fuel cell) includes a membrane electrode assembly 10, and an anode-side separator 11 and a cathode-side separator 12 that sandwich the membrane-electrode assembly 10 from both sides.

The membrane electrode assembly 10 includes an electrolyte membrane 13, an anode-side electrode catalyst layer 14 and a cathode-side electrode catalyst layer 14 formed on both surfaces of the electrolyte membrane 13, and an anode side provided adjacent to each electrode catalyst layer 14. The gas diffusion layer 15 and the gas diffusion layer 15 on the cathode side.

The electrolyte membrane 13 is an ion exchange membrane made of, for example, a fluorine resin, and exhibits good proton conductivity in a wet state.

The electrode catalyst layer 14 is made of, for example, platinum (Pt) or an alloy of Pt and another metal (for example, a Pt alloy in which cobalt or nickel is mixed) supported on carbon carrier particles, and electrolyte particles (ionomer). ) And a water-repellent agent. The electrode catalyst layer 14 is formed on the electrolyte membrane 13 by hot pressing or direct spraying.

The gas diffusion layer 15 is a conductive member having gas permeability, which is made of, for example, a carbon porous body such as carbon cloth or carbon paper, or a metal porous body such as a metal mesh or foam metal. The gas diffusion layer 15 has a substantially uniform ventilation resistance (air permeability) over substantially the entire area of the surface in contact with the separators 11 and 12.

The separators 11 and 12 are formed of a gas impermeable conductive member such as dense carbon or a press-molded metal plate.

As shown in FIG. 3, a groove-shaped fuel gas flow channel 20 that defines a fuel gas flow channel together with the gas diffusion layer 15 is formed on the surface of the separator 11 in contact with the gas diffusion layer 15. A groove-shaped coolant channel 30 serving as a coolant channel is formed on the surface opposite to the surface on which the fuel gas channel 20 is formed. In addition, a groove-shaped oxidant gas flow path 40 that defines a flow path for the oxidant gas together with the gas diffusion layer 15 is formed on the surface of the separator 12 that contacts the gas diffusion layer 15. The coolant channel 30 may be formed on the surface of the separator 12 opposite to the surface on which the oxidant gas channel 40 is formed, or on both surfaces of the separators 11 and 12 that directly face each other. Good.

As shown in FIG. 4, at one end (left side in the drawing) of the separator 12 in the longitudinal direction Y, a gas supply port A1 for fuel gas, a gas supply port B1 for oxidant gas, and a coolant supply port C1 are provided. Are arranged side by side in this order in the width direction Z of the separator 12. Further, at the other end (right side in the drawing) of the longitudinal direction Y of the separator 12, a gas exhaust port A2 for fuel gas, a gas exhaust port B2 for oxidant gas, and a refrigerant exhaust port C2 are provided. They are arranged side by side in this order in the width direction Z. Although not shown, the gas supply ports A1 and B1, the coolant supply port C1, the gas discharge ports A2 and B2, and the coolant discharge port C2 of the separator 11 are line-symmetrical to those of the separator 12. It is provided in an arrangement.

The gas supply port A1 and the gas discharge port A2 of the fuel gas respectively configure a fuel gas supply manifold and a fuel gas discharge manifold extending in the stacking direction X in the fuel cell stack S. The gas supply port B1 and the gas discharge port B2 for the oxidant gas respectively configure an oxidant gas supply manifold and an oxidant gas discharge manifold extending in the stacking direction X in the fuel cell stack S. The coolant supply port C1 and the coolant discharge port C2 respectively form a coolant supply manifold and a coolant discharge manifold extending in the stacking direction X in the fuel cell stack S. Further, the fuel gas supply manifold and the fuel gas discharge manifold communicate with the fuel gas supply port 4a and the fuel gas discharge port 4d, respectively. The oxidant gas supply manifold and the oxidant gas discharge manifold communicate with the oxidant gas supply port 4b and the oxidant gas discharge port 4e, respectively. The coolant supply manifold and the coolant discharge manifold communicate with the coolant supply port 4c and the coolant discharge port 4f, respectively.

The fuel gas supplied to the fuel gas supply port 4a passes through the fuel gas supply manifold, branches from the gas supply port A1 of each separator 12 into each fuel gas passage 20, and is supplied to the electrochemical reaction. After that, the fuel gas exits the gas exhaust port A2, gathers in the fuel gas exhaust manifold, and is exhausted from the fuel cell stack S via the fuel gas exhaust port 4d.

Further, the oxidant gas supplied to the oxidant gas supply port 4b passes through the oxidant gas supply manifold, branches from the gas supply port B1 of each separator 11 into each oxidant gas flow channel 40, and flows into the electrochemical gas. Subject to the reaction. Then, the oxidant gas exits the gas exhaust port B2, gathers in the oxidant gas exhaust manifold, and is exhausted from the fuel cell stack S via the oxidant gas exhaust port 4e.

Further, the refrigerant supplied to the refrigerant supply port 4c passes through the refrigerant supply manifold, branches from the refrigerant supply port C1 of each separator 11, 12 into each refrigerant flow passage 30, and flows into the refrigerant flow path 30 to exchange heat with the fuel cell unit 1. To do. Then, the refrigerant exits the refrigerant outlet C2, collects in the refrigerant exhaust manifold, and is exhausted from the fuel cell stack S via the refrigerant exhaust port 4f.

Although illustration is omitted, the outer peripheral portion of each fuel cell 1 is provided with a sealing material for sealing a region through which the fuel gas flows, a region through which the oxidant gas flows, and a region through which the refrigerant flows. ..

The gas flow channel structure according to this embodiment will be described by taking the oxidant gas flow channel 40 formed in the separator 12 as an example. In the fuel gas passage 20 formed in the separator 11, the positions of the gas supply ports and the gas discharge ports A1 and A2 are different from the gas supply ports and the gas discharge ports B1 and B2 of the oxidant gas flow channel 40. Since the configuration is the same, the description is omitted here.

As shown in FIG. 4, the oxidant gas flow channel 40 constitutes an opposed comb-shaped flow channel (IDFF) including a substantially comb-tooth-shaped gas supply-side flow channel 50 and a substantially comb-tooth-shaped gas discharge-side flow channel 60. doing. The gas supply side flow passage 50 and the gas discharge side flow passage 60 are separated from each other by a rib R formed between the grooves of the both flow passages 50 and 60. That is, in the surface of the separator 12 in contact with the gas diffusion layer 15, the regions of the flow paths 50 and 60 do not overlap, and the internal space of the gas supply side flow path 50 and the internal space of the gas discharge side flow path 60 are , Only communicate with each other through the gas diffusion layer 15.

The gas supply side flow path 50 includes a gas supply port B1, a header flow path 51, and a plurality of gas supply flow paths 52. The header flow path 51 communicates with the gas supply port B1 and extends in the width direction Z of the separator 12. Each of the plurality of gas supply channels 52 branches from the header channel 51 and extends in a substantially straight line substantially parallel to the longitudinal direction Y of the separator 12.

The gas discharge side flow path 60 includes a gas discharge port B2, a header flow path 61, and a plurality of gas discharge flow paths 62. The header flow path 61 communicates with the gas outlet B2 and extends in the width direction Z of the separator 12. Each of the plurality of gas discharge channels 62 branches from the header channel 61 and extends in a substantially straight line substantially parallel to the longitudinal direction Y of the separator 12.

The gas supply flow paths 52 and the gas discharge flow paths 62 are alternately arranged in the width direction Z of the separator 12 at intervals. The upstream end 52a of the gas supply flow path 52 communicates with the gas supply port B1 via the header flow path 51, and the downstream end 52b is closed. On the other hand, the upstream end 62 a of the gas discharge flow channel 62 is closed, and the downstream end 62 b communicates with the gas discharge port B 2 via the header flow channel 61. The upstream end 52a of each gas supply passage 52 is located near the upstream end 62a of the gas discharge passage 62 adjacent to the gas supply passage 52. The downstream end 62b of each gas discharge flow path 62 is located near the downstream end 52b of the gas supply flow path 52 adjacent to the gas discharge flow path 62. As shown in FIG. 4, the upstream end 52a of the gas supply channel 52 is defined as a portion located on a straight line connecting the upstream ends 62a of the gas discharge channels 62 adjacent to the gas supply channel 52. You may Further, the downstream end 62b of the gas exhaust flow channel 62 may be defined as a portion located on a straight line connecting the downstream ends 52b of the gas supply flow channels 52 adjacent to the gas exhaust flow channel 62. Alternatively, when the downstream end 52b of the gas supply flow channel 52 is close to the header flow channel 61, the branch point from the header flow channel 61 may be the downstream end 62b of the gas discharge flow channel 62. When the upstream end 62a of the gas discharge flow channel 62 is close to the header flow channel 51, the branch point from the header flow channel 51 may be the upstream end 52a of the gas supply flow channel 52.

In this specification, the direction from the upstream end 52a of the gas supply flow path 52 to the downstream end 52b or the direction from the upstream end 62a of the gas discharge flow path 62 to the downstream end 62b is referred to as a "main flow direction FD". In the opposed comb-shaped flow path of the present embodiment, the main flow direction FD is substantially parallel to the longitudinal direction Y of the separator 12, the upstream ends 52a and 62a are aligned in the main flow direction FD, and the downstream ends 52b are aligned. , 62b are aligned in the main flow direction FD. Since the gas supply flow path 52 and the gas discharge flow path 62 each extend linearly along the main flow direction FD, the flow paths 52 and 62 have the same flow path length in the main flow direction FD.

The oxidant gas flowing into the oxidant gas channel 40 is distributed to each gas supply channel 52 via the header channel 51. The gas supplied to each of the gas supply channels 52 has a difference between the pressure of the gas in the gas supply channel 52 and the pressure of the gas in the gas discharge channel 62 (hereinafter, referred to as “flow channel”, as indicated by an arrow in FIG. 3). It is introduced into the gas diffusion layer 15 by the "pressure difference". Part of the oxidant gas that has entered the gas diffusion layer 15 is supplied to the electrode catalyst layer 14 when passing through the gas diffusion layer 15 under the rib R, and contributes to the electrochemical reaction. The oxidant gas that has contributed to the electrochemical reaction is forcibly pushed out to the gas discharge flow channel 62 by the pressure difference between the flow channels, and is discharged from the gas discharge port B2 via the header flow channel 61. The fuel gas that has flowed into the fuel gas flow path 20 is also forced to convection in the gas diffusion layer 15 (see the arrow in FIG. 3) and contributes to the electrochemical reaction, and then the gas exhaust port A2. Discharged from.

In the present embodiment, the flow path resistance from the upstream end 62a to the downstream end 62b of each gas discharge flow path 62 is from the upstream end 52a to the downstream end 52b of each gas supply flow path 52 adjacent to the gas discharge flow path 62. Greater than the flow path resistance of. Here, the flow path resistance is an index representing the difficulty of flow when the fluid flows in the flow path. When a predetermined fluid is flown under a predetermined condition (temperature, pressure, flow rate, etc.), the flow path resistance is larger as the flow path has a larger pressure difference (pressure loss) between the inlet and the outlet. The flow path resistance can be evaluated from the total value of the friction coefficient (friction loss coefficient) and the loss coefficient (shape loss coefficient) of the flow path, and can also be obtained through numerical calculation and experiment.

Specifically, as shown in FIG. 4, the flow passage width W1 in the range from the upstream end 62a to the downstream end 62b of each gas discharge flow passage 62 is determined by the respective gas supply flow passages adjacent to the gas discharge flow passage 62. It is smaller than the flow passage width W2 in the range from the upstream end 52a to the downstream end 52b of 52. On the other hand, the depths of the flow channels (grooves) are equal in the gas supply flow channel 52 and the gas discharge flow channel 62, as shown in FIG. As a result, the flow passage cross-sectional area of each gas discharge flow passage 62 is smaller than the flow passage cross-sectional area of each gas supply flow passage 52 adjacent to the gas discharge flow passage 62.

The flow rate of the cross flow in the facing comb-shaped flow passage changes according to the magnitude of the differential pressure between the flow passages. In particular, when the gas diffusion layer communicating between the gas supply flow path and the gas discharge flow path has a substantially uniform ventilation resistance from the upstream side region to the downstream side region of the opposing comb-shaped flow path, the cross in the main flow direction FD. The flow rate distribution of the flow is the same as the pressure difference between the flow paths in the main flow direction FD.

FIG. 5 is a schematic diagram showing how the relationship between the flow path resistances in the gas supply flow path and the gas discharge flow path adjacent to each other in the opposed comb-shaped flow path affects the distribution of the differential pressure between the flow paths, that is, the flow rate distribution of the cross flow. Is shown in. The graph of (a) shows the pressure distribution in the main flow direction FD of each of the gas supply flow path and the gas discharge flow path adjacent to each other, and the graph of (b) shows the main flow direction of the cross flow between both flow paths. The flow distribution in FD is shown. In these graphs, the broken curve shows the case where the flow path resistance of the gas discharge flow path and the flow path resistance of the gas supply flow path adjacent thereto are equal, and the solid curve shows the flow path resistance of the gas discharge flow path. The case where the flow path resistance of the gas supply flow path adjacent to this is larger than that is shown. In the graph of (a), the pressures at the upstream ends of the gas supply channels are made uniform in order to facilitate comparison between cases where the flow path resistances of both flow paths are equal (broken curve) and different cases (real curve). Is displayed. Further, in (a), the magnitude of the differential pressure between the flow paths is displayed as the space between the broken curves in the vertical direction or the space between the real curves in the vertical direction.

As indicated by a broken curve in (a), when the flow path resistance of the gas discharge flow path is equal to the flow path resistance of the adjacent gas supply flow path, the magnitude of the differential pressure between the flow paths is determined by the upstream region and the downstream side. It is almost equal to the area. Therefore, the flow rate of the cross flow in the upstream region is substantially equal to the flow rate of the cross flow in the downstream region, as shown by the broken curve in (b).

On the other hand, when the flow path resistance of the gas discharge flow path is larger than the flow path resistance of the adjacent gas supply flow path, as shown by the solid curve in (a), the flow path differential pressure in the upstream region is It becomes smaller than the differential pressure between the channels. Therefore, the flow rate of the cross flow becomes larger in the downstream region than in the upstream region, as shown by the solid curve in (b).

In the present embodiment, as described above, since the flow channel resistance of the gas discharge flow channel 62 is higher than the flow channel resistance of each gas supply flow channel 52 adjacent to the gas discharge flow channel 62, the former is equal to or less than the latter. The pressure difference between the flow paths is smaller in the upstream region and larger in the downstream region as compared with. Therefore, according to the present embodiment, the flow rate of the cross flow can be decreased in the upstream area and increased in the downstream area, thereby suppressing a decrease in gas diffusivity in the downstream area and reducing the fuel cell. The power generation efficiency of can be improved. In addition, in FIG. 4, the magnitude of the flow rate of the cross flow is shown by the magnitude of the arrow.

In addition, when the polymer electrolyte fuel cell such as the fuel cell 1 is operated under low humidification conditions, the membrane electrode assembly is dried in the upstream region of the opposing comb-shaped channel, and the proton conductivity of the electrolyte membrane is reduced. Then, the power generation performance tends to decrease. On the other hand, when operating under high humidification conditions or high current density conditions, in the downstream region, liquid water such as generated water or condensed water of humidified vapor stays in the gas diffusion layer, and diffusion of gas is hindered. Power generation performance tends to decrease.

According to the present embodiment, as described above, the flow rate of the cross flow can be decreased in the upstream area and increased in the downstream area. Therefore, it is possible to suppress the drying of the membrane electrode assembly 10 in the upstream region and prevent the liquid water from staying in the gas diffusion layer 15 in the downstream region to ensure the gas diffusibility. Thereby, the power generation performance of the fuel cell unit 1 can be improved.

Further, in the present embodiment, the flow passage cross-sectional area of the gas discharge flow passage 62 is made smaller than the flow passage cross-sectional area of the gas supply flow passage 52. Thereby, the flow passage resistance of the gas discharge flow passage 62 can be made larger than the flow passage resistance of each adjacent gas supply flow passage 52 with a simple structure.

<First Modification>
In the above-described embodiment, the flow passage width W1 of the gas discharge flow passage 62 is set to be smaller than the flow passage width W2 of the gas supply flow passage 52, so that the flow passage cross-sectional area of the gas discharge flow passage 62 becomes smaller than that of the gas supply flow passage 52. Although it is smaller than the road cross-sectional area, the method of setting the flow path cross-sectional area is not limited to this. The dimensions and cross-sectional shapes other than the width of the flow passage may be different between the gas discharge flow passage 62 and the gas supply flow passage 52, so that the flow passage cross-sectional areas of both flow passages may be different. For example, as shown in FIG. 6, while the widths of the flow channels (grooves) are unified to the same width W in the gas discharge flow channel 62 and the gas supply flow channel 52, The depth D1 may be set to be smaller than the depth D2 of the gas supply flow channel 52 flow channel (groove).

<Second Modification>
Further, as shown in FIG. 7, the cross sectional shape of the gas discharge channel 62 may be a trapezoid having the same maximum width W and maximum depth D as the rectangular cross section of the gas supply channel 52. The cross-sectional shapes of both flow paths are not particularly limited, and although not shown, they may be polygonal shapes other than rectangular and trapezoidal shapes, semicircular shapes, semielliptical shapes, semielliptical shapes, and the like.

<Third Modification>
In the above-described embodiment and modification, the flow passage cross-sectional area of the gas discharge flow passage 62 is made smaller than the flow passage cross-sectional area of the gas supply flow passage 52, so that the flow passage resistance of the gas discharge flow passage 62 is reduced. However, the method of setting the channel resistance is not limited to this. By making the shape and surface roughness of the inner wall surface of the flow passage different between the gas discharge flow passage 62 and the gas supply flow passage 52, the flow passage resistance of both flow passages may be made different. For example, while making the inner wall of the gas supply channel 52 a smooth surface (not shown), as shown in FIG. You may let me.

<Fourth Modification>
Furthermore, the flow path resistance of both flow paths may be made different by making the flow path length from the upstream ends 52a, 62a to the downstream ends 52b, 62b of each flow path different. Specifically, for example, as shown in FIG. 9, the gas supply passage 52 is linearly extended from the upstream end 52a to the downstream end 52b along the main flow direction FD, while the gas discharge passage 62 is formed. You may make it meander between the upstream end 62a and the downstream end 62b. Thereby, the flow path length from the upstream end 62a to the downstream end 62b of each gas discharge flow path 62 is from the upstream end 52a to the downstream end 52b of each gas supply flow path 52 adjacent to the gas discharge flow path 62. It is longer than the flow path length.

According to these first to fourth modified examples, the flow passage resistance of the gas discharge flow passage 62 can be made larger than the flow passage resistance of the adjacent gas supply flow passages 52 with a simple structure.

<Second Embodiment>
In the gas flow channel structure according to the above-described embodiment and modification, the flow channel resistances of the gas supply flow channel 52 and the gas discharge flow channel 62 are set evenly from the upstream ends 52a and 62a to the downstream ends 52b and 62b. It was That is, the flow path resistance of each flow path per unit length in the main flow direction FD was uniformly distributed in the main flow direction FD. However, the distribution of the flow path resistance in the main flow direction FD is not limited to this.

The second embodiment of the present invention will be described below. Here, in order to avoid duplication, the description of the configuration common to the first embodiment will be omitted, and the configuration different from the first embodiment will be described. Further, the gas flow channel structure will be described by taking the oxidant gas flow channel 40 as an example, as in the first embodiment. The fuel gas flow path 20 is different from that of the oxidant gas flow path 40 in the positions of the gas supply port and the gas discharge port, but other configurations are the same, and therefore detailed description thereof is omitted here.

In the gas flow channel structure of the present embodiment, as shown in FIG. 10, the gas supply flow channel 52 is divided into an upstream portion 52A and a downstream portion 52B. Further, the gas discharge flow channel 62 is divided into an upstream portion 62A and a downstream portion 62B, respectively. The upstream portion 52A and the downstream portion 52B each have a flow passage length that is ½ of the flow passage length from the upstream end 52a to the downstream end 52b of the gas supply flow passage 52. The upstream portion 62A and the downstream portion 62B each have a flow passage length that is ½ of the flow passage length from the upstream end 62a to the downstream end 62b of the gas discharge flow passage 62.

The minimum flow passage cross-sectional area of the gas discharge flow passage 62 is smaller than the minimum flow passage cross-sectional area of each gas supply flow passage 52 adjacent to the gas discharge flow passage 62. Here, the minimum flow passage cross-sectional area of the gas discharge flow passage 62 is the minimum value of the flow passage cross-sectional areas of the upstream portion 62A and the downstream portion 62B, and the minimum flow passage area of the gas supply passage 52. The road cross-sectional area is the minimum value of the flow path cross-sectional area of the upstream portion 52A and the flow path cross-sectional area of the downstream portion 52B. More specifically, the flow passage width W11 of each upstream portion 62A is smaller than the flow passage width W21 of each upstream portion 52A adjacent to the upstream portion 62A, and the flow passage width W12 of each downstream portion 62B is It is smaller than the flow passage width W22 of each downstream portion 52B adjacent to the downstream portion 62B. On the other hand, the depths of the flow paths (grooves) are the same in the upstream portion 52A and the upstream portion 62A, and are the same in the downstream portion 52B and the downstream portion 62B. Thus, in the present embodiment, the flow passage cross-sectional area of each upstream portion 62A is smaller than the flow passage cross-sectional area of each upstream portion 52A adjacent to the upstream portion 62A, and the flow passage cross-sectional area of each downstream portion 62B is It is smaller than the flow passage cross-sectional area of each downstream portion 52B adjacent to the downstream portion 62B.

Therefore, the flow path resistance of the upstream portion 62A of the gas discharge flow path 62 is larger than the flow path resistance of the upstream portion 52A of each gas supply flow path 52 adjacent to the gas discharge flow path 62. The flow path resistance of the downstream portion 62B of the gas discharge flow path 62 is larger than the flow path resistance of the downstream portion 52B of each gas supply flow path 52 adjacent to the gas discharge flow path 62.

According to this embodiment, the following effects can be obtained in addition to the effects of the first embodiment. That is, according to the present embodiment, in both the upstream portion (52A, 62A) and the downstream portion (52B, 62B), the flow passage resistance on the gas discharge flow passage 62 side is greater than the flow passage resistance on the gas supply flow passage 52 side. Since it is large, the pressure difference between the flow passages in the downstream region can be increased more reliably in one or both of the upstream portion and the downstream portion than in the case where the former is equal to or less than the latter. Therefore, the flow rate of the cross flow can be more reliably reduced in the upstream region and increased in the downstream region.

Note that, according to the present embodiment, the relationship of the flow resistances of the upstream portion 52A and the downstream portion 52B in the same gas supply flow passage 52 is not particularly limited, and the upstream portion 62A and the downstream in the same gas discharge flow passage 62 are the same. The relationship of the flow path resistance of the portion 62B is not particularly limited. Furthermore, the flow path resistance per unit length in the main flow direction FD in each of the upstream portions (52A, 62A) and the downstream portions (52B, 62B) changes in steps or smoothly along the main flow direction FD. It may be set to.

<Modification>
In the second embodiment, the gas supply passage 52 and the gas discharge passage 62 are divided into the upstream portion and the downstream portion, respectively, but the number of divisions is not limited to this. For example, each of the gas supply channel 52 and the gas exhaust channel 62 is divided into N elements having an even channel length, and the channel resistance of the nth element of the gas exhaust channel 62 is It may be set to be larger than the flow passage resistance of the n-th element of the supply flow passage 52. Specifically, for example, the flow passage cross-sectional area of the n-th element of the gas discharge flow passage 62 may be larger than the flow passage cross-sectional area of the n-th element of the gas supply flow passage 52. Here, N is an integer of 3 or more. n is the order in which each element is counted from the upstream side, and is an integer of 1 or more and N or less. Also in this case, the minimum flow passage cross-sectional area of each gas discharge flow passage 62 (minimum value among the flow passage cross-sectional areas of N elements) is the gas supply flow passage 52 adjacent to the gas discharge flow passage 62. Is smaller than the minimum flow channel cross-sectional area (minimum value among the flow channel cross-sectional areas of N elements).

According to this modification, the following effects can be obtained in addition to the effects of the second embodiment. That is, in this modification, since the flow passage resistance on the gas exhaust flow passage 62 side is larger than the flow passage resistance on the gas supply flow passage 52 side in all N combinations of the elements adjacent to each other, any one of the above combinations In comparison with the case where the flow path resistance on the gas exhaust flow path 62 side is less than or equal to the flow path resistance on the gas supply flow path 52 side in (1), the differential pressure between the flow paths in the downstream region can be increased more reliably. Therefore, the flow rate of the cross flow can be more surely reduced in the upstream region and increased in the downstream region.

In this modification, the relationship of the flow path resistance between the N elements in the same gas supply flow path 52 (or gas discharge flow path 62) is not particularly limited. Further, the flow path resistance per unit length in the main flow direction FD in each element may be set so as to change stepwise or smoothly along the main flow direction FD.

In addition, the upstream parts 52A and 62A and the downstream parts 52B and 62B in the second embodiment, and the elements of the gas supply flow path 52 and the gas discharge flow path 62 in the modified example thereof, are included in the first to fourth modified examples. The structure according to any one of them or a combination thereof may be applied.

<Third Embodiment>
In the gas flow path structures according to the above-described embodiment and modification, the facing comb-shaped flow paths are formed in substantially the entire surfaces of the separators 11 and 12 that contact the gas diffusion layer 15. However, the opposing comb-shaped channel may be provided in a part of the surface of the separators 11 and 12 in contact with the gas diffusion layer 15 by combining it with another type of channel such as a parallel channel or a serpentine channel. Good.

The third embodiment of the present invention will be described below. Here, in order to avoid duplication, the description of the configuration common to the first embodiment will be omitted, and the configuration different from the first embodiment will be described. Further, the gas flow channel structure will be described by taking the oxidant gas flow channel 40 as an example, as in the first embodiment. The fuel gas flow path 20 is different from that of the oxidant gas flow path 40 in the positions of the gas supply port and the gas discharge port, but other configurations are the same, and therefore the description thereof is omitted here.

In the gas flow channel structure of the present embodiment, as shown in FIG. 11, the parallel flow channel 70 is provided on the upstream side and the opposing comb-shaped flow channel is provided on the downstream side. The parallel flow channel 70 includes a gas supply port B1, an upstream header flow channel 71, a downstream header flow channel 72, and a plurality of branch flow channels 73. The upstream header flow channel 71 communicates with the gas supply port B1 and extends in the width direction Z of the separator 12. The downstream header flow passage 72 is located away from the upstream header flow passage 71 in the longitudinal direction Y of the separator 12 and extends in the width direction Z of the separator 12. Each of the plurality of branch flow channels 73 branches from the upstream header flow channel 71, extends linearly substantially parallel to the longitudinal direction Y of the separator 12, and is connected to the downstream header flow channel 72 at each downstream end. Has been done. The downstream header flow channel 72 also serves as the header flow channel 51 of the facing comb-shaped flow channel, and a plurality of gas supply flow channels 52 branch off from the downstream header flow channel 72, respectively, and the separator 12 longitudinal direction Y. Has been extended to. The structure of the facing comb-shaped flow passage on the downstream side is the same as that of the facing comb-shaped flow passage according to the above-described first and second embodiments or their modifications, and therefore detailed description thereof is omitted here.

According to this embodiment, the following effects can be obtained in addition to the effects of the first embodiment. That is, since the parallel flow path 70 does not generate forced convection in the gas diffusion layer 15, the membrane electrode assembly 10 in the upstream region is not excessively dried even under a low humidification condition, and the electrolyte in the upstream region is prevented. The decrease in proton conductivity of the membrane 13 can be suppressed. On the other hand, the opposed comb-shaped flow passage can generate a forced convection in a region closer to the electrode catalyst layer 14 in the gas diffusion layer 15, thereby increasing the concentration gradient in the region and improving the gas diffusibility. In the present embodiment, since the parallel flow channel 70 is arranged in the upstream side region where the gas concentration is relatively high and the opposing comb-shaped flow channel is arranged in the downstream side region where the gas concentration is relatively low, the parallel flow channel 70 in the upstream side region is It is possible to suppress the drying of the membrane electrode assembly 10 and to secure the gas diffusibility in the downstream region. Thereby, the power generation performance of the fuel cell unit 1 can be improved.

Although some embodiments and modifications of the present invention have been described above, these embodiments and the like are merely examples described for facilitating the understanding of the present invention, and the present invention includes the embodiments and the like. It is not limited. The technical scope of the present invention is not limited to the specific technical matters disclosed in the above-described embodiments and the like, but also includes various modifications, changes, and alternative techniques that can be easily derived therefrom.

For example, the gas flow path structures of the above-described embodiments and the like are provided on the gas diffusion layers 15 on both sides of the membrane electrode assembly 10, but they may be provided only on one side of the gas diffusion layer 15, and the fuel may be provided. You may employ|adopt only in either one of gas and oxidizing gas.

Further, the air permeability of the gas diffusion layer 15 in the above-described embodiments and the like was substantially uniform over the substantially entire surface in contact with the separators 11 and 12, but the air permeability of the gas diffusion layer was changed depending on the location. May be. For example, if you want to increase the flow rate of crossflow in a local area, such as an intermediate area between the upstream and downstream areas, set the gas diffusion layer air permeability in that local area to be lower than that in other areas. May be.

In the third embodiment, the parallel flow path is provided on the upstream side, and the facing comb-shaped flow path is provided on the downstream side. However, the arrangement of both is determined according to the environmental conditions required for the fuel cell stack, specifications, and the like. It can be changed appropriately. Further, a serpentine channel can be combined with the opposing comb-shaped channel instead of or in addition to the parallel channel. The positional relationship between the serpentine flow channel and the other opposing comb-shaped flow channels and the parallel flow channel can be appropriately set according to the environmental conditions, specifications, etc. required for the fuel cell stack.

1 Fuel cell (fuel cell)
10 Membrane Electrode Assembly 11, 12 Separator 15 Gas Diffusion Layer 52 Gas Supply Channel 52a Gas Supply Channel Upstream End 52b Gas Supply Channel Downstream End 52A Gas Supply Channel Upstream Part 52B Gas Supply Channel Downstream Part A1, B1 gas supply port 62 gas discharge flow path 62a upstream end of gas discharge flow path 62b downstream end of gas discharge flow path 62A upstream part of gas discharge flow path 62B downstream part of gas discharge flow path A2, B2 gas discharge port

Claims (6)

On the gas diffusion layer on at least one side of the membrane electrode assembly,
A plurality of gas supply passages whose upstream end communicates with the gas supply port and whose downstream end is closed;
The upstream end is closed, the downstream end is a plurality of gas discharge passages communicating with the gas discharge port, and the gas discharge flow path is alternately arranged in parallel with each other,
The upstream end of each gas supply passage is located near the upstream end of the gas discharge passage adjacent to the gas supply passage,
The downstream end of each gas discharge channel is located near the downstream end of the gas supply channel adjacent to the gas discharge channel,
Each gas flow path resistance from the upstream end of the discharge channel to the downstream end is much larger than the flow path resistance to the downstream end from the upstream end of the gas supply passage adjacent to the gas discharge channel,
The flow path length from the upstream end to the downstream end of each gas discharge flow path is characterized by being longer than the flow path length from the upstream end to the downstream end of each gas supply flow path adjacent to the gas discharge flow path. Gas flow channel structure for fuel cells. The gas supply passage is divided into an upstream portion and a downstream portion having a passage length of ½ of the passage length from the upstream end to the downstream end of the gas supply passage, Is divided into an upstream part and a downstream part having a flow path length of 1/2 of the flow path length from the upstream end to the downstream end of the gas discharge flow path,
The flow path resistance of the upstream part of the gas discharge flow path is larger than the flow path resistance of the upstream part of each gas supply flow path adjacent to the gas discharge flow path,
The fuel cell according to claim 1, wherein a flow passage resistance at a downstream portion of the gas discharge flow passage is larger than a flow passage resistance at a downstream portion of each gas supply flow passage adjacent to the gas discharge flow passage. Gas flow path structure. The gas supply passage is divided into an upstream portion, a middle flow portion, and a downstream portion having a passage length of 1/3 of the passage length from the upstream end to the downstream end of the gas supply passage, When the discharge flow passage is divided into an upstream portion, a middle flow portion, and a downstream portion having a flow passage length of 1/3 of the flow passage length from the upstream end to the downstream end of the gas discharge flow passage,
The flow path resistance of the upstream part of the gas discharge flow path is larger than the flow path resistance of the upstream part of each gas supply flow path adjacent to the gas discharge flow path,
The flow path resistance of the midstream part of the gas discharge flow path is larger than the flow path resistance of the midstream part of each gas supply flow path adjacent to the gas discharge flow path,
The fuel cell according to claim 1, wherein a flow passage resistance at a downstream portion of the gas discharge flow passage is larger than a flow passage resistance at a downstream portion of each gas supply flow passage adjacent to the gas discharge flow passage. Gas flow path structure. The minimum flow passage cross-sectional area of each gas discharge flow passage is smaller than the minimum flow passage cross-sectional area of each gas supply flow passage adjacent to the gas discharge flow passage. The gas flow channel structure of the fuel cell described. With the membrane electrode assembly,
A separator sandwiching the membrane electrode assembly,
The gas flow path defined between the gas diffusion layer of the membrane electrode assembly and the flow path groove formed in the surface of the separator in contact with the gas diffusion layer, at least a part of which is defined in any one of claims 1 to 4 . A fuel cell comprising the gas flow channel structure according to any one of claims. On the surface of the membrane electrode assembly in contact with the gas diffusion layer,
A plurality of gas supply passages whose upstream end communicates with the gas supply port and whose downstream end is closed;
The upstream end is closed and the downstream end is provided with a plurality of gas discharge flow paths communicating with the gas discharge port, and the gas discharge flow paths are alternately arranged side by side.
The upstream end of each gas supply passage is located near the upstream end of the gas discharge passage adjacent to the gas supply passage,
The downstream end of each gas discharge channel is located near the downstream end of the gas supply channel adjacent to the gas discharge channel,
Each gas flow path resistance from the upstream end of the discharge channel to the downstream end is much larger than the flow path resistance to the downstream end from the upstream end of the gas supply passage adjacent to the gas discharge channel,
The flow path length from the upstream end to the downstream end of each gas discharge flow path is characterized by being longer than the flow path length from the upstream end to the downstream end of each gas supply flow path adjacent to the gas discharge flow path. Separator.

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