JP3673252B2 - Fuel cell stack - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention includes an electrolyte membrane / electrode structure configured by sandwiching a solid polymer electrolyte membrane between a pair of electrodes, and alternately stacks the electrolyte membrane / electrode structure and a separator in a horizontal direction, The present invention relates to a fuel cell stack provided with a reaction gas channel for supplying at least a reaction gas which is a fuel gas or an oxidant gas to an electrode.
[0002]
[Prior art]
Usually, the polymer electrolyte fuel cell employs an electrolyte membrane made of a polymer ion exchange membrane (cation exchange membrane). An electrolyte membrane / electrode structure having an anode side electrode and a cathode side electrode each having a noble metal-based electrode catalyst layer bonded to a base material mainly composed of carbon on both sides of the electrolyte membrane is separated by a separator (bipolar plate). A unit cell configured by holding is provided. Usually, a predetermined number of unit cells are stacked and used as a fuel cell stack.
[0003]
In this type of fuel cell, a fuel gas supplied to the anode side electrode, for example, a gas mainly containing hydrogen (hereinafter also referred to as a hydrogen-containing gas) is ionized with hydrogen on the electrode catalyst, and passes through an electrolyte membrane. Move to the cathode side electrode side. Electrons generated in the meantime are taken out to an external circuit and used as direct current electric energy. The cathode side electrode is supplied with an oxidant gas, for example, a gas mainly containing oxygen or air (hereinafter also referred to as an oxygen-containing gas). And oxygen react to produce water.
[0004]
By the way, since the operation temperature of the polymer electrolyte fuel cell is relatively low (˜100 ° C.), the moisture that has not been absorbed by the electrolyte after being introduced into the fuel cell stack, or the moisture generated by the reaction, It is cooled in the reaction gas flow path (oxidant gas flow path and / or fuel gas flow path) in the fuel cell stack or in the pipe after being discharged from the fuel cell stack, and tends to exist in a liquid state.
[0005]
However, as described above, when water is present in the reaction gas flow path in the fuel cell stack, it becomes difficult to sufficiently supply the oxidant gas and the fuel gas to each unit cell. Thereby, the problem that the diffusibility to the electrode catalyst layer of the fuel gas and oxidizing gas which are reaction gas falls, and the cell performance deteriorates remarkably is pointed out.
[0006]
Therefore, for example, as disclosed in Patent Document 1, a supply pipe connected to the inlet side of the reaction gas flow path in the fuel cell stack, and a discharge pipe connected to the outlet side of the reaction gas flow path, And at least one pipe is provided with an enlarged portion having a stepped portion projecting downward from the other part in a part of the pipe line, or at least one pipe is directed upward toward the fuel cell stack. A fuel cell stack provided with an inclined portion that is inclined is known.
[0007]
As described above, a stepped portion protruding downward is formed in the enlarged portion provided in the pipe, and water in the pipe is stored in the stepped portion. On the other hand, the pipe is provided with an inclined portion that is inclined upward toward the fuel cell stack, so that it is possible to effectively prevent water from flowing back into the gas flow path in the fuel cell stack.
[0008]
[Patent Document 1]
JP 2000-90954 A (FIGS. 2 and 5)
[0009]
[Problems to be solved by the invention]
By the way, in said patent document 1, it is provided with the supply piping and discharge piping connected with the reaction gas flow path, and an expansion part is provided in this piping, or an inclination part is provided in this piping. For this reason, although water does not flow backward from the piping into the fuel cell stack, when a reaction gas outlet manifold communicating with the discharge side of the reaction gas flow path is provided in the fuel cell stack, the reaction gas outlet Water may accumulate in the manifold. Thereby, especially at the time of a low temperature start of 0 ° C. or less, the water in the reaction gas outlet manifold is likely to be frozen, and the reaction gas may not flow smoothly.
[0010]
The present invention solves this type of problem, and with a simple configuration, the water in the fuel cell stack can be easily and reliably discharged, and the fuel cell stack capable of maintaining a desired power generation performance. The purpose is to provide.
[0011]
[Means for Solving the Problems]
In the fuel cell stack according to claim 1 of the present invention, a reaction gas outlet manifold that extends in the stacking direction in the fuel cell stack and communicates with the discharge side of the reaction gas flow path, and the reaction gas outlet manifold are provided. An outlet pipe that communicates with the outside and extends downwardly from the fuel cell stack, and a bypass pipe that communicates with the reaction gas outlet manifold and the outlet pipe. In the bypass pipe, the first opening end position communicating with the reaction gas outlet manifold is set above the second opening end position communicating with the outlet pipe.
[0012]
For this reason, the water existing in the reaction gas outlet manifold is discharged to the outlet pipe through the bypass pipe by the action of gravity, and it is possible to effectively prevent water from staying in the reaction gas outlet manifold.
[0013]
Moreover, since the inside of the bypass pipe is sucked by the gas flow of the reaction gas discharged to the outlet pipe, the water in the reaction gas outlet manifold is surely discharged to the outlet pipe through the bypass pipe. . Furthermore, the water in the bypass line is carried to the outlet pipe by the action of the gas flow. Therefore, particularly at the time of cold start, water does not freeze in the reaction gas outlet manifold, and the desired power generation performance can be satisfactorily maintained.
[0014]
In the fuel cell stack according to claim 2 of the present invention, an outlet pipe is provided at one end in the stacking direction of the fuel cell stack, and a bypass pipe is provided at each end of the fuel cell stack in the stacking direction. It is provided in communication with the manifold. Thereby, even if the fuel cell stack is inclined in the vertical direction with respect to the stacking direction, water is discharged from one of the bypass conduits provided at both ends of the stacking direction to the outlet pipe. For this reason, the water in the reaction gas outlet manifold can be easily and reliably discharged to the outlet pipe, and good power generation performance can be ensured with a simple configuration.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a schematic perspective view of a fuel cell stack 10 according to a first embodiment of the present invention, and FIG. 2 is a partial sectional side view of the fuel cell stack 10.
[0016]
In the fuel cell stack 10, a plurality of fuel cells 12 are stacked in the direction of arrow A, and terminal terminal plates 16a and 16b, insulator plates 18a and 18b, and end plates 20a and 20b are externally provided at both ends in the stacking direction. It is sequentially arranged toward the direction. A predetermined tightening load is applied between the end plates 20 a and 20 b via a tie rod 21.
[0017]
As shown in FIG. 3, the fuel cell 12 includes an electrolyte membrane / electrode structure 22 and first and second separators 24 and 26 that sandwich the electrolyte membrane / electrode structure 22. Between the electrolyte membrane / electrode structure 22 and the first and second separators 24, 26, a seal member 28 such as a gasket is interposed so as to cover the periphery of a communication hole described later and the outer periphery of the electrode surface (power generation surface). It is disguised.
[0018]
One end edge of the fuel cell 12 in the direction of arrow B communicates with each other in the direction of arrow A, which is the stacking direction, and an oxidant gas supply communication hole 30a for supplying an oxidant gas, for example, an oxygen-containing gas. Cooling medium discharge communication holes 32b for discharging the medium and fuel gas discharge communication holes 34b for discharging a fuel gas, for example, a hydrogen-containing gas, are arranged in the direction of arrow C (vertical direction).
[0019]
The other end edge of the fuel cell 12 in the direction of the arrow B communicates with each other in the direction of the arrow A, the fuel gas supply communication hole 34a for supplying the fuel gas, and the cooling medium supply communication hole for supplying the cooling medium. 32a and an oxidant gas discharge communication hole 30b for discharging the oxidant gas are arranged in the direction of arrow C.
[0020]
The electrolyte membrane / electrode structure 22 includes, for example, a solid polymer electrolyte membrane 36 in which a perfluorosulfonic acid thin film is impregnated with water, and an anode side electrode 38 and a cathode side electrode 40 that sandwich the solid polymer electrolyte membrane 36. With.
[0021]
The anode side electrode 38 and the cathode side electrode 40 include a gas diffusion layer made of carbon paper or the like, and an electrode catalyst layer in which porous carbon particles having a platinum alloy supported on the surface are uniformly applied to the surface of the gas diffusion layer. Respectively. The electrode catalyst layers are bonded to both surfaces of the solid polymer electrolyte membrane 36 so as to face each other with the solid polymer electrolyte membrane 36 interposed therebetween. An opening 44 is formed at the center of the seal member 28 corresponding to the anode side electrode 38 and the cathode side electrode 40.
[0022]
An oxidant gas flow path 46 that communicates with the oxidant gas supply communication hole 30a and the oxidant gas discharge communication hole 30b is provided on the surface 24a of the first separator 24 on the electrolyte membrane / electrode structure 22 side. The oxidant gas channel 46 includes, for example, a plurality of grooves (serpentine grooves) extending in the arrow C direction while meandering in the arrow B direction.
[0023]
A fuel gas flow path 48 communicating with the fuel gas supply communication hole 34a and the fuel gas discharge communication hole 34b is formed on the surface 26a of the second separator 26 on the electrolyte membrane / electrode structure 22 side. The fuel gas channel 48 includes, for example, a plurality of grooves (serpentine grooves) extending in the arrow C direction while meandering in the arrow B direction. A cooling medium flow path 50 communicating with the cooling medium supply communication hole 32a and the cooling medium discharge communication hole 32b is formed on the surface 26b opposite to the surface 26a of the second separator 26. The cooling medium flow path 50 is configured by, for example, a plurality of straight flow path grooves extending in the arrow B direction.
[0024]
As shown in FIGS. 1 and 2, the end plate 20a communicates with the oxidant gas discharge communication hole 30b and the first cylindrical portion 52 constituting the oxidant gas outlet manifold and the fuel gas discharge communication hole 34b. Thus, the second cylindrical portion 54 constituting the fuel gas outlet manifold is formed to bulge in the direction of the arrow A1. The first and second cylindrical portions 52 and 54 may be formed integrally with the end plate 20a, or may be separate parts from the end plate 20a.
[0025]
An oxidant gas outlet pipe 56 is connected to the first cylindrical part 52, and a fuel gas outlet pipe 58 is connected to the second cylindrical part 54. The oxidant gas outlet pipe 56 is provided integrally with the one end portion 56a connected to the first cylindrical portion 52 and the one end portion 56a, and is directed downward in the direction away from the end plate 20a (arrow A1 direction). An inclined portion 56b inclined in the direction of the arrow C1 and an other end portion 56c extending in the horizontal direction from the lower end portion of the inclined portion 56b and connected to the discharge pipe 60 are provided.
[0026]
Similarly, the fuel gas outlet pipe 58 is provided integrally with the one end portion 58a connected to the second cylindrical portion 54 and the one end portion 58a. The fuel gas outlet pipe 58 is lowered in the direction away from the end plate 20a (direction of arrow A1). And an other end portion 58c extending in the horizontal direction from the lower end portion of the inclined portion 58b and connected to the discharge pipe 62.
[0027]
A first bypass pipe 64 is attached in communication with the lower portion of the first cylindrical portion 52 and the middle of the inclined portion 56 b of the oxidant gas outlet pipe 56. In the first bypass pipe 64, the position of the first opening end portion 66 a communicating with the first cylindrical portion 52 is farther than the position of the second opening end portion 66 b communicating with the inclined portion 56 b of the oxidant gas outlet pipe 56. It is set upward by H.
[0028]
A second bypass pipe 68 is attached in communication with the lower portion of the second cylindrical portion 54 and the inclined portion 58 b of the fuel gas outlet pipe 58. In the second bypass pipe 68, the position of the first opening end portion 70a communicating with the second cylindrical portion 54 is set higher than the position of the second opening end portion 70b communicating with the fuel gas outlet pipe 58 by a distance H. Is done. The first and second bypass conduits 64 and 68 have an inclination angle of 0 ° or more in the downward direction (arrow C1 direction) toward the arrow A1 direction.
[0029]
The operation of the fuel cell stack 10 configured as described above will be described below.
[0030]
First, as shown in FIG. 1, a fuel cell stack 10 contains a fuel gas such as a hydrogen-containing gas, an oxidant gas that is an oxygen-containing gas such as air, and a cooling medium such as pure water, ethylene glycol, or oil. Supplied.
[0031]
For this reason, as shown in FIG. 3, the oxidant gas is introduced into the oxidant gas flow path 46 of the first separator 24 from the oxidant gas supply communication hole 30a, and this oxidant gas passes through the electrolyte membrane / electrode structure 22. It moves along the cathode side electrode 40 which comprises. The fuel gas is introduced from the fuel gas supply passage 34 a into the fuel gas flow path 48 of the second separator 26 and moves along the anode side electrode 38 that constitutes the electrolyte membrane / electrode structure 22.
[0032]
Therefore, in the electrolyte membrane / electrode structure 22, the oxidant gas supplied to the cathode side electrode 40 and the fuel gas supplied to the anode side electrode 38 are consumed by an electrochemical reaction in the electrode catalyst layer, thereby generating power. Is done. The fuel gas consumed by being supplied to the anode electrode 38 is discharged in the direction of arrow A along the fuel gas discharge communication hole 34b. Similarly, the oxidant gas consumed by being supplied to the cathode side electrode 40 is discharged in the direction of arrow A along the oxidant gas discharge communication hole 30b. At that time, the reaction product water flows along the oxidant gas flow path 46 in the gravity direction, that is, from the upper side to the lower side.
[0033]
Further, the cooling medium supplied to the cooling medium supply communication hole 32a is introduced into the cooling medium flow path 50 of the second separator 26 and then flows along the arrow B direction. The cooling medium is discharged from the cooling medium discharge communication hole 32b after the electrolyte membrane / electrode structure 22 is cooled.
[0034]
In this case, in the first embodiment, the first cylindrical portion 52 is provided on the end plate 20a of the fuel cell stack 10, and the oxidant gas outlet pipe 56 is connected to the first cylindrical portion 52. A first bypass pipe 64 is connected to the cylindrical portion 52 and the oxidant gas outlet pipe 56.
[0035]
For this reason, a part of the water generated in the oxidant gas discharge communication hole 30b is directly discharged from the first cylindrical portion 52 to the discharge pipe 60 through the oxidant gas outlet pipe 56, while the remaining water is discharged. A portion is discharged to the oxidant gas outlet pipe 56 via a first bypass pipe 64 communicating with the lower part of the first cylindrical part 52.
[0036]
At that time, the first bypass pipe 64 has a distance H greater than the position of the second opening end portion 60 b communicating with the oxidizing gas outlet pipe 56 at the position of the first opening end portion 66 a communicating with the first cylindrical portion 52. Is set only above. Accordingly, in the first bypass conduit 64, a water level difference (distance H) is generated between the first opening end portion 66a and the second opening end portion 66b.
[0037]
For this reason, the water introduced into the first bypass pipe 64 flows toward the oxidant gas outlet pipe 56 and can effectively prevent water from staying in the first cylindrical portion 52. Moreover, a gas flow of the discharged oxidant gas is generated in the oxidant gas outlet pipe 56, and the inside of the first bypass pipe 64 is sucked.
[0038]
As a result, the water present on the bottom side of the first cylindrical portion 52 is reliably discharged into the oxidant gas outlet pipe 56 via the first bypass conduit 64. In particular, the first cylindrical portion 52 has a stepped portion 52a, which makes it difficult to flow water. However, the water can be discharged well into the oxidant gas outlet pipe 56. Therefore, water does not exist in the oxidant gas outlet manifold including the first cylindrical portion 52, and in particular, when the fuel cell stack 10 is started at a low temperature, water does not freeze in the oxidant gas outlet manifold. As a result, the desired power generation performance can be satisfactorily maintained.
[0039]
Further, the first bypass pipe 64 is slightly inclined in the vertically downward direction (arrow C1 direction) toward the direction away from the end plate 20a (arrow A1 direction). For this reason, the water introduced into the first bypass pipe 64 can smoothly flow toward the oxidant gas outlet pipe 56 along the inclination of the first bypass pipe 64.
[0040]
On the other hand, a fuel gas outlet pipe 58 is connected to the second cylindrical part 54 communicating with the fuel gas discharge communication hole 34b, and a second bypass pipe line is connected to the second cylindrical part 54 and the fuel gas outlet pipe 58. 68 is provided. Thereby, a part of the water generated in the fuel gas discharge communication hole 34b is directly discharged from the second cylindrical portion 54 to the fuel gas outlet pipe 58, and the remaining water is discharged to the second bypass pipe. 68 is discharged to the fuel gas outlet pipe 58. Accordingly, water can be reliably discharged from the fuel gas outlet manifold including the second cylindrical portion 54, and water freezing in the fuel gas outlet manifold can be reliably prevented.
[0041]
FIG. 4 is a schematic perspective view of a fuel cell stack 80 according to the second embodiment of the present invention, and FIG. 5 is a partial cross-sectional side view of the fuel cell stack 80. The same components as those of the fuel cell stack 10 according to the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.
[0042]
The end plate 20b constituting the fuel cell stack 80 is provided with a third cylindrical portion 82 that is positioned coaxially with the first cylindrical portion 52 of the end plate 20a and communicates with the oxidant gas discharge communication hole 30b. The end plate 20b is provided with a fourth cylindrical portion 84 that is located coaxially with the second cylindrical portion 54 of the end plate 20a and communicates with the fuel gas discharge communication hole 34b. The third and fourth cylindrical portions 82 and 84 may be formed integrally with the end plate 20b, or may be separate parts from the end plate 20b.
[0043]
The lower portion of the third cylindrical portion 82 and the first bypass conduit 64 are connected via a third bypass conduit 86, and the lower portion of the fourth cylindrical portion 84 and the second bypass conduit 68 are fourth. They are connected via a bypass line 88. The third and fourth bypass pipes 86 and 88 may be directly connected to the oxidant gas outlet pipe 56 and the fuel gas outlet pipe 58, respectively.
[0044]
In the second embodiment configured as described above, the end plate 20a that is one end in the stacking direction of the fuel cell stack 80 is provided with the first and second cylindrical portions 52 and 54, and the end plate that is the other end in the stacking direction. Third and fourth cylindrical portions 82 and 84 are provided on 20b. The first and second cylindrical portions 52, 54 are connected to the oxidant gas outlet pipe 56 and the fuel gas outlet pipe 58 via the first and second bypass pipes 64, 68, and further to the third and The fourth cylindrical portions 82 and 84 and the first and second bypass conduits 64 and 68 are connected via third and fourth bypass conduits 86 and 88.
[0045]
Thereby, for example, when the end plate 20 b side of the fuel cell stack 80 is inclined downward, the water in the third cylindrical portion 82 constituting the oxidant gas outlet manifold passes through the third bypass pipe 86 to the 1 is discharged to the bypass pipe 64 side. On the other hand, the water in the fourth cylindrical portion 84 constituting the fuel gas outlet manifold is discharged to the second bypass conduit 68 via the fourth bypass conduit 88.
[0046]
Therefore, even if the fuel cell stack 80 is inclined in the vertical direction, from one of the first and second bypass pipes 64 and 68 or the third and fourth bypass pipes 86 and 88 provided at both ends in the stacking direction, Water is discharged to the oxidant gas outlet pipe 56 and the fuel gas outlet pipe 58. Therefore, water does not stay in the fuel cell stack 80, and the water in the oxidant gas outlet manifold and the fuel gas outlet manifold can be discharged more easily and reliably to ensure the desired power generation performance. The effect of becoming.
[0047]
【The invention's effect】
In the fuel cell stack according to the present invention, it is possible to effectively prevent water existing in the reaction gas outlet manifold from being discharged to the outlet pipe through the bypass pipe and retaining water in the reaction gas outlet manifold. it can. Moreover, since the inside of the bypass pipe is sucked by the gas flow of the reaction gas discharged to the outlet pipe, the water in the reaction gas outlet manifold is surely discharged to the outlet pipe through the bypass pipe. . Therefore, particularly at the time of cold start, the water staying in the reaction gas outlet manifold does not freeze, and the desired power generation performance can be maintained satisfactorily.
[Brief description of the drawings]
FIG. 1 is a schematic perspective view of a fuel cell stack according to a first embodiment of the present invention.
FIG. 2 is a partial cross-sectional side view of the fuel cell stack.
FIG. 3 is an exploded perspective view of a fuel cell constituting the fuel cell stack.
FIG. 4 is a schematic perspective view of a fuel cell stack according to a second embodiment of the present invention.
FIG. 5 is a partial cross-sectional side view of the fuel cell stack.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10, 80 ... Fuel cell stack 12 ... Fuel cell 20a, 20b ... End plate 22 ... Electrolyte membrane and electrode structure 24, 26 ... Separator 30a ... Oxidant gas supply communication hole 30b ... Oxidant gas discharge communication hole 34a ... Fuel gas Supply communication hole 34b ... Fuel gas discharge communication hole 36 ... Solid polymer electrolyte membrane 38 ... Anode side electrode 40 ... Cathode side electrode 46 ... Oxidant gas flow path 48 ... Fuel gas flow path 52, 54, 82, 84 ... Cylindrical portion 56 ... Oxidant gas outlet pipes 56b, 58b ... Inclined portion 58 ... Fuel gas outlet pipes 60, 62 ... Discharge pipes 64, 68, 86, 88 ... Bypass pipe lines 66a, 66b, 70a, 70b ... Open ends

Claims (2)

An electrolyte membrane / electrode structure configured by sandwiching a solid polymer electrolyte membrane between a pair of electrodes, the electrolyte membrane / electrode structure and a separator are alternately stacked in a horizontal direction, and at least a fuel is provided on the electrode. A fuel cell stack provided with a reaction gas flow path for supplying a reaction gas which is a gas or an oxidant gas,
A reaction gas outlet manifold that extends in the stacking direction in the fuel cell stack and communicates with the discharge side of the reaction gas flow path;
An outlet pipe communicating with the reaction gas outlet manifold and extending outwardly and downwardly from the fuel cell stack;
A bypass line communicating with the reaction gas outlet manifold and the outlet pipe;
With
The fuel cell stack, wherein the bypass pipe has a first opening end position communicating with the reaction gas outlet manifold set above a second opening end position communicating with the outlet pipe. The fuel cell stack according to claim 1, wherein the outlet pipe is provided at one end in the stacking direction of the fuel cell stack,
The bypass pipe line is provided at both ends of the fuel cell stack in the stacking direction so as to communicate with the reaction gas outlet manifold, respectively.

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