JP2004220950A - Polymer electrolyte fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To form a passage in a separator wherein there is no retention of generated water, supply pressure is controlled in a proper range, and a reaction material is almost uniformly distributed. <P>SOLUTION: Three main meandering passages wherein straight passages horizontally flowing and return passages perpendicularly flowing at an end are connected by turns are arranged in parallel. Furthermore, communication passages 2 are arranged in positions from which distances to a fuel gas supply manifold 3 are uniform, and the three main passages are to communicated to equalize the pressure. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a polymer electrolyte fuel cell, and more particularly to a configuration of a flow path of a reactant provided in a separator sandwiching the unit cell.
[0002]
[Prior art]
In a polymer electrolyte fuel cell, a separator made of a gas-impermeable material is arranged so as to sandwich a unit cell formed by bonding a catalyst layer to both surfaces of an electrolyte from both surfaces, and the separator is provided on a surface of the separator facing the unit cell. Is formed with a groove serving as a flow path for a reactant supplied to the unit cell. As a reactant, a gas mainly composed of hydrogen is used as a fuel gas, and air is used as an oxidant gas.
Among various types of fuel cells, in a polymer electrolyte fuel cell operated at a relatively low temperature, there is a possibility that generated water generated due to the power generation reaction stays in a liquid state in a flow path and hinders the flow of a reactant. Therefore, a flow path having a substantially constant flow path cross section from the inlet to the outlet is arranged in a meandering manner on the separator so that generated water is discharged by the flow of the reactant, and a stagnant portion is generated in the flow of the reactant. There is no channel. In the case of a polymer electrolyte fuel cell having a small electrode area, it is possible to cover the entire electrode only by arranging one of the above-mentioned meandering flow paths. Since the pressure loss is increased only by the flow path and the supply pressure of the reactant becomes too high, the flow path of the reactant is formed by combining a plurality of flow paths in parallel, and the pressure loss is suppressed to an appropriate range.
[0003]
FIG. 4 is a front view of a separator showing a conventional example of a flow path of a reactant of a polymer electrolyte fuel cell, and is a front view of a separator arranged to face a fuel electrode. In the figure, the portions indicated by 3 to 8 are holes penetrating through the separator, and in the solid polymer electrolyte fuel cell constituted by stacking, 3 is a fuel gas supply manifold, and 4 is a fuel gas discharge manifold. A manifold 5 is an oxidant gas supply manifold, and 6 is an oxidant gas discharge manifold. Reference numerals 7 and 8 denote a refrigerant supply manifold and a refrigerant discharge manifold. Further, a groove indicated by reference numeral 1 in the figure is a main flow path through which a fuel gas as a reactant flows, and three meandering flow paths having a substantially constant flow path cross section correspond to the fuel gas supply manifold 3. It is formed between the fuel gas discharge manifold 4. The fuel gas supplied from the fuel gas supply manifold 3 is divided into the three main flow paths 1 and successively meanders in a linear flow path extending in the horizontal direction and a return flow path extending in the vertical direction in the figure, The fuel gas is discharged from the discharge manifold 4 to the outside.
[0004]
[Problems to be solved by the invention]
As described above, in the conventional polymer electrolyte fuel cell, the separator is provided with a flow path of a reactant composed of a plurality of main flow paths arranged in parallel as shown in FIG. However, this configuration still has the following problems.
That is, in the flow path configuration shown in FIG. 4, a plurality of main flow paths 1 are arranged in parallel, and each main flow path 1 has a straight flow path extending in the horizontal direction and a folded flow path extending in the vertical direction. Are sequentially meandering, for example, at a portion where the flow paths in which the reactants flow in opposite directions are close to each other, such as a portion indicated by reference numeral 10 in the drawing, a large pressure is applied between the adjacent flow paths. There will be a difference. On the other hand, since a porous body called a diffusion layer for allowing the reactant to permeate is disposed between the reactant flow path and the catalyst layer of the unit cell, the pressure difference between adjacent flow paths is large. Then, permeation of the reactant occurs between adjacent flow paths via the porous body. Therefore, there is a difference in flow rate between a main flow path having an adjacent flow path and a main flow path having no adjacent flow path. In addition, if the generated current density varies in the electrode plane, the flow rate of the reactant in each flow path may become uneven, and even when the flow path manufacturing accuracy is poor, the flow rate of the reactant in each flow path may be reduced. May be uneven.
[0005]
In particular, in a meandering flow path as shown in FIG. 4, the flow path is highly independent, and if there is a variation in the upstream, the influence remains down to the downstream. If it is uniform, a portion where the supply amount of the reactant is insufficient occurs in the downstream portion, and the battery characteristics are degraded.
The present invention has been made in consideration of the problems of the prior art as described above, and an object of the present invention is to provide a rectangular separator that sandwiches a unit cell without causing stagnation of generated water and at an appropriate supply pressure. An object of the present invention is to provide a polymer electrolyte fuel cell which can be operated with excellent cell characteristics, having a flow path which is suppressed to a range and through which a reactant flows almost uniformly.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, in the present invention,
A flat unit cell formed by bonding a catalyst layer to both sides of an electrolyte membrane, and a rectangular separator sandwiching the unit cell, and the separator is supplied from the outside to a surface facing the unit cell. In a polymer electrolyte fuel cell having a flow path through which a reactant is passed,
(1) The same pressure is applied between a parallel flow path in which a plurality of meandering main flow paths having substantially constant cross-sections are connected in parallel and the main flow path of the parallel flow path at a prescribed flow rate. And at least one or more communication flow paths that communicate with each other at the following positions.
[0007]
(2) In the above (1), the plurality of meandering main flow paths constituting the parallel flow path have the same flow path length, and the communication flow path has a distance from the start end of the main flow path. It is assumed that communication is made between the main flow paths at the same point.
(3) In the above (2), the plurality of meandering main flow paths constituting the parallel flow path may be formed into a straight flow extending linearly from one end to the other end corresponding to the electrode surface of the unit cell facing the flow path. Path, and a meandering path formed by alternately arranging and connecting folded paths extending in a direction orthogonal to the linear flow path arranged at the end, and the communication path is formed by the meandering path. It is arranged in at least every other straight channel or at least every other folded channel.
[0008]
In the polymer electrolyte fuel cell, if the flow path of the reactant provided in the separator is constituted by a main flow path having a meandering shape with a substantially constant flow path cross section as described in (1) above, a stagnant portion exists in the flow path. Therefore, even if water droplets of the generated water are generated, they are swept away by the flow of the reactant, and the deterioration of the characteristics due to the stagnation of the water droplets is avoided. In addition, since the plurality of main flow paths are arranged in parallel, it is possible to set the pressure loss in the flow paths within an appropriate range, and it is possible to keep the supply pressure of the reactant low. Further, between the main flow paths of the parallel flow path, at a position where the same pressure is obtained when the specified flow rate is passed, for example, as described in (2) above, when the main flow paths have the same flow path length, the main flow path At least one or more communication flow paths are arranged at the same distance from the starting end of the main flow path, so that the flow rate of the reactants in each main flow path varies due to some factors such as the fluctuation of the generated current density during operation. Even in some cases, the pressure difference between the main flow paths is eliminated by the communication flow path, the variation in the flow rate is reduced, and a predetermined battery characteristic is obtained.
[0009]
In particular, as described in (3) above, the main flow paths composed of the meandering flow paths in which the linear flow paths and the return flow paths are alternately arranged and connected are arranged in parallel to form a flow path of the reactant, and If the communication flow path is arranged in every other linear flow path or at least every other return flow path, the pressure of the reactant flowing through each main flow path in each communication flow path is adjusted to the same pressure Therefore, even if there is a variation in the flow rate of the reactant in each main flow path, it is eliminated at an early stage, and the flow rate can be adjusted effectively.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of a polymer electrolyte fuel cell according to the present invention will be described with reference to the drawings.
<Example 1>
FIG. 1 is a front view of a separator showing a flow path of a reactant according to a first embodiment of the polymer electrolyte fuel cell of the present invention. As in FIG. FIG. Note that components having the same functions as the components in FIG. 4 are denoted by the same reference numerals as those used in FIG. 4, and redundant description will be omitted.
In the separator of this embodiment, a gas-impermeable resin-impregnated carbon having a thickness of 1.5 mm is provided with through-holes for various manifolds 3 to 8, and a groove having a depth of 0.75 mm is processed. A flow path through which gas flows is formed. The formed fuel gas flow path includes three main flow paths 1 each composed of a meandering flow path in which a straight flow path flowing in the horizontal direction in the figure and a folded flow path flowing vertically in the end portion are alternately connected. It comprises a parallel flow passage arranged in parallel and a communication flow passage 2 connecting the three main flow passages 1. The main flow paths 1 are each formed as a flow path having a constant flow path cross section, and are arranged so that the flow path lengths of the three main flow paths 1 from the fuel gas supply manifold 3 to the fuel gas discharge manifold 4 are the same. Have been.
[0011]
The communication flow path 2 is disposed so as to communicate with the three main flow paths 1 orthogonal to the flow path at a point where the distance from the fuel gas supply manifold 3 to the straight flow path of the meandering flow path is the same. I have. In the meandering flow path of the present embodiment, the flow path is formed such that the fuel gas is immediately led from the fuel gas supply manifold 3 to the linear flow path. Therefore, as shown in FIG. By arranging the communication flow path 2 in the odd-numbered linear flow path calculated from the above, the main flow path 1 can be made orthogonal.
In this embodiment, one communication channel 2 is arranged at the center of the odd-numbered linear flow channel of the main flow channel 1. However, the communication flow channel 2 may be any one of the linear flow channels. It may be arranged at a position, or two or more may be arranged in the same straight channel. Further, among the odd-numbered linear flow paths, for example, the communication flow path 2 disposed in the most downstream linear flow path may be omitted.
[0012]
<Example 2>
FIG. 2 is a front view of a separator showing a flow path of a reactant according to a second embodiment of the polymer electrolyte fuel cell of the present invention. As in FIG. 1 shown in the first embodiment, FIG. It is a front view of the separator arrange | positioned facing. In this figure, components having the same functions as those shown in FIGS. 4 and 1 are denoted by the same reference numerals.
The fuel gas flow path provided in the separator of the present embodiment is a meandering flow path in which a straight flow path flowing vertically in the figure and a folded flow path flowing horizontally at the end are alternately connected. The main flow path 1 includes a parallel flow path in which the main flow paths 1 are arranged in parallel, and a communication flow path 2 that connects the three main flow paths 1 in a folded flow path. Also in this embodiment, the main flow paths 1 are formed as flow paths each having a fixed flow path cross section, and the flow path length of the three main flow paths 1 from the fuel gas supply manifold 3 to the fuel gas discharge manifold 4 is reduced. They are arranged to be identical. In the meandering flow path of the present embodiment, the flow path is formed so that the fuel gas supplied from the fuel gas supply manifold 3 is immediately bent at a right angle and guided to a linear flow path. If the communication passages 2 are arranged in the upper and lower return passages so as to be orthogonal to the flow, the three main passages 1 communicate with each other at the same distance from the fuel gas supply manifold 3. . By arranging the communication flow path 2 in this manner, the pressure of the fuel gas flowing through the three main flow paths 1 is appropriately made uniform, and the flow rate is appropriately adjusted.
[0013]
<Example 3>
FIG. 3 is a front view of a separator showing a flow path of a reactant according to a third embodiment of the polymer electrolyte fuel cell of the present invention. As shown in FIGS. 1 is a front view of a separator to be used.
In the separator of this embodiment, as in the second embodiment shown in FIG. 2, a straight flow path flowing in the vertical direction in the figure and a folded flow path flowing in the horizontal direction at the end are alternately connected. A parallel flow path in which three main flow paths 1 composed of meandering flow paths are arranged in parallel is defined as a main flow path of the fuel gas. This embodiment is different from the second embodiment in the installation location of the communication flow path 2 that communicates the three main flow paths 1, and in the present embodiment, the communication path 2 is disposed at substantially the center of each straight flow path. Have been. In order to communicate the three main flow paths 1 at the same distance from the fuel gas supply manifold 3, the communication flow path 2 is arranged obliquely to the three main flow paths 1.
[0014]
In each of the first to third embodiments, only the flow path of the fuel gas formed in the separator arranged to face the fuel electrode side is described in all cases. If the flow path of the oxidizing gas formed in the separator arranged oppositely is formed in accordance with the same design concept, the pressure of the oxidizing gas flowing through each main flow path is adjusted to the same pressure by the communication flow path, Since the flow rate of the oxidizing gas in each main flow path is effectively adjusted, a stable power generation operation can be performed.
[0015]
【The invention's effect】
As described above, according to the present invention,
A flat unit cell formed by bonding a catalyst layer to both sides of an electrolyte membrane, and a rectangular separator sandwiching the unit cell, and the separator is supplied from the outside to a surface facing the unit cell. In a polymer electrolyte fuel cell having a flow channel through which a reactant is passed, the flow channel is configured as described in claim 1 or claim 2, and further according to claim 3 or 4. As a result, there is no stagnation of generated water in the flow path of the reactant, the reactant can be supplied at a low pressure, and the pressure between the flow paths is effectively adjusted so that the reactant flows almost uniformly. As a result, a polymer electrolyte fuel cell capable of operating with excellent cell characteristics was obtained.
[Brief description of the drawings]
FIG. 1 is a front view of a separator showing a flow path of a reactant of a first embodiment of a polymer electrolyte fuel cell of the present invention; FIG. 2 is a second embodiment of a polymer electrolyte fuel cell of the present invention; FIG. 3 is a front view of a separator showing a flow path of a reactant of the present invention. FIG. 3 is a front view of a separator showing a flow path of a reactant of a third embodiment of the polymer electrolyte fuel cell of the present invention. Front view of a separator showing a conventional example of a flow path of a reactant of a fuel cell [Description of reference numerals]
DESCRIPTION OF SYMBOLS 1 Main flow path 2 Communication flow path 3 Fuel gas supply manifold 4 Fuel gas discharge manifold 5 Oxidant gas supply manifold 6 Oxidant gas discharge manifold

Claims (4)

A flat unit cell formed by bonding a catalyst layer to both surfaces of an electrolyte membrane, and a rectangular separator sandwiching the unit cell, and the separator is supplied from the outside to a surface facing the unit cell. In a polymer electrolyte fuel cell having a flow path through which a reactant is passed,
The flow path is a parallel flow path in which a plurality of flow path cross sections are connected in parallel in a meandering main flow path having a substantially constant meandering position, and at a position where the same pressure is applied between the main flow paths of the parallel flow path at a prescribed flow rate. A polymer electrolyte fuel cell, comprising: at least one or more communicating flow paths that communicate with each other. 2. The polymer electrolyte fuel cell according to claim 1, wherein the plurality of meandering main flow paths forming the parallel flow path have the same flow path length, and the communication flow path is a start end of the main flow path. A solid polymer fuel cell, wherein the main flow passages communicate with each other at the same distance from the main flow path. 3. The polymer electrolyte fuel cell according to claim 2, wherein the plurality of meandering main flow paths constituting the parallel flow path extend linearly from one end to the other end corresponding to the electrode surfaces of the opposed unit cells. A linear flow path and a meandering flow path in which the return flow path extending in a direction orthogonal to the linear flow path provided at the end portion are alternately arranged and connected, and the communication flow path is a meandering flow. A polymer electrolyte fuel cell, wherein the polymer electrolyte fuel cells are arranged in at least one other linear flow path. 3. The polymer electrolyte fuel cell according to claim 2, wherein the plurality of meandering main flow paths constituting the parallel flow path extend linearly from one end to the other end corresponding to the electrode surfaces of the opposed unit cells. A linear flow path and a meandering flow path in which the return flow path extending in a direction orthogonal to the linear flow path provided at the end portion are alternately arranged and connected, and the communication flow path is a meandering flow. A polymer electrolyte fuel cell, wherein the fuel cell is disposed in at least one of the folded paths.

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