JP4595282B2 - Polymer electrolyte fuel cell - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a structure of a flow path of a reactant provided in a solid polymer fuel cell, particularly a separator sandwiching the unit cell.
[0002]
[Prior art]
In a polymer electrolyte fuel cell, a separator made of a gas-impermeable material is disposed so that a unit cell formed by joining a catalyst layer on both sides of an electrolyte is sandwiched from both sides, and the separator is opposed to the unit cell. Is formed with a groove that serves as a flow path for the reactant supplied to the unit cell. As the reactant, a gas mainly containing hydrogen as a fuel gas and air as an oxidant gas are used.
In a polymer electrolyte fuel cell that is operated at a relatively low temperature among various types of fuel cells, the generated water that accompanies the power generation reaction may stay in the flow path in a liquid state, possibly hindering the flow of reactants. Therefore, a flow path with a substantially constant flow path cross section from the inlet to the outlet is meandered on the separator so that the generated product water is discharged by the flow of the reactive substance, and a stagnant portion is generated in the flow of the reactive substance. There are no flow paths. Further, in the case of a polymer electrolyte fuel cell having a small electrode area, it is possible to cover the entire electrode by arranging only one meandering flow path as described above. Since the pressure loss is increased only by the flow path and the supply pressure of the reactant is 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 reactant flow path of a polymer electrolyte fuel cell, and is a front view of a separator disposed to face a fuel electrode. In the figure, the portions indicated by 3 to 8 are all holes that penetrate the separator. In the polymer electrolyte fuel cell constituted by stacking, 3 is a fuel gas supply manifold, 4 is a fuel gas discharge Manifold 5 is an oxidizing gas supply manifold, and 6 is an oxidizing gas discharge manifold. Reference numerals 7 and 8 denote a refrigerant supply manifold and a refrigerant discharge manifold. Further, a groove denoted by reference numeral 1 in the figure is a main flow path through which fuel gas as a reactant flows, and three meandering flow paths having a substantially constant flow path cross section are connected 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 three main flow paths 1 and flows in a meandering manner in a linear flow path extending in the horizontal direction and a folded flow path extending in the vertical direction in the figure. It is discharged from the fuel gas 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 reactant flow path composed of a plurality of main flow paths arranged in parallel as shown in FIG. Although it is supplied, this configuration still has the following problems.
That is, in the flow channel configuration shown in FIG. 4, a plurality of main flow channels 1 are arranged in parallel, and each main flow channel 1 is a straight flow channel extending in the horizontal direction and a folded flow channel extending in the vertical direction. In a region 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 figure, 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 the adjacent flow channels through the porous body. Accordingly, there is a difference in flow rate between the main channel having the adjacent channel and the main channel not having the adjacent channel. In addition, if the generated current density varies within the electrode surface, the flow rate of the reactants in each channel may be non-uniform, and even if the flow channel manufacturing accuracy is poor, the reactant flow rate per channel May become non-uniform.
[0005]
In particular, the meandering flow path as shown in FIG. 4 has high independence of the flow path. Therefore, if variations occur upstream, the influence remains downstream, and thus the flow rate of the reactants is not improved in each flow path. If it becomes uniform, a portion where the supply amount of the reactant is insufficient is generated in the downstream portion, and the battery characteristics are deteriorated.
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 the unit cell without any retention of generated water and an appropriate supply pressure. An object of the present invention is to provide a polymer electrolyte fuel cell that can be operated with excellent cell characteristics as a flow path that is limited to a range and that allows reactants to flow substantially uniformly.
[0006]
In order to achieve the above object, in the present invention,
A flat unit cell formed by joining a catalyst layer on both surfaces of an electrolyte membrane, and a rectangular separator sandwiching the unit cell, and the separator is supplied from the outside to the surface facing the unit cell In a polymer electrolyte fuel cell having a flow path for allowing a reactant to flow,
(1) The flow path has the same pressure when a prescribed flow rate is passed between a parallel flow path in which a plurality of meandering main flow paths having a constant flow path cross section are connected in parallel and the main flow paths of the parallel flow paths. It is composed of at least one communication channel that communicates at a position,
(2) The plurality of meandering main flow paths constituting the parallel flow paths have the same flow path length and are linear from one end to the other end corresponding to the electrode surfaces of the opposing unit cells. It consists of meandering channels in which the linear channels extending and the folded channels extending in the direction perpendicular to the linear channels arranged at the ends are alternately connected,
(3) The communication channel communicates between the main channels at the same distance from the starting end of the main channel, and between the linear channels at both ends of the meandering channel and the linear channels at both ends. It is assumed that at least every other one of the plurality of straight flow paths positioned at the position is arranged.
[0007]
Alternatively, in place of the above configuration (3),
(3 ′) The communication flow path communicates between the main flow paths at the same distance from the start end of the main flow path, and is arranged in at least every other folded flow path of the meandering flow path And
[0008]
In the polymer electrolyte fuel cell, if the flow path of the reactant provided in the separator is configured as described in (1) and (2) above, there is no staying portion in the flow path, so that water droplets of product water are generated. However, it will be swept away by the flow of reactants, avoiding the degradation of characteristics due to the retention of water droplets. In addition, since the plurality of main flow paths are arranged in parallel, the pressure loss of the flow paths can be set within an appropriate range, and the supply pressure of the reactant can be kept low.
In addition, at least one position between the main flow paths of the parallel flow paths is at a position where the same pressure is reached when the specified flow rate flows, that is, at a point where the distance from the start end of each main flow path having the same flow path length is the same. Since the above communication flow paths are arranged, even if there is a variation in the flow rate of the reactant in each main flow path due to some factors such as variations in generated current density during operation, each main flow path is caused by this communication flow path. The pressure difference between the two is eliminated, the variation in flow rate is relaxed, and predetermined battery characteristics are obtained.
[0009]
Further, as described in the above (3) or (3 ′), each main flow path composed of meandering flow paths in which straight flow paths and turn-back flow paths are alternately arranged and connected is arranged in parallel to allow the flow of the reactant. If a communication channel is arranged in at least every other linear channel, or at least every other folded channel, the reactants flowing through the main channels in each communication channel are formed. Since the pressure is adjusted to the same pressure, 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 is adjusted effectively.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the polymer electrolyte fuel cell of 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 in a first embodiment of a polymer electrolyte fuel cell according to the present invention. Like FIG. 4, a separator disposed facing a fuel electrode side. FIG. Components having the same functions as those in FIG. 4 are denoted by the same reference numerals as those used in FIG.
In the separator of this example, 1.5 mm thick gas-impermeable resin-impregnated carbon is provided with through holes to form various manifolds 3 to 8, and a groove having a depth of 0.75 mm is processed to allow fuel gas to flow. The flow path to be formed is formed. The formed fuel gas flow path is composed of three main flow paths 1 each consisting of a meandering flow path in which a straight flow path flowing in the horizontal direction and a folded flow path flowing in the vertical direction at the end portion are alternately connected in the drawing. A parallel flow path arranged in parallel and a communication flow path 2 communicating the three main flow paths 1 are configured. The main flow paths 1 are each formed as a flow path having a constant flow cross section, and are arranged so that the flow lengths from the fuel gas supply manifold 3 to the fuel gas discharge manifold 4 of the three main flow paths 1 are the same. Has been.
[0011]
The communication flow path 2 is arranged so as to communicate the three main flow paths 1 at right angles to the flow paths at the same distance from the fuel gas supply manifold 3 of the linear flow path of the meandering flow path. Yes. In the meandering flow path of the present embodiment, the flow path is formed so that the fuel gas is immediately guided from the fuel gas supply manifold 3 to the linear flow path. Therefore, as shown in FIG. If the communication flow path 2 is arranged in the odd-numbered linear flow paths calculated from the above, it can be orthogonal to the main flow path 1.
In the present embodiment, one communication channel 2 is arranged at the center of the odd-numbered linear channel of the main channel 1, but the communication channel 2 is any of the linear channels. It may be arranged at a position, or two or more may be arranged in the same linear flow path. In addition, among the odd-numbered linear channels, for example, the communication channel 2 arranged in the most downstream linear channel may be omitted.
[0012]
<Example 2>
FIG. 2 is a front view of the separator showing the flow path of the reactant in the second embodiment of the polymer electrolyte fuel cell of the present invention. Like FIG. 1 shown in the first embodiment, FIG. It is a front view of the separator arrange | positioned facing. Also 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 composed of a meandering flow path in which a straight flow path that flows in the vertical direction and a folded flow path that flows in the horizontal direction at the ends are alternately connected in the figure. 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 the folded flow path. Also in this embodiment, the main flow path 1 is formed as a flow path having a constant flow path cross section, and the flow length from the fuel gas supply manifold 3 to the fuel gas discharge manifold 4 of the three main flow paths 1 is the same. They are arranged to be identical. In the meandering flow path of this embodiment, the flow path is formed so that the fuel gas supplied from the fuel gas supply manifold 3 is bent at right angles and led to the straight flow path. If the communicating flow path 2 is arranged in the upper and lower folded flow paths so as to be orthogonal to the flow as much as possible, the three main flow paths 1 communicate with each other at the same distance from the fuel gas supply manifold 3. . If the communication flow path 2 is arranged in this way, the pressure of the fuel gas flowing through the three main flow paths 1 is made uniform as appropriate, and the flow rate is adjusted appropriately.
[0013]
<Example 3>
FIG. 3 is a front view of the separator showing the flow path of the reactant in the third embodiment of the polymer electrolyte fuel cell of the present invention, and is arranged facing the fuel electrode side as in FIGS. It is a front view of a separator.
Also in the separator of this example, like the second example shown in FIG. 2, the linear flow channel flowing in the vertical direction and the folded flow channel flowing in the horizontal direction at the end portion are alternately connected in the drawing. A parallel flow path in which three main flow paths 1 composed of meandering flow paths are arranged in parallel is used as a main flow path for fuel gas. The difference of this embodiment from the second embodiment is the installation location of the communication flow path 2 that connects the three main flow paths 1, and in this embodiment, it is arranged at substantially the center of each linear flow path. Has been. In order to connect 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 described above, only the fuel gas flow path formed in the separator disposed opposite to the fuel electrode side is illustrated and described. If the flow path of the oxidant gas formed in the separator disposed opposite is also formed in accordance with the same design concept, the pressure of the oxidant gas flowing through each main flow path is adjusted to the same pressure by the communication flow path, Since the flow rate of the oxidant gas in each main channel is effectively adjusted, stable power generation operation is possible.
[0015]
【The invention's effect】
As described above, according to the present invention, a flat unit cell formed by joining a catalyst layer on both surfaces of an electrolyte membrane, and a rectangular separator that sandwiches the unit cell, and the above-mentioned In the polymer electrolyte fuel cell having a flow path for allowing a separator to flow a reactant supplied from the outside to a surface facing the unit cell, the flow path is configured as in claim 1 or claim 2. Therefore, there is no stagnation of product water in the flow path of the reactants, the reactants can be supplied at a low pressure, and the pressure between the channels is effectively adjusted to allow the reactants to flow almost uniformly. Since the flow path was provided, a polymer electrolyte fuel cell capable of operating with excellent battery characteristics was obtained.
[Brief description of the drawings]
FIG. 1 is a front view of a separator showing a flow path of a reactant in 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 the separator showing the flow path of the reactant in the third embodiment of the polymer electrolyte fuel cell of the present invention. FIG. 4 is a front view of the separator showing the flow path of the reactant. Front view of a separator showing a conventional example of a reactant flow path of a fuel cell [Description of symbols]
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 (2)

A flat unit cell formed by joining a catalyst layer on both surfaces of an electrolyte membrane, and a rectangular separator sandwiching the unit cell, and the separator is supplied from the outside to the surface facing the unit cell In the polymer electrolyte fuel cell having a flow path for allowing the reactant to flow,
The flow path is a parallel flow path in which a plurality of channel cross section connects the main channel of a certain serpentine in parallel, at a position where the same pressure between at specified flow rate through flow of the main flow path of the parallel flow paths It is composed of at least one communication channel that communicates,
A plurality of meandering main flow paths constituting the parallel flow paths have the same flow path length and linearly extend from one end to the other corresponding to the electrode surfaces of the opposing unit cells. A meandering channel formed by alternately arranging and connecting a channel and a folded channel extending in a direction perpendicular to the linear channel disposed at the end,
The communication channel communicates between the main channels at the same distance from the starting end of the main channel, and is positioned between the linear channels at both ends of the meandering channel and the linear channels at both ends. A polymer electrolyte fuel cell , wherein at least every other one of a plurality of straight flow paths is arranged. A flat unit cell formed by joining a catalyst layer on both surfaces of an electrolyte membrane, and a rectangular separator sandwiching the unit cell, and the separator is supplied from the outside to the surface facing the unit cell In the polymer electrolyte fuel cell having a flow path for allowing the reactant to flow,
The flow path is a parallel flow path in which a plurality of channel cross section connects the main channel of a certain serpentine in parallel, at a position where the same pressure between at specified flow rate through flow of the main flow path of the parallel flow paths It is composed of at least one communication channel that communicates,
A plurality of meandering main flow paths constituting the parallel flow paths have the same flow path length and linearly extend from one end to the other corresponding to the electrode surfaces of the opposing unit cells. A meandering channel formed by alternately arranging and connecting a channel and a folded channel extending in a direction perpendicular to the linear channel disposed at the end,
The communication channel is characterized in that it communicates between the main channels at the same distance from the starting end of the main channel, and is arranged in at least every other folded channel of the meandering channel. Solid polymer fuel cell.

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