JP2009152069A - Fuel cell stack - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell stack capable of promoting drainage of liquid water in an offgas manifold. <P>SOLUTION: The fuel cell stack (100) is provided with a laminate which has a separator (40) and a membrane-electrode assembly (30) equipped with a seal member (32) laminated alternatively, with an offgas manifold formed penetrating the seal members and the separators in a laminate direction, and a swirling flow generation means (50) fitted inside the offgas manifold and generating swirling flow in the gas flow in the offgas manifold. Either the separator or the seal member adjacent to each other and structuring an inner wall of the offgas manifold has a convex part being convex toward inside of the manifold in relation to the other, and a concave part being concave to the other. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a fuel cell stack in which a plurality of fuel cells are stacked.

  A fuel cell is a device that generally obtains electric energy using hydrogen and oxygen as fuel. This fuel cell is environmentally superior and can realize high energy efficiency, and therefore has been widely developed as a future energy supply system. In particular, since the polymer electrolyte fuel cell operates at a relatively low temperature among various types of fuel cells, it has a good startability. For this reason, research has been actively conducted for practical application in various fields.

  In many cases, a plurality of fuel cells are stacked and used as a stack. In this case, a manifold for the reaction gas to flow is formed in the stack. In particular, it is known that liquid water tends to accumulate in an off-gas manifold. Since this liquid water expands by freezing below freezing point, the sealing member may be damaged and gas leakage may occur. Therefore, a technique using a swirling flow generating means for discharging water generated in the off-gas manifold has been disclosed (for example, see Patent Document 1).

JP 2005-339814 A

  However, in the technique of Patent Document 1, water discharge may be hindered by a step in the manifold. In this case, liquid water may not be discharged.

  An object of this invention is to provide the fuel cell stack which can accelerate | stimulate discharge | emission of the liquid water in an off-gas manifold.

  The fuel cell stack according to the present invention includes a laminate in which membrane-electrode assemblies having a seal member and separators are alternately stacked and an off-gas manifold is formed that penetrates the seal member and the separator in the stacking direction. And a swirling flow generating means for generating a swirling flow in the gas flowing in the off-gas manifold, and one of the separator and the seal member constituting the inner wall of the off-gas manifold adjacent to the other protrudes inside the manifold. And a concave portion that is concave with respect to the other.

  In the fuel cell stack according to the present invention, the swirling flow is imparted to the off gas by the swirling flow generating means. By this swirling flow, the liquid water accumulated in the concave portion of the seal member moves in the swirling flow direction. In this case, since the liquid water moves from the concave portion to the convex portion of the seal member, it can get over the separator. Thereby, the liquid water is discharged in the axial direction of the off-gas manifold. Moreover, the liquid water which was not discharged | emitted by offgas accumulates in the recessed part of a separator. However, this liquid water further moves in the swirl direction of the off gas. In this case, since the liquid water moves from the concave portion to the convex portion of the separator, it can get over the seal member. Thereby, the liquid water is discharged in the axial direction of the off-gas manifold. From the above, the discharge of liquid water in the off-gas manifold can be promoted.

  The swirling flow generating means may have a spiral fin shape. The swirl flow generating means may be a plurality of twisted wires. In the off-gas manifold, one of the separator and the seal member may have a substantially rectangular hole shape, and the other may have an elliptical hole shape. The off gas manifold may be a fuel gas off gas manifold.

  According to the present invention, the discharge of liquid water in the off-gas manifold can be promoted.

  Hereinafter, the best mode for carrying out the present invention will be described.

  FIG. 1 is a view for explaining a fuel cell stack 100 according to a first embodiment of the present invention. FIG. 1A is a schematic overview of the fuel cell stack 100. As shown in FIG. 1A, the fuel cell stack 100 has a structure in which both ends of a stacked body in which a plurality of cells 10 are stacked are fastened by an end plate 20a and an end plate 20b.

  Next, the stacked body of the cells 10 will be described. FIG. 1B is a schematic cross-sectional view of the stacked body of the cells 10. As shown in FIG. 1B, the stacked body of the cells 10 has a structure in which a membrane-electrode assembly 30 with a seal member is stacked via a separator 40. The membrane-electrode assembly 30 with a seal member includes a power generation unit 31 and a seal member 32. The power generation unit 31 has a structure in which a solid polymer electrolyte membrane having proton conductivity is sandwiched between an anode and a cathode. The seal member 32 is a member for suppressing gas leakage or the like, and is made of, for example, rubber. Details of the seal member 32 will be described later. The separator 40 is made of a conductive member such as stainless steel. The separator 40 is formed with a flow path for the fuel gas and the oxidant gas to flow.

  FIG. 2A is a plan view of the membrane-electrode assembly 30 with a seal member. FIG. 2B is a plan view of the separator 40. As shown in FIG. 2A, the membrane-electrode assembly 30 with a seal member has a structure in which a seal member 32 covers the periphery of the power generation unit 31. Holes 33 to 38 are formed in the seal member 32. As shown in FIG. 2B, the separator 40 has holes 43 to 48 formed therein.

  The holes 33 and 43 communicate with each other to form an oxidant gas manifold. The holes 34 and 44 communicate with each other to form a fuel gas manifold. The holes 35 and 45 communicate with each other to form a refrigerant inlet manifold. The holes 36 and 46 communicate with each other to form a fuel off gas manifold. The holes 37 and 47 communicate with each other to form a refrigerant outlet manifold. Hole 38 and hole 48 communicate with each other to form an oxidant off-gas manifold.

  The fuel gas manifold communicates with the anode and the fuel off gas manifold via a fuel gas passage (not shown). The oxidant manifold communicates with the cathode and the oxidant offgas manifold via an oxidant gas flow path (not shown). The refrigerant inlet manifold communicates with the refrigerant outlet manifold via a refrigerant channel (not shown).

  Next, power generation in the fuel cell stack 100 will be described. First, the fuel gas is supplied to the anode via the fuel gas manifold. Hydrogen contained in the fuel gas is dissociated into protons and electrons via the anode catalyst. Protons pass through the solid polymer electrolyte membrane and reach the cathode. On the other hand, the oxidant gas is supplied to the cathode via the oxidant gas manifold. At the cathode, protons react with oxygen contained in the oxidant gas via a catalyst. Thereby, electric power is generated and water is generated.

  In addition, the fuel off gas after being used for power generation is discharged from the anode via the fuel off gas manifold. The oxidant off gas after being used for power generation is discharged from the cathode via the oxidant off gas manifold. Further, the refrigerant is supplied to the refrigerant flow path via the refrigerant inlet manifold. It is discharged via the refrigerant outlet manifold. Thereby, the fuel cell stack 100 is maintained at a predetermined temperature.

  Next, details of the fuel off-gas manifold will be described. FIG. 3A is a schematic diagram showing a fuel off-gas manifold in the fuel cell stack 100. As shown in FIG. 3A, the swirl flow generating means 50 is arranged in the fuel off-gas manifold so as to extend in the gas flow direction. The swirl flow generating means 50 has a structure for imparting swirl flow to the fuel off gas. For example, as shown in FIG. 3B, the swirl flow generating means 50 may have a spiral fin shape. Further, the swirling flow generating means 50 may be formed by twisting a plurality of wires as shown in FIG. Thus, the swirl flow generating means 50 may have any structure as long as it provides a swirl flow to the fuel off gas.

  FIG. 4A is a diagram illustrating the shape of the hole 36 in the seal member 32. As shown in FIG. 4A, the hole 36 has an elliptical shape. FIG. 4B is a diagram illustrating the shape of the hole 46 in the separator 40. As shown in FIG. 4B, the hole 46 has a rectangular shape. The inner wall surface of the fuel off gas manifold in this case will be described.

  FIG. 4C is a view of the fuel off-gas manifold as viewed from the flow direction of the fuel off-gas. FIG.4 (d) is OA plane sectional drawing of FIG.4 (c). FIG. 4E is a cross-sectional view taken along the plane OB of FIG. As shown in FIG. 4D, in the cross section taken along the plane OA, the separator 40 is convex toward the inside of the fuel off-gas manifold with respect to the adjacent seal member 32. This protrusion is referred to as a protrusion of the separator 40. Further, the seal member 32 is recessed inside the fuel off-gas manifold with respect to the separator 40. This recess is referred to as a recess of the seal member 32.

  On the other hand, as shown in FIG. 4 (e), in the O-B cross section, the separator 40 is recessed inside the fuel off-gas manifold with respect to the adjacent seal member 32. This recess is referred to as a recess of the separator 40. Further, the seal member 32 is convex toward the inside of the fuel off-gas manifold with respect to the separator 40. This protrusion is referred to as a protrusion of the seal member 32.

  Next, the relationship between the fuel off gas and the liquid water in the fuel off gas manifold will be described. FIG. 5A is a schematic diagram showing a state in which the swirl flow generating means 50 is disposed in the fuel off-gas manifold. As shown in FIG. 5A, when the fuel off-gas flows into the fuel off-gas manifold, the swirling flow generating means 50 imparts a swirling flow to the fuel off-gas.

  FIG. 5B is a schematic diagram showing the flow of liquid water in the fuel off-gas manifold. As shown in FIG. 5B, it is assumed that liquid water is accumulated in the recess of the seal member 32. In this case, since the separator 40 becomes a wall, it becomes difficult to discharge liquid water in the axial direction of the fuel off-gas manifold. However, when a swirl flow is applied to the fuel off gas, the liquid water accumulated in the recess of the seal member 32 moves in the swirl flow direction of the fuel off gas. In this case, since the liquid water moves from the concave portion to the convex portion of the seal member 32, the liquid water can get over the separator 40. Thereby, the liquid water is discharged in the axial direction of the fuel off-gas manifold.

  Note that liquid water that has not been discharged by the fuel off-gas accumulates in the recesses of the separator 40. However, this liquid water further moves depending on the swirl direction of the fuel off gas. In this case, since the liquid water moves from the concave portion of the separator 40 to the convex portion, the liquid member can get over the seal member 32. Thereby, the liquid water is discharged in the axial direction of the fuel off-gas manifold.

  As described above, by providing the seal member 32 and the separator 40 with the concave and convex portions and arranging the swirling flow generating means 50, it is possible to promote the discharge of the liquid water accumulated in the step of the fuel off-gas manifold. Thereby, the freezing of liquid water can be suppressed. As a result, damage to the seal member 32 can be suppressed and gas leakage can be suppressed.

  In this embodiment, the shape of the hole 36 is elliptical and the shape of the hole 46 is rectangular. However, the present invention is not limited to this. The shape of the hole 36 and the hole 46 is particularly limited as long as one of the adjacent separator 40 and the seal member 32 includes a convex portion that is convex toward the inside of the manifold with respect to the other and a concave portion that is concave with respect to the other. Not. For example, as shown in FIG. 6, both the hole 36 and the hole 46 may have an elliptical shape.

  Further, as shown in FIG. 7A, the seal member 32 may have a portion that is concave with respect to the separator 40 and a protruding portion that protrudes in a mountain shape inside the manifold. As shown in FIG. 7B, the separator 40 has a portion that protrudes to the inside of the manifold with respect to the seal member 32, and a notch that becomes a recess inside the manifold with respect to the seal member 32. Also good.

  It is also conceivable to match the shapes of the hole 36 and the hole 46 so that the wall surface formed by the hole 36 and the hole 46 is a flat surface. However, since the member constituting the seal member 32 is rubber and the member constituting the separator 40 is metal, a difference occurs in the coefficient of thermal expansion. It is also conceivable that the sealing member 32 protrudes inside the manifold due to the fastening pressure. As a result, a step is generated on the wall surface formed by the hole 36 and the hole 46. Therefore, by providing the concave portion and the convex portion in advance as in the present embodiment, the discharge of the liquid water in the manifold can be promoted.

  In this embodiment, the fuel off-gas manifold is provided with the swirl flow generating means and the concavo-convex portion, but is not limited thereto. Discharge of liquid water can be promoted by providing the swirl flow generating means and the concavo-convex portion in the manifold in which liquid water may accumulate. For example, the swirl flow generating means and the concavo-convex portion may be provided in the oxidant off-gas manifold. However, in the fuel gas circulation-less system, since the flow rate of the fuel off gas is very small, liquid water tends to accumulate in the fuel off gas manifold. Therefore, in the fuel gas circulation-less system, it is preferable to provide the fuel off-gas manifold with the swirl flow generating means and the uneven portion.

It is a figure for demonstrating the fuel cell stack which concerns on 1st Example of this invention. 3 is a plan view of a membrane-electrode assembly with a seal member and a separator 40. FIG. It is a figure for demonstrating the detail of a fuel off gas manifold. It is a figure for demonstrating the detail of a fuel off gas manifold. It is a figure for demonstrating the relationship between the fuel off gas and liquid water in a fuel off gas manifold. It is a figure which shows the other shape of a hole. It is a figure which shows the other example of the shape of a sealing member and a separator.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Cell 30 Membrane-electrode assembly with seal member 31 Power generation unit 32 Seal member 40 Separator 50 Swirl flow generating means 100 Fuel cell stack

Claims (5)

A laminate in which membrane-electrode assemblies including a seal member and separators are alternately stacked, and an off-gas manifold penetrating the seal member and the separator in the stacking direction is formed;
A swirl flow generating means provided in the off gas manifold for generating a swirl flow in the gas flowing through the off gas manifold, and
One of the separator and the seal member adjacent to each other that constitutes the inner wall of the off-gas manifold includes a convex portion that is convex to the inside of the manifold with respect to the other, and a concave portion that is concave to the other. A fuel cell stack characterized by that.   2. The fuel cell stack according to claim 1, wherein the swirl flow generating means has a spiral fin shape.   The fuel cell stack according to claim 1, wherein the swirl flow generating means is a plurality of twisted wires.   4. The off-gas manifold according to claim 1, wherein one of the separator and the seal member has a substantially rectangular hole shape, and the other has an elliptical hole shape. Fuel cell stack.   The fuel cell stack according to any one of claims 1 to 4, wherein the off-gas manifold is a fuel gas off-gas manifold.

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