JPS63119166A - Fuel battery - Google Patents

Abstract

PURPOSE:To improve reliability and performance of a fuel battery by increasing a cross-sectional area of fuel gas flow passage in a unit cell located at the lower part of layered stack. CONSTITUTION:The differential pressure of fuel gas fed to a fuel gas supply manifold 11 between outlet and inlet of a battery is large at the upper part but is small at the lower part of battery. By the arrangement that a layered group C 15 located at the lower part has a large cross-sectional area of fuel gas flow passage in a unit cell, the pressure loss is reduced and the fuel gas flows easily even if the differential pressure between outlet and inlet of the battery is small.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a fuel cell, and in particular to a fuel cell that improves uniform supply of fuel gas and oxidant gas to each cell in a laminated stack. Regarding fuel cells.

(Prior Art) Fuel cells are conventionally known as devices that directly convert chemical energy contained in fuel into electrical energy. This fuel cell usually has a pair of porous electrodes sandwiched between a matrix holding an electrolyte, a fuel gas such as hydrogen is brought into contact with the back of one electrode, and an oxidizing agent such as oxygen is brought into contact with the back of the other electrode. It is constructed by stacking a plurality of unit cells that output electrical energy from between the electrodes by bringing gas into contact and utilizing the electrochemical reaction that occurs at this time, and the fuel gas and oxidizing gas are Electrical energy can be extracted with high conversion efficiency as long as it is supplied.

FIGS. 4(A) and 4(B) show the configuration of this type of conventional fuel cell. That is, as shown in FIG. 4(A), a ribbed anode made of a porous body whose surface in contact with the matrix 1 is coated with a catalyst is placed on the upper side with a matrix 1 impregnated with an electrolyte sandwiched therebetween. An electrode 2 is disposed, and a ribbed cathode electrode 3 made of a porous material whose surface in contact with the matrix 1 is similarly coated with a catalyst is disposed on the lower side, thereby forming a unit cell 4. There is.

Furthermore, as shown in FIG. 4(B), in the conventional fuel cell, cooling plates 5 are installed at appropriate intervals between the stacked unit cells 4 to cool the heat generated during the power generation reaction. It has been inserted.

Further, the laminated cell 4 is sandwiched between the sealing conductor 6 at its upper and lower sides, and is tightened and fixed in the stacking direction by a fastening fitting 7 disposed below the sealing conductor 6, thereby forming a laminated stack.

On the other hand, a manifold 8 for supplying or discharging fuel gas or oxidant gas is attached to the side surface of the battery body formed in this manner.

Furthermore, a fuel gas or oxidant gas supply pipe 9 is attached to the manifold 8, and the fuel gas or oxidant gas supplied from the supply pipe 9 is supplied to each unit cell 4 of the stacked cells.

(Problems to be solved by the invention) The above-mentioned problems in conventional fuel cells are illustrated in Figure 3 (A
) and (B).

The fuel gas in the fuel gas supply manifold 11 supplied from the fuel gas supply port 10 has a high hydrogen concentration and therefore has a low density, but after passing through the stacked cells 4, hydrogen is consumed in the fuel gas exhaust manifold 12 and is replaced by hydrogen. The density increases due to the introduction of water vapor. As a result, the pressure distribution in the stack height direction is the hydrostatic pressure ρgh (ρ: density, g: gravitational acceleration, h: height) as shown in Figure 3 (B).
Due to this effect, the differential pressure between the battery inlet and outlet is large at the top of the battery and small at the bottom. For this reason, the flow rate of fuel gas flowing to the lower part of the battery is reduced.

As a result, sufficient fuel gas is not supplied to the lower cell of the stacked cell 4 during fuel cell operation, and the characteristics of the lower cell are significantly degraded. Furthermore, if only a smaller amount of fuel gas is supplied than the required flow rate, the cell will undergo a polarity reversal phenomenon, resulting in major problems such as damage to the battery body.

The present invention was made in view of the above circumstances, and provides a fuel cell that improves the reliability of the fuel cell and enables higher performance by uniformly supplying fuel gas to each cell of a stacked cell. The purpose is to provide.

[Structure of the invention]

(Means for Solving the Problems) In the fuel cell of the present invention, the cross-sectional area of the fuel gas flow passage of the unit cell located at the lower part of the stack is made larger than that of the unit cell at the upper part.

(Function) In the fuel cell of the present invention, by increasing the cross-sectional area of the fuel gas flow passage of the lower unit cell, the pressure drop of the fuel gas flow passage of the lower unit cell is reduced, and the lower cell = 4- is easily formed. By allowing the fuel gas to flow through the stacked cells, the fuel gas is uniformly supplied to each cell of the stacked cells.

〔Example〕

(Configuration of Example) In this example, as shown in FIG. 1, the unit cell 4 is
A fuel gas supply manifold 11 for supplying fuel gas to the anode electrode 2 is formed by stacking a plurality of layers and inserting cooling plates 5 at appropriate intervals to form a stack, and on one side of the stack. A fuel gas discharge manifold 12 for discharging fuel gas is installed on the opposing side.

Here, as shown in Figure 3 (B), the fuel gas at the cell inlet has a high hydrogen concentration and therefore has a low density, but at the cell outlet the hydrogen is consumed and water vapor is mixed in instead, so the density is low. increases, and the pressure distribution in the battery height direction is such that due to the effect of the hydrostatic pressure ρgh, the differential pressure between the battery inlet and outlet is large at the top of the battery and small at the bottom.

Therefore, as shown in FIG. 1, the laminated stack is configured to be divided into three or more groups having different cross-sectional areas of the fuel gas flow passages of the unit cells. At this time, the cross-sectional area of the cell fuel gas flow passages for the three groups is determined by taking into account the differential pressure between the cell inlet and outlet due to the pressure distribution along the cell height direction shown in Figure 3 (B), and the pressure drop in the fuel gas flow passages is , and is shaped to balance the differential pressure between the inlet and outlet.

In other words, as shown in FIG. 1(B), the laminated group located at the bottom has a larger cross-sectional area of the fuel gas flow passage. (Fuel gas flow passage cross-sectional area Group A <Group B <Group C) (Function of the embodiment) In the fuel cell of this embodiment having such a configuration,
Due to the effect of the hydrostatic pressure ρgh, the fuel gas sent to the fuel gas supply manifold has a differential pressure at the cell inlet and outlet, which is large at the top of the cell and small at the bottom.

At this time, the stacked group C15 located at the bottom has a large cross-sectional area of the unit cell fuel gas flow passage and a small pressure loss, so that even if the differential pressure between inlet and outlet of the cell is small, the fuel gas flows easily. As a result, fuel gas is uniformly supplied to each cell of the stacked cells.

〔Effect of the invention〕

As described above, by increasing the cross-sectional area of the cell fuel gas flow passages in the lower group of the laminated stack, fuel gas can easily flow to the lower cells, and fuel gas can be uniformly supplied to each cell in the laminated stack. This occurs during stacked cell operation. It is possible to prevent the lower cell characteristics from deteriorating due to fuel gas shortage, thereby increasing the reliability of the fuel cell and achieving higher performance.

(Other Examples) Note that the present invention is not limited to the above-mentioned Examples,
As shown in FIG. 2, a throttle 16 is provided at the inlet of the fuel gas flow path of the unit cell 4 to control the pressure drop in the fuel gas flow path.

In this case, by locating a cell with a small aperture 16 in the lower group of the laminated stack, the fuel gas can flow easily even if the differential pressure between the cell inlet and outlet is small, and the same effect as in this embodiment can be obtained.

[Brief explanation of the drawing]

FIG. 1(A) is a sectional view showing one embodiment of the fuel cell of the present invention, FIG. 1(B) is an enlarged view of the main part of FIG. 1(A), and FIG. 2 is a cross-sectional view showing an embodiment of the fuel cell of the present invention. An enlarged view of the main parts showing another embodiment, FIG. 3(A) is a sectional view showing the problems of the conventional fuel cell, and FIG. 3(B) shows the gas density difference between the inlet and outlet of the laminated stack. 4 (A> is a perspective view showing the structure of a unit cell, and FIG. 4 (B) is a sectional view showing the structure of a conventional fuel cell. 1... Matrix 2... Anode electrode 1 ．．
0...Fuel gas supply port 11...Fuel gas supply manifold 12...Fuel gas exhaust manifold Representative Patent attorney Nori Chika Ken Yudo Hirofumi Mitsumata Figure 1 (C) Figure 1 (B) Figure 2 Figure 3 (8) Third cause (A)

Claims (2)

[Claims] (1) A plurality of unit cells each consisting of a pair of anode and cathode electrodes each having a fuel gas flow path and an oxidant gas flow path and a matrix for holding an electrolyte are stacked, and an appropriate interval is set within the single cell. A cooling plate is inserted to form a laminated stack, and an oxidant gas supply manifold and a discharge manifold are respectively provided on opposite sides of the laminated stack for supplying or discharging the oxidant gas to the cathode electrode. In the fuel cell, a fuel gas supply manifold and a discharge manifold for supplying or discharging fuel gas to or from the anode electrode are arranged side by side on one side of the stack. 1. A fuel cell characterized in that the cross-sectional area of the fuel gas flow path of the unit cell located at the bottom is made larger than that of the unit cell located at the top. (2) The fuel cell according to claim 1, characterized in that a throttle is provided at the entrance of the fuel gas flow path of the unit cell to change the cross-sectional area.