JPH01151163A - Fuel cell - Google Patents

Abstract

PURPOSE:To unify the flow of fuel gas in the lamination direction of a cell laminated body by decreasing the cross section area of the electrode substrate of a unit cell or the gas passage duct of a separator in stages from the lower section of the lamination height to the upper section. CONSTITUTION:The width size of a gas passage duct 17 is decreased and the width of a projection forming the wall of the duct 17 is increased at the upper position of a laminated body, thus the cross section area of the whole gas passage is decreased and the passage resistance is increased. The excessive flow of the fuel gas at the upper section of lamination is thereby prevented by the difference of aerial height in the lamination direction of a cell laminated body 9. The width size of the duct 17 is made larger then that of the upper duct and the passage resistance is decreased at the middle position of lamination of the laminated body 9. The width of the duct 17 is made larger than that at the middle position and the passage resistance is decreased at the lower section of lamination of the laminated body 9. The difference of aerial height in the lamination direction can be thereby compensated, and the fuel gas flow in the lamination direction can be unified.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is a method of forming a gas duct by alternately stacking unit cells and separators to supply fuel gas to the electrode base material of the unit cell or the separator in contact with the electrode. The present invention relates to a fuel cell equipped with a cell stack made of.

[Conventional technology]

A cell stack of a fuel cell is formed by alternately stacking unit cells and separators. The so-called ribbed electrode method and the ribbed separator method are known for the combination of a cell and a separator.

FIG. 3 is an exploded perspective view of the lip-equipped electrode system. In the figure, 1 is a matrix and a box, and a fuel electrode catalyst layer 2 and an oxidizer electrode catalyst layer 3 are placed between them, and the fuel electrode A gas permeable fuel electrode base material 4 is provided in close contact with the catalyst layer 2, while a gas permeable oxidant electrode base material 5 is provided in close contact with the oxidant electrode catalyst layer 3. The fuel electrode base material 4 is provided with a plurality of groove-shaped channels 4a for supplying fuel gas to the fuel electrode catalyst layer 2, while the oxidant electrode base material 5 is provided with a plurality of groove-like channels 4a for supplying fuel gas to the oxidant electrode catalyst layer 3. A plurality of groove-shaped channels 5a are provided perpendicularly to the channel 4a. The battery stack is formed by alternately stacking the above-mentioned unit cells and separator plates 6 as gas-impermeable separators.

In the ribbed separator method, as shown in the exploded perspective view of FIG. 4, a matrix and a matrix 1 are sandwiched, and a fuel electrode catalyst layer 2 and an oxidizer electrode catalyst layer 3 are arranged on both sides of the matrix, and a gas A lipped separator 7 is provided as an impermeable separator.

A plurality of groove-shaped channels 7a for supplying fuel gas to the fuel electrode catalyst layer 2 are provided on one side of the ribbed separator 7 so as to open to the fuel electrode catalyst layer 2. A plurality of groove-shaped flow passages 7b for supplying oxidant gas to the oxidant electrode catalyst layer 3 are provided on the surface thereof, so as to be perpendicular to the flow passages 7a and open to the oxidant electrode catalyst layer. The battery stack is formed by alternately stacking these unit cells and ribbed separators.

FIG. 5 is an exploded perspective view of a fuel cell composed of a battery stack as described above. In the figure, 9 is a battery stack, and a fuel gas supply manifold 10 and a fuel gas discharge manifold are arranged on opposite sides of the battery stack 9, respectively. A manifold 11 is attached to the battery stack 9 via a sealing material, while an oxidant gas supply manifold and a fertilization discharge manifold 13 are attached to the battery stack 9 via a sealant on the other opposing side. installed on. Fuel gas and oxidant gas are supplied to and discharged from the battery stack through these manifolds, causing an electrochemical reaction in the single cells in the battery stack to extract electricity.

By the way, there is a sixth channel in the flow path for the fuel gas and oxidant gas mentioned above.
What is shown in FIG. 7 and FIG. 7 is known. FIG. 6 is a cross-sectional view of the fuel gas flow path portion of the fuel cell shown in FIG. 5. The figure shows the fuel gas supply.

Discharge manifolds 10 and 11 are attached to opposite sides of the battery stack 9, and an unillustrated supply and discharge manifold for oxidizing gas is attached to the other opposite side (in the following drawings, this type of The same illustration method is used in the figures).

As explained in FIG. 4, the separate plate 7 is supplied with the first gas duct 15, which is a groove-shaped gas flow duct that supplies fuel gas to the fuel electrode catalyst layer 2, and the exhaust manifold 10.
, 11 are opened on both sides of the battery stack 9 to which a predetermined number of strips are provided. A predetermined number of groove-shaped second gas ducts 16 that communicate between these first gas ducts 15 and are orthogonal to the first gas ducts 15 are provided. With this structure, the fuel gas that has flowed into the supply manifold lO travels straight through the first gas duct, travels laterally through the second gas duct, and is collected in the exhaust manifold ()'11, from which it is discharged to the outside.

Although the ribbed separator type was described above, the fuel electrode base material 4 is also provided with a first gas duct and a second gas duct having the same configuration.

Note that the flow path for supplying the oxidizing gas to the oxidizing agent electrode catalyst layer is also provided with a first gas duct and a second gas duct on the arranging agent electrode base material or the separate plate, as described above, and the oxidizing gas is supplied to the oxidizing agent electrode catalyst layer. The oxidant gas is supplied to the oxidant electrode catalyst layer by flowing through the first gas duct and the second gas duct so as to be perpendicular to the gas.

However, since this type of fuel cell stacks a large number of single cells, the height of the cell stack becomes high.

Therefore, the reactive gas, especially the fuel gas, consists of hydrogen containing non-reactive components such as carbon dioxide gas as a reformed gas, so the fuel gas supplied to the battery stack is generated by consuming the hydrogen in the cell stack. The fuel gas discharged at the exit of the body has a higher proportion of components such as carbon dioxide, which is heavier than hydrogen. Therefore, the density of the fuel gas at the outlet of the battery stack is greater than that at the inlet. Therefore, the height of the fuel gas column at the inlet and outlet of the battery stack differs due to the above-mentioned density difference, and increases as it goes downwards in the battery stack.

Therefore, when fuel gas is introduced from the inlet at a relatively low pressure, the fuel gas becomes difficult to flow below the battery stack due to the large air column height at the gas passage outlet due to the difference in gas density, which increases the stack height. There is a problem that the fuel gas does not flow evenly in the horizontal direction.

As a means to solve these problems, the present applicant previously proposed, in Utility Application No. 58-92571, to form a battery into a multi-cell block, stack a large number of these blocks, and provide a manifold for each block. We are proposing a configuration that reduces the stacking height. However, with this configuration, the shape of the manifold becomes complicated and costs increase.

In addition, the fuel gas discharged from the fuel cell is fed back into the fuel cell using a blower, and the flow rate is increased together with the fuel gas from the reformer to increase the pressure loss and reduce the pressure at the inlet of the cell stack. A configuration is known in which the amount of fuel gas is increased to allow sufficient flow of fuel gas even below the battery stack. However, this configuration requires a circulation blower, which increases equipment costs and auxiliary power.

In addition, as shown in FIG. 8, a fuel gas supply manifold 1° and a discharge manifold 1] are provided next to each other on one side of the battery stack 9, and an intermediate manifold 14 is provided on the other side. By making a U-turn and flowing the fuel gas in the direction of the arrow, the length of the flow path is increased and the flow path resistance is increased, and the pressure of the fuel gas at the inlet of the cell stack is increased and the fuel gas is flowed downward into the cell stack. There is also a known configuration that allows fuel gas to flow. However, this configuration has a problem in that the gas flow is uneven in the plane of the battery due to uneven flow in the intermediate manifold.

Further, in Utility Application No. 60-87218, the present applicant proposed that a filling material be inserted into the gas flow path to close part of the gas flow path to increase the flow path resistance. There was a problem that the number of parts increased.

[Problem that the invention seeks to solve]

As mentioned above, this type of fuel cell has a large number of single cells stacked on top of each other, so the height of the cell stack becomes high.

Therefore, the fuel gas consists of hydrogen and other gases that contain non-reactive components such as carbon dioxide gas, so as the hydrogen is consumed in the single cell, the fuel gas discharged at the exit of the battery stack is heavier than hydrogen. The ratio of components such as carbon dioxide gas increases. Therefore, the height of the gas column at the inlet and outlet of the battery stack differs, and increases as it goes downwards in the battery stack.

Therefore, when fuel gas is fed from the inlet at a relatively low pressure, the fuel gas becomes difficult to flow below the AM stack due to the large air column height at the gas passage outlet due to the difference in gas density, and the AM height increases. There is a problem that the fuel gas does not flow evenly in the horizontal direction.

As a means to solve these problems,
In No. 92571, the shape of the manifold is complicated, and the above-described method of supplying fuel gas and fuel exhaust gas requires the addition of a circulation blower and an increase in the power of auxiliary equipment.
The above-mentioned method of providing an intermediate manifold and making a U-turn on the fuel gas has a problem of uneven flow of gas, and the above-mentioned Utility Model Application No. Shoin-87218 also has a problem of increasing the number of parts, which are fillers.

SUMMARY OF THE INVENTION In view of the above-mentioned points, an object of the present invention is to provide a fuel cell that can uniformly supply a fuel gas flow rate in a stacked cell stack direction with a simple structure.

[Means for solving problems]

In order to solve the above problems, according to the present invention, unit cells and separators are alternately stacked, and a plurality of gas flow ducts are formed in the electrode base material of the unit cell or the separator in contact with the unit cell. In a fuel cell equipped with a cell stack formed by the above, the cross-sectional area of the gas flow duct is gradually reduced from the bottom to the top of the stack height.

[Effect]

According to the present invention, in the battery stack, if the cross-sectional area of the gas flow duct for fuel gas is made smaller toward the top in the stacking direction, the flow path resistance can be increased at the top of the stack and reduced at the bottom. , it is possible to compensate for the difference in air column height in the stacking direction of the battery stack. That is, a part of the gas pressure applied to the upper part of the battery stack is distributed to the lower part of the stack, and it is possible to compensate for the decrease in the height of the air column in the upper part of the stack due to the difference in fuel gas density. In this way, the cross-sectional area of the gas flow duct is gradually reduced in the stacking direction to increase the flow resistance, thereby increasing the supply of fuel gas at the bottom of the battery stack. , it is possible to ensure that the required flow rate of fuel gas flows uniformly to all the single cells.

〔Example〕

The present invention will be described in detail below based on the drawings.

FIG. 1 is a sectional view of a fuel gas flow path portion of a fuel cell according to an embodiment of the present invention. Note that Figures 1 and 2 are from Figure 6.
Components that are the same as those in the conventional example shown in FIGS. 7 and 8 are given the same reference numerals. In FIG. 1, a second gas duct 16 opens into the fuel electrode catalyst layer of the separation plate 7 as a separator. Supply manifold 10. Discharge manifold 1
1 etc. configuration.

Since the operation is the same as that of the prior art, the explanation will be omitted. In this embodiment, as shown in FIG. 1, the middle dimension of the gas flow duct (first gas duct) 17 is reduced and the width of the convex portion forming the wall of the gas flow duct is widened. The cross-sectional area of the entire channel becomes smaller and the flow resistance becomes larger. This can prevent the fuel gas from flowing too much above the stack due to the difference in air column height in the stacking direction of the battery stack 9.

At the mid-stack position of the laminate, the width of the gas flow duct 17 is made larger than the width of the duct above the laminate to slightly reduce flow path resistance.

At the bottom of the stack, the width of the gas flow duct 17 is made larger than the width of the duct at the middle of the stack to further reduce the flow path resistance.

In this way, by decreasing the width of the gas duct toward the top of the stack, its cross-sectional area can be reduced, and the flow resistance of the gas passage can be increased at the top of the stack and gradually reduced below. Differences in air column height in the stacking direction of the battery stack can be compensated for. Note that in order to reduce the cross-sectional area of the gas flow duct, it is possible to change the height of the grooves provided in the electrode base material or the separator, but in this case it is not preferable because it will affect the thickness of the electrode base material or separator.

FIG. 2 shows a cross-sectional view of the gas flow duct taken along the line A-A of the gas passage in FIG. flow duct 1
The width dimension is smaller than the cross section of No. 5, clearly indicating a state where the cross-sectional area is reduced.

The cross-sectional area of the second gas duct) 16 may be uniform.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, the width of the gas flow duct in the fuel gas passage.

By simply manufacturing the gas flow duct with several different dimensions when manufacturing the electrode base material 4 or the separator 7, without increasing the number of parts by using a filler, The gas flow resistance is changed in the stacking direction of the battery stack so that it increases at the top and decreases at the bottom, and as the flow resistance increases at the top, the pressure of the fuel gas at the inlet of the battery stack increases. , the required flow rate of fuel gas can be made to flow by compensating for the difference in air column height due to the difference in density of fuel gas at the inlet and outlet of the battery stack, and the flow rate of fuel gas can be made uniform in the stacking direction. It has the effect of

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a fuel gas flow path portion of a fuel cell according to an embodiment of the present invention, and FIG. 2 is a cross-sectional view showing that the cross-sectional area of a gas flow duct according to an embodiment of the present invention is reduced. , Figure 3 is an exploded perspective view of a unit cell with lip-attached electrodes, Figure 4
The figure is an exploded perspective view of a cell with a ribbed separator type.
The figure is an exploded perspective view of a fuel cell! Figure 6 is a partial cross-sectional view of a single cell showing a conventional fuel gas flow path, Figure 7 is a cross-sectional view of a conventional gas duct, and Figure 8 is a partial cross-section of a fuel cell showing different conventional fuel gas flow paths. It is a diagram. 1.2.3, 4, 5... Cell, 6, 7... Separator, 9... Battery stack, 15... Conventional gas flow duct, 16... Second gas duct , 17... Gas flow duct according to the present invention. Figure 1 A-Aj Hokomen Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7

Claims (1)

[Claims] 1) A fuel cell comprising a battery stack in which unit cells and separators are alternately stacked and a plurality of gas flow ducts are formed on the electrode base material of the unit cells or the separator in contact with the unit cells, A fuel cell characterized in that the cross-sectional area of the gas flow duct is gradually reduced from the bottom to the top of the stack height.