JPS618853A - Layer-built fuel cell - Google Patents

Abstract

PURPOSE:To promote uniformity of electrochemical reaction precisely, by varying the flow rate distribution in perpendicular direction to the gas flow direction in the flow passage flux in gas flow. CONSTITUTION:Fuel gas enters a manifold 4a for fuel inlet/outlet at the inlet side and thereafter enters a cell, the flow rate distribution in perpendicular direction to the gas flow direction being varied by a baffle plate 6. The fuel gas getting into the cell returns in a fuel-return-manifold 4b, after contributing to electrochemical reaction in a region S1, and in turn, uniformly enters the cell. After the fuel gas contributes to electrochemical reaction in a region S2, it flows to the outlet side of the manifold 4a for fuel inlet/outlet and is exhausted outside of the system. On the other hand, oxidizer gas is distributed uniformly in the cell from an oxidizer inlet side manifold 15a and flows to an oxidizer outlet side manifold 15b and is exhausted outside of the system, after contributing to electrochemical reaction in the regions S2 and S1 respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a stacked fuel cell, and particularly aims to equalize surface pressure, temperature, and current distribution on a surface perpendicular to the stacking direction.

[Prior Art] - Figure 1 is a partially cutaway perspective view showing the interior of a conventional stacked fuel cell. ,(2
) is a gas separation plate that separates a fuel gas flow path (not shown) provided opposite to the fuel electrode from an oxidant gas flow path (not shown) provided opposite to the oxidizer electrode, and (3) is a single cell ( End plates (14a) l (141)) arranged above and below a laminate made by alternately laminating a plurality of 1) and gas separation plates (2),
(15a) and (15b) are arranged on the side surfaces of the laminate, respectively, and supply fuel and oxidant gas to fuel and oxidant gas channels (not shown) provided in the laminate.

(14a) is the fuel inlet side - = t = hold, (14b) is the fuel outlet side manifold, (15a) is the oxidizer inlet side manifold, (15
b) is the oxidizer outlet side manifold. In addition, arrow A
.

B indicates the direction in which the fuel and oxidizing gas flow, respectively.

Next, the operation will be explained. The fuel and oxidant gas supplied to the fuel and oxidant gas flow path through the fuel and oxidant inlet manifolds (14a) and (15a) diffuse into each porous electrode and undergo an electrochemical reaction. It contributes to the production of water and DC power.

Since the unit cells (1) are connected in series through the gas separation plate (2), the DC power generated at this time is transmitted through the end plate (3).
) is then led to an external electrical circuit. Incidentally, unreacted fuel and oxidizing gas that did not contribute to the reaction are discharged to the outside from the corresponding outlet manifolds (14b) and (15b), respectively.

l By the way, in conventional stacked fuel cells,
Since the fuel and oxidizer gas were flowing with a constant flow rate distribution, the fuel and oxidant gas were flowing at a part corresponding to the inlet side of the fuel and oxidizer gas and a part corresponding to the outlet side in the plane of the unit cell (1). Because gases with high partial pressures overlap with gases with low gas partial pressures, the amount of electrochemical reaction that depends on the gas partial pressure becomes extremely uneven within the cell (1) plane, resulting in electrical distribution and temperature distribution on 9 planes. The pressure distribution may be uneven. moreover,
In the stacked fuel cell, which is a stack of single cells (1), the uneven current, temperature, and surface pressure distributions overlap in the stacking direction, resulting in a synergistic effect, making it impossible to obtain stable battery characteristics. .

Figure 2 shows the results of simulating the above properties using a computer. The figure shows the current distribution within the plane of the single cell (1). a, b, c, a in the diagram
Vi corresponds to that in FIG.

In other words, in the part indicated by a in Fig. 1, the partial pressures of fuel and oxidant gas are both high, and the above electrochemical reaction is active, so the amount of electricity generated is large, the temperature is high, and the surface pressure is increased due to thermal expansion. The prices are also getting higher. , Current value at this part (1+nax) +3 compared to Id single cell average current value
It is 4 chi. In part a, where the surface pressure is high due to high temperature, the reaction becomes more active. On the other hand, in the part indicated by C, the partial pressures of fuel and oxidant gas are both low and the amount of reaction is small;
The amount of electricity generated is small, and the temperature per surface pressure is also low. The current value (min) in this part is 20% of that in 〒. Regarding the portions indicated by d and b, both the amount of power generation and the temperature per surface pressure are approximately between the two. The in-plane temperature distribution caused by the amount of power generated varies depending on the type of battery, load amount, gas utilization rate, etc., but using a phosphoric acid fuel cell as an example, the load is 200 mA/cm and the oxidizing agent is used. In-plane temperature difference △T (Tmax - Tm
1n) is approximately 14°C.

As described above, in conventional stacked fuel cells, the distribution of current, temperature, and surface pressure on the plane perpendicular to the stacking direction is non-uniform, and this non-uniformity has a synergistic effect in the stacking direction. However, there was a drawback that stable battery characteristics could not be obtained.

[Summary of the invention]

This invention was made in order to eliminate the drawbacks of the conventional ones as described above, and in order to uniformly perform the electrochemical reaction, the direction perpendicular to the direction of gas flow in the flow path bundle within the gas flow is It is an object of the present invention to provide a stacked fuel cell that can promote uniformity of the electrochemical reaction with high accuracy by changing the flow rate distribution.

(Embodiments of the invention) An embodiment of the present invention will be described below with reference to the drawings.

FIG. 3 is a partially cutaway perspective view showing the inside of a stacked fuel cell according to an embodiment of the present invention. In the figure, (4
a) C Fuel inlet and outlet manifold.

(4b) is a fuel return manifold, (6) is a fuel gas inlet, that is, a fuel inlet manifold (4a
) is a baffle plate with many holes (6FL) of varying density and size to change the distribution of flow path resistance, (7) is a fuel inlet and outlet manifold (4).
This is a partition plate that separates the fuel gases on the inlet side and the outlet side so that they do not mix in the interior of a). In addition, the baffle board (6)
The holes (6a) are larger and more densely opened closer to the oxidant gas outlet side.

FIG. 4 is an explanatory diagram showing the results of a computer simulation of the current distribution within the plane of the single cell (1) in the fuel cell according to the embodiment of the present invention shown in FIG.

In the figure, the broken line indicates the line separating the fuel gas inlet side and return side, and the area ratio is inlet side: return side - b: 3. In the following explanation, the area is 7. The side with an area of 3 is called a region S1, and the side with an area of 3 is called a region S2.

Note that the fuel gas flow paths in regions B1 and e2 each form one flow path bundle.

Next, the operation will be explained. The electrochemical reaction within the unit cell (1) and the method for guiding the generated current to an external electrical circuit are similar to those used in operating a conventional stacked fuel cell. In the following description, the manner in which fuel and oxidant gas flow will be mainly described. Manifold for fuel inlet and outlet for fuel gas! (4a) enters the inlet side, the flow rate distribution in the direction perpendicular to the flow direction of the p gas is changed by the baffle plate (6), and the p gas enters the pond 0 Ratio of flow rate distribution in the simulation shown in Figure 4 This is the case when the ratio of the smallest flow rate A1 near the oxidizer inlet side to the largest flow rate A2 that is close to the oxidizer outlet side is O or 8:1.2,
The total flow rate A is the same as when flowing uniformly. After the fuel gas that has entered the cell contributes to an electrochemical reaction within the region Sl, it returns within the fuel return manifold (4b) and then uniformly enters the cell. After contributing to the electrochemical reaction within region S2, it flows out to the exit side of the fuel inlet/outlet manifold (4a) and is discharged to the outside of the system. On the other hand, the oxidizing gas is uniformly distributed into the battery from the oxidizing agent inlet side manifold (llta), and after contributing to the electrochemical reactions in the areas 82 and 81, K flows out from the oxidizing agent outlet side manifold (15b) and outside the system. is discharged to.

According to this embodiment, the partial pressure of the fuel gas is high and the partial pressure of the oxidant gas is low in the region SI.
fllll+'/7d"T'J"l-+sei L? m
1Rtr*.

Therefore, the fuel gas on the oxidizer outlet side in region S1
The difference between the partial pressure 1 and the partial pressure of the fuel gas on the side closer to the oxidizing agent inlet side is increasing.In addition, in the region S2, the partial pressure of the fuel gas is low and the partial pressure of the oxidizing gas is high. The effect of this pressure distribution on battery characteristics is that when looking at the current value distribution, compared to the average value 〒, I max is +22%, 1 m1n is +18%, and the conventional type (+34%) shown in Fig.
, -20%), the reaction is more uniform. In addition, the in-plane temperature distribution due to the amount of power generation, taking a phosphoric acid fuel cell as an example, is a load of 200 mA/am and an oxidizer utilization rate of 50%.
, in-plane temperature difference ΔT (T
max - Tm1n ) is approximately 10°C, compared to the conventional type (approximately 14
℃）It can be seen that the mechanical properties are improved. As described above, by making the reaction uniform within the cell (1), the synergistic effect in the stacking direction of uneven distribution of current, etc., which was a drawback of the conventional type, is alleviated, and stable battery characteristics are achieved. can get.

In addition, in the above embodiment, a case where fuel gas is returned is shown as an example of a stacked fuel cell configured such that the flow directions of fuel and oxidant gas are perpendicular to each other within the cell reaction surface. The flow rate distribution of the fuel gas may be changed by a cross flow method, and the flow rate distribution of the oxidizing gas may be changed at the same time.

Furthermore, in the above embodiment, a case was explained in which the baffle plate (6) was used as a means for changing the gas flow rate distribution.
As shown in Figure 5, instead of the baffle plate (6), the cross-sectional area of the gas separation plate (2) (or the gas flow path (2a) provided in the electrode part of the unit cell (1)) is The gas flow rate distribution may be changed by changing the gas flow rate in a direction perpendicular to .

[7 Effects of the Invention] As described above, according to the present invention, the flow rate distribution in the direction perpendicular to the gas flow direction in the flow path bundle in the gas flow is changed so that the electrochemical reaction is performed uniformly. As a result, it is possible to promote the uniformity of the electrochemical reaction mentioned above with high accuracy, and as a result, it is possible to equalize the distribution of current, temperature, and surface pressure within the plane of the single cell, and to alleviate the synergistic effect in the stacking direction. This has the effect of providing stable battery characteristics.

[Brief explanation of the drawing]

Figure 1 is a partially cutaway perspective view showing the inside of a conventional stacked fuel cell, and Figure 2 is a calculator used to calculate the current distribution within the plane of a single cell in the conventional stacked fuel cell shown in Figure 1. FIG. 3 is a partially cutaway perspective view showing the inside of a stacked fuel cell according to an embodiment of the present invention, and FIG. An explanatory diagram showing the results of a computer simulation of the current distribution within a single cell plane in a stacked fuel cell according to an example, and FIG. 5 shows a part of a stacked fuel cell according to another embodiment of the present invention. FIG. In the figure, (1) is a single cell, (2) is a gas separation plate, (
2a) is a gas flow path, (4a), (4b), (14a
), (14b) is a fuel manifold, (15a),
(15b) is an oxidizer manifold, (6) is a baffle plate, (6a) is a hole, (7) is a partition plate, and arrows A and B indicate the flow directions of fuel and oxidizer, respectively. I Note that the same reference numerals in each figure indicate the same or corresponding parts.

Claims (3)

[Claims] (1) Single cell with an electrolyte matrix interposed between the fuel electrode and the oxidizer electrode, and gas separation that separates the fuel gas flow path facing the fuel electrode from the oxidizer gas flow path facing the oxidizer electrode. In a stacked fuel cell in which a plurality of plates are alternately stacked to form a laminate, a fuel gas and an oxidant gas are supplied to the fuel gas flow path and the oxidant gas flow path, respectively, and an electrochemical reaction is performed, A stacked fuel cell characterized in that the flow rate distribution in the direction perpendicular to the gas flow direction in the flow path bundle in the gas flow is changed so that the electrochemical reaction is performed uniformly. (2) The stacked fuel cell according to claim 1, wherein the means for changing the flow rate distribution is provided with a baffle plate that changes the distribution of flow path resistance at the inlet of the gas flow. (3) The laminated type according to claim 1, wherein the means for changing the flow rate distribution is one in which the cross-sectional area of each flow path in the flow path bundle is changed in a direction perpendicular to the gas flow direction. Fuel cell.