JPH0650639B2 - Fuel cell - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a fuel cell.

[Conventional technology]

As described in JP-A-60-180066, a conventional fuel cell has a rib of a separator plate provided in parallel with a gas flow direction, and has a flow resistance in a direction orthogonal to the gas flow. It was uniform. However, in the cross-flow type gas flow pattern, the current density and the battery temperature change greatly depending on the combination of the flows of the fuel gas and the oxidant gas, so that a large current density and temperature distribution occur in the battery, and the battery performance, life, and There is a problem in terms of reliability. This large current density and temperature distribution is designed so that the gas flow path of the separator plate has a uniform flow resistance, so that the gas flow between the fuel gas and oxidant gas inlets and their respective outlets is high. It is caused by a large difference in fuel gas composition, utilization factor, gas temperature, etc. As described above, in the conventional fuel cell, no consideration has been given to the uniformity of the utilization rate, composition, and gas temperature of the fuel gas and the oxidant gas over the reaction surface of the cell.

[Problems to be solved by the invention]

The above-mentioned prior art does not consider the gas utilization rate, composition, gas temperature, etc. of the fuel gas and the oxidant gas over the entire reaction surface in the battery, and the power generation performance of the battery, high temperature part However, there were problems such as lifetime due to occurrence and reliability deterioration due to thermal stress due to temperature distribution.

The present invention has been made in view of the above points, and an object of the present invention is to provide a fuel cell capable of achieving uniform temperature distribution and current density distribution.

[Means for solving problems]

The above object is to provide a flow rate distribution control means for controlling the flow rate distribution of each gas in the flow direction of the fuel and the oxidant gas on the separator plate so that the temperature and current density distribution in the unit cell become uniform. Is achieved.

[Action]

If a flow rate distribution is given to the gas flowing in the unit cell in the flow direction, the cell performance changes due to the gas utilization rate and composition, that is, the gas flow rate on the fuel gas side, and the gas temperature change due to the gas flow rate on the oxidant gas side. The cell performance and temperature are uniform on the surface orthogonal to the gas flow direction in the cell. Therefore, even in a flow in which the composition of the fuel, the composition of the oxidant gas, the temperature, and the like differ in the gas flow direction, such as the cross-flow gas flow pattern, the utilization rate of the fuel gas, the composition, and the temperature of the oxidant gas are different. If the gas flow rate distribution is controlled so as to be uniform in the plane orthogonal to, the current density and temperature distribution will be uniform, and the performance, life and reliability will be improved.

〔Example〕

Hereinafter, the present invention will be described based on the illustrated embodiments. An embodiment of the present invention is shown in FIGS. As shown in the figure, a plurality of fuel cells are stacked with a separator plate 1 in between, and a unit cell (both not shown) having a pair of gas diffusion electrodes sandwiching an electrolyte plate between them is used for fuel and oxidation. It is provided with fuel and oxidant gas inlet / outlet manifolds 2, 3, 4, 5 for supplying / discharging the agent gas, respectively.
Fuel and oxidant gas flow paths are respectively formed between the separator plate 1 and the electrode plate via ribs 6 interposed therebetween, and the fuel gas flow path and the oxidant gas flow path are orthogonal to each other. It is arranged. In the fuel cell configured as described above, in the present embodiment, the flow rate distribution of the fuel and the oxidant gas 7, 8 in the flow direction of the gas 7, 8 is controlled in the separator plate 1 to control the temperature and current density in the unit cell. The flow rate distribution control means is provided so that By doing so, it is possible to obtain a fuel cell in which the temperature and the current density in the unit cell are made uniform and the temperature distribution and the current density distribution are made uniform.

That is, the oxidant gas 8 flows into the separator plate 1 from the oxidant gas inlet manifold 4, flows between the gas flow path and the rib 6 serving as a passage for the generated current, and generates electricity by an electrochemical reaction. At this time, the rib 6 is used for fuel, oxidant gas 7,
The oxidant gas 8 is provided at an angle with respect to the flow direction of the fuel gas outlet manifold 3 side so that the rib 6 of the fuel gas inlet manifold 2 has a larger angle. In the figure, 9 is a separator sealing surface. Oxidizer gas 8 in molten carbonate fuel cell
Is air and carbon dioxide gas, and oxygen and carbon dioxide gas in the air are consumed by an electrochemical reaction, and the concentration of oxygen and carbon dioxide gas becomes smaller as it flows downstream. However, changes in these concentrations do not affect the cell performance as much as changes in the hydrogen concentration on the fuel gas 7 side. However, since the oxidant gas flow rate is larger than the fuel gas flow rate, the influence on the cell temperature distribution is larger than that of the fuel gas. Therefore, the flow rate distribution of the oxidant gas 8 in the separator plate 1 has a great influence on the battery temperature distribution. Therefore, as shown in FIG. 1, the rib 6 is largely inclined with respect to the flow of the oxidant gas 8 on the fuel gas inlet side and is parallel to the flow of the oxidant gas 8 on the fuel gas outlet side. did. By doing so, the flow resistance of the gas flow path becomes large on the fuel gas inlet side and small on the fuel gas outlet side, and as shown in the figure, the flow rate Q _c of the oxidant gas is The flow rate distribution increases on the fuel gas outlet manifold 3 side.

As shown in FIG. 2, the fuel gas 7 has flowed from the fuel gas inlet manifold 2 into the separator channel, and the fuel gas 7 flows between the ribs 6 as in the case of the oxidant gas.
It flows out to the fuel gas outlet manifold 3. The composition of the fuel gas 7 is hydrogen and carbon dioxide, but the separator plate 1
Hydrogen is consumed as it flows through the interior of the reactor and generates electricity by an electrochemical reaction, and the concentrations of water and carbon dioxide, which are reaction product gases, increase. Therefore, the concentration of hydrogen, which is the fuel, decreases with the flow of the fuel gas 7, and the power generation output also decreases accordingly. Therefore, the inclination angle with respect to the flow direction of the ribs 6 of the fuel gas flow path is set to be large on the oxidant gas inlet side and small on the oxidant gas outlet side as in the case of the oxidant gas. By doing so, the flow resistance of the gas flow path increases on the oxidant gas inlet side, and as shown in the figure, the flow rate Q _A of the fuel gas 7 increases on the oxidant gas outlet manifold 5 side. Distribution. Due to this flow rate distribution, the output decrease on the oxidant gas outlet side is reduced, and the current density distribution becomes uniform.

The results obtained by comparing the dimensionless temperature distribution and the dimensionless current density distribution of the electrolyte plate with those of the conventional example in the above examples are shown in FIGS. 3 and 4. Dimensionless temperature As is apparent from FIG. 3 in which the change characteristics of (T _e : temperature of the electrolyte plate, T _gi : gas temperature at the inlet) are shown, the temperature distribution curve A of this embodiment shown by the dotted line is the conventional one shown by the solid line. As compared with the temperature distribution curve B in the example, it was confirmed that the entire temperature distribution, particularly the distribution in the flow direction of the oxidant gas, was almost flat and uniform. This is because the flow rate of the oxidant gas is low on the fuel gas inlet side and high on the fuel gas outlet side.

Dimensionless current density (J: current density at each place of the electrolyte plate, j _av : average current density of the electrolyte plate) As shown in FIG. 4 showing the change characteristics, the current of the present example shown by the dotted line The density distribution curve C has a lower current density on the oxidant gas inlet side than the current density distribution curve D of the conventional example shown by the solid line, and is almost flat and uniform with respect to the flow direction of the fuel gas. I was confirmed. This is because the fuel gas flow rate is low on the oxidant inlet side and the fuel gas flow rate is high on the oxidant gas outlet side.

As described above, according to this embodiment, the temperature distribution and the current density distribution of the battery become uniform, so that the life loss is reduced by reducing the amount of electrolyte loss due to the temperature decrease in the high temperature portion, and the performance is improved by uniforming the power generation output. Can be planned. Also, since the flow rate distribution in the gas flow direction inside the separator plate can be controlled arbitrarily, the oxidant gas flow rate can be increased to the high temperature part of the battery to lower the temperature, and the fuel gas flow amount can be increased to the low output part. It is possible to achieve high output.

〔The invention's effect〕

As described above, the present invention makes it possible to obtain a fuel cell in which the temperature distribution and the current density distribution of the fuel cell are uniform, and the temperature distribution and the current density distribution are uniform.

[Brief description of drawings]

FIG. 1 is a plan view showing an arrangement state of ribs forming a flow path of an oxidant gas in one embodiment of a fuel cell of the present invention, and FIG. 2 is a rib forming a flow path of a fuel gas in the same embodiment. FIG. 3 is a plan view showing an arrangement state of FIG. 3, FIG. 3 is a temperature distribution diagram of an embodiment of the fuel cell of the present invention and a conventional example, and FIG. 4 is a current density distribution diagram of the embodiment and a conventional example. 1 ... Separator plate, 2 ... Fuel gas inlet manifold, 3 ... Fuel gas outlet manifold, 4 ... Oxidizing gas inlet manifold, 5 ... Oxidizing gas outlet manifold, 6 ... Rib, 7 ... Fuel gas , 8 ... Oxidizer gas.

Claims (1)

[Claims] 1. A plurality of unit batteries, each of which has an electrolyte plate sandwiched between a pair of gas diffusion electrodes, are stacked with a separator plate in between. The separator plate and each of the gas diffusion electrodes are provided over the entire surface thereof. A fuel cell main body in which a fuel gas flow passage and an oxidant gas flow passage are respectively formed through a large number of ribs, and the fuel gas flow passage and the oxidant gas flow passage are arranged orthogonally, and the fuel cell main body A fuel cell comprising a fuel gas inlet / outlet manifold for supplying / discharging a fuel gas and an oxidant gas inlet / outlet manifold for supplying / discharging an oxidant gas, wherein the fuel gas is oxidized from the oxidant gas inlet manifold side in the fuel gas passage. The oxidant gas outlet manifold is inclined toward the agent gas outlet manifold side with respect to the flow direction of the fuel gas, and the sloping angle is made larger toward the oxidant gas inlet manifold side. A large number of ribs, which are set to become smaller toward the cold side, are interposed, and the flow of the oxidant gas flows in the oxidant gas flow path in such a direction as to guide the oxidant gas from the fuel gas inlet manifold side to the fuel gas outlet manifold side. A fuel cell comprising a large number of ribs which are inclined with respect to the direction and whose inclination angle is set to be larger on the fuel gas inlet manifold side and smaller on the fuel gas outlet manifold side.