JPH03214568A - Reaction gas supply device of fuel cell - Google Patents

Abstract

PURPOSE:To improve poorly performed even distribution in reaction gas supply owing to the gravitation by inserting a fluid resistance, the value of which increases with rising level, into the inlet to a fuel supply manifold, and inserting a fluid resistance, the value of which increases with sinking level, into the inlet to an air supply manifold. CONSTITUTION:Fuel gas is supplied to unitary cells in stack, block by clock, from a fuel supply piping 2 through a fuel supply manifold 3. A fixed orifice 14 as a fluid resistance to adjust the rate of flow of the fuel gas flowing to the manifold 3 is installed in each divergent pipe 10 for connecting this piping 2 with each manifold 3, wherein the bore of orifice is reducing as going upward. A similar orifice 15 is provided in each divergent pipe 12 which connects an air supply piping 6 with an air supply manifold, and the bore of orifice is decreasing as going down. This improves poorly performed even distribution of reaction gas in the height direction of a cell stack.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to an apparatus for supplying reactive gases to a cell stack in a fuel cell that supplies reactive gases (fuel gas and air) to generate electricity through an electrochemical reaction.

[Conventional technology]

Figures 4 to 6 are schematic diagrams showing the reactant gas supply structure in a conventional fuel cell. Figure 4 is a plan view, Figure 5 is a cross-sectional view along the line ■-■, and Figure 6 is the same. < It is a cross-sectional view along the VI-VI line. In the figure, reference numeral 1 denotes a battery stack, which is composed of a large number of stacked rectangular cells in which a hydrogen electrode and an air electrode are arranged on both sides of a matrix containing an electrolyte. Reference numeral 2 denotes a fuel supply pipe that runs along the side of the battery stack 1, and a fuel gas containing hydrogen as a main component is supplied from the fuel supply pipe 2 to the battery stack 1 via a fuel supply manifold 3 as shown by the arrow. The fuel is supplied to the constituent unit cells, collected at the fuel discharge manifold 4 on the opposite side as shown by the arrow, and discharged from the fuel discharge pipe 5 to the next system. Similarly, air containing oxygen that reacts with the fuel gas is passed from the air supply pipe 6 vertically up along the side of the battery stack l, which is orthogonal to the side where the fuel supply pipe 2 is installed, to the air supply eyebrow holder. 7, collected by an air exhaust manifold 8 on the opposite side and discharged from an air exhaust line 9. In supplying such a reaction gas, for example, a distance of 2 to 3 m
It is necessary to evenly distribute the reactant gas to each of the multiple cells stacked at a height of . For this purpose, as shown in FIGS. 5 and 6, the battery stack 1 is divided into several blocks 1-1 to 1-N each containing, for example, 60 to 80 cells, and each block is supplied with fuel gas and air. Supply and discharge manifolds 3.4 and 7,8
is installed to equalize the supply of reaction gas. In addition,
Manifolds 3 and 4 and fuel gas pipes 2 and 5 are connected by branch pipes 10 and 11, respectively, and manifolds 7 and 8 and air pipes 6 and 9 are connected by branch pipes 12 and 1, respectively.
Connected by 3.

[Problem to be solved by the invention]

By the way, fuel gas is a mixture of 70-80% hydrogen and the rest mainly carbon dioxide, but since hydrogen is lighter than carbon dioxide, there is a difference in the concentration distribution of fuel gas as it flows through vertical pipes. The hydrogen concentration is higher at the top of the pipe and lower at the bottom. This causes poor uniform distribution, in which a large amount of hydrogen is distributed to the fuel supply manifold 3 that supplies fuel gas to the unit cells stacked at the top of the cell stack 1, while less hydrogen is distributed at the bottom. On the other hand, with regard to air, the molecular weights of the component gases are not as different as in fuel gas, and large imbalances do not occur. However, oxygen in the air is still heavier than nitrogen, which is the main component, and is poorly distributed in the upper air supply manifold 7. , the number of equal distribution defects increases in the lower part. Although there is a concentration difference in the reaction gas as it passes through pipe 2.6, the consumption of hydrogen and oxygen in each car battery is based on the power generation principle that the same current flows through the stacked single cells as a whole. Since the quantities are the same, it is possible to analyze their supply shortfalls by measuring the concentrations of hydrogen and oxygen in the fuel gas and air exhaust manifolds 4 and 8 (outlet concentrations). Figure 7 shows the results of such an analysis, and shows how the outlet concentrations of hydrogen and oxygen change with respect to the appropriate value of 100% in the height direction of the battery stack 1. It can be seen that the lower the position, the higher the concentration of oxygen. As a result, conventional power generation plants have had a problem in that it is difficult to obtain normal power generation even if a proper flow rate of reactant gas is supplied to the fuel cell main body. This invention was made in response to such a situation, and provides a reactant gas supply device for a fuel cell that improves power generation performance by correcting the imbalance of reactant gas supply based on gravity. The purpose is to

[Means to solve the problem]

In order to achieve the above object, the present invention divides a battery stack formed by stacking a large number of single cells into several blocks in the height direction, and installs a fuel supply manifold and an air supply manifold for each of these blocks. In a fuel cell in which fuel gas and air are supplied to the unit cell from fuel supply piping and air supply piping vertically raised through the fuel supply manifold, a fluid whose resistance increases as the height increases at the entrance of the fuel supply manifold. A resistor is inserted, and a fluid resistor is inserted at the inlet of the air supply manifold, with the resistance increasing as the height decreases.

[For use]

While the fuel gas ascends up the vertical fuel supply pipe and is distributed to each fuel supply manifold, hydrogen, the main component required for power generation, is carried to the upper part of the pipe because it is light. Since the branch pipes that guide this fuel gas from the piping to the manifold all have the same inner diameter, the higher the position of the manifold, the more hydrogen will be supplied. Therefore, a fluid resistance is inserted into the inlet of each manifold to suppress the flow of fuel gas, and the resistance increases as the height increases. As a result, the higher the hydrogen concentration of the fuel gas, the smaller the flow rate to the Mayufold, and the upper and lower hydrogen supply amounts can be balanced. Similarly, in the air supply piping, the concentration of heavy oxygen increases as it goes lower, but by inserting a fluid resistance at the inlet of the air supply manifold, the resistance of which increases as the height position decreases. It is possible to balance the supply amount up and down.

【Example】

1 and 2 show an embodiment of the present invention, FIG. 1 is a sectional view corresponding to FIG. 5 showing the fuel gas supply structure, and FIG. 2 is a sectional view showing the air supply structure. 6 is a sectional view corresponding to FIG. 6. FIG. Note that the same parts as in the conventional example are given the same reference numerals, and the description thereof will be omitted. First, in FIG. 1, a battery stack 1 is divided into several blocks 1-1 to 1-N, and fuel is supplied to each block from a vertically rising fuel supply pipe 2 to the stacked unit cells. Fuel gas is supplied via the manifold 3. Each branch pipe 10 connecting the pipe 2 and each manifold 3 is provided with an orifice 14 as a fluid resistance for adjusting the flow rate of fuel gas to the manifold 3. This orifice 14 is a fixed orifice whose inner diameter gradually decreases from bottom to top, and therefore its resistance increases as the height position increases. As a result, the flow rate of the fuel gas in the upper part of the pipe where the hydrogen concentration is higher is suppressed, and the amount of hydrogen supplied to each manifold 3 is distributed equally. Further, in FIG. 2, a similar orifice 15 is provided in each branch pipe 12 connecting the air supply pipe 6 and the air supply manifold 7, and the inner diameter of the orifice 15 becomes smaller sequentially from the top to the bottom. As a result, the flow rate of air in the lower part of the pipe where the oxygen concentration is higher is suppressed, and the amount of oxygen supplied to each manifold 7 is distributed equally. The inner diameter of each of the orifices 14 and 15 is set so that a standard flow rate of the reactant gas flows at the rated current, and FIG. This figure shows the results of measuring the concentration in the same manner as in the conventional example. Standard concentration of hydrogen is 100%
According to the actual measurement in the conventional example, the concentration was as high as 110% in the upper part (Fig. 7), but in the example, it was 102%, an improvement of 8%, and by that amount, the concentration in the lower part was 92%. 9
It has risen to 8%. Also, regarding the oxygen concentration, the concentration in the lower part decreases from 106% to 102%, and the concentration in the upper part decreases from 94% to 98%.
%.

【Effect of the invention】

According to this invention, with a simple configuration, the problem of uneven distribution of reactant gases in the height direction of a battery stack, which is caused by the weight difference between hydrogen in fuel gas, oxygen in air, and other component gases, is improved. As a result, power generation performance can be improved and battery life can be extended.

[BRIEF DESCRIPTION OF THE DRAWINGS] FIG. 1 is a vertical cross-sectional view showing a fuel gas supply configuration according to an embodiment of the present invention, FIG. 2 is a vertical cross-sectional view showing an air supply configuration,
Fig. 3 is a diagram showing the change in outlet concentration of reactant gas depending on the height of the battery stack in the example, Fig. 4 is a plan view of the conventional example, and Fig. 5 is a cross section along the line V1 in Fig. 4. 6 and 6 are cross-sectional views taken along the same <VI-■ line, and FIG. 7 is a diagram showing the change in outlet concentration of reactant gas depending on the height of the battery stack in the conventional example. 1...Battery stack, 2...Fuel supply piping, 3...
・Fuel supply manifold, 4...Fuel discharge manifold,
5...Fuel delivery pipe, 6...Air supply pipe, 7...
・Air supply manifold, 8... air discharge manifold,
9... Air discharge piping, 14.15... Orifice. l ■T+Golden red! Shin 1 Figure 1 ■ 1 ■ Chiku 4 Figure 5 Figure Gunbo

Claims (1)

[Claims] 1) A battery stack consisting of a large number of stacked single cells is divided into several blocks in the height direction, and fuel supply piping is installed vertically through fuel supply manifolds and air supply manifolds provided for each block. In a fuel cell in which fuel gas and air are supplied to the single cell from a fuel supply pipe and an air supply pipe, respectively, a fluid resistance whose resistance increases as the height increases is inserted into the inlet of the fuel supply manifold, and a fluid resistance whose resistance becomes larger as the height position increases, A reactant gas supply device for a fuel cell, characterized in that a fluid resistance whose resistance increases as the height position becomes lower is inserted into the inlet.