JP2021082486A - Fuel cell stack - Google Patents

Abstract

To suppress excessive inflow of liquid water to an inlet of each single cell in a fuel cell stack having a configuration in which both ends of a stack of a plurality of single cells in the stacking direction are sandwiched between a pair of end plates.SOLUTION: A fuel cell stack includes a laminate including a plurality of laminated single cells, and end plates arranged at both ends of the laminate and formed with flow paths for supplying fuel gas to the laminate, and the flow path includes a step between the end on the inflow side of the fuel gas and the end on the laminate side, and the inner diameter becomes smaller from the end on the inflow side of the fuel gas toward the step.SELECTED DRAWING: Figure 2

Description

The present disclosure relates to a fuel cell stack.

Inside the fuel cell stack, which has a structure in which both ends of a stack of a plurality of single cells in the stacking direction are sandwiched between a pair of terminals and a pair of end plates, reaction gas is supplied to each single cell and each single cell is supplied. A plurality of manifolds for discharging off-gas from the cells and supplying and discharging the cooling medium to each single cell are formed parallel to the stacking direction. At least one end plate is formed with a plurality of through holes so as to communicate with each manifold inside the fuel cell stack. The end plate described in Patent Document 1 is provided with a water pool in a through hole communicating with a manifold for supplying reaction gas to each single cell, and water generated by power generation of the fuel cell or fuel cell. The water remaining inside the fuel cell before startup is temporarily stored.

Japanese Unexamined Patent Publication No. 2003-178791

However, when the fuel cell stack described in Patent Document 1 is mounted on a vehicle, the fuel cell stack is mounted on the vehicle in a state of being tilted from the horizontal direction, or the fuel cell stack is tilted from the horizontal direction depending on the traveling condition of the vehicle. In some cases. In such a case, the water stored in the water reservoir may flow into the inlet of each single cell, and the water may flow excessively into each single cell.

The present disclosure can be realized in the following forms.

(1) According to one form of the present disclosure, a fuel cell stack is provided. The fuel cell stack includes a laminate including a plurality of stacked single cells, an end plate arranged at both ends of the laminate, and a flow path for supplying fuel gas to the laminate. The flow path has a step between the end on the inflow side of the fuel gas and the end on the laminated body side, and the inner diameter increases from the end on the inflow side of the fuel gas toward the step. It becomes smaller.
According to this form of the fuel cell stack, the flow path for supplying the fuel gas has a step between the end on the inflow side of the fuel gas and the end on the laminate side, and is on the inflow side of the fuel gas. Since the inner diameter decreases from the end toward the step, backflow can be generated at the step. Therefore, the liquid water flowing in the flow path is finely separated by the backflow vortex, so that the liquid water can be made into droplets. As a result, it is possible to prevent excessive inflow of liquid water into the inlet of the single cell.

The present disclosure can also be realized in various embodiments. For example, it can be realized in the form of a fuel cell system including a fuel cell stack, a vehicle equipped with such a fuel cell system, or the like.

An explanatory diagram showing a schematic configuration of a fuel cell system including a fuel cell stack according to an embodiment of the present disclosure. FIG. 5 is an enlarged cross-sectional view showing the configuration of the first end plate. Explanatory drawing for demonstrating the mechanism of dropletizing liquid water in a fuel gas flow path. Explanatory drawing which shows the relationship between the size of a step and the inflow amount of liquid water into a single cell.

A. Embodiment:
A1. Fuel cell system configuration:
FIG. 1 is an explanatory diagram showing a schematic configuration of a fuel cell system 100 including a fuel cell stack 30 according to an embodiment of the present disclosure. The fuel cell system 100 is mounted on the vehicle, for example, and outputs electric power that is a power source of the vehicle in response to a request from the driver. The fuel cell system 100 includes a fuel cell stack 30 and a fuel gas supply / discharge unit 50.

The fuel cell stack 30 includes a laminate 10, a first end plate 20, and a second end plate 21. The laminated body 10 is configured to include a plurality of single cells 11 laminated along the laminating direction. Specifically, the laminated body 10 includes a plurality of single cells 11, a terminal plate (not shown), and an insulator (not shown). Note that FIG. 1 shows a cross section of the fuel cell stack 30 along the stacking direction. In FIG. 1, the Z-axis is parallel to the vertical direction, and the X-axis and the Y-axis are parallel to the horizontal direction. The + Z direction corresponds to the vertical upper direction, and the −Z direction corresponds to the vertical lower direction. The stacking direction is parallel to the X-axis.

Each single cell 11 is a polymer electrolyte fuel cell, and is subjected to an electrochemical reaction using a reaction gas supplied to an anode-side catalyst electrode layer and a cathode-side catalyst electrode layer provided with a solid polymer electrolyte membrane interposed therebetween. Generates power. In each single cell 11, a gas diffusion layer formed of a carbon porous body such as carbon paper and carbon cloth is arranged outside the catalyst electrode layer of each electrode. Further, a conductive separator is arranged outside the gas diffusion layer of each pole. Inside the fuel cell stack 30, there are a plurality of manifolds for supplying reaction gas to each single cell 11, discharging off-gas from each single cell 11, and supplying and discharging a cooling medium to each single cell 11. , It is formed parallel to the stacking direction.

The first end plate 20 is located outside (+ X direction) in the stacking direction with respect to one end face of the two end faces in the stacking direction of the laminated body 10. Specifically, a terminal plate (not shown) is placed in contact with the end face of the single cell 11 on the + X direction side, and the first end plate 20 is placed outside the terminal plate in the stacking direction with an insulator (not shown) interposed therebetween. Is located in.

The first end plate 20 is a plate-shaped member, and is formed of, for example, an aluminum alloy. Instead of the aluminum alloy, it may be formed of a titanium alloy or any metal such as stainless steel. The plan view shape of the first end plate 20 is substantially rectangular, and its area is larger than the plan view shape area of the end face of the laminated body 10 in the stacking direction. The first end plate 20 is formed with a plurality of through holes penetrating in the thickness direction, in other words, in the stacking direction of the laminated body 10. These plurality of through holes function as a fluid flow path communicating with the plurality of manifolds formed inside the laminated body 10. Specifically, for discharging the fluid flow path (for example, the fuel gas flow path 25 described later) for supplying the reaction gas and the cooling medium to the laminate 10, and the off-gas and the cooling medium from the laminate 10. Functions as a fluid flow path.

The second end plate 21 is located on the outer side (−X direction) of the stacking direction with respect to the end face on the side opposite to the side on which the first end plate 20 is arranged, out of the two end faces in the stacking direction of the laminated body 10. To do.
Similar to the first end plate 20 described above, the terminal plate is arranged in contact with the other end surface of the single cell 11, and the second end plate 21 is located outside the terminal plate in the stacking direction with an insulator interposed therebetween. It is located in. The second end plate 21 has the same shape as the first end plate 20, and is made of the same material as the first end plate 20. The first end plate 20 and the second end plate 21 sandwich the laminated body 10 at a predetermined pressure and are fastened with bolts (not shown) to maintain the laminated state of the laminated body 10.

The fuel gas supply / discharge unit 50 supplies hydrogen gas as a fuel gas to the laminate 10 and discharges the fuel off gas from the laminate 10 to the outside. The fuel gas supply / discharge unit 50 includes a fuel gas pipe 51, a fuel gas tank 52, an on-off valve 53, a pressure regulating valve 54, an injector 55, a fuel off-gas pipe 61, a gas-liquid separator 62, and an exhaust / drain valve 63. A discharge pipe 64, a circulation pipe 65, and a hydrogen pump 66 are provided.

The fuel gas pipe 51 connects the fuel gas tank 52 and the fuel gas supply manifold formed inside the laminate 10, and supplies the hydrogen gas in the fuel gas tank 52 and the hydrogen gas sent from the hydrogen pump 66 to the laminate 10. To do. The on-off valve 53, the pressure regulating valve 54, and the injector 55 are arranged in the fuel gas pipe 51 from the fuel gas tank 52 toward the laminate 10 in this order. The on-off valve 53 controls the inflow of hydrogen gas from the fuel gas tank 52 to the injector 55. The pressure regulating valve 54 adjusts the pressure of the hydrogen gas supplied to the injector 55 to a predetermined pressure. The injector 55 supplies hydrogen gas to the laminate 10 and adjusts the supply amount thereof.

The fuel off-gas pipe 61 connects the fuel-off gas discharge manifold formed inside the laminate 10 to the gas-liquid separator 62. The fuel off-gas pipe 61 is a flow path for discharging the fuel-off gas from the laminated body 10. The fuel off gas includes hydrogen gas and nitrogen gas that were not used in the power generation reaction, and water produced by the power generation of the laminate 10. The fuel off gas pipe 61 guides the fuel off gas to the gas-liquid separator 62.

The gas-liquid separator 62 is connected between the fuel off-gas pipe 61 and the circulation pipe 65. The gas-liquid separator 62 separates the gas contained in the fuel-off gas in the fuel-off gas pipe 61 from the liquid water, and causes the gas containing hydrogen gas to flow into the circulation pipe 65. A part of the liquid water not separated by the gas-liquid separator 62 flows into the circulation pipe 65.

The exhaust drain valve 63 is an on-off valve provided in the lower part of the gas-liquid separator 62. The exhaust / drain valve 63 discharges the liquid water separated by the gas-liquid separator 62 and the impurity gas such as nitrogen gas contained in the fuel off gas to the discharge pipe 64. The discharge pipe 64 discharges the liquid water and the fuel off gas discharged from the exhaust drain valve 63 to the outside (in the atmosphere) of the fuel cell system 100.

The circulation pipe 65 is connected to the fuel gas pipe 51 on the downstream side of the injector 55. A hydrogen pump 66 is arranged in the circulation pipe 65. The hydrogen pump 66 sends the gas (gas containing hydrogen gas) separated by the gas-liquid separator 62 to the fuel gas pipe 51. In the fuel cell system 100, the gas containing the hydrogen gas contained in the fuel off gas is circulated and supplied to the laminate 10 again to improve the utilization efficiency of the hydrogen gas.

In addition to the above-described configuration, the fuel cell system 100 takes in air as an oxidant gas from the outside air and supplies it to the laminate 10, and discharges off-oxidation gas from the laminate 10 to the outside. Power to loads such as a cooling medium circulation unit that adjusts the temperature of the laminated body 10 by circulating a cooling medium in the body 10, a converter that boosts the voltage output from the laminated body 10, and a motor that generates power for the vehicle. A power control unit, a control device, and the like for controlling the supply of the fuel cell are provided, but the illustration and description are omitted because they are not essential in the description of the present embodiment.

A2. Detailed configuration of the first end plate:
FIG. 2 is an enlarged cross-sectional view showing the configuration of the first end plate 20. In FIG. 2, the end side of the fuel cell stack 30 shown in FIG. 1 in the + X direction is enlarged and shown. The first end plate 20 includes a fuel gas flow path 25. As described above, the fuel gas flow path 25 is a through hole formed along the thickness direction of the first end plate 20, in other words, the stacking direction of the laminated body 10. The fuel gas flow path 25 communicates with the fuel gas pipe 51 and the manifold formed in the laminate 10, and guides the fuel gas supplied from the fuel gas pipe 51 to each single cell 11. In FIG. 2, the flow of fuel gas is indicated by a broken line arrow.

In the present embodiment, the fuel gas flow path 25 is configured in its shape in order to droplet the liquid water flowing in with the fuel gas. Specifically, the fuel gas flow path 25 includes an end ES1 (the end in the + X direction of the first end plate 20) on the inflow side of the fuel gas and an end ES2 (the first end plate 20) on the laminated body 10 side. A step 26 is provided between the vehicle and the end portion in the −X direction. In the present embodiment, the size d1 (dimension in the Z-axis direction) of the step 26 is 0.5 mm. The step 26 may have an arbitrary size within the range of 0.5 mm or more and 1.0 mm or less instead of 0.5 mm.

The inner diameter of the fuel gas flow path 25 decreases from the end ES1 on the inflow side of the fuel gas toward the step 26. The fuel gas flow path 25 has the same inner diameter as the inner diameter of the end ES1 on the inflow side of the fuel gas from the step 26 to the end ES2 on the laminated body 10 side. Therefore, the fuel gas flow path 25 is formed in a tapered shape in which the inner diameter becomes smaller toward the laminated body 10 side from the end ES1 to the step 26, and is formed in a cylindrical shape in the step 26 to the end ES2. Has been done.

FIG. 3 is an explanatory diagram for explaining a mechanism for atomizing the liquid water in the fuel gas flow path 25. As shown in FIG. 3, the fuel gas that has flowed into the fuel gas flow path 25 flows toward the laminated body 10 side as shown by the solid arrow. In the vicinity of the center of the fuel gas flow path 25 in the Z-axis direction, the flow velocity of the fuel gas is larger and the inertia is larger than that in the vicinity of the inner wall of the fuel gas flow path 25, so that the fuel gas reaches the laminate 10 side. To do.

On the other hand, the liquid water Lw flowing into the fuel gas flow path 25 flows toward the laminated body 10 side while being pressed against the inner wall surface of the fuel gas flow path 25 by the pressure of the fuel gas. As described above, in the vicinity of the inner wall of the fuel gas flow path 25, the flow velocity is small and the inertia is also small, so that the flow velocity is further reduced. Therefore, the velocity gradient becomes 0 (zero) in the vicinity of the step 26, and so-called flow separation occurs on the downstream side (laminated body 10 side) of the step 26. Then, due to the separation of the flow, a backflow is generated and a vortex is generated, and the flow of the fuel gas is disturbed. At this time, the liquid water Lw in the vicinity of the step 26 is in a state of floating from the inner wall surface, and is finely separated by the backflow vortex generated by the separation of the flow to become a droplet Dr. Then, the droplet Dr flows toward the laminated body 10 side together with the fuel gas. Since the mass of the droplet Dr is smaller than the mass of the liquid water Lw due to the droplet formation, the droplet Dr is flowed to the downstream side in the stacking direction of the laminated body 10. Therefore, it is possible to prevent the liquid water from concentrating at the inlet of the laminated body 10 (near the end ES2). As a result, it is possible to prevent the liquid water from excessively flowing into the inlet of each single cell 11, so that it is possible to prevent the inlet of each single cell 11 from being blocked by the liquid water and the power generation efficiency of the single cell 11 from being lowered.

FIG. 4 is an explanatory diagram showing the relationship between the size d1 of the step 26 and the inflow amount of liquid water into the single cell 11. In FIG. 4, the horizontal axis represents the size d1 (mm) of the step 26, and the vertical axis represents the inflow amount (%) of liquid water into the single cell 11. The "inflow amount of liquid water into the single cell 11" is the liquid water into the single cell 11 when the amount of water that may flow into the single cell 11 during the power generation of the laminated body 10 is 100%. It means the amount of inflow and was calculated using fluid analysis software. In FIG. 4, assuming that the amount of water that may flow into the single cell 11 during the power generation of the laminated body 10 is 2.0 cc / sec as 100%, the water flows into the single cell 11 during the power generation of the laminated body 10. When the amount of water is 3.0 cc / sec, the amount of liquid water flowing into the single cell 11 is 150%, and the amount of water flowing into the single cell 11 during power generation of the laminate 10 is 1.0 cc / sec. In this case, the amount of liquid water flowing into the single cell 11 is 50%.

As shown in FIG. 4, as the size d1 of the step 26 increases, the amount of liquid water flowing into the single cell 11 decreases, and when the size d1 of the step 26 is 0.5 mm, the liquid water flows into the single cell 11. The inflow amount of the liquid water is 100% or less, and when the size d1 of the step 26 is 1.0 mm, the inflow amount of the liquid water into the single cell 11 is further smaller. Therefore, the size d1 of the step 26 is more preferably 0.5 mm or more and 1.0 or less.

According to the fuel cell stack 30 of the present embodiment having the above configuration, the fuel gas flow path 25 has a step 26 between the end ES1 on the inflow side of the fuel gas and the end ES2 on the laminate 10 side. However, since the inner diameter becomes smaller from the end ES1 on the inflow side of the fuel gas toward the step 26, a backflow can be generated at the step 26. Therefore, the liquid water Lw flowing in the fuel gas flow path 25 is finely separated by the backflow vortex, so that the liquid water Lw can be made into droplets. As a result, it is possible to prevent excessive inflow of liquid water into the inlet of the laminated body 10 (more specifically, the inlet of the single cell 11 in the vicinity of the end ES2). Therefore, it is possible to prevent the inlet of each single cell 11 from being blocked by the liquid water and the power generation efficiency of the single cell 11 from being lowered.

B. Other embodiments:
(1) The fuel gas flow path 25 has been used as a fuel gas flow path, but the present disclosure is not limited to this. For example, it may be used as a flow path of a cooling medium. Even in such a configuration, the same effect as that of the above-described embodiment can be obtained.

The present disclosure is not limited to the above-described embodiment, and can be realized by various configurations within a range not deviating from the gist thereof. For example, the technical features in the embodiments corresponding to the technical features in each form described in the column of the outline of the invention may be used to solve some or all of the above-mentioned problems, or one of the above-mentioned effects. It is possible to replace or combine as appropriate to achieve part or all. Further, if the technical feature is not described as essential in the present specification, it can be deleted as appropriate.

10 ... Laminate, 11 ... Single cell, 20 ... 1st end plate, 21 ... 2nd end plate, 25 ... Fuel gas flow path, 26 ... Step, 30 ... Fuel cell stack, 50 ... Fuel gas supply / discharge section, 51 ... Fuel gas pipe, 52 ... Fuel gas tank, 53 ... On-off valve, 54 ... Pressure regulating valve, 55 ... Injector, 61 ... Fuel off gas pipe, 62 ... Gas-liquid separator, 63 ... Exhaust drain valve, 64 ... Discharge pipe, 65 ... Circulation piping, 66 ... hydrogen pump, 100 ... fuel cell system, ES1 ... end, ES2 ... end, Dr ... droplet, Lw ... liquid water

Claims (1)

It ’s a fuel cell stack,
A laminated body containing a plurality of laminated single cells and
End plates arranged at both ends of the laminate and formed with flow paths for supplying fuel gas to the laminate.
With
The flow path is
There is a step between the end on the inflow side of the fuel gas and the end on the laminate side.
The inner diameter decreases from the end on the inflow side of the fuel gas toward the step.
Fuel cell stack.

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