JP7294239B2 - fuel cell system - Google Patents

Description

The disclosure herein relates to fuel cell systems.

US Pat. No. 6,200,009 discloses an air-cooled fuel cell separator plate having a heat-conducting structure to locally enhance the heat transfer of the airflow. The contents of the prior art documents are incorporated by reference as descriptions of technical elements in this specification.

Japanese Patent Publication No. 2017-510954

In a fuel cell, water vapor generated on the cathode side may move to the anode side by back diffusion. When the water vapor that has moved to the anode side is cooled and condensed, it becomes liquid water, which impedes the smooth flow of the fuel gas on the anode side. A fuel cell is in a state in which it cannot properly generate power unless it is properly supplied with fuel gas.

Movement of water vapor to the anode side due to reverse diffusion or the like can occur anywhere from upstream to downstream of the fuel gas flow. For this reason, a portion positioned downstream in the flow of the fuel gas tends to contain more water vapor and condense to generate liquid water. In view of the above, or in other aspects not mentioned, further improvements are desired in fuel cell systems.

One object of the disclosure is to provide a fuel cell system capable of stably generating power.

The fuel cell system disclosed herein comprises a fuel cell stack (31) having a plurality of fuel cells (11) for generating power through a chemical reaction between a fuel gas and an oxidant gas, and supplying fuel gas to the fuel cell stack. and an oxidant gas supply device (50) for supplying oxidant gas to the fuel cell stack and for cooling the fuel cell stack. A fuel inlet (32) for introducing fuel gas into the inside of the cell stack, a fuel outlet (33) for leading the fuel gas from the inside of the fuel cell stack, and a fuel in the fuel cell stack rather than the fuel outlet. A fuel upstream portion (31u), which is a portion close to the inlet portion, and a fuel downstream portion (31d), which is a portion closer to the fuel outlet portion than the fuel inlet portion in the fuel cell stack. It comprises a cathode separator (15, 615) forming a flow path for a chemical gas and an anode separator (16) forming a flow path for a fuel gas, the cathode separator forming part of the fuel downstream portion. and upstream cathode separators (15u, 615u) that form part of the fuel upstream section and have higher heat dissipation than the downstream cathode separators.

The disclosed fuel cell system includes an upstream cathode separator that is more heat dissipative than a downstream cathode separator. Therefore, the temperature of the fuel downstream portion having the downstream cathode separator can be maintained higher than the temperature of the fuel upstream portion having the upstream cathode separator. Therefore, in the downstream portion of the fuel, which tends to contain a large amount of water vapor, it is possible to prevent the water vapor from being condensed in the fuel gas flow path and generating liquid water. Therefore, it is possible to provide a fuel cell system capable of stably generating power.

The multiple aspects disclosed in this specification employ different technical means to achieve their respective objectives. Reference numerals in parentheses described in the claims and this section are intended to exemplify the correspondence with portions of the embodiments described later, and are not intended to limit the technical scope. Objects, features, and advantages disclosed in this specification will become clearer with reference to the following detailed description and accompanying drawings.

1 is a configuration diagram showing a fuel cell system; FIG. FIG. 4 is an explanatory diagram for explaining the supply of reaction gas to the fuel cell stack; 1 is an exploded perspective view showing a fuel cell; FIG. FIG. 3 is an enlarged perspective view showing a fuel cell in a fuel upstream portion; FIG. 3 is an enlarged perspective view showing a fuel cell in a fuel downstream portion; FIG. 3 is a cross-sectional view showing reactant gas flow paths inside the fuel cell stack; FIG. 11 is an enlarged perspective view showing a fuel cell in a fuel upstream portion in the second embodiment; FIG. 11 is an enlarged perspective view showing a fuel cell in a fuel upstream portion in a third embodiment; FIG. 11 is an enlarged perspective view showing a fuel cell in a fuel upstream portion in a fourth embodiment; FIG. 11 is an enlarged perspective view showing a fuel cell in a fuel upstream portion in a fifth embodiment; FIG. 11 is a cross-sectional view showing reaction gas flow paths inside a fuel cell stack in a sixth embodiment;

A number of embodiments will be described with reference to the drawings. In several embodiments, functionally and/or structurally corresponding and/or related parts may be labeled with the same reference numerals or reference numerals differing by one hundred or more places. For corresponding and/or associated parts, reference can be made to the description of other embodiments.

First Embodiment A fuel cell system 1 is a system that generates power through a chemical reaction between a fuel gas and an oxidant gas. The fuel cell system 1 is installed in, for example, a fuel cell hybrid vehicle (FCHV) to generate electric power to be supplied to a driving motor. Further, the fuel cell system 1 is a stationary fuel cell system, and simultaneously extracts electricity and heat to supply hot water, space heating, and the like.

In FIG. 1 , the fuel cell system 1 includes a fuel cell stack 31 , an oxidant gas supply device 50 and a fuel gas supply device 60 . The fuel cell stack 31 is a power generator that generates power through a chemical reaction between an oxidant gas and a fuel gas. The fuel cell stack 31 has a fuel inlet 32 for introducing fuel gas into the fuel cell stack 31 . The fuel cell stack 31 has a fuel outlet 33 for leading fuel gas from the fuel cell stack 31 to the outside.

A portion of the fuel cell stack 31 closer to the fuel inlet portion 32 than the fuel outlet portion 33 in the flow of the fuel gas is the fuel upstream portion 31u. On the other hand, in the fuel cell stack 31, the portion closer to the fuel outlet portion 33 than the fuel inlet portion 32 in the flow of fuel gas is the fuel downstream portion 31d. In other words, when the entire fuel cell stack 31 is bisected along the flow of the fuel gas, it is divided into a fuel upstream portion 31u including the fuel inlet portion 32 and a fuel downstream portion 31d including the fuel outlet portion 33. be done.

The oxidant gas supply device 50 has a supply function of supplying the fuel cell stack 31 with an oxidant gas for chemical reaction. In addition, the oxidant gas supply device 50 has an air-cooling function that lowers the temperature of the fuel cell stack 31 that is generating heat due to the chemical reaction. The oxidant gas supply device 50 includes a blower 51 and a guide member 52 . The blower 51 is a device for supplying air containing oxygen, which is an oxidant gas, to the fuel cell stack 31 . The blower 51 draws in air from the fuel cell stack 31 side and discharges air to the side opposite to the fuel cell stack 31 . The fuel cell system 1 is an air-cooled fuel cell system that does not have a water-cooling function for the fuel cell stack 31 but has an air-cooling function.

The blower 51 is provided facing the fuel cell stack 31 . The blower 51 includes an upstream blower 51u that blows air so as to pass through the fuel upstream portion 31u, and a downstream blower 51d that blows air so as to pass through the fuel downstream portion 31d. As the blower 51, an axial flow blower that blows air along the axial direction of the rotating shaft can be used. However, the blower 51 is not limited to the axial flow blower, and a centrifugal blower that blows air in the radial direction of the rotating shaft can also be used. Further, instead of the air blower 51 , a compressor may be used to supply compressed air to the fuel cell stack 31 .

The guide member 52 connects the blower 51 and the fuel cell stack 31 to form a channel for the oxidant gas. The guide member 52 guides the oxidant gas so that it flows throughout the fuel cell stack 31 and prevents the wind from flowing without passing through the fuel cell stack 31 . The guide member 52 is formed such that the air passage gradually narrows from the fuel cell stack 31 toward the blower 51 .

The fuel gas supply device 60 includes a fuel gas tank 61 , a supply valve 62 and a discharge valve 63 . The fuel gas tank 61 is a tank that stores hydrogen gas, which is fuel gas, in a high pressure state. The fuel gas tank 61 may be composed of a plurality of tanks. According to this, even when one tank becomes empty, the supply of fuel gas can be continued from the other tanks.

A fuel gas pipe connecting the fuel gas tank 61 and the fuel cell stack 31 is provided with a supply valve 62 . The supply valve 62 is a valve device for adjusting the amount of fuel gas supplied from the fuel gas tank 61 to the fuel cell stack 31 . The fuel gas is supplied to the fuel cell stack 31 by opening the supply valve 62 , and the supply of fuel gas to the fuel cell stack 31 is stopped by closing the supply valve 62 . The supply valve 62 is an electromagnetic valve whose opening can be electrically controlled. However, the supply valve 62 may be configured by a valve device other than the solenoid valve.

A fuel gas pipe connecting the fuel cell stack 31 and the outside is provided with a discharge valve 63 . The exhaust valve 63 is a valve device that adjusts the amount of exhaust gas, such as fuel gas that has not been used for reaction in the fuel cell stack 31 , to be discharged from the fuel cell stack 31 to the outside. Here, the exhaust gas includes gases other than the unreacted fuel gas. For example, the exhaust gas contains water vapor as water generated by the chemical reaction in the fuel cell stack 31 . For example, the exhaust gas includes air that is supplied to the fuel cell stack 31 as an oxidant gas and partially leaks to the fuel gas side. The exhaust gas is discharged from the fuel cell stack 31 by opening the exhaust valve 63 , and the exhaust gas from the fuel cell stack 31 is stopped by closing the exhaust valve 63 . The discharge valve 63 is an electromagnetic valve whose opening can be electrically controlled. However, the discharge valve 63 may be configured by a valve device other than the solenoid valve.

When generating power in the fuel cell stack 31 , the supply valve 62 is opened to supply fuel gas to the fuel cell stack 31 . Further, the exhaust valve 63 is kept closed until the supplied fuel gas is consumed, and when the consumption of the fuel gas is completed, the exhaust valve 63 is opened to exhaust the exhaust gas. By discharging the exhaust gas, fuel gas is newly supplied to the fuel cell stack 31 . However, the exhaust gas containing the unreacted fuel gas may be discharged with the exhaust valve 63 always open.

Instead of discharging the unreacted fuel gas that has flowed through the fuel cell stack 31 as it is, the configuration may be such that the unreacted fuel gas flows back into the fuel cell stack 31 . According to this, unreacted fuel gas can be recycled to the fuel cell stack 31 and used for the chemical reaction. Therefore, the amount of unreacted fuel gas discharged can be reduced, and the fuel gas can be efficiently used for power generation. However, the overall size of the fuel cell system 1 tends to increase due to the addition of the configuration for recirculating the fuel gas. In other words, by not providing a configuration for recirculating the fuel gas, it is easy to design the overall size of the fuel cell system 1 to be small. For this reason, it is preferable to select whether or not to employ a configuration that recirculates the fuel gas, taking into consideration the application, usage environment, and the like of the fuel cell system 1 .

The fuel cell system 1 includes a load 81 , a secondary battery 82 and a controller 90 . The load 81 is a device that consumes power generated by the fuel cell stack 31 . The load 81 is, for example, a running motor used for running the vehicle. A load 81 is, for example, a heater device used for supplying hot water. The secondary battery 82 is a device that stores power generated by the fuel cell stack 31 . The power stored in the secondary battery 82 may be used to drive the load 81 . The control unit 90 controls the driving of various devices that make up the fuel cell system 1 and controls the power generation of the fuel cell stack 31 .

In FIG. 2, the upstream fan 51u and the downstream fan 51d are provided adjacent to each other. Both the upstream fan 51u and the downstream fan 51d are axial fans. The rotating shaft of the upstream blower 51u faces the fuel upstream portion 31u. The rotating shaft of the downstream blower 51d faces the fuel downstream portion 31d.

The fuel cell stack 31 is configured by stacking a plurality of fuel cells 11 . The stacking direction of the fuel cells 11 is the Z direction. Here, the Z direction is the vertical direction, and both end surfaces of the fuel cell stack 31 in the Z direction correspond to the upper surface and the lower surface of the fuel cell stack 31 . However, the stacking direction of the fuel cells 11 is not limited to the vertical direction. The blower 51 blows air in a direction crossing the stacking direction of the fuel cells 11 . The blowing direction of the blower 51 is the X direction. Here, the X direction coincides with the axial direction of the rotating shaft of the blower 51 . The direction perpendicular to the two directions, the X direction and the Z direction, is the Y direction.

The fuel inlet portion 32 is provided on the bottom surface of the fuel cell stack 31 . Therefore, the fuel gas is introduced into the fuel cell stack 31 along the stacking direction of the fuel cells 11 . The fuel outlet portion 33 is provided on the bottom surface of the fuel cell stack 31 . Therefore, the fuel gas is led out from inside the fuel cell stack 31 along the stacking direction of the fuel cells 11 .

In FIG. 3, the fuel cell 11 includes a membrane electrode assembly 12, an oxidizing gas diffusion layer 14a, a fuel gas diffusion layer 14b, a cathode separator 15 and an anode separator 16. As shown in FIG. The membrane electrode assembly 12 is an assembly configured by arranging an anode electrode on one surface of an electrolyte membrane and arranging a cathode electrode on the other surface thereof. The anode electrode and the cathode electrode are configured by supporting a catalyst such as platinum on a carrier such as carbon. The membrane electrode assembly 12 is also called MEA.

Each fuel cell 11 is supplied with hydrogen gas functioning as a fuel gas and oxygen-containing air functioning as an oxidant gas, thereby outputting electrical energy. More specifically, on the anode side, a reaction is induced that converts hydrogen into hydrogen ions and electrons. On the other hand, on the cathode side, hydrogen ions, electrons, and oxygen react with each other to produce water.

The oxidizing gas diffusion layer 14a and the fuel gas diffusion layer 14b have a function of diffusing reaction gases such as oxidizing gas and fuel gas. The oxidant gas diffusion layer 14a and the fuel gas diffusion layer 14b are made of a porous member having gas permeability and electron conductivity.

The cathode separator 15 and the anode separator 16 are made of, for example, a conductive material such as metal or carbon. The cathode separator 15 forms a channel through which the oxidant gas flows. In the cathode separator 15, the direction of flow of the oxidant gas is the X direction. The anode separator 16 forms a channel through which the fuel gas flows. In the anode separator 16, the fuel gas flows in the Y direction. The oxidant gas diffusion layer 14 a is positioned between the cathode separator 15 and the membrane electrode assembly 12 . The fuel gas diffusion layer 14 b is positioned between the anode separator 16 and the membrane electrode assembly 12 .

The membrane electrode assembly 12 has a manifold 19 through which the fuel gas can flow outside the portion functioning as a reaction surface where a chemical reaction occurs. The oxidant gas diffusion layer 14a and the fuel gas diffusion layer 14b are provided with a manifold 19 through which the fuel gas can flow outside the portion functioning as the diffusion layer. The cathode separator 15 has a manifold 19 through which the fuel gas can flow outside the portion forming the flow path for the oxidant gas. The anode separator 16 is provided with a manifold 19 through which the fuel gas can flow in the Z direction, which is the direction in which the fuel cells 11 are stacked, at the end of the portion forming the flow path through which the fuel gas flows.

The manifold 19 includes an upstream manifold 19u through which the fuel gas immediately after being introduced from the fuel inlet portion 32 flows. The manifold 19 includes a downstream manifold 19d through which the fuel gas immediately before being led out from the fuel outlet portion 33 flows. The manifold 19 allows the fuel gas to pass through the plurality of fuel cells 11 and flow to the fuel gas flow path formed in the anode separator 16 .

The cathode separator 15 includes an upstream cathode separator 15u and a downstream cathode separator 15d. The upstream cathode separator 15u is a portion of the cathode separator 15 that constitutes the fuel upstream portion 31u. The downstream cathode separator 15d is a portion of the cathode separator 15 that constitutes the fuel downstream portion 31d.

In FIG. 4, the cathode separator 15 is a corrugated plate member. The cathode separator 15 has two types of flow passages, a reaction flow passage portion 15r and a cooling flow passage portion 15c, as flow passages for the oxidant gas. The reaction channel portion 15r is a channel portion that is open on the oxidant gas diffusion layer 14a side. The oxidant gas flowing through the reaction flow channel portion 15r flows into the oxidant gas diffusion layer 14a and is used for the chemical reaction. On the other hand, the cooling channel portion 15c is a channel portion whose side opposite to the oxidant gas diffusion layer 14a is open. The oxidant gas flowing through the cooling channel portion 15c cannot flow into the oxidant gas diffusion layer 14a. However, the oxidant gas passes through the fuel cells 11 in the X direction. Therefore, it greatly contributes to the cooling of the fuel cells 11 . The reaction channel portions 15r and the cooling channel portions 15c are arranged alternately in the Y direction.

In the upstream cathode separator 15u, the cooling channel portion 15c is provided with heat radiation fins 55f as the heat radiation promoting portion 55. As shown in FIG. The heat dissipation promotion part 55 is a part that contributes to improvement of heat dissipation performance. The radiation fins 55f are provided so as to protrude in the Z direction from the upstream cathode separator 15u. The radiation fin 55f has a plate shape with the X direction as the longitudinal direction. The amount of protrusion of the heat radiation fins 55f from the upstream cathode separator 15u is smaller than the height of the upstream cathode separator 15u. In other words, the Z-direction size of the radiation fins 55f is smaller than the Z-direction size of the upstream cathode separator 15u. Therefore, when the fuel cells 11 are stacked, the Z-direction ends of the heat radiation fins 55f do not contact the adjacent fuel cells 11 . Therefore, the oxidant gas can pass through the gaps between the heat radiation fins 55f and the adjacent fuel cells 11 .

The size of the radiation fins 55f in the Z direction is at least half the size of the upstream cathode separator 15u in the Z direction. The heat radiating fins 55f are provided substantially in the center of the cooling channel portion 15c in the Y direction. The radiating fins 55f are provided continuously from the starting end, which is the most upstream portion of the flow of the oxidizing gas in the cooling channel portion 15c, to the terminal end, which is the most downstream portion.

By providing the heat radiation fins 55f on the upstream cathode separator 15u, it is possible to ensure a large surface area where the oxidant gas and the upstream cathode separator 15u come into contact. The larger the radiation fins 55f are, the larger the surface area of contact between the oxidant gas and the upstream cathode separator 15u can be secured. A plurality of heat radiation fins 55f may be provided in one cooling channel portion 15c.

In FIG. 5, the downstream cathode separator 15d is not provided with a structure corresponding to the heat dissipation promoting portion 55. As shown in FIG. Therefore, the downstream cathode separator 15d has a smaller surface area in contact with the oxidant gas and has lower heat dissipation than the upstream cathode separator 15u.

In FIG. 6, since the fuel cells 11 are stacked in the Z direction, the cathode separators 15 and the anode separators 16 are alternately arranged in the Z direction. Here, the illustration of the membrane electrode assembly 12, the oxidant gas diffusion layer 14a, and the fuel gas diffusion layer 14b that constitute the fuel cell 11 is omitted.

The radiation fins 55f are provided for each of the plurality of cooling channel portions 15c. The cooling channel portions 15c and the reaction channel portions 15r are alternately formed in the Y direction. Therefore, in the upstream cathode separator 15u, the channel portions having the radiating fins 55f and the channel portions not having the radiating fins 55f are alternately formed. On the other hand, the downstream cathode separator 15d is not provided with the radiation fins 55f.

Stagnant water W may exist inside the anode separator 16 . The reason why the stagnant water W is generated will be described below. In the chemical reaction of the fuel cell 11, water is produced on the cathode side. Furthermore, when air is supplied as the oxidant gas, the supplied air contains moisture. In this way, during the power generation of the fuel cell stack 31, water is present on the cathode separator 15 side. In addition, the membrane electrode assembly 12 generates heat as the fuel cell stack 31 generates power. Therefore, moisture present on the side of the cathode separator 15 is likely to be heated by the membrane electrode assembly 12 and become water vapor.

The electrolyte membrane that constitutes the membrane electrode assembly 12 is a membrane that permeates not only hydrogen ions but also water vapor. Therefore, in the membrane electrode assembly 12, water vapor existing on the cathode side permeates the membrane electrode assembly 12 and moves to the anode side. The phenomenon in which water vapor moves from the cathode side to the anode side is called back diffusion. The water vapor that has moved to the anode side is cooled and condensed on the surface of the anode separator 16 . This condensed water stays on the surface of the anode separator 16 and becomes stagnant water W. As shown in FIG. Reverse diffusion is more likely to occur as the thickness of the electrolyte membrane of the membrane electrode assembly 12 is thinner.

Further, in the fuel cell 11, part of the oxidant gas flowing on the cathode side may leak to the anode side. Therefore, the fuel gas flowing on the cathode side is mixed with a part of the oxidant gas. When air is supplied as the oxidant gas, the fuel gas is mixed with nitrogen, water, and the like leaked from the cathode side. This water leaking from the cathode side can also condense on the surface of the anode separator 16 to become stagnant water W, like the water vapor that has permeated the membrane electrode assembly 12 .

The reverse diffusion of water vapor generated on the cathode side to the anode side and the phenomenon that a part of the oxidant gas leaks from the cathode side to the anode side may occur throughout the fuel cell 11 . Therefore, in the flow of the fuel gas, the more downstream the fuel gas is located, the more likely it is to be mixed with water. Therefore, in the flow of the fuel gas flowing through the fuel cell 11, stagnant water W tends to occur more downstream, and the amount of stagnant water W tends to increase.

The stagnant water W narrows the flow path of the fuel gas in the anode separator 16 and increases the pressure loss. In other words, the existence of the stagnant water W makes it difficult for the fuel gas to properly flow through the anode separator 16 . Therefore, among the plurality of channel portions formed in the anode separator 16, the channel portion in which the stagnant water W exists has a smaller amount of fuel gas flowing than the channel portion in which the stagnant water W does not exist. Therefore, the fuel gas required for proper power generation cannot be supplied, and the amount of power generated by the fuel cell 11 is reduced. In this way, depending on the presence or absence of stagnant water W and the amount of stagnant water W in each fuel cell 11, the power generation amount of each fuel cell 11 varies, and the power generation amount of the fuel cell stack 31 as a whole decreases.

The reason why the influence of the stagnant water W can be suppressed in the fuel cell system 1 will be described below. As for the cathode separators 15, the upstream cathode separator 15u has higher heat dissipation than the downstream cathode separator 15d. In other words, the downstream cathode separator 15d has a lower heat dissipation property than the upstream cathode separator 15u, and is likely to have a higher temperature due to heat generation accompanying power generation. Therefore, the temperature of the fuel downstream portion 31d including the downstream cathode separator 15d tends to be higher than the temperature of the fuel upstream portion 31u including the upstream cathode separator 15u. The stagnant water W is generated by condensation of water vapor. Therefore, in the fuel downstream portion 31d having a high temperature, water vapor is less likely to be condensed, and stagnant water W is less likely to be generated. Further, in the fuel downstream portion 31d having a high temperature, it is easy to evaporate the generated stagnant water W, and this is one of the reasons why the influence of the stagnant water W can be suppressed.

According to the embodiment described above, the fuel cell system 1 includes the downstream cathode separator 15d and the upstream cathode separator 15u having higher heat dissipation than the downstream cathode separator 15d. Therefore, it is easy to keep the temperature of the fuel downstream portion 31d, which tends to contain a large amount of water vapor in the fuel gas, higher than the temperature of the fuel upstream portion 31u. Therefore, it is easy to prevent water vapor from being cooled and condensed in the fuel gas flow path of the fuel downstream portion 31d. Therefore, the condensed stagnant water W is less likely to hinder the smooth flow of the fuel gas, and it is easy to maintain an appropriate supply of the fuel gas. As described above, it is possible to provide the fuel cell system 1 capable of stably generating power.

The oxidant gas channel in the upstream cathode separator 15u has a larger surface area in contact with the oxidant gas than the oxidant gas channel in the downstream cathode separator 15d. Therefore, with a simple structure, the heat dissipation property of the upstream cathode separator 15u can be improved compared to the downstream cathode separator 15d.

The cathode separator 15 includes a heat dissipation promoting portion 55 provided in the flow path of the oxidant gas. Therefore, the heat dissipation property of the cathode separator 15 can be easily changed by appropriately adjusting the shape and arrangement of the heat dissipation promoting portion 55 .

The heat dissipation promoting portion 55 is provided on the upstream cathode separator 15u, and is not provided on the downstream cathode separator 15d. Therefore, it is easier to ensure a large temperature difference between the fuel upstream portion 31u and the fuel downstream portion 31d compared to the case where the heat dissipation promoting portion 55 is also provided in the downstream cathode separator 15d. Here, if the temperature difference between the fuel upstream portion 31u and the fuel downstream portion 31d is too small, the target temperature of the fuel upstream portion 31u and the target temperature of the fuel downstream portion 31d may not be compatible. Therefore, ensuring a large temperature difference between the fuel upstream portion 31u and the fuel downstream portion 31d is important for appropriately maintaining power generation in each of the fuel upstream portion 31u and the fuel downstream portion 31d.

The heat dissipation promoting portion 55 is a heat dissipation fin 55 f protruding from the cathode separator 15 . Therefore, the surface area in contact with the oxidant gas can be easily increased compared to the portion where the radiation fins 55f are not provided. In particular, the radiating fins 55f are configured to stably and easily exhibit high heat radiation even when the flow velocity of the oxidant gas is slow.

More heat dissipation promoting portions 55 are provided in the cooling channel portion 15c than in the reaction channel portion 15r. Therefore, it is easy to prevent a situation in which a large number of heat dissipation promoting portions 55 are provided in the reaction use channel portion 15r, resulting in a shortage of the oxidant gas necessary for the chemical reaction. Therefore, the supply of the oxidant gas for chemical reaction to the fuel cell stack 31 can be stably maintained, and the temperature of the fuel upstream portion 31u can be easily lowered appropriately. Here, in the case where the heat dissipation promoting portion 55 is provided in the reaction flow path portion 15r, it is preferable to have a shape and arrangement that can stably maintain the supply of the oxidant gas for the chemical reaction.

The heat dissipation promoting portion 55 is provided in the cooling channel portion 15c and is not provided in the reaction channel portion 15r. Therefore, the heat dissipation promoting portion 55 does not hinder the flow of the oxidant gas in the cooling channel portion 15c. Therefore, the oxidant gas for chemical reaction can be stably supplied to the fuel cell stack 31, and the temperature of the fuel upstream portion 31u can be easily lowered appropriately.

The shape and arrangement of the heat dissipation promotion part 55 are not limited to the above examples, and any shape and arrangement can be adopted as long as the desired heat dissipation performance can be exhibited.

Second Embodiment This embodiment is a modification based on the preceding embodiment. In this embodiment, the heat dissipation promoting section 255 includes a stirring section 255s. Further, a stirring portion 255s and a radiation fin 255f are provided in one cooling channel portion 15c.

In FIG. 7, a heat dissipation promoting portion 255 is provided in the cooling channel portion 15c of the upstream cathode separator 15u. The heat dissipation promoting section 255 includes a stirring section 255s for disturbing the flow of the oxidant gas. The stirring part 255s is a convex part that protrudes in the Z direction from the upstream cathode separator 15u. The stirring part 255s has a plate shape with the X direction as the longitudinal direction. The amount of protrusion of the stirring part 255s from the upstream cathode separator 15u is smaller than the height of the upstream cathode separator 15u. In other words, the size of the stirring portion 255s in the Z direction is smaller than the size of the upstream cathode separator 15u in the Z direction.

The stirring section 255s is provided at a substantially central portion in the Y direction of the cooling channel section 15c. The stirring portion 255s is provided at a position including the starting end portion, which is the most upstream portion of the flow of the oxidizing gas in the cooling channel portion 15c. The size of the stirring part 255s in the X direction is smaller than the size of the upstream cathode separator 15u in the X direction. The stirring part 255s is not provided in the portion including the end part of the cooling channel part 15c. Therefore, when the fuel cell 11 is viewed from the X direction, the stirring portion 255s can be visually recognized from the starting end side, and the stirring portion 255s cannot be visually recognized from the terminal end side.

The heat dissipation promotion part 255 includes heat dissipation fins 255f. The radiation fins 255f are provided downstream of the stirring section 255s in the flow of the oxidant gas. The size of the radiation fins 255f in the X direction is larger than the size of the stirring part 255s in the X direction. The size of the radiation fins 255f in the Y direction is smaller than the size of the stirring part 255s in the Y direction. The size of the radiation fins 255f in the Z direction is larger than the size of the stirring part 255s in the Z direction. In other words, the stirring part 255s and the heat radiation fins 255f have different shapes.

Since the stirring portion 255s is provided in the upstream cathode separator 15u, the flow of the oxidant gas around the stirring portion 255s is stirred. More specifically, the oxidant gas flowing into the cooling channel portion 15c collides with the stirring portion 255s, thereby changing the flow of the oxidant gas. As a result, the oxidant gas flowing in the X direction along the surface of the upstream cathode separator 15u can flow not only in the X direction but also in the Y and Z directions. In other words, the stirring part 255s disturbs the flow of the oxidant gas and changes it from laminar flow to turbulent flow.

The stirring by the stirring part 255s can suppress the oxidant gas flowing near the surface of the upstream cathode separator 15u from continuing to flow along the X direction while maintaining the position near the surface. Therefore, the oxidant gas whose temperature has increased by flowing near the surface of the upstream cathode separator 15u is separated from near the surface of the upstream cathode separator 15u. After that, the oxidizing gas before the temperature rises is attracted near the surface of the upstream cathode separator 15u.

In summary, by stirring the flow of the oxidizing gas, it is possible to separate the oxidizing gas flowing near the upstream cathode separator 15u and attract the oxidizing gas flowing away from the upstream cathode separator 15u. This facilitates maintaining a large temperature difference between the upstream cathode separator 15u and the oxidant gas. Therefore, it is easy to improve the heat exchange efficiency between the upstream cathode separator 15u and the oxidant gas. In other words, it is easy to improve the heat dissipation property of dissipating the heat of the upstream cathode separator 15u to the oxidant gas.

According to the above-described embodiment, the heat dissipation promoting section 255 is the stirring section 255s that stirs the flow of the oxidant gas. Therefore, of the oxidant gas flowing through the cathode separator 15, the proportion of the oxidant gas that contacts the cathode separator 15 and exchanges heat can be increased. Therefore, it is easy to improve the heat dissipation in the upstream cathode separator 15u provided with the stirring part 255s. In particular, the heat exchange efficiency can be greatly improved by changing the flow of the oxidant gas from a laminar flow with a low heat exchange efficiency to a turbulent flow with a high heat exchange efficiency by the stirring section 255s.

The cathode separator 15 includes a stirring section 255s and heat radiation fins 255f from upstream to downstream of the oxidant gas flow. In other words, the cathode separator 15 includes a plurality of heat dissipation promoting portions 255 having different shapes from upstream to downstream of the oxidant gas flow. Therefore, it is possible to finely adjust the heat dissipation property by combining the heat dissipation promoting portions 255 having various shapes. In addition, a structure that realizes improvement in heat dissipation for different purposes, such as the stirring part 255s for the purpose of stirring the flow of the oxidant gas and the heat dissipation fins 255f for the purpose of enlarging the contact area with the oxidant gas. can be combined. Therefore, by adopting an appropriate combination for the plurality of heat dissipation promoting portions 255, it is easy to improve heat dissipation.

The stirring portion 255s is provided at a position including the starting end portion, which is the most upstream portion of the flow of the oxidizing gas in the cooling channel portion 15c. Therefore, the flow of the oxidant gas can be disturbed at the most upstream of the flow of the oxidant gas in the cooling channel portion 15c. Therefore, the effect of improving the heat exchange efficiency can be obtained over the entire cooling channel portion 15c from upstream to downstream of the flow of the oxidant gas.

The stirring part 255s is provided at a position including the starting end, which is the most upstream part of the flow of the oxygen-containing gas in the cooling channel part 15c, and is not provided at the terminal end. In other words, the fuel cell stack 31 is installed so that the side on which the stirring part 255s can be visually recognized is the most upstream part of the flow of the oxidant gas. Therefore, it is easy to recognize the proper orientation of the fuel cell stack 31, and it is easy to prevent the fuel cell stack 31 from being arranged in the wrong orientation with respect to the oxygen-containing gas supply device 50. FIG.

Although the configuration including the stirring section 255s and the heat radiation fins 255f has been described as an example of the heat radiation promoting section 255, the configuration of the heat radiation promoting section 255 is not limited to the above configuration. For example, the heat dissipation promoting section 255 may be configured only with the stirring section 255s. Further, the heat dissipation promoting part 255 may be configured by a plurality of stirring parts 255s provided between upstream and downstream of the flow of the oxidant gas.

As the agitating part 255s, the convex part protruding from the cathode separator 15 in the Z direction has been described as an example, but the structure for agitating the flow of the oxidant gas is not limited to the convex part. For example, it may be constituted by a concave portion recessed in the Z direction from the cathode separator 15 . Alternatively, the stirring portion 255s may be configured by combining a convex portion and a concave portion.

The shape and arrangement of the heat dissipation promotion part 255 are not limited to the above examples, and any shape and arrangement can be adopted as long as the desired heat dissipation performance can be exhibited.

Third Embodiment This embodiment is a modification based on the preceding embodiment. In this embodiment, the heat radiation fins 355f, which are the heat radiation promoting portion 355, are provided in both the cooling channel portion 15c and the reaction channel portion 15r.

In FIG. 8, the cooling channel portion 15c and the reaction channel portion 15r of the upstream cathode separator 15u are provided with heat radiation fins 355f functioning as the heat radiation promoting portion 355. As shown in FIG. The radiation fins 355f are provided so as to protrude in the Z direction from the upstream cathode separator 15u. The heat radiating fins 355f provided in the cooling channel portion 15c protrude in the direction away from the membrane electrode assembly 12 in the Z direction. On the other hand, the heat radiation fins 355f provided in the reaction channel portion 15r protrude in the Z direction toward the membrane electrode assembly 12. As shown in FIG.

The radiation fin 355f has a plate shape with the X direction as the longitudinal direction. The amount of protrusion of the heat radiation fins 355f from the upstream cathode separator 15u is smaller than the height of the upstream cathode separator 15u. In other words, the size of the heat radiation fins 355f in the Z direction is smaller than the size of the upstream cathode separator 15u in the Z direction. Therefore, when the fuel cells 11 are stacked, the Z-direction ends of the heat radiation fins 355f provided in the cooling channel portion 15c do not contact the adjacent fuel cells 11 . Therefore, the oxidant gas can pass through the gaps between the heat radiation fins 355f provided in the cooling channel portion 15c and the adjacent fuel cells 11. As shown in FIG. In addition, the end portion in the Z direction of the radiation fin 355f provided in the reaction channel portion 15r does not contact the oxidant gas diffusion layer 14a. Therefore, the oxidizing gas can pass through the gap between the heat radiation fins 355f provided in the reaction flow path portion 15r and the oxidizing gas diffusion layer 14a.

The size of the radiation fins 355f in the Z direction is at least half the size of the upstream cathode separator 15u in the Z direction. The radiation fins 355f are provided at substantially the center of the cooling channel portion 15c in the Y direction. The radiating fins 355f are provided continuously from the starting end, which is the most upstream portion of the flow of the oxidizing gas in the cooling channel portion 15c, to the terminal end, which is the most downstream portion.

By providing the heat radiation fins 355f on the upstream cathode separator 15u, it is possible to secure a large surface area where the oxidant gas and the upstream cathode separator 15u come into contact. The larger the radiation fins 355f are, the larger the contact surface area between the oxidant gas and the upstream cathode separator 15u can be secured. A plurality of heat radiation fins 355f may be provided in one cooling channel portion 15c.

According to the above-described embodiment, the heat dissipation promoting portion 355 is provided in both the cooling channel portion 15c and the reaction channel portion 15r of the upstream cathode separator 15u. Therefore, compared with the case where the heat dissipation promoting part 355 is provided only in the cooling channel part 15c, the heat dissipation of the upstream cathode separator 15u can be easily improved.

A gap is provided between the radiating fins 355f provided in the reaction channel portion 15r and the oxidant gas diffusion layer 14a. Therefore, the radiation fins 355f are less likely to block the flow of the oxidizing gas into the oxidizing gas diffusion layer 14a.

The radiation fins 355f provided in the cooling channel portion 15c and the radiation fins 355f provided in the reaction channel portion 15r may have different shapes. For example, the size in the Z direction of the heat radiation fins 355f of the reaction channel portion 15r is made smaller than the size in the Z direction of the heat radiation fins 355f of the cooling channel portion 15c. According to this, it is easy to stably supply an appropriate amount of oxidant gas to the membrane electrode assembly 12 by reducing an increase in pressure loss in the reaction flow channel portion 15r.

The shape and arrangement of the heat dissipation promotion part 355 are not limited to the above examples, and any shape and arrangement can be adopted as long as the desired heat dissipation performance can be exhibited.

Fourth Embodiment This embodiment is a modification based on the preceding embodiment. In this embodiment, heat radiation fins 455f functioning as heat radiation promoting portions 455 are provided. The radiation fins 455f are configured such that the amount of protrusion from the cathode separator 15 decreases from upstream to downstream of the fuel gas flow.

In FIG. 9, since the fuel cells 11 are stacked in the Z direction, the cathode separators 15 and the anode separators 16 are alternately arranged in the Z direction. Here, illustration of the membrane electrode assembly 12, the oxidant gas diffusion layer 14a, and the fuel gas diffusion layer 14b that constitute the fuel cell 11 is omitted.

The radiation fins 455f are provided for each of the plurality of cooling channel portions 15c, and the cooling channel portions 15c and the reaction channel portions 15r are alternately formed in the Y direction. Therefore, in the cathode separator 15, the channel portions having the radiating fins 455f and the channel portions not having the radiating fins 455f are alternately formed. Also, the radiation fins 455f are provided on both the upstream cathode separator 15u and the downstream cathode separator 15d.

A plurality of radiation fins 455f are provided from upstream to downstream of the fuel gas flow. The projecting amount of the radiation fins 455f increases as the radiation fins 455f are provided closer to the fuel inlet portion 32 in the Y direction. In other words, the projecting amount of the radiation fins 455f becomes smaller as they are provided closer to the fuel outlet portion 33 in the Y direction. Therefore, the amount of protrusion of the heat radiation fins 455f provided on the upstream cathode separator 15u is larger than the amount of protrusion of the heat radiation fins 455f provided on the downstream cathode separator 15d.

The protrusion amount of the radiation fins 455f differs by a predetermined amount between adjacent radiation fins 455f in the Y direction. For example, when the projection amount of the smallest radiation fin 455f is F0, the projection amount of the adjacent radiation fin 455f in the Y direction can be set to twice F0. Further, the amount of protrusion of the radiation fin 455f next to it can be set to three times F0. In this way, by setting the protrusion amount to a multiple of F0, the protrusion amounts of the radiation fins 455f adjacent to each other in the Y direction can be made different by F0. In other words, the amount of protrusion of the radiation fins 455f can be linearly related to the position in the Y direction.

The amount of protrusion of the radiation fins 455f is not limited to the case where it is in a linear relationship with respect to the position in the Y direction. For example, the amount of protrusion of the radiation fins 455f may have a non-linear relationship with respect to the position in the Y direction. Alternatively, the amount of protrusion of the radiating fins 455f on the downstream cathode separator 15d may be all set to F0, and the amount of protrusion of the fins 455f on the upstream cathode separator 15u may be set to five times F0.

The larger the amount of projection of the heat radiation fins 455f, the larger the surface area in contact with the oxidant gas and the higher the heat radiation. On the other hand, the smaller the amount of protrusion of the heat radiation fins 455f, the smaller the surface area in contact with the oxidant gas, and the lower the heat radiation performance. Therefore, the heat dissipation of the upstream cathode separator 15u is higher than that of the downstream cathode separator 15d.

According to the above-described embodiment, the amount of protrusion of the heat radiation fins 455f from the cathode separator 15 decreases from upstream to downstream of the fuel gas flow. Therefore, the heat dissipation property of the cathode separator 15 can be changed stepwise. Therefore, in the cathode separator 15, it is easy to suppress the occurrence of portions with too high or too low heat dissipation.

The shape and arrangement of the heat dissipation promotion part 455 are not limited to the above examples, and any shape and arrangement can be adopted as long as the desired heat dissipation performance can be exhibited.

Fifth Embodiment This embodiment is a modification based on the preceding embodiment. In this embodiment, heat radiation fins 555f functioning as heat radiation promoting portions 555 are provided. The radiation fins 555f are configured such that the amount of protrusion from the cathode separator 15 increases from upstream to downstream of the flow of the oxidant gas.

In FIG. 10, the cooling channel portion 15c of the upstream cathode separator 15u is provided with heat radiation fins 555f as the heat radiation promoting portion 555. As shown in FIG. The radiation fins 555f are provided so as to protrude in the Z direction from the upstream cathode separator 15u. The radiation fin 555f has a plate shape with the X direction as the longitudinal direction. The amount of protrusion of the radiating fins 555f from the upstream cathode separator 15u is configured to gradually increase from upstream to downstream of the flow of the oxidant gas. Therefore, the surface area of the cooling channel portion 15c is the largest at the most upstream side of the oxidant gas and the smallest at the most downstream side.

The amount of protrusion of the radiation fins 555f is linearly changed with respect to the position in the X direction. However, the relationship between the position in the X direction and the amount of protrusion of the radiation fins 555f is not limited to a linear relationship. For example, the amount of protrusion of the radiation fins 455f may have a non-linear relationship with respect to the position in the X direction. Alternatively, the amount of protrusion of the heat radiating fins 455f from the starting end to the center in the X direction may be constant F0, and the amount of protrusion from the center in the X direction to the end may be five times F0. In this case, the radiation fins 555f have a stepped shape in the X direction.

The oxidizing gas contacts with the surface of the cathode separator 15 and exchanges heat while flowing through the cooling channel portion 15c. Therefore, the temperature of the oxidizing gas tends to be lowest upstream and highest downstream of the flow of the oxidizing gas. That is, from the viewpoint of the temperature of the oxidant gas, the heat dissipation property of the upstream of the flow of the oxidant gas is high, and the heat dissipation property of the downstream is low. On the other hand, the surface area of the cooling channel portion 15c is configured to be the smallest at the most upstream side of the oxidant gas and the largest at the most downstream side. Therefore, from the viewpoint of the surface area of the cooling channel portion 15c, the heat dissipation property of the upstream side of the flow of the oxidant gas is low, and the heat dissipation property of the downstream side is high.

In summary, the upstream side of the flow of the oxidant gas in the cooling channel portion 15c has a large temperature difference from the oxidant gas and a small surface area capable of exchanging heat, so the heat dissipation is moderate. On the other hand, the downstream side of the flow of the oxidant gas in the cooling channel portion 15c has a small temperature difference from the oxidant gas and a large surface area capable of exchanging heat, so the heat dissipation is moderate. By providing the heat radiation fins 555f in this manner, the heat radiation distribution in the X direction can be made approximately the same in the cooling flow path portion 15c. In other words, by providing the radiation fins 555f, it is possible to eliminate variations in temperature distribution in the flow direction of the oxidant gas.

According to the embodiment described above, the radiation fins 555f are configured such that the amount of protrusion from the cathode separator 15 increases from upstream to downstream of the flow of the oxidant gas. Therefore, a larger surface area can be secured for the radiation fins 555f toward the downstream side of the flow of the oxidant gas. Therefore, it is possible to eliminate the occurrence of a large deviation in heat dissipation in the flow direction of the oxidant gas.

The shape and arrangement of the heat dissipation promotion part 555 are not limited to the above examples, and any shape and arrangement can be adopted as long as the desired heat dissipation performance can be exhibited.

Sixth Embodiment This embodiment is a modification based on the preceding embodiment. In this embodiment, the upstream cathode separator 615u is made of a material with higher heat dissipation than the downstream cathode separator 615d. Also, the Y-direction size of the cooling channel portion 615c in the upstream cathode separator 615u is smaller than the Y-direction size of the cooling channel portion 615c in the downstream cathode separator 615d.

In FIG. 11, the upstream cathode separator 615u is made of a metal material such as titanium, stainless steel, or aluminum. On the other hand, the downstream cathode separator 615d is made of carbon. Generally, metal materials are materials with higher thermal conductivity than carbon. Therefore, the upstream cathode separator 615u is made of a material with higher heat dissipation than the downstream cathode separator 615d.

The cooling channel portion 615c of the upstream cathode separator 615u is smaller in size in the Y direction than the cooling channel portion 615c of the downstream cathode separator 615d. On the other hand, the Y-direction size of the reaction channel portion 15r is the same for both the upstream cathode separator 615u and the downstream cathode separator 615d. In addition, the cooling channel portion 615c of the downstream cathode separator 615d and the reaction channel portion 15r have substantially the same size in the Y direction. In summary, only the cooling channel portion 615c in the upstream cathode separator 615u is smaller in size in the Y direction than the other channel portions of the cathode separator 615. FIG.

The Z-direction size of the cooling channel portion 615c is the same for both the upstream cathode separator 615u and the downstream cathode separator 615d. Here, the cross-sectional area of the channel portion is calculated as the product of the channel width, which is the size in the Y direction, and the channel height, which is the size in the Z direction. Therefore, the cross-sectional area of the cooling channel portion 615c in the upstream cathode separator 615u having a small channel width is smaller than that of the other channel portions. The smaller the cross-sectional area of the cooling channel portion 615c, the faster the flow velocity of the oxidant gas flowing through the cooling channel portion 615c. Therefore, the smaller the cross-sectional area, the more oxidant gas can flow near the surface of the upstream cathode separator 615u. In other words, the smaller the cross-sectional area, the better the heat dissipation.

According to the embodiment described above, the cooling channel portion 615c in the upstream cathode separator 615u has a smaller cross-sectional area than the cooling channel portion 615c in the downstream cathode separator 615d. Therefore, the flow velocity of the oxidant gas flowing through the cooling channel portion 615c of the upstream cathode separator 615u can be increased, and the heat dissipation can be enhanced. Also, a large number of cooling channel portions 615c can be formed in the upstream cathode separator 615u. Therefore, heat dissipation can be enhanced.

The upstream cathode separator 615u is made of a material with higher heat dissipation than the downstream cathode separator 615d. Therefore, it is easy to maintain the temperature of the fuel downstream portion 31d higher than the temperature of the fuel upstream portion 31u. Therefore, in the fuel downstream portion 31d, which tends to contain a large amount of water vapor, it is easy to suppress the generation of stagnant water W due to condensation of water vapor.

The upstream cathode separator 615u may be made of a material having a higher heat dissipation property than the downstream cathode separator 615d, and the heat dissipation fins 55f and the stirring section 255s may be provided. According to this, it is possible to improve the heat dissipation properties of the upstream cathode separator 615u and the heat dissipation properties of the downstream cathode separator 615d in terms of both material and structure.

Other Embodiments The disclosures in this specification, drawings, etc. are not limited to the illustrated embodiments. The disclosure encompasses the illustrated embodiments and variations thereon by those skilled in the art. For example, the disclosure is not limited to the combinations of parts and/or elements shown in the embodiments. The disclosure can be implemented in various combinations. The disclosure can have additional parts that can be added to the embodiments. The disclosure encompasses omitting parts and/or elements of the embodiments. The disclosure encompasses permutations or combinations of parts and/or elements between one embodiment and another. The disclosed technical scope is not limited to the description of the embodiments. The disclosed technical scope is indicated by the description of the claims, and should be understood to include all changes within the meaning and range of equivalents to the description of the claims.

The disclosure in the specification, drawings, etc. is not limited by the description in the claims. The disclosure in the specification, drawings, etc. encompasses the technical ideas described in the claims, and extends to more diverse and broader technical ideas than the technical ideas described in the claims. Therefore, various technical ideas can be extracted from the disclosure of the specification, drawings, etc., without being bound by the scope of claims.

1 Fuel Cell System 11 Fuel Cell 12 Membrane Electrode Assembly 15 Cathode Separator 15u Upstream Cathode Separator 15d Downstream Cathode Separator 15c Cooling Channel 15r Reaction Channel 16 Anode Separator 31 Fuel cell stack 31u fuel upstream portion 31d fuel downstream portion 32 fuel inlet portion 33 fuel outlet portion 50 oxidant gas supply device 55 heat dissipation promotion portion 55f heat dissipation fins 60 fuel gas supply device 255 heat dissipation promotion portion 255f heat dissipation fin 255s stirring part 355 heat dissipation promotion part 355f heat dissipation fin 455 heat dissipation promotion part 455f heat dissipation fin 555 heat dissipation promotion part 555f heat dissipation fin 615 cathode separator 615u upstream cathode separator 615d downstream cathode separator 615c Cooling channel

Claims (11)

a fuel cell stack (31) having a plurality of fuel cells (11) for generating power through a chemical reaction between fuel gas and oxidant gas;
a fuel gas supply device (60) for supplying fuel gas to the fuel cell stack;
an oxidant gas supply device (50) for supplying oxidant gas to the fuel cell stack and cooling the fuel cell stack;
The fuel cell stack is
a fuel inlet (32) for introducing fuel gas into the interior of the fuel cell stack;
a fuel outlet (33) for leading fuel gas from the interior of the fuel cell stack;
a fuel upstream portion (31u), which is a portion of the fuel cell stack closer to the fuel inlet than the fuel outlet;
a fuel downstream portion (31d), which is a portion closer to the fuel outlet portion than the fuel inlet portion of the fuel cell stack,
The fuel cell is
a cathode separator (15, 615) forming a channel for an oxidant gas;
an anode separator (16) forming a fuel gas flow path,
The cathode separator is
a downstream cathode separator (15d, 615d) forming part of the fuel downstream;
and an upstream cathode separator (15u, 615u) that constitutes a part of the fuel upstream portion and has higher heat dissipation than the downstream cathode separator. 2. The fuel cell system according to claim 1, wherein the oxidant gas flow path in the upstream cathode separator has a larger surface area in contact with the oxidant gas than the oxidant gas flow path in the downstream cathode separator. 3. The fuel cell system according to claim 2, wherein the cathode separator includes a heat dissipation promoting portion (55, 255, 355, 455, 555) provided in the flow path of the oxidant gas. 4. The fuel cell system according to claim 3, wherein the heat dissipation promoting portion is a heat dissipation fin (55f) protruding from the cathode separator. 5. The fuel cell system according to claim 4, wherein the radiation fins protrude from the cathode separator in a decreasing amount from upstream to downstream of the flow of the fuel gas. 5. The fuel cell system according to claim 4, wherein the heat radiating fins protrude from the cathode separator to a greater extent from upstream to downstream of the flow of the oxidant gas. 4. The fuel cell system according to claim 3, wherein the heat dissipation promoting section is a stirring section (255s) that stirs the flow of the oxidant gas. 8. The fuel cell system according to any one of claims 3 to 7, wherein said cathode separator comprises a plurality of said heat dissipation promoting portions having different shapes from upstream to downstream of said oxidant gas flow. The cathode separator is
a reaction channel portion (15r) through which the oxidant gas used for reaction with the fuel gas flows;
a cooling channel portion (15c) through which the oxidant gas that is not used for reaction with the fuel gas flows;
9. The fuel cell system according to any one of claims 3 to 8, wherein more heat release promoting portions are provided in said cooling channel portion than in said reaction channel portion. The cathode separator is
a reaction channel portion (15r) through which the oxidant gas used for reaction with the fuel gas flows;
a cooling flow channel (615c) through which the oxidant gas that is not used for reaction with the fuel gas flows;
2. The fuel cell system according to claim 1, wherein the cooling channel portion in the upstream cathode separator has a smaller cross-sectional area than the cooling channel portion in the downstream cathode separator. 11. The fuel cell system according to any one of claims 1 to 10, wherein the upstream cathode separator is made of a material with higher heat dissipation than the downstream cathode separator.

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