JP6857827B2 - Fuel cell system - Google Patents

Description

The present invention relates to a fuel cell system, and more particularly to a fuel cell system that discharges anode-off gas from the anode of the fuel cell.

As a conventional fuel cell system, the fuel cell system shown in Patent Document 1 is known. In this fuel cell system, the heat medium circulating in the fuel cell is cooled by the heat exchanger by the air sent by the heat exchange fan. Further, this air diffuses the anode off-gas discharged from the anode of the fuel cell and dilutes the hydrogen contained in the anode-off gas.

Japanese Unexamined Patent Publication No. 2011-65903

However, there is still room for improvement in the prior art of Patent Document 1 from the viewpoint of achieving both dilution of the anode off-gas and temperature control of the fuel cell. The present invention has been made to solve such a problem, and an object of the present invention is to provide a fuel cell system capable of achieving both dilution of anode off-gas and temperature control of a fuel cell.

A fuel cell system according to an aspect of the present invention includes a fuel cell that generates power using a fuel gas and an oxidizing agent gas, a supply flow path through which the fuel gas supplied to the anode of the fuel cell flows, and the anode. A recycle flow path through which the anode off-gas discharged from is circulated and connected to the supply flow path, a discharge flow path branched from the recycle flow path and through which the anode off-gas flows, and an opening / closing provided in the discharge flow path. A valve, a heat exchanger that exchanges heat between the cooling water that cools the fuel cell and air, a water flow path through which the cooling water circulates between the fuel cell and the heat exchanger, and the heat exchange. A blower fan that sends the air to the vessel, an anode off gas discharged from the discharge flow path, a confluence portion in which the air that has passed through the heat exchanger merges and discharges to the outside, and a controller are provided. The controller reduces the air volume of the blower fan before opening the on-off valve and discharging the anode off gas, and reduces the air volume of the blower fan when the on-off valve is opened and the anode off gas is discharged. To increase.

The present invention has the effect that it is possible to achieve both dilution of the anode off gas and temperature control of the fuel cell in the fuel cell system.

The above objectives, other objectives, features, and advantages of the present invention will be apparent from the following detailed description of preferred embodiments with reference to the accompanying drawings.

It is a functional block diagram which shows the structure of the fuel cell system which concerns on Embodiment 1 of this invention. It is a flowchart which shows an example of the operation method of the fuel cell system shown in FIG. It is a timing diagram of opening / closing of an on-off valve and air volume adjustment of a blower fan in a conventional fuel cell system. It is a graph which shows the temperature change of the fuel cell in the conventional fuel cell system. It is a timing diagram of opening / closing of an on-off valve and air volume adjustment of a blower fan in the fuel cell system of FIG. It is a graph which shows the temperature change of the fuel cell in the fuel cell system of FIG. It is a flowchart which shows an example of the operation method of the fuel cell system which concerns on Embodiment 3 of this invention.

(Knowledge that became the basis of the present invention)
The present inventors have diligently studied the compatibility between the dilution of the anode off-gas in the fuel cell system and the temperature control of the fuel cell. Among them, the present inventors have found that the prior art has the following problems.

In the fuel cell system of Patent Document 1, the heat exchanger fan is driven at the maximum rotation speed when the anode off-gas is discharged (purged). As a result, the anode off-gas is diffused by the air generated by the heat exchanger fan, and the hydrogen in the anode off-gas is diluted.

However, when the heat exchanger fan is driven at the maximum rotation speed, the temperature of the heat medium drops too much due to the air generated by the heat exchanger fan. As a result, it may not be possible to keep the fuel cell through which the heat medium passes within a predetermined temperature range.

On the other hand, when the rotation speed of the heat exchanger fan is lowered in order to maintain the fuel cell in a predetermined temperature range, the amount of air by the heat exchanger fan is reduced accordingly. Therefore, there arises a problem that the anode off-gas cannot be sufficiently diluted with air from the heat exchanger fan so that the hydrogen concentration of the anode-off gas becomes equal to or less than a predetermined value.

Therefore, the present inventors reduce the air volume of the blower fan before discharging the anode off gas and increase the air volume of the blower fan when discharging the anode off gas to dilute the anode off gas and control the temperature of the fuel cell. We are trying to achieve both. The present invention has been made based on this finding.

The fuel cell system according to the first embodiment of the present invention includes a fuel cell that generates power using a fuel gas and an oxidizing agent gas, and a supply flow path through which the fuel gas supplied to the anode of the fuel cell flows. , A recycle flow path through which the anode off gas discharged from the anode flows and is connected to the supply flow path, a discharge flow path branched from the recycle flow path and through which the anode off gas flows, and the discharge flow path are provided. An on-off valve, a heat exchanger that exchanges heat between the cooling water that cools the fuel cell and air, a water flow path through which the cooling water circulates between the fuel cell and the heat exchanger, and the like. A blower fan that sends the air to the heat exchanger, an anode off gas discharged from the discharge flow path, a confluence portion where the air that has passed through the heat exchanger merges and discharges to the outside, a controller, and the controller. The controller reduces the air volume of the blower fan before opening the on-off valve to discharge the anode off gas, and opens the on-off valve to discharge the anode off gas. Increase the air volume of.

According to this configuration, the anode off-gas discharged from the discharge channel and the air that has passed through the heat exchanger merge at the confluence, so that the anode-off gas is sufficiently diluted with air and from the confluence to the outside. Can be discharged. In addition, the air blown by the blower fan can be used for both cooling the cooling water and diluting the anode off-gas. Further, by reducing the air volume of the blower fan before discharging the anode off-gas, the temperature of the cooling water cooled by the blower of the blower fan and the fuel cell cooled by the blower is raised. Then, when the anode off gas is discharged, the temperature of the cooling water and the fuel cell decreases from this increased temperature due to the increase in the air volume of the blower fan, so that the fuel cell is prevented from becoming too cold and the temperature of the fuel cell is appropriately controlled. be able to.

In the fuel cell system according to the second aspect of the embodiment of the present invention, in the first aspect, the supply flow path is the first supply flow path, the discharge flow path is the first discharge flow path, and the fuel cell. A second supply flow path through which the oxidant gas supplied to the cathode of the cathode flows, and a second discharge flow path through which the cathode off gas discharged from the cathode flows, and the anode off gas at the confluence portion. The air and the cathode off gas discharged from the second discharge flow path may merge and be discharged to the outside. According to this configuration, by discharging the cathode off gas to the confluence portion, the anode off gas can be sufficiently diluted by the cathode off gas in addition to air and discharged from the confluence portion to the outside.

In the fuel cell system according to the third aspect of the embodiment of the present invention, in the first or second aspect, when the controller opens the on-off valve and discharges the anode off gas, the air volume of the blower fan is increased. In addition, the air volume of the blower fan may be reduced when the on-off valve is closed to stop the discharge of the anode off gas. According to this configuration, by reducing the air volume of the blower fan after the anode off gas is discharged, the temperature of the fuel cell lowered due to the increase in the air volume at the time of discharging the anode off gas is rapidly raised, and the temperature fluctuation of the fuel cell is caused. It can be suppressed.

In the fuel cell system according to the fourth aspect of the embodiment of the present invention, in any one of the first to third aspects, the smaller the output of the fuel cell, the smaller the controller, the earlier the on-off valve is opened. The time for reducing the air volume of the blower fan may be lengthened. According to this configuration, even when the output of the fuel cell is small and the temperature response of the fuel cell to the decrease of the air volume of the blower fan is slow, the blower fan is increased by lengthening the time for reducing the air volume of the blower fan. It is possible to reduce the temperature fluctuation of the cooling water cooled by the blown air and the fuel cell cooled by the cooling water.

Hereinafter, embodiments of the present invention will be specifically described with reference to the drawings. In the following, the same or corresponding elements will be designated by the same reference numerals throughout the drawings, and duplicate description thereof will be omitted.

(Embodiment 1)
<Structure>
The fuel cell system 10 according to the first embodiment will be described with reference to FIG. The fuel cell system 10 includes a fuel cell 11, a supply flow path (first supply flow path) 12, a recycling flow path 13, a discharge flow path (first discharge flow path) 14, an on-off valve 15, a heat exchanger 16, and a water flow path. It includes 17, a blower fan 18, a merging unit 19, and a controller 20. In addition to this, the fuel cell system 10 may include a first circulatory system 21 and a second circulatory system 22.

The fuel cell 11 is a device that generates electricity by electrochemically reacting hydrogen in a fuel gas with oxygen in an oxidant gas. The fuel cell 11 includes a stack (not shown) in which a plurality of cells are stacked. The cell is composed of an electrolyte using a polymer electrolyte membrane and a pair of electrodes (anode, cathode) sandwiching the electrolyte. The cell is provided with an anode flow path that supplies fuel gas to the anode and a cathode flow path that supplies oxidant gas to the cathode.

The first supply flow path 12 is a flow path through which the fuel gas supplied to the anode of the fuel cell 11 flows, and is connected to the inlet of the anode flow path of the fuel cell 11. This fuel gas is hydrogen or a gas containing hydrogen, for example, a reformed gas obtained by reforming a raw material gas such as city gas with a reformer (not shown), and water electrolysis. Hydrogen obtained from the above is used. The first supply flow path 12 may be provided with a humidifier (not shown) for humidifying the fuel gas.

A fuel gas supply device (not shown) may be provided in the first supply flow path 12. For example, when the pressure of the fuel gas supplied to the fuel cell 11 is lower than the pressure loss of the fuel gas flowing through the fuel cell 11, the fuel gas can be boosted by the fuel supply device and supplied to the fuel cell 11. Further, the fuel gas supply device may be provided with a pressure regulator capable of adjusting the pressure of the fuel gas. As a result, for example, when a hydrogen tank or the like is used as the fuel gas supply source and the pressure of the fuel gas supplied to the fuel cell 11 is higher than the pressure loss of the fuel gas, the fuel gas is brought to a predetermined pressure by the pressure regulator. Can be adjusted and supplied to the fuel cell 11.

The recycling flow path 13 is a flow path through which the anode off gas discharged from the anode of the fuel cell 11 flows, and connects the outlet of the anode flow path of the fuel cell 11 and the first supply flow path 12. As a result, a circulation flow path is formed by the recycling flow path 13, the first supply flow path 12 on the downstream side of the connection point, and the anode flow path of the fuel cell 11.

Since the anode off-gas discharged from the anode flow path of the fuel cell 11 still contains unused hydrogen, this hydrogen can be reused in the fuel cell 11. Therefore, the anode off gas discharged from the anode flow path is used as fuel gas to flow from the recycling flow path 13 into the first supply flow path 12, and flows through the first supply flow path 12 on the upstream side of the connection point of the recycling flow path 13. It is mixed with the fuel gas that has been used and supplied to the anode flow path of the fuel cell 11. In this way, the anode off-gas circulates in the circulation flow path including the recycling flow path 13, the first supply flow path 12, and the anode flow path.

The first circulator 21 is a device provided in the recycling flow path 13 and for allowing the anode off gas flowing through the recycling flow path 13 to flow into the first supply flow path 12, and is generally a step-up pump or the like. Is used. For the first circulatory system 21, for example, an electromagnetic induction type diaphragm pump capable of adjusting the flow rate of the anode off gas by an input voltage is used.

The first discharge flow path 14 is a flow path that branches from the recycling flow path 13 and extends to the confluence portion 19 and through which the anode off-gas flows. The first discharge flow path 14 is connected to the recycling flow path 13 on the upstream side of the first circulatory system 21 and communicates with the outside of the fuel cell system 10 via the confluence portion 19.

The on-off valve 15 is provided in the first discharge flow path 14, and for example, a solenoid type solenoid valve is used. When the on-off valve 15 is opened and opened, impurities such as anode off-gas and condensed water flowing through the recycling flow path 13 pass through the on-off valve 15 from the recycling flow path 13 to the outside via the first discharge flow path 14. It is discharged.

The water flow path 17 is a flow path through which cooling water for maintaining the temperature of the fuel cell 11 at a predetermined target temperature flows, penetrates the fuel cell 11 and the heat exchanger 16, and penetrates the fuel cell 11 and the heat exchanger 16. It circulates between and. The water flow path 17 may be provided with a fuel cell 11, a second circulator 22 and a heat exchanger 16, and may be provided with a temperature detector, a flow meter, or the like (not shown), if necessary.

The second circulator 22 is a device that circulates the cooling water flowing through the water flow path 17 between the fuel cell 11 and the heat exchanger 16, and is, for example, a pump. The second circulator 22 has, for example, a function (flow rate adjusting function) capable of adjusting the flow rate of the cooling water circulating in the water flow path 17 in response to a control signal from the controller 20. The flow rate adjusting function may be built in the second circulatory system 22, or may be provided separately from the second circulatory system 22 as a component having the flow rate adjusting function.

The heat exchanger 16 is a device that exchanges heat between the cooling water flowing through the fuel cell 11 and the air in the atmosphere. For example, the heat exchanger 16 includes a fin-and-tube type radiator. In this case, the heat of the cooling water discharged from the heat exchanger 16 is released to the atmosphere, and the cooling water is cooled. The heat exchanger 16 may be of any type.

The blower fan 18 is a fan that sends air to the heat exchanger 16. The blower fan 18 may be a suction type that draws air toward the heat exchanger 16 side, or may be a blow type that sends air toward the heat exchanger 16 side. Air is introduced into the heat exchanger 16 by the blower fan 18, and the heat dissipation effect in the heat exchanger 16 is promoted. Thereby, the size of the heat exchanger 16 can be maintained or reduced. Further, the air volume (m ³ / min) of the blower fan 18 is variable and is controlled by the controller 20. For example, a first temperature sensor 17a is provided in the water flow path 17 at the inlet of the fuel cell 11, and the blower fan 18 is based on the temperature of the cooling water at the inlet of the fuel cell 11 detected by the first temperature sensor 17a. The air volume is adjusted.

The merging portion 19 is configured such that the anode off gas discharged from the first discharge flow path 14 and the air passing through the heat exchanger 16 merge and are discharged to the outside. For example, the merging portion 19 is a space provided in the housing 23, is adjacent to the heat exchanger 16, communicates with the first discharge flow path 14, is opened to the outside through the opening 23a, and merges. A blower fan 18 is provided in the portion 19.

The controller 20 includes a calculation unit (not shown) such as a CPU and a storage unit (not shown) such as a ROM and RAM. Information such as the basic program of the fuel cell system 10 and various fixed data is stored in the storage unit, and the arithmetic unit reads and executes software such as this basic program, so that the controller 20 controls the operation of each unit. To do. The controller 20 may be composed of a single controller 20 for centralized control, or may be composed of a plurality of controllers 20 for distributed control in cooperation with each other.

<Driving method>
The operation method of the fuel cell system 10 will be described with reference to FIGS. 2 and 3. This operation method is controlled by the controller 20. Here, a case where a radiator is used for the heat exchanger 16 will be described.

First, when an anode off-gas discharge (purge) command is output according to the operating state of the fuel cell 11 (step S1: YES), the controller 20 determines whether the amount of air cooled by the blower fan 18 is equal to or greater than the dilution amount. (Step S2). This cooling amount is the air volume of the blower fan 18 required to cool the cooling water in order to cool the fuel cell 11 to a predetermined temperature, and is adjusted based on the temperature detected by the first temperature sensor 17a. The dilution amount is the air volume of the blower fan 18 required to dilute the anode off-gas in order to lower the hydrogen concentration of the discharged anode-off gas below a predetermined value, and is, for example, the maximum air volume.

As the amount of power generated by the fuel cell 11 increases, a higher cooling capacity is required for the cooling water that cools the fuel cell 11, so that the flow rate (cooling amount) of the air that cools the cooling water increases. If this cooling amount becomes equal to or more than the dilution amount (step S2: YES), the dilution amount can be covered by the cooling amount, the cooling water is cooled by the cooling amount of air, and the anode off gas is blown by the cooled air. It can be sufficiently diluted.

Therefore, while sending a cooling amount of air by the blower fan 18, the on-off valve 15 of the first discharge flow path 14 is opened to start purging (step S3). As a result, the first discharge flow path 14 communicates with the confluence portion 19, and the anode off gas discharged from the fuel cell 11 flows out to the confluence portion 19 through the first discharge flow path 14. In the merging portion 19, a cooling amount of air is sent to the heat exchanger 16 by the blower fan 18, and then is discharged to the merging portion 19 through the heat exchanger 16. This air dilutes the anode off-gas, and the hydrogen concentration of the anode-off gas drops below a predetermined value. Then, the diluted anode off-gas flows out from the merging portion 19 through the opening 23a.

When a predetermined condition for discharging the anode off gas from the fuel cell system 10 is satisfied, such as when the elapsed time from the opening of the on-off valve 15 reaches a predetermined time (step S4: YES), the control unit closes the on-off valve 15. (Step S5). As a result, the purging process of the anode off-gas is completed.

On the other hand, in step S2, for example, if the power generation amount of the fuel cell 11 is small and the cooling amount by the blower fan 18 is smaller than the dilution amount (step S2: NO), the dilution amount cannot be covered by the cooling amount. However, since it is necessary to sufficiently dilute the anode off-gas with air, the blower fan 18 must blow the diluted amount when purging the anode off-gas.

Therefore, the controller 20 reduces the air volume of the blower fan 18 before opening the on-off valve 15 to discharge the anode off gas, and when the on-off valve 15 is opened to discharge the anode off gas, the blower fan 18 Increase the air volume of. As a result, it is possible to achieve both dilution of the anode off-gas and temperature control of the fuel cell 11.

That is, normally, as shown in FIG. 3A, when the anode off gas purge command is output at the point A1, the on-off valve 15 of the first discharge flow path 14 is opened to start purging, and the air volume of the blower fan 18 is started. To the dilution amount. Then, the on-off valve 15 is closed at the point A2 to end the purge, and the air volume of the blower fan 18 is reduced to the cooling amount.

In this way, at the start of purging the anode off-gas at point A1, the anode-off gas is discharged to the merging portion 19 through the first discharge flow path 14 by opening the on-off valve 15, and merging due to the increase in the air volume of the blower fan 18. The air volume supplied to the part 19 increases to the dilution amount. As a result, the anode off gas is diluted by the air from the blower fan 18 at the confluence portion 19 and discharged from the confluence portion 19 to the outside.

However, as the air volume of the blower fan 18 increases, the cooling water in the water flow path 17 is cooled in the heat exchanger 16 by the blower of the blower fan 18. As a result, as shown in FIG. 3B, the temperature of the fuel cell 11 cooled by the cooling water becomes lower than the minimum temperature T2 of the target temperature. The target temperature may be, for example, a predetermined temperature according to the amount of power generation of the fuel cell 11, and may be a temperature having a range. In this case, the center temperature T0 of the target temperature is 52 ° C., the maximum temperature T1 of the target temperature is 54 ° C., and the minimum temperature T2 of the target temperature is 50 ° C.

On the other hand, in the fuel cell system 10 shown in FIG. 1, as shown in FIG. 4A, the on-off valve 15 of the first discharge flow path 14 is not opened in response to the purge command of the anode off gas at the point B1. The air volume of the blower fan 18 is reduced from the air volume before the decrease such as the air volume at the time of the purge command (step S6). This decrease in air volume also includes stopping the blower fan 18. As a result, the temperature of the cooling water cooled by the blown air of the blower fan 18 is reduced, so that the cooling capacity of the cooling water for the fuel cell 11 is reduced, and as shown in FIG. 4B, the temperature of the fuel cell 11 is increased. ..

Then, the controller 20 determines whether or not a predetermined condition such as the passage of a predetermined time or reaching the predetermined temperature of the cooling water is satisfied (step S7). This predetermined time is the time until the temperature of the fuel cell 11 reaches the maximum temperature T1 of the predetermined target temperature. Further, the predetermined temperature is a temperature equal to or lower than the maximum temperature T1 of the target temperature.

When the predetermined condition is satisfied (step S7: YES), the controller 20 opens the on-off valve 15 of the first discharge flow path 14 and starts purging (step S8). At the same time as or at the same timing as this, the controller 20 increases the air volume of the blower fan 18 to the dilution amount (step S9). As a result, the air volume of the blower fan 18 is higher than the air volume before the decrease at the point B1 such as the air volume at the time of the purge command, and becomes, for example, the maximum air volume.

As a result, at point B2 in FIG. 4A, the anode off gas is discharged to the confluence 19 through the first discharge flow path 14 by opening the on-off valve 15, and is supplied to the confluence 19 by increasing the air volume of the blower fan 18. The air volume becomes the dilution amount. Therefore, the anode off gas is sufficiently diluted by the air from the blower fan 18 at the merging portion 19, the hydrogen concentration of the anode off gas is lowered, and the anode off gas is discharged to the outside from the merging portion 19.

Further, as shown in FIG. 4B, as the air volume of the blower fan 18 increases, the temperature of the cooling water cooled by the blown air of the blower fan 18 and the temperature of the fuel cell 11 cooled by the cooling water decrease. Here, since the air volume is temporarily reduced before the air volume of the blower fan 18 rises, the temperature of the fuel cell 11 is higher than the target temperature. From here, the fuel cell 11 is cooled to a temperature lower than the target temperature by the large air volume of the blower fan 18. Therefore, since the temperature of the fuel cell 11 moves up and down around the target temperature, it is prevented from falling below the target temperature, and appropriate temperature control of the fuel cell 11 becomes possible.

Then, when it is determined that a desired amount of anode off-gas has been discharged (step S10: YES), such as when a predetermined time has elapsed, the on-off valve 15 is closed at point B3 in FIG. 4A (step S11). As a result, the purging process of the anode off-gas is completed.

On the other hand, if the anode off gas purge command is not output in step S1 (step S1: NO), air is blown according to the temperature of the cooling water by the first temperature sensor 17a so that the temperature of the fuel cell 11 becomes the target temperature. The air volume of the fan 18 is feedback controlled. For example, if the temperature of the fuel cell 11 is the target temperature (step S12: YES), the air volume of the blower fan 18 is maintained at that air volume without being changed, and the process returns to the process of step S1. On the other hand, if the temperature of the fuel cell 11 is lower than the target temperature (step S12: NO, step S13: YES), the blower fan 18 that cools the cooling water in order to reduce the cooling capacity of the cooling water that cools the fuel cell 11. (Step S14). On the other hand, if the temperature of the fuel cell 11 is equal to or higher than the target temperature (step S12: NO, step S13: NO), a blower for cooling the cooling water is used to increase the cooling capacity of the cooling water for cooling the fuel cell 11. The air volume of the fan 18 is increased (step S15). Then, the process returns to the process of step S1.

(Embodiment 2)
In the fuel cell system 10 according to the second aspect of the embodiment of the present invention, the fuel cell system 10 further includes a second supply flow path 24 and a second discharge flow path 25, as shown in FIG.

The second supply flow path 24 is a flow path through which the oxidant gas supplied to the cathode of the fuel cell 11 flows, and is connected to the inlet of the cathode flow path of the fuel cell 11. For example, air can be used as the oxidant gas, and in this case, even if an oxidant gas supply device (not shown) for supplying air to the fuel cell 11 is provided in the second supply flow path 24. Good. For the oxidant gas supply device, for example, a compressor and an electromagnetic induction type diaphragm pump are used. A humidifier for humidifying the oxidant gas may be provided in the second supply flow path 24.

The second discharge flow path 25 is a flow path through which the cathode off gas discharged from the cathode of the fuel cell 11 flows, and is connected to the outlet of the cathode flow path of the fuel cell 11 and communicates with the confluence portion 19. Therefore, the cathode off gas is discharged to the confluence portion 19. As a result, the anode off gas is diluted by the cathode off gas in addition to the air of the blower fan 18 at the confluence portion 19. Therefore, the hydrogen concentration of the anode off-gas is sufficiently lowered to a predetermined value or less, and flows out from the confluence 19 to the outside through the opening 23a.

(Embodiment 3)
In the fuel cell system 10 according to the third aspect of the embodiment of the present invention, the controller 20 increases the air volume of the blower fan 18 when the on-off valve 15 is opened to discharge the anode off-gas, and further opens the on-off valve 15. The air volume of the blower fan 18 is reduced when the anode off gas is stopped from being discharged.

In this case, in the flow shown in FIG. 5, the controller 20 executes each of the processes of steps S1 to S15 shown in FIG. 2, and further reduces the air volume of the blower fan 18 in step S20 after the process of step S11. Perform processing. Since each process of S1 to S15 of FIG. 5 is the same as each process of steps S1 to S15 of FIG. 2, the description thereof will be omitted.

At point B3 in FIG. 4A, the on-off valve 15 is closed (step S11), and at the same time or at the same timing as this, the air volume of the blower fan 18 is reduced to the air volume before purging the anode off gas or to a predetermined air volume. (Step S20). As a result, the temperature of the fuel cell 11 is lowered due to the increase in the air volume of the blower fan 18 when purging the anode off gas at points B2 to B3 in FIG. 4B. On the other hand, since the air volume is reduced after the completion of purging at point B3 in FIG. 4B, the temperature of the fuel cell 11 rises rapidly, and the temperature fluctuation of the fuel cell 11 can be further reduced.

(Embodiment 4)
In the fuel cell system 10 according to the fourth aspect of the embodiment of the present invention, the smaller the output of the fuel cell 11, the longer the time for the controller 20 to reduce the air volume of the blower fan 18 before opening the on-off valve 15. To do.

According to the findings of the inventors, the smaller the output of the fuel cell 11, the smaller the calorific value of the fuel cell 11, so that the temperature responsiveness of the fuel cell 11 when the air volume of the blower fan 18 is reduced decreases.

For example, a second temperature sensor 17b is provided in the water flow path 17 at the outlet of the fuel cell 11, and the cooling water at the outlet of the fuel cell 11 detected by the second temperature sensor 17b is detected. The second circulator 22 is controlled based on the temperature of the second temperature sensor 17b, and the flow rate of the cooling water flowing through the water flow path 17 is adjusted by the second circulator 22. At this time, the smaller the calorific value of the fuel cell 11, the lower the temperature of the cooling water at the outlet of the fuel cell 11, and the lower the flow rate of the cooling water by the second circulator 22. Therefore, since the flow rate of the cooling water is small with respect to the heat capacity of the heat exchanger 16, the temperature response of the heat exchanger 16 is slow, and the temperature response of the outlet of the heat exchanger 16 of the cooling water is also slow. Along with this, the temperature rise rate of the fuel cell 11 also slows down, so that the temperature responsiveness of the fuel cell 11 decreases.

On the other hand, by lengthening the time for lowering the air volume of the blower fan 18, the temperature of the fuel cell 11 is set to a predetermined temperature, for example, at the center temperature T0 or higher and the maximum temperature T1 or lower before purging. Can be raised. As a result, the air volume of the blower fan 18 is increased during purging, and even when the temperature of the cooling water due to the blower of the blower fan 18 drops, the temperature of the fuel cell 11 cooled by the cooling water is set to the minimum temperature T2 or higher of the target temperature. Can be stored in. In this way, the temperature fluctuation of the fuel cell 11 can be reduced.

(Embodiment 5)
In the fuel cell system 10 according to the fifth aspect of the embodiment of the present invention, the controller 20 controls the air volume of the blower fan 18 by the rotation speed of the blower fan 18. The relationship between the air volume and the number of revolutions is predetermined by a relational expression, a map, or the like. As a result, the air volume of the blower fan 18 is directly adjusted by the rotation speed, so that a desired air volume can be immediately generated, so that more appropriate temperature control can be performed.

(Other embodiments)
In addition, all the above-described embodiments may be combined with each other as long as the other party is not excluded from each other. For example, in the fuel cell system 10 according to the second aspect of the embodiment, the controller 20 may be controlled in the same manner as in the third, fourth and / or fifth aspects of the embodiment. Further, in the fuel cell system 10 according to the third embodiment, the controller 20 may be controlled in the same manner as in the fourth and / or fifth embodiment. Further, in the fuel cell system 10 according to the fourth embodiment, the controller 20 may be controlled in the same manner as in the fifth embodiment.

From the above description, many improvements and other embodiments of the present invention will be apparent to those skilled in the art. Therefore, the above description should be construed as an example only and is provided for the purpose of teaching those skilled in the art the best aspects of carrying out the present invention. The details of its structure and / or function can be substantially changed without departing from the spirit of the present invention.

The fuel cell system of the present invention is useful as a fuel cell system that achieves both dilution of anode off-gas and temperature control of the fuel cell.

10: Fuel cell system 11: Fuel cell 12: First supply flow path 13: Recycling flow path 14: First discharge flow path 15: On-off valve 16: Heat exchanger 17: Water flow path 18: Blower fan 19: Confluence part 20 : Controller 21: 1st circulator 22: 2nd circulator 24: 2nd supply flow path 25: 2nd discharge flow path

Claims (4)

A fuel cell that generates electricity using fuel gas and oxidant gas,
A supply flow path through which the fuel gas supplied to the anode of the fuel cell flows, and
A recycling flow path through which the anode off gas discharged from the anode flows and is connected to the supply flow path, and a recycling flow path.
A discharge channel that branches off from the recycling channel and through which the anode off-gas flows.
An on-off valve provided in the discharge flow path and
A heat exchanger that exchanges heat between the cooling water that cools the fuel cell and air,
A water flow path in which the cooling water circulates between the fuel cell and the heat exchanger, and
A blower fan that sends the air to the heat exchanger,
A confluence portion where the anode off gas discharged from the discharge flow path and the air passing through the heat exchanger merge and are discharged to the outside.
With a controller,
The controller reduces the air volume of the blower fan before opening the on-off valve and discharging the anode off gas, and reduces the air volume of the blower fan when the on-off valve is opened and the anode off gas is discharged. Increasing fuel cell system. The supply flow path is the first supply flow path.
The discharge flow path is the first discharge flow path.
A second supply flow path through which the oxidant gas supplied to the cathode of the fuel cell flows, and
A second discharge flow path through which the cathode off gas discharged from the cathode flows is further provided.
The fuel cell system according to claim 1, wherein the anode off gas, the air, and the cathode off gas discharged from the second discharge flow path merge at the merging portion and are discharged to the outside. The controller increases the air volume of the blower fan when the on-off valve is opened to discharge the anode off-gas, and further closes the on-off valve to stop the discharge of the anode-off gas. The fuel cell system according to claim 1 or 2, which reduces the air volume of the fuel cell system. The fuel according to any one of claims 1 to 3, wherein the controller increases the time for reducing the air volume of the blower fan before opening the on-off valve as the output of the fuel cell becomes smaller. Battery system.

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