INCORPORATION BY REFERENCE

The disclosure of Japanese Patent Application No. 2018-211409 filed on Nov. 9, 2018 including the specification, drawings and abstract is incorporated herein by reference in its entirety.

BACKGROUND

1. Technical Field

The present disclosure relates to a fuel cell system.

2. Description of Related Art

When electric power generation stops while liquid water remains in a fuel cell, circulation of reactant gas may be hindered next time the electric power generation is started. Accordingly, a technique for scavenging the fuel cell to discharge liquid water from the fuel cell is known. For example, in Japanese Patent Application Publication No. 2008-192614, a fuel cell is scavenged by an injector injecting anode gas while electric power generation in the fuel cell is stopped.

SUMMARY

In order to sufficiently scavenge a fuel cell, it is desirable to inject a large amount of anode gas from an injector. Accordingly, there is a fuel cell system including a circulation passage for circulating the anode gas discharged from the fuel cell to the fuel cell again. When a large amount of anode gas is injected in such a system for the purpose of scavenging, the anode gas may remain without being consumed since electric power generation of the fuel cell is stopped. Consequently, the pressure inside the circulating passage may rise, as a result of which the pressure inside the fuel cell may become high enough to affect the fuel cell. Therefore, in the fuel cell system including a circulation passage for circulating anode gas, it may be hard to sufficiently scavenge the fuel cell, since scavenging can be performed only in the range where the pressure of the fuel cell does not become too high.

The present disclosure provides a fuel cell system capable of sufficiently scavenging the fuel cell.

An aspect of the present disclosure relates to a fuel cell system including: first and second fuel cells; first and second injectors; first and second ejectors; a first circulation passage; a second circulation passage; a communication passage; a switching valve; and a controller. The first and second injectors are configured to inject anode gas to be supplied to the first and second fuel cells. The first and second ejectors are configured to allow the anode gas injected from the first and second injectors to pass through the first and second ejectors respectively. The first circulation passage is configured to circulate the anode gas that has passed the first ejector between the first fuel cell and the first ejector. The second circulation passage is configured to circulate the anode gas that has passed the second ejector between the second fuel cell and the second ejector. The communication passage communicates with the first and second circulation passages. The switching valve is configured to be opened and closed to switch the communication passage to a communication state where the first and second circulation passages communicate with each other or to a cutoff state where the first and second circulation passages are cut off. The controller is configured to scavenge the first fuel cell by injecting the anode gas with the first injector, while the first fuel cell stops electric power generation in the communication state.

Since the first and second circulation passages communicate with each other, the anode gas injected by the first injector flows not only to the first circulation passage and the inside of the first fuel cell, but also to the second circulation passage and the inside of the second fuel cell. This makes it possible to restrain a rising speed of pressure inside the first fuel cell caused by injection of the anode gas from the first injector. Accordingly, the amount of anode gas supplied into the first fuel cell can be secured to achieve sufficient scavenging of the first fuel cell.

The controller may be configured to scavenge the first fuel cell, while the second fuel cell generates electric power in the communication state.

The controller may be configured to scavenge the first fuel cell, while the second fuel cell generates electric power in the communication state, with driving of the second injector being stopped.

The fuel cell system may include first and second exhaust valves communicating with the first and second circulation passages through outside air, respectively. The controller may be configured to scavenge the first fuel cell, while at least one of the first and second exhaust valves is opened in the communication state.

The controller may be configured to scavenge the first fuel cell, while the second fuel cell generates electric power in the communication state, with the second exhaust valve being opened.

The fuel cell system may include a first gas-liquid separator configured to allow the anode gas discharged from the first fuel cell to pass through the first gas-liquid separator until the anode gas reaches the first ejector. The communication passage may have a first end portion connected between the first gas-liquid separator and the first ejector in the first circulation passage.

The controller may be configured to scavenge the second fuel cell by injecting the anode gas with the second injector, while the second fuel cell stops the electric power generation in the communication state.

The fuel cell system may include a second gas-liquid separator configured to allow the anode gas discharged from the second fuel cell to pass through the second gas-liquid separator until the anode gas reaches the second ejector. The communication passage may have a second end portion connected between the second gas-liquid separator and the second ejector in the second circulation passage.

The fuel cell system capable of sufficiently scavenging the fuel cell can be provided.

