FIELD

The present disclosure relates to a fuel cell system comprising a fuel cell stack configured to electrochemically react hydrogen and oxygen so as to generate electricity, a hydrogen circulation passage through which anode waste gas discharged from the fuel cell stack is circulated, a hydrogen circulation pump provided at the hydrogen circulation passage, and a discharge valve configured to discharge anode waste gas to outside, to a control method of a fuel cell system, and to a computer program for executing control processing of a fuel cell system.

BACKGROUND AND SUMMARY

Some of fuel cell systems that obtain electromotive force by an electrochemical reaction of hydrogen and oxygen are provided with a hydrogen circulation passage through which anode waste gas discharged from an anode of a fuel cell stack is circulated, so that residual hydrogen included in the anode waste gas is effectively used. Regarding such a fuel cell system, anode waste gas includes impurities such as nitrogen or water vapor, and therefore the concentration of such impurities may possibly increase at an anode, the hydrogen concentration may possibly relatively decrease, and the performance of the fuel cell stack may possibly deteriorate as the anode waste gas is circulated and power generation is continued. Therefore, a technique for suppressing deterioration in the performance of the fuel cell stack has been known in which a discharge valve for discharging a part of anode waste gas to outside is provided at a hydrogen circulation passage, and the impurities are discharged to outside by periodically putting the discharge valve into an open state.

Moreover, water is generated at a cathode of the fuel cell stack. When generated water passes through an electrolyte membrane under osmotic pressure or a concentration difference, infiltrates to the anode side, and is stored on the anode side, a so-called flooding phenomenon in which water stays may possibly occur, and the power generation performance of the fuel cell stack may possibly deteriorate.

In order to solve such problems, a technique for suppressing deterioration in the performance of a stack has been known in which a discharge valve provided at a hydrogen circulation passage is periodically opened so that impurities such as nitrogen or water vapor and water are discharged to outside.

An example of a conventional fuel cell system is provided with an air discharge valve and a water discharge valve that are discharge valves at anode off-gas piping and corrects the open time of the air discharge valve and the open time of the water discharge valve based on the atmospheric pressure. The conventional fuel cell system, however, disregards the relation between the opening/closing timing of the air discharge valve and the opening/closing timing of the water discharge valve.

In the case of such a hydrogen circulation type fuel cell system provided with an air discharge valve and a water discharge valve, the pressure in the hydrogen circulation passage normally lowers when the air discharge valve or the water discharge valve is put into an open state. For example, when the air discharge valve is put into an open state while the water discharge valve is in an open state, the internal pressure lowers, water discharge may possibly become insufficient, and it may possibly become impossible to discharge a required amount of water. On the contrary, in a case where the water discharge valve is put into an open state while the air discharge valve is in an open state, the internal pressure also lowers, and air discharge may also possibly become insufficient.

An object of the present disclosure is to provide a fuel cell system that can suppress lowering of the internal pressure by controlling the timing of putting an air discharge valve into an open state and the timing of putting a water discharge valve into an open state and sufficiently discharge impurities at the time of air discharge or water discharge.

In the present disclosure, the fuel cell system comprises a fuel cell stack configured to react hydrogen and oxygen so as to generate electricity, a hydrogen supply passage for supplying hydrogen to the fuel cell stack, a hydrogen circulation passage for returning anode waste gas discharged from an anode of the fuel cell stack to the hydrogen supply passage, a hydrogen circulation pump that is provided at the hydrogen circulation passage, has an inlet and an outlet, and operates to circulate the anode waste gas, a waste gas discharge passage for discharging the anode waste gas to outside, the waste gas discharge passage being branched from a part of the hydrogen circulation passage between the anode and the inlet of the hydrogen circulation pump, a first discharge valve configured to put the waste gas discharge passage into an open state or a close state, a gas-liquid separator that is disposed at the hydrogen circulation passage and can separate a water component included in the anode waste gas, a water discharge passage for discharging the water component separated by the gas-liquid separator to outside, the water discharge passage being connected with the gas-liquid separator, a second discharge valve configured to put the water discharge passage into an open state or a close state, and a control unit configured to switch the first discharge valve and the second discharge valve into an open state or a close state, and the control unit performs control to deviate a period when the first discharge valve is in an open state and a period when the second discharge valve is in an open state from each other.

In the present disclosure, a control method of controlling a first discharge valve and a second discharge valve by a control unit of a fuel cell system is disclosed and the fuel cell system comprises a fuel cell stack configured to react hydrogen and oxygen so as to generate electricity, a hydrogen supply passage for supplying hydrogen to the fuel cell stack a hydrogen circulation passage for returning anode waste gas discharged from an anode of the fuel cell stack to the hydrogen supply passage a hydrogen circulation pump that is provided at the hydrogen circulation passage, has an inlet and an outlet, and operates to circulate the anode waste gas, a waste gas discharge passage for discharging the anode waste gas to outside, the waste gas discharge passage being branched from a part of the hydrogen circulation passage between the anode and the inlet of the hydrogen circulation pump, a first discharge valve configured to put the waste gas discharge passage into an open state or a close state, a gas-liquid separator that is disposed at the hydrogen circulation passage and can separate a water component included in the anode waste gas, a water discharge passage for discharging the water component separated by the gas-liquid separator to outside, the water discharge passage being connected with the gas-liquid separator, a second discharge valve configured to put the water discharge passage into an open state or a close state and the control unit configured to control the first discharge valve and the second discharge valve. The control unit performs control to deviate a period when the first discharge valve is in an open state and a period when the second discharge valve is in an open state from each other.

In the present disclosure, a non-transitory computer-readable recording medium recoding a computer program of a control unit of a fuel cell system comprising, a fuel cell stack configured to react hydrogen and oxygen so as to generate electricity, a hydrogen supply passage for supplying hydrogen to the fuel cell stack, a hydrogen circulation passage for returning anode waste gas discharged from an anode of the fuel cell stack to the hydrogen supply passage, a hydrogen circulation pump that is provided at the hydrogen circulation passage, has an inlet and outlet, and operates to circulate the anode waste gas, a waste gas discharge passage for discharging the anode waste gas to outside, the waste gas discharge passage being branched from a part of the hydrogen circulation passage between the anode and the inlet of the hydrogen circulation pump, a first discharge valve configured to put the waste gas discharge passage into an open state or a close state, a gas-liquid separator that is disposed at the hydrogen circulation passage and can separate a water component included in the anode waste gas, a water discharge passage for discharging the water component separated by the gas-liquid separator to outside, the water discharge passage being connected with the gas-liquid separator, and a second discharge valve configured to put the water discharge passage into an open state or a close state. The control unit switches the first discharge valve and the second discharge valve into an open state or a close state, and the computer program causes the control unit to execute a process of performing control to deviate a period when the first discharge valve is in an open state and a period when the second discharge valve is in an open state from each other.

The above and further objects and features will more fully be apparent from the following detailed description with accompanying drawings.

