Fuel cell system

Patent metadata

Field	Value
Publication number	US-10581096-B2
Application number	US-201314407272-A
Country	US
Kind code	B2
Filing date	Jun 14, 2013
Priority date	Jun 15, 2012
Publication date	Mar 3, 2020
Grant date	Mar 3, 2020

Abstract

A fuel cell system calculates a target value of a flow rate of cathode gas to be supplied to a fuel cell stack according to a request of the fuel cell stack, controls a flow rate of the cathode gas to be supplied by the compressor according to an operating state of the fuel cell system, controls a bypass valve based on a target fuel cell supply flow rate so that the flow rate of the cathode gas to be supplied from the compressor to the fuel cell stack reaches the target fuel cell supply flow rate, and limits the flow rate of the cathode gas to be supplied by the compressor when the bypass valve has a predetermined opening and the flow rate of the cathode gas to be supplied to the fuel cell stack is not smaller than the target fuel cell supply flow rate.

First claim

The invention claimed is:

1. A fuel cell system for generating power by supplying anode gas and cathode gas to a fuel cell stack, comprising:
a compressor configured to supply the cathode gas;
a bypass passage configured to discharge a part of the cathode gas discharged from the compressor to a cathode gas discharge passage while bypassing the fuel cell stack;
a bypass valve provided in the bypass passage and configured to adjust a bypass flow rate of the cathode gas flowing in the bypass passage; and
a controller programmed to:
calculate a power generation request stack supply flow rate of the cathode gas to be supplied to the fuel cell stack required by a load of the fuel cell stack and calculate a wetness request stack supply flow rate required to maintain electrolyte wetness and select a larger of the power generation request stack supply flow rate and the wetness request stack supply flow rate as a target value of the stack supply flow rate;
calculate a stack request compressor supply flow rate from an actual stack supply flow rate and the target value of the stack supply flow rate;
select a provisional target value of the compressor supply flow rate of the cathode gas to be supplied by the compressor as a larger of the stack request compressor supply flow rate and a dilution request compressor supply flow rate, the dilution request compressor supply flow rate determined as a flow necessary to set a hydrogen concentration in an exhaust gas to at or below a predetermined concentration;
control the bypass valve based on the target value of the stack supply flow rate so that an actual value of the stack supply flow rate of the cathode gas to be supplied by the compressor to the fuel cell stack reaches the target value of the stack supply flow rate;
calculate a compressor limiting flow rate using the wetness request stack supply flow rate and an estimated value of the bypass flow rate determined if the bypass valve is fully opened and using atmospheric pressure, a stack inlet pressure, and a discharge temperature;
select a target compressor supply flow rate from a smaller of the provisional target value and the compressor limiting flow rate; and
control the compressor so as to limit the compressor supply flow rate of the cathode gas supplied by the compressor to the target compressor supply flow rate.

2. The fuel cell system according to claim 1 , wherein the controller is further programmed to:
calculate the compressor limiting flow as a sum of the wetness request stack supply flow rate and the estimated value of the bypass flow rate.

3. The fuel cell system according to claim 1 , wherein the wetness request stack supply flow rate of the cathode gas required to be supplied to the fuel cell stack is calculated from a required degree of wetness and an actual degree of wetness so that the actual degree of wetness of electrolyte membranes of the fuel cell stack reaches the required degree of wetness.

4. A control method of fuel cell system for generating power by supplying anode gas and cathode gas to a fuel cell stack, the fuel cell system comprising:
a compressor configured to supply the cathode gas;
a bypass passage configured to discharge a part of the cathode gas discharged from the compressor to a cathode gas discharge passage while bypassing the fuel cell stack; and
a bypass valve provided in the bypass passage and configured to adjust a bypass flow rate of the cathode gas flowing in the bypass passage, wherein
the control method comprises:
a step of calculating a power generation request stack supply flow rate of the cathode gas to be supplied to the fuel cell stack required by a load of the fuel cell stack and calculating a wetness request stack supply flow rate required to maintain electrolyte wetness and selecting a larger of the power generation request stack supply flow rate and the wetness request stack supply flow rate as a target value of the stack supply flow rate;
a step of calculating a stack request compressor supply flow rate from an actual stack supply flow rate and the target value of the stack supply flow rate;
a step of selecting a provisional target value of the compressor supply flow rate of the cathode gas to be supplied by the compressor as a larger of the stack request compressor supply flow rate and a dilution request compressor supply flow rate, the dilution request compressor supply flow rate determined as a flow necessary to set a hydrogen concentration in an exhaust gas to at or below a predetermined concentration;
a step of controlling the bypass valve based on the target value of the stack supply flow rate so that an actual value of the stack supply flow rate of the cathode gas to be supplied by the compressor to the fuel cell stack reaches the target value of the stack supply flow rate;
a step of calculating a compressor limiting flow rate using the wetness request stack supply flow rate and an estimated value of the bypass flow rate determined if the bypass valve is fully opened and using atmospheric pressure, a stack inlet pressure, and a discharge temperature;
a step of selecting a target compressor supply flow rate from rate from a smaller of the provisional target value and the compressor limiting flow rate; and
a step of controlling the compressor so as to limit the compressor supply flow rate of the cathode gas supplied by the compressor to the target compressor supply flow rate.

5. The method of claim 4 , further comprising:
a step of calculating the compressor limiting flow rate as a sum of the wetness request stack supply flow rate and the estimated value of the bypass flow rate.

6. The method of claim 4 , further comprising:
a step of calculating the wetness request stack supply flow rate of the cathode gas required to be supplied to the fuel cell stack from a required degree of wetness and an actual degree of wetness so that the actual degree of wetness of electrolyte membranes of the fuel cell stack reaches the required degree of wetness.

Assignees

• Nissan Motor

Inventors

• Tomita Yousuke
• Chikugo Hayato

Classifications

• H01M8/04432

  Pressure differences, e.g. between anode and cathode · CPC title

• H01M8/0438

  Pressure; Ambient pressure; Flow · CPC title

• H01M8/04291 Primary

  Arrangements for managing water in solid electrolyte fuel cell systems (H01M8/04119 takes precedence) · CPC title

• H01M8/0435

  of cathode exhausts · CPC title

• H01M8/04753

  of fuel cell reactants · CPC title