Fuel cell system and its control method

Patent metadata

Field	Value
Publication number	US-2022336831-A1
Application number	US-201917762567-A
Country	US
Kind code	A1
Filing date	Sep 24, 2019
Priority date	Sep 24, 2019
Publication date	Oct 20, 2022
Grant date	—

Abstract

A fuel cell system that raises temperature of fuel cells by supplying heated air to the fuel cells during starting up period. The fuel cell system includes a plurality of fuel cells, a fuel supply path connected parallelly to the fuel cells to provide fuel thereto, an air supply path connected serially to the fuel cells to provide air thereto, a heat exchanger arranged in the fuel supply path to heat air or fuel, an air heat exchanger arranged in the air supply path to heat air; and a connection path connecting a position of the air supply path upstream to the air heat exchanger with a position of the fuel supply path upstream to the heat exchanger. A first control valve is arranged in the air supply path for controlling the air flowing into to the air heat exchanger. A second control valve arranged in the connection path for controlling the air flowing into the heat exchanger. The fuel cell system controls opening degrees of the first and second control valves during the start-up period of the fuel cell system to supply heated air to the fuel cells through both the air supply path and the fuel supply path.

First claim

1 . A fuel cell system configured to warm up a fuel cell by providing heated air thereto during a start-up period, comprising:
a plurality of fuel cells; a fuel supply path connected parallelly to the fuel cells to provide fuel thereto; an air supply path connected serially to the fuel cells to provide air thereto; a heat exchanger arranged in the fuel supply path to heat air or fuel; an air heat exchanger arranged in the air supply path to heat air; and a connection path connecting a position of the air supply path upstream to the air heat exchanger with a position of the fuel supply path upstream to the heat exchanger, and wherein a first control valve is arranged in the air supply path, the first control valve controlling air flowing into the air heat exchanger, a second control valve is arranged in the connection path, second control valve controlling air flowing into the heat exchanger, and the fuel cell system is configure to control opening degrees of the first and second control valves during the start-up period of the fuel cell system to supply heated air to the fuel cells through both the air supply path and the fuel supply path.

2 . A fuel cell system according to claim 1 , wherein
the fuel cell system, during the start-up period, is configured to control supply of the heated air provided to the fuel cells through the air supply path and the fuel supply path by adjusting the opening degrees of the first and second control valves based on temperatures of the fuel cells.

3 . A fuel cell system according to claim 1 , further comprising:
a bypass branching off from a position in the connection path or the air supply path, the position being upstream of the air heat exchanger, wherein the bypass is provided with a third control valve for controlling supply of the air, the air being supplied to the fuel cells without passing through the air heat exchanger during the start-up period of the fuel cell system.

4 . A fuel cell system according to claim 3 , further configured to:
up until the time a first fuel cell reaches a prescribed temperature during the start-up period of fuel cell system,
control the opening degrees of the first and second control valve so that a temperature increasing rate of the first fuel cell becomes highest in the fuel cells, the first fuel cell being arranged closest to the air heat exchanger in the fuel cells; and
from the time when the temperature of the first cell has reached the prescribed temperature, control the opening degree of the third control valve in a way so as to maintain a heat dissipation from the first fuel cell to the air flowing in from the air supply path is equal to, or greater than a heating amount provided to the first fuel cell by the air flowing in from the fuel supply path.

5 . A fuel cell system according to claim 3 , further configured to:
up until the time when the first fuel cell located closest to the air heat exchanger reaches a prescribed temperature during the start-up period of fuel cell system,
If a heat input to the heat exchanger is greater than the heat input to the air heat exchanger,
control the opening degrees of the first and second control valves in a way so as to maintain an air supply ratio equal to, or greater than a value calculated by dividing number of fuel cells by a heat input ratio, the air supply ratio being an air amount supplied to the air heat exchanger divided by a total air amount supplied to the heat exchanger and the air heat exchanger, the heat input ratio being the heat input to the heat exchanger divided by a total heat input to the heat exchanger and the air heat exchanger;
If the heat input to the heat exchanger is smaller than heat input to the air heat exchanger,
control the opening degrees of the first and second control valves in a way so as to maintain the air supply ratio equal to, or greater than the heat input ratio, which is the heat input to the heat exchanger divided by a total heat input to the heat exchanger and the air heat exchanger; and
from the time when the temperature of the first cell has reached the prescribed temperature,
control the degree of opening of the third control valve in a way so as to maintain a heat dissipation from the first fuel cell to the air supplied from the air supply path is equal to, or greater than a heating amount provided by the air supplied from the fuel supply path to the first fuel cell.

6 . A fuel cell system according to claim 4 , further configured to control the opening degrees of the first, second, and third control valves to maintain the following two values mutually equal:
the air supply ratio of the heat exchanger divided by a total air amount supplied into the heat exchanger and the air heat exchanger under condition that the air heat exchanger with the control valve is closed; and the air supply ratio of the heat exchanger divided by the total air amount supplied into the heat exchanger, the air heat exchanger, and the bypass under condition that the control valve is opened.

7 . A fuel cell system according to claim 4 , further configured to,
up until the time when the first fuel cell reaches the prescribed temperature during the start-up period of the fuel cell system, control the opening degrees of the first and second control valves to minimize a total pressure loss, which is sum of an air pressure loss due to the fuel supply path and the air pressure loss due to the air supply path.

8 . A control method of a fuel cell system having
a plurality of fuel cells, a fuel supply path connected parallelly to the fuel cells to provide fuel thereto, an air supply path connected serially to the fuel cells to provide air thereto, a heat exchanger arranged in the fuel supply path to heat air or fuel, an air heat exchanger arranged in the air supply path to heat air, and a connection path connecting a position of the air supply path upstream to the air heat exchanger with a position of the fuel supply path upstream to the heat exchanger, a first control valve arranged in the air supply path, the first control valve controlling air flowing into the air heat exchanger, a second control valve arranged in the connection path, second control valve controlling air flowing into the heat exchanger, and wherein during a start-up period of the fuel cell system, the first and the second control valves are opened to allow both the air supply path and the fuel supply path to supply heated air to the fuel cells to raise the temperatures thereof.

Assignees

• Nissan Motor

Inventors

• Ikeguchi Ken Bryan
• Chikugo Hayato

Classifications

• H01M2008/1293

  Fuel cells with solid oxide electrolytes · CPC title

• H01M8/0618

  Reforming processes, e.g. autothermal, partial oxidation or steam reforming · CPC title

• H01M8/04776

  at auxiliary devices, e.g. reformer, compressor, burner · CPC title

• H01M8/04753

  of fuel cell reactants · CPC title

• H01M8/04731

  of other components of a fuel cell or fuel cell stacks · CPC title