Anode Bleed Control Strategy for Improved Water Management and Hydrogen Utilization

• US 20080312849A1
• Filed: 06/15/2007
• Published: 12/18/2008
• Est. Priority Date: 06/15/2007
• Status: Active Grant

• Current Assignee: GM Global Technology Operations LLC (General Motors Company)
• Original Assignee: GM Global Technology Operations Incorporated (Motors Liquidation Co. GUC Trust)
• Inventors: Sienkowski, Jon R., Lakshmanan, Balasubramanian, Gade, Prasad, Sinha, Manish
• Granted Patent: US 8,855,942 B2
• Time in Patent Office: Days
• US Class Current: 702/47
• CPC Class Codes: H01M 8/04231 Purging of the reactants
• CPC Class Codes: H01M 8/04462 of anode exhausts
• CPC Class Codes: H01M 8/04761 of fuel cell exhausts
• CPC Class Codes: H01M 8/04992 characterised by the implementation of mathematical or computational algorithms, e.g. feedback control loops, fuzzy logic, neural networks or artificial intelligence
• CPC Class Codes: Y02E 60/50 Fuel cells

Abstract

A control strategy for bleeding an anode side of fuel cell stack in a fuel cell system that improves water management and addresses durability and performance concerns. The method includes determining when to begin the anode bleed, typically by estimating or measuring the amount of nitrogen in the anode side of the stack. The method also includes determining when to end the anode bleed based on the volume of gas that has been bled. The method determines the mole flow rate of the anode gas flowing through a bleed valve, integrates the mole flow rate to get the number of moles of the gas that have passed through the bleed valve, determines a desired amount of moles to be bled, and ends the bleed when the actual number of moles of the gas equals the desired number of moles of the gas.

Claims

1. A method for determining when to bleed an anode of a fuel cell stack, said method comprising:

determining when to start the anode bleed; and

determining when to end the anode bleed based on determining the volume of anode gas that has already been bled during the bleed event.

2. The method according to claim 1 wherein determining when to end the anode bleed includes determining the mole flow rate of the anode gas through a bleed valve, integrating the mole flow rate to get the number of moles of the gas that have passed through the bleed valve, determining a desired amount of moles of the gas to be bled, and ending the bleed when the actual number of moles of the gas that have passed through the bleed valve equals the desired number of moles of the gas to be bled.

3. The method according to claim 2 wherein determining the mole flow rate of the anode gas through the bleed valve includes using the equation:

4. The method according to claim 2 wherein determining the desired amount of moles to be bled includes determining and using an anode residence time scaling factor that defines a number of anode volumes.

5. The method according to claim 4 wherein determining the desired amount of moles to be bled includes using the equation:

6. The method according to claim 4 wherein the scaling factor is determined by experimentation.

7. The method according to claim 1 wherein determining when to begin the anode bleed includes determining the concentration of nitrogen in the anode side of the fuel cell stack using a nitrogen estimating model.

8. The method according to claim 1 wherein determining when to begin the anode side bleed includes measuring the concentration of nitrogen in the anode side of the fuel cell stack.

9. The method according to claim 1 wherein the fuel cell stack includes a first split stack and a second split stack that employ anode flow-shifting.

10. A method for controlling an anode bleed from first and second split fuel cell stacks that operate under anode flow-shifting through first and second bleed valves, said method comprising:

determining when to start the anode bleed;

determining the mole flow rate of the anode gas flowing through the bleed valves;

integrating the mole flow rate to get the number of moles of the gas that have passed through the bleed valves;

determining a desired amount of moles to be bled; and

ending the anode bleed when the actual number of moles of the gas that have passed through the bleed valves equals the desired number of moles of the gas to be bled.

11. The method according to claim 10 wherein determining the mole flow rate of the anode gas through the bleed valves includes using the equation:

12. The method according to claim 10 wherein determining the desired amount of moles to be bled includes determining and using an anode residence time scaling factor that defines a number of anode volumes.

13. The method according to claim 12 wherein determining the desired amount of moles to be bled includes using the equation:

14. The method according to claim 12 wherein the scaling factor is determined by experimentation.

15. The method according to claim 10 wherein determining when to begin the anode bleed includes determining the concentration of nitrogen in the anode side of the fuel cell stack using a nitrogen estimating model.

16. The method according to claim 10 wherein determining when to begin the anode side bleed includes measuring the concentration of nitrogen in the anode side of the split stacks.

17. A method for controlling an anode bleed from first and second split fuel cell stacks that operate under anode flow-shifting through first and second bleed valves, said method comprising:

determining when to start the anode bleed based on the concentration of nitrogen in the anode of the split stacks; and

determining when to end the anode bleed based on an anode time residence model that identifies the number of volumes of anode gas to be bled.

18. The method according to claim 17 wherein determining when to end the anode bleed includes determining the mole flow rate of the anode gas through the bleed valves, integrating the mole flow rate to get the number of moles of the gas that have passed through the bleed valves, determining a desired amount of moles of the gas to be bled, and ending the bleed when the actual number of moles of the gas that have passed through the bleed valves equals the desired number of moles of the gas to be bled.

19. The method according to claim 18 wherein determining the mole flow rate of the anode gas through the bleed valves includes using the equation:

20. The method according to claim 18 wherein determining the desired amount of moles to be bled includes using the equation: