Patent ID: 7537848
Filing Date: 2009-05-26
Classification: H01M,Y02E,Y02P

Abstract:
1. A fuel cell system comprising: a fuel cell stack including a cathode side and an anode side; a compressor providing an airflow to the cathode side of the fuel cell stack; a bleed valve for periodically bleeding anode exhaust gas from the anode side of the stack; a mixing junction for mixing a cathode exhaust gas and the bled anode exhaust gas during the bleed; and a controller for controlling the compressor and the bleed valve so that the concentration of hydrogen in the mixed anode and cathode exhaust gas is below a predetermined percentage, said controller using a valve orifice model to calculate the flow rate of the anode exhaust gas through the bleed valve to identify how much airflow from the compressor is required to dilute the hydrogen in the anode exhaust gas to be below the predetermined percentage.