FUEL CELL ANODE STOICHIOMETRIC CONTROL

PROBLEM TO BE SOLVED: To provide a system and method for controlling an anode exhaust gas bleed valve in a fuel cell system. SOLUTION: This system and method estimates a gas composition in an anode exhaust gas, uses an inverse valve model to calculate a desired valve flow coefficient, and bleeds the anode exhaust gas at a flow resulting in a desired valve flow coefficient. This method determines the partial pressure of nitrogen in the anode exhaust gas, calculates the partial pressures of water vapor and hydrogen in the anode exhaust gas, and calculates the gas mol fractions of nitrogen, water vapor and hydrogen in the anode exhaust gas. In addition, this method uses the gas mol fractions of nitrogen, water vapor and hydrogen to determine a desired valve flow coefficient, and uses the desired valve flow coefficient to determine a timing for opening or closing the bleed valve. COPYRIGHT: (C)2008,JPO&INPIT