Abstract: A system and method for a cathode subsystem in a fuel cell system. The system includes a fuel cell stack, a cathode inlet line that provides cathode air to a fuel cell stack and a cathode exhaust line that exhausts a cathode exhaust gas out of the fuel cell stack. Also included is a backpressure valve in the cathode exhaust line that is located downstream of a drip rail of the cathode exhaust line, where the drip rail includes a protrusion that prevents condensed water from building up near the backpressure valve. The drip rail further includes a sump that collects drips of condensed water from the protrusion of the drip rail. The system also includes a drain below a water vapor transfer unit that includes an orifice that is in a portion of the drain that is within the cathode exhaust line.

Abstract: A method for shutting down a fuel cell system including operating a fuel cell stack. the method includes providing an increased cathode air flow so as to dry fuel cell membranes in the stack until a first desired level of high frequency resistance is achieved, rehydrating the cell membranes of the stack until a second desired level of high frequency resistance is achieved, and operating the stack with a decreased cathode input relative humidity until a third desired level of high frequency resistance is achieved.

Abstract: A system and method for a cathode subsystem in a fuel cell system. The system includes a fuel cell stack, a cathode inlet line that provides cathode air to a fuel cell stack and a cathode exhaust line that exhausts a cathode exhaust gas out of the fuel cell stack. Also included is a backpressure valve in the cathode exhaust line that is located downstream of a drip rail of the cathode exhaust line, where the drip rail includes a protrusion that prevents condensed water from building up near the backpressure valve. The drip rail further includes a sump that collects drips of condensed water from the protrusion of the drip rail. The system also includes a drain below a water vapor transfer unit that includes an orifice that is in a portion of the drain that is within the cathode exhaust line.

Abstract: A method for purging water from a fuel cell stack at fuel cell system shutdown. The method includes determining a stack water generation request to control the rate of drying of membranes in the stack and determining a cathode catalytic heating water generation request. A maximum charge a battery in the fuel cell system can accept is also determined. An ancillary power request for powering components of the fuel cell system during shutdown is determined. The method allocates how much of the water generation request will be fulfilled by operating the fuel cell stack to charge the battery and to provide the power needed for the ancillary power request, and how much of the water generation request will be fulfilled by cathode catalytic heating that produces water and heat in a cathode side of the fuel cell stack.

Abstract: A valve for a fuel cell system includes a valve housing having a valve seat formed therein. The valve seat includes an orifice formed therein to permit a fluid to flow through the valve housing. A movable member is disposed in the valve housing and is movable between an open position and a closed position. The movable member includes a first end having an elongate portion and a generally conical shaped base. At least a portion of the base is disposed in the orifice of the valve seat when the movable member is in the closed position to militate against a formation of ice across the orifice of the valve seat.

Abstract: A system and method for selectively determining whether a freeze purge should be performed at shut-down of a fuel cell stack. The method includes identifying that the vehicle has been keyed off and then determining whether a stack membrane humidification value is less than a predetermined humidification value that identifies the humidification of membranes in fuel cells in the fuel cell stack. If the stack membrane humidification value is not less than the predetermined humidification value, then the method determines if the ambient temperature is below a predetermined ambient temperature, and if so, performs the freeze purge. If the ambient temperature is not below the predetermined ambient temperature, then the method performs a short non-freeze purge of the flow channels in the fuel cell stack. The method determines a wake-up time for a controller for a next time to determine whether a freeze purge should be performed.

Abstract: A method for increasing the temperature of a cooling fluid used to control the temperature of a fuel cell stack at a system freeze start-up. The method includes determining that the cooling fluid is frozen or nearly frozen, and if so, deactivating excessive power draw on the fuel cell stack to minimize stack waste heat and activating a cooling fluid heater to heat the cooling fluid. Once it is determined that the cooling fluid is not frozen or is flowing, then the method initiates a normal system start-up.

Abstract: A technique for reducing the amount of water that accumulates in an anode exhaust gas bleed line in a fuel cell system. The system includes a fuel cell stack, a cathode exhaust line and an anode exhaust line. The anode exhaust gas line is coupled to an anode bleed valve. An anode bleed line is coupled to the bleed valve and the cathode exhaust gas line so the hydrogen in the bled anode exhaust gas is diluted by the cathode exhaust gas. The anode bleed line is coupled to the cathode exhaust gas line so that a stand-off portion of the bleed line extends through a wall of the cathode exhaust gas line and into the cathode exhaust flow therein so as to prevent water and water vapor clinging to the inside surface of the cathode exhaust gas line from draining into the anode bleed line.

Abstract: A system and method for selectively determining whether a freeze purge should be performed at shut-down of a fuel cell stack. The method includes identifying that the vehicle has been keyed off and then determining whether a stack membrane humidification value is less than a predetermined humidification value that identifies the humidification of membranes in fuel cells in the fuel cell stack. If the stack membrane humidification value is not less than the predetermined humidification value, then the method determines if the ambient temperature is below a predetermined ambient temperature, and if so, performs the freeze purge. If the ambient temperature is not below the predetermined ambient temperature, then the method performs a short non-freeze purge of the flow channels in the fuel cell stack. The method determines a wake-up time for a controller for a next time to determine whether a freeze purge should be performed.

Abstract: A method for purging water from a fuel cell stack at fuel cell system shutdown. The method includes determining a stack water generation request to control the rate of drying of membranes in the stack and determining a cathode catalytic heating water generation request. A maximum charge a battery in the fuel cell system can accept is also determined. An ancillary power request for powering components of the fuel cell system during shutdown is determined. The method allocates how much of the water generation request will be fulfilled by operating the fuel cell stack to charge the battery and to provide the power needed for the ancillary power request, and how much of the water generation request will be fulfilled by cathode catalytic heating that produces water and heat in a cathode side of the fuel cell stack.

Abstract: A method for determining whether a fuel cell stack cooling fluid is flowing at cold fuel cell system start-up. The method monitors the temperature of the cooling fluid outside of the fuel cell stack, and determines whether the temperature of the cooling fluid is increasing properly as the temperature of the stack increases.

Abstract: A valve for a fuel cell system includes a valve housing having a valve seat formed therein. The valve seat includes an orifice formed therein to permit a fluid to flow through the valve housing. A movable member is disposed in the valve housing and is movable between an open position and a closed position. The movable member includes a first end having an elongate portion and a generally conical shaped base. At least a portion of the base is disposed in the orifice of the valve seat when the movable member is in the closed position to militate against a formation of ice across the orifice of the valve seat.

Abstract: A valve for a fuel cell system includes a main body having a passage through which a fluid is permitted to flow. A sliding member is disposed in the main body and configured to move between an open position and a closed position. The sliding member has an orifice formed therein. At least one biased plug is disposed within the main body adjacent the sliding member. The biased plug abuts an outer surface of the sliding member and permits fluid flow through the orifice of the sliding member when the sliding member is in the open position. The biased plug seals the orifice of the sliding member and militates against a formation of ice in the orifice when the sliding member is in the closed position.

Abstract: A method for performing a plausibility check of a fuel cell stack anode side pressure sensor to determine whether the pressure sensor is providing an accurate measurement. Prior to system start-up when a cathode side compressor is not providing cathode air to a fuel cell stack, and the cathode side of the stack is at ambient pressure, a pressure measurement from a differential pressure sensor between the anode side and the cathode side of the fuel cell stack is provided. The differential pressure sensor reading is added to a pressure measurement from an ambient pressure sensor, where the sum should be about the same as the pressure measurement from the anode side pressure sensor if the anode side pressure sensor is operating properly.

Abstract: A method for increasing the temperature of a cooling fluid used to control the temperature of a fuel cell stack at a system freeze start-up. The method includes determining that the cooling fluid is frozen or nearly frozen, and if so, deactivating excessive power draw on the fuel cell stack to minimize stack waste heat and activating a cooling fluid heater to heat the cooling fluid. Once it is determined that the cooling fluid is not frozen or is flowing, then the method initiates a normal system start-up.

Abstract: A method for shutting down a fuel cell system including operating a fuel cell stack. the method includes providing an increased cathode air flow so as to dry fuel cell membranes in the stack until a first desired level of high frequency resistance is achieved, rehydrating the cell membranes of the stack until a second desired level of high frequency resistance is achieved, and operating the stack with a decreased cathode input relative humidity until a third desired level of high frequency resistance is achieved.

Abstract: A method for determining whether a fuel cell stack cooling fluid is flowing at cold fuel cell system start-up. The method monitors the temperature of the cooling fluid outside of the fuel cell stack, and determines whether the temperature of the cooling fluid is increasing properly as the temperature of the stack increases.

Abstract: An internal coolant circulation system and method of homogenizing waste heat in a fuel cell stack using homogenous thermal coolant cycling is disclosed. The method includes operating a fuel cell stack, distributing a coolant through the fuel cell stack, terminating operation of the fuel cell stack, retaining the coolant in the fuel cell stack and circulating the coolant throughout the fuel cell stack.

Abstract: A purge valve for a split fuel cell stack design that prevents a direct flow path between the anode sides of the split stacks. The purge valve includes an inlet port that receives purge air from a compressor, a first outlet port in fluid communication with the anode side of one of the split stacks and a second outlet port in fluid communication with the anode side of the other split stack. A spring biased shaft maintains a diaphragm in a closed position to close off the flow channels between the inlet port and the first outlet port, the inlet port and the second outlet port and the first and second outlet ports during normal fuel cell operation. A hole is provided through the diaphragm to provide pressure equalization in the chamber.

Abstract: A method for performing a plausibility check of a fuel cell stack anode side pressure sensor to determine whether the pressure sensor is providing an accurate measurement. Prior to system start-up when a cathode side compressor is not providing cathode air to a fuel cell stack, and the cathode side of the stack is at ambient pressure, a pressure measurement from a differential pressure sensor between the anode side and the cathode side of the fuel cell stack is provided. The differential pressure sensor reading is added to a pressure measurement from an ambient pressure sensor, where the sum should be about the same as the pressure measurement from the anode side pressure sensor if the anode side pressure sensor is operating properly.