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.

Abstract: A system for bleeding the anode side of first and second split fuel cell stacks in a fuel cell system that employs anode flow-shifting, where each split stack includes a bleed valve. The system determines that one or both of the bleed valves is stuck in an open position if there is flow through an orifice and a bleed has not been commanded. A shut-off valve is then used to provide the bleed if the cathode exhaust gas is able to dilute the hydrogen in the bled anode exhaust gas. An outlet valve between the first and second split stacks is used to bleed the anode exhaust gas if the cathode exhaust gas is not significant enough to dilute the hydrogen in the anode exhaust gas. If the first or second bleed valve is stuck in the closed position, then the outlet valve is used to provide the bleed.

Abstract: An improved air foil bearing assembly is disclosed. The air foil bearing assembly includes a bearing housing having an axially extending bore therein and a shaft arranged within the bore for relative coaxial rotation with respect to the bearing housing. The shaft cooperates with the bearing housing to define an annular gap therebetween. A foil assembly is disposed in the annular gap, including at least one foil having at least one laterally extending tab. The tab is adapted to be received in and extend axially from the annular gap and is further adapted to be bent into frictional contact with an outer surface of the bearing housing to militate against axial movement of the foil.

Abstract: A system and method for quickly heating a fuel cell stack at fuel cell system start-up. The fuel cell system includes a three-way valve positioned in the anode exhaust that selectively directs the anode exhaust gases to the cathode input of the fuel cell stack so that hydrogen in the anode exhaust gas can be used to heat the fuel cell stack. During normal operation when the fuel cell stack is at the desired temperature, the three-way valve in the anode exhaust can be used to bleed nitrogen to the cathode exhaust.

Abstract: An improved air foil bearing assembly is disclosed. The air foil bearing assembly includes a bearing housing having an axially extending bore therein and a shaft arranged within the bore for relative coaxial rotation with respect to the bearing housing. The shaft cooperates with the bearing housing to define an annular gap therebetween. A foil assembly is disposed in the annular gap, including at least one foil having at least one laterally extending tab. The tab is adapted to be received in and extend axially from the annular gap and is further adapted to be bent into frictional contact with an outer surface of the bearing housing to militate against axial movement of the foil.

Abstract: A method for triggering an anode bleed from split fuel cell stacks in a fuel cell system that employs anode flow-shifting. The method requests the bleed if any one of three different conditions are met. Those conditions include that the concentration of nitrogen in the anode side of the split stacks is above a predetermined percentage, the voltage spread between the maximum cell voltage and the minimum cell voltage of two fuel cells in the split stacks is greater than a predetermined spread voltage and the absolute value of the difference between the overall voltage of the two split stacks is greater than a predetermined voltage. The concentration of nitrogen in the anode can be determined in any suitable manner, such as by a nitrogen cross-over model or a sensor.

Abstract: An improved air foil bearing assembly is disclosed. The air foil bearing assembly includes a bearing housing having an axially extending bore therein and a shaft arranged within the bore for relative coaxial rotation with respect to the bearing housing. The shaft cooperates with the bearing housing to define an annular gap therebetween. A foil assembly is disposed in the annular gap, including at least one foil having at least one laterally extending tab. The tab is adapted to be received in and extend axially from the annular gap and is further adapted to be bent into frictional contact with an outer surface of the bearing housing to militate against axial movement of the foil.

Abstract: A fuel cell system is provided having a fuel cell stack including a plurality of fuel cells. The fuel cell system includes an anode supply manifold in fluid communication with the plurality of fuel cells, the anode supply manifold adapted to deliver a anode supply stream to the plurality of fuel cells; an anode exhaust manifold in fluid communication with the anodes of the plurality of fuel cells, the anode exhaust manifold adapted to receive an anode exhaust stream from the plurality of fuel cells; a first valve in fluid communication with the anode supply manifold; and a second valve in fluid communication with the anode exhaust manifold. A method of starting the fuel cell system is also provided. The fuel cell system and method militates against a non-uniform distribution of the anode supply stream to the anodes of the plurality of fuel cells.

Abstract: A fuel cell system that controls an anode exhaust gas bleed during power up-transients. The fuel cell system includes a by-pass valve that allows compressor air to by-pass the fuel cell stack and be directly emitted into the cathode exhaust gas stream. The system detects a power up-transient by monitoring the rate of closing of the by-pass valve and the rate of change of an increase in the compressor airflow set-point. If these parameters pass a certain threshold, then the system determines that a power up-transient is occurring, and prevents an anode exhaust gas bleed for a predetermined period of time. If cathode pulsing is occurring where power up-transients come one after another, then the system will continuously reset the time period for preventing the anode exhaust gas bleed until a second time limit is reached, where the bleed is then forced.

Abstract: A parallel dual stack fuel cell system having anode recirculation includes a first fuel cell stack and a second fuel cell stack. Each of the first and second fuel cell stacks includes a gas outlet line connected to an anode outlet unit. The anode outlet unit functions to release wet H2/N2 gaseous mixture from the system. A second water separator is provided between the anode outlet unit and gas inlet lines to the first and second fuel cell stacks to increase removal of water droplets prior to a recirculation pump.

Abstract: A valve mechanism is disclosed, the valve mechanism including a rotor and stator adapted for selectively providing a flow of hydrogen to and selectively bleeding the hydrogen from a plurality fuel cell stacks.

Abstract: A system and method for quickly heating a fuel cell stack at fuel cell system start-up. The fuel cell system includes a three-way valve positioned in the anode exhaust that selectively directs the anode exhaust gases to the cathode input of the fuel cell stack so that hydrogen in the anode exhaust gas can be used to heat the fuel cell stack. During normal operation when the fuel cell stack is at the desired temperature, the three-way valve in the anode exhaust can be used to bleed nitrogen to the cathode exhaust.

Abstract: A system for bleeding the anode side of first and second split fuel cell stacks in a fuel cell system that employs anode flow-shifting, where each split stack includes a bleed valve. The system determines that one or both of the bleed valves is stuck in an open position if there is flow through an orifice and a bleed has not been commanded. A shut-off valve is then used to provide the bleed if the cathode exhaust gas is able to dilute the hydrogen in the bled anode exhaust gas. An outlet valve between the first and second split stacks is used to bleed the anode exhaust gas if the cathode exhaust gas is not significant enough to dilute the hydrogen in the anode exhaust gas. If the first or second bleed valve is stuck in the closed position, then the outlet valve is used to provide the bleed.

Abstract: A system for providing fuel recirculation in a fuel cell is disclosed, wherein the system uses a cathode exhaust flow to energize a fuel recirculation pump that facilitates the fuel recirculation from an anode exhaust passage to an anode supply passage.

Abstract: A method for triggering an anode bleed from split fuel cell stacks in a fuel cell system that employs anode flow-shifting. The method requests the bleed if any one of three different conditions are met. Those conditions include that the concentration of nitrogen in the anode side of the split stacks is above a predetermined percentage, the voltage spread between the maximum cell voltage and the minimum cell voltage of two fuel cells in the split stacks is greater than a predetermined spread voltage and the absolute value of the difference between the overall voltage of the two split stacks is greater than a predetermined voltage. The concentration of nitrogen in the anode can be determined in any suitable manner, such as by a nitrogen cross-over model or a sensor.

Abstract: A fuel cell system is provided having a fuel cell stack including a plurality of fuel cells. The fuel cell system includes an anode supply manifold in fluid communication with the plurality of fuel cells, the anode supply manifold adapted to deliver a anode supply stream to the plurality of fuel cells; an anode exhaust manifold in fluid communication with the anodes of the plurality of fuel cells, the anode exhaust manifold adapted to receive an anode exhaust stream from the plurality of fuel cells; a first valve in fluid communication with the anode supply manifold; and a second valve in fluid communication with the anode exhaust manifold. A method of starting the fuel cell system is also provided. The fuel cell system and method militates against a non-uniform distribution of the anode supply stream to the anodes of the plurality of 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.

Abstract: A fuel cell system that controls an anode exhaust gas bleed during power up-transients. The fuel cell system includes a by-pass valve that allows compressor air to by-pass the fuel cell stack and be directly emitted into the cathode exhaust gas stream. The system detects a power up-transient by monitoring the rate of closing of the by-pass valve and the rate of change of an increase in the compressor airflow set-point. If these parameters pass a certain threshold, then the system determines that a power up-transient is occurring, and prevents an anode exhaust gas bleed for a predetermined period of time. If cathode pulsing is occurring where power up-transients come one after another, then the system will continuously reset the time period for preventing the anode exhaust gas bleed until a second time limit is reached, where the bleed is then forced.

Abstract: A valve mechanism is disclosed, the valve mechanism including a rotor and stator adapted for selectively providing a flow of hydrogen to and selectively bleeding the hydrogen from a plurality fuel cell stacks.

Abstract: A parallel dual stack fuel cell system having anode recirculation includes a first fuel cell stack and a second fuel cell stack. Each of the first and second fuel cell stacks includes a gas outlet line connected to an anode outlet unit. The anode outlet unit functions to release wet H2/N2 gaseous mixture from the system. A second water separator is provided between the anode outlet unit and gas inlet lines to the first and second fuel cell stacks to increase removal of water droplets prior to a recirculation pump.