Abstract: An apparatus for recirculating a reactant fluid stream of a fuel cell system, and electric power generation systems comprising the apparatus, are disclosed. The apparatus comprises (1) a common suction chamber fluidly connected to a suction inlet configured to receive a recirculated flow from the exhaust stream of the fuel cell stack, (2) a low-flow nozzle positioned in the common suction chamber and fluidly connected to a low-flow motive inlet configured to receive a first motive flow from a reactant source of the fuel cell stack, (3) a low-flow diffuser fluidly connected to a discharge outlet configured to provide the inlet stream to the fuel cell stack, (4) a high-flow nozzle positioned in the common suction chamber and fluidly connected to a high-flow motive inlet configured to receive the first motive flow from the reactant source, and (5) a high-flow diffuser fluidly connected to the discharge outlet.

Abstract: Methods and apparatus for fuel release mitigation including enclosing a fuel cell stack (12) within an enclosure (20), supplying oxidant to the enclosure, circulating the oxidant within the enclosure to mix with any fuel present in the enclosure, withdrawing circulated oxidant from the enclosure; and supplying at least a portion of the circulated oxidant withdrawn from the enclosure to the stack as the cathode inlet stream.

Abstract: A fuel cell system and associated method allows for continuous operation of the fuel cell system with fuel recirculation, without the necessity for periodic purging. A portion of the anode exhaust is not recirculated but is continuously bled from the anode exhaust line. Preferably, less than 5% by volume of the anode exhaust is allowed to bleed continuously from the anode exhaust. The bleed line may be connected to a catalytic reactor which combusts the unused fuel. The cathode exhaust may be used as the oxidant for the catalytic reactor. The flow of exhaust to the catalytic reactor may be controlled to ensure that the concentration of hydrogen in the catalytic reactor is no higher than 50% of the lower limit of inflammability for hydrogen.

Abstract: An electric power generation system has a multiple jet ejector assembly for recirculating an exhaust stream. The system includes a fuel cell stack having a reactant stream inlet, a reactant stream outlet and at least one fuel cell. A pressurized reactant supply provides a reactant to the multiple jet ejector assembly. The multiple jet ejector assembly includes two motive flow inlets, one suction inlet, fluidly connected to the reactant stream outlet to receive a recirculated flow from the fuel cell stack, and one discharge outlet, fluidly connected to the reactant stream inlet to provide an inlet stream to the fuel cell stack. A pressure regulator is interposed between the pressurized reactant supply and the two motive flow inlets of the multiple jet ejector assembly. A first solenoid valve is interposed between the first motive flow inlet and the regulator. A second solenoid valve is interposed between the second motive flow inlet and the regulator.

Abstract: A fuel cell system comprises a reservoir for cryogenic media and a fuel cell unit containing at least one fuel cell connected to receive fuel from the reservoir. At least a first heat exchanger is provided within a cooling circuit for the fuel cell unit, whereby heat from the first heat exchanger (3) is used, at least indirectly, to provide fuel from the reservoir. A heating circuit for the reservoir, designed to heat and/or vaporize the cryogenic medium via the first heat exchanger, is connected directly to the cooling circuit for the fuel cell unit.

Abstract: A method and apparatus for humidifying a gas flow includes means for atomizing a liquid into a gas feed line and means for heating the liquid. The atomizing means is provided in a spray chamber, with a heat-exchanger region for at least partially evaporating the liquid being arranged adjacent to the spray chamber. The heat-exchanger region has a multiplicity of flow passages for gas flows which are to be humidified, which flow passages are at least partially delimited by heat-exchanger surfaces for condensing and evaporating the liquid.

Abstract: A fuel cell system and associated method allows for continuous operation of the fuel cell system with fuel recirculation, without the necessity for periodic purging. A portion of the anode exhaust is not recirculated but is continuously bled from the anode exhaust line. Preferably, less than 5% by volume of the anode exhaust is allowed to bleed continuously from the anode exhaust. The bleed line may be connected to a catalytic reactor which combusts the unused fuel. The cathode exhaust may be used as the oxidant for the catalytic reactor. The flow of exhaust to the catalytic reactor may be controlled to ensure that the concentration of hydrogen in the catalytic reactor is no higher than 50% of the lower limit of inflammability for hydrogen.

Abstract: A fuel cell system comprises a reservoir for cryogenic media and a fuel cell unit containing at least one fuel cell connected to receive fuel from the reservoir. At least a first heat exchanger is provided within a cooling circuit for the fuel cell unit, whereby heat from the first heat exchanger (3) is used, at least indirectly, to provide fuel from the reservoir. A heating circuit for the reservoir, designed to heat and/or vaporize the cryogenic medium via the first heat exchanger, is connected directly to the cooling circuit for the fuel cell unit.

Abstract: A method and apparatus for humidifying a gas flow includes means for atomizing a liquid into a gas feed line and means for heating the liquid. The atomizing means is provided in a spray chamber, with a heat-exchanger region for at least partially evaporating the liquid being arranged adjacent to the spray chamber. The heat-exchanger region has a multiplicity of flow passages for gas flows which are to be humidified, which flow passages are at least partially delimited by heat-exchanger surfaces for condensing and evaporating the liquid.

Abstract: A valve with a Laval nozzle, a valve needle movable axially in the Laval nozzle, and an inlet chamber which receives the valve needle foot, in which chamber a radially extended inlet opening terminates. The inlet chamber is separated axially from the inlet plane of the Laval nozzle by a flow channel located therebetween. The inlet chamber is delimited by the valve needle on one side and by one of the valve needle housing sections surrounding the valve needle on the other side. This valve can be used in particular as a metering valve for metering a process gas for a reaction process in a motor vehicle operated by a fuel cell.

Abstract: An apparatus and method for starting a vehicle which is driven by an electric drive unit supplied with electrical energy from a fuel cell. A compressor is arranged in the feed line of the fuel cell for the oxidant mass flow and is driven by an electric motor supplied with voltage from the fuel cell itself. For the purpose of starting the fuel cell, a starter motor is provided for driving the compressor which is fed from a 12 V starter battery. In addition, a safety interrogation is initiated before starting the vehicle. The fuel cell is not run up to a prescribed no-load power with the aid of the starter motor until successful termination of the safety interrogation. The drive unit is then released after this no-load power has been reached.

Abstract: A method and a system meters a supply of methanol and/or water out of a storage reservoir to a fuel-cell system by way of a conveying conduit with a metering valve. A constant mass flow is conveyed out of the storage reservoir into the conveying conduit via a conveying pump. The differential pressure between the conveying conduit and fuel-cell system is set at a predetermined value via a differential-pressure controller which is arranged in a return conduit provided between the conveying conduit and storage reservoir. The methanol and/or water supplied can be set, for example, by varying the opening and closing times of a solenoid valve. A second metering stage can be provided in the return conduit downstream of the first metering stage. When two separate metering systems are used, a common pump motor can be employed.

Abstract: A process and an apparatus control output of an air-breathing fuel cell system which consists of an air supply line, a fuel cell, an air exhaust line, and a separate gas supply system for hydrogen gas. To control the fuel cell output, an adjustable rotary speed compressor is located in the air supply line and a variable absorption capacity expander is located in the air exhaust line. The compressor, the expander, and an additional electric motor are positioned on a common shaft. The expander converts the pressure energy contained in the exhaust air into mechanical energy and delivers that energy via the common shaft to the compressor. The air volume flow is controlled by the compressor rotary speed and adjusted to a preset value. A preset working pressure is established in the fuel cell system by adjusting the absorption capacity of the expander.

Abstract: A method and an apparatus are provided for controlling the power of an electric drive unit in a vehicle. The drive unit is supplied with electrical energy by a fuel cell in the vehicle. On the basis of a power request which is determined from the accelerator pedal position, the air flow rate required to provide the set power from the fuel cell is calculated and set by controlling rotational speed of a compressor arranged in the air intake line to the fuel cell. To prevent the fuel cell from producing more electrical power than the drive unit can absorb, the drive unit acts limits the power request by emitting appropriate error messages. The set value for the power is fed to the drive unit and can be corrected such that the drive unit never demands more power than the amount of power instantaneously produced by the fuel cell to prevent fuel cell collapse.

Abstract: A process and an apparatus control output of an air-breathing fuel cell system which consists of an air supply line, a fuel cell, an air exhaust line, and a separate gas supply system for hydrogen gas. To control the fuel cell output, an adjustable rotary speed compressor is located in the air supply line and a variable absorption capacity expander is located in the air exhaust line. The compressor, the expander, and an additional electric motor are positioned on a common shaft. The expander converts the pressure energy contained in the exhaust air into mechanical energy and delivers that energy via the common shaft to the compressor. The air volume flow is controlled by the compressor rotary speed and adjusted to a preset value. A preset working pressure is established in the fuel cell system by adjusting the absorption capacity of the expander.

Abstract: A process and an apparatus humidify process gas for operating fuel cell systems. To ensure high efficiency, the process gas must be introduced at a predetermined temperature and humidity. A metered quantity of fine water droplets is injected into the gas supply line, by way of which the process air is humidified. If the fuel cell is operated under pressure, the process air generally has to be cooled after it has been compressed. The process air is automatically cooled as a result of a partial evaporation of the water droplets while the residual quantity of water in the form of droplets is introduced into the fuel cell.