Abstract: A method for controlling cathode air flow at system start-up by controlling a stack by-pass valve. The method includes determining a concentration of hydrogen in a cathode side of the fuel cell system. The method also includes determining a volumetric flow rate through a cathode compressor, determining a volumetric flow rate through the stack cathode and determining a fraction of volumetric flow rate through the cathode to the total flow through the compressor. The method determines a modeled hydrogen outlet concentration from the fuel cell stack based on the volumetric flow rate through the compressor, the fraction of volumetric flow rate through the compressor to the total flow through the compressor and the concentration of hydrogen in the cathode. The method uses a desired fraction of volumetric flow rate through the cathode and the total flow through the compressor to determine the position of the by-pass valve.

Abstract: A method for reducing the probability of an air/hydrogen front in a fuel cell stack is disclosed that includes closing anode valves for an anode side of the fuel cell stack to permit a desired quantity of hydrogen to be left in the anode side upon shutdown and determining a schedule to inject hydrogen during the time the fuel cell stack is shutdown. The pressure on an anode input line is determined and a discrete amount of hydrogen is injected into the anode side of the stack according to the determined schedule by opening anode input line valves based on the determined pressure along the anode input line so as to inject the hydrogen into the anode side of the stack.

Abstract: A method for creating an oxygen depleted gas in a fuel cell system, including operating a fuel cell stack at a desired cathode stoichiometry at fuel cell system shutdown to displace a cathode exhaust gas with an oxygen depleted gas. The method further includes closing a cathode flow valve and turning off a compressor to stop the flow of cathode air.

Abstract: A fuel cell system including a fuel cell stack having a plurality of fuel cells is provided. An anode supply manifold and an anode exhaust manifold are in fluid communication with the anodes of the plurality of fuel cells. A first valve is in fluid communication with the anode supply manifold and a second valve is in fluid communication with the anode exhaust manifold. A pressure sensor is adapted to measure an anode pressure. In operation, the first valve and the second valve are controlled in response to the anode pressure, thereby militating against an undesired exhausting of an anode supply stream.

Abstract: A fuel cell system including a fuel cell stack having a plurality of fuel cells, the fuel cell stack including an anode supply manifold and an anode exhaust manifold, a first valve in fluid communication with at least one of the anode supply manifold and the anode exhaust manifold, wherein the first valve includes an inlet for receiving a fluid flow and an outlet for exhausting a fluid, a sensor for measuring at least a fluid pressure at the inlet and the outlet of the first valve, wherein the sensor generates a sensor signal representing the pressure measurement, and a processor for receiving the sensor signal, analyzing the sensor signal, and determining a composition of a fluid in the fuel cell system based upon the analysis of the sensor signal.

Abstract: A fuel cell system including a fuel cell stack having a plurality of fuel cells, each of the fuel cells including an electrolyte membrane disposed between an anode and a cathode, an anode supply manifold in fluid communication with the anodes of the fuel cells, the anode supply manifold providing fluid communication between a source of hydrogen and the anodes, an anode exhaust manifold in fluid communication with the anodes of the fuel cells, and a fan in fluid communication with the anodes of the fuel cells, wherein the fan controls a flow of fluid through the anodes of the fuel cells after the fuel cell system is shutdown.

Abstract: A membrane humidifier for a fuel cell system is disclosed wherein the membrane humidifier includes a plurality of membrane layers, a first pair of spaced apart sealing bars disposed between a first membrane layer and a second membrane layer adjacent to perimeter edges thereof to form a first flow channel, a second pair of spaced apart sealing bars disposed between the second membrane layer and a third membrane layer adjacent to perimeter edges thereof to form a second flow channel, and a plurality of supports, wherein a first support is disposed adjacent the second planar layer and extending between the second pair of spaced apart sealing bars, and a second support is disposed adjacent the third planar layer and extending between the second pair of spaced apart sealing bars.

Abstract: Processes to shut down a fuel cell system are described. In one implementation (400), fuel (H2) and oxidizer (air) flow is halted and the system's anode region (305) is sealed. A load (215) is then engaged across the system's fuel cell stack (205) so as to deplete much of the fuel in the stack's sealed anode region (305). The stack (205) is monitored to determine when the load should be disengaged. (215). Once the load is disengaged, fluid communication between the system's anode and cathode regions is established. The vacuum created in the anode region (305) as a consequence of consuming H2 therein, pulls nitrogen enriched gas from the cathode region (310) into the anode region (305). When substantially all of the H2 has been depleted from the anode region (305), no pressure difference exists between the anode and cathode regions and fluid communication between the two is severed.

Abstract: Processes to shut down a fuel cell system are described. In one implementation (300), a load (215) is cyclically engaged and disengaged across a fuel cell stack (205) so as to deplete the fuel available to the system's fuel cells (205). Voltage and/or current thresholds may be used to determine when to engage and disengage the load (215) and when to terminate the shutdown operation. In another implementation (500), a variable load (405) is engaged and adjusted so as to deplete the fuel available to the system's fuel cells (205). As before, voltage and/or current thresholds may be used to determine when to adjust the load (405) and when to terminate the shutdown process. In still another implementation, a load (215 or 405) may be periodically engaged and disengaged during some portion of the shutdown process and engaged but adjusted during other portions of the shutdown process.

Abstract: A method for filling a fuel cell anode supply manifold with hydrogen prior to a start-up operation to facilitate a substantially even hydrogen distribution across the fuel cell is disclosed. The anode supply manifold is in fluid communication with a source of hydrogen. A first valve in fluid communication with the anode supply manifold and a second valve in fluid communication with an anode exhaust manifold are initially in a closed position while hydrogen is supplied to the anode inlet conduit to pressurize the fuel cell stack. The first valve is then opened to purge at least a portion of a fluid from the anode supply manifold to facilitate a filling of the manifold with hydrogen.

Abstract: A fuel cell system that enables an assisted anode purge upon start-up is provided. The fuel cell system includes a fuel cell stack having a plurality of fuel cells with anodes and cathodes. The fuel cell stack has an anode supply manifold and an anode exhaust manifold in fluid communication with the anodes. The fuel cell system further includes a suction device in fluid communication with at least one of the anode supply manifold and the anode exhaust manifold. The suction device adapted to selectively draw a partial vacuum on the fuel cell stack during a start-up of the fuel cell system. Methods for starting the fuel cell system are also provided.

Abstract: The present invention includes an integrated fuel processor subsystem incorporating a thermal combustor, a catalytic combustor, a quasi-autothermal reactor (QATR) and a air-fuel-steam (AFS) mixer to provide a range of operating modes exhibiting performance between that of a pure steam reformer and a pure autothermal reformer to increase the flexibility of the fuel processor to handle transient system demands such as cold starts, suppress emissions and carbon formation and improve efficiency.

Abstract: A fuel cell system including a fuel cell stack having a plurality of fuel cells is provided. An anode supply manifold and an anode exhaust manifold are in fluid communication with the anodes of the plurality of fuel cells. A first valve is in fluid communication with the anode supply manifold and a second valve is in fluid communication with the anode exhaust manifold. A pressure sensor is adapted to measure an anode pressure. In operation, the first valve and the second valve are controlled in response to the anode pressure, thereby militating against an undesired exhausting of an anode supply stream.

Abstract: An autothermal reformer according to the principles of the present invention comprises a first stage that selectively receives a fuel flow, a first oxidant flow, and a steam flow. The first stage has a first portion of a catalyst bed. The fluids within the first stage are routed through the first portion of the catalyst bed and react. There is a second stage downstream from and communicating with the first stage. The second stage receives the fluids from the first stage and also selectively receives a second oxidant flow. The second oxidant flow and the fluids received from the first stage flow through a second portion of a catalyst bed and further react.

Abstract: The present invention relates to controlled staged rich combustion throughout a fuel processing system in order to improve start up performance. Multiple stages of air injection are used to burn rich combustion products within each component to provide direct heating thereof. During the start up cycle, the fluid temperature entering each reactor is increased and each component is heated to its operating temperature in parallel. The controlled staged rich combustion eliminates the load imposed upon a combustor within the system during the start up cycle. Thus, each of the components within the fuel processing system may be optimized for an operational mode rather than a start up mode.

Abstract: Various devices and methods for achieving electrochemical energy conversion are presented. In accordance with one embodiment, an energy conversion cell is configured to enable the first and second reactant supplies to communicate selectively with first and second catalytic electrodes of the cell. The selective communication of the first and second reactant supplies with the first and second catalytic electrodes may be attributable to alteration of the reactant supply flow paths or to movement of the first and second catalytic electrodes.

Abstract: Various devices and methods for achieving electrochemical energy conversion are presented. In accordance with one embodiment, an energy conversion cell is configured to enable the first and second reactant supplies to communicate selectively with first and second catalytic electrodes of the cell. The selective communication of the first and second reactant supplies with the first and second catalytic electrodes may be attributable to alteration of the reactant supply flow paths or to movement of the first and second catalytic electrodes.

Abstract: A method is provided to inject liquid water into the normal stream of fuel, superheated air and superheated steam entering a primary reactor of a fuel processor. The injection location is in the steam supply line where superheated steam vaporizes a majority of the liquid water, preferably prior to injection into the primary reactor. Steam supplied by a vaporizer may temporarily lag desired steam production due to system up-power transients or startup conditions, coupled with vaporizer thermal lag time. Injection of liquid water overcomes this temporary deficit of steam. Additional air is also supplied as needed to improve reactance for a given steam volume/temperature. Injection rate or volume of the liquid water and air may also be based on one or more measured variables of the primary reactor.

Abstract: A method is provided to inject liquid water into the normal stream of fuel, superheated air and superheated steam entering a primary reactor of a fuel processor. The injection location is in the steam supply line where superheated steam vaporizes a majority of the liquid water, preferably prior to injection into the primary reactor. Steam supplied by a vaporizer may temporarily lag desired steam production due to system up-power transients or startup conditions, coupled with vaporizer thermal lag time. Injection of liquid water overcomes this temporary deficit of steam. Additional air is also supplied as needed to improve reactance for a given steam volume/temperature. Injection rate or volume of the liquid water and air may also be based on one or more measured variables of the primary reactor.

Abstract: An autothermal reformer according to the principles of the present invention comprises a first stage that selectively receives a fuel flow, a first oxidant flow, and a steam flow. The first stage has a first portion of a catalyst bed. The fluids within the first stage are routed through the first portion of the catalyst bed and react. There is a second stage downstream from and communicating with the first stage. The second stage receives the fluids from the first stage and also selectively receives a second oxidant flow. The second oxidant flow and the fluids received from the first stage flow through a second portion of a catalyst bed and further react.