Abstract: A fuel cell system for generating a hydrogen test pulse includes a fuel cell stack having an anode inlet in fluid communication with a hydrogen source via a fuel spending line, a cathode inlet in fluid communication with an oxidant source, and an anode outlet and a cathode outlet in fluid communication with an exhaust line. An electric pressure regulator is in fluid communication with the fuel spending line. An overpressure valve is in fluid communication with an overpressure line, which is in fluid communication with the fuel spending line between the electric pressure regulator and the fuel cell stack. A hydrogen sensor is in communication with the exhaust line, and is configured to measure the hydrogen test pulse.

Abstract: A thermal sub-system for a fuel cell system that employs an algorithm using feed-forward control. The algorithm calculates a Reynolds number based on the velocity of the cooling fluid, a diameter of a coolant loop pipe and a kinematic viscosity (temperature) of a cooling fluid. The algorithm also uses a pressure loss number based on the Reynolds number and a position of a by-pass valve. The algorithm also defines a pressure loss value based on the pressure loss number, the density of the cooling fluid and the velocity of the cooling fluid. The algorithm then calculates a delivery head value based on the pressure loss value, the fluid density and a gravitational acceleration. The algorithm then uses the delivery head value and a predetermined set-point value of the volume flow to determine a desired pump speed based on the current operating parameters of the system.

Abstract: A method and system for controlling a pressure regulator in a gas storage system using a pressure switch as a pressure measurement device. A controller uses supply pressure data and gas flow demand data to compute a feed-forward control term, and uses data from a pressure sensor downstream of the pressure regulator to compute a feedback control term. During normal operation, with pressure downstream of the regulator oscillating about a set point pressure, on-time and off-time periods of a pressure switch are monitored, and an adaptive control term is computed which balances on-time and off-time. If the pressure sensor fails, excessive switch on-time or off-time will be detected; in response to this, the feedback control term is disregarded, and an adaptive control term is computed which aims to restore balanced on-time and off-time of the switch, thus indicating that the actual pressure is oscillating about the set point.

Abstract: A fuel cell system for generating a hydrogen test pulse includes a fuel cell stack having an anode inlet in fluid communication with a hydrogen source via a fuel spending line, a cathode inlet in fluid communication with an oxidant source, and an anode outlet and a cathode outlet in fluid communication with an exhaust line. An electric pressure regulator is in fluid communication with the fuel spending line. An overpressure valve is in fluid communication with an overpressure line, which is in fluid communication with the fuel spending line between the electric pressure regulator and the fuel cell stack. A hydrogen sensor is in communication with the exhaust line, and is configured to measure the hydrogen test pulse.

Abstract: A method and system for controlling a pressure regulator in a gas storage system using a pressure switch as a pressure measurement device. A controller uses supply pressure data and gas flow demand data to compute a feed-forward control term, and uses data from a pressure sensor downstream of the pressure regulator to compute a feedback control term. During normal operation, with pressure downstream of the regulator oscillating about a set point pressure, on-time and off-time periods of a pressure switch are monitored, and an adaptive control term is computed which balances on-time and off-time. If the pressure sensor fails, excessive switch on-time or off-time will be detected; in response to this, the feedback control term is disregarded, and an adaptive control term is computed which aims to restore balanced on-time and off-time of the switch, thus indicating that the actual pressure is oscillating about the set point.

Abstract: A fuel cell system that includes a first fuel cell stack and a second fuel cell stack in a divided stack design. A first water vapor transfer unit is used to humidify the cathode inlet to the first divided stack and a second water vapor transfer unit is used to humidify the cathode inlet air to the second divided stack. The cathode exhaust gas from the divided stacks is used to provide the humidification for the water vapor transfer units. In order to provide relative humidity balancing between the first and second divided stacks, the cathode inlet air flowing through one of the WVT units is sent to one of the divided stacks that receives the cathode exhaust gas from the other divided stack and vice versa.

Abstract: A system and method for drying a fuel cell stack after stack shutdown. In one embodiment, a cooling fluid is pumped through the fuel cell stack after the system is shutdown to use the heat still available in the cooling fluid immediately after shutdown to provide thermal equilibrium in the stack. In another embodiment, the heated cooling fluid still available immediately after system shutdown is sent through a cathode input gas heat exchanger so that drying air from the system compressor is heated by the cooling fluid before it enters the stack. In another embodiment, a separate heat exchanger is provided that receives the drying gas prior to it being sent into the fuel cell stack.

Abstract: A diagnostic method of detecting component failures in a fuel cell anode subsystem involves estimating fuel flow through injectors and comparing the estimated flow with a model based upon the system parameters. An observer based model is used to determine a residual value, the difference between the hydrogen input and the hydrogen consumed, and the residual is compared with a threshold range. In alternative embodiments, the stack current and the state of the valves are used to calculate the required hydrogen flow through the injectors and the duty cycle of an injector is compared to a tolerance range.

Abstract: A thermal sub-system for a fuel cell system that calculates a desired volume flow or mass flow of a cooling fluid pumped through a fuel cell stack solely on thermal stack power loss and cooling fluid temperature. An algorithm calculates a power loss of the stack and then calculates the temperature of the stack based on the power loss and dissipated heat power from the stack. The algorithm uses the temperature of the stack and the temperature of the cooling fluid out of the stack to determine the dissipated heat power. The algorithm then uses the temperature of the stack, the temperature of the cooling fluid into the stack and the temperature of the cooling fluid out of the stack to determine the flow.

Abstract: A thermal sub-system for a fuel cell system that uses pump characteristics to determine a required cooling fluid volume flow. An algorithm controls the speed of the pump to provide the desired volume flow of the cooling fluid for the system parameters. The algorithm determines a motor efficiency value based on a pump input power value and a pump speed value. The algorithm then determines a coefficient of power value based on the motor efficiency value, the pump input power value and the pump speed value. The algorithm then uses a look-up table to convert the coefficient of power value to a coefficient of flow value. The algorithm then calculates the volume flow based on the coefficient of flow value and the pump speed value.

Abstract: A thermal sub-system for a fuel cell system that employs an algorithm using feed-forward control. The algorithm calculates a Reynolds number based on the velocity of the cooling fluid, a diameter of a coolant loop pipe and a kinematic viscosity (temperature) of a cooling fluid. The algorithm also uses a pressure loss number based on the Reynolds number and a position of a by-pass valve. The algorithm also defines a pressure loss value based on the pressure loss number, the density of the cooling fluid and the velocity of the cooling fluid. The algorithm then calculates a delivery head value based on the pressure loss value, the fluid density and a gravitational acceleration. The algorithm then uses the delivery head value and a predetermined set-point value of the volume flow to determine a desired pump speed based on the current operating parameters of the system.

Abstract: A system and method for drying a fuel cell stack after stack shutdown. In one embodiment, a cooling fluid is pumped through the fuel cell stack after the system is shutdown to use the heat still available in the cooling fluid immediately after shutdown to provide thermal equilibrium in the stack. In another embodiment, the heated cooling fluid still available immediately after system shutdown is sent through a cathode input gas heat exchanger so that drying air from the system compressor is heated by the cooling fluid before it enters the stack. In another embodiment, a separate heat exchanger is provided that receives the drying gas prior to it being sent into the fuel cell stack.