摘要:
A method for reconditioning a fuel cell stack. The method includes periodically increasing the relative humidity level of the cathode input airflow to the stack to saturate the cell membrane electrode assemblies to be greater than the relative humidity levels during normal stack operating conditions. The method also includes providing hydrogen to the anode side of the fuel cell stack at system shut down while the membrane electrode assemblies are saturated without stack loads being applied so that the hydrogen crosses the cell membranes to the cathode side and reacts with oxygen to reduce stack contaminants.
摘要:
A system and method for providing a fuel cell stack purge to remove excess water during system shut-down. A compressor is operated at a shut-down speed to force water out of the cathode flow channels and draw water through the membrane from the anode flow channels so that a desired amount of water is removed from the fuel cell stack without over drying the membrane. The cathode shut-down purge flow can be introduced in the forward or reverse direction. Further, the flow of hydrogen fuel can be directed so that it flows through the anode flow channels in an opposite direction to push water out of an anode outlet manifold into the anode flow channels so that it will also be drawn through the membrane by the cathode airflow. Finally, a brief rehydration step is added after the shut-down purge to achieve the desired water content in the cells.
摘要:
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.
摘要:
A system and method for reducing the frequency of stack stand-by mode events, if necessary, as a fuel cell stack ages and experiences lower performance. The method determines an irreversible voltage loss of the fuel cell stack at predetermined time intervals and determines a stack voltage degradation variable based on the irreversible voltage loss. The method also determines if the stack voltage degradation variable indicates that the fuel cell stack will not meet predetermined stack end-of-life voltage requirements and calculates a maximum allowed voltage degradation rate of the fuel cell stack. The method calculates a maximum number of stand-by mode events per unit time that can be allowed to prevent the stack from exceeding the maximum allowed degradation rate and controls the number of stand-by mode events based on the calculated maximum number of stand-by mode events.
摘要:
A method for improving fuel cell system reliability in the event of end cell heater failure in a fuel cell stack. The method includes detecting that an end cell heater has failed. If an end cell heater failure is detected, then the method performs one or more of setting a cooling fluid pump to a predetermined speed that drives a cooling fluid through cooling fluid flow channels in the fuel cell stack, limiting the output power of the fuel cell stack or the net power of the fuel cell system, limiting the maximum temperature of the cooling fluid flowing out of the stack, turning off stack anti-flooding algorithms that may be used to remove water from reactant gas flow channels in the stack, and turning off cathode stoichiometry adjustments for relative humidity control in response to water accumulating in cathode flow channels in the fuel cell stack.
摘要:
A method for providing calibration and synchronization pulses in a pulse width modulation (PWM) signal including cell voltage measurement pulses, where the calibration pulses are four calibration pulses having a pattern of a narrow width high voltage pulse followed by a wide width low voltage pulse followed by a narrow width high voltage pulse followed by a wide width low voltage pulse that has a very low probability of occurring in a practical fuel cell system. The method modulates a combined sequence of the voltage measurement signals and the calibration pulses using an inverted saw tooth wave to provide the PWM signal, where a width of the pulses representing the voltage signals are proportional to a width of the pulses representing the calibration pulses.
摘要:
A system and method for reducing the frequency of stack stand-by mode events, if necessary, as a fuel cell stack ages and experiences lower performance. The method determines an irreversible voltage loss of the fuel cell stack at predetermined time intervals and determines a stack voltage degradation variable based on the irreversible voltage loss. The method also determines if the stack voltage degradation variable indicates that the fuel cell stack will not meet predetermined stack end-of-life voltage requirements and calculates a maximum allowed voltage degradation rate of the fuel cell stack. The method calculates a maximum number of stand-by mode events per unit time that can be allowed to prevent the stack from exceeding the maximum allowed degradation rate and controls the number of stand-by mode events based on the calculated maximum number of stand-by mode events.
摘要:
A system and method for increasing the temperature of a fuel cell stack quickly, especially at cold stack start-up. The method includes determining whether the fuel cell stack is below a first predetermined temperature threshold, and, if so, starting a cooling fluid flow through the stack and engaging a shorting circuit across the stack to short circuit the stack and cause the stack to operate inefficiently. The method then determines a desired heating rate of the fuel cell stack and calculates a cathode airflow to the fuel cell stack based on the desired heating rate. The method reduces the flow of cathode air to the stack if a minimum cell voltage is below a predetermined minimum cell voltage threshold and disengages the shorting circuit and applies vehicle loads to the stack when the stack temperature reaches a predetermined second temperature threshold.
摘要:
A method for reconditioning a fuel cell stack. The method includes periodically increasing the relative humidity level of the cathode input airflow to the stack to saturate the cell membrane electrode assemblies to be greater than the relative humidity levels during normal stack operating conditions. The method also includes providing hydrogen to the anode side of the fuel cell stack at system shut down while the membrane electrode assemblies are saturated without stack loads being applied so that the hydrogen crosses the cell membranes to the cathode side and reacts with oxygen to reduce stack contaminants.
摘要:
A system and method for increasing the temperature of a fuel cell stack quickly, especially at cold stack start-up. The method includes determining whether the fuel cell stack is below a first predetermined temperature threshold, and, if so, starting a cooling fluid flow through the stack and engaging a shorting circuit across the stack to short circuit the stack and cause the stack to operate inefficiently. The method then determines a desired heating rate of the fuel cell stack and calculates a cathode airflow to the fuel cell stack based on the desired heating rate. The method reduces the flow of cathode air to the stack if a minimum cell voltage is below a predetermined minimum cell voltage threshold and disengages the shorting circuit and applies vehicle loads to the stack when the stack temperature reaches a predetermined second temperature threshold.