Abstract: A diagnostic system for determining whether a rotor shaft of a compressor is unbalanced. The compressor includes a displacement sensor that measures the displacement of the rotor shaft as it is rotating. The sensor dynamic frequency signal is sent to a bandpass filter that filters out an eigen-frequency frequency that is a function of shaft elasticity and rotor dynamics. The filtered frequency signal is then rectified by a rectifier to make the filtered frequency signal positive. The rectified signal is then passed through a low pass filter that converts the rectified signal to a DC signal. The DC signal is then sent to a controller that determines if the amplitude of the signal is above a predetermined threshold, which indicates a problem with the balance of the compressor.

Abstract: A diagnostic system for determining whether a rotor shaft of a compressor is unbalanced. The compressor includes a displacement sensor that measures the displacement of the rotor shaft as it is rotating. The sensor dynamic frequency signal is sent to a bandpass filter that filters out an eigen-frequency frequency that is a function of shaft elasticity and rotor dynamics. The filtered frequency signal is then rectified by a rectifier to make the filtered frequency signal positive. The rectified signal is then passed through a low pass filter that converts the rectified signal to a DC signal. The DC signal is then sent to a controller that determines if the amplitude of the signal is above a predetermined threshold, which indicates a problem with the balance of the compressor.

Abstract: A diagnostic system for determining whether a rotor shaft of a compressor is unbalanced. The compressor includes a displacement sensor that measures the displacement of the rotor shaft as it is rotating. The sensor dynamic frequency signal is sent to a bandpass filter that filters out an eigen-frequency frequency that is a function of shaft elasticity and rotor dynamics. The filtered frequency signal is then rectified by a rectifier to make the filtered frequency signal positive. The rectified signal is then passed through a low pass filter that converts the rectified signal to a DC signal. The DC signal is then sent to a controller that determines if the amplitude of the signal is above a predetermined threshold, which indicates a problem with the balance of the compressor.

Abstract: A humidity sensing device for measuring a humidity of a reactant stream in a fuel cell system is provided. The humidity sensing device includes a humidity sensor coupled to a sensor housing. The sensor housing is adapted to selectively move the humidity sensor to an operating position and to a non-operating position in the fuel cell system. A fuel cell system and a method employing the humidity sensing device in the fuel cell system is also provided.

Abstract: A humidity sensing device for measuring a humidity of a reactant stream in a fuel cell system is provided. The humidity sensing device includes a humidity sensor coupled to a sensor housing. The sensor housing is adapted to selectively move the humidity sensor to an operating position and to a non-operating position in the fuel cell system. A fuel cell system and a method employing the humidity sensing device in the fuel cell system is also provided.

Abstract: A control valve is disclosed having a passage formed therein defined by an inner surface, the control valve includes at least one enhanced surface, a liner, or a combination thereof to militate against ice formation thereon and adhesion of the ice thereto.

Abstract: A diagnostic system for determining whether a rotor shaft of a compressor is unbalanced. The compressor includes a displacement sensor that measures the displacement of the rotor shaft as it is rotating. The sensor dynamic frequency signal is sent to a bandpass filter that filters out an eigen-frequency frequency that is a function of shaft elasticity and rotor dynamics. The filtered frequency signal is then rectified by a rectifier to make the filtered frequency signal positive. The rectified signal is then passed through a low pass filter that converts the rectified signal to a DC signal. The DC signal is then sent to a controller that determines if the amplitude of the signal is above a predetermined threshold, which indicates a problem with the balance of the compressor.

Abstract: A fuel cell system that can be used to power a vehicle is disclosed. The system includes a fuel cell stack, which uses hydrogen and an oxidizer to generate electricity, and a re-circulation loop that returns unreacted hydrogen to the fuel cell stack. The system includes a hermetically sealed assembly having a blower portion that pressurizes hydrogen in the re-circulation loop and a motor portion that drives the blower. The system also includes a source of make-up hydrogen for replenishing hydrogen in the re-circulation loop. The source introduces make-up hydrogen in the motor portion of the assembly at a pressure greater than the pressure in the blower portion of the assembly. Consequently, make-up hydrogen flows from the motor portion of the assembly into the blower portion assembly where it mixes with components in the re-circulation loop. A method of replenishing hydrogen in the fuel cell stack is also disclosed.

Abstract: A fuel cell system that can be used to power a vehicle is disclosed. The system includes a fuel cell stack, which uses hydrogen and an oxidizer to generate electricity, and a re-circulation loop that returns unreacted hydrogen to the fuel cell stack. The system includes a hermetically sealed assembly having a blower portion that pressurizes hydrogen in the re-circulation loop and a motor portion that drives the blower. The system also includes a source of make-up hydrogen for replenishing hydrogen in the re-circulation loop. The source introduces make-up hydrogen in the motor portion of the assembly at a pressure greater than the pressure in the blower portion of the assembly. Consequently, make-up hydrogen flows from the motor portion of the assembly into the blower portion assembly where it mixes with components in the re-circulation loop. A method of replenishing hydrogen in the fuel cell stack is also disclosed.