Abstract: Fuel Cell Powering system and method minimizing the number of motive drive sources and controlling fuel/air ratios by employing differentials including variable speed mechanisms between compressors and between compressors and expanders; by utilizing flow control devices for separate fluid streams including separate exhaust streams; by utilizing independent compressor/expander chambers; and by injection of water into exhaust streams prior to expansion.

Abstract: Variable valve timing is provided to control compressors and expanders in a fuel cell powering system in order to provide for matching the displaced volume of the compressor and expander over a range of pressure delivery requirements. A movable timing edge is positioned adjacent inlet and/or discharge ports to cooperate with a movable valve element with inlet and outlet slots to adjust the time and time period of open and close operations. Several embodiments are presented.

Abstract: Fluid displacement apparatus with a set of opposing pistons in traveling chambers and a set of opposing pistons in stationary bores; a second embodiment with all pistons in traveling chambers; a third embodiment with all pistons in stationary bores. In each embodiment the displacement of the pistons can be different and the displacement can be variable. The apparatus is connected to a fuel cell stack to supply compressed gaseous fluid from a portion of the chambers and receive exhaust from the fuel cell stack in other chambers to perform an expander function. The apparatus can also be connected to a fuel cell stack and a reformer to supply compressed gaseous fluid to both and to receive exhaust from both as an expander. The chambers are sized differently to provide a pressure ratio across the fuel cell stack.