Preliminary Aeronautical Design Considerations of “High NOS” SOFC/GT Hybrids

Aerovehicular application of solid oxide fuel cell/gas turbine (SOFC/GT) auxiliary power units (APUs) is a promising concept that may significantly aid the advent of next-generation, environmentally benign aircrafts. The hybrid concept may not only be a novelty, but a necessity, for viably realizing the benefits of fuel cells on-board. A generic design concept is proposed wherein the strategic integration of the cell stack with a bottoming turbine for APU duty, along with regenerative fuel recirculation, could be used to foster larger reactant “numbers-of-stoichs” (NOS) levels within the stack. This may engender larger gravimetric power densities, capacitance for load following and thermal reliability. Fuel utilization/NOS may then be a significant design degree-of-freedom to include within the design process.