This work investigates the feasibility of using engine-integrated catalytic partial oxidation reactors (CPOX) and solid oxide fuel cells (SOFCs) to increase the range/endurance of sensor-laden aircraft like unmanned air vehicles that have relatively large electrical power needs. Thermodynamic models for SOFCs, CPOx reactors, and three gas turbine engine types (a turbojet, a low bypass ratio turbofan, and a high bypass ratio turbofan) are developed and validated. A model of the gas turbine - fuel cell integration shows that 4% thermodynamic improvement is possible over traditional engine-generator approaches for a vehicle with a 10% electric power fraction (i.e., the ratio of electrical to total (electrical + propulsive) power demand). This improves to a 12% or 29% advantage at 30% and 50% power fractions, respectively. Preliminary estimates show that the mass of the SOFC systems is large, but the system has not yet been optimized and several strategies for achieving significant mass reductions are discussed. These include optimizing the geometry of the fuel processor and fuel cell elements, lowering the cell operating voltage, and operating at reduced fuel utilization. Another important finding is that the CPOX must be operated leaner as pressure is increased in order to avoid graphite formation. Also, small engine compression ratios result in flows that are not hot enough to sustain SOFC operation.
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