Pressurized Testing of Tubular Solid Oxide Fuel Cells Using Ammonia and Jet Fuel for Development of a Hybrid Gas Turbine Propulsion System Model

David Shafer

The NASA CarbonLess Electric AviatioN (CLEAN) project aims to create the next generation of passenger aircraft propulsion systems. The CLEAN project proposes a solid oxide fuel cell (SOFC) gas turbine (GT) turbofan engine that leverages thermal synergies between SOFCs and a gas turbine for higher efficiency. This hybrid engine could operate on ammonia, jet fuel, and hydrogen. Using requirements laid out by the CLEAN project and limitations from adapting the engine to a Boeing 737 airframe, a sizing model was generated for the SOFC-GT engine. This sizing model was optimized using a genetic algorithm and simplified to a surrogate model that was then implemented into an overarching CLEAN SOFC-GT thermodynamic model. An SOFC performance model was also integrated based on data from novel pressurized SOFC performance testing. This testing evaluated SOFC performance at various temperatures and pressures using hydrogen, simulated ammonia, ammonia, and jet fuel. Ammonia testing showed that ammonia-fed SOFC performance was marginally worse compared to hydrogen performance; however, the addition of a nickel foam catalyst was found to make that performance difference negligible. Desulfurized jet fuel testing showed that jet fuel operation required careful control to prevent carbon formation and to obtain stable performance. Ammonia and hydrogen variants of the CLEAN SOFC-GT thermodynamic model were successfully compared using the experimental data and sizing model generated in this work. Pressurized jet fuel testing was found to be unpredictable, so creation of a jet fuel variant was held off for future refinement before model integration. This work demonstrated the viability of ammonia and hydrogen operation within the CLEAN SOFC-GT framework and identified the operational challenges that must be resolved to enable the creation of a reliable jet fuel model.