3-D Modeling of Stack-Integrated Autothermal Reformer and Solid Oxide Fuel Cell for High-Power-Density Aviation Applications

Solid oxide fuel cells (SOFCs) with high energy conversion efficiency offer a possible solution to produce electric power for aircraft in hybridized gas-turbine propulsion operating on future sustainable fuels such as renewable liquified natural gas (LNG). To apply SOFCs in conjunction with a gas-turbine, novel SOFC architectures must be implemented to enable an SOFC to work directly with compressor outlet temperatures, pressures, and high mass fluxes. Fuel and air pre-processing must provide SOFC inlet temperatures and gas compositions that enable high SOFC stack power (> 1 kW/liter). This work explores the integration of an exothermic autothermal reformer/heat exchanger (ATR/HX) for fuel and air pre-processing and a solid-oxide fuel cell (SOFC) for operation in the flow path of an aviation gas turbine system. The study focuses on liquified CH4 as a potential renewable aviation fuel and the use of partial anode-exhaust recycling to provide an ATR inlet stream mixed with some bleed air to provide mildly exothermic fuel reforming and air preheating for inlet temperatures adequate for reliable SOFC operation. A single cell channel representing a repeating unit inside a stack is simulated in ANSYS Fluent to predict the performance and down-the-channel profiles for the integrated, inline ATR/HX with both YSZ-electrolyte and GDC-electrolyte SOFCs. Lower operating temperatures and higher power densities of GDC-based SOFCs allow better integration of the ATR/HX at lower air-to-fuel ratios (eair). The integrated system is studied to identify preferred operating conditions for the ATR/HX/SOFC for stack testing and identifying possible implementation into dynamic gas-turbine flow pathways.