The world is moving towards sustainability and there is immense pressure on Aerospace Industry to reduce its emissions to contribute to a carbon-neutral world. However, maturing gas turbine technology is a big bottleneck towards this goal and hence, this project focuses on the technical and economic feasibility of a new type of propulsion system, called Solid-Oxide Fuel Cell- Gas Turbine or SOFC-GT hybrid propulsion system. SOFC- GT, even though being a low TRL technology, has the potential to reduce fuel consumption, emissions, and operation costs, making it a suitable candidate for a future propulsion system.

This research concludes that in order to achieve the full potential of the SOFC-GT hybrid, engine parameters like BPR, FPR and cooling air requirements need to be changed. The Thrust-Specific Fuel Consumption (TSFC) for the propulsion system has decreased by 6.03% and 19.89% for 1 MW and 4 MW fuel cell power output in Off-Design (Cruise) condition. Along with this, core mass flow rate or size, cooling air requirement and Turbine Inlet Temperature for Cruise condition has decreased. The emission results show that the NOx emissions have been reduced by 29.11% and 78.05% respectively. Sensitivity analysis shows that the thermodynamic efficiency is most sensitive to engine parameters but the impact of fuel cell parameters is increasing as the fuel cell power output is increased.

The economic analysis done in this study shows that the SOFC-GT hybrid is not feasible for the commercially available fuel cell because of the substantial increase in weight of the propulsion system. However, the propulsion system will become feasible at the fuel cell system specific power of 2.30 kW/kg and 2.10 kW/kg for no emission tax and highest emission tax scenario respectively at a fuel price of $ 6/kg. Along with this, increasing the fuel cell power output leads to the increase in required specific power for fuel cell or has a negative impact on the overall economics. The overall economics of the aircraft is most sensitive to aircraft parameters but increasing the fuel cell power output decreases sensitivity substantially. In the end, the emission has a low impact on the overall economics of the aircraft.

This research shows that it is possible to integrate a SOFC with the turbofan if the fuel cell technology improves in the future. Along with this, the research provides multiple novel methodologies for technical and economic analysis of the SOFC-GT hybrid.

Solid Oxide Fuel Cell (SOFC) systems for aviation applications have been considered for their use as APUs or powertrains, as standalone systems or in combination with gas turbines, and both fueled by reformed Jet-A or by hydrogen. Most existing studies focus on powertrain performance modelling. In this work, traditional tube-and-wing regional aircraft sizing methodologies are modified to account for liquid hydrogen fuel and SOFC-GT-Battery hybrid electric powertrains. Methodologies for powertrain modelling, power sizing, energy sizing, weight calculation and system integration have been derived, implemented, verified, validated when possible, and used to assess several study cases. Considering state-of-the-art metal-supported planar ITSOFC technology installed in a 50-seat regional aircraft as test case, it is concluded that current SOFC system power density is not sufficient to achieve MTOW values similar to conventional kerosene-powered regional aircraft. This work serves as a baseline for the integration of sizing methodologies for SOFC-GT-Battery powertrains into aircraft conceptual-to-preliminary design tools.