Performance analysis of a turbofan engine integrated with solid oxide fuel cells based on Al-H₂O hydrogen production for more electric long-endurance UAVs

This work investigates a turbofan engine (a type of gas turbine, GT) integrated solid oxide fuel cells (SOFCs) based on Al-H₂O hydrogen production to reduce the specific fuel consumption (SFC) and meet the increasing power demand in unmanned aerial vehicles (UAVs). The new engine uses an Al-H₂O reactor to produce hydrogen for the SOFCs. To analyze the performance of the engine, the thermodynamic models of the turbofan engine, the Al-H₂O reactor, and the SOFC are established and the key models are verified. The performance comparisons between the SOFC-GT engine and the turbofan engine under different electric power fractions are carried out. It is found that the SFC of the SOFC-GT engine can be reduced by 10.30%, 14.41%, 18.98%, and 24.08% compared with the turbofan engine when the electric power fractions are 15%, 20%, 25%, and 30% respectively. The effects of engine parameters such as bypass ratio, fan pressure ratio, compressor pressure ratio and turbine inlet temperature, reactor parameters such as H₂O-to-Al-weight ratio, and aircraft flight parameters such as flight altitude and Mach number on the performance of the new engine are studied. The preliminary results are as follows: (1) Under the design conditions, the SFC, the specific thrust, the thermal efficiency, the propulsion efficiency, and the overall efficiency of the SOFC-GT engine could reach 16.71 g/(kN·s), 222.47 N·s/kg, 57.62%, 42.63%, 28.91%. (2) Bypass ratio and fan pressure ratio have a great influence on the performance. By adjusting these two parameters, the SFC can be reduced by more than half. (3) Compared with thermal efficiency, propulsion efficiency has a greater impact on the performance of the engine. (4) The increase of the H₂O-to-Al-weight ratio is unfavorable to the performance of the engine. The optimal interval can be preliminarily determined between 3 and 4. (5) To achieve low SFC, high economy, and long endurance, while maintaining high efficiency and high specific thrust, the aircraft needs to be designed with high flight altitude and low Mach number.