Business Aviation Turbofan Efficiency Improvement by Electrical Assistance During Transient Operations

The recent growth in popularity of business jets, driven by increased demand for operational flexibility, reflects their capability to offer long-range, high-speed, high-altitude, and comfortable travel. However, they produce high greenhouse gas emissions on a per-passenger basis compared to commercial aviation. Consequently, the growing demand, combined with the collective goal of achieving net-zero carbon emissions by 2050, heightens environmental concerns and puts pressure on the industry to innovate towards sustainable propulsion systems. In the short to medium term, fully electric or hydrogen propulsion remains unsuitable due to limited battery energy capacity, the need for major airframe redesigns, and the lack of alternative energy infrastructure at the airports most frequently used by business jets. These limitations impose significant performance and flexibility constraints, making hybrid-electric propulsion a promising alternative. This study investigates the Electrically-Assisted Turbofan, a mild hybrid-electric concept tailored for business jet applications. The analysis is based on the Honeywell HTF7000 turbofan, used, among others, in the Challenger 300 aircraft. Supplying electrical power to the high-pressure spool during acceleration reduces the need for large stall margins traditionally required for rapid engine acceleration. This relaxation enables a turbomachinery redesign that improves high-pressure compressor efficiency and pressure ratio, reducing cruise-specific fuel consumption by up to 2.0 %. Similar improvements are achieved in other steady-state flight phases. These potential performance gains are obtained with an electrical energy input of 378 W h (1361 kW s) and a peak power demand of 415 kW (557 hp) during a single acceleration phase. Comparison with the baseline turbofan shows that the redesigned Electrically-Assisted Turbofan maintains full thrust capability and compliance with acceleration requirements. The conceptual analysis demonstrates that electrical assistance during transient operations requires a relatively low electrical energy input, although at high discharge rates, and can yield non-negligible steady-state fuel savings. These results highlight the potential of the mild hybrid-electric concept for business aviation.