Conceptual Assessment of Hybrid Electric Aircraft with Distributed Propulsion and Boosted Turbofans

This paper presents the results of a study into the effect of distributed hybrid-electric propulsion on aircraft performance and characteristics. To size these aircraft, a new preliminary sizing method for hybrid-electric aircraft with distributed propulsion, including aero-propulsive interaction, is combined with a modified Class-II weight estimation method where energy consumption is estimated through a mission analysis method. Comparison of the predictions from these new methods to the predictions from a traditional sizing method has shown to be within 5% agreement for a single-aisle aircraft powered by conventional turbofans in terms of wing loading, energy consumption and maximum take-off weight. A boosted turbofan aircraft as well as two aircraft with different distributed, hybrid-electric propulsion systems have been assessed for a 150-pax aircraft designed for a harmonic range of 800nmi. Each of these aircraft designs showed significant increases in propulsion system mass (up to 700%). The distributedpropulsion aircraft showed increases in energy consumption of 34% and 51%, respectively, over the conventional turbofan aircraft. However, the boosted-turbofan aircraft showed a 10% decrease in energy consumption and a 3% reduction in maximum take-off weight. Future studies have to be performed exploring the design space, including all powertrain components, thermal management components, mission parameters and propulsion system layout.