Within the IMOTHEP project, Bauhaus Luftfahrt evaluated the fuel burn reduction potential of a regional turboprop concept with a hybrid-electric propulsion architecture for entry into service in 2035+. An electrically assisted turboshaft engine was the focus of the investigation. Using electrical assistance could significantly improve overall propulsion efficiency at the cost of increased overall propulsion system mass.
The aircraft configuration addressed the challenges associated with an additional electrical energy source. For e.xample, failure cases that can lead to the loss of electrical power were considered for propulsion system sizing, since this can have a negative impact on engine performance in crucial flight phases. Additionally, an innovative thermal management concept was investigated. It was found that combining a conventional ram air heat exchanger with a wing surface heat exchanger leads to a smaller penalty compared to a conventional thermal management system. Integrated aircraft design studies aimed to narrow down uncertainties when analysing the potential of hybrid-electric propulsion. The final configuration achieved a block fuel reduc- tion of 9.6 % for a 200 nautical mile (nmi) typical mission compared to a conventional reference aircraft. Here, 15 % of the required power was supplied electrically through an on-board battery during take-off, climb, and cruise. For the 600 nmi design mission, however, mission block fuel increased.
It was found that the limiting factor for fuel reduction potential is the battery’s gravimetric energy density and choosing an optimal mission hybridisation strategy is key to achieve maximum fuel burn reduction. The final results served as a reference for the project’s hybrid-electric propulsion roadmap
Investigation and Maturation of Technologiesfor Hybrid Electric Propulsion – A holistic approach towards hybrid-electric propulsion.