Impact of Distributed Propulsion on the Design of a Hybrid Electric Aircraft

Abstract

The study presents a novel methodology for the conceptual design of a Hybrid Aircraft featuring Propulsive devices distributed along the wingspan of the wing. Distributed Propulsions is a solution that can theoretically augment high lift capabilities so that the resulting needed wing loading can be lowered; in addition, electric propulsion can potentially enable the introduction of such solutions with a relatively low penalty in terms of increased structural weight because of the relative lightness and compactness of electric motors. The proposed sizing procedure consists of several intermediate steps: first, the thrust, lift and drag decomposition are modified to take the effect of aerodynamic interaction into account, leading to a set of modified flight performance constraining equations. Subsequently, a hybrid powertrain model, containing information and operating characteristics extrapolated by the components used in the Mahepa project, allows to determine a series of component-power oriented power loading diagrams; in addition, the energy requirements can be calculated on the basis of a certain mission profile and energy/power management assumptions. Finally, class I weight estimation are used to determine the Maximum Take Off Weight of the aircraft through an iterative procedure. A second sizing procedure, that relies on the use of a lifting-line model where propellers are represented by actuator disks. Two study cases are considered: a CS25 regional aircraft and a CS23 commuter. Preliminary results suggest a slight reduction of the payload-range energy efficiency.