Enabling the Decarbonization of Regional Air Transport with Series Hybrid Electric Propulsion

The aviation industry faces significant environmental challenges, prompting the implementation of regulations to mitigate the adverse effect of carbon-based energy and associated emissions. While electrified flight is a promising pathway, limitations in specific energy density of batteries narrow down the application space to commuter and regional classes. Towards that direction, this work investigates the design and operation of a series hybrid electric 30-passenger regional aircraft. A multi-disciplinary framework is utilized, comprising modelling approaches for multi-point thermal engine design, physics-based electrical component sizing and performance, aircraft sizing, mission design, and environmental assessment. Distributed propulsion with up to three propellers per wing is evaluated for aerodynamic benefits. With optimal wing redesign, drag reduction benefits only reach 1\% for the selected aircraft class and flight velocities. Variable free power turbine speed operation is promising in reducing engine mass and improving performance of both thermal and electrical power systems. A combination of hybridization during take-off, climb and cruise defines the optimal design and operation guidelines for the hybrid concept. However, due to the increased mass of the battery and electrical power system, block fuel benefits only in the order of 5\% are reported, compared to a turboelectric aircraft. When compared with a conventional configuration of same entry-into-service year, the series concept is outperformed in the examined range of battery assumed technologies.