Efficiency Analysis of Hybrid Electric Propulsion System for Commuter Airliners

The paper presents the study of conceptual design of hybrid propulsion system for 9–19 passenger capacity commuter airliner. As a prototype a twin-engine turboprop aircraft is considered. The engines for such aircrafts must have the power to ensure a short take off, but at cruise speed the engine power is excessive which leads to increased fuel consumption. The hybrid propulsion system considered in the paper consists of two propellers directly driven by two electric motors with maximum power of 550 kW each. The electric power is provided by a power unit that includes batteries and one or two turboshaft engine rotating generators. At take-off the electric motors are supplied by batteries and generators simultaneously. Gas-turbine generators should provide enough power for cruise flight and batteries charging at minimal fuel consumption. The power of each generator at the ground for two-generator case should be 550 hp each, and for one-generator case should be 1100 hp. The numerical model uses predictions for year 2020, 2025 and 2030 of the characteristics for gas turbine, electric generator, electric motor, the control system, and batteries. The modelling of typical airplane flight cycle with hybrid propulsion system characteristics predicted for 2025-2030 time period shows 1–3% increase in fuel efficiency for two-generator case. For the same period, the one-generator case hybrid propulsion system will have less weight and 9–10% fuel consumption decrease. All of these lead to 16% airplane range increase in comparison with the traditional propulsion system.