Parallel Hybrid Propulsion System for a Regional Turboprop: Conceptual Design and Benefits Analysis

A conventional, high-wing, regional aircraft in the 30-50 passenger class with a parallel hybrid electric turboprop propulsion (PHET) system has been studied. The PHET system is comprised of 2 under-wing engines assisted by 750 kW motors, each integrated by a combining gearbox (CGB) driving the PHET propeller. The electric drive train (EDT) further consists of 2 motor drives, a 1000 V electric distribution system, a 500 kWhr battery pack capable of 1500 kW discharge (c-rate of 3) and a thermal management system (TMS) capable of maintaining component temperatures at levels required for high life. The flat rated PHET system core engines, sized for cruise power are significantly undersized for take-off and climb; thus the make-up power comes from the CBG mounted motors fed by a ground-charged battery pack. The EDT and TMS weight and performance analysis as well as the overall propulsion system performance analysis is described. One mission concept of operations (CoO) is analyzed with the resultant fuel and energy consumption quantified and compared to a conventional propulsion system-based aircraft. The 250 nm mission CoO carries only the battery pack mass required for boosted take-off and climb, with all energy for cruise supplied by on board fuel. A fuel burn reduction of 30% and energy reduction of 25% are predicted for this CoO.