Parallel Hybrid-Electric Operation of a Turbofan Engine during Climb and the Influence on Stability and MRO

Abstract

This study aims at analysing hybrid-electric operation of a twospool high-bypass turbofan for a narrow-body aircraft during the climb trajectory. Boundaries of safe hybrid-electric operation are investigated and methods for controlling the electric power along the trajectory are demonstrated. This is crucial, as hybrid-electric operation induces throttling of the low-pressure compressor and the effect intensifies with increasing altitude during climb. Furthermore, operational loads are extracted and applied to lifetime prognostics for the turbofan engine, electric machine and power electronic system. The results show an influence of the hybridisation on the gas turbine by nearly −20% in SVR and +7% in TOW. Higher electric assistance unloads the gas turbine and increases operational time, but requires higher bleed air extraction for compressor stability. The electric drive train shows variations in lifetime consumption up to 150% for the electric machine and 135% for the power electronics capacitors. The semiconductors show strong interdependence with small scale temperature cycling of the operating profile, which shows the need for more sophisticated thermal mission modelling.