A Study of the Electric Drive of Parallel Hybrid Electric Power Plants

An approach to the implementation of an electric drive of parallel circuit hybrid electric plants (HEPs) is considered. The characteristics of an HEP with a turbocharger and free turbine drive are compared. The key difference between the considered complexes is the installation location of the electric machine (EM): in the first case, the EM drives the compressor section; in the second, the free turbine shaft does. A search for optimal hybridization—the ratio between electrical and thermal energy, taking into account the parameters of the thermal control system—is performed. The range of hybridization variation is from 5 to 25%. The analysis of the results shows that hybridization of aircraft (ACs) significantly reduces fuel consumption per flight cycle. The break-even point for the turbocharger drive scheme corresponds to a hybridization of 18%; for the free turbine drive scheme, this value is 20%. The HEP scheme with a turbocharger drive at the maximum considered value of hybridization (25%) provides a reduction in fuel consumption per flight cycle by 13%. The parallel hybrid system with a free turbine drive reduces fuel consumption by 5%. An increase in hybridization requires an increase in the energy stored onboard the aircraft, which, in turn, requires a high specific energy capacity of batteries (up to 600 W h/kg) and a specific power of the electric drive (more than 10 kW/kg).