Performance Investigation of Cycle-Integrated Parallel Hybrid Turboshafts

Motivated by the long-term target settings for research and innovation in Europe and in North America, initial investigations of parallel hybrid electric power plant systems have indicated significant in-flight fuel reduction potentials for short range air transport. Based on this topology, a special variant, namely the cycle-integrated parallel hybrid (CIPH), has been investigated. In this special configuration, electric motors supplied by batteries are powering an array of compressor stages of a power plant that are mechanically decoupled from the turbine section. The potentials with regard to in-flight fuel reduction and efficiency improvement of this concept are derived for a 12-ton-helicopter accommodating 19 passengers on a 450 nm mission. For the presented CIPH concept, the axial compressor section of a baseline turboshaft (TS) delivering a maximum shaft power of 3300 kW is electrified with the help of linear electric motors (LEMs). The highest potential for this arrangement was identified in part load for moderate degrees of power hybridization—the share between installed electric power and total power—of around 20%. The first assessment has revealed that this additional degrees-of-freedom allows to almost double the overall efficiency, compared to a conventional power with same technology time horizon, and a reduction in power-specific fuel consumption (PSFC) of roughly 45%. The range capability of a hybrid-powered helicopter has been decreased by more than 50%, mainly driven by the battery mass. However, a fuel burn, and thus, in-flight CO₂ reduction of more than 40% against the reference at decreased mission range have been found.