Cycle-integrated parallel-hybrid power plant
For the realisation of hybrid-electric aircraft, there are different topologies, for example, serial, parallel or serial-parallel available to combine energy carriers like kerosene and batteries. The classical parallel hybrid topology, where usually an electric motor assists a gas turbine in supplying mechanical power to the power shaft, could be shown in the last Yearbooks as a most promising solution for aircraft applications. Based on this topology, Bauhaus Luftfahrt has investigated a special variant, specifically the cycle-integrated parallel hybrid.
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 fuel reduction and efficiency improvement were initially investigated within the 7th European Framework Programme project E-BREAK. In this project, Bauhaus Luftfahrt performed conceptual studies on a turboshaft platform for a helicopter application, where the highest potential for this arrangement was expected in part load for moderate degrees of power hybridisation – the share between installed electric power and total power – of around 20 %. The first assessment has revealed that this additional degree of freedom allows to almost double the efficiency, compared to a conventional power plant, and a reduction in power-specific fuel consumption 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, at decreased mission range, a fuel burn and, thus, CO2 reduction of more than 40 % has been found.