Energy Management Strategies for different Aircraft Parallel Hybrid-Electric Propulsion Systems

Civil aircraft activities are steadily growing and are expected to increase by 2% per year by 2050. The guidelines of Flightpath 2050 have been established to mitigate CO2, NOx emissions, and noise of the aircrafts impact. To fulfill these goals, efforts must be directed towards multiple areas, including improving engine efficiency, optimizing aerodynamics, refining design, and developing innovative propulsion systems. Since full-electric propulsion options are still unsuitable due to the considerable weight of the batteries, despite local zero emissions, this work focuses on different parallel hybrid-electric propulsion systems (P-HEPS). A novel methodology for preliminary sizing of this architecture coupled with a point-mass aircraft dynamical model is presented. This procedure is developed for ultralight and general aviation applications. The proposed approach considers three different engines connected to the same electric machine: by simulating a short mission, the results in terms of fuel consumption and battery state of charge have been compared with a fully thermal solution, assumed as a benchmark. Moreover, both adaptive and non-adaptive equivalent consumption minimization strategies (ECMS) are adopted to optimize energy management during the flight mission. Each parallel configuration has guaranteed lower fuel and primary energy consumption than the fully thermal scheme. The main outcomes of this study show that an optimized hybrid-electric propulsion design, combined with an efficient energy management strategy, can reduce CO2 emissions by approximately 6% with a full-hybrid solution and up to 24% with a plug-in system.