Evaluation and Optimisation of Dual Role Electrical Drive and Regeneration Propellers

This study delves into the innovative realm of in-flight energy regeneration within electric-powered aircraft, marking a significant stride towards sustainable aviation practices. A novel toolset for evaluating inflight regeneration of electric or hybrid-electric propeller-driven aircraft across various flight missions is introduced. The toolset, versatile in its application, can function as a standalone program, integrate into existing propeller design frameworks, or enhance aircraft sizing tools. When the propeller operates as a windmill during descent, the motor transitions into a generator, recharging the batteries. Aerodynamic performance is evaluated using the Blade Element Method, supplemented by Computational Fluid Dynamics (CFD) and validated through wind tunnel experiments. Results emphasize the necessity of CFD for accurately predicting regenerative torque during flow detachment. Three novel energy recovery metrics are proposed: (NEE), quantifying regenerated energy relative to expended energy; Extended Range Ratio (ERR), indicating range gain through regeneration; and Payload Efficiency Ratio (PER), measuring payload transport efficiency considering recovered energy. Analyses of two case study aircraft demonstrate varying regeneration potential based on mission profiles. A light electric aircraft achieves 9.6% NEE in traffic patterns, while a medium hybrid-electric aircraft achieves 6.1% NEE on a short-haul island transfer. Cross-country missions show decreased NEE but improved ERR and PER values. Further optimisation is explored through a dedicated windmill recuperation propeller, revealing that variable-pitch propellers recover up to 71% of maximum regeneration potential, significantly outperforming fixed-pitch designs. This study demonstrates that integrating regenerative capabilities into electric aircraft powertrains enhances energy efficiency and operational flexibility. Additionally, regeneration offers a potential alternative to conventional air brakes, further optimising aircraft performance.<p></p>