| Abstract [eng] |
Purpose of this work was to evaluate the feasibility of using Distributed Electric Propulsion (DEP) as a single means of propulsion for ultralight aircraft. While some single seat aircraft that do not strictly fall into fixed wing ultralight category, but utilize DEP, are emerging, most of the current all-electric ultralight aircraft designs still use single propeller/motor configurations. Utilizing DEP has the potential to enhance lift by, depending on configuration, increasing the pressure on the upper surface of the wing and taking advantage of Coandă effect, or by Boundary Layer Ingestion (BLI). Different propulsor and placement options were analysed and preliminary configuration using four off-the-shelf Electric Ducted Fans (EDFs) positioned on the upper leading edge of the wing was proposed on the concept high-wing ultralight aircraft. Proposed configuration was based on the assumptions that providing direct airflow on the upper surface of the wing (Upper Surface Blowing) and utilizing Coandă effect will significantly increase the upper wing pressure, make the airflow more laminar and substantially increase the lift compared to conventional single propeller configuration. These assumptions were tested by carrying out Computational Fluid Dynamics (CFD) simulations using Ansys Fluent software. Results showed that even with lower total dynamic thrust of DEP configuration, it was able to provide noticeably greater lift compared to baseline single propeller configuration making it a feasible alternative. It was also noticed that nacelle geometry plays a big role in the pressure generation, initial assumption that open nacelles providing airflow on larger area of the wing were not proven. Further research on nacelle geometry was suggested, especially on closed high aspect ratio exit nozzles, as these could futher increase the lift. Lastly, economic considerations on using DEP were discussed. It was determined that overall aircraft costs would be higher due to the current high cost of larger diameter EDFs, however, it is feasible to utilize investments, common for electric aviation projects, for design and manufacturing stage and buyers could still be attracted by lower operating and maintenance costs, as well as improved aerodynamic characteristics. |
