Aerodynamic Design and Experimental Validation of a 1/10th Scale Notional Proprotor for a 30-Seat Tilt-Rotor eVTOL Aircraft

The paper presents the design, optimization and experimental investigation of scaled proprotors for the Sora S-1, a 30-seat eVTOL aircraft. The study includes an investigation into the aerodynamic and aeroacoustic performance of proprotors with varying blade numbers, designed for consistent thrust and a given rotational speed, allowing fair comparison between designs. An in-house Blade Element Momentum Theory-based tool was used to design the proprotors, with a weighting for low noise in the hover condition, and validated for aerodynamic performance through scaled experimental testing. Supporting CFD analysis is used to highlight the aerodynamic mechanisms linked to the aeroacoustic trend. It is revealed that the tonal noise scales with the sixth power of the tip Mach number, independent of blade number. In contrast, broadband noise follows a scaling law between the fourth and fifth power of tip Mach number, which varies with blade number. While increasing the blade count does not systematically raise the overall broadband noise level, higher blade numbers have been shown to enhance tip-vortex interactions, which can influence broadband characteristics.