Acoustics comparison of a novel reduced tip vortex rotary blade and a traditional blade

Abstract

Acoustics data collection was performed in an anechoic chamber for two propeller blade types, one traditional power optimized blade and one novel blade designed to reduce generated tip vortex strength. Both blade types had a 7.82” radius, a 2.25” root chord, a taper ratio of 2, a thrust coefficient of 0.003, and used an Eppler E387 airfoil. The blades were held at a steady 5000 rotations per minute as data were captured at 11 different microphone locations downwind of the rotor disc. Data were processed using a Fourier transform and analyzed. Key peaks in the processed data were identified and compared for each blade type and microphone location. Compared to the power optimized blade, the reduced vortex blade was found to have a greater number of distinct peaks. Additionally, for peaks that were present in the acoustic signatures of both blade types, the reduced vortex blade’s peaks were slightly greater in magnitude on average.