Experimental and computational aeroacoustic and aerodynamic evaluations of five eVTOL propeller blades

Drones generate significant noise during their operation, limiting their usage in noise-sensitive environments. This study compared four pairs of eVTOL propeller blade designs from Texas High Energy Materials, LLC against a commercial baseline to reduce noise while maintaining aerodynamic efficiency. Experimental measurements and computational simulations were used to evaluate the aeroacoustic and aerodynamic performances. Experimental data was processed to obtain spatially averaged auto-spectra and overall sound pressure levels. It was shown that one of the proprietary blades presented the quietest overall noise level, generating an overall 14.9 dBA noise reduction compared to the commercial blades with an overall level of 80.8 dBA. Comparisons between measured and simulated data showed a 3.4 - 8.8 dBA difference, with computational models consistently underpredicting dominant noise peaks at blade passing frequencies. Although these computational models are useful in optimizing the designs where relative performance improvements are only important, the dBA difference can be reduced through improved finite element mesh quality in future simulations. Aerodynamic predictions indicated that the quietest blade design was the most energy-efficient, producing the highest average lift-to-power ratio of 0.95 N/W. Finally, experimental Nearfield Acoustic Holography results suggest that simple rotating monopole models can be used to represent the propeller noise effectively.