Broadband Noise Sources for Electric Vertical Take-Off and Landing Vehicle Rotor Designs

open_access
Open Access
Author:
Modi, Prem
Area of Honors:
Aerospace Engineering
Degree:
Bachelor of Science
Document Type:
Thesis
Thesis Supervisors:
Kenneth Steven Brentner, Thesis Supervisor
Kenneth Steven Brentner, Thesis Honors Advisor
Puneet Singla, Faculty Reader
Keywords:
eVTOL
Acoustics
Broadband Noise
OASPL
Rotors
Design
Aerospace Engineering
Tip-Mach Number
Number of Blades
Hub Radius
Abstract:
The integration of Electric Vertical Take-Off and Landing (eVTOL) vehicles into urban air mobility systems presents a significant challenge due to noise pollution, which affects both public acceptance and regulatory compliance. This study aims to characterize the broadband noise generated by rotors used in eVTOL applications, focusing on the effects of three key parameters: tip-Mach number, blade count, and hub radius. Using a combination of computational tools, including XROTOR for rotor designs, CHARM for aerodynamic analysis, and PSU-WOPWOP for noise predictions, rotor configurations with four, five, and six blades were analyzed at tip-Mach numbers of 0.2, 0.4, and 0.6. Additionally, hub radii of 0.0447, 0.1447, and 0.2447 meters were evaluated to assess their influence on noise generation. The results indicate that increasing the tip-Mach number with the same number of blades leads to a substantial rise in overall sound pressure level (OASPL) and broadband noise, with noise levels increasing by up to 22 dB directly underneath the rotor as the tip-Mach number rose from 0.2 to 0.6. The effect of increasing blade count on noise generation was found to reduce the OASPL and broadband noise. At 0.2 and 0.4 tip-Mach numbers, noise generated from the rotors showed a 6 dB decrease as the number of blades increased from 4 to 6 blades. However, at a higher tip-Mach number of 0.6, increasing the blade count contributed to higher noise levels, showing a rise of 3 dB under the rotor in OASPL and broadband noise. An analysis of possibilities for this trend suggested an error in trimming the rotor at 0.6 tip-Mach number. Thus, further research into the effect of increasing blade count at higher tip-Mach numbers in the future may lead to a more definitive picture of the overall trend. These findings provide valuable insights for optimizing rotor design in future eVTOL applications, emphasizing the importance of carefully selecting tip speeds and blade configurations to achieve lower noise emissions. By refining rotor parameters to minimize broadband noise while maintaining performance requirements, this research contributes to the development of quieter eVTOL vehicles that can be integrated more seamlessly into urban environments in the near future.