Acoustic and Performance Analysis of Counter-Rotating Co-Axial Toroidal Rotors
Open Access
- Author:
- Robertson, Noah
- Area of Honors:
- Aerospace Engineering
- Degree:
- Bachelor of Science
- Document Type:
- Thesis
- Thesis Supervisors:
- Jose Palacios, Thesis Supervisor
Kenneth Steven Brentner, Thesis Honors Advisor - Keywords:
- Aeroacoustics
Propellers
Performance
Toroidal - Abstract:
- With the rise of autonomous vertical flight and rapid development of urban air mobility rotorcraft in the private sector, noise levels generated by aerospace vehicles within densely populated areas has become a concern. For electric rotorcraft in particular, coaxial rotor systems represent a potentially beneficial vertical takeoff and landing configuration. Extensive prior experimentation has been done to explore how the variables in a coaxial system, such as separation distance, relative phase angle, and RPM, impact both acoustics and performance. The experimental work done in this research applies a novel rotor design, known as a toroidal propeller, to a coaxial, counter-rotating configuration. Toroidal propellers, developed in preliminary research by MIT and Sharrow Marine (for underwater usage), have demonstrated distinct acoustic properties, which has been further verified by amateur drone hobbyists. Much of this acoustic change has been attributed to toroidal propellers not producing, or producing much weaker, tip vortices. Applying this propeller concept to a coaxial system could introduce acoustic benefits and create an appealing solution for aerospace companies operating in urban environments. Experimental work was completed to compare the acoustics, performance, and power requirements between custom designed toroidal propellers and standard propellers at the Penn State Adverse Environment Rotor Test Stand (AERTS) Lab. Comparability was maintained by holding parameters, such as radius, airfoil selection, and rotor solidity, constant between the toroidal and standard designs. A comparison of the acoustic signatures was conducted, considering the overall sound pressure levels, tonal noise changes that could manifest due to the uneven spacing and nature of the toroidal blades, and broadband shifts that could be an effect of wake ingestion in the coaxial configuration. Thrust and torque data was collected to compare performance between each propeller in the coaxial configuration as well as the system as a whole. At matching thrust test cases, the toroidal propeller acoustics did not result in a lower overall sound pressure level.