The Potential of Collective Pitch Actuation Using Shape Memory Alloys for Aeroacoustic Benefit in Coplanar Rotors
Open Access
- Author:
- Hafner, Aaron
- Area of Honors:
- Aerospace Engineering
- Degree:
- Bachelor of Science
- Document Type:
- Thesis
- Thesis Supervisors:
- Jose Palacios, Thesis Supervisor
Xin Ning, Thesis Honors Advisor - Keywords:
- Acoustics
Aeroacoustics
VTOL
rotor
rotor blade
experiment
experimental
OASPL
PSD
Vold-Kalman Filter
Tonal
Broadband - Abstract:
- Rotor noise represents an obstacle towards public acceptance of VTOL technology which must be overcome. In this thesis, blade pitch actuation is experimentally investigated as a means of reducing noise and improving aerodynamic performance. Experimental data for co-planar rotor blades in hover is collected from the Penn State Coaxial Acoustics Test System. Blade pitches representative of conditions before and after pitch actuation are tested in an experimental parametric study varying blade number, blade pitch, and RPM. The effects of multiple blade pitches and RPM on the rotor's aerodynamic performance and acoustics are quantified, in the 4-bladed and 2-bladed configurations. Initial results from the experiment indicate that the combination of highest blade pitch (below stall) and lowest RPM is both aerodynamically and acoustically preferable over other combinations of blade pitch and RPM which produce the same thrust. The test at 15.0 degrees blade pitch experiences a 16.9% increase in power loading and a and a 13.4% increase in figure of merit, compared to the matching-thrust test at 9.0 degrees blade pitch. The test at 15.0 degrees blade pitch also produces an OASPL 4.3 dB and 3.6 dBA lower than the OASPL produced by the matching-thrust test at 9.0 degrees blade pitch. It is also shown that pitch actuation from 9.0 degrees to 15.0 degrees changes the steady-state broadband noise generated by a 4-bladed co-planar rotor by less than 1 dB. These results indicate that the implementation of blade pitch actuation has the potential to provide performance and acoustic benefits to coplanar rotors. Pitch actuation using shape memory alloys is suggested.