A higher harmonic control (HHC) investigation was conducted on a fuII-scale, isolated XV-15 rotor in helicopter mode in the NASA Ames 80- by 120-Foot Wind Tunnel to independently control noise and vibration. The higher harmonic blade pitch was generated using swashplate oscillations. The radiated blade-vortex interaction (BVI) noise footprint was measured on a plane beneath the rotor with an acoustic traverse. Test results showed that HHC is highly effective in reducing BVI noise, achieving a 12 dB reduction in peak noise level within the noise footprint. Noise reduction with HHC remains effective even with perturbations in rotor trim and flight conditions. Blade pressure feedback was demonstrated to be a viable method for closed-Ioop noise control. Some noise reduction was achieved with no increase in vibratory hub Ioads. Increases in control loads due to HHC generally limited further noise reduction. The vibration controller achieved about 50 percent reduction in vibratory hub loads with control loads Iimiting the HHC amplitude.
Full-scale demonstration of higher harmonic control for noise and vibration reduction of the XV-15 rotor
Demonstration der höheren harmonischen Lärm- und Schwingungsdämpfung am vollmaßstäblichen Modell des XV-15-Hubschrauberrotors
Journal of the American Helicopter Society ; 46 , 3 ; 182-191
2001
10 Seiten, 15 Bilder, 2 Tabellen, 23 Quellen
Article (Journal)
English
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