A model high-speed advanced counterrotation propeller, F7/A3, was tested in the NASA Lewis Research Center's 9- by 15-Foot Anechoic Wind Tunnel at simulated takeoff/approach conditions of 0.2 Mach number. Acoustic measurements were taken with an axially translating microphone probe, and with a 'polar' microphone probe which was fixed to the propeller nacelle and could take both sideline and circumferential acoustic surveys. Aerodynamic measurements were also made to establish propeller operating conditions. The propeller was run at two blade setting angels (front angle/rear angle) of 36.4/43.5 and 41.1/46.4 deg, forward rotor tip speeds from 165 to 259 m/sec (540 to 850 ft/sec), rotor spacings from 8.48 cm (3.34 in.) to 14.99 cm (5.90 in.) based on pitch change axis separation, and angles of attack to plus/minus 16 deg. The aft rotor diameter was 85 percent of the forward rotor diameter to reduce tip vortex-aft rotor interaction as a major interaction noise source. Results are compared with equal diameter F7/A7 data which was previously obtained under similar operating conditions. The aft rotor-alone tone was 7 dB lower for the reduced diameter aft rotor, due to reduced tip speed at constant rpm. Interaction tone levels for the F7/A3 propeller (compared to the F7/A7 propeller) were higher at minimum blade row spacing and lower at maximum spacing.
Noise of a model counterrotation propeller with reduced aft rotor diameter at simulated takeoff/approach conditions (F7/A3)
Geraeuschentwicklung eines Drehfluegelmodells mit entgegengesetzt drehendem rueckwaertigem Rotor unter simulierten Start- und Landebedingungen (F7/A3)
AIAA-Papers ; Jan ; 1-28
1988
28 Seiten, 19 Bilder, 3 Tabellen, 10 Quellen
Aufsatz (Konferenz)
Englisch