MODEL DUCTED PROPULSOR NOISE CHARACTERISTICS AT TAKEOFF CONDITIONS

A model Advanced Ducted Propulsor (ADP) was tested in the NASA Lewis L ow-Speed Anechoic Wind Tunnel at a simulated takeoff velocity of Mach 0.2. The model was designed and manufactured by Pratt & Whitney. The 1 6-blade rotor ADP was tested with 22- and 40-vane stators to achieve c ut-on and cut-off criterion with respect to propagation of the fundame ntal rotor-stator interaction tone. Additional test parameters include d three inlet lengths, three nozzle sizes, two spinner configurations, and two rotor rub strip configurations. The model was tested over a r ange of rotor blade setting angles and inlet angles of attack. Acousti c data were taken with a sideline translating microphone probe and wit h a unique inlet microphone probe that identified inlet rotating acous tic modes. The beneficial acoustic effects of cut-off were clearly dem onstrated. A 10-dB fundamental tone reduction was associated with the long inlet and 40-vane stator. The fundamental tone level was essentia lly unaffected by inlet angle of attack at rotor speeds of above 96% d esign.