Experimental study on aerodynamic noise characteristics of helicopter ducted tail rotor

Using the FL–52 aero-acoustic wind tunnel test system of the Aerodynamics Research Institute, the experimental study on the ducted tail rotor noise characteristics is carried out. The influence of the jet shear layer on the test data is corrected, and the noise spectrum and far-field directivity of the culvert tail rotor in hover and forward flight are obtained. The variation laws of the noise with the Mach number of the tail rotor tip are analyzed, and the results show that the aerodynamic noise of the ducted tail rotor conforms to the load noise characteristics. The effects of the blade distribution along the hub on the spectral characteristics of the aerodynamic noise are compared. The shielding noise reduction effect of the duct on the noise propagation under typical working conditions is obtained in hover, the noise in the rotating plane is 2 dB lower than that in other positions in forward flight, the noise reduction in the rotating plane is 5 – 8 dB.