Theoretical And Experimental Investigation Of Helicopter Tail Rotor Noise

With wide applications of helicopters, helicopter noise level has become one of substantial indexes of helicopter performance and acceptability. Helicopter tail rotor is a major source of the noise; therefore investigation of tail rotor noise characteristics becomes very valuable and important to control the helicopter noise level.This article focuses on researching the helicopter tail rotor noise and analyzing its mechanism to establish the computation model of the isolated tail rotor noise. The three-dimensional unsteady panel method is adopted to calculate the pressure on the surface of the blades and the Farassat la formula is used to simulate the numerical value of the isolated tail rotor noise property. A set of test system has been established, through the experiment of the isolated tail rotor noise, the tail rotor and the vortex interference which are carried out in the anechoic chamber, Test parameters include rotor speed, number of blades, blade pitch angle, vortex interference angle and tail rotor blade azimuth arrangement. The result shows that the noise is markedly increased when the tail blades interacted with the vortex, the noise level under the orthogonal interference is highest.Besides, the scissors-type arrangement of tail rotor can change the noise spectrum and lower the noise level. Last, by contrastive analysis between the results of the isolated tail rotor noise and the experiment, the computation model is being proven. These conclusions can be used to estimate the helicopter tail rotor noise and help to guide tail rotor noise reduction design.