Separation Method And Experimental Verification Of Helicopter Rotor Noise Source

Rotor noise of helicopter is one of the research hotspot of helicopter technology.In order to identify the acoustic noise characteristics of rotor in the complex flowfield of rotor,the verification of different types of noise separation methods of rotor based on measurement methods and data is proposed.In Chapter 1,the research purpose,significance of this paper and the research status are introduced,Then the numerical research on helicopter rotor noise and the new progress of the test are summarized.Finally,the main research work of this paper is introduced.In Chapter 2,a new kind of vortex generator is designed,and after the simulation the PIV test is conducted and the intensity and radius of the vortex are measured.Based on this,the PIV flow field test is carried out.The vortex intensity and core radius at different wind speeds are obtained,and the calculated results agree well with the CFD analysis results.This provides technical supports for the following blade/vortex interaction noise test.In Chapter 3,the test methods for different types of rotor noise in hover are established.Firstly,the noise of symmetric NACA0015 airfoil of model rotor is measured without lift and torque,and the noise is the reference value of thickness noise.The collective angle is then added to the rotor to measure the thickness noise and load noise of rotor.Then with the designed vortex generator interfering with the model rotor,the noise of thickness noise and blade vortex interaction(BVI)noise is measured in different collective angles and Mach number of blade-tip of rotor,and it is a comprehensive measurement of thickness noise,load noise and BVI noise.Subsequently,under the different collective angles and the Mach number of the tip,the comprehensive experimental measurements of thickness noise,load noise and BVI noise are carried out,and the spatial radiation direction of different types of noise and the parameters that affect acoustic noise are obtained.In Chapter 4,the test method of high-speed impulse noise in hover is established.Firstly,based on the two-dimensional Euler equation,the NACA0015 airfoil resistance divergence Mach number is calculated.Then,according to the calculation results,the test equipment of noise test are replaced,and the Mach number of the tip is gradually increased to 0.894.The sound pressure value of the high-speed impulse noise is measured and time/frequency analysis are conducted.The results of test indicate that the method for the separation and identification of rotor acoustic noise can obtain the thickness noise,load noise and BVI noise,BVI noise can be simulated effectively with the new designed vortex generator and model rotor,it provides a new method for the research and measurement of BVI noise,and abundant experimental data is provided for the research and identification of parameters that influenced the helicopter rotor noise characteristics.