Abstract:
Based on mechanism analyses on aeroacoustic characteristics of iced rotors, a new icing detection method is proposed, and a corresponding numerical method for calculating aeroacoustic characteristics of iced rotors is developed. Firstly, the CFD simulation method for 3-D flowfield around the blade is established by solving the unsteady RANS equations. Using the Eulerian approach, the conservation equations of mass and momentum are solved to obtain the droplet flowfield properties. Then, combined with the characters of rotor blade motion, a 3-D icing model considering influences of centrifugal force, the movement of water film and azimuthal angle variations is put forward. On this basis, the acoustic characteristics of iced rotor are calculated by the Ffowcs Williams-Hawkings equations with penetrable data surface in time domain, and the sensitivity of the acoustic characteristics to the ice accretion on rotor is analyzed. The calculated results are validated through the ice amount comparisons with experimental results of SRB rotor model and the sound pressure comparisons with experimental results of AH-1G/OLS model rotor in forward flight. Additionally, the influences of ice parameters on aeroacoustic characteristics of rotor are calculated, such as the ice accretion time and the icing position on blade. At last, some monitor locations compromising between sensitivity and enablement are found, and some new conclusions are obtained. The tiny ice amount on rotor can make the aeroacoustic characteristics change a lot, for instance, the ice with only 1.2% of blade volume makes the sound pressure decrease by 15% at the 255° azimuthal angle. The icing position can be identified through the variations of sound pressure at different monitor points.