Abstract:
A new numerical method for predicting ice accretion on helicopter rotor is established. The ice amount is calculated using a coupling method of 3-D CFD and 3-D icing model. Firstly, the orthogonal and body-fitted grids are generated around rotor blade by interpolating and folding approach of section airfoil grid. Then, the CFD simulation method for 3-D flowfield around the blade is established by solving the unsteady RANS equations with Spalart-Allmaras turbulence model. Based on the Eulerian approach, the conservation equations of mass and momentum are solved to obtain the droplet flowfield properties on the same grid used in CFD simulations, and the multistage Runge-Kutta scheme is employed in the temporal discretization. Followed that, combined with the characters of rotor blade motion, a 3-D icing model considering the influences of the centrifugal force, the movement of water film and the variation of the azimuthal angle is put forward. The comparisons between the calculated results and experimental data about the ice accretion on rotor in hover and in forward flight indicate that the present method is effective. At last, the effects of the atmospheric temperature on the icing process and the aerodynamic performance of the iced rotor are analyzed. At the warmer sub-freezing temperatures, ice is not easy to form near the blade tip, and blade sectional lift along the spanwise direction from 45% to 65%R is decreased obviously. There is a significant deterioration in the rotor required power and the lift coefficient with temperature dropping, resulting in the decrease of the Figure of Merit of rotor in hover (FM is reduced by about 7.1% at the temperature of -28°C).