Empirical modeling of urban air mobility rotor icing thrust degradation

An empirical model to predict airfoil lift coefficient degradation under icing conditions was developed.The model uses Blade Element Momentum Theory to predict the thrust lost due to a blade section with accreted ice. The model attempts to characterize the lift degradation of a section of the rotor, effectively converting the 3D rotor environment to a 2D problem. The 2D ice accretion was reached by removing all the ice from the blade but a strip of ice at a selected spanwise location. The model was developed using a 14-inch carbon fiber 2 bladed rotor. Accreted ice to the rotor was removed except at 75% of the rotor, spanning +/-1 inch. Baseline lift coefficients were determined empirically using experimental thrust value measured and baseline drag coefficients were acquired from NACA 0015 lookup tables. From 36 experimental cases, the model over-predicted rotor thrust by an average of 33%. Using the Han-Palacios Correlation for the iced drag coefficients, the model under-predicted rotor torque by an average of 37%. These errors were attributed to 3D effects due to the sectional ice left on the rotor being too large for the inherent 2D assumptions used. Smaller ice strips should be used to develop the empirical model and reduce uncertainty.