An aerodynamic design method of propeller airfoils with geometric compatibility as constraints

The Mach number and Reynolds number vary widely from root to tip for a propeller blade, resulting complex flow at low-speed, subsonic and even transonic. Low-speed airfoils are used for inboard and high-speed airfoils are used for outboard, leading to a great challenge to ensure the aerodynamic compatibility and geometric compatibility of the airfoils under different design conditions. In this paper, some constraints, such as the locations of maximum thickness, coordinates of airfoils with adjacent thickness, and second-order derivative distribution of airfoil shape, are applied in the design optimization of propeller airfoil family, to achieve good geometric compatibility among airfoils. Reynolds-average Navier-Stokes (RANS) solver coupled with transition model and the efficient optimizer “SurroOpt” are used to perform the optimization. The results show that the optimized airfoils with second-order derivative as constraints behave the best geometric compatibility, and the lift-to-drag ratio at the design condition is also improved significantly, which demonstrates that the proposed method is effective in the design of airfoil family for propeller.