To optimize the leading edge (LE) shape for improving airfoil aerodynamic performance

a polynomial based continuous-curvature LE design method was proposed. By specifying derivatives of camber-line and thickness distribution at the junction point

the continuous surface curvature was guaranteed. The length and the fullness of the LE portion could be specified according to design need. The method was used to optimize the LE portion of two subsonic airfoils with inlet Mach number of 075 and 060

respectively. Simulations indicated that the LE optimized airfoils had much lower suction spike strength

which decreased the gradient of adverse pressure caused by flow diffusion. Therefore

the LE separation bubble was suppressed and the premature transition of boundary-layer was avoided. Due to these two factors

the LE optimized airfoils had much lower loss level at off-design conditions and the useful operation range were increased by 31°and 38° compared with circular LE airfoil

respectively. The leading edge of a transonic compressor stage was also modified by this method

the increase of adiabatic efficiency for rotor and stage were 07 percent and 11 percent at near stall condition

respectively

with stall margin also extended.