Large thickness airfoils with high lift in the operating range of angle of attack

Abstract

This paper presents the design, prediction and evaluation of a family of large thickness airfoils with blunt trailing edges. The family includes four airfoils, whose relative thickness ranges from 45% to 60% and relative thickness of trailing edge ranges from 7% to 16%. These airfoils are designed by the RFOIL solver at different design Reynolds numbers of 4.0 × 106, 3.5 × 106, 3.0 × 106, and 2.5 × 106 with increasing thickness. The design Reynolds numbers are calculated by the operating characteristics of a 5 MW wind turbine. The design objectives focus on the aerodynamic performance in operating ranges of angle of attack at blade root, differing from those of the aviation airfoils and traditional wind turbine airfoils. And the main design constraint is the stability of the lift coefficients in range of large angles of attack with the variation of Reynolds number. The predictions by RFOIL show that, in the range of angle of attack (15°–30°), the values of lift coefficient of the four new airfoils are largely in the range of (1.0–1.7) and stable with the variation of Reynolds number. These features help obtain more efficient and stable output. The evaluation results indicate that the overall performance of new airfoils is acceptable for the design of multi-MW rotor blades.