Experimental study of wind turbine blade power augmentation using airfoil flaps, including the Gurney flap

Abstract

The purpose of this paper is to present the feasibility experiment study of the power and efficiency augmentation of the horizontal axis wind turbine system by adding small flaps to its blades. The experiment of lift enhancement of a two-dimensional airfoil with a small trailing edge flap is conducted in a low-speed, closed-loop wind tunnel at Shantou University. NACA632-215 is selected as the tested airfoil and the Reynolds number is 2.4xIO5, based on airfoil chord. In experiments the angles of attack varied from 0 to 40 and the heights of the flaps are 1.0%, 1.5%, 2.0% and 2.5% of the airfoil chord. The effects of different deflection angles (0°, 45°, 90°, 135°) of the trailing edge flap are compared. The lift and drag coefficients are determined from the surface pressure distributions, which were measured for all tested conditions. The results indicate that all tested flaps could increase the lift coefficient and the larger flaps produce successively larger increments, although not proportionally. The Gurney flap shows a superior performance compared with other angles trailing edge flaps.