Performance improvement of horizontal axis wind turbines using curved gurney flap: 3D numerical investigation

Abstract

The impact of curved Gurney flaps on the performance of a 660 kW V47 horizontal axis wind turbine (HAWT) is analyzed in this study. The trailing edge of the turbine blades is passively modified by curved flaps. The continuity and momentum equations are solved using a Reynolds-averaged Navier-Stokes solver and Shear-Stress-Transport turbulent model. The effect of the direction and radius of curved flaps on the aerodynamic performance of the wind turbine (torque and power generation, flow separation, and thrust loads) is examined. The study examines how the curved flap’s performance on HAWT is affected by the blade pitch angle ( $\theta$ ) and wind speed ( $V$ ). According to the results, curve flaps have a positive impact on the output torque at lower pitch angles ( $\theta \le 9°$ ). The average torque increase for $\theta =2°$ and $5°$ is 3.7% for curve flaps, while it is only 2.9% for flat flaps. This conclusion is not valid for higher pitch angles ( $\theta \ge 11°$ ) where the flap disrupts the aerodynamic performance. Further, the use of curve flaps with the radius of $R_f=2h$ (inward-type) can improve the torque produced (up to $9.6\%$ ) compared to other curved flaps and even flat flaps, especially around the nominal operating point. This conclusion is valid for $\theta \le 9°$ , while for higher pitch angles, the flat Gurney flap has better performance generally.