Wind Forces on Rotating Small Wind Turbine Blade Tip using Wind Tunnel Measurements

Abstract

The wind tunnel tests performed on a small wind turbine with a rotor diameter of 340 mm and four different winglet configurations were analyzed. In this study, wind forces on small wind turbine blade tips were calculated using low speed wind tunnel. The five rotor models were fabricated to measure the force coefficients at tips using different winglet configuration. The sectional tangential force coefficients at r/R = 0.85 to 0.95 for all rotor models for various wind speeds of 5 m/s to 11.7 m/s were calculated. The maximum Ct value 0.4 and Cn value 0.8 were observed at 10 m/s. The wind speed beyond 10 m/s tangential force drastically decreases owing to stall occurrence at blade tip. The increase in wind velocity increases the normal and tangential forces for all winglets. The sectional forces increase as winglet height increases and radius of curvature decreases. The W2 winglet force coefficients Cn, Ct values were slightly more when compared to other winglet configurations. It is evident that, rotor model (W2) diffuses more vortex and reduces stall effects at blade tip when compared to other rotor models. Winglet on wind turbine blades increases the normal and tangential forces at blade tip; it leads to increase in structural forces on the blade.