PERFORMANCE ANALYSIS OF WIND TURBINES WITH TIP VANES

Abstract

Performance enhancement of horizontal axis wind turbine (HAWT) with circular arc blade section (CABS) has been investigated both experimentally and computationally using upstream and downstream tip-vanes (winglet) configurations. A computational study is performed for a three-blade rotor of 0.5m diameter in ANSYS Fluent to identify the optimum values for cant angle and twist angle. Findings from the numerical analysis are then utilized as inputs for the experimental study. The height of the winglet is selected as 6% of the rotor radius while cant angle and twist angle are 55o and 0o, respectively. Power and thrust coefficient are measured for both the upstream and downstream winglet  orientations at different pitch angles ( ) and tip speed ratios (λ). Results show that thrust coefficient increases with the increase of tip speed ratio. There is an around 10.94% and 8.56% increment for upstream and downstream winglets, respectively, in terms of without winglets at design tip speed ratio (TSR=5) and zero pitch angle. Regarding power coefficient, the upstream winglet provides 9.79 % extra power in comparison with the reference model at design tip speed ratio and zero pitch angle. Improved performance is obtained with downstream winglet achieving almost 15% additional power at zero pitch angle. But with the increase of the pitch angles, power decreases as λ0.1. The reason for extracting more wind energy by downstream winglets can be explained from the pressure coefficient values. Near the leading edge, r/R=95%, of the blade, the pressure difference between suction and pressure surface is 15 for the downstream winglets, and 6 is in the case of without winglets.