Numerical Analysis of Double Stack Blade Savonius Wind Turbine with Secondary Blades

Abstract

In this work, the performance of the Savonius vertical axis wind turbine with secondary blades was investigated numerically. The impacts of two geometric parameters of the secondary blades, including the height of secondary blades (h) and the distance between the main and the secondary blades (b) on the output torque were analyzed. Numerical simulations were performed by a commercial CFD code, ANSYS FLUENT 18.2. Numerical results show that employing secondary blades has a constructive impact on the output torque compared to the case without secondary blades. Moreover, the studied geometric parameters of the secondary blades have a significant impoact on the performance of the proposed turbine. It can be seen that by increasing the height of secondary blades, the angular position of the maximum torque is shifted. At b = 2.5 mm, the difference between the models is more comparable. Models h = 6 and 12 mm have the highest output torque, although with a slight difference between them. Model h = 12 mm has the highest output torque. At b = 7.5 mm, the difference between the models is more comparable than b = 2.5 mm. Model h = 12 mm has the highest output torque and models h = 3 and 6 mm are in the next levels. Obtained results in the second section demonstrate that by growing the distance between the secondary and the main blades, in the case of h = 3 mm, the produced torque declines. Furthermore, by increasing the distance between the secondary and the main blades from b = 0 mm to b = 2.5 mm and b = 7.5 mm, the amount of torque produced decreases by 17.33 and 26.66%, respectively. Moreover, by augmenting the distance between the secondary and main blades from b = 2.5 mm to b = 7.5 mm (200% growth), the produced torque decreases by 11.3%.