Flow Dynamics and Performance Enhancement of Drag-Type Savonius Wind Turbine with a Novel Elliptic-Shaped Deflector

Abstract

The drag-type Savonius rotor, a type of vertical-axis wind turbine, is designed to capture wind energy and convert it into rotational torque. However, their efficiency is limited, which restricts their commercial viability. This inefficiency is primarily due to the negative torque produced by the returning blades, which results in minimal power output. This study examines the effect of the aspect ratio on a new elliptic-shaped deflector using three-dimensional (3D) computational fluid dynamics (CFD) modeling and an optimization approach. The aim of this novel deflector is to enhance the aerodynamic performance of the Savonius turbine by reducing negative torque during blade sweeping on the return side. Although there is extensive literature on elliptic-shaped bodies, there is a notable lack of research on the interaction between airflow over such a body used as a deflector and the Savonius rotor. This research uses an optimization methodology based on the design of experiments to determine the optimal design. Using the Taguchi method and analysis of variance, the number of blades is identified as the most significant factor, accounting for 77% of the rotor performance near the deflector. At a Tip Speed Ratio (λ) of 0.8, the optimal deflector achieves the highest average power coefficient of 0.34, representing a significant 42% improvement compared to the maximum average power coefficient without a deflector.