Performance Enhancement of a Savonius Wind Turbine Using an Elliptical Cylinder Deflector

Savonius wind turbines, while robust and simple in design, suffer from inherently low efficiency primarily due to the negative torque generated on the returning blade. This study presents a parametric investigation of an elliptical-cylinder deflector as a passive flow control method for Savonius wind turbines. Using Computational Fluid Dynamics (CFD), a series of unsteady Reynolds-averaged Navier-Stokes (URANS) simulations were performed with the k–ω SST turbulence model to evaluate the aerodynamic effects of the deflector. The investigation focused on systematically analyzing the influence of deflector aspect ratio (AR) and axial rotation angle (α) on turbine aerodynamics and wake behavior. The results demonstrate that the elliptical deflector modifies the incoming flow field and reduces adverse pressure effects on the returning blade, leading to improved turbine performance relative to the baseline configuration. Among the investigated configurations, the case with AR = ۰.۵ and a ratio of ellipse vertical diameter to turbine diameter (b/D) of ۰.۷ yielded the highest power coefficient (CP) of ۰.۲۷۵ at a tip speed ratio (TSR) of ۰.۸۲, corresponding to an ۸% improvement compared to the turbine without a deflector. While the AR = ۰.۵ configuration produced the highest performance among the investigated cases, the circular deflector (AR = ۱) exhibited more stable behavior across a broader TSR range. Furthermore, the axial rotation angle of the deflector significantly affected the aerodynamic response, with the ۰° orientation producing the highest torque response among the investigated cases. Flow-field and pressure analyses confirmed that the deflector weakens the high-pressure region on the returning blade and alters the wake structure around the rotor.

کلیدواژه ها:

Savonius wind turbine ، Elliptical deflector ، Aspect-ratio ، Power coefficient