Aerodynamic performance and efficiency enhancement of a Savonius vertical axis wind turbine with Semi-Directional Curved Guide Vane, using CFD and optimization method

Savonius vertical axis wind turbines, as a type of drag-based power generator turbomachine, have long been characterized by low-efficiency challenges. One of the primary reasons for this is the positive pressure gradient on the convex portion of the returning bucket. To improve the aerodynamic performance of the rotor and enhance its efficiency, the present study proposes the use of a Semi-Directional Curved Guide Vane (SDCGV), an external device that is placed on the suction side of the rotor. This device effectively injects flow and controls positive pressure gradient accumulation, reducing unfavorable drag on the convex part of the returning bucket. The CFD study revealed that installing SDCGV can improve rotor efficiency by 230–350%. Also, the factorial optimization method, which is the most efficient approach compared to others, demonstrated that the implementation of a Savonius VAWT with SDCGV containing 7 vanes at a longitudinal distance of 250 (mm) and a lateral distance of 310 (mm) had a noteworthy effect on the turbine power coefficient ( \({C}_{\text{p}}\) $C_{\text{p}}$ ). The \({C}_{\text{p}}\) $C_{\text{p}}$ of the Savonius turbine attained a value of 0.14, which is deemed an adequate and elevated value for this type of VAWT. Moreover, the installation of SDCGV successfully broadened the operating range of the rotor to a tip speed ratio of 0.8.