Aerodynamic Design Optimization of Elliptical-Bladed Savonius-Style Wind Turbine by Numerical Simulations

Abstract

Savonius-style wind turbine (SSWT), a class of vertical-axis wind turbine, appears to be promising for off-shore applications because of its design simplicity, good starting ability, insensitivity to wind direction, relatively low operating speed, low cost and easy installation. Various blade shapes have been used over the years to improve the performance of this class of turbine. In the recent past, an elliptic-bladed profile with sectional cut angle of 50° has shown its potential to harness the wind energy more efficiently. The present study aims to optimize this profile by numerical simulations. In view of this, the elliptical-bladed profiles are tested at different sectional cut angles of θ = 45°, 47.5°, 50° and 55°. The shear stress transport (SST) k-ω turbulence model is used to simulate the flow field, and thereafter, the torque and power coefficients are obtained at the rotating conditions. From 2D simulation, pressure and velocity contours are generated and analyzed. 2D simulations are also carried out for a semi-circular bladed profile in order to have a direct comparison. The numerical study demonstrates an improved flow characteristics, and hence the power coefficient of the elliptical-bladed profile at = 47.5°. Finally, 3D simulation is carried out to visualize and analyze the flow field around the optimum elliptical-bladed rotor at a tip speed ratio of 0.8. The aspect ratio of the rotor for the 3D simulation is kept at 0.7.