Experimental and numerical investigations on the aerodynamic performance of a pivoted Savonius wind turbine

Savonius turbines have been the subject of various wind energy projects due to their good starting characteristics, easy installation, and independency of wind direction. However, the Savonius rotor suffers from low aerodynamic performance, which is mainly due to the adverse torque of the returning blade. A recently introduced design suggests using pivoted blades for the rotor to eliminate the negative torque of the returning blade. In this study, the aerodynamic performance of the newly proposed turbine has been investigated experimentally and numerically. The experimental measurements are performed in a subsonic open-jet type wind tunnel facility. The numerical simulations are performed using ANSYS-Fluent commercial software, by making use of the multiple reference frame model. The effects of the number of blades (3-, 4-, and 6-bladed) on the torque and power coefficients are examined in details, at several Reynolds numbers. Results show that the new rotor has no negative torque in one complete revolution and that the 3-bladed rotor has the best aerodynamic performance, in a manner that, it reaches a maximum power coefficient of 0.21 at TSR = 0.5. Although increasing the number of blades decreases the output torque oscillations, it also decreases the average power coefficient of the rotor. Results show that Reynolds number does not have a significant effect on the average power coefficient of the rotor in the studied range of 7.7 × 10⁴≤ Re ≤ 1.2 × 10⁵.