An innovative deflector system for drag-type Savonius turbine using a rotating cylinder for performance improvement

The present study mainly focused on a new design of deflector by utilizing a rotating cylinder to augment the overall performance of the drag-type Savonius turbine since the negative torque generated by the returning blade is the primary cause of its poor efficiency. This has never been studied previously. The influence of distance, angular velocity, and cylinder deflector diameter on torque and power coefficients, as well as the wake zone on Savonius rotor performance, were numerically evaluated using the Computational Fluid Dynamics (CFD) method. The performance of the Savonius rotor was improved the most via the rotating cylinder deflector for almost all Tip Speed Ratios (TSRs). At a high angular velocity (ω = 40 rad/s), it performed better at redirecting incoming wind flow with high-velocity magnitude toward the concave surface of the advancing blade to increase positive pressure while reducing pressure on the convex side of the returning blade. On the other hand, at low angular velocity (ω = 3 rad/s) it required less energy to rotate in terms of energy consumption with a net torque up to 14% improvement compared to without the deflector case. Overall, there is a huge efficiency gain using the rotating cylinder deflector for all TSR ranges with about 50% more than the stationary deflector improvement at TSR = 0.6.