Performance study on a modified hybrid wind turbine with twisted Savonius blades

The present paper introduces a numerical investigation of a proposed hybrid vertical axis wind rotor performance. This proposed hybrid wind rotor has twisted Savonius blades with a modified blade profile combined with 2/3 Darrieus blades. The numerical simulations are aimed to explore the effects of the blade's attachment angle, radius ratio, and number of blades. The utilized Darrieus blades are straight, with an NACA0021 airfoil profile. It is clear from the hybrid rotors results obtained at a low radius ratio of beta = 0.27 that, the optimum attachment angle is phi = 30 degrees. Furthermore, there is a noticeable enhancement in the starting ability, especially through orientations where the standalone Darrieus rotor has degraded static torque. Different radius ratios, 0.25 to 0.5, are trained at the optimum attachment angle of 30 degrees, for both 2 and 3 bladed hybrid rotors. It is found that the influence of the radius ratio variation on the performance of the tested hybrid rotors is more significant than that of the attachment angle and the optimum radius ratio is found to be beta = 0.43. Adjusting both the radius ratio and attachment angle shows the best performance of the proposed hybrid rotor at beta = 0.43 and phi = 30 degrees, with a peak performance of Cp-max = 0.49.