Experimental investigation on aerodynamic performance of helical savonius rotor

In order to decrease the large fluctuation in the static torque of the conventional Savonius rotor, a helical Savonius rotor with a twist of 180° is proposed. The aerodynamic performance of the rotor is investigated in the low-speed wind tunnel. The rotation diameter, height and eccentric of the rotor are 420 mm, 680 mm and 100 mm, respectively. The static torque at different azimuth angles is tested at a velocity of 5 m/s, the rotation speed and torque at different loads are recorded at a velocity of 10 m/s. Through the analysis of experiment data, the rotor could always provide positive coefficient of the torque, though the blade loss causes the static torque not being constant with the azimuth angle, the fluctuation in the static torque is relatively small. The rotation speed fluctuation decreases with the increase in the tip speed ratio, while the torque fluctuation increases with the increase in the tip speed ratio. The torque coefficient decreases nearly linear with the increase in the tip speed ratio, the power coefficient and the tip speed ratio are related in quadratic function and the power coefficient first increases, then decreases with the increase in the tip speed ratio. At a velocity of 10 m/s, maximum power coefficient of the rotor of 0.1125 occurs at the tip speed ratio of 0.47.