Computational fluid dynamics (CFD) study on the effect of the number of blades on the performance of double-stage savonius rotor

Abstract

Wind energy is known as renewable energy with the properties of the free, abundant and readily available source of energy. Wind power has now been seen as an alternative way to generate electricity. However, the existing wind turbines to harness this energy, which is used to transform wind kinetic energy into electricity still suffer low conversion capabilities. This study is therefore set out to evaluate the performance of a double-stage Savonius-type rotor while aiming to examine the effectiveness of this technique in increasing the efficiency while overcoming the inherent low inefficiency of the Savonius rotor. The simulations involved the use of the K-omega SST as the turbulent viscosity model. Three simulation models based on a different number of blades on the double-stage model are tested in terms of torque, power, torque coefficient and power coefficient. It is concluded that the double-stage technique was capable of enhancing the performance of the Savonius rotor. It was observed that more blades on a double-stage rotor have a negative effect on the performance of the Savonius rotor in terms of both torque efficiency and power efficiency. Comparing the three models, it was found that the two-blade model of the double-stage produced more torque and power output compared to the other three-blade and four-blade models of the double-stage Savonius rotor. Furthermore, the highest conversion efficiency in terms of power among all models occurs at the TSR of 0.6 with a corresponding maximum power coefficient of 18.4%.