Mojtaba Tahani, - Faculty of new sciences and technologies, University of Tehran, Tehran, Iran
Alibakhsh Kasaeian, - Faculty of new sciences and technologies, University of Tehran, Tehran, Iran
Ali Rabbani, - Faculty of new sciences and technologies, University of Tehran, Tehran, Iran
Yeganeh Heydari - Faculty of electrical engineering, Shahid Beheshti University, Tehran, Iran

Recently, Savonius vertical axis wind turbines due to their capabilities and positive properties have gained a significant attention. The objective of this study is to design and model a Savonius-style vertical axis wind turbine with direct discharge flow capability in order to ventilate buildings. Two design modifications, variations in cross-section with respect to the height of rotor and conical shaft in the middle of wind rotor are proposed. The variable cut plane changes the pressure in inner region of rotor and enhances the discharge flow rate. However, this increases the negative torque acting on returning blade thus reducing the power coefficient. The inlet flow to Savonius wind rotor goes along the surface of conical shaft and is diverted to lower pressure in order to improve the discharge flow rate. Results indicate that the twist on Savonius wind rotor reduces the negative torque and improves its performance. According to the results, a twisted Savonius wind turbine with conical shaft is associated with 18% increase in power coefficient and 31% increase in discharge flowrate compared to simple Savonius wind turbine

Savonius turbine; Discharge flow; Conical shaft; Twist; Power coefficient