Design and numerical investigation of Savonius wind turbine with discharge flow directing capability

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. For this purpose, a modeling procedure is defined and validated using available experimental results in literature. In addition, 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. Also, wind turbine with variable cut plane has a 12% decrease in power coefficient and 5% increase in discharge flow rate compared to simple Savonius wind turbine. Therefore, it can be inferred that twisted wind turbine with conical shaft indicated a proper aerodynamic performance.