Numerical investigation of performance and flow patterns of a modified Savonius hydraulic rotor

The Savonius hydraulic turbine is effective in harnessing the energy carried by flowing water. The advantages of the Savonius hydraulic turbine, such as simple in structure and good start-up characteristics, have been acknowledged. Nevertheless, the lack of a detailed investigation of the flows around the Savonius hydraulic rotor hampers the technical advancement of the Savonius hydraulic turbine. Here, a modified Savonius hydraulic rotor based on conventional Savonius rotors was designed to investigate the performance and flow characteristics of the Savonius hydraulic rotor. Computational fluid dynamics techniques were used. The influence of the rotor blade geometry and the tip speed ratio was considered. The results indicate that the ratio of the length of the straight edge to the radius of the circular arc of the blade has an important impact on the performance of the Savonius hydraulic rotor. The maximum power coefficient of the rotor with such a ratio of 0.81 is 58% higher than the rotor with the ratio of 0.46. The tip speed ratio corresponding to the maximum power coefficient is related to the ratio. Comparative analysis of the velocity and pressure distributions for different rotor setting angles was conducted to describe the interaction between the flow medium and the rotor. The torque coefficient of the rotor depends considerably on the area and position of high upstream pressure; meanwhile, downstream vortices impose a negative effect on the rotation of the rotor. The results provide a sound support for the optimal design of the Savonius hydraulic turbine. (paper)