Optimal shape and position of a thick deflector plate in front of a hydraulic Savonius turbine

Abstract

This paper describes an optimization procedure for the shape and position of a thick deflector plate in front of a hydraulic Savonius turbine to improve the output power of the system for a constant frontal area. Seven geometrical parameters are taken into account during the optimization process. The simulation code Star-CCM+ is used to investigate the flow field around numerous structures to obtain the optimal configuration. This code is driven by OPAL++ (in-house code optimization). During the optimization procedure, maximizing the average power coefficient (Cp) is the main objective function. The optimal configuration improves the Cp by almost 11% for a tip speed ratio λ=1.1 in comparison with the traditional Savonius turbine. The hydrodynamic features of the turbine with the optimal deflector plate are discussed in detail and compared with the standard turbine, explaining that the increase in the turbine performance was obtained by an improved pressure distribution and enhanced flow configuration around the turbine blades. The performance of the turbine with optimal deflector plate is finally compared with the standard design for the whole operation range by varying the tip speed ratio. This comparison reveals that the power coefficient Cp is increased by nearly 15% for λ=1.2. Finally, it has been checked that the turbine with the deflector plate is still self-starting. The obtained design should not only be very useful to considerably improve the power of the turbine at a constant frontal area but also effective to protect the returning blade from collisions with suspended objects thanks to the deflector plate.