Investigation of different deflector geometry and mechanism effect on the performance of an in-pipe hydro Savonius turbine

Generation of clean power is one of the primary concerns of the world's engineering community today. The use of renewable and clean energy harvesting methods, especially on a small scale, has gained increasing importance in recent years. Due to abundant distribution, uncomplicated manufacturing, and low cost, small-scale hydrokinetic sources could be an interesting choice for clean energy harvesting. For instance, existing excessive pressure in water transmission systems could be counted as a small-scale hydrokinetic energy source. One beneficial method for extracting this excessive energy from piping systems is utilizing in-pipe drag-based turbines with a vertical axis. Despite recent studies determining the optimal design point for these turbines, variable flow rates within the pipeline are one of the problems that affect their operation, causing deviations from the optimal point. In this study, the main focus is on improving the turbine performance in off-design conditions by use of deflectors, which are generally used to direct the flow toward the blades of a turbine in an appropriate direction. For these reasons, the effects of five different types of deflector geometry on the efficiency of an in-pipe Savonius turbine have been numerically investigated for varying flow rates. Among the studied deflectors, one featuring a moving guide vane, that can dynamically adjust its position at various flow rates has proved to have considerably better performance at flow rates that are different from the optimal design point. In addition, a new systematic outline procedure for designing this type of deflector in a limited space of small-scale pipe has been proposed. The accuracy of the numerical simulations is validated by the experimental results of the provided test rig.