Experimental investigation on the characterization of self-starting capability of a 3-bladed Savonius hydrokinetic turbine using deflector plates

Abstract

The use of deflectors as augmentation devices to improve the power performance of a 3-bladed conventional Savonius turbine has been investigated by analyzing the deflectors’ effects on self-starting capability and power performance at various deflector angles. Two deflector plates positioned at the upstream of the turbine were tested inside a closed-circuit wind tunnel at an air flow speed of 7.0 m/s (equivalent to 0.4 m/s water flow speed). The self-starting capability of the turbine was characterized in terms of the coefficient of static torque, CTS at various advancing blade deflector angles and returning blade deflector angles of δA= 15°, 30°, 45°, 60° and 75°and δR= 30°, 60°, 90°, respectively. It was found that the CTS profiles were generally higher than without any deflector. The increment of δR showed that it had a significant effect on the CTS profile due to the reduction of drag force on the returning blade as compared to the variation of δA. The study highlighted that the CTS profiles shifted away from the no-self-start conditions (CTS< 0) with the presence of deflectors. The experimental results also revealed that the coefficient of power, CP significantly improved for the case with the deflectors, particularly at δR=90°. The highest CP of 0.183 was achieved at δA= 75° and δR= 90°, which was also the optimal deflector configuration for the best self-starting characteristics. Thus, deflector augmentation may be a practical solution to improve the power performance and self-starting capability of the Savonius turbine in hydrokinetic applications, particularly at the low speeds of narrow and shallower rivers commonly found in rural areas.