The effects of deflector longitudinal position and height on the power performance of a conventional Savonius turbine

The limited electrical power inherent in rural and remote areas with a narrow width river can be addressed with the utilization of a Savonius hydrokinetic turbine (HKT) that generates electricity from a renewable hydro resource. However, despite its simple design, Savonius HKT practicality is hindered by low power performance. One solution to overcome this issue is to use an augmentation device such as a deflector to improve the performance. However, the effects of deflector geometric parameters on the power performance of such turbine have not been comprehensively studied and information about the flow physics around the turbine with the presence of a deflector are still lacking in literature. Therefore, the present study aims to improve the power performance by varying the advancing blade and the returning blade deflector longitudinal position ratios, ranging from 0.000 to –0.500 and –1.204 to –1.704, respectively, followed by varying the deflector height at 0.5Η, 1Η and 1.5Η of the turbine's height. Quantitative study has shown that all variations of deflector positions resulted in power performance improvements of more than 30% whereas a reduction by 7.69% was observed for the case with 0.5Η deflector. It was found that the optimal deflector longitudinal position ratios were at –0.500 for the advancing blade deflector and –1.204 for the returning blade deflector, whereas the optimal height of deflector was 1Η. The qualitative study revealed that the deflector at optimal deflector longitudinal position and height prevented the separated flow from entering the low pressure region between the deflector and the turbine’s blade, reducing unfavorable negative torque on the turbine. Consequently, the turbine exhibited the highest coefficient of power of 0.26 with a significant improvement of 100% relative to without the deflectors.