Enhancing hydrodynamic efficiency of Savonius hydrokinetic turbine through circular deflector flow augmentation

Abstract

ABSTRACT The present numerical study employs a passive flow control augmentation mechanism to enhance the hydrodynamic performance of the Savonius hydrokinetic turbine. Two cylindrical deflectors guide the flow over the Savonius rotor blades. The effectiveness of placing the deflectors is examined by positioning them upstream of the returning and advancing blades. The Savonius hydrokinetic rotor’s efficiency is improved by incorporating Deflector1 to decrease the counteracting torque from the returning blade and Deflector2 to magnify the positive torque produced by the advancing blade. The study focuses on finding a suitable position ( L 1 ) and size ( d 1 ) of Deflector1 while keeping the size ( d 2 ) and position ( L 2 and ⍺) of Deflector2 fixed. The diameter of Deflector1 ( d 1 ) changes as d 1 / d =0 .15, 0.20, 0.25, 0.30, and 0.35 for each position, L 1 / d of 1.35, 1.65, 1.95, and 2.25. The study reports that the augmented Savonius turbine operates most efficiently at d 1 / d =0 .15, L 1 / d = 1.65, corresponding to a tip speed ratio of 0.9. The deflector-assisted Savonius hydrokinetic turbine enhances the power coefficient (C P ) by 54.1% in comparison to the ordinary Savonius rotor lacking deflectors. Further, utilizing cylindrical deflectors upstream of the Savonius hydrokinetic rotor improves the operating TSR range of the Savonius hydrokinetic turbine.