Design and flow analysis of a Savonius‐type hydro‐kinetic turbine with hybrid‐blade profile

This paper attempts to improve the performance of the Savonius hydrokinetic turbine by replacing its conventional blade with a hybrid blade profile associating curved segments from airfoils and a straight blade segment. Symmetric and unsymmetrical airfoil curve segments with innovative blade parameters—overlap (6.14%), flat edge gap (20%), flat offset (8.96%), and bend curvatures (5–15 mm) at the blade trailing edges have been designed. Using CFD, different combinations of the parameters and their fluidic behavior have been systematically studied with a specific airfoil curved segment to develop a Savonius‐type hybrid‐blade hydrokinetic turbine (HHT) for a low discharge channel. Results show that the unsymmetrical NACA 63415 curve segment at the turbine leading edge produces higher average hydrodynamic torque. Incorporating trailing edge bend curvatures (5, 10 and 15 mm) in the HHT ensures higher performance than any combinations of flat edge gap, offset and overlap. The highest torque coefficient and power of 0.93 and 0.61 W are obtained with a flow stream speed of 0.4 m/s for the best blade bend curvature of 10 mm. Well‐developed flow structures in the overlapped portion resulted from edge gap, and offset flow along with reduced recirculation zones on the suction surfaces and increased shear layers at the trailing edges of the blades due to bend curvatures are the contributors to the increased fluid dynamic performance of the present HHT.