Performance enhancement of Savonius hydrokinetic turbines: the role of twisted blade profiles

Abstract

Savonius Hydrokinetic Turbines (SHTs) are widely recognized for their simplicity, cost-effectiveness, and adaptability to slow flow conditions. However, conventional SHT designs face limitations, including low efficiency and significant torque fluctuations. The adoption of twisted/helical blade profiles has emerged as a potential solution to enhance turbine performance by reducing torque fluctuations and improving power output. A review of the existing literature reveals that studies focusing on blade twist angles are limited. To address this, the present study systematically investigates the impact of a broader range of blade twist angles (15-90°) on SHT performance using computational fluid dynamics (CFD). Key performance metrics, including the torque coefficient (CT) and power coefficient (CP), were evaluated, and numerical accuracy was ensured through mesh independence and time step independence studies. The developed CFD model was validated against experimental results obtained from the literature to confirm the model's ability to capture flow dynamics. The results show that the SHT with a 45° blade twist achieves a maximum CP of 0.252, an increase of 3.81 % over the conventional design, and reduces torque fluctuations by 9.38 %. Meanwhile, the 60° blade twist demonstrates comparable CP values but achieves a further 7.28 % reduction in torque fluctuations compared to SHTs with a 45° blade twist.