Blade curvature as a key driver of conical-basin gravitational vortex turbine performance: experimental evidence

Abstract

This study investigates the role of runner blade curvature in enhancing the performance of Gravitational Water Vortex Turbines (GWVTs) for low-head hydropower applications. Despite growing interest in GWVT technology, previous studies typically vary multiple geometric parameters simultaneously, leaving the isolated effect of blade curvature radius insufficiently understood. To address this research gap, an experimental investigation was conducted using a conical-basin GWVT with three runner configurations having identical blade inclination (66°) but different curvature radii (0.10 m, 0.20 m, and 0.30 m). Experiments were performed under controlled flow rates of 800, 1025, and 1300 LPM. Turbine torque, rotational speed, mechanical power, and efficiency were measured using a Prony brake dynamometer and magnetic tachometer. Each test condition was repeated three times, and the resulting data were analyzed using mean and standard deviation analysis to ensure measurement reliability and experimental consistency. The results show that increasing blade curvature significantly improves hydrodynamic interaction between the vortex flow and the runner. The runner with a curvature radius of 0.30 m achieved the best performance, producing a peak torque of 15.92 Nm, mechanical power of 109.95 W, and maximum efficiency of 66.43% at moderate flow conditions. The findings establish a direct curvature-performance relationship, demonstrating that larger curvature enhances tangential momentum transfer, prolongs blade-vortex interaction, and improves torque generation in low-head vortex systems. This study empirically confirms blade curvature as the key parameter governing hydrodynamic coupling and energy extraction in GWVT runners, while providing a practical design guideline to improve efficiency in low-head decentralized micro-hydropower systems.