PICO-SCALE OPEN FLUME PROPELLER WATER TURBINE PERFORMANCE UNDER VARIATION IN AIRFOIL THICKNESS-TO-CHORD RATIO

Abstract

Air pollution from coal-fired power plants contributes approximately 44% of Indonesia’s CO₂ emissions. Transitioning to renewable sources, such as hydroelectric power, offers a viable solution, particularly with open-flume propeller turbines in remote areas. This study investigates the effect of T/C ratios on pico-scale open-flume propeller turbines using NACA 44XX airfoils. Three configurations (0.11, 0.12, and 0.13) with varying rotational speeds were evaluated using computational fluid dynamics (CFD) simulations with mesh motion in ANSYS Fluent, along with analytical methods for torque, power output, and efficiency. T/C 0.13 consistently delivered the best performance, reaching a maximum efficiency of 15.39% at 850 rpm. In contrast, the analytical method found that the maximum efficiency of that configuration is approximately 26% at 1100 RPM. The deviation between the analytical and numerical results arises from the analytical method's limitations in capturing the viscous shear flow around the turbine blades and the gap-clearance loss. The pressure distribution analysis revealed that T/C 0.13 maintained the most balanced high–low pressure zones, minimizing early flow separation. T/C 0.12 exhibited instability at high RPM due to less stable pressure differentials, whereas T/C 0.11 maintained stability with sharper pressure gradients and a higher risk of separation despite lower output. These findings emphasize the role of optimal blade geometry in improving efficiency, pressure–velocity stability, and flow control in small-scale water turbines. However, the lack of experimental testing in this study limits the validity of its results; further experimentation is needed.