Performance Optimization of Francis Turbines in Small Hydro Power Plants Using CFD and Experimental Validation

Abstract

This study presents the performance optimization of Francis turbines used in small hydro power plants through an integrated approach combining Computational Fluid Dynamics and experimental validation. The baseline turbine exhibited limitations such as non-uniform flow distribution, pressure fluctuations, higher cavitation risk, and reduced efficiency, particularly under part-load conditions. To address these issues, a CFD-based design optimization was carried out by modifying key parameters including runner blade geometry, guide vane angles, and draft tube configuration. The optimized turbine demonstrated a significant improvement in hydraulic efficiency, increasing from 82–86% to 88–92%, while experimental results confirmed efficiency values in the range of 87–91%, showing strong agreement with simulation outcomes. Power output was enhanced with more stable performance under rated conditions. Flow uniformity at the runner inlet improved considerably, leading to reduced hydraulic losses and smoother operation. Pressure distribution across the turbine blades became more uniform, minimizing mechanical stress and improving structural reliability. Furtherore, the optimized design reduced cavitation zones, thereby lowering the cavitation index and enhancing turbine durability. Torque stability was improved, resulting in reduced mechanical vibrations and better operational consistency. The efficiency at part-load conditions increased from 70–75% to 78–85%, with experimental validation indicating values between 76–83%, highlighting improved adaptability under varying flow conditions. In addition, draft tube losses were minimized, contributing to better energy recovery, while optimized guide vane performance enabled improved flow control and regulation. Overall, the results indicate that the proposed optimization approach significantly enhances turbine performance, reliability, and operational lifespan. The close correlation between CFD predictions and experimental findings validates the effectiveness of the methodology, making it a practical and efficient solution for improving the performance of Francis turbines in small hydro power applications.