Francis Type Turbine Runner Design and Comparison with Model Test Results

Cavitation wear and hydraulic efficiency decrease in hydroelectric power plants have frequently been the subject of various research and studies. A hydroelectric power plant built on the Kızılırmak River in Türkiye started operating in 1960 and has not been subjected to any large-scale rehabilitation work other than general maintenance until today. The power plant has 4 Francis-type turbines, each with a power of 32 MW. Due to cavitation wear of turbine runners over the years, performance loss, vibration, and noise problems have arisen. Moreover, the maximum turbine hydraulic efficiency, which was 92% in 1960, the year the power plant was commissioned, decreased to 87.9% according to the efficiency measurements carried out at the power plant in 2020. In this study, Computational Fluid Dynamics (CFD) analyses were accomplished with Reynolds averaged Navier Stokes (RANS) calculations for the redesign of the Francis-type turbine runner and finally checked by a model test according to IEC 60193. It was observed that the model test and CFD results were close to each other, especially at the best efficiency point. The maximum turbine hydraulic efficiency, which was calculated as 94.95% as a result of CFD analysis at the nominal head, was calculated as 95.19% by the model test. The x-blade shape created in the redesigned turbine runner blades ensured homogeneous pressure distribution and increased the hydraulic efficiency significantly.