Design and development of a hybrid Francis-type turbine runner using numerical methods

Francis-type turbine runners are custom designed to meet the hydraulic and operational requirements of each hydroelectric power plant (HEPP). Sarıyar HEPP, one of Turkey's major plants that has been in operation for over 50 years, consists of four units incorporating two different runner designs. This situation leads to increased complexity in maintenance processes, longer design durations, and higher production costs. Within the scope of the Sarıyar HEPP Rehabilitation Project, an innovative approach has been adopted to overcome these challenges by developing a single, high-efficiency hybrid runner geometry that can be used across all units. By replacing the two separate designs with a unified configuration, this hybrid design simplifies production and assembly processes and provides significant economic advantages in operation. In this study, the design and analysis of the hybrid runner were carried out using Computational Fluid Dynamics (CFD) methods. The hydraulic performance and cavitation characteristics of the design were evaluated under various operating conditions. The CFD analyses revealed that the newly developed hybrid runner significantly increased turbine efficiency and substantially reduced hydraulic losses. Additionally, the optimized blade incidence angles and flow-conforming alignment, secondary flow structures such as vortices and separations, which are critical for long-term turbine reliability, were minimized. The implementation of this hybrid design represents a practical and innovative solution for enhancing the service life and performance of aging hydropower plants, while also supporting the advancement of domestic engineering capabilities. This study demonstrates that integrating reverse engineering with CFD-based optimization can provide a more cost-effective and higher-performance alternative to traditional rehabilitation approaches and offers a reference methodology for similar projects in the hydropower sector.