CFD-Based Design Optimization for Hydro Turbines

A computational fluid dynamics-based design system with the integration of three blade design approaches, automatic mesh generator and CFD codes enables a quick and efficient design optimization of turbine components. It is applied to a Francis turbine rehabilitation project with strict customer requirements to provide over 3% increase in peak efficiency, 13% upgrade in power, and improved cavitation characteristics. Extensive turbulent flow simulations are performed for both the existing and new turbines at design and off design conditions. In order to take into account the interactions between different components, particularly the effects between the rotating and stationary parts, coupling calculations based on the implicit coupling method under multiple frames of reference are carried out for the entire turbine model. As a result, the runner and guide vanes are optimized to the greatest extent, and the stay vanes are locally modified with a possible minimum cost under the geometrical constraints of the existing machine. The performance of the new design is verified by model tests, and exceeds required improvements.