The application of computational fluid dynamics (CFD) in the redesign or rehabilitation of hydraulic turbines appears to be necessary in order to improve their efficiency and cost-effectiveness beyond the traditional redesign practices. The runner geometry considered within the computational domain was modelled by using a three-dimensional laser triangulation scanner coupled with a portable coordinate measurement system. The runner geometry was generated by a number of 3D sub models, one for each of the main components of the runner, crown, band and a blade. In order to obtain a blade geometry a portable coordinate measurement system based on optical digitalization technology (scanner technology) was used. A numerical optimization methodology is developed and applied to a Francis turbine. The hydrodynamic performance analysis was investigated by application of a three dimensional Navier-Stoke commercial turbomachinery oriented CFD code. Analysis of the flow through the spiral case and stay vanes was carried out so as to include appropriate flow effects induced by these components and boundary conditions at the inlet of the wicket. A CFD analysis for the wicket and runner was carried out to generate the so called reference solution. Then, the runner blades design was optimized by a process implemented in a commercial CFD code which combines genetic algorithms and a trained artificial neural network (ANN). A database of geometries and their respective CFD computations were computed in order to determine the optimum geometry for a given objective function. The flow within hydraulic turbines has a thin boundary layer and noticeable pressure gradients. Hence, the CFD computations were carried out using the Sparlat-Allmaras turbulence model. After optimization cycle convergence, an increment not only in efficiency but also in power was obtained. The optimized runner represented by a parametric model achieves considerably higher efficiency than the reference runner. Efficiency versus power curve was used to compare data from measurements at the power station for the reference runner versus the parametric optimized runner model. Results have shown that application of CFD based optimization can modify and improve runners design so as to increase the efficiency and power of installed hydraulic power stations.

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