Evaluation of guide vanes effect over runner Francis turbine sediment erosion using a quasi-two dimensional approach

Francis turbines are widely used in hydroelectric power plants all over the world, Ecuador is not an exception to this trend. Hence, Francis turbine design and assessment have taken importance in order to provide in-house design methods to enhance their performance in the region. The volcanic nature of the region facilitates sediment formation, which produces drastic erosion problems in many Francis turbines. Since guide vanes set the inlet flow velocity of the runner and erosion is related with the velocity distribution through this latter, this work evaluates guide vane profiles using a quasi-two dimensional approach to assess the impact of guide vane design on erosion rate. For this aim, parametric analysis and a mean line analysis are employed for the conceptual geometrical design, which then is coupled with a panel vortex model to assess the two dimensional hydro profiles for the guide vanes. Thus, the velocity triangles at entry and exit of the guide vane-runner setup can be related to the erosion rate within the runner. At this stage the calculations were carried out at the BEP and for the validation experimental data from the San Francisco hydroelectric power plant was used. The results show how the model developed captures main performance trends and enables the correlation of erosion with the geometrical features of the guide vanes. The method used is accurate enough for preliminary design and its low computational resources with versatility make it suitable for optimization routines for erosion proof designs.