Numerical Simulation On Internal Flow In Hydraulic Turbines With Deviated Splitter Vanes In Sandy Water

Up to now, much progress has been achieved in the research on the damage mechanism of sand abrasion in the hydraulic turbines operating in sandy rivers. However, the theories and techniques are not mature.During the operation of Francis turbines in sandy rivers, the cavitation and abrasion damages of the turbine are severe. These problems could be worse if operating in high water head. The cavitation and abrasion damages of turbines are key issues for the safety operation of a hydropower station. Actually, the problems of cavitation and abrasion damages could be alleviated by using hydraulic turbines with deviated splitter vanes. However, this problem is not solved completely. Hence there is a necessity to study the solid-liquid two-phase flow in hydraulic turbines with deviated splitter vanes. Discussions on the flow mechanisms of sandy water flow field in hydraulic turbines could serve as a basis for the design of hydraulic turbines with deviated splitter vanes.All flow passage components of the turbine are considered as a whole in this dissertation. Based on the N-S Equations, the flowing conditions of clear water and sandy water in the turbine are numerically simulated, respectively. The main contents of this dissertation are as follows:Firstly, according to the technical parameters of hydraulic design of a practical hydraulic turbine, the commercial software Unigraphics is adopted to establish the 3D geometric models of the diversion components, guide apparatus, runner and draft tube of the turbine. And the 3D models of all flow passage components are introduced into the commercial software of Gambit which could generate grids and set up boundary conditions for the models.Secondly, the internal flows of the turbine in clear water under large flow rate, optimum conditions and small flow rate are numerically calculated.Thirdly, the internal flows of the turbine in sandy water while the particle volume concentrations and the diameters are fixed, and the flow rates are different; the particle volume concentrations and flow rates are fixed, and the particle diameters are different; the particle diameters and flow rates are fixed, and the concentrations are different, are numerically calculated. Through comparing and analyzing the numerical calculation results in clear water and sandy water, the rules of cavitations and abrasion damage of all flow passage components of hydraulic turbines with deviated splitter vanes are obtained. And the results are also basically consistent with those happened during the operation of a practical power station.