The Internal Flow Calculation In A Runner Of The Francis Turbine

Francis turbines have the characteristic of cheap, developed and wide specific speeds. They can be widely used in power stations that the water heads from several meters to several handlers ones. With the water power market turning to our country and the rapid development of our water power projects, the needs of Francis turbines are increasing. So it is significant to enhance the Francis turbine's hydraulic performance and stability.Along with the development of numeration, computer technology and the mechanism's lucubrating of the revolving hydro- machinery, numerical simulation has become a mainly method to research the internal flow and the performance of hydro-machinery. Based on the finite volume method and Simple algorithm, standard k-s turbulence model with standard wall function was adopted to simulate the flow within the signal turbine route way and the majority using FLUENT. In order to provide reliable character of the internal flow for the turbine's performance, the mechanism of the HL260 turbine's internal flow has been studied deeply by analyzing the distributing of velocity and stress.In this paper, 3-D viscous numerical simulation of the Francis turbine was carried outon different operating conditions. The study focused on velocity field, pressure field and back flow status within the turbine, and results were analyzed and compared under various working conditions. The cavitations' performance and hydro performance were analyzed and quantificational forecasted. So we can find out the flow within the Francis turbine completely and corresponding measure for enhancing the performance of the turbine. So we can draw results as flows:1. By study, we found that the calculation results are similar by numerating the signal turbine route way and the majority of the unit. The velocity and stress were semblable very much The relative error of the maximal pressure was less than 0.121 percent.2. By observation and analysis, we catch the velocity and stresses on blades are asymmetry, some circumfluence on the blades up inlet and some eddies on the down inlet of the turbine in the off-design operating conditions especially in the low discharge conditions. That is one of the most import factors make the turbine's efficiency down.Aims at those phenomenons, some corresponding, for instance, to minish the angle ofinlet have been put forward.