Cascade Wake Vortex Changes The Numerical Simulation

When water flows through the Francis turbine's blades or vane cascade,it will be separated, and forming many complex swirl. Vortex usually come from the rear of guide vanes, runner and the export part of runner blades. The vortex will go through a process of generation, migration to downstream and demise finally.Vortices exported from guide vane may easily lead the resonance of vanes, guide vanes and blades, and may even stimulate the resonance of local flow around, resulting in varying degrees of damage to water-turbine. At the same time, the vortex going down, will deteriorate flow conditions of entrance of the draft tube,and increase the pressure pulsation of draft tube,also affect the stability and efficiency of water-turbine. Therefore, it is necessary to research the changes of vortex exported from the vane cascade.In this paper, a three-dimensional solid model of the distributor and runner of HLA351-LJ-170 model water-turbine is established and computed field was meshed by nonstructural grid. Realizableκ-εturbulence model and SIMPLEC algorithm are used to do three-dimensional steady calculations under a number of conditions,after setting a moving mesh surface, RNGκ-εturbulence model and the PISO algorithm are used to do distributor-runner interaction three-dimensional unsteady calculations under a number of conditions. The distribution of static pressure, velocity in computed field and velocity vector diagram was obtained, the pictures reveal the change process of the vortices exported from the vane cascade.