抄録
In order to extend operation range of a reversible pump-turbine, it is important to increase vortex core stability in the draft tube specifically in partial load operation. It is clarified that the behavior of a vortex core is subjected to the runner outlet swirl intensity. Thus, the tangential velocity control at the outlet of the runner by modifying runner vane geometry is very effective to stabilize the vortex core. This mechanism was confirmed by the experiments up to now, but it is difficult to optimize the runner geometry at that time. CFD is now very useful tool for designing runner geometry to improve the performance. To simulate the behavior of a vortex core, unsteady flow computation has to be used. This paper describes the simulation by using the unsteady flow computation to investigate the vortex core behavior in a draft tube for a Francis pump-turbine.
