Development of Splitter Runner for Pump-Turbine

We have been investigating several technical measures to improve hydraulic performance of pump-turbines which are to be installed into pumped storage power stations with a wide operating-head-range. A splitter runner, which has long blades. and short blades in circumferentially alternate positions, can be one of the means for achieving this aim. In this paper, characteristic flow-patterns in the splitter runner and appropriate design methods based on them are discussed. As far as flowpattern is concerned, influence of circumferential pitch between a long blade and a short blade is focused on especially. Through flow analyses for some runners, it has become clear that making the short blade move to its pressure side direction enhances turbine operation performance. After optimization of the runner by flow analysis at the design stage, model tests were conducted to verify its hydraulic performance and to optimize it further. Finally, the developed splitter runners for low/high specific-speed pump-turbines proved to demonstrate better hydraulic performance and smaller pressure fluctuation compared to conventional runners.