Improvement of partial load performance of Francis turbine runner

Turbine operation range has had to be extended to meet economic requirements in recent years. Specifically, efficiency under partial flow conditions has been improved by the development of low loss runners. The most effective runner design achieves suitable flow distribution from the runner exit, because the loss mechanism in the partial flow is due to swirl loss in the draft tube. In this study, a new design concept for improving turbine efficiency under low flow rate conditions is established and confirmed by both computation and experiment. The performance predicted by the CFD is compared with the experimental results and good agreement is observed. This report describes some runner shape improvement techniques to mitigate the effects of the flow conditions in a partial flow scenario, and validates their results through model performance testing.