Numerical Simulation of Jet in a Pelton Turbine

Abstract

In case of predicting the performance of prototype Pelton turbine from a model test, a scale effect has been ignored so far. However, it is getting clear that there is an outstanding deviation from a classical similarity laws. The direction of the deviation is completely inverse against the case of reaction turbines, namely, the performance of prototype is worse than the predicted one. In order to analyze this negative scale effect, the behavior of jets should be considered more precisely. In this study, the unsteady jet issuing from a Pelton turbine nozzle was calculated numerically using HSMAC method under the assumption of axisymmetric flow. The calculation shows that the needle considerably affects the velocity distribution in the jet and the velocity distribution in the jet changes by the head.