Numerical investigation of a Pelton turbine at several operating conditions

Abstract

The use of Computational Fluid Dynamics (CFD) for predicting the flow behaviour in Pelton turbines is limited by the complex nature of the flow, interaction between the jets and interference of the water after the impact on the buckets. Besides, validation of the numerical results in such turbines is usually challenging due to the unsteadiness of the flow properties. Hence, time-dependent analysis with multi-phase models is required for obtaining such solutions. This paper conducts a CFD analysis on a Pelton turbine using RANS based Eulerian scheme. The fluid domain consists of three successive buckets placed in their corresponding circumferential locations, along with a spear valve, which is adjusted for various operating conditions. Such a domain assumes that the interaction of the jet on the buckets takes place for a maximum of three buckets at any particular time. The results of the CFD analysis are compared with the experimental results for all the studied opening conditions. The objective of this work is to build a suitable numerical model that can be applied to any Pelton turbines, such that a complete performance curve of the turbine can be generated. The flow pattern between entry and exit of the bucket obtained from CFD is compared with images taken from a high speed camera in rotating frame of reference. The results of the numerical analysis are found to be in a good agreement with the experimental data.