Transient 3D CFD Simulation of a Pelton turbine – A state of the art approach for Pelton turbine development and optimisation

The complexity of the flow structure in Pelton turbines makes it challenging to gain a detailed insight into the local flow processes. However, CFD methods offer vast potential for developing and optimising Pelton turbines due to these complex flow conditions. In a comprehensive examination, a six-nozzle prototype Pelton turbine with 19 buckets has been investigated using 3D CFD simulations. First, the steady simulations of the manifold and the unsteady runner simulation have been performed with a mesh-based, commercial CFD code, whereby a two-equation turbulence model and the homogeneous two-phase model were used. Then, to limit the simulation time and the computational cost, symmetry was applied in the runner simulation, and also a sophisticated meshing strategy. Subsequently, the simulation results are analysed. The examination of the manifold provided a detailed insight into the occurrence of losses and local flow conditions, especially upstream the nozzle, which allows for a better understanding of the jet shape. Furthermore, the results of the runner simulation were analysed with special regard to the jet-bucket interaction from start to end of the impingement cycle of a particular bucket. Finally, the enhancement potential could be derived from the summary.