Comparison of mechanical stress in Pelton Buckets between simulation and measurement

Abstract

Thinner structures, lead to higher efficiencies, but also to higher mechanical stresses. The increase of the hydraulic performances of Pelton runners is hence limited by mechanical stress constraints. The design process of Pelton runner therefore includes stress and hydraulic assessment during profile development phase. This assessment is based on the combination of Finite Element Method (FEM) for the mechanical stress and computational fluid dynamics (CFD) for the hydraulic behavior of the machine. This combined approach enables the generation of hydraulic profiles with high efficiency while respecting defined limits for the stress. The validation of the combined simulation is achieved by comparison with prototype measurements. For several projects the runners have been equipped with strain gauges in the root and close to the cut-out to record the deformation for different operating points. The comparison with numerical simulation results shows some limitations of the approach but concludes with a satisfying agreement between numerical simulation and measurement.