Francis turbine dynamic stresses measurements at model and prototype scales

Abstract

A strain gauge and pressure measurement campaign on a model runner with a modern design was performed. The reference prototype runner was commissioned in 2013 and strain gauge measurements on the prototype are available for comparison. The model runner was fabricated by stereolithography in a plastic composite selected to obtain mechanical homology. The instrumented model runner was tested from 14% to 100% of the maximum guide vane opening at various speed factors (nED ) by combining different head levels and rotating speeds as well as varying the cavitation coefficient (sigma) so that the effect of each studied parameter can be identified and quantified. By adjusting the speed and the head of the model test, it was also possible to induce rotor-stator resonance of the runner and to confirm expected hydrodynamic damping behaviour. Finally, the model scale pressure and stress measurements are compared to the ones obtained by both prototype measurements and CFD/FSI simulations.