International Journal of Fluid Machinery and Systems
Online ISSN : 1882-9554
ISSN-L : 1882-9554
Special issue for invited papers from 24th IAHR Symposium
Selected papers from the 24th IAHR Symposium on Hydraulic Machinery and Systems, October 27-31, 2008, Foz do Iguassu-Brazil are published in the special issue.
Dynamic Analysis of Francis Runners - Experiment and Numerical Simulation
Stefan LaisQuanwei LiangUrs HenggelerThomas WeissXavier EscalerEduard Egusquiza
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2009 Volume 2 Issue 4 Pages 303-314

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Abstract

The present paper shows the results of numerical and experimental modal analyses of Francis runners, which were executed in air and in still water. In its first part this paper is focused on the numerical prediction of the model parameters by means of FEM and the validation of the FEM method. Influences of different geometries on modal parameters and frequency reduction ratio (FRR), which is the ratio of the natural frequencies in water and the corresponding natural frequencies in air, are investigated for two different runners, one prototype and one model runner. The results of the analyses indicate very good agreement between experiment and simulation. Particularly the frequency reduction ratios derived from simulation are found to agree very well with the values derived from experiment. In order to identify sensitivity of the structural properties several parameters such as material properties, different model scale and different hub geometries are numerically investigated. In its second part, a harmonic response analysis is shown for a Francis runner by applying the time dependent pressure distribution resulting from an unsteady CFD simulation to the mechanical structure. Thus, the data gained by modern CFD simulation are being fully utilized for the structural design based on life time analysis. With this new approach a more precise prediction of turbine loading and its effect on turbine life cycle is possible allowing better turbine designs to be developed.

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© 2009 Turbomachinery Society of Japan, Korean Fluid Machinery Association, Chinese Society of Engineering Thermophysics, IAHR
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