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Background
Damaged runner, Svartisen, Norway
In recent years several high head Francis turbines have experienced breakdown after a short
time of operation. It is thought that these breakdowns is caused by Runner Stator Interaction
(RSI) which induces pressure pulsations on the runner. If these pulsations have a frequency
close to the natural frequency of the runner, resonance can occur and, in a short amount of
time, cracks or total failure could be the result. To avoid this, an understanding of the natural
frequencies of the turbine is important for turbine manufactures. The natural frequencies
of the runner depends on a number of factors, which need to be modelled, in order to get
accurate calculations, even at an early stage of runner construction.
The recent beakdowns is the best proof of the lack of knowledge concerning this problem.
The goal of this thesis is to check the computer simulated frequencies against the measured
frequencies from a model
Master Thesis
Waterpower Laboratory
Simulation of Natural
Frequencies of a Francis
Turbine in Air and Water
By Øyvind Moen Fjeld
Supervisor: Torbjørn Nielsen