NVKS_presentation_spring

Some new high head Francis runners have experienced

that resonance is excited during operation and caused

fatigue fractures. Therefore the natural frequency

is a important characteristic of high head Francis

runners. However, the natural frequency of the runner

is dependent of the medium it is surrounded by and

nearby rigid surfaces. This is called the added mass

effect, and it makes it difficult to predict the natural

frequency of the runner while it is in operation.

Goals

• Identify the current research status on natural

frequencies of Francis runners, and other rotating

constructions.

• Do response frequency measurements on a disc

and pump turbine.

• Identify the added mass effect of water through experiments.

Valentín, D., et al., Experimental study on the added mass and damping of a disc submerged in a partially fluid-filled

tank with small radial confinement. Journal of FluidsandStructures(2014),

Supervisor: Pål-Tore Storli

Co-supervisor: Torbjørn K. Nielsen, Petter

Østby

By Frode Kristoffer Amundsen Kjøsnes

Master Thesis

Waterpower Laboratory

Measurement of Natural

Frequencies in a Circular Disk

in Air and Water