Experimental investigation of the local wave speed in a draft tube with cavitation vortex rope

C. Landry, Arthur Tristan Favrel, A. Müller, C. Nicolet, K. Yamamoto, F. Avellan

Research output: Contribution to journalConference article

10 Citations (Scopus)

Abstract

Hydraulic machines operating in a wider range are subjected to cavitation developments inducing undesirable pressure pulsations which could lead to potential instability of the power plant. The occurrence of pulsating cavitation volumes in the runner and the draft tube is considered as a mass source of the system and is depending on the cavitation compliance. This dynamic parameter represents the cavitation volume variation with the respect to a variation of pressure and defines implicitly the local wave speed in the draft tube. This parameter is also decisive for an accurate prediction of system eigen frequencies. Therefore, the local wave speed in the draft tube is intrinsically linked to the eigen frequencies of the hydraulic system. Thus, if the natural frequency of a hydraulic system can be determined experimentally, it also becomes possible to estimate a local wave speed in the draft tube with a numerical model. In the present study, the reduced scale model of a Francis turbine (v=0.29) was investigated at off-design conditions. In order to measure the first eigenmode of the hydraulic test rig, an additional discharge was injected at the inlet of the hydraulic turbine at a variable frequency and amplitude to excite the system. Thus, with different pressure sensors installed on the test rig, the first eigenmode was determined. Then, a hydro-acoustic test rig model was developed with the In-house EPFL SIMSEN software and the local wave speed in the draft tube was adjusted to obtain the same first eigen frequency as that measured experimentally. Finally, this method was applied for different Thoma and Froude numbers at part load conditions.

Original languageEnglish
Article number032037
JournalIOP Conference Series: Earth and Environmental Science
Volume22
DOIs
Publication statusPublished - 2014 Jan 1
Externally publishedYes
Event27th IAHR Symposium on Hydraulic Machinery and Systems, IAHR 2014 - Montreal, Canada
Duration: 2014 Sep 222014 Sep 26

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cavitation
vortex
hydraulics
turbine
Froude number
compliance
power plant
acoustics
speed
sensor
software
prediction
test
parameter

ASJC Scopus subject areas

  • Environmental Science(all)
  • Earth and Planetary Sciences(all)

Cite this

Experimental investigation of the local wave speed in a draft tube with cavitation vortex rope. / Landry, C.; Favrel, Arthur Tristan; Müller, A.; Nicolet, C.; Yamamoto, K.; Avellan, F.

In: IOP Conference Series: Earth and Environmental Science, Vol. 22, 032037, 01.01.2014.

Research output: Contribution to journalConference article

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