000255358 001__ 255358
000255358 005__ 20190507143841.0
000255358 0247_ $$2doi$$a10.1007/s00348-018-2552-x
000255358 02470 $$2DOI$$a10.1007/s00348-018-2552-x
000255358 037__ $$aARTICLE
000255358 245__ $$aExperimental investigation of the sloshing motion of the water free surface in the draft tube of a Francis turbine operating in synchronous condenser mode
000255358 260__ $$c2018-05-15
000255358 269__ $$a2018-05-15
000255358 336__ $$aJournal Articles
000255358 520__ $$aHydropower units may be required to operate in condenser mode to supply reactive power. In this operating mode, the water level in the turbine or pump-turbine is decreased below the runner by closing the guide vanes and injecting pressurized air. While operating in condenser mode the machine experiences power losses due to several air–water interaction phenomena which cause air losses. One of such phenomena is the sloshing motion of the water free surface below the runner in the draft tube cone of a Francis turbine. The objective of the present work is to experimentally investigate the sloshing motion of the water free surface in the draft tube cone of a reduced scale physical model of a Francis turbine operating in condenser mode. Images acquisition and simultaneous pressure fluctuation measurements are performed and an image processing method is developed to investigate amplitude and frequency of the sloshing motion of the free surface. It is found that this motion is excited at the natural frequency of the water volume and corresponds to the azimuthal wavenumber m=1 of a rotating gravity wave. The amplitude of the motion is perturbed by wave breaking and it decreases by increasing the densimetric Froude number. The sloshing frequency slightly increases with respect to the natural frequency of the water volume by increasing the densimetric Froude number. Moreover, it results that this resonant phenomenon is not related to the torque perturbation.
000255358 700__ $$g241436$$0248056$$aVagnoni, Elena
000255358 700__ $$aFavrel, Arthur
000255358 700__ $$aAndolfatto, Loïc
000255358 700__ $$aAvellan, François
000255358 773__ $$q95$$k6$$j59$$tExperiments in Fluids
000255358 8560_ $$felena.vagnoni@epfl.ch
000255358 909C0 $$pLMH$$mfrancois.avellan@epfl.ch$$0252135$$xU10309
000255358 909CO $$pSTI$$particle$$ooai:infoscience.epfl.ch:255358
000255358 960__ $$aelena.vagnoni@epfl.ch
000255358 961__ $$aalain.borel@epfl.ch
000255358 973__ $$aEPFL$$sPUBLISHED$$rREVIEWED
000255358 980__ $$aARTICLE
000255358 981__ $$aoverwrite