000255336 001__ 255336
000255336 005__ 20190812210022.0
000255336 0247_ $$a10.1088/1755-1315/12/1/012053$$2doi
000255336 02470 $$2DOI$$a10.1088/1755-1315/12/1/012053
000255336 037__ $$aCONF
000255336 245__ $$aOn the upper part load vortex rope in Francis turbine: Experimental investigation
000255336 260__ $$c2010$$bInternational Association For Hydraulic Research
000255336 269__ $$a2010
000255336 300__ $$a11
000255336 336__ $$aConference Papers
000255336 490__ $$aFrancis Turbines$$v6A.3
000255336 520__ $$aThe swirling flow developing in Francis turbine draft tube under part load operation leads to pressure fluctuations usually in the range of 0.2 to 0.4 times the runner rotational frequency resulting from the so-called vortex breakdown. For low cavitation number, the flow features a cavitation vortex rope animated with precession motion. Under given conditions, these pressure fluctuations may lead to undesirable pressure fluctuations in the entire hydraulic system and also produce active power oscillations. For the upper part load range, between 0.7 and 0.85 times the best efficiency discharge, pressure fluctuations may appear in a higher frequency range of 2 to 4 times the runner rotational speed and feature modulations with vortex rope precession. It has been pointed out that for this particular operating point, the vortex rope features elliptical cross section and is animated of a self-rotation. This paper presents an experimental investigation focusing on this peculiar phenomenon, defined as the upper part load vortex rope. The experimental investigation is carried out on a high specific speed Francis turbine scale model installed on a test rig of the EPFL Laboratory for Hydraulic Machines. The selected operating point corresponds to a discharge of 0.83 times the best efficiency discharge. Observations of the cavitation vortex carried out with high speed camera have been recorded and synchronized with pressure fluctuations measurements at the draft tube cone. First, the vortex rope self rotation frequency is evidenced and the related frequency is deduced. Then, the influence of the sigma cavitation number on vortex rope shape and pressure fluctuations is presented. The waterfall diagram of the pressure fluctuations evidences resonance effects with the hydraulic circuit. The time evolution of the vortex rope volume is compared with pressure fluctuations time evolution using image processing. Finally, the influence of the Froude number on the vortex rope shape and the associated pressure fluctuations is analyzed by varying the rotational speed.
000255336 542__ $$fCC BY
000255336 700__ $$aNicolet, C
000255336 700__ $$aZobeiri, A
000255336 700__ $$aMaruzewski, P
000255336 700__ $$aAvellan, F
000255336 7112_ $$dSeptember 20-24, 2010$$cTimişoara, Romania$$a25th Symposium on Hydraulic Machinery and Systems
000255336 773__ $$q1-11$$j1$$tProceedings of the 25th Symposium on Hydraulic Machinery and Systems
000255336 8560_ $$femilie.reynaud@epfl.ch
000255336 8564_ $$uhttps://infoscience.epfl.ch/record/255336/files/On%20the%20upper%20part%20load%20vortex%20rope%20in%20Francis%20turbine%3A%20Experimental%20investigation.pdf$$s1779187
000255336 8564_ $$xpdfa$$uhttps://infoscience.epfl.ch/record/255336/files/On%20the%20upper%20part%20load%20vortex%20rope%20in%20Francis%20turbine%3A%20Experimental%20investigation.pdf?subformat=pdfa$$s2178627
000255336 909C0 $$xU10309$$pLMH$$mfrancois.avellan@epfl.ch$$0252135
000255336 909CO $$qGLOBAL_SET$$pconf$$pSTI$$ooai:infoscience.epfl.ch:255336
000255336 960__ $$aemilie.reynaud@epfl.ch
000255336 961__ $$alaurence.gauvin@epfl.ch
000255336 973__ $$aEPFL$$rREVIEWED
000255336 980__ $$aCONF
000255336 981__ $$aoverwrite