Reliable prediction of pressure pulsations in the draft tube of a Francis turbine at medium and deep part load: A validation of CFD-results with experimental data.

Jürgen Schiffer-Rosenberger, Helmut Benigni, Helmut Jaberg, Martin Ehrengruber

Research output: Contribution to conferencePaper

Abstract

The Francis turbine flow at any discharge significantly below the
Best Efficiency Point is generally accompanied by secondary flow
phenomena occurring in the runner and/or draft tube of the turbine.
While an inter-blade vortex structure appears at deep part load, the
typical helical vortex rope appears at medium load. Both flow
phenomena cause more or less severe pressure pulsations and may
result in operational restrictions of the turbine. The present
publication presents that a reliable CFD-based prediction of the
pressure pulsations in the draft tube can nowadays be achieved if
appropriate modelling and evaluation techniques are used. Unsteady
Scale Adaptive Simulations (SAS) were used for the calculation of
the flow at various operation points ranging from deep part load to
full load. In addition to the evaluation of the resulting hydraulic
turbine efficiency pressure pulsations were recorded at various
positions at the inlet and outlet of the draft tube cone. In parallel to
the CFD study a comprehensive measurement campaign was
performed at a model test rig. The comparison of the pressure
pulsations calculated by means of CFD and measured on the test rig
shows that both approaches match well. Even the cavitation patterns
occurring at part load and captured in the experiment agree well
with the cavitation structures found in course of the CFD study.
Original languageEnglish
PagesPaper 6.04
Publication statusPublished - 15 Oct 2018
EventHydro 2018: Progress through Partnerships - Danzig, Poland
Duration: 15 Oct 201817 Oct 2018

Conference

ConferenceHydro 2018
CountryPoland
CityDanzig
Period15/10/1817/10/18

Fields of Expertise

  • Sustainable Systems

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