Detail publikace

Experimental investigation of swirl number influence on spiral vortex structure dynamics

ŠTEFAN, D. HUDEC, M. URUBA, V. PROCHÁZKA, P. URBAN, O. RUDOLF, P.

Originální název

Experimental investigation of swirl number influence on spiral vortex structure dynamics

Typ

článek ve sborníku ve WoS nebo Scopus

Jazyk

angličtina

Originální abstrakt

The hydraulic turbines are recently forced to operate far away from the optimal conditions in order to balance fluctuations in electricity generation. In case of Francis, pump and propeller turbines, using only single control component of guide vanes, it means that in regions where the high residual swirl enters the draft tube, the flow is decelerated and convenient conditions for the vortex rope development are created. Such flow conditions are considered to be the triggering mechanism for occurrence of different forms of vortex structures in the Francis turbine draft tube, e.g. spiral or straight vortex rope at part load or full load respectively. Independently on the vortex rope shape the unsteady pressure fields develop producing periodic stress on turbine components and possibly resulting in noise, blade cracks, runner lift, power swing, etc. To study and mimic such flow conditions, a simplified device of vortex generator apparatus is employed. Thanks to its design, the vortex generator enables to change the ratio between fluxes of axial momentum and tangential moment of momentum of generated swirl. Then, the behavior of vortex structure changes in a similar way as the flow rate variation in the draft tube of Francis turbine. For above mentioned reasons the unsteady cavitating spiral vortex is experimentally studied using both high speed video record and particle image velocimetry (PIV). The main focus is on change of vortex dynamics regarding to the swirl number variation. The proper orthogonal decomposition (POD) together with the classical fast Fourier transformation (FFT) are employed to extract dominant modes and frequencies from experimental data.

Klíčová slova

vortex breakdown; vortex rope; PIV; swirling flow; swirl generator

Autoři

ŠTEFAN, D.; HUDEC, M.; URUBA, V.; PROCHÁZKA, P.; URBAN, O.; RUDOLF, P.

Vydáno

15. 6. 2021

Nakladatel

IOP Publishing

ISSN

1755-1307

Periodikum

IOP Conference Series: Earth and Environmental Science

Ročník

774

Číslo

1

Stát

Spojené království Velké Británie a Severního Irska

Strany od

012085

Strany do

012085

Strany počet

10

URL

https://iopscience.iop.org/article/10.1088/1755-1315/774/1/012085

Plný text v Digitální knihovně

http://hdl.handle.net/11012/200962

BibTex

@inproceedings{BUT171994,
  author="David {Štefan} and Martin {Hudec} and Václav {Uruba} and pavel {procházka} and Ondřej {Urban} and Pavel {Rudolf}",
  title="Experimental investigation of swirl number influence on spiral vortex structure dynamics",
  booktitle="IOP Conference Series-Earth and Environmental Science",
  year="2021",
  journal="IOP Conference Series: Earth and Environmental Science",
  volume="774",
  number="1",
  pages="012085--012085",
  publisher="IOP Publishing",
  doi="10.1088/1755-1315/774/1/012085",
  issn="1755-1307",
  url="https://iopscience.iop.org/article/10.1088/1755-1315/774/1/012085"
}