Publication detail

Connection between inlet velocity field and diffuser flow instability

RUDOLF, P.

Czech title

Spojitost mezi vstupním rychlostním polem a nestabilitou proudění v difuzoru

English title

Connection between inlet velocity field and diffuser flow instability

Type

journal article - other

Language

en

Original abstract

Simulations of the flow in a straight diffuser were carried out for different inlet velocity profiles equivalent to the real turbine operating points. Frequencies and magnitudes of pressure pulsations of the rotating vortex rope were recorded. Two types of vortices were detected. The first one is a thin vortex with higher frequency and relatively low pressure amplitudes corresponding to higher part load turbine operation. For lower loads, further from best efficiency point, a huge vortex rotating on higher diameter appears, which is accompanied by massive pressure pulsations, but with lower frequency. Connections of these two regimes with inlet circumferential velocity com-ponent are discussed in the paper.

Czech abstract

Byly provedeny simulace proudění v přímém difuzoru se vstupními rychlostními profily odpovídajícími skutečné Francisově turbíně. Výsledky ukázaly na dva rozdílné typy vírových struktur. První je tenký vír s vyšší frekvencí a relativně nízkými amlitudami tlaku. Tento vír se objevuje pro vyšší částečné zatížení turbíny. Pro nižší průtoky, dále od optimálního bodu, se objevuje masívní vír doprovázený výraznými pulzacemi tlaku. Frekvence jeho rotace je ovšem nižší. Článek dává do souvislosti různá vstupní rychlostní pole se vznikem rpzdílného charakteru vírových struktur.

English abstract

Simulations of the flow in a straight diffuser were carried out for different inlet velocity profiles equivalent to the real turbine operating points. Frequencies and magnitudes of pressure pulsations of the rotating vortex rope were recorded. Two types of vortices were detected. The first one is a thin vortex with higher frequency and relatively low pressure amplitudes corresponding to higher part load turbine operation. For lower loads, further from best efficiency point, a huge vortex rotating on higher diameter appears, which is accompanied by massive pressure pulsations, but with lower frequency. Connections of these two regimes with inlet circumferential velocity com-ponent are discussed in the paper.

Keywords in Czech

nestability, difuzor, vírový cop, vodní turbína

Keywords in English

instability, diffuser, vortex rope, hydraulic turbine

RIV year

2009

Released

01.06.2009

Publisher

University of West Bohemia

Location

Plzeň

ISSN

1802-680X

Journal

Applied andComputational Mechanics

Volume

3

Number

1

Pages from–to

177–184

Pages count

8

BIBTEX


@article{BUT47117,
  author="Pavel {Rudolf},
  title="Connection between inlet velocity field and diffuser flow instability",
  journal="Applied andComputational Mechanics",
  year="2009",
  volume="3",
  number="1",
  month="June",
  pages="177--184",
  publisher="University of West Bohemia",
  address="Plzeň",
  issn="1802-680X"
}