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Main Title: Investigation of the Global Mode in Swirling Combustor Flows: Experimental Observations and Local and Global Stability Analysis
Author(s): Terhaar, Steffen
Paredes, P.
Oberleithner, Kilian
Theofilis, V.
Paschereit, Christian Oliver
Type: Article
Language Code: en
Abstract: Self-excited helical flow oscillations are frequently observed in gas turbine combustors. In the present work a new approach is presented tackling this phenomenon with stability concepts. Three reacting swirling flows are investigated. All of them undergo vortex breakdown, but only two of them show self-excited global flow oscillations at well-defined frequencies. The oscillations feature a precession of the vortex core and synchronized Kelvin-Helmholtz instabilities in the shear layers. Based on the mean flow fields, local and global linear hydrodynamic stability analyses are carried out. The dampening effect of the Reynolds stresses is accounted for by an eddy viscosity estimated from the experimental results. Both the local and the global analysis successfully identify linear global modes as being responsible for the large-scale flow oscillations and successfully predict their frequency. However, only the global analysis accurately predicts a globally stable flow field for the case without the oscillation, while the local analysis overpredicts the global growth rate. The predicted spatial distribution of the amplitude functions agree very well to the experimentally identified global mode. This successful application of global and local stability concepts to a complex and practically relevant flow configuration paves the way for the application of theoretically-founded passive and active control strategies.
Issue Date: 2015
Date Available: 19-Apr-2018
DDC Class: 530 Physik
Subject(s): turbulent swirling flow
global mode
local and global stability analysis
eddy viscosity
Journal Title: Procedia IUTAM
Publisher: Elsevier BV
Publisher Place: Red Hook, NY
Volume: 14
Publisher DOI: 10.1016/j.piutam.2015.03.079
Page Start: 553
Page End: 562
ISSN: 2210-9838
Appears in Collections:FG Experimentelle Strömungsmechanik » Publications

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