Impact of flow non-axisymmetry on swirling flow dynamics and receptivity to acoustics

Samuel Hansford, Jacqueline O'connor, Kiran Manoharan, Santosh Hemchandra

Research output: Chapter in Book/Report/Conference proceedingConference contribution

9 Scopus citations

Abstract

In this study, we experimentally investigate both the intrinsic instability characteristics and forced response to transverse acoustic excitation of a non-reacting, swirling flow for application to combustion instability in annular gas turbine engines. The non-axisymmetry of the velocity field is quantified using an azimuthal mode decomposition of the time-averaged velocity field that shows that(1) the flow field is largely axisymmetric,(2) axisymmetry decreases with downstream distance, and (3) forcing does not significantly alter the time averaged shape of the flow field. The flow field is analyzed in a companion linear stability analysis that shows that the most unstable modes in the flow field are m=-1 and m=-2, which agrees with the experimental observations and shows that the intrinsic dynamics of this flow field are non-axisymmetric with respect to the jet axis. The linear stability analysis captures the spatial variation of mode strength for certain modes, particularly mode m=-1, but there are some deviations from the experimental results. Most notably, these deviations occur for mode m=0 at radii away from the jet axis. Experimental results of the forced response of the flow indicate that the intrinsic instability characteristics of the flow field have an impact on the forced-response dynamics. Response of the flow field to a velocity anti-node in a standing transverse acoustic field shows non-axisymmetric vortex rollup and the dominance of the m=-1 and m=1 azimuthal modes in the fluctuating flow field. In the presence of a pressure anti-node, the m=0 mode of the fluctuating flow field is very strong at the jet exit, indicating an axisymmetric response, and ring vortex shedding is apparent in the flow measurements from high-speed PIV. However, further downstream, the strength of the axisymmetric mode decreases and the m=-1 and m=1 modes dominate, resulting in a tilting of the vortex ring as it convects downstream. Implications for flame response to transverse acoustic fields are discussed.

Original languageEnglish (US)
Title of host publicationCombustion, Fuels and Emissions
PublisherAmerican Society of Mechanical Engineers (ASME)
ISBN (Electronic)9780791856697, 9780791856697
DOIs
StatePublished - Jan 1 2015
EventASME Turbo Expo 2015: Turbine Technical Conference and Exposition, GT 2015 - Montreal, Canada
Duration: Jun 15 2015Jun 19 2015

Publication series

NameProceedings of the ASME Turbo Expo
Volume4B

Other

OtherASME Turbo Expo 2015: Turbine Technical Conference and Exposition, GT 2015
CountryCanada
CityMontreal
Period6/15/156/19/15

All Science Journal Classification (ASJC) codes

  • Engineering(all)

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