Instability mechanism in a swirl flow combustor: Precession of vortex core and influence of density gradient

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

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

25 Scopus citations

Abstract

Combustion instability is a serious problem limiting the operating envelope of present day gas turbine systems using a lean premixed combustion strategy. Gas turbine combustors employ swirl as a means for achieving fuel-air mixing as well as flame stabilization. However swirl flows are complex flows comprised of multiple shear layers as well as recirculation zones which makes them particularly susceptible to hydrodynamic instability. We perform a local stability analysis on a family of base flow model profiles characteristic of swirling flow that has undergone vortex breakdown as would be the case in a gas turbine combustor. A temporal analysis at azimuthal wavenumbers m = 0 and m = 1 reveals the presence of two unstable modes. A companion spatio-temporal analysis shows that the region in base flow parameter space for constant density density flow, over which m = 1 mode with the lower oscillation frequency is absolutely unstable, is much larger that that for the corresponding m = 0 mode. This suggests that the dominant self-excited unstable behavior in a constant density flow is an asymmetric, m=1 mode. The presence of a density gradient within the inner shear layer of the flow profile causes the absolutely unstable region for the m = 1 to shrink which suggests a possible explanation for the suppression of the precessing vortex core in the presence of a flame.

Original languageEnglish (US)
Title of host publicationCombustion, Fuels and Emissions
PublisherAmerican Society of Mechanical Engineers (ASME)
ISBN (Electronic)9780791856680, 9780791856680
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
Volume4A

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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    Manoharan, K., Hansford, S., O'Connor, J., & Hemchandra, S. (2015). Instability mechanism in a swirl flow combustor: Precession of vortex core and influence of density gradient. In Combustion, Fuels and Emissions (Proceedings of the ASME Turbo Expo; Vol. 4A). American Society of Mechanical Engineers (ASME). https://doi.org/10.1115/GT2015-42985