Quantification of variation in combustion instability amplitude in a multi-nozzle can combustor

Seth Westfall, Olivia Sekulich, Wyatt Culler, Stephen J. Peluso, Jacqueline O’Connor

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

1 Scopus citations

Abstract

In this work, we quantify the level of variation in unstable combustion oscillation amplitudes and identify the source of this variation in a multi-nozzle can combustor. At conditions where pollutant emissions are reduced, lean-premixed combustors can undergo thermoacoustic instability when pressure and heat release rate oscillations couple. A commonly used method for suppressing instability is fuel staging, which is a method where fuel is unevenly distributed between nozzles in a multi-nozzle combustor. Our work follows others who have characterized the effect of fuel staging on combustion instability and the mechanisms by which it works during both steady-state and transient operation. One of the outcomes from our previous work was that certain instability operating points display a high level of pressure oscillation amplitude variation. Instead of oscillating at a constant limit-cycle amplitude, the pressure oscillation amplitude varies significantly in time. In this work, we use the concept of permutation entropy to quantify the level of variation in the pressure fluctuation amplitude. We correlate the level of variation with a number of state variables over a range of operating conditions, 291 test cases in all. These state variables include mixture equivalence ratio; transient timescale, amplitude, and direction; hardware temperatures; gas temperatures; and thermoacoustic damping and growth rates. Significant pressure oscillation amplitude variation occurs when the thermoacoustic damping rate is low. The damping and growth rates can be low for a number of reasons, but they are highly correlated with the metal temperature of the centerbody, where the flames are anchored; lower temperatures result in lower damping rates during stable operation and lower growth rates during unstable operation. These results show the importance of the thermal boundary condition on the time-dependent behavior of the thermoacoustic instability.

Original languageEnglish (US)
Title of host publicationCombustion, Fuels, and Emissions
PublisherAmerican Society of Mechanical Engineers (ASME)
ISBN (Electronic)9780791884133
DOIs
StatePublished - 2020
EventASME Turbo Expo 2020: Turbomachinery Technical Conference and Exposition, GT 2020 - Virtual, Online
Duration: Sep 21 2020Sep 25 2020

Publication series

NameProceedings of the ASME Turbo Expo
Volume4B-2020

Conference

ConferenceASME Turbo Expo 2020: Turbomachinery Technical Conference and Exposition, GT 2020
CityVirtual, Online
Period9/21/209/25/20

All Science Journal Classification (ASJC) codes

  • Engineering(all)

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