The effect of fuel staging on the structure and instability characteristics of swirl-stabilized flames in a lean premixed multi-nozzle can combustor

Janith Samarasinghe, Wyatt Culler, Bryan David Quay, Domenic A. Santavicca, Jacqueline O'connor

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

4 Scopus citations

Abstract

Fuel staging, or fuel splitting, is a commonly used strategy for the suppression of combustion instabilities in gas turbine engines. In multi-nozzle combustor configurations, this is achieved by varying the fuel flow rate to the different nozzles. The effect of fuel staging on flame stabilization and heat release rate distribution (referred to as flame structure), and self-excited instability characteristics is investigated in a research can combustor employing five small-scale lean-premixed industrial nozzles. The nozzles are arranged in a "four-around-one" configuration and fuel staging is achieved by injecting additional fuel to the middle nozzle. An operating condition was identified where all five nozzles were fueled equally and the combustor was subject to a self-excited instability. At the operating condition considered, the self-excited instabilities are suppressed with fuel staging: this is true for cases where overall equivalence ratio is increased by staging (by only increasing the fuel flow rate to the middle nozzle) as well as cases where overall equivalence ratio is kept constant while staging (by simultaneously decreasing the fuel flow rate of the outer nozzles while increasing the fuel flow rate to the middle nozzle). Fuel staging causes variations in the distribution of timeaveraged heat release rate in the regions where adjacent flames interact. The locations of highest heat release rate fluctuation are not altered with increased fuel staging but the fluctuation amplitude is reduced. A breakup in the monotonic phase behavior that is characteristic of convective disturbances is observed with increased fuel staging, resulting in a lower pressure fluctuation amplitude. In particular, the monotonic variation in phase in the middle flame and the region where adjacent flames interact is out-of-phase with that of the outer flames, resulting in a cancellation of the global heat release rate oscillations. The distribution of local Rayleigh integral within the combustor shows that during a self-excited instability, the regions of highest heat release rate fluctuation are in phase-with the pressure fluctuation. When staging fuel is introduced, these regions fluctuate out-of-phase with the pressure fluctuation, further illustrating that fuel staging suppresses instabilities by altering the phase relationship of convective disturbances that travel along the flame front.

Original languageEnglish (US)
Title of host publicationCombustion, Fuels and Emissions
PublisherAmerican Society of Mechanical Engineers (ASME)
ISBN (Electronic)9780791850848
DOIs
StatePublished - Jan 1 2017
EventASME Turbo Expo 2017: Turbomachinery Technical Conference and Exposition, GT 2017 - Charlotte, United States
Duration: Jun 26 2017Jun 30 2017

Publication series

NameProceedings of the ASME Turbo Expo
Volume4A-2017

Other

OtherASME Turbo Expo 2017: Turbomachinery Technical Conference and Exposition, GT 2017
CountryUnited States
CityCharlotte
Period6/26/176/30/17

All Science Journal Classification (ASJC) codes

  • Engineering(all)

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  • Cite this

    Samarasinghe, J., Culler, W., Quay, B. D., Santavicca, D. A., & O'connor, J. (2017). The effect of fuel staging on the structure and instability characteristics of swirl-stabilized flames in a lean premixed multi-nozzle can combustor. In Combustion, Fuels and Emissions (Proceedings of the ASME Turbo Expo; Vol. 4A-2017). American Society of Mechanical Engineers (ASME). https://doi.org/10.1115/GT201763688