Mixture-forced flame transfer function measurements and mechanisms in a single-nozzle combustor at elevated pressure

Nick Bunce, Jong Guen Lee, Bryan D. Quay, Domenic A. Santavicca

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

    7 Scopus citations

    Abstract

    The mixture-forced flame transfer function of a lean fully premixed single-nozzle research combustor operating on natural gas is determined experimentally at combustor pressures from 1 to 4 atm. Measurements are made over a range of inlet temperatures (100-300°C), mean velocities (25-35 m/s), and equivalence ratios (0.5-0.75). A rotating siren device, located upstream of the nozzle, is used to modulate the flow rate of the premixed fuel-air mixture. The amplitude and phase of the resultant velocity fluctuation are measured near the exit of the nozzle using the two-microphone method. The measured normalized velocity fluctuation serves as the input to the flame transfer function. In this study, the amplitude of the normalized velocity fluctuation is fixed at 5% and the modulation frequency is varied from 100 to 500 Hz. The output of the flame transfer function is the normalized global heat release fluctuation, which is measured using a photomultiplier tube and interference filter which captures the CH* chemiluminescence from the entire flame. In addition, two-dimensional CH* chemiluminescence images are taken for both forced and unforced flames. Forced flame images are phase-synchronized with the velocity fluctuation. The flame transfer functions for all of the operating conditions tested exhibit similar behavior. At low frequencies, the gain is initially greater than one, but then decreases as the frequency increases. After reaching a minimum, the gain increases with increasing frequency to a second peak and then again decreases. At certain operating conditions, the gain exhibits a second minimum. At frequencies corresponding to the minima in gain the phase curve exhibits inflection points. Regions of maximum and minimum gain are explained in terms of the constructive and destructive interference of vorticity fluctuations generated in the inner and outer shear layers. Phase-synchronized images are analyzed to isolate the fluctuating component of heat release. At frequencies where the gain is amplified, this analysis shows that the heat release fluctuations caused by the vorticity fluctuations generated in the inner and outer shear layers are in phase. While when the gain is at its minimum value, the heat release fluctuations are out of phase and therefore destructively interfere.

    Original languageEnglish (US)
    Title of host publicationASME 2011 Turbo Expo
    Subtitle of host publicationTurbine Technical Conference and Exposition, GT2011
    Pages1317-1326
    Number of pages10
    EditionPARTS A AND B
    DOIs
    StatePublished - Dec 1 2011
    EventASME 2011 Turbo Expo: Turbine Technical Conference and Exposition, GT2011 - Vancouver, BC, Canada
    Duration: Jun 6 2011Jun 10 2011

    Publication series

    NameProceedings of the ASME Turbo Expo
    NumberPARTS A AND B
    Volume2

    Other

    OtherASME 2011 Turbo Expo: Turbine Technical Conference and Exposition, GT2011
    CountryCanada
    CityVancouver, BC
    Period6/6/116/10/11

    All Science Journal Classification (ASJC) codes

    • Engineering(all)

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