Effect of pressure on the transfer functions of premixed methane and propane swirl flames

Francesco Di Sabatino, Thibault Guiberti, Wesley Boyette, William L. Roberts, Jonas P. Moeck, Deanna Lacoste

Research output: Contribution to journalArticlepeer-review

43 Scopus citations


This paper reports on the effect of pressure on the response of methane–air and propane–air swirl flames to acoustic excitation of the flow. These effects are analyzed on the basis of the flame transfer function (FTF) formalism, experimentally determined from velocity and global OH* chemiluminescence measurements at pressures up to 5 bar. In parallel, phase-locked images of OH* chemiluminescence are collected and analyzed in order to determine the associated flame dynamics. Flame transfer functions and visual flame dynamics at atmospheric pressure are found to be similar to previous studies with comparable experimental conditions. Regardless of pressure, propane flames exhibit a much larger FTF gain than methane flames. For both fuels, the effect of pressure primarily is to modify the gain response at the local maximum of the FTF, at a Strouhal number around 0.5 (176 Hz). For methane flames, this gain maximum increases monotonically with pressure, while for propane flames it increases from 1 to 3 bar and decreases from 3 to 5 bar. At this frequency and regardless of pressure, the flame motion is driven by flame vortex roll-up, suggesting that pressure affects the FTF by modifying the interaction of the flame with the vortex detached from the injector rim during a forcing period. The complex heat transfer, fluid dynamics, and combustion coupling in this configuration does not allow keeping the vortex properties constant when pressure is increased. However, the different trends of the FTF gain observed for methane and propane fuels with increasing pressure imply that intrinsic flame properties and fuel chemistry, and their variation with pressure, play an important role in controlling the response of these flames to acoustic forcing.
Original languageEnglish (US)
Pages (from-to)272-282
Number of pages11
JournalCombustion and Flame
StatePublished - Apr 24 2018

Bibliographical note

KAUST Repository Item: Exported on 2020-10-01
Acknowledged KAUST grant number(s): 1975
Acknowledgements: This work is funded by the Center of Competitive Funding from King Abdullah University of Science and Technology (Grant No. 1975).


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