Incipient sooting tendency of oxygenated fuels doped in ethylene counterflow diffusion flames

Zepeng Li, Peng Liu*, Carson Chu, Suk Ho Chung, William L. Roberts

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

2 Scopus citations


The incipient sooting tendencies of oxygenated fuels in counterflow diffusion flames were systematically assessed by doping selected oxygenate fuels into the baseline fuel of ethylene with various mixing ratios. Laser light scattering and planar laser-induced fluorescence (PLIF) techniques were adopted. The critical oxygen mole fractions at different mixing ratios were identified with the use of laser scattering. It is found that the critical oxygen mole fraction varies with oxygenates, suggesting that the effect of mixing ethylene with oxygenates is highly sensitive to the types of oxygenate. While the doping of acetone moderately promoted the incipient sooting tendency, the doping of methanol, acetic acid, formic acid, and diethyl carbonate suppressed the formation of incipient soot. On the other hand, the doping of ethanol, dimethyl carbonate, diethyl ether, and dimethoxymethane had weak influences on the incipient sooting tendency. The production of polycyclic aromatic hydrocarbons (PAHs) of different sizes were measured by PLIF. The results show there was a strong correlation between the incipient sooting tendency and the production of large PAHs. One important finding is that, at their sooting limits, the total oxygen-to-carbon ratio of a stoichiometric fuel/oxygen mixture is linearly correlated with the mixing ratio of the ethylene-oxygenate mixture. This slope of these two quantities can be defined as an incipient sooting index (ISI) of oxygenated fuels for ranking their tendency of incipient sooting formation. Having the slopes correlated well with the oxygenates’ hydrogen/oxygen ratio, a reasonably accurate prediction of critical oxygen mole fractions from the molecule information of oxygenated fuels can be achieved.

Original languageEnglish (US)
Article number112284
JournalCombustion and Flame
StatePublished - Oct 2022

Bibliographical note

Funding Information:
The research reported in this publication was supported by funding from King Abdullah University of Science and Technology (KAUST), under award number BAS/1/1370- 01–01 and URF/1/4688–01–01 .

Publisher Copyright:
© 2022


  • Counterflow flame
  • Incipient soot
  • Oxygenated fuel
  • Sooting limit
  • Sooting tendency

ASJC Scopus subject areas

  • General Chemistry
  • General Chemical Engineering
  • Fuel Technology
  • Energy Engineering and Power Technology
  • General Physics and Astronomy


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