Relative polycyclic aromatic hydrocarbon concentrations in unsteady counterflow diffusion flames

J. Xiao, E. Austin, W. L. Roberts*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

28 Scopus citations


Qualitative measurements of polycyclic aromatic hydrocarbon (PAH) concentrations made in counterflow diffusion flames subjected to both steady and oscillating strain rates are presented. Planar laser-induced fluorescences was used to make spatially and temporally resolved measurements of the relative concentrations of PAH. The measurements for each PAH size class were made as a function of strain rate, forcing frequency, and fuel type. The peak laser-induced fluorescence spectra from PAHs is known to be a function of the number of benzene rings that make up the particular PAH. It was found that, with increasing strain rate, the intensity of PAH fluorescence decreases dramatically, though unequally, among the three size classes measured. With an unsteady strain rate, the PAH intensity oscillates in phase for frequencies below 50 Hz. When nondimensionalized relative concentration is plotted, it is shown that the smaller PAHs continue to respond to the instantaneous strain rate at a higher frequency than larger PAHs.

Original languageEnglish (US)
Pages (from-to)691-713
Number of pages23
JournalCombustion science and technology
Issue number4
StatePublished - Apr 2005
Externally publishedYes


  • PAH
  • PLIF
  • Unsteady diffusion flames

ASJC Scopus subject areas

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


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