Visible and Chemical Flame Lengths of Acetylene/Air Jet Diffusion.
Visible and Chemical Flame Lengths of Acetylene/Air Jet
Wade, R. W.; Gore, J. P.
NISTIR 5904; October 1996.
National Institute of Standards and Technology. Annual
Conference on Fire Research: Book of Abstracts.
October 28-31, 1996, Gaithersburg, MD, 41-42 pp, 1996.
Sponsor:National Institute of Standards and Technology,
Available from: National Technical Information Service
Order number: PB97-153514
fire research; fire science; diffusion flames; jet
flames; flame length; acetylene; air; turbulent flames
The lengths of turbulent diffusion flames have been
widely studied experimentally and theoretically. Flame
lengths are typically defined in terms of the mean
temperature, chemical composition or luminosity along
the axis. For many flames, the interchangeable use of
the different definitions, that frequently occurs in the
literature, may cause qualitative and quantitative
discrepancies amongst data and confusion regarding the
importance of different physical processes. There are
several existing models for flame length correlations.
The significant assumption in most of the flame length
correlation is that the visible flame length is
proportional to local chemical state. One complication
that these existing models do not address is that of
soot. If a large fraction of the fuel mass is converted
to soot, then the visible flame length would be
determined by radiation emitted by the hot soot
particles. The radiation transferred from the hot soot
particles to the surroundings lowers that temperature of
the soot and flame gas mixtures making the flame
non-luminous. Gore et al. have shown that the peak
temperature along the centerline occurs much closer to
the injector exit in strongly radiating flames than in
weakly radiating flames. Therefore, the definition of
flame length based on this visible luminosity is
inconsistent. Based on the above, the objective of the
present work was to obtain flame lengths based on
measurements of axial gas species concentrations.