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Visible and Chemical Flame Lengths of Acetylene/Air Jet Diffusion.


pdf icon Visible and Chemical Flame Lengths of Acetylene/Air Jet Diffusion. (178 K)
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, Gaithersburg, MD

Available from:

National Technical Information Service
Order number: PB97-153514

Keywords:

fire research; fire science; diffusion flames; jet flames; flame length; acetylene; air; turbulent flames

Abstract:

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.