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Post-Flame Soot. Final Report. September 1994-December 1995.


pdf icon Post-Flame Soot. Final Report. September 1994-December 1995. (1243 K)
Sorensen, C. M.

NIST GCR 96-694; 34 p. June 1996.

Sponsor:

National Institute of Standards and Technology, Gaithersburg, MD

Available from:

National Technical Information Service
Order number: PB96-193701

Keywords:

soot; acetylene; diffusion flames; flame research; light scattering; smoke; sphere sizes

Abstract:

The smoke agglomerates produced by a co-annular diffusion flame with acetylene fuel were characterized by sampling/microscopy and light scattering measurements. Particles were sampled at various heights above the flame using both thermophoretic sampling and impaction. Transmission electron microscopy was used for the smaller agglomerates obtained by thermophoretic sampling and optical microscopy was used for analysis of particles as large as .4 mm in diamter collected by impaction. The number of primary spheres was estimated from the projected area of the agglomerate and the primary sphere size. The fractal analysis extended over four orders of magnitude in the radius of gyration - the widest range studied for smokes. The fractal dimension and the prefactor were determined for smoke collected for a range of heights above the flame. The structure factor measurements were performed for angles ranging from 1DG to 150DG as a function of height and fuel flow. No Guinier regime was observed at a flow rate of 30 ml/min. Modeling results suggest that the slight dip in the structure factor measurements might result from intercluster scattering. A condition for the transition from Brownian agglomeration to gelation is derived.