Quantitative Measurements of Enhanced Soot Production in a Flickering Methane/Air Diffusion Flame.
Quantitative Measurements of Enhanced Soot Production in
a Flickering Methane/Air Diffusion Flame.
(707 K)
Shaddix, C. R.; Harrington, J. E.; Smyth, K. C.
Combustion Institute. Symposium (International) on
Combustion, 25th. Proceedings. Abstracts of Symposium
Papers. Session 09-F: Soot Formation. July 31-August
5, 1994, Irvine, CA, Combustion Institute, Pittsburgh,
PA, 93 pp, 1994.
Combustion and Flame, Vol. 99, 723-732, 1994.
Keywords:
diffusion flames; extinction; lasers; incandescence;
methane; soot; flame flicker
Abstract:
Integrated models of soot production and oxidation are
based upon experimental results obtained in steady,
laminar flames. For successful application of these
descriptions to turbulent combustion, it is instructive
to test predictions of soot concentrations against
experimental measurements obtained in time-varying
flowfields. This paper reports quantitative
measurements of the local soot volume fraction in a
co-flowing, flickering CH4/air diffusion flame burning
at atmospheric pressure. Acoustic forcing of the fuel
flow rate is used to phase lock the periodic flame
flicker close to the natural flicker frequency. Our
measurements show that soot production is four times
greater for a forcing condition in which flame tip
clipping occurs, compared with a steady flame burning
with the same mean fuel flow velocity. The soot field
in the flickering flame has been characterized using
tomographic reconstruction of extinction data obtained
at 632.8 nm, laser-induced incandescence (LII) images
calibrated against steady CH4/air extinction results,
and vertically polarized scattering data. The LII
method is found to track the soot volume fraction
closely and to give better signal-to-noise than the
extinction measurements in both the steady and
time-varying flowfields. A Mie analysis of these
results suggests that the flickering flame exhibits
similar number densities but large particle sizes than
the corresponding steady flame.
Selected Papers
Building and Fire Research Laboratory
National Institute of Standards and Technology
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