Effect of CF3I Compared to CF3Br on OH and Soot Concentrations in Co-Flowing Propane/Air Diffusion Flames.
Effect of CF3I Compared to CF3Br on OH and Soot
Concentrations in Co-Flowing Propane/Air Diffusion
Flames.
(954 K)
Smyth, K. C.; Everest, D. A.
Combustion Institute, Symposium (International) on
Combustion, 26th. Proceedings. Volume 1. July
28-August 2, 1996, Napoli, Italy, Combustion Institute,
Pittsburgh, PA, 1385-1393 pp, 1996.
Keywords:
combustion; soot; diffusion flames; propane
Abstract:
The recent halt in the production of CF3Br because of
its deleterious effect on stratospheric ozone levels has
intensified the search for new suppressants with
comparable properties. In contrast to most proposed
alternatives, earlier investigations of CF3I have
reported excellent extinction efficiencies, sometimes
superior to CF3Br on a molar basis. These findings have
spurred an interest in elucidating more clearly the
chemical effects produced by iodine-containing
suppressants. In the present study, OH and soot
concentrations have been measured using fluorescence
imaging and laser-induced incandescence methods,
respectively, in a co-flowing, axisymmetric,
atmospheric-pressure propane/air diffusion flame
inhibited by CF3Br and CF3I. In addition, broadband
molecular fluorescence (attributed to polycyclic
aromatic hydrocarbons) has been monitored, and peak
temperatures have been measured using two-line OH
laser-induced fluorescence. Overall, the two
suppressants behave similarly when added to both the air
and fuel streams, with the most notable exception being
the greaer enhancement of soot production for CF3Br
addition at subextinction concentrations. CF3I is found
to slightly superior to CF3Br under our experimental
conditions in terms of [1] requiring smaller mole
fraction concentrations at extinction and [2] producing
less within-flame soot. The reductions in the OH
concentrations with agent additions are essentially the
same for CF3I and CF3Br.
Building and Fire Research Laboratory
National Institute of Standards and Technology
Gaithersburg, MD 20899