Effect of Inhibitor Concentration on the Inhibition Mechanism of Fluoromethanes in Premixed Methane-Air Flames.
Effect of Inhibitor Concentration on the Inhibition
Mechanism of Fluoromethanes in Premixed Methane-Air
Linteris, G. T.
American Chemical Society. Halon Replacements -
Technology and Science. National Meeting, 208th.
Proceedings. ACS Symposium Series 611. August 21-25,
1994, Washington, DC, American Chemical Society,
Washington, DC, Miziolek, A. W.; Tsang, W.,
Editor(s)(s), 260-274 pp, 1995.
chemical inhibition; flame chemistry; flame models;
flame retardants; flame speed
The mechanisms of inhibition premixed methane-air flames
in the presence of difluoromethane, trifluoromethane,
and tetrafluoromethane are studied. The chemistry of
these agents is expected to be similar to that of agents
which may be used as replacements for CF3Br. The
burning rates of premixed methane-air flames stabilized
on a Mache-Hebra nozzle burner are determined using the
total area method from a schlieren image of the flame.
The three inhibitors are tested over an initial mole
fraction from 0 to 8% at nominal values of the fuel-air
equivalence ration, equal to 0.9, 1.0, and 1.1. The
measured burning rate reductions are compared with those
predicted by numerical solution of the mass, species,
and energy conservation equations employing a detailed
chemical kinetic mechanism recently developed at the
National Institute of Standards and Technology (NIST).
Even in this first test of the kinetic mechanism on
inhibited hydrocarbon flames, the numerically predicted
burning rates are in excellent agreement for CH2F2 and
CF4 and within 35% for CF3H. The effects of inhibitor
concentration on the decomposition pathway of the
inhibitors and on the H, O, and OH radical production
and consumption rates are discussed. The modified
decomposition pathway and the reduced radical
consumption explain the diminishing effectiveness of
CF3H and CH2F2 at higher concentrations.