Inhibition of Premixed Methane-Air Flames by Fluoroethanes and Fluoropropanes.
Inhibition of Premixed Methane-Air Flames by
Fluoroethanes and Fluoropropanes.
Linteris, G. T.; Burgess, D. R. F., Jr.; Babushok, V.
I.; Zachariah, M. R.; Tsang, W.; Westmoreland, P. R.
Combustion and Flame, Vol. 113, No. 1/2, 164-180, April
chemical inhibition; flame chemistry; flame models;
flame retardants; flame speed
This paper presents experimental and modeling results
for laminar premixed methane-air flames inhibited by the
fluoroethanes C2F6, C2HF5, and C2H2F4, and experimental
results for the fluoroporpanes C3HF7 and C3F8. The
modeling results are in good agreement with the
measurements. At high inhibitor mole fractions, the
calculated burning velocities are very sensitive to the
values of the specific reaction rate constant for
initial inhibitor reaction, whereas at low mole
fraction, the flame speed is only moderately sensitive
to the rate constants used for reactions of the
inhibitor fragments. For the fluoroethanes, calculated
flame structures are used to determine the reaction
pathways for inhibitor decomposition and the mechanisms
of inhibition, as well as to explain the enhanced soot
formation observed for the inhibitors C2HF5, C2H2F4 and
C3HF7. The agents reduce the burning velocity of rich
and stiochiometric flames mostly by raising the
effective equivalence ratio and lowering the adiabatic
flame temperature. For lean flames, the inhibition is
primarily kinetic, since inhibitor reaction helps to
maintain the final temperature. The peak radical
concentrations are reduced beyond that due to the
temperature effect through reactions of fluorinated
species with radicals.