Influence of CF3I, CF3Br, and CF3H on the High-Temperature Combustion of Methane.
Influence of CF3I, CF3Br, and CF3H on the
High-Temperature Combustion of Methane.
Babushok, V. I.; Noto, T.; Burgess, D. R. F., Jr.;
Hamins, A.; Tsang, W.
Combustion and Flame, Vol. 107, No. 4, 351-367,
methane; high temperature; combustion; kinetics;
validation; temperature effect; ignition delay; reaction
time; additives; radicals
The effects of a number of flame retardants (CF3I,
CF3Br, and CF3H) on the high-temperature reactions of
methane with air in a plug flow reactor are studied by
numerical simulations using the Sandia Chemkin Code.
The dependence of (a) the ignition dely and (b) time for
substantially complete reaction as a function of
temperature and additive concentrations are calculated.
In agreement with experiments, the ignition delay can be
increased or decreased by the addition of retardants.
The reaction time is always increased by additives. The
mechanism for these effects has been examined. It is
concluded that the ignition delay is controlled by the
initial retardant decomposition kinetics, which releases
active species into the system. These species can
either terminate or initiate chains. The reaction time
is largely a function of the concentrations of the
active radicals H, OH, and O that are formed during the
combustion process. It is shown that their
concentrations, particularly those of H atoms, are
lowered in the presence of the retardants. We find that
the chemical mechanism governing reaction time is very
similar to that which controls the flame velocity and a
correlation between decreases in flame velocity and
H-atom concentration is demonstrated. The calculations
suggest that relative reaction time and H-atom
concentrations should be effective measures for the
estimation of retardant effectiveness.