Inhibition of Premixed Carbon Monoxide-Hydrogen-Oxygen-Nitrogen Flames by Iron Pentacarbonyl.
Inhibition of Premixed Carbon
Monoxide-Hydrogen-Oxygen-Nitrogen Flames by Iron
Rumminger, M. D.; Linteris, G. T.
NISTIR 6360; 36 p. October 1999.
Combustion and Flame, Vol. 120, No. 4, 451-464, March
Order number: PB99-150443
carbon monoxide; iron pentacarbonyl; chemical inhibition
This paper presents measurements of the burning velocity
of premixed CO-H2-O2-N2 flames with and without the
inhibitor Fe(CO)5 over a range of initial H2 and O2 mole
fractions. A numerical model is used to simulate the
flame inhibition using a gas-phase chemical mechanism.
For the uninhibited flames, predictions of burning
velocity are excellent and for the inhibited flames, the
qualitative agreement is good. The agreement depends
strongly on the rate of the CO+OH<->CO2+H reaction and
the rates of several key iron reactions in catalytic H-
and O-atom scavenging cycles. Most of the chemical
inhibition occurs through a catalytic cycle that
converts O atoms into O2 molecules. This O-atom cycle is
not important in methane flames. The H-atom cycle that
causes most of the radical scavenging in the methane
flames is also active in CO-H2 flames, but is of
secondary importance. To vary the role of the H- and
O-atom radical pools, the experiments and calculations
are performed over a range of oxygen and hydrogen mole
fraction. The degree of inhibition is shown to be
related to the fraction of the net H- and O-atom
destruction through the iron species catalytic cycles.
The O-atom cycle saturates at a relatively low inhibitor
mole fraction (~100 ppm), while the H-atom cycle
saturates at a much higher inhibitor mole fraction (~400
ppm). The calculations reinforce the previously
suggested idea that catalytic cycle saturation effects
may limit the achievable degree of chemical inhibition.