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Role of Particles in Counterflow Diffusion Flames Inhibited by Iron Pentacarbonyl.


pdf icon Role of Particles in Counterflow Diffusion Flames Inhibited by Iron Pentacarbonyl. (1047 K)
Rumminger, M. D.; Linteris, G. T.

Combustion Institute/Western States Secion. U.S. Sections of the Combustion Institute, 2nd Joint Meeting. Hosted by Lawrence Berkeley National Laboratory. Proceedings. March 25-28, 2001, Oakland, CA, 1-17 pp, 2001.

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Keywords:

diffusion flames; counterflow flames; particles; fire suppression; nanoparticles; flame synthesis; flame inhibition; halon alternatives; nucleation; iron pentacarbonyl; metal oxides

Abstract:

Laser light scattering and thermophoretic sampling have been used to investigate particle formation in a methane-air counterflow diffusion flames inhibited by iron pentacarbonyl (Fe(CO)5) added to the fuel or the oxidizer stream. Flame calculations which incorporate only gas-phase chemistry are used to assist in interpretation of the experimental results. In flames with the inhibitor added to the oxidizer stream, the region of particle formation overlaps with the region of high H-atom concentration, and particle formation may interfere with the inhibition chemistry. When the inhibitor is added to the fuel stream, significant condensation of metal or metal oxide particles is found, and implies that particles prevent active inhibiting species from reaching the region of high radical concentration. As the inhibitor loading increases, the maximum scattering cross section increases sharply, and the difference between the measured and predicted inhibition effect widens, suggesting that particle formation is the cause of the deviation. Thermophoretic sampling in low strain rate flames indicates that the particles have diameters between 5 nm and 25 nm. Thermophoresis affects the nanoparticle distribution in the flames, in some cases causing particles to cross the stagnation plane. The scattering magnitude in the counterflow diffusion flames appears to be strongly dependent on the residence time, and relatively independent of the peak flame temperature.