EFFECT OF FERROCENE ON SOOT IN A PREVAPORIZED ISOOCTANE AIR DIFFUSION FLAME

Measurements were carried out to determine the effect on soot when ferrocene is added to a prevaporized isooctane/air diffusion flame. Data were obtained for operation of the flame above and below its smoke-point. Mie scattering was used to determine soot size, number density, and volume fraction with and without ferrocene. In addition, quartz microprobe sampling and gas chromatographic analysis were used to determine ferrocene's effect on soot precursor hydrocarbon and other species. The flame temperature was measured using a novel method based on infrared emission tomography. Ferrocene shortened the time for soot to first appear in the flame, and caused the formation of solid iron oxide particulates. It perturbed the particulate's size and number density in a complex manner in that increases and decreases of the latter were observed at early and late residence times, respectively. Ferrocene was very effective in and near the flame's terminus, thereby appearing to enhance soot burnout. On the whole, ferrocene did not significantly affect the soot precursor chemistry. An exception to this was the observed simultaneous decrease and increase of acetylene and molecular hydrogen mole fractions, respectively, which may be interpreted as an enhancement of acetylene oxidation. Solid effluent was collected above the flame and subjected to an Auger-type chemical analysis in order to look for coating of iron and/or its oxides by soot, which, if present, would support a catalytic mechanism for enhanced soot burnout with ferrocene seeding; the Auger data were not fully consistent with the aforesaid coating. Ferrocene did not affect flame temperature, which ruled out any thermally related explanation of its behavior in relation to soot suppression.