Effects Of Flow Properties On Soot Formation And Oxidation Rates In Flame Environments

Soot and flame structure were measured in a variety of round laminar premixed and nonpremixed (diffusion) jet flames fueled with hydrocarbons to study the properties of soot formation (primary soot particle nucleation and surface growth) and surface oxidation. The following properties were measured along the axes of the flames: soot concentrations by laser extinction, soot temperatures by multiline emission, soot structure by thermophoretic sampling and electron microscopy, concentrations of major gas species by sampling and gas chromatography, concentrations of some radical species (H, OH and O) by atomic absorption and flow velocities by laser velocimetry. These measurements were analyzed to yield local primary soot particle surface growth and surface oxidation rates, as well as primary soot particle nucleation rates. It was found that local soot surface growth rates could be correlated effectively using Hydrogen-Abstraction/Carbon-Addition (HACA) soot surface growth rate mechanisms in the literature; that local soot surface oxidation rates could be correlated effectively using OH/O2 mechanisms in the literature; and that local soot particle nucleation rates (observable using electron microscopy techniques) could be correlated by assuming that the rate of development of large PAH molecules by the HACA mechanism controlled nucleation rates. These results were found considering a broad range of conditions in laminar flame environments: premixed and diffusion flames, various hydrocarbon fuel types (methane, acetylene, ethylene, propylene, propane and benzene), gas temperatures of 1500-2350 K and pressures of 10-100 kPa