Physical and chemical properties of combustion generated soot

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Abstract
The physical and chemical properties of soot particles generated by an acetylene-air, premixed flame stabilized on a well-characterized, water cooled, porous, flat flame burner are analyzed over a wide range of operating parameters. To characterize the soot generated in combustion systems as a function of combustion parameters, the temperature, velocity, and burner heat losses are measured over the stable range of burner operation. The flat flame achieved with this burner is uniform in temperature over the entire flame disk within a few percent of the maximum flame temperature. In separate experiments, hot film indicates that the cold flow gas velocity assessment is uniform within approximately 10% over the entire porous disk. Particle size distribution measurements by an Electrical Aerosol Size Analyzer indicate two submicron modes, one centered at approximately 80 A and another which occurs only in luminous flames at high equivalence ratios at approximately 500 A. The chemical composition of soot collected on different filter media is determined by X-ray photoelectron spectroscopy (ESCA) and X-ray fluorescent techniques. Two oxygenated species, as yet unidentified but here designated as O/sub I/ and O/sub II/, adsorbed on carbon particles, are recognized. The ratios of atomic concentrations O/C and O/sub I//O/sub II/ aremore » determined as a function of flame parameters. These ratios decrease as the flame equivalence ratio increases but remain constant at equivalence ratios greater than 2.0. The rate of heterogeneous oxidation of SO/sub 2/ in a plume containing combustion-generated carbon particles is also studied. Water vapor and oxygen concentrations along with particle size and concentration are found to have controlling influences on the oxidation of SO/sub 2/. An analysis is presented in which integrated forms of species, momentum, and energy equations are solved to predict concentration histories along the trajectory of a reacting plume of combustion products. « less

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