The effects of molecular structure on soot formation,I. Soot thresholds in premixed flames

Soot thresholds have been measured in atmospheric pressure, laminar premixed flames of 55 pure hydrocarbons. Soot threshold data as a function of fuel structure parameters are presented in four forms; threshold soot indices, TSIs; equivalence ratios assuming combustion to CO₂ and H₂O, f_c; equivalence ratios assuming combustion to CO and H₂O, ψ_c; and carbon to oxygen atom ratios (C/O)_c. The relative TSI scale allows comparison with previous measurements and removes apparatus-dependent variations in the data. Data were obtained for more than 40 previously unstudied fuels, including 15 alkanes, 14 alkenes, 7 alkynes, and 15 aromatics. Comparison with similar data in the literature gave good agreement. Suggested TSI values are given for all fuels which have been reported.