Effect of the oxidation-induced fragmentation of primary particles on soot oxidation reactivity

Experiments were performed on a CH4 lean premixed flame to better understand the effect of the oxidation-induced fragmentation of primary particles on soot oxidation reactivity. An aerosol generator was used to homogeneously disperse diesel soot into the flame. Because minimal soot was formed in this flame itself, the information about diesel soot fragmentation was readily obtained. The thermophoretic and probe sampling techniques were used to obtain soot particles at various heights above the burner. The particle size distribution, oxidation reactivity, nanostructure and carbon chemical state of each sample were characterized. The soot reactivity was evaluated in terms of activation energy. The results indicate a higher extent of aggregate fragmentation occurs at moderate soot burnout percentages and that the internal structure in soot is not destroyed during aggregate fragmentation. At higher soot burnout percentages, the internal burning produces more primary particle fragmentation, so that the soot particles exhibit an increase in fringe tortuosity and decreases in fringe length and sp(2)/sp(3) hybridization ratio. These variations in physicochemical properties increase the oxidation reactivity of the soot particles. (c) 2022 The Combustion Institute. Published by Elsevier Inc. All rights reserved.

Automated summary

This study investigates the effect of oxidation-induced fragmentation on the oxidation reactivity of diesel soot in a CH4 lean premixed flame. The results show that more particle fragmentation occurs during soot burnout, and the internal combustion leads to variations in physicochemical properties, resulting in increased oxidation reactivity of the soot particles.