Characterization of Individual Soot Aggregates from Different Sources using Image Analysis

The elemental carbon core of combustion particles is covered with more or less volatile material, depending on the emission source, and these coatings could have a significant influence on the optical and hygroscopic nature of the soot particles. Detailed soot characteristics are therefore highly dependent on the formation conditions and on the combustion process and some intrinsic characteristics are different for soot of different sources. Although morphological studies on soot aggregates have a long and elaborate history, based mainly on simulations, the application of image analysis on individual soot particles has been limited. The purpose of this work is to detect whether there are significant differences in morphology between soot aggregates from different origins. By performing individual particle analysis, the morphology is measured on single particles and these particles are characterized as a function of their aerodynamic diameter. In this paper, a description of an irregular shape of aggregate is performed by applying the developed image analysis methodology to electron microscopical images. Some new parameters are defined and a method is established to calculate the number of primary particles in a soot aggregate produced by different sources. These provided a means to distinguish between different soot types and their corresponding production conditions.