Probing soot formation, chemical and physical evolution, and oxidation: A review of in situ diagnostic techniques and needs

Soot is responsible for notoriously detrimental effects on human health, air quality, and global and regional climate. Controlling soot emissions to the atmosphere will require overcoming large gaps in the understanding of soot formation and physical and chemical evolution during combustion. These gaps in understanding are largely attributable to the complexity of the chemical and physical system combined with a paucity of diagnostic techniques available for probing soot non-invasively and under a wide range of combustion conditions. This review briefly summarizes the chemistry of soot formation and evolution during combustion and describes diagnostic tools that are available to make these measurements. Despite the availability and value of a host of ex situ particle diagnostic techniques, because of space limitations, this review is restricted to a discussion of in situ diagnostic methods. The review concludes with a brief discussion of needs for new diagnostic tools to probe soot chemistry.