Characterization of Soot Particles Produced from the Combustion of Hydrocarbon Fuels in a Shock-Tube

Abstract

Soot as a byproduct of hydrocarbon combustion has been studied extensively because of its contribution to pollution, on the order of 12-24 Teragrams annually[1]. The composition and morphology of highly agglomerated soot particles is very much dependent on the combustion conditions and may change significantly during atmospheric aging, which occurs through condensation of low-volatile gaseous species (e.g. sulfuric acid and organics), coagulation with existing aerosols, and oxidation by OH and O3[2]. Therefore, better understanding of soot’s fundamental characteristics and formation pathways is critical to minimizing its adverse impact on the environment and human health. An experimental technique has been established for analyzing soot generated in a shock tube using a suite of instruments with particular emphasis on soot yield, particle composition, morphology, optical properties and mass fraction of elemental carbon (EC). The shock tube is useful for creating precise and repeatable temperature and pressure conditions for combusting test mixtures. This precise and individual control over the test conditions allows for studying the effects small temperature and pressure changes have on fundamental soot properties. In the present study, soot is examined from its initiation, through its growth, and at various time increments. The following describes the equipment and techniques used to produce and analyze soot from the combustion of high-equivalence ratio propane and oxygen mixtures, and the results of the analysis are presented.