Kinetic Aspects of Diesel Soot Coagulation

In order to control the formation of particulate carbon during diesel combustion it is important to understand the mechanisms and kinetics of formation. This report addresses several aspects of diesel soot formation, focusing primarily on the influence of coagulation processes on the spherule size and kinetics of formation. Our previously developed nucleation/depletion model for the spherule size of particulate carbon has been modified to take account of coalescent coagulation during the early stages of diesel soot formation. Such coagulation should not increase spherule size by more than a factor of two or three. Simple coagulation theory has been employed to calculate the time constants for coalescent and chain-forming coagulation. Kinetics aspects of other processes --nucleation, particle fusion, dehydrogenation, depletion of precursors, and oxidation --have also been assessed.