Time-Resolved Soot Particulates in Diesel Spray Combustion
Experiments have been made to study the soot particulates formed at different stages of combustion of a simulated diesel spray by applying a newly developed laboratory combustor in which the following two essential characteristics of diesel spray combustion are reproduced: intermittency and autoignition. The combustor is designed so that the fuel is injected by using a diesel fuel injection system into a steadily flowing high temperature air stream resulting in autoignition and combustion. Soot particulates have been collected at different stages of combustion by applying an inert gas quenching technique. The mass concentration, diameter, number and carbon-to-hydrogen ratio of soot particulates, oxygen concentration and temperature in the flame as a function of the time from the start of fuel injection have been obtained. Mutagenic activity of the time-resolved soot particulates has been determined by using the bacterial mutagenesis test. Thus, some factors affecting time-resolved characteristics of soot particulates have been studied. Theoretical analysis is also made of the physical mechanism for soot particulates formation.
The results indicate that this new technique is a useful tool to obtain the time-resolved characteristics of soot particulates in diesel spray combustion. The mass concentration of soot particulates increases during the early stage of combustion and reaches a maximum after which it decreases to very low values approaching zero near the end of the combustion process. The diameter and carbon-to-hydrogen ratio of the soot particulates increase with time while their number decreases. The mutagenic activity shows a maximum as a function of time. The rates of formation and gasification of soot particulates increase with the increase in flame temperature. Adding alcohol, indolene and water to diesel fuel has a definite effect on reducing the soot particulates in the flame.
KeywordsDiesel Engine Combustion Chamber Equivalence Ratio Mutagenic Activity Soot Particulate
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