Time resolved soot particulates in autoignited intermittent spray flames

Abstract

An attempt has been made to study soot particulates formation at different stages of combustion of simulated diesel sprays by using a new laboratory combustor in which the following two essential characteristics of diesel spray 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 of soot particulates, C/H ratio, the microscopic diameter of each particle, the flame temperature and the oxygen concentration in the flame have been obtained. The results indicate that this new technique is a useful tool to obtain the time resolved characteristics of soot particulates in intermittent spray flames. The mass concentration of soot particulates increases during the early stages of combustion, reaches a maximum, after which it decreases near the end of the combustion process. The diameter and C/H ratio of the soot particulates increase with time while their number decreases. The mass concentration rates of formation and oxidation of soot particulates increase with the increase in flame temperature. Adding methanol to diesel fuel has a definite effect on reducing the soot particulates in the flame.