The Computed Structure of a Combusting Transient Jet Under Diesel Conditions

Numerical computations of combusting transient jets are performed under diesel-like conditions. Discussions of the structure of such jets are presented from global and detailed points of view. From a global point of view, we show that the computed flame heights agree with deductions from theory and that integrated soot mass and heat release rates are consistent with expected trends. We present results of several paramaters which characterise the details of the jet structure. These are fuel mass fractions, temperature, heat release rates, soot and NO. Some of these parameters are compared with the structure of a combusting diesel spray as deduced from measurements and reported in the literature. The heat release rate contours show that the region of chemical reactions is confined to a thin sheet as expected for a diffusion flame. The soot contour plots appear to agree qualitatively with the experimental observations. The NO contours show that NO is formed in regions of high temperature as expected. The penetration of the combusting gas jet is compared with that of a non-combusting gas jet under similar injection and ambient conditions in order to study the effect of combustion. Different criteria may be used to define penetrat)ion of jets. The results of the comparison of penetration of combusting with non-combusting jets depends on the criteria selected.