Two Dimensional Measurements of Soot Size and Concentration in Diesel Flames by Laser Based Optical Methods

Soot particle size, particle concentration and volume fraction were measured by laser based methods in optically dense, highly turbulent combusting diesel sprays under engine-like conditions. Experiments were done in the Chalmers High Pressure, High Temperature spray rig under isobaric conditions and combusting commercial diesel fuel. Laser Induced Incandescence (LII), Elastic Scattering and Light Extinction were combined quasi-simultaneously to quantify particle characteristics spatially resolved in the middle plane of a combusting spray at two instants after the start of combustion. The influence that fuel injection pressure, gas temperature and gas pressure exert on particle size, particle concentration and volume fraction were studied. Probability density functions of particle size and two-dimensional images of particle diameter, particle concentration and volume fraction concerning instantaneous single-shot cases and average measurements are presented. High injection pressure led to a reduction in the mean particle size, total number of particles and total amount of soot compared to a low injection pressure. Higher gas pressure resulted in larger amount of soot and larger soot particle size, with higher gas temperature having similar effects.