Optical Soot Particle Size And Number Density Measurements In A Direct Injection Diesel Engine

Abstract

Abstract Abstract–Optical measurements of soot particle size and number density have been made in-situ in a direct injection diesel engine using a light scattering and extinction measurement technique. Simultaneously, the radiation from the soot particles was measured and used to estimate the thickness of the soot cloud and temperature of the soot particles. The measurement was taken at a fixed location near the center of the spray plume. Soot particle size was found to increase slightly during the combustion event reaching a peak diameter of approximately 40 nm. As the injection process and combustion ended, the soot particle size dropped rapidly to below 20 nm before the signal became too small to measure. Soot volume fraction reached a maximum near 7 x 10-5. The soot cloud was not only dense but thick, indicating that the soot was not confined to a thin reaction layer but rather filled more than half of the path length from the piston to the cylinder head. Rates of soot formation and oxidation appeared faster at the higher temperatures and pressures of the engine in comparison to laboratory diffusion flames.