Optical diagnostics of temporal and spatial evolution of a reacting Diesel fuel jet

Laser Doppler anemometry, spectral extinction-absorption, and flame chemiluminescence measurements were carried out to characterize the fluid flow and to analyze the temporal and spatial distribution of liquid, vapor and some pollutant species in an optically accessed high swirl combustion chamber. Extinction-absorption measurements from UV to visible have shown that the spray, strongly distorted, is mixed downstream by the high swirling flow and the vapor region expands rapidly from the tip of the jet toward the chamber walls. The entrainment of hot air into the jet accelerates the vaporization process and the strong swirling flow transports the vapor around the chamber. The OH emission, indicating the spatial location of autoignition, occurs at the same crank angle as that of the minimum of the heat release rate, and in the vapor region far from the tip of the liquid jet. The first appearance of soot occurs later across a wide portion of the leading part of the jet located between the tip of the jet and the OH emission zone.