Characterization of Local Fuel Concentrations and Internal Dynamics in D.I. Diesel Sprays

The object of this paper is to present a methodology to characterize the distribution of fuel concentration into Diesel sprays and to use it to analyze the internal dynamics and atomization/coalescence mechanisms. This methodology is based on a combination of data obtained with PDA and high speed shadowgraphy on the basis of the light extinction principle. The results of fuel concentration distribution obtained at different instants of the injection show a two zones structure. From the nozzle to approximately 70% of the tip position, the evolution of radial fuel concentration distribution is similar to a gaseous steady jet. The unsteady nature of the Diesel spray appears on the front region where an accumulation of droplets occurs, mainly in the spray axis.