The Structure Analysis of Evaporative Diesel Spray

This paper analyzes heterogeneous distribution of branch-like structure at downstream region of the diesel spray. The liquid and vapor phase of the spray are obtained by a 35mm still camera and CCD camera in order to investigate spray structure of evaporative diesel spray. The many previous studies about diesel spray structure have yet stayed in the analyses of 2-D structure, and there is little information which is concerned with 3-D structure analysis of evaporative spray. The heterogeneous distribution of droplets in inner spray affects the mixture formation of diesel spray, and the combustion characteristics of the diesel engines. In this study, the laser beam of 2-D plane was used in order to investigate 3-D structure of evaporative spray. The incident laser beam was offset on central axis of the spray. From the analysis of images taken by offset of the laser beam, we examine formation mechanism of heterogeneous distribution of the diesel spray by vortex flow at the downstream of the spray. The images of liquid and vapor phase of free spray are simultaneously taken by exciplex fluorescence method. As a result, the branch-like structure consisted of heterogeneous distribution of the droplets forms high concentration of vapor phase at the periphery of droplets and the region of the spray tip.