Abstract
To understand the spray characteristics that are related to the characteristics of emissions and the combustion of direct injection engines, the planar image technique was applied to measure the distribution of droplet size. This technique was based on the principles of laser-induced fluorescence (LIF) and the Mie scattering of droplets in the spray. We decided to apply the LIF and Mie scattering intensity indices for unleaded gasoline to this technique with a droplet generator. The fluorescence and scattering signals were imaged simultaneously by an optical system composed of a doubling prism, optical filters and an ICCD camera. Relative Sauter mean diameter distributions according to space and time were obtained by calculating the ratio between two light intensities, and the distributions were quantified with a laser diffraction particle analyser. Experimental results have shown that the characteristics of the gasoline direct injection injector varied with injection pressure.