DROP-SIZE MEASUREMENT TECHNIQUES APPLIED TO GASOLINE SPRAYS

Abstract

Combustion processes involved in internal combustion engines greatly depend on the characteristics of the spray. This study is focused on the comparison of three different techniques used for spray drop sizing. Laser diffraction (LDG), phase Doppler anemometry (PDA) and Image Analysis (IMA) have been used to characterize gasoline sprays produced by gasoline injectors of a direct injection type. Whereas studies comparing drop sizing techniques found in the literature are mainly dealing with steady flows, attention is paid here to the unsteady nature of the spray. The differences in the measurement volumes of the different techniques are also considered. As these diagnostics do not measure exactly the same kind of distribution, both PDA and IMA measurements were converted to spatial-averaged volume-weighted drop size distributions to be compared to LDG. The Sauter Mean Diameter D32 and the mean diameter D43 are used to characterize the spray for different time and position of the measurement volume in the spray. The comparison between the three techniques shows a good agreement. Greatest mean diameters are found on the leading edge of the spray and on the side of the spray facing stagnant air, so where the conditions are favourable to a fast evaporation of the smallest droplets. Velocity measurements done by PDA and drop shape morphology characterization are also discussed. Paper ID ILASS08-7-7