X-RAY RADIOGRAPHY MEASUREMENTS OF DIESEL SPRAY STRUCTURE AT ENGINE-LIKE AMBIENT DENSITY

Abstract

X-ray radiography has been used to examine the dependence of the near-nozzle fuel distribution of diesel sprays on injection pressure and ambient density. Measurements of sprays from two nozzles with different geometries, one extensively hydroground and the other largely non-hydroground, have been obtained to show how nozzles of different geometries respond to changes in ambient density and rail pressure. The spray penetration near the nozzle demonstrates little dependence on ambient density but a strong dependence on rail pressure. Comparison of these results with standard correlations in the literature show that, in the near-nozzle region examined in this study, the penetration is expected to show little dependence on ambient density. The spray width becomes much larger for both nozzles as the ambient density increases. Rescaling the axial position by the square root of the density ratio between the fuel and the ambient gas accounts for the trends in spray width with ambient density for both nozzles. The radiography data can also be examined to determine the relative trends in the steady-state, mass-averaged axial velocity of the spray. The velocity decays more rapidly with axial distance as the ambient density increases. Rescaling the axial position also accounts for the trend of velocitymore » decay with ambient pressure.« less