In-Cylinder Penetration and Break-Up of Diesel Sprays Using a Common-Rail Injection System

As part of an ongoing investigation, the influence of in-cylinder charge density, and injector nozzle geometry on the behavior of diesel sprays were examined using high-speed imaging. Both liquid and vapor penetration profiles were investigated in operating conditions representative of a modern turbocharged after-cooled HSDI diesel engine. These conditions were achieved in an optical rapid compression machine fitted with a common-rail fuel injection system. Differences in spray liquid and vapor penetrations were observed for different nozzle geometries and in-cylinder conditions over a range of injection fuelling representative of those in a typical engine map. Investigation into the differences in spray structure formed by multi-hole and single-hole injections were also undertaken. The results of the spray penetration profiles from the experiments were compared to empirical correlations in the literature and differences observed were attributed to flow structures within the nozzle, which are not taken into account by these correlations.