A quantitative study of diesel fuel injection was conducted to investigate minute differences in spray plume development from several unique injector tips. In this study, a set of six eight-hole injector tips was assessed to evaluate distinguishable spray characteristics. The tips have known variability in soot and NOx data during in-engine testing. A spray fixture was constructed with a cam-pressurized electronic unit injector and a 5.1L, nitrogen-pressurized spray chamber. Injection conditions such as injection timing and duration were experimentally controlled to replicate actual engine load conditions. A copper-vapor laser illuminated the fuel spray, and a high-speed digital camera was timed to capture the injection events.
Digital analysis of the spray images produced quantified penetration length, cone angle, and two-dimensional area data as a function of crank angle. The first five observed spray images (up to a spray radius of approximately 6 cm) of each injection event are presented.
Initial qualitative analysis of the spray images indicated clear and repeatable asymmetries, as well as plume development differences between the injector tips. These observations suggest that early penetration length measurements may be indicative of emissions trends. It is assumed that variations in spray shapes can be correlated to NOx and soot data. The level of these differences, however, is minute, suggesting that detailed characterization strategies must be implemented to detect the spray patterns that are most influential to engine emissions.