Optical Investigation of the Effect of Fuel Jet Wall Impact Position on Soot Emissions in a Single Cylinder Common Rail Direct Injection Diesel Engine

This study is dealing with optical experiments in a common rail DI Diesel small-bore automotive engine. Its purpose is to investigate the influence on soot emissions of the location of the point of impact of the fuel jet on the piston bowl walls. The experiments are carried out in a single cylinder, 4 valves Diesel engine equipped with a common rail injector and a bowl shaped piston. A classic extended piston with piston-crown quartz window provides a first optical access to the combustion chamber. A transparent quartz cylinder also provides a second access to the chamber. Liquid and vapor phases of the fuel were visualized using Exciplex laser induced fluorescence while combustion and soot images were recorded with an intensified CCD camera by direct light emission monitoring. Soot emissions were also analyzed in the exhaust pipe with a standard smoke meter. Experiments carried out for several vertical positions of the injector show that smoke emissions are strongly affected by the fuel jets point of impact in the piston bowl. The analysis of the fuel and combustion visualizations presented in this article shows that this phenomenon is related to distribution of the vapor fuel in the combustion chamber between squish area and piston bowl.