Fuel pressure oscillations impact on emissions - when applying multiple injections on a heavy-duty Diesel engine

Konferensbidrag (offentliggjort, men ej förlagsutgivet), 2005

A common goal for Diesel engine development is to reduce NOx and soot emissions while maintaining low fuel consumption. This can be achieved in several ways, one of which is to use advanced injection systems and injection strategies. In this study a common rail injection system was used with a heavy-duty single cylinder research engine. When applying high injection pressures and multiple injections, pressure waves and pressure drops (caused by the injections) in the injection system are generated, and their effects on soot emissions are analyzed here. Since high fuel pressure has a strong beneficial effect on soot emissions it is desirable to keep it as high as possible. Multiple early (pilot) injections do not reduce the fuel pressure significantly while late (post) injections, after and in interaction with a main injection; can result in very low injection pressures. Pressure waves created by the injector closing can be used to generate higher pressure in later injections during the same engine cycle