Experimental analysis of emission reduction by the split injection strategy using close post injection with a double-row nozzle in heavy EGR conditions

As EURO-6 regulations will be enforced in 2014, simultaneous reduction of NO _x and PM emissions becomes an important issue in recent diesel engine research. New combustion concepts, such as LTDC and pHCCI, have been introduced to overcome the NO _x and PM trade-off relation. However, these novel combustion concepts are usually implemented with a high EGR rate and by advancing the main injection timing which cause high CO and THC emissions along with poor fuel consumption due to low combustion efficiency. Therefore, the split injection strategy, which was consisted of applying post injection close to the main injection, was carried out in this experiment. Specifically, two different nozzles - a 7-hole conventional nozzle and a 12-hole double-row nozzle - were evaluated to determine the effects of nozzle configurations on engine-out emissions. The result shows that CO emission was reduced by the close post injection strategy regardless of the nozzle configuration. However, THC and PM emissions were reduced only when the 12-hole double-row nozzle was used. Thus, the use of close post injection with the 12-hole double-row nozzle could increase the combustion efficiency in heavy EGR conditions.