Potential of multiple injection strategies implementing the after shot and optimized with the design of experiments procedure to improve diesel engine emissions and performance

The substitution of the pilot-main injection schedule in the medium-high part-load zone of the NEDC region with a triple injection, featuring both pilot and after shots, has led to lower NOx and higher soot, while fuel consumption remains almost the same. In general, the EGR trade-off soot-NOx, bsfc-NOx, HC-NOx and CO-NOx curves do not change to any significant extent when an after shot is added to the pilot-main injection train. Reductions in the combustion noise, which depend on the changes in the pilot injection parameters that result from the design of experiments procedure, can also be obtained, as a consequence of the addition of the after-injection to the pilot-main injection schedule. Pilot-pilot-main-after strategies guarantee improved NOx engine-out emissions and bsfc-NOx EGR trade-off curve at medium loads and speeds, compared to both pilot-pilot-main and pilot-main-after strategies, and allow combustion noise to be diminished significantly.