Potential of Premixed Combustion With Flash Late Injection On a Heavy-Duty Diesel Engine

Among the various homogeneous combustion concepts, the “late injection strategy” shows potential to put NOx and particulate emissions within the Euro 5 box at low loads. However, the corresponding retarded injection timings lead to increased fuel consumption. This article gives an overview of techniques which improve fuel consumption by enabling the combustion to be phased closer to top dead center. Primarily, injection duration can be shorten using an adapted Common Rail and high flow tips. Secondly, the ignition delay can be increased through lowered compression ratio or retarded inlet valve closing. Lastly, the mixing of air and fuel can be enhanced as a result of additional nozzle tip holes, optimized A/F and swirl level.

The end result for this combination of improvements is a defined combustion system that yields the same NOx/BSFC trade-off as conventional combustion at low loads, but with very low soot emissions. This could be advantageous in conjunction with diesel particulate filter applications which do not self-regenerate at low loads.