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The use of early and late injection diesel Low Temperature Combustion (LTC) strategies in the low to mid load operating range are becoming increasingly popular options for production diesel engines to reduce oxides of nitrogen (NOx) and particulate matter (PM) emissions. Although opacity-based filter smoke number (FSN) PM measurements in these operating conditions have been reduced to near zero for many instruments (which are standard and very useful in most engine combustion research laboratories), significant changes can still be seen in the particle size and number measurements (such as a 2.5 - 4.5 fold variation in total particle number concentration, depending on engine operating condition). The current work presents particle size distribution measurements from early to late injection timing LTC, varying the start of injection (SOI) by three crank angle degrees (CAD) per data point, for two exhaust gas recirculation (EGR) rates, 45% and 50%.

The scope of present study is the analysis of the potential of the highly premixed combustion concept for pollutant control in a HD Diesel engine. Two different approaches to attain this advanced combustion concept are presented in this paper. A narrow angle nozzle configuration is investigated with two different adapted piston bowl geometries. Parametrical tests were performed in a HD single cylinder engine with the aim of appreciating advantages and limitations of these strategies. In each case, results are compared with equivalent conventional single injection strategy. This analysis is focused on NOx-soot emissions and also on engine performance.