Appliance of High EGR Rates With a Short and Long Route EGR System on a Heavy Duty Diesel Engine

The goal of this work was to investigate the possibilities of applying high EGR rates with low NO_x and PM emission levels on a two-stage turbocharged 12 liter heavy duty diesel engine. The EGR is applied by using a long and short route EGR system. For the ESC operating points A25 and C100 EGR is applied, such that the NO_x emission is 0.5 g/kWh. Lowest PM level and BSFC are achieved when long route EGR is applied in A25 and short route is applied in C100. Increasing the fuel line pressure is an effective way to reduce PM at high EGR rate engine running conditions. At a fuel line pressure of 2400 bar PM emission are 0.06 g/kWh for A25 and 0.54 g/kWh for C100. At C100 the PM reduction coincides with also a significant fuel consumption improvement. Retarding the injection timing at C100 can improve the PM emission further to a level of 0.13 g/kWh at the expense of an increase in BSFC. From the results it can be concluded that a minimal engine out NO_x emission level of 0.75 g/kWh is required for meeting Euro-6/US2010 emission levels with additionally installed NO_x and PM aftertreatment systems.