Combustion Optimization and In-Cylinder NOx and PM Reduction by Using EGR and Split Injection Techniques

Nowadays, the major most challenge in the diesel engine is the oxides of nitrogen (NOx) and particulate matter (PM) trade-off, with minimal reduction in Power and BSFC. Modern day engines also rely on expensive after-treatment devices, which may decrease the performance and increase the BSFC. In this paper, combustion optimization and in-cylinder emission control by introducing the Split injection technique along with EGR is carried out by 1-D (GT- POWER) simulation. Experiments were conducted on a 3.5 kW Single-cylinder naturally aspirated CRDI engine at the different load conditions. The Simulation model incorporates detailed pressure (Burn rate) analysis for different cases and various aspects of ignition delay, premixed and mixing controlled combustion rate, the injection rate affecting oxides of nitrogen and particulate matter. The predictive combustion model (DI-PULSE) has been developed for the calibration of an engine under multiple injections and the detailed injection rates with EGR rates. Split injection with higher fuel quantity injected in the 1^st pulse, helped to significantly reduce PM emissions. This reduction is due to the restraint in the premixed phase of the 2^nd pulse combustion. Split injections technique is helpful to effectively reduce NOx as well as PM emissions, as compared to increasing dilution rates and injection pressure (700 to 1000 bar) using Cooled EGR and retarding the injection timing. It is noted that for a case of 60(10)40 retarded to injection timings of 20°bTDC, 18°bTDC and 16°bTDC from 23°bTDC has resulted in 31.32% reductions in soot emissions and 38.23% reduction in NOx emissions. Results showing that the simultaneous reduction in NOx emissions and PM emissions is possible with an optimized combination of Split injections & the EGR, under different load conditions and the experimental values are almost matching with the 1-D simulation.