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Due to the higher combustion efficiency and fewer exhaust emissions in comparison with other diesel combustion strategies, RCCI combustion attracted lots of attention. Using two fuels with different reactivities lead to lower fuel consumption and considerably less NOx and PM emissions. An investigation has been carried out in order to examine the simultaneous effects of diesel injection pressure and single injection timing on the emissions formation and engine performance in a heavy duty single-cylinder butanol-diesel reactivity controlled compression ignition (RCCI) diesel engine. A reduced chemical n-heptane-n-butanol-PAH mechanism which consists of 76 species and 349 reactions has been used to simulate the combustion process of the dual-fuel diesel engine.

Exhaust Gas Recirculation (EGR) is an effective pre-treatment technique, which has been widely used to decrease the amount of the oxides of nitrogen (NOx) emission from diesel engines. However, the use of high EGR rates leads to the reduction in oxygen availability in the burning regions of the combustion chamber which impairs the soot oxidation process. Consequently, higher soot generated by EGR leads to long-term usage problems inside the engines such as higher carbon deposits, lubricating oil degradation and enhanced engine wear. In this study, CFD modeling has been carried out to analyze the effects of high EGR rates in conjunction with optimum multiple injection strategies. A heavy-duty DI Diesel engine has been modeled to study the engine performance and emissions with various EGR rates (from 0% to 40%). The selected operating points have been achieved with the same injection profile including a main and post injection for all considered cases.

Effects of included spray angle with different injection strategies on combustion characteristics, performance and amount of pollutant emission have been computationally investigated in a common rail heavy-duty DI diesel engine. The CFD model was firstly validated with experimental data achieved from a Caterpillar 3401 diesel engine for a conventional part load condition at 1600 rev/min. Three different included spray angles (α = 145°, 105°, 90°) were studied in comparison with the traditional spray injection angle (α = 125°). The results show that spray targeting is very effective for controlling the in-cylinder mixture distributions especially when it accompanied with various injection strategies. It was found that 105° spray cone angle along with an optimized split pre- and post-Top Dead Center (TDC) injection strategy could significantly reduce NOx and soot emissions without much penalty of the fuel consumption, as compared to the wide spray angle.

The mechanism of NOx and soot reduction using different pilot and multiple injection strategies has been computationally studied in a heavy duty DI Diesel engine. A designed set of advanced injection schemes with various variables and exhaust gas recirculation rate (up to 10%) have been analyzed. The CFD model was firstly calibrated against experimental data for a part load operation at 1600 rpm. The computational models used were found to predict the correct trends obtained in the experiment. The study demonstrated the potential and explained the mechanism of the combination of EGR and multiple injection to reduce both soot and NOx emissions together with improved fuel economy.