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The possible NOx and soot limits that a conventional diesel engine could meet without the assistance of aftertreatment system were investigated on an engineering level. A methodology combining both experiment and numerical simulation was used to evaluate favorable and unfavorable effects of various in-cylinder strategies quantitatively. These strategies or factors include combustion chamber geometry, fuel injection strategy, exhaust gas recirculation (EGR), intake valve close (IVC) timing, and turbocharger. Interactions among these strategies were paid special attention. Two steps to achieve as low as possible emissions were proposed based on analysis of these strategies. The first step would shift the NOx-soot trade-off curve closer to low emission regions via optimization of injection strategy, combustion chamber geometry, IVC, and turbocharger. As a result, NOx and soot could be simultaneously reduced by approximately 14% and 62% respectively.

Selective catalytic reduction (SCR) has become one of the primary technologies to reduce internal combustion engine (ICE) emission. The installation angle of urea injector plays an important role during the SCR process. The urea injector is often vertically mounted to the exhaust pipe for on road heavy duty truck because of its good performance and general packaging convenience, and this type of installation has been the focus of previous research. However, due to certain packaging constraints or responsiveness considerations, the injector is installed with an inclined acute angle to the exhaust pipe under some circumstance.