Abstract
KEYWORDS-Diesel engine, Common rail system, SCR system, CO2, NOx
ABSTRACT -
The further improvement of diesel engine combustion and aftertreatment systems in terms of CO2 and NOx emission reduction is an important challenge and the subject in this paper. As for the diesel engine combustion, the technical target is to achieve further thermal efficiency especially in the case of a downsized engine. Structurally the smaller the bore diameter is, the lower the thermal efficiency is, due to the cooling losses to the combustion chamber wall. New FIE solutions can break the trade-off between combustion speed and cooling losses. For example, at low load, controlled spatial and temporal spray by the future fuel injection technologies can provide appropriate air and fuel mixture and hold combustion zone away from the wall. The engine experimental results show a remarkable improvement of thermal efficiency thus fuel consumption.
As for the aftertreatment and urea SCR systems, the improvement of NOx reduction at low exhaust gas temperatures is the upcoming technical theme to develop. The above mentioned thermal efficiency improvement, on the other hand, causes the drawback of slower SCR catalyst activation. To face this issue, the brand new concept “Direct Dosing Injection System” is applied. This extremely compact layout without mixer can reduce heat losses towards the ambient air through the exhaust line pipes, allowing faster catalyst activation. Consequently, while securing lower NOx emissions, this concept can cut down extra fuel consumption required for exhaust gas heat up. Moreover, it can increase engine power by reducing exhaust pressure losses. Finally, this compact layout can enhance the degree of freedom in the engine-aftertreatment system packaging design.