Evaluation of the effect of engine, load and turbocharger parameters on transient emissions of diesel engine

The vital issue of exhaust emissions during transient operation of diesel engines has been studied so far mainly on an experimental rather than simulation basis, owing to the very high computational times required for the analysis of each transient cycle. The study of transient emissions, however, is extremely important to manufacturers, since newly produced engines must meet the stringent regulations concerning exhaust emissions levels. In the present work, a comprehensive two-zone transient diesel combustion model is used for a preliminary evaluation of the effect of various parameters on nitric oxide (NO) and soot emissions during transient operation after load changes. The parameters are divided into three categories according to the specific sub-system examined, i.e. engine, load and turbocharger. Demonstrative diagrams are provided for the development of NO and soot emissions during the transient event, which depict the effect of each parameter considered. Moreover, the peculiarities of each case are discussed mainly in relation to turbocharger lag effects. For the current engine-load configuration, it is found that exhaust valve opening timing and cylinder wall insulation affect considerably NO and soot emissions. Additionally, load characteristics as well as turbocharger (T/C) mass moment of inertia play an important role on the development of transient NO and soot emissions.