Investigation of the effect of boost pressure and exhaust gas recirculation rate on nitrogen oxide and particulate matter emissions in diesel engines

In recent years, due to the growing problem of environmental pollution and climate change internal combustion engine stroke volume size has been reduced. The use of down-sized engines provides benefit for reducing emissions and fuel consumption especially at the inner city driving conditions. However, when the engine demands additional power, utilizing a turbocharging system is required. This study is a joint work of Istituto Motori CNR with Automotive Laboratory of Mechanical Engineering Faculty of Istanbul Technical University (ITU) and the objective of this study was devoted to increase the understanding of various engine operating conditions on emissions, especially at low load. The trade-off between Nitrogen Oxide (NO_x) and Particulate Matter (PM) emissions in a Diesel engine has been examined depending on turbocharging rates and the rate of Exhaust Gas Recirculation (EGR) applied. Experimental and numerical investigations were carried out to study the optimum conditions for providing lowest emission rates in a Diesel engine. Within the context of this study, it is aimed to develop a multi-dimensional cycle analysis model which is capable of simulating the cases in engine combustion and expansion stroke. The change of two pollutant components with different intake boost pressures was analyzed by parametric analysis. Moreover, the effect of EGR systems used in Diesel engines on emissions regarding the EGR rate and the temperature were also analyzed. EGR application reduces NO_x emissions as expected while increasing PM. But further increase in EGR rate reduces the increase of PM emissions. Increasing the intake boost pressure provides positive effect on PM emissions.