A theoretical investigation of two possible modifications to reduce pollutant emissions from a diesel engine

Abstract

The goal of the study is to present and to evaluate theoretically two strategies for reducing simultaneously both particulate and NOx emission from a compression-ignited, direct injection engine. The emission reduction strategies to be considered here include auxiliary exhaust gas injection (AEGI) and a combination of exhaust gas recirculation (EGR) and AEGI. The auxiliary gas injection (AGI) process consists of the injection of a gas directly into the combustion chamber of a diesel engine during the combustion stroke to enhance fluid mixing. Increased mixing during the combustion process can lower the emission of both soot and NOx. AEGI is a process whereby exhaust gas is the injected gas used in AGI. To predict the effect of AEGI on diesel engine combustion and emission, a gas injection model was developed and used with a multidimensional simulation computer code, KIVA. The program is used to evaluate the combined effect of AEGI and EGR on pollutant emissions in a Caterpillar diesel engine. The results demonstrate that the injection timing of AEGI affects soot emissions quite differently to NOx emissions. A combination of EGR and AEGI is found to be more effective than AEGI alone for the maximum simultaneous reduction of soot and NOx emissions. It is predicted that the EGR and AEGI combination can reduce both particulate and NOx emissions by almost 50 per cent over baseline.