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

The goal of the study is to present and to evaluate theoretically two strategies for reducing simultaneously both particulate and NO_x 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 NO_x. 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 NO_x emissions. A combination of EGR and AEGI is found to be more effective than AEGI alone for the maximum simultaneous reduction of soot and NO_x emissions. It is predicted that the EGR and AEGI combination can reduce both particulate and NO_x emissions by almost 50 per cent over baseline.