EGR Combined with Particulate Trap for the Reduction of Oxides of Nitrogen and Smoke Emissions in a Small DI Diesel Engine

Abstract

The increase in motorized transport has led to a simultaneous increase in oxides of nitrogen (NO_x) and smoke emissions. Though a wide range of reduction strategies have been explored, exhaust gas recirculation (EGR) combined with particulate trap technology has proved to be a more effective and economic choice. The effect of EGR on engine performance and emissions was studied on a single-cylinder, direct injection (DI) diesel engine run at a constant speed of 1500 rpm at various loads. The present work aims at studying the effect of hot and cool EGR on the formation of NO_x. The baseline readings were determined from the experimental results obtained from an engine without EGR run at various operating conditions. This would definitely form a healthy means of evaluation of the effect of EGR on engine performance and emissions. Comparison of the findings of hot and cool EGR at full load conditions corresponds to a proportion of 15% which amounts to be the maximum allowable one, has revealed the effectiveness of cool EGR on the reduction of NO_x and smoke emissions as compared to hot EGR. Hence, a suitable particulate trap with a high trapping efficiency and cost effectiveness is strongly desired before the EGR cooler to reduce the smoke emissions to meet the emission standards. The present study uses a particulate trap with a substrate made of clay material, made into spheres coated with copper and zinc oxide catalyst material. Effective reduction in NO_x and smoke emissions by 63% and 42% respectively have been observed by the combination of EGR and the particulate trap. A simultaneous increase in brake specific fuel consumption by 10% as compared to baseline operation has also been observed.