Effects of low pressure exhaust gas recirculation on regulated and unregulated gaseous emissions during NEDC in a light-duty diesel engine

摘要

Regulated and unregulated gaseous emissions with high pressure and low pressure ECR (exhaust gas recirculation) system were tested in a 4-cylinder, light-duty diesel EURO IV engine typically used in European vehicles. Four different engine calibrations with the low pressure EGR system were studied. Regulated emissions of NO_x, CO, HC and CO_2 were measured for each configuration. Unburned Hydrocarbon Speciation, HCHO (formaldehyde), HCOOH (formic acid) and N_2O (nitrous oxide) were also measured in order to determine the MIR (maximum incremental reactivity) of the gaseous emissions. Pollutants were measured without the DOC (diesel oxidation catalyst) to gather data about raw emissions. When the low pressure EGR system was used, decreases in NOx, N_2O and fuel consumption were observed and significant increases HC, CO and unregulated emissions; this is the result of a lower intake manifold temperature, which provides a higher gas density which modifies the combustion process. The potential of tropospheric ozone production was higher in all cases when the low pressure EGR was used.