Assessment of pollutants emission and aftertreatment efficiency in a GTDi engine including cooled LP-EGR system under different steady-state operating conditions

Abstract

Nowadays, EGR systems are being incorporated in the research focused on spark-ignition direct-injection engines as a solution to the problems presented by them; i.e. knock risk and high combustion temperature which produces high NOx emission. Since the major part of the investigations are centered on engine performance or engine simulation aside pollutants emission and aftertreatment evaluation, this paper focuses on these topics: gaseous and particle emission analysis and aftertreatment efficiency evaluation when cooled LP-EGR system is applied to a GTDi engine. This work has been performed in a 4-cylinder, turbocharged, direct-injection gasoline engine with 2.0 L displacement. The equipment used in this study are TSI-EEPS for particle measurement and HORIBA MEXA 1230-PM for soot measurement being HORIBA MEXA 7100-DEGR with a heated line selector the system employed for regulated gaseous emission measurement and aftertreatment evaluation. A reduction around 50% of NOx with an increase of HC and CO emissions was found in medium-load operating points. At full-load conditions, the suppression of fuel enrichment including EGR leads in a drastically reduction in CO maintaining similar HC and NOx emissions. Furthermore, PN and soot emissions also decrease as EGR is included and spark timing advanced in all the tested conditions.