Clark, D. and Pauly, T., "An Approach to Controlling N2O Emission on HDD On-Road Applications," SAE Int. J. Engines 9(3):1623-1629, 2016, doi:10.4271/2016-01-0948.
Control of N2O emissions is a significant challenge for manufacturers of HDD On-Road engines and vehicles due to requirements for NOx control and Green House Gas (GHG) Phases I & II requirements. OEMs continually strive to improve BSFE which often results in increased engine out NOx (EO NOx) emissions. Consequently, the necessity for higher NOx conversions results in increased N2O emissions over traditional SCR and SCR+ASC catalysts systems . This study explores methods to improve NOx conversion while reducing the SCR contribution of N2O across the exhaust after treatment systems. For example, combinations of two traditional SCR catalysts, one Iron based and another Copper based, can be utilized at various proportions by volume to optimize their SCR efficiency while minimizing the N2O emissions. Results show that a proper combination of catalysts volume can significantly reduce N2O levels while simultaneously reaching the highest levels of NOx performance achieved in the study. The results highlight the traditional expected tradeoff between N2O emissions and NOx performance across an ATS system while providing design guidance to manage this tradeoff and, equally importantly, confidence that solutions exist to meet ever tighter emission requirements.