Aftertreatment Architecture and Control Methodologies for Future Light Duty Diesel Emission Regulations

Future light duty vehicles in the United States are required to be certified on the FTP-75 cycle to meet Tier 3 or LEV III emission standards [1, 2]. The cold phase of this cycle is heavily weighted and mitigation of emissions during this phase is crucial to meet the low tail pipe emission targets [3, 4]. In this work, a novel aftertreatment architecture and controls to improve Nitrogen Oxides (NO_x) and Hydrocarbon (HC) or Non Methane Organic gases (NMOG) conversion efficiencies at low temperatures is proposed. This includes a passive NO_x & HC adsorber, termed the diesel Cold Start Concept (dCSC™) catalyst, followed by a Selective Catalytic Reduction catalyst on Filter (SCRF^®) and an under-floor Selective Catalytic Reduction catalyst (SCR). The system utilizes a gaseous ammonia delivery system capable of dosing at two locations to maximize NO_x conversion and minimize parasitic ammonia oxidation and ammonia slip. This aftertreatment system was evaluated on the chassis dynamometer and demonstrated the potential to achieve Tier 3 Bin 30 (T3B30) or SULEV30 emissions on the FTP-75 (Federal Test Procedure) cycle and HWFET (highway fuel economy) test cycles. A similar aftertreatment architecture, consisting of a Diesel Oxidation Catalyst (DOC) instead of a diesel cold start concept catalyst, was also evaluated. This system demonstrated the potential to achieve Tier 3 Bin 125 or ULEV125 emissions on the FTP-75 cycle. The aftertreatment architecture with the diesel cold start concept catalyst in place of the DOC was a key enabler to improve the low temperature NO_x and HC conversions to demonstrate the potential to meet Tier 3 Bin 30 or SULEV30 regulations.