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

摘要

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. 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. 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.