Four-Flow Path High-Efficiency NOx and PM Exhaust Emission Control System for Heavy-Duty On-Highway Diesel Engines

A 5.9 liter medium-heavy-duty diesel engine, meeting the emissions performance of a MY 2000 US heavy-duty on-highway engine, was tested with and without a diesel exhaust emission control system consisting of catalyzed diesel particulate filters and adsorber catalysts NO_x arranged in a four-flow path configuration. This four-flow path system represents a significant reduction in catalyst volume when compared to previous systems tested by EPA. The goal of this project was to achieve high NO_x reduction over the Heavy-Duty Diesel Engine Federal Test Procedure (HDDE-FTP) and Supplemental Emission Test (SET), consistent with the 2007 U.S. heavy-duty engine emissions standards, using this reduced volume system. Supply of hydrocarbon reductant for NO_x adsorber regeneration was accomplished via a secondary exhaust fuel injection system. Alternating the restriction of the exhaust flow between the four-flow paths allowed reductant injection and adsorber regeneration to occur under very low space velocity conditions. Emissions of NO_x were reduced by 78% over the HDDE-FTP and 89% over the SET; reduced by 78% over the HDDE-FTP and 89% over the SET; and particulate matter (PM) emissions were reduced by 86% over the HDDE-FTP and SET. System improvements were identified during this testing which should allow the system to meet the 2007 emission targets. These improvements will be validated in future testing.