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With input from industry, the United States Environmental Protection Agency (US EPA) has developed ramped modal versions of its steady-state certification duty cycles for land-based nonroad diesel engines. The Ramped Modal Cycle (RMC) calls for gathering gaseous and particulate emissions continuously over the cycle, while the steady-state test specifies that samples be taken for only a portion of the time at each mode. The RMC test was developed in part to capture discrete regeneration events associated with advanced catalyst systems like NOx adsorbers that are anticipated to meet future nonroad emission standards.1 To compare the emission levels between these two tests, a 5.9 liter medium-heavy-duty on-highway diesel engine rated for 260 hp @ 2500 rpm, was run at EPA's National Vehicle and Fuel Emissions Laboratory (NVFEL), derated to 180 hp @ 2500 rpm, to simulate the configuration of a typical nonroad engine.

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 NOx 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 NOx 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 NOx adsorber regeneration was accomplished via a secondary exhaust fuel injection system.

A 5.9 liter medium-heavy-duty diesel engine was modified to approximate the emissions performance of a MY 2004 US heavy-duty on-highway engine. The engine was tested with and without a diesel exhaust emission control system consisting of catalyzed diesel particulate filters and NOx adsorber catalysts arranged in a dual-path configuration. The goal of this project was to achieve hot-start HDDE-FTP emissions consistent with the recently announced 2007 U.S. heavy-duty engine emissions standards. Supply of hydrocarbon reductant for NOx adsorber regeneration was accomplished via a secondary exhaust fuel injection system. An alternating restriction of the exhaust flow between the two flow paths allowed injection and adsorber regeneration to occur under very low space velocity conditions. NOx and PM emissions over the hot-start portion of the HDDE-FTP transient cycle were 0.13 g/bhp-hr and less than 0.002 g/bhp-hr, respectively.

A 5.9-liter medium-heavy-duty diesel engine, equipped with a diesel exhaust emission control system consisting of catalyzed diesel particulate filters and NOx adsorber catalysts arranged in a dual flow path configuration was evaluated with the goal of studying the thermal aging characteristics of a number of NOx adsorber formulations. These adsorbers were tested with near zero sulfur fuel and low sulfur engine oil to minimize the impact of sulfur poisoning on the test results. Testing was performed at a high temperature engine operating mode to provide accelerated but not abusive aging. The test duration ranged from 100 to 250 hours depending on the severity of the aging at the 100 hour mark. The initial “zero” sulfur testing screened the NOx adsorber formulations for future testing and established a thermal aging baseline.

A 5.9 liter medium-heavy-duty diesel engine, equipped with a diesel exhaust emission control system consisting of catalyzed diesel particulate filters (CDPF) and NOx adsorber catalysts arranged in a dual-path configuration, was evaluated with the goal of developing desulfation strategies for in-use NOx adsorber desulfation. NOx adsorber desulfation was accomplished by providing reductant via a secondary exhaust fuel injection system and exhaust flow via an exhaust bypass valve. An alternating restriction of the exhaust flow between the two flow paths allowed reductant injection and adsorber desulfation to occur under very low space velocity conditions. An exhaust bypass valve connecting the dual path configuration upstream of the catalyzed diesel particulate filters allowed controlled addition of exhaust into the desulfating pathway for desulfation method development.