Fuel Sulfur Effects on a Medium-Duty Diesel Pick-Up with a NOX Adsorber, Diesel Particle Filter Emissions Control System: 2000-Hour Aging Results 2006-01-0425

Increasing fuel costs and the desire for reduced dependence on foreign oil have brought the diesel engine to the forefront of future medium-duty vehicle applications in the United States due to its higher thermal efficiency and superior durability. One of the obstacles to the increased use of diesel engines in this platform is the Tier 2 emission standards. In order to succeed, diesel vehicles must comply with emissions standards while maintaining their excellent fuel economy. The availability of technologies-such as common rail fuel injection systems, low-sulfur diesel fuel, oxides of nitrogen (NO_X) adsorber catalysts or NACs, and diesel particle filters (DPFs)-allows for the development of powertrain systems that have the potential to comply with these future requirements. In support of this, the U.S. Department of Energy (DOE) has engaged in several test projects under the Advanced Petroleum Based Fuels-Diesel Emission Control (APBF-DEC) activity [1, 2, 3, 4, 5]. Three of the APBF-DEC projects evaluated the sulfur tolerance of a NAC/DPF system and the full useful life implications of NAC desulferization. The test bed for one project in this activity is a 2500 series Chevrolet Silverado equipped with a 6.6L Duramax diesel engine certified to 2002 model year (MY) federal heavy-duty and 2002 MY California medium-duty emission standards.

While NAC systems have demonstrated extremely high levels of NO_X reduction in steady-state laboratory evaluations, the application of a NAC system to an actual transient engine has not been demonstrated. Such an application requires the development of an integrated engine/emissions management system [6, 7, 8, 9, 10, 11, 12, 13, 14, 15]. Two previous papers detailed the thermal and NO_X adsorber management aspects of a system applied to the project test bed [1, 2]. The final control strategies applied to this project achieved over 98% reductions in tailpipe NO_X mass emission over the hot-start Urban Dynamometer Driving Schedule (UDDS). This paper discusses the emission results of the system measured over the course of 2000 hours of on-engine aging exposure. The system was evaluated over the cold-start UDDS, hot-start UDDS, Highway Fuel Economy Test (HFET) and US06 portion of the Supplemental Federal Test Procedure (SFTP). The discussion will cover the aging cycle utilized and its development, details of the desulfurization process, and regulated emission results over the test cycles of interest. After 2000 hours of on-engine aging, the NAC/DPF system demonstrated an average NO_X reduction of 89% and PM reduction of 94% over the composite Federal Test Procedure (FTP).