The objective of this paper is to present the results of diesel exhaust aftertreatment testing and analysis done under the FreedomCAR program. Nitrogen Oxides (NOx) adsorber technology was selected based on a previous investigation of various NOx aftertreatment technologies including non-thermal plasma, NOx adsorber and active lean NOx. Particulate Matter (PM) emissions were addressed by developing a catalyzed particulate filter. After various iterations of the catalyst formulation, the aftertreatment components were integrated and optimized for a light duty vehicle application.This compact exhaust aftertreatment system is dual leg and consists of a sulfur trap, NOx adsorbers, and catalyzed particulate filters (CPF). During regeneration, supplementary ARCO ECD low-sulfur diesel fuel is injected upstream of the adsorber and CPF in the exhaust. Steady state and transient emission test results with and without the exhaust aftertreatment system (EAS) are presented. Results of soot filter regeneration by injecting low-sulfur diesel fuel and slip of unregulated emissions, such as NH 3 , are discussed. Effects of adsorber size and bypass strategy on NO x conversion efficiency and fuel economy penalty are also presented in this paper. The results indicate that if the supplementary fuel injection is optimized, NH 3 slip is negligible. During the FTP cycle, injection of low sulfur diesel fuel can create temperature exotherms high enough to regenerate a loaded CPF. With the optimized NOx adsorber regeneration strategies the fuel injection penalty can be reduced by 40 to 50%. Results for various other issues like low temperature light off, reductant optimization, exhaust sulfur management, system integration and design trade-off, are also presented and discussed in this paper.

Due to their excellent fuel efficiency, reliability, and durability, compression ignition direct injection (CIDI) engines have been used extensively to power almost all highway trucks, urban buses, off-road vehicles, marine carriers, and industrial equipment. CIDI engines burn 35 to 50% less fuel than gasoline engines of comparable size, and they emit far less greenhouse gases (Carbon Dioxides), which have been implicated in global warming. Although the emissions of CIDI engines have been reduced significantly over the last decade, there remains concern with the Nitrogen Oxides (NO X ) and Particulate Matter (PM) emission levels. In 2000, the US EPA proposed very stringent emissions standards to be introduced in 2007 along with low sulfur (< 15ppm) diesel fuel. The California Air Resource Board (CARB) has also established the principle that future diesel fueled vehicles should meet the same emissions standards as gasoline fueled vehicles and the EPA followed suit with its Tier II emissions regulations.Meeting the Tier II standards requires NO X and PM emissions to be reduced dramatically. Achieving such low emissions while minimizing fuel economy penalty cannot be done through engine development and fuel reformulation alone, and requires application of NO X and PM aftertreatment control devices. A joint effort was made between Cummins Inc. and the Department of Energy to develop the generic aftertreatment subsystem technologies applicable for Light-Duty Vehicle (LDV) and Light-Duty Truck (LDT) engines. This paper provides an update on the progress of this joint development program.Three NO X reduction technologies including plasmaassisted catalytic NO X reduction (PACR), active lean NO X catalyst (LNC), and adsorber catalyst (AC) technology using intermittent rich conditions for NO X reduction were investigated in parallel in an attempt to select the best NO X control approach for light-duty aftertreatment subsystem integration and development. Investigations included system design and analysis, critical lab/engine experiments, and ranking then selection of NO X control technologies against reliability, up-front cost, fuel economy, service interval/serviceability, and size/weight. The results of the investigations indicate that the best NO X control approach for LDV and LDT applications is a NO X adsorber system. A greater than 83% NO X reduction efficiency is required to achieve 0.07g/mile NO X Tier II vehicle-out emissions. Both active lean NO X and PACR technology are currently not capable of achieving the high conversion efficiency required for Tier II, Bin 5 emissions standards.In this paper, the NO X technology assessment and selection is first reviewed and discussed. Development of the selected NO X technology (NO X adsorber) and PM control are then discussed in more detail. Discussion includes exhaust sulfur management, further adsorber formulation development, reductant screening, diesel particulate filter development & active regeneration, and preliminary test results on the selected integrated...

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