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Increasingly stringent emission regulations within the diesel engine industry, particularly with regard to particulate matter and oxides of nitrogen, have led to the development of a number of aftertreatment control technologies. Most of these control technologies address either oxides of nitrogen (NOx) emissions or particulate matter (PM) emissions, but not both. Until now no technologies were available that simultaneously reduced both these pollutants. Ceryx Incorporated has developed a novel four-way converter for the simultaneous reduction of PM, NOx, CO, and HC from diesel engines. The Ceryx systems integrate diesel particulate filters (DPF's) and lean NOx catalysts (LNC's) in the core of a proprietary heat exchanger. The heat exchanger serves to “recycle” heat from exothermic reactions over the catalyst by transferring heat from the hot exit gases to the cooler inlet gases.

Technologies for emission reduction from diesel (a.k.a. compression ignition) engines can be categorized as pre-combustion elements, in-cylinder combustion elements and post-combustion elements. Many technologies reduce emissions, yet have difficulty in simultaneously improving engine performance, saving fuel or reducing costs, all four of which are critical elements to successful technology introduction. Most of these technologies are being developed as discrete systems and often face frustrating “trade-offs” such as emission reductions causing engine performance degradation and/or fuel penalties, or the common PM/NOx dilemma. This paper outlines the key trade-offs of the four criteria, discusses various technologies and their limitations, and suggests a systems-level optimization strategy for a cleaner diesel engine.

Poor air quality represents a serious threat to the health and quality of life of people across the globe, as well as increasing the burden on the U.S. and international economy. These threats exist despite progress being made at many local, state and federal levels to curb the growing pollution problem due to increased industrialization and the expansion of motor vehicle usage. Many approaches have been developed over the last decade to combat pollutants [primarily oxides of nitrogen (NOx), hydrocarbons (HC), particulate matter (PM) and carbon monoxide (CO)] contributed by mobile sources. This paper will focus on PM and NOx, the two pollutants most commonly associated with heavy-duty diesel engines. The paper will also focus on the development of an air management technology designed to increase combustion efficiency within the engine chamber that reduces engine-out emissions while increasing fuel efficiency and engine performance.

Combustion processes inside the engine cylinder dictate engine power, efficiency and emissions. Following compression, burning proceeds as air and fuel mix to the composition necessary for combustion to take place. In the diesel engine, fuel is injected in the cylinder into high pressure and temperature air. The engine has less time to form the air-fuel mixture, which is less homogenous as a result. This creates periods during the combustion phase where the air to fuel relationship is non-optimized. This is particularly apparent during low-end operating cycles. Traditionally, efforts to reduce engine-out emissions have concentrated on fuel management. Development of two advanced technologies on turbocharged diesel engines have focused instead on air management with the optimization of this relationship of air to fuel.