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Stringent emissions legislation for diesel-powered vehicles, soon to go into effect, has led to new advances in both Diesel Oxidation Catalysts (DOC) and Diesel Particulate Filters (DPF). This paper reviews some of the new developments in DOC support design which lead to improved light-off behavior and higher overall emissions performance through lower thermal mass, higher Geometric Surface Area (GSA) and larger Open Frontal Area (OFA) than those afforded by the standard cordierite 400/6.5 cell configuration. The four different DOC supports examined in this paper include 400/4, 200/8, 300/8 and 400/6.5 - the last one serving as baseline.

This paper reviews the development and successful application of ceramic catalytic converters for controlling automotive exhaust emissions. It presents the scientific rationale for designing the high surface area substrate to meet both performance and durability requirements. This is followed by a step-by-step design process for each of the converter components. The initial design stage focuses on understanding automaker's requirements and optimizing component design commensurate with them. The intermediate stage involves laboratory testing of converter components in simulated environment and ensuring component compatibility from durability point of view. The final design stage addresses the critical tests on converter assembly to ensure performance and field durability. In addition, it examines the necessary trade-offs and associated design modifications and evaluates their impact on warranty cost for system failure.

The shape and size of the unit cell of a ceramic monolith have a profound influence on its geometric and mechanical properties. These, in turn, affect the catalytic performance, converter durability and vehicle drive-ability. This paper presents the important relationships between cell geometry and monolith's open frontal area, geometric surface area, hydraulic diameter, bulk density, structural rigidity, strength and heat transfer characteristics of the monolith; both the square and triangular cells are considered. These relationships provide a rational basis for selecting the cell shape and size which will yield the best balance between the various performance requirements, i.e. light-off characteristics, conversion efficiency, back pressure and long-term dutability. It is shown that certain tradeoffs are necessary in selecting the final cell geometry which is best accomplished by prioritizing the various performance requirements.

The stringent emissions legislation has necessitated advances in the catalytic converter system comprising the substrate, washcoat technology, catalyst formulation and packaging design. These advances are focused on reducing light-off emissions at lower temperature or shorter time, increasing FTP efficiency, reducing back pressure and meeting the mechanical and thermal durability requirements over 100,000 vehicle miles. This paper reviews the role of cordierite ceramic substrate and how its design can help meet the stringent emissions legislation. In particular, it compares the effect of cell geometry and size on performance parameters like geometric surface area, open frontal area, hydraulic diameter, thermal mass, heat transfer factor, mechanical integrity factor and thermal integrity factor - all of which have a bearing on emissions, back pressure and durability. The properties of advanced cell configurations like hexagon are compared with those of standard square cell.