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This paper presents the performance and durability test results of a newly developed diesel particulate filter (DPF) made of silicon carbide (SiC). While SiC offers thermal resistance that is superior to cordierite, it requires a complex, multi-segment bonded design structure due to the thermal expansion coefficient that is higher than cordierite, which leads to a higher thermal stress during regeneration. This company has developed a honeycomb slit-type DPF made from a newly developed SiC through the application of its own honeycomb forming technology and material technology, and has also succeeded in controlling the cost of the product through a simplified design.

Catalytic performance can be improved by reducing bulk density (BD) and increasing geometric surface area (GSA) of ceramic substrate. Ultra thin-wall / high cell-density ceramic substrates, such as 3 mil/ 600 cpsi and 2 mil/ 900 cpsi have improved the catalytic performance over the conventional 6 mil/ 400 cpsi substrates. and are expected to help in complying with future emission regulations, as well as catalyst down-sizing. This paper describes the effects of BD and GSA using Pd-based catalysts. The significant reduction of hydrocarbons emissions was demonstrated at close-coupled location, and dual bed design was proven effective. The effectiveness at under-floor location was not as significant as the close-coupled location. This paper proposes the converter layout of dual bed close-coupled converter consisting of small volume 2 mill 900 cpsi front catalyst and large volume 3 mil/ 600 cpsi rear catalyst.

Catalytic performance can be improved by increasing geometric surface area (GSA) and reducing bulk density (BD), namely heat capacity, using high cell-density / thinwall advanced ceramic substrates. The advanced substrates, such as 3 mil/600 cpsi and 2 mil/900 cpsi have improved the catalytic performance over the conventional substrates, and are expected to help in complying with future emission regulations, as well as catalyst downsizing. This paper describes the effects of GSA and BD using Pd-based catalysts. The reduction of hydrocarbons emissions was demonstrated significantly at close-coupled location, and dual bed design was proven effective. The effectiveness at under-floor location was not as significant as the close-coupled location.

This paper proposes a high temperature manifold converter with a thin wall ceramic substrate, such as; 4mil/400cpsi and 4mil/600cpsi. Double-wall cone insulation design was proposed for close-coupled converters to protect the conventional intumescent mat from high temperature. However, the double wall cone insulation is not applicable when the converter is directly mounted to the exhaust manifold without an inlet cone. The prototype manifold converter was tested under hot vibration test with a non-intumescent ceramic fiber mat and retainer rings as a supplemental support. The converter demonstrated durability for 10 hours under 80G acceleration and 100 hours under 60G acceleration with 1,050 °C catalyst bed temperature. The skin temperature of the heat shield was kept below 400 °C.

European car manufacturers have traditionally used Pt/Rh or Pd/Rh TWCs with PM loadings of 40-60 g/ft3. New regulations, however have stimulated interest in high Pd loadings (100 g/ft3 or more) in order to drastically reduce HC emissions. Pd is known to have good HC oxidation activity, high thermal stability and is relatively inexpensive. However, it suffers from excessive sensitivity to poisons and is usually associated with poor NOx conversion. A research program was initiated with the goal of capturing the benefits of high Pd concentrations while minimizing its disadvantages. It was found that trimetal formulations (Pt/Pd/Rh) could achieve high NOx conversions provided the loadings of the PMs were optimized based on a Box-Behnken design. Data showing the high thermal stability and low H2S emissions of these new “TriMax” catalysts will be presented. Their high performance has led to commercial acceptance by several European car manufacturers.

In a direct injection (D.I) diesel engine with high efficiency, the blue and white smoke (cold smoke) exhaust at cold starting and warming-up are unsolved problems in the development of small D.I diesel engines. In this experiment, the fuel adhering on the combustion chamber wall, and which influences the cold smoke, was measured on a special engine which can be stopped immediately after a single injection. It is found that 30-40% of the injected fuel remained on the combustion chamber wall after burning at low compression ratios and under low temperature conditions.