Durable Packaging Design for Cordierite Ceramic Catalysts for Motorcycle Application 930161

The motorcycle emissions regulations for both two-stroke and four-stroke engines, which are receiving worldwide attention, will go into effect in the very near future. To meet these regulations, the motorcycles will require a catalyst in conjunction with the muffler due to space limitations. The combination of high engine speeds, high vibrational acceleration, high HC and CO emissions, high oxidation exotherms, and stringent durability requirements, points to cordierite ceramic substrate as an ideal catalyst support. However, as an integral unit within the muffler, its packaging design must be capable of withstanding isothermal operating conditions which may exceed the upper intumescent temperature limit of the ceramic mat.

This paper describes a durable packaging design for the ceramic catalyst which employs a hybrid ceramic mat, special end rings and gaskets, and high strength stainless steel can. Such a packaging design enjoys sufficient radial and axial mounting pressures up to temperatures approaching 1000°C. The robustness of converter package is verified experimentally by two different laboratory tests, namely an axial retention test and a high frequency/high acceleration vibration test, both at temperatures approaching 1000°C. The use of hybrid mat with high mount density maintains the required pressure to survive 100 hours of high temperature and high acceleration vibration testing. The pertinent physical properties of ceramic catalyst and hybrid mat, which contribute to robustness, are also presented. The systems design approach for a durable converter, employed here, also permits optimization of cell size to minimize back pressure penalty while providing adequate surface area for conversion efficiency.