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This paper presents a simplified thermal model for round catalytic converters in steady state operation. Using this model, the analytic solution for the temperature distribution in the monolithic substrate is obtained. This analytic solution in the substrate is, then, combined with those in the intumescent mat [1] and the metal shell to obtain the temperature profile in the radial direction of the converter except for three unknown temperatures at the three material interfaces, which can be solved using an Excel application program. This analytical temperature solution facilitates the studies of the effects of various design parameters such as the exhaust gas temperature, exhaust gas flow rate, substrate cell geometry, converter dimensions, and ambient temperature and flow, etc.

The isostatic strength of porous cordierite ceramic monoliths plays an important role during canning and subsequent operation of automotive catalysts. Its value depends on wall porosity, cell geometry, skin thickness and morphology, monolith size and contour, and substrate/washcoat interaction. If the stresses induced by canning loads and closure speeds exceed the isostatic strength, the monolith may exhibit either crushing or shear type failure. This paper presents the room temperature isostatic strength data for coated and uncoated ceramic monoliths of different contour, size, and cell geometry. The applied isostatic load on the monolith is translated into stresses in the porous cell wall using both an analytical model and finite element analysis. It is found that the failure criteria are governed by the fundamental tensile and compressive strengths of the cell wall.