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With a view to application of model base development to exhaust catalyst design, a numerical model for catalytic reaction was formulated so as to be able to predict tailpipe emission during test mode running. In order to grasp the catalytic reaction characteristics, catalyst characteristics test using catalyst test pieces and synthetic gas was conducted and the basic reaction that takes place inside the exhaust catalyst was modeled by employing the 3 overall reaction models: Arrhenius model, competitive adsorption model, and adsorption model. By using the formulated numerical catalyst model, tailpipe emission estimation for a gasoline engine vehicle was carried out, and an estimated accuracy of within ±10% error range from the actual measurement was realized for all of CO, HC, and NO.

This paper presents a new substrate for Lean NOx Traps (LNT) which enables high NOx conversion efficiency, even after long-term aging, when using alkali metals as the NOx adsorber. When a conventional metal honeycomb is used as the LNT substrate, the chromium in the metal substrate migrates into the washcoat and reacts with the alkali metals after thermal aging. In order to help prevent this migration, we have developed a new substrate where a fine -alumina barrier is precipitated to the surface of the metal substrate. The new substrate is highly capable of preventing migration of chromium into the washcoat and greatly enhances the NOx conversion. The durability of the new substrate and emission test using a test vehicle are also examined.

As a result of higher exhaust gas temperature for an improvement of fuel consumption, catalytic converters must be much more durable at high temperature. To satisfy such requirements, we have developed an advanced metal substrate using newly developed stainless Fe-Cr-Al foil, which contains more than 7.5 mass% of aluminum. The developed foil elongates durable lifetime about 4 times compared with the conventional foils in high temperature oxidizing atmospheres. The newly developed metal substrate is suitable for exhaust systems which is used under conditions of high exhaust gas temperature above 1000 °C.

In this study, with the purpose of applying to the metal catalyst substrates, we have examined the feasibility of improving the light-off performance of a catalytic converter by enhancing heat transfer in the cells with heat-transfer promoters. Experimental and CFD analyses have been conducted to estimate heat transfer rates and pressure losses of the model cells with hemispherical protrusions. The analyses show that, by enhancing heat transfer of the cells, the cell density can be reduced keeping the catalytic performance in the steady state at the same level as that of conventional ones. As a result, the thermal mass of the substrate can be also reduced effectively without an increase of the pressure loss, and consequently the light-off performance of the catalytic converter can be improved noticeably.

In order to quantitatively evaluate mechanical durability of metal substrates for catalytic converters under heat cycles, thermal stresses and strains were simulated by FEM elastic-plastic analysis. Flat and corrugated sheets constituting honeycomb structures were directly modeled by thick-shell elements without replacing the structures with equivalent solid elements. It was reported that an asymmetric joint structure with “Strengthened Outer Layer” could provide metal substrates with high mechanical durability against heat cycles and the results of analysis in this study could show their high durability. It is important for improvement of mechanical durability to control the location of initial cracks generation and the direction of their propagation.