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The ability to accurately predict skin temperatures of catalytic converter and manifold is very important for a robust/durable design of the vehicle exhaust system, especially in the development of close coupled converter system. In this paper, Computational Fluid Dynamics (CFD) is used to calculate the skin temperature of complicated components in vehicle exhaust system such as catalytic converter. Generally, a catalytic converter consists of substrate, mat, outer shell, inner cone, cone insulation, and outer cone. 3-D compressible turbulent fluid flow with heat transfer involved in force and natural convections, heat conduction and radiation is numerically simulated. First, both numerical calculation and experimental tests are conducted for a catalytic converter under the same operation conditions to evaluate the accuracy of current numerical method. Good agreement is found between CFD prediction and experimental tests.

Stricter emission standards are forcing automakers to attach catalytic converters directly to the exhaust manifold. Mounting catalytic converter at or near the exhaust manifold helps to reduce the increase in emissions that occurs during the first few minutes after a cold engine is started. The spike occurs because cold engines require a richer air-fuel mixture to run smoothly. The emission standards can be met only by new designs of exhaust system with the catalyst being as close as possible to the engine, and with the thin walled exhaust manifolds. With concept-to-customer timing continuously shrinking in the automotive industry, the need to quickly validate the engineering designs is becoming ever more critical. It is no longer acceptable to design a component, produce soft tooling, build and test a prototype, analyze what failed, and then redesign.