| This paper introduces the structure and development of the automotive catalytic converters, analyzes the connection of the asymmetry of airflow distributing and transformation efficiency, illuminates the necessary of optimize design; It includes and summarizes the research of the airflow distributing characteristic in the automotive catalytic converters all over the world, indicates that the structure ought to be improved; It constitutes the airflow numerical model in the catalytic converters, respectively simulates the difiusion header structure of routine end monolith, 60° taper end monolith, 120° taper end monolith matched 30°, 45°, 60° expand half angle, elementary educes that the structure of 90° taper end matched 30° expand half angle is the best to improve the uniformity; It puts up the isothermal, stabilized and axis symmetrical experiment device, the structure and boundary condition is the same to the simulation, measures the airflow velocity in the monolith and protracts the curve of airflow radial distributing, the result can reflect the real complexion in the catalytic converters, so it can guidance the practice; It defines the conception of the flux bear percent and the flow uniformity exponent to describe the uniformity of the airflow radial distributing, concretely analyzes the influence of difiusion half angle, difiusion type, taper end, end diameter, monolith locations matching and intake velocity and so oa It induces that the taper end monolith matched enhanced difiusion is the best to improve the uniformity when tile end diameter corresponds to the radius of the entrance, and the improved extent is better when the intake velocity is little; It theoretic analyzes and numerical simulates the exhaust pressure and cold start calefactive peculiarity, illuminates that the difiusion structure what the author advanced can bring positive influence to others. So it can be applied in practice.
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