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An experimental and theoretical investigation has been performed on the flow and pressure loss in axisymmetric catalytic converters and isolated monoliths under steady, isothermal flow conditions. Monolith resistance has been measured with a uniform, low turbulence, incident flow field. It has been found that the pressure loss expression for fully developed laminar flow is a good approximation to observations for x+ greater than 0.2. However, for x+ less than 0.2 the additional pressure loss due to developing flow is no longer negligible and a better approach is to use the correlation proposed by Shah (16). From experimental studies on the axisymmetric catalytic converters non-dimensional power law relationships have been derived relating maldistribution and pressure drop to expansion length, Re, and monolith length. These expressions are shown to generally fit the data well within ±5%.

With the increasingly widespread use of catalytic converters for meeting exhaust emission regulations, considerable attention is currently being directed towards improving their performance. Experimental analysis is costly and time consuming. A desirable alternative would be a computational model based on established numerical techniques. To this end a transient three-dimensional model has been developed using a commercial CFD code. It simulates the fluid dynamics, chemical kinetics and heat and mass transfer that takes place in catalysts and their associated assembly. As a result the model can be used to predict important performance parameters such as conversion efficiency, incurred pressure drop and the thermal environment.