(587b) Numerical Simulation of Gas Flow in Segmented Catalytic Converters

Catalytic flow-through converters are important parts of vehicle after-treatment systems for both gasoline and diesel application. These parts are conventionally fabricated from ceramic materials and have ?honeycomb? structure with many channels of small diameter packed into relatively large supports. Recently, there has been much interest in improvement of conversion performance of such systems to meet stringent US and European emission regulations.

One factor limiting the conversion performance of the device is formation of a concentration boundary layer across the channel walls. Characterized with diffusion mass transfer, this boundary layer impedes exhaust component conveyed to the vicinity of washcoat impregnated on the wall of catalytic converter. Since chemical reactions occur inside the washcoat, it, thus, would be beneficial to develop a design modification allowing for break-out of concentration boundary layers and remixing of channel flow.

In this work, we apply numerical techniques to analyse exhaust gas flow patterns in segmented converter gaps. Detailed study of potential sources of turbulence in gaps is made in different length scales and for varying gap length.

Besides segmented structures with gaps, we also consider so called ?stacked? converter designs with no gap between elements and study conversion properties of such devices in comparison with conventional one-piece parts.