Numerical Optimization of Flow Uniformity inside a Catalytic Converter

Abstract

A serious issue that is always been debated among the environmentalists over the decades and recent years is air pollution. Automobiles throughout the world are one of the primary consumers of fossil fuel. Internal Combustion engines generate undesirable emissions during the combustion process, which include, NOX, CO, unburned HC, smoke etc. All these pollutants are harmful to environment and human health. They are the main causes for greenhouse effect, acid rain, global warming etc. The simplest and the most effective way to reduce NOX and PM, is to go for the after treatment of exhaust. The most effective after treatment for reducing engine emission is the catalytic converter found on most automobiles and other modern engines of medium or large size. Our main focus in this study is to modify the cross sectional geometry of the catalytic converter to find the optimum design configuration which would establish a good uniformity in the flow development. Inlet velocity, inlet angle of the catalytic converter and aspect ratio of the substrate is varied to find out the optimum configuration of the catalytic converter. Through Computational Fluid Dynamics (CFD) analysis, various models with different wire mesh grid size combinations were simulated using the appropriate boundary conditions. It is shown than aspect ratio and inlet angle heavily influences the flow condition inside the flange section and substrate section. For elongated oval (Aspect Ratio 2) with 35 degree inlet angle the uniformity index is 0.9902 which is significantly higher than the standard substrate model. This study reveals that tailoring of inlet cone angle and aspect ratio of the substrate can significantly improve the flow uniformity index thus results in optimum utilization of the available catalytic volume which obviously results in improved emission characteristics. newline newline newline