Simulation on the characteristic of gas flow and mixing for the location of the oxygen sensor in the exhaust system

One of the methods for reducing engine exhaust emission is to use a close-coupled catalytic converter (CCC). To obtain the maximum conversion efficiency in a CCC, the exhaust gas should be uniformly distributed across the frontal area of the catalytic substrate as much as possible, and the engine should be operated at a condition close to the stoichiometric air/fuel ratio by using an oxygen sensor in the exhaust system. A theoretical and computational study on three-dimensional unsteady compressible non-reacting flow for three kinds of exhaust manifold and a CCC system was performed to understand the flow characteristics and estimate the effects of geometric change. In each case, the oxygen sensor location where the local exhaust gas can represent the average flow of exhaust is proposed.