A model for the unsteady motion of pollutant particles in the exhaust system of an I.C. engine

The measurement of the various pollutant species (HC, CO, NO, etc.) has become one of the main issues in internal combustion engine research. This interest concerns not only their quantitative measurement but also the study of the mechanism of their formation. In fact, pollutant species concentration can be used as an indicator for the combustion characteristics. For instance, it enables the determination of a lean or a rich combustion, the percentage of EGR, etc. The purpose of this research is to investigate the behavior of pollutant gas particles in the first part of an engine exhaust system through a detailed study of the unsteady flow in the exhaust pipe. The results are intended to designate the appropriate sensor positions which ensure accurate measurement results. This investigation wants to track an inert component in the exhaust system, namely the NO gas. This component can be considered as inert since its reaction freezes at temperatures which are higher than outside the cylinder. For this purpose a thermodynamic model of the in-cylinder process has been matched with a model for the fluid dynamics of the exhaust gas process to simulate the exhaust conditions. A set of simulations was performed for different working conditions of an engine. The simulated transient pressure field in the pipe has been compared with real data gathered on a V6 SI engine. Copyright © 2003 SAE International.