Real-time simulation of the effects of catalyst on automotive engines performance

Abstract

Restrictions on pollutant emissions nowadays force the use of catalyst-based after-treatment systems both in SI and in Diesel engines. The use of a honeycomb support is an established practice: however, to overcome drawbacks such as poor flow homogenization, the use of ceramic foams has been recently investigated [1,…] as an alternative showing better conversion efficiencies (but with higher pressure losses). The proposed paper is aimed at evaluating the effects of these supports on engine performance through a 0D “crank-angle” mathematical model developed by the Authors in Simulink® for real-time calculations [2,3]. This tool has been enhanced improving the heat exchange model of the exhaust manifold to take account of thermal dynamics during transients. Besides a 0D model of the catalyst has been developed to simulate mass flow and thermal processes. Gas temperature at the catalyst outlet is calculated from energy conservation equation taking account of thermal inertia of the system and considering convective heat exchange between gas and monolith and thermal energy from the partial oxidation of unburnt compounds. The model has been used to simulate an actual 1.6l turbocharged Diesel with EGR during an EUDC driving cycle comparing honeycomb and foam catalysts. Results reported in the paper show the effects of these supports on pressure changes in intake and exhaust manifolds, on fuel consumption and on variations of catalyst temperatures during the considered transients