Abstract
In the automotive industry, today's major objectives concern the reduction of pollutant emissions and fuel consumption while improving performance and driveability. For this purpose, during the last decade, the classical engine has evolved towards a very complex system combining many hi-tech components with advanced control strategies. Optimising the whole engine system and controlling its behaviour has then become a real challenge for car manufacturers. In this context, powertrain simulation tools have been shown to provide an undisputable support during all stages of engine development from concept design to control strategies development and calibration. However these tools require sophisticated models to be efficient, especially in the combustion chamber where combustion and pollutant formation processes take place. This paper presents a 0D physical combustion model devoted to the prediction of heat release and pollutants in SI engines. The originality of this model derives from the fact it is based on the reduction of the 3D CFD E-CFM (Extended Coherent Flame Model) model developed at IFP [1]. The CFM formalism distinguishes two zones : the fresh and the burnt gases, which are separated by a flame front and are both described by their temperature, mass and composition. The proposed model is an important evolution of the CFM-1D model previously published in [2]. It computes the rate of consumption of the fresh gases and is based on the calculation of the flame front surface using the real engine geometry and a 0D derivation of the flame surface density approach. Pollutants (CO and NO_x) are computed both through the flame front and within the burnt gases using a reduced kinetic scheme and a classical extended Zel'dovitch mechanism. The whole model is validated against experimental data at several steady state operating points for two engine configurations. A good agreement with experiments is observed for both configurations, showing the interest of reducing 3D CFD models to build predictive 0D models for engine system simulations.
