Particularities of Combustion in Direct Injection Spark Ignition Engines 2001-01-0249

The development of advanced techniques for an improved control of scavenging, mixture formation and thereby of the combustion in IC engines is more and more supported by numerical simulation models. However, the benefits in reducing the specific fuel consumption and the pollutant emission are not spectacular. On the other hand, the recent evolution of the fuel cell systems - which let expect a commercial application for automotive propulsion in the next years - demonstrates a remarkable efficiency. There appears a challenge for the IC engines, considering the utilization of similar energetic sources for both systems. This imposes an accelerated optimization of the processes in thermal engines - the central problem being the control of combustion. In this context, the basic models should be reconsidered. The paper presents and discuss the specific aspects of advanced mixture formation techniques by direct injection in SI engines, which could form the base of new combustion models - as initial configuration of numerical simulation. The main specific aspects for more realistic modeling are the non homogeneity of components and phases during mixture formation, the mixture structure depending on load and speed, the partially superposed processes of mixture formation and combustion, the complex heat transfer in different zones, the controlled autoignition process as well as multifuel applications.