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The internal mixture formation by gasoline direct injection offers a remarkable potential to improve the engine performances and to reduce the pollutant emission, due to the large possibilities of process control. On the other hand, the control mechanisms their selves are more complex and sensitive at speed or load variations than the ones used for external mixture formation. The spray characteristics, as well as the shape of injection rate have to be accurately adapted to every condition of load, speed and surrounding. This paper presents a method for the effective optimization of GDI techniques for SI engines, which is exemplified by a system with direct injection by high pressure modulation. The method is based on the interactive optimization of the processes within the injection system respectively during the spray evolution, by a feed-back strategy between separate numerical simulations of both processes.

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 application of supercharging as a measure to improve the engine performances is a basic feature for downsizing concepts applied for advanced automobile engines. The adaptation of such concept to a high speed compact SI engine with a speed range between 2.000rpm and 9.000rpm forms the object of this paper. The determination of the special adapted control strategy as well as the necessary modifications of the basic engine were conducted in this work by mean of simulation with the 1D Code BOOST and coupled modules from 3D simulation by the code FIRE. The used models were generated and calibrated going out from the individual components to be connected: an 1000cc/2 cylinder/4 stroke engine and a screw type compressor. The adaptation of the engine to the supercharging concept, imposed modifications of the valve course and timing as well as of the intake ducts shaping.