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The objective of this paper is to present a simulation model for controlling combustion phasing in order to avoid knock in turbocharged SI engines. An empirically based knock model was integrated in a one-dimensional simulation tool. The empirical knock model was optimized and validated against engine tests for a variety of speeds and λ. This model can be used to optimize control strategies as well as design of new engine concepts. The model is able to predict knock onset with an accuracy of a few crank angle degrees. The phasing of the combustion provides information about optimal engine operating conditions.

A single cylinder Direct Injection Spark Ignition (DISI) engine with optical access has been used for combustion studies with both early injection and late injection for stratified charge operation. Cylinder pressure records have been used for combustion analysis that has been synchronised with the imaging. A high speed cine camera has been used for imaging combustion within a cycle, while a CCD camera has been used for imaging at fixed crank angles, so as to obtain information on cycle-by-cycle variations. The CCD images have also been analysed to give information on the quantity of soot present during combustion. Tests have been conducted with a reference unleaded gasoline (ULG), and pure fuel components: iso-octane (a representative alkane), and toluene (a representative aromatic). The results show diffusion-controlled combustion occurring in so-called homogeneous combustion with early injection.