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Development of SI engines to further increase engine efficiency is strongly affected by the occurrence of engine knock. Engine knock has been widely investigated over the years and the main promoting parameters have been identified as load (temperature and pressure), mixture composition, engine speed, characteristic of the fuel, combustion chamber design, and etc. In this paper a new model for predicting engine knock in 0-D environment is presented. The model is based on the well-known approach of using a Livengood and Wu knock integral. Ignition delay data that are supplied to the knock integral are for specific fuel calculated by detail chemical kinetics and are comprised of low temperature heat release ignition delay and high temperature heat release ignition delay. Next, the cycle to cycle variations of engine and temperature stratification of the end gas have to be taken into account.

The paper presents modeling of cycle-to-cycle variations (CCV) of a SI engine by using the modified cycle-simulation model. The presented research has been performed on CFR engine fueled by gasoline. Experimental in-cylinder pressure traces of 300 cycles have been processed for several operating points representing the spark sweep which captured the operating points with low and high CCV. The cycle-simulation model applied in this study uses significantly improved turbulence and combustion model that have been implemented into the cycle-simulation code. Developed k-ε turbulence model and the quasi-dimensional combustion model based on the fractal theory have been applied.