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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.

Nowadays, the main potential of the HCCI engine, i.e. high efficiency with low NOx and soot emissions, is a well-known fact. Main limitations that prevent the commercial application of the HCCI engine are the control of combustion timing and low power density. Higher power density could be achieved by boosting the engine, but low exhaust temperatures associated with the HCCI combustion require a different approach when trying to achieve a boosted HCCI engine. This paper presents a numerical study on two boosting configurations that will enable high boost levels and high load, as a consequence, in the Ethanol fueled HCCI engine, in the engine speed range of 1000 - 4000 rpm. For the purposes of this study, a four-cylinder HCCI engine model has been made in the cycle-simulation software. The model includes the entire engine geometry and all elements necessary for representing the entire engine flow path.

In the paper the operation of a turbocharged dual fuel engine at mid-high load is investigated on a single cylinder experimental engine complemented by a full 0D/1D simulation model that provides boundary conditions for the experiment and full engine system results. When duel fuel combustion mode is used on a turbocharged engine with the variable geometry turbocharger, the mid-high load operating points can be obtained with number of different combinations of intake pressure and excess air ratio. Besides the impact on combustion, the specific combination of intake pressure - excess air ratio has also impact on the exhaust back pressure caused by the turbocharger and consequently on the obtained brake efficiency. Additionally, the dual fuel combustion is influenced by natural gas mass fraction and start of injection of diesel fuel and the search for the optimal solution could be a challenging task.