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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.

A promising strategy for increasing thermal efficiency and decreasing emissions of a spark ignited (SI) internal combustion engine is the application of lean mixtures. The flammability limit of lean mixtures can be increased by using an active pre-chamber containing an injector and a spark plug, resulting in a combustion mode commonly called Turbulent Jet Ignition (TJI). The optimization of the combustion chamber shape and operating parameters for TJI combustion can be a demanding task, since the number of design parameters is significantly increased and is today supported by numerical simulations. In this paper, the process of the development of a numerical framework based on 3D CFD and 1D/0D numerical models that will support the research of the pre-chamber design and optimization of operating parameters will be shown. For 3D CFD modelling the AVL Fire™ code is employed, where the full combustion chamber model with intake and exhaust ports of the experimental engine is prepared.

It is a well-known fact that HCCI combustion offers the possibility of achieving high efficiency with low emissions, but with the challenges in combustion control and ability to adjust to changing environmental conditions. To resolve the aforementioned challenges, a pre-chamber induced homogeneous charge compression ignition (PC-HCCI) combustion mode was experimentally tested with aim of providing initial operating boundaries in terms of combustion stability and obtaining initial performance results. The single cylinder engine equipped with active pre-chamber and compression ratio (CR) of 17.5 was fueled by gasoline. The initial experiments were performed at the engine speed of 1600 rpm with intake air temperatures varied from 33°C to 100°C to verify the possibility of achieving the PC-HCCI combustion mode and to compare the achieved engine performance and emission results with both PCSI and pure HCCI combustion modes used as reference cases.

Advanced combustion concepts that rely on the lean-burn approach are a proven solution for increasing the efficiency and reducing the harmful emissions of SI engines. The pre-chamber spark ignited (PCSI) engines utilize high ignition energy of the multiple jets penetrating from the pre-chamber, to enable fast and stable combustion of lean mixture in the main chamber. The combustion is still governed by the flame propagation, so the dilution level and efficiency benefits are highly restricted by strong decrease of laminar flame speeds. Homogeneous charge compression ignition (HCCI) combustion allows a higher dilution level due to rapid chemically driven combustion, however the inability to directly control the ignition timing has proven to be a major setback in HCCI deployment.