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A visualization study using shadowgraphy was performed in an optically-accessible, cylindrical constant-volume combustion chamber to identify the mechanism of flow/flame interaction in spark-ignited, lean propane-air mixtures. The effect of the flow on flame initiation and propagation was examined by varying the pre-ignition mean flow and turbulence within a range typical of modern four-valve spark-ignition (SI) engines, as well as the spark plug orientation relative to the mean flow. The initial flame development was quantified in terms of 2-D images which provided information about the projected flame area and the displacement of the flame center as a function of flow conditions, time from the spark initiation and spark plug orientation. The results showed that high mean flow velocities and turbulence levels can shorten combustion duration in lean mixtures and that the positioning of the ground electrode can have an important effect on the initial kernel formation.

A diesel spray model has been developed and validated against experimental data obtained for different injection and surrounding gas conditions to allow investigation of the relative importance of the different physical processes occurring during the spray development. The model is based on the Eulerian-Lagrangian approximation and the Navier-Stokes equations, simulating the gas motion, are numerically solved on a collocated non-uniform curvilinear non-orthogonal grid, while the spray equation is solved numerically using a Lagrangian particle tracking method. The injection conditions are determined by another recently developed model calculating the flow in the fuel injection system, the sac volume and injection holes area which accounts for the details of the injection velocity, the fuel injection rate per injection hole and occurrence of hole cavitation. Thus, differences between the sprays from inclined multihole injectors can be simulated and analysed.

A new simulation approach to the modeling of the whole fuel injection process within a common-rail fuel injection system for direct-injection gasoline engines, including the pressure-swirl atomizer and the conical hollow-cone spray formed at the nozzle exit, is presented. The flow development in the common-rail fuel injection system is simulated using an 1-D model which accounts for the wave dynamics within the system and predicts the actual injection pressure and injection rate throughout the nozzle. The details of the flow inside its various flow passages and the discharge hole of the pressure-swirl atomizer are investigated using a two-phase CFD model which calculates the location of the liquid-gas interface using the VOF method and estimates the transient formation of the liquid film developing on the walls of the discharge hole due to the centrifugal forces acting on the swirling fluid.