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Early injection strategies in the case of part-load conditions are offering the possibility to enhance mixing and evaporation. Due to the early injection, ignition and evaporation are separated in time and space for that less rich pockets from where soot is formed are occurring. For reducing NOx, cooled EGR is a method to dilute the intake charge. The combustion is shifted to lower temperatures and less NOx is formed. More, the cooling of the intake charge and the higher heat capacity enhance the evaporation time for that ignition starts at later times and combustion is retarded. For the simulation of such engine cases using high rates of EGR with an early fuel injection, a CFD (Computational Fluid Dynamics) code is coupled interactively with the flamelet model that will be applied here as combustion model. That approach, known as RIF (Representative Interactive Flamelet) model, requires a re-evaluation of the chemical reaction mechanism.

Recently developed computer models are being applied to calculate complex interactions between sprays and gas motions. The three- dimensional KIVA code was modified to address drop breakup and was used to study fuel sprays. The results show that drop breakup influences spray penetration, vaporization and mixing in high pressure sprays. The spray drop size is the outcome of a competition between drop breakup and drop coalescence phenomena, and the atomization details at the injector are lost during these size rearrangements. Drop breakup dominates in hollow-cone sprays because coalescence is minimized by the expanding spray geometry. The results imply that it may be possible to use a simple injector and still control spray drop size and vaporization if the flow details are modified so as to enhance drop breakup and coalescence.