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The quest for high efficient internal combustion engines has intensified in the last years due to, among other reasons, increasing fuel costs and the pressure to reduce environmental deterioration. One of the possible alternatives capable of providing the sought efficiency gains is the recovery of the energy wasted in the exhaust gases and turbo-compounding is one obvious option. Compression ignition engines are usually the target of turbo-compounding, however, the rising interest for alternative fuels could result in the use of turbo-compounding for spark ignition engines as well. Due to its different flame propagation mechanism, spark ignition engines may force operation at higher fuel-air ratios, eventually creating a quite distinctive operational behavior.

The fuel injection in internal combustion engines plays a crucial role in the mixture formation, combustion process and pollutants' emission. Its correct modeling is fundamental to the prediction of an engine performance through a computational fluid dynamics simulation. In the first part of this work a tridimensional numerical simulation of a multi-hole’s injector, using ethanol as fuel, is presented. The numerical simulation results were compared to experimental data from a fuel spray injection bench test in a quiescent vessel. The break up model applied to the simulation was the combined Kelvin-Helmholtz Rayleigh-Taylor, and a sensitivity analysis of the liquid fuel penetration curve, as well on the overall spray shape was performed according to the model constants. Experimental spray images were used to aid the model tuning. The final configuration of the KH-RT model constants that showed best agreement with the measured spray was C3 equal to 0.5, B1, 7 and Cb, 0.