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The adoption of high compression ratios when designing an internal combustion engine is often used to improve thermal efficiency. However, compression ratio cannot be enhanced indefinitely since elevated pressures and temperatures inside the combustion chamber may cause knock. In view of this issue, it is important to have an accurate knowledge about the conditions in which the probability of knock occurrence is high to preserve engine integrity and achieve the best performance. In addition, if numerical tools are available for this type of analysis, time and experimentation costs can be avoided. Based on this idea, this paper presents a numerical tridimensional study of knock occurrence in a spark ignition three-cylinder engine operating with different compression ratios and late intake valve closing.

A CFD three-dimensional analysis of an internal combustion engine was carried out to evaluate the gasoline-ethanol E27 fuel spray and flow characteristics using variable valve timing (VVT) technology. In this study, the fuel injection has been made using port fuel injection (PFI) and the simulations modeled two conditions of valve timing: baseline and retarding the intake valve opening (IVO) 40°. The dynamic performance of this numerical model was validated comparing simulation results of cylinder pressure, mass burned fraction, cylinder temperature, and heat release with experimental data. The effects of in-cylinder fluid flow patterns, such as tumble and swirl, on combustion were numerically investigated for the two studied conditions and it was verified an extreme reduction of swirl when IVO is retarded, besides differences in tumble and cross-tumble.

Atomization parameters from the spray produced by a direct injection injector, operating into an engine with optical access were analyzed in this work. Parameters such as cone angle, penetration and spray geometry for determined crank angles and different rotations, with the respective variability, were evaluated for ethanol injection. Images from spray injection were captured for the specified rotation conditions for the angle and geometry analysis. For the penetration analysis, the image acquisition occurred with crank angle variation, obtaining a mean value with respect to the spray displacement of a point of maximum concentration on a specified direction. Lines were adjusted to the penetration data and the penetration rates (velocities) were evaluated through its slopes. For the cone angle and geometry study, an automatic routine in Matlab environment for image processing was used.

Fulfill emission restrictions is the most challenging task of future engines development. In this context, improvements with regard to the spray and mixture formation in internal combustion engines are necessary. Experimental investigation and numerical simulation have been used to predict and analyze complex in cylinder processes. In this paper, a diesel spray characterization using optical diagnostics was made in order to provide input data and boundary conditions for a diesel spray computational fluid dynamics simulation (CFD), using the Eulerian-Lagrangian model. Combining the advantages of Eulerian and Lagrangian approaches, this model is able to predict continuously the whole spray evolution. The main difficulty of numerical spray simulation is the correct representation of the two characteristic spray zones: dense near the nozzle and dilute downstream.