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The main challenge of the internal combustion engine industry is strongly related to the development of products that satisfy both the current and future legislation standards for pollutant emission and the increasing market demand for high efficiency energy solutions [1, 2]. In this sense, the usage of fuels such as natural gas and ethanol along with the development of high-efficiency combustion systems represent an important option to meet those requirements. In this study, three-dimensional numerical calculations were done considering a regular piston geometry and the AVL tri-flow® system. Three levels of swirl were generated during the intake stroke aiming to evaluate its influence over the flow features at spark timing, comparing the initial flame kernel development and flame front propagation.

A computational fluid dynamics (CFD) analysis of the M366LAG in-cylinder flow was performed to explain what are the reasons for the measured engine slower combustion which results from the replacement of the intake valve seat angle of 45° by 20°. Simulations showed that a quite different in-cylinder flow resulted from the different designs. The 20° geometry was found to generate a weaker turbulent field at the end of the compression stroke, specially around spark plug, which was identified as the cause of the slower combustion. The weaker turbulence is a result of a less coherent flow structure which is less capable of both storing the main flow kinetic energy until the compression stroke end and of taking advantage of squish to generate turbulence.