CONICET | Buscador de Institutos y Recursos Humanos

Numerical and experimental techniques were applied in order to study the in-cylinderflow field in a commercial 4- valve spark ignition engine Fiat Torque. Investigation was focusedin analyze the generation and evolution of tumble-vortex structures during the intake andcompression strokes, and the capacity of this engine to promotes the turbulence enhancementduring tumble-vortex degradation, at the end of the compression stroke. For these purposes,three different approaches were developed. Firstly, static flow bench tests were experimentallycarried out, and these were reproduced by computational fluid dynamics (CFD) simulations.Once the numerical techniques were assessed, a dynamic simulation of the full engine cyclewas performed for several engine speeds (1500 rpm, 3000 rpm and 4500 rpm) without considerthe combustion (cold dynamic simulation). Static and dynamic cold-engine results werecompared in order to conclude about the significance of static-flow-test results to analyze thein-cylinder flow behavior. Finally, combustion was taken into account and the full-cycle engine simulation (hotdynamic simulation) was developed for the same three engine speeds. Combustionphenomenon was introduced as an in-cylinder homogeneous heat source. For this, a simplepredicting model was proposed in order to estimate the combustion rate as a function of themean in-cylinder flow conditions (temperature, pressure, turbulent intensity and geometry ofthe combustion chamber). In addition, to getting more realistic results, 0/1-dimensionalsimulations were performed in order to feed appropriate boundary conditions for CFDsimulations. All these results were employed to characterize the in-cylinder flow field of theengine, and at the same time, to conclude about the validity and usefulness of the differentengine tests (static flow tests, cold dynamic and hot dynamic simulation) to estimate the mean-flow characteristics of the engine.

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