Abstract
The object of study of the following thesis concerns the study of SACI combustion using a CFD software. Starting from the analysis of the European homologation cycles and from the innovative technological strategies aimed at reducing the pollutants emitted by the vehicles, the purpose of the experimental activity is to investigate the physics of advanced combustions, such as Low Temperature Combustions (LTC), which represent an alternative way to reduce the pollutant emissions while enhancing the engine efficiency. In particular, the objective is to determine the favorable conditions in terms of air motion and injection timing that would allow the implementation of a SACI-type combustion. Following the patent provided by Mazda regarding the same technology, only one engine point to investigate is chosen: 1500 rpm and 8 bar BMEP. The analysis of the problem is then approached through a preliminary study on the initial and boundary conditions of the intake and exhaust systems using the OpenWAM opensource software. Subsequently, the same conditions obtained are applied in the 3-D CFD AVL Fire software. The aim is to create a stratified charge through the interaction between air motion and injection strategy. After verifying the effective stratification and stability of the mixture around the spark plug through PDF analysis, the research proceeds studying the implementation of EGR to favor the self-combustion of the peripheral regions and to lower the average temperature of the cylinder during combustion itself, so to reduce the formation of NOx and PM. As a last step, the combustion analysis is carried out by exposing its characteristic indices.
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