Investigation of the flow field in a single-cylinder spark ignition engine using OpenFOAM

In Internal combustion Engines research field, numerical investigations have become widespread in the last decades and have contributed to recent state of the art of modern engines. Indeed, they have the potential to capture the in-cylinder turbulence, which is at the basis of any combustion phenomena.In-cylinder flow field is fundamental and it contributes to the engine efficiency and performance. The present thesis work describes the numerical investigation of the flow field in a motored four strokes, single-cylinder optical research engine, adding a preliminary study on fired case as well. Qualitative and quantitative comparisons between experimental and numerical data have been performed at selected crank angles. In order to investigate the velocity field, describing the engine flow structure, three consequently full-cycle Large Eddy Simulation (LES) were carried out, using only one mesh resolution. The adopted modeling framework has covered every steps, starting from pre-processing (stl and mesh generation) and ending with post-processing, necessary for the evaluation of the results with experimental data. Several inconsistencies have been observed, in particular in the momentum of velocity components. Although this result can be mainly attributed to the limited number of statistical sample collected during the simulations (only three full-cycle simulations), further multi-cycles investigation is certainly necessary to assess the accuracy and validity of the numerical tool and spatial resolution issues.

Il framework di modellazione adottato ha coperto ogni fase, a partire dalla pre-elaborazione (generazione di stl e mesh) e termina con la post-elaborazione, necessaria per la valutazione dei risultati con dati sperimentali. Sono state osservate diverse incongruenze, in particolare nella quantità di moto dei componenti della velocità. Sebbene questo risultato possa essere principalmente attribuito al numero limitato di dati raccolti durante le simulazioni (solo tre simulazioni a ciclo completo consecutivi), ulteriori indagini su più cicli sono certamente necessarie per valutare l'accuratezza e la validità dello strumento numerico e dei problemi di risoluzione spaziale.