|Tipo di tesi||Tesi di dottorato di ricerca|
|Titolo||Modellazione avanzata di flussi reagenti all'interno dei motori a combustione interna|
|Titolo in inglese||Advanced modeling of the combustion process in internal combustion engines|
|Settore scientifico disciplinare||ING-IND/08 - MACCHINE A FLUIDO|
|Corso di studi||Scuola di D.R. in HIGH MECHANICS AND AUTOMOTIVE DESIGN & TECHNOLOGY / MECCANICA AVANZATA E TECNICA DEL VEICOLO|
|Data inizio appello||2013-03-22|
|Disponibilità||Accessibile via web (tutti i file della tesi sono accessibili)|
L’attività di ricerca svolta è stata caratterizzata dallo studio della modellazione fluidodinamica tridimensionale dei principali fenomeni che coinvolgono flussi reagenti nei motori a combustione interna. Il fine principale è stato quello di determinare la corretta evoluzione fisica, spaziale e temporale, di tali flussi all’interno dei motori per favorire la corretta interpretazione dei fenomeni chimico-fisici e la predizione delle prestazioni dei motori.
The proposed research activity focuses on the modeling of the phenomena involved during the combustion process in internal combustion engines. In recent years, increasingly stricter anti-pollution regulations have addressed the research and development of internal combustion engines towards much more environmentally-friendly spark and compression -ignited engines. In order to meet the new anti-pollution requirements, different strategies based on innovative injection systems and combustion processes or alternative fuels are studied: much more complex chemistry mechanisms are now involved and this implies the need to address the problem in a more sophisticated way from a numerical point of view. In a scenario like this, detailed CFD analyses are used to accurately model the complex set of physical and chemical processes and to properly estimate the fluid-dynamic behavior of the engine, which is otherwise difficult to be experimentally determined. The analyses are carried out on two- and four- stroke engines fuelled both with conventional and alternative fuels: this aiming at generalizing the modeling approach respect to the combustion modes and the specific engine / fuel analyzed. Because of the influence that in-cylinder large scale and small scale turbulent structures have in the mixing process and subsequently in the combustion process and in the pollutant emissions, the flow motion during the intake and compression strokes is at first investigated. In order to assess the accuracy of the adopted numerical approach, comparisons between simulation forecasts and experimental measurements of instantaneous in-cylinder pressure history for steady-state operations of the engine are then performed and discussed. A combined numerical and experimental activity aiming at characterizing the behavior of a small displacement SI 2-stroke engine fuelled with gasoline and Natural Gas is reported in order to investigate the potential benefits due to the use of a “greener” fuel. Numerical tools are used to investigate the early stages of the flame kernel development, the propagation of the flame front and its interaction with the in-cylinder flow-field. The knock limit of the gasoline-fuelled and CNG-fuelled engines is finally investigated under much more critical operating conditions. With reference to a 4-stroke diesel- fuelled engine, the influence of the ignition delay and the effect of the interaction between in-cylinder turbulence and spray turbulence on the development of combustion is investigated.