Carbon neutrality goals are pushing the research towards the study of electrification and alternative fuels, to keep global warming under a safety level. In this work the focus is on methanol as a fuel for large marine vessels, since it is a field where it is impossible to have an electric propulsion due to the large power request. Two studies are conducted using the CFD technology: the combustion in a large two stroke compression ignition marine engine and the behaviour of a non-reactive high pressure spray. In both cases the software used to run the simulations is OpenFOAM, to which is added the LibICE code, developed by the Internal Combustion Engine group at Politecnico di Milano. After a short description of the main characteristics of methanol and of the numerical code, the engine simulations are described: first, the study of the single fuel combustion using only diesel, used to find the proper engine simulation setup since some experimental data for a comparison were available. Then the dual fuel configuration, with a mixture of methanol and lignin oil as the main fuel and diesel as the pilot injection, which results will be compared with the single fuel case. After that, the study of the non-reactive spray in a constant volume vessel is shown, with the results for different injection directions and the investigation of a limit injection angle allowing to have a stable jet. Some interesting conclusions are drawn at the end of this work, but future developments are possible, going deeper and expanding the study of both combustion and fuel spray to other alternative fuels.
L’obiettivo della neutralità carbonica sta spingendo la ricerca verso lo studio dell’elettrificazione e dei carburanti alternativi come metodo per mantenere il riscaldamento globale al di sotto del livello di allarme. In questo lavoro di tesi l’attenzione è posta sul metanolo come carburante per grandi navi, dato che in questo settore non è possibile avere una propulsione elettrica a causa della grande potenza necessaria. Sono stati condotti due studi usando la tecnologia CFD: la combustione diffusiva in un grosso motore marino a due tempi e il comportamento dello spray non reagente iniettato ad alta pressione. In entrambi i casi è stato usato il software OpenFOAM per le simulazioni, a cui è stata aggiunta la LibICE, un codice sviluppato dal gruppo di Motori a Combustione Interna del Politecnico di Milano. Dopo una breve descrizione delle principali caratteristiche del metanolo e del codice numerico, vengono illustrati i risultati delle simulazioni del motore: prima con una configurazione in cui viene bruciato unicamente gasolio, usata per cercare il setup ottimale grazie alla disponibilità di dati sperimentali con cui confrontare i risultati delle simulazioni. In seguito si descrive la configurazione dual fuel, in cui viene usata una miscela di metanolo e olio di lignina come carburante principale e gasolio come ausiliario, che verrà confrontata con il caso diesel. Infine viene studiato il comportamento dello spray di metanolo non reagente in un dominio a volume costante, con diverse direzioni di iniezione. Viene inoltre cercato l’angolo di iniezione limite che permetta di avere un getto stabile. A valle di questi studi si possono trarre alcune interessanti conclusioni, ma sono possibili ulteriori sviluppi, approfondendo ed ampliando la ricerca ad altri carburanti alternativi.
CFD combustion modelling of marine two stroke engines operating with conventional and alternative fuels
FOGLIO, SABRINA
2022/2023
Abstract
Carbon neutrality goals are pushing the research towards the study of electrification and alternative fuels, to keep global warming under a safety level. In this work the focus is on methanol as a fuel for large marine vessels, since it is a field where it is impossible to have an electric propulsion due to the large power request. Two studies are conducted using the CFD technology: the combustion in a large two stroke compression ignition marine engine and the behaviour of a non-reactive high pressure spray. In both cases the software used to run the simulations is OpenFOAM, to which is added the LibICE code, developed by the Internal Combustion Engine group at Politecnico di Milano. After a short description of the main characteristics of methanol and of the numerical code, the engine simulations are described: first, the study of the single fuel combustion using only diesel, used to find the proper engine simulation setup since some experimental data for a comparison were available. Then the dual fuel configuration, with a mixture of methanol and lignin oil as the main fuel and diesel as the pilot injection, which results will be compared with the single fuel case. After that, the study of the non-reactive spray in a constant volume vessel is shown, with the results for different injection directions and the investigation of a limit injection angle allowing to have a stable jet. Some interesting conclusions are drawn at the end of this work, but future developments are possible, going deeper and expanding the study of both combustion and fuel spray to other alternative fuels.File | Dimensione | Formato | |
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2023_10_Foglio_Tesi_01.pdf
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Descrizione: Testo della Tesi
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2023_10_Foglio_Executive Summary_02.pdf
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Descrizione: Executive Summary
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2.17 MB
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2.17 MB | Adobe PDF | Visualizza/Apri |
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https://hdl.handle.net/10589/210104