Energy is one of the most important factors in each country. Renewable and sustainable energy resources have been and are nowadays the focus of many energy studies, since they provide a valid alternative to the conventional fossil fuels. Issues like the global warming, the increasing pollution worldwide and the depletion of fossil fuels reserves are increasingly moving the focus on the RES. Biodiesels and vegetable oils are the best candidate for the substitution of gasoline in internal combustion engines for stationary power generation applications. The main advantages of biofuels in ICEs are the lower CO, CO2, HC, smoke, soot and PM emissions. The main disadvantages of biofuels in ICEs derive from the high viscosity, high surface tension and low LHV. For these reasons, it is necessary to pre-treat the fuels in order to achieve characteristics similar to the diesel ones. In particular, preheating the fuel leads to a reduction of the viscosity and the surface tension, which means a better atomization and combustion process. The blending method between diesel and the biofuel provides a LHV similar to the diesel one. The viscosity of different biofuels and blends was measured in order to determine the proper range of preheating temperature at which the fuels were injected and burnt. The output data analyzed were the exhaust gases composition, i.e. the emissions, and in particular the NO emissions, the CO emissions, the oxygen content and the exhaust temperature. It was found that the vast majority of the results are in accordance with literature, that states the biofuels generally provide lower CO emissions and higher NO emissions than diesel fuel. Different preheating temperatures and different engine loads were adopted during each experiment. A model for the prediction of the kinematic and dynamic viscosity of VO-diesel blends with the variation of the vegetable oil content was formulated. Diesel, pure biodiesel, B50, VO30, VO50 and VO70 were analyzed through experiments with a 4-stroke 2-cylinder air-cooled diesel engine with direct injection. Furthermore, pure frying sunflower-palm vegetable oil, i.e. VO100, was studied through a model formulated on the basis of the previous experimental data. The results for VO100 are basically in agreement with the experiments and with the literature, hence it can be said that the assumptions used for the formulation of the model can be valid.
L’energia è uno dei fattori più importanti in ogni Paese. Le energie rinnovabili e sostenibili sono state e sono tuttora al centro di molti studi, poiché forniscono una valide alternativa ai combustibili fossili tradizionali. Problematiche come il riscaldamento globale, il crescente inquinamento nel mondo e l’esaurimento delle riserve dei combustibili fossili stanno sempre più muovendo l’attenzione sulle energie rinnovabili. I biodiesel e gli oli vegetali sono i migliori candidati per sostituire il gasolio nei motori a combustione interna per applicazioni stazionarie di generazione di potenza. I principali vantaggi dei biocombustibili in motori a combustione interna sono le ridotte emissioni di CO, CO2, HC, fumo, particolato carbonioso e polveri sottili. I principali svantaggi dei biocombustibili in motori a combustione interna derivano dall’elevata viscosità, dall’elevata tensione superficiale e dal basso potere calorifico inferiore. Per queste ragioni, è necessario pretrattare i combustibili per raggiungere caratteristiche simili al diesel. In particolare, preriscaldare il combustibile porta ad una riduzione della viscosità e della tensione superficiale, che si rispecchia in una migliore atomizzazione e combustione. Miscelare diesel e biocombustibile genera un potere calorifico inferiore simile a quello del gasolio. La viscosità di diversi biocombustibili e miscele è stata misurata per determinare un range adeguato di temperatura di preriscaldamento alle quali i combustibili sono stati iniettati e bruciati. I dati analizzati in output riguardavano la composizione dei gas combusti, e in particolare sono stati misurati le emissioni di NO, CO, il contenuto di ossigeno e la temperatura. E’ stato trovato che la maggior parte dei risultati sono in accordo con la letteratura, cioè che i biocombustibili forniscono generalmente emissioni di CO minori ed emissioni di NO maggiori rispetto al diesel. Diverse temperature di preriscaldamento e diversi carichi del motore sono stati adottati durante ogni esperimento. Un modello per la previsione della viscosità dinamica e cinematica di miscele tra diesel e olio vegetale, in base al contenuto di olio vegetale nella miscela, è stato formulato. Diesel, biodiesel, miscela B50, VO30, VO50 e VO70 sono stati analizzati attraverso esperimenti in un motore diesel a 4 tempi, 2 cilindri, ad iniezione diretta e raffreddato ad aria. Inoltre, l’olio vegetale puro di girasole di palma, cioè VO100, è stato studiato attraverso un modello formulato sulla base dei precedenti dati sperimentali. I risultati per il VO100 sono in accordo con gli esperimenti e con la letteratura, quindi è possibile dire che le assunzioni utilizzate per la formulazione del modello sono valide.
Atomization and combustion of viscous biofuels in a Diesel engine
BETTINELLI, MATTEO
2016/2017
Abstract
Energy is one of the most important factors in each country. Renewable and sustainable energy resources have been and are nowadays the focus of many energy studies, since they provide a valid alternative to the conventional fossil fuels. Issues like the global warming, the increasing pollution worldwide and the depletion of fossil fuels reserves are increasingly moving the focus on the RES. Biodiesels and vegetable oils are the best candidate for the substitution of gasoline in internal combustion engines for stationary power generation applications. The main advantages of biofuels in ICEs are the lower CO, CO2, HC, smoke, soot and PM emissions. The main disadvantages of biofuels in ICEs derive from the high viscosity, high surface tension and low LHV. For these reasons, it is necessary to pre-treat the fuels in order to achieve characteristics similar to the diesel ones. In particular, preheating the fuel leads to a reduction of the viscosity and the surface tension, which means a better atomization and combustion process. The blending method between diesel and the biofuel provides a LHV similar to the diesel one. The viscosity of different biofuels and blends was measured in order to determine the proper range of preheating temperature at which the fuels were injected and burnt. The output data analyzed were the exhaust gases composition, i.e. the emissions, and in particular the NO emissions, the CO emissions, the oxygen content and the exhaust temperature. It was found that the vast majority of the results are in accordance with literature, that states the biofuels generally provide lower CO emissions and higher NO emissions than diesel fuel. Different preheating temperatures and different engine loads were adopted during each experiment. A model for the prediction of the kinematic and dynamic viscosity of VO-diesel blends with the variation of the vegetable oil content was formulated. Diesel, pure biodiesel, B50, VO30, VO50 and VO70 were analyzed through experiments with a 4-stroke 2-cylinder air-cooled diesel engine with direct injection. Furthermore, pure frying sunflower-palm vegetable oil, i.e. VO100, was studied through a model formulated on the basis of the previous experimental data. The results for VO100 are basically in agreement with the experiments and with the literature, hence it can be said that the assumptions used for the formulation of the model can be valid.| File | Dimensione | Formato | |
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Atomization and combustion of viscous biofuels in a diesel engine - Matteo Bettinelli.pdf
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https://hdl.handle.net/10589/137694