De Robbio, Roberta (2020) CFD study of diesel engine operating in dual fuel mode. [Tesi di dottorato]

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Tipologia del documento:	Tesi di dottorato
Lingua:	English
Titolo:	CFD study of diesel engine operating in dual fuel mode
Autori:	Autore Email De Robbio, Roberta roberta.derobbio@unina.it
Data:	13 Marzo 2020
Numero di pagine:	256
Istituzione:	Università degli Studi di Napoli Federico II
Dipartimento:	Ingegneria Industriale
Dottorato:	Ingegneria industriale
Ciclo di dottorato:	32
Coordinatore del Corso di dottorato:	nome email Grassi, Michele michele.grassi@unina.it
Tutor:	nome email Tuccillo, Raffaele [non definito] Cameretti, Maria Cristina [non definito]
Data:	13 Marzo 2020
Numero di pagine:	256
Parole chiave:	CFD; Diesel Engine; Dual Fuel; Combustion
Settori scientifico-disciplinari del MIUR:	Area 09 - Ingegneria industriale e dell'informazione > ING-IND/08 - Macchine a fluido
Depositato il:	02 Apr 2020 08:08
Ultima modifica:	08 Nov 2021 11:57
URI:	http://www.fedoa.unina.it/id/eprint/13170

Abstract

In the last years climate change has become an emergency that united countries of the world to make agreements to reduce pollutant emissions. In this context, the diesel engine, whose combustion is characterised by high emissions of particulate matter and nitric oxides, is likely to disappear from the future automotive market. However, the high performances of this well established engine may still represent a resource in terms of power, efficiency and reliability. In this regard, a possible solution is to readapt the engine to operate in Dual Fuel mode. In order to assess the benefits and limits of this technology, it is necessary a deep investigation of the phenomena that characterise the combustion development that results further complicated, due to the interaction of two burning fuels. To this purpose, Computational Fluid Dynamics is the most powerful tool allowing investigation of the different processes that take place inside the cylinder such as turbulence, fuel atomisation and chemical kinetics. Clearly, major difficulties are encountered in the choice of a combustion model suitable for both fuels. In this regard, kinetics plays a key role in the description of the oxidation process. This thesis aimed at a progressive improvement of the methodology and more detailed kinetic mechanism were utilised to better comprehend the actual combustion mechanism and pollutants formation. Starting from a simplified kinetics scheme for diesel oil and natural gas oxidation, firstly a new mechanism including 9 reactions was introduced for the ignition of methane (considered as the main component of natural gas), in this way it was possible to release from empirical correlations for the ignition of at least one of the two fuels. Finally, this model was compared with a more detailed scheme consisting of 100 species and 432 reactions. Further criticalities arise from the wide operating range of the engine, especially for automotive applications. To overcome the typical problem related to the computational cost of the CFD based approach, the utilisation of different tools such as a one-dimensional model demonstrated to be helpful for extending the numerical investigations to multiple cases characterised by either different load levels or changes in the fuel injection settings. In this framework the experimental activity represented an effective tool for the validation of the numerical outcomes, since experimental data provided important information on the behaviour of three distinct diesel engines, say: a light-duty common rail engine, an optically accessible research engine and a heavy-duty engine. The main point to be highlighted is that the study of three engines with different characteristics allowed a wide investigation on different operating conditions.

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