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Title: Theoretical and experimental investigation of n-butanol combustion
Author: Katsikadakos, Dimitrios
ISNI:       0000 0004 2737 7529
Awarding Body: Imperial College London
Current Institution: Imperial College London
Date of Award: 2013
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Biofuels, are attracting great interest as an alternative to fossil fuels. n-Butanol has surfaced as a potential biofuel, mainly because it does not suffer from the drawbacks, that the current most widely used biofuel, ethanol, does. In this work a theoretical and experimental investigation of n-butanol combustion is performed, while a baseline investigation of fundamental combustion properties of methane is carried out. The computational work involves the investigation of the various reaction pathways for hydrogen abstraction from n-butanol by CH3 using quantum chemical calculations. The relative significance of hydrogen abstraction reactions from the specific carbon sites of n-butanol are compared with each other and with similar radical reactions initiated by OH and HO2 radicals. While the most stable structural conformer of n-butanol is expected to be the most abundant during the combustion process, the temperatures at which fuel burns, allow higher energy conformers to be accessible. A key feature of this work is to assess if any of these low lying, but not minimum energy conformers, have transition state barriers or product radicals lower in energy than those found for the most stable conformer. Based on the above ab initio calculations the rate constants and product branching ratios for hydrogen abstraction by CH3 from the different sites of n-butanol are computed using three available kinetic programs, namely CanTherm, MultiWell and Variflex, providing accurate data for future detail chemistry mechanism of n-butanol. An exhaustive comparison of the aforementioned kinetic programs is also carried out. The experimental work involves the development of a counterflow burner, specifically designed for the study of flames of pre-vaporised liquid fuels, which provides a very useful idealisation of the combustion process of a real combustor. While the present research focuses on n-butanol combustion, measurements of methane flames are used as a starting point of the experimental work, providing a basic understanding of the combustion aspects under investigation. The natural chemiluminescence of OH* and CH* radicals emitted in preheated premixed methane and n-butanol flames are measured using intensified high speed photography, in order to evaluate the dependence of the chemiluminescent ratio OH*/CH* on equivalence ratio and strain rate for various preheat gas temperatures and the performance of available chemical kinetics mechanisms. The effect of an electric field in counterflow flames is also investigated focusing on two principal themes: the effect of strain rate on the saturation current and the effect of high potential fields on the OH* chemiluminescence.
Supervisor: Hardalupas, Yannis ; Hunt, Patricia ; Taylor, Alex Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available