The emissions and chemical autoignition delay of biodiesel fuel.
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Date
2013
Authors
Boyd, Marcus William
Editors
Advisors
Doolan, Con
Kestell, Colin David
Kestell, Colin David
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Thesis
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Abstract
Biodiesel is an alternative to diesel fuel that can reduce life-cycle greenhouse emissions. It is made from plant oils or waste animal fat. Changing an engine's fuel from #2 diesel to biodiesel does not require modifications to the engine, and has typically reduced emissions of particulate matter (PM) but increased nitrogen oxides (NOₓ). However, government regulations tightly limit exhaust pollutants, hence the increase is problematic. In order to investigate the relationship between biodiesel fuel, ignition delay and emissions, experiments with a compression ignition, direct injection (CIDI) engine were performed. The emissions, ignition delays and apparent heat release rates from four locally produced biodiesel fuels and #2 diesel were measured. Emissions of NOₓ were greater on average from the biodiesel fuels than the #2 diesel. Emissions of PM were not consistent, and measurements of ignition delay were the opposite of expectations. It was postulated that the fuel was undergoing atypical combustion, but this could not be confirmed with the limited data available from this investigation technique. The engine experiments exemplified the need for alternative investigation techniques and numerical simulation of CIDI combustion was the leading choice. This technique was already well developed, however chemical ignition delay models for #2 diesel had received little validation and no data existed to generate a biodiesel chemical ignition delay model. The novel drop method was conceived to measure the chemical ignition delay of heavy fuels at CIDI combustion relevant conditions and a shock tube was designed and built to use this method. It combusted fuel in a heterogeneous environment and minimised pre-experiment reactions. It was validated with n-dodecane, which indicated an assumed equivalence ratio at the ignition point was required. It then produced the first measurements of the chemical ignition delay of methyl oleate (a biodiesel surrogate) and #2 diesel at CIDI relevant conditions without pre-experimental reactions. Methyl oleate generated shorter chemical ignition delays than diesel and displayed NTC behaviour. The drop method shows strong potential for future measurements of the chemical ignition delay of many different heavy fuels.
School/Discipline
School of Mechanical Engineering
Dissertation Note
Thesis (Ph.D.) -- University of Adelaide, School of Mechanical Engineering, 2013
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Copyright material removed from digital thesis. See print copy in University of Adelaide Library for full text.