No description available.

No description available.

Thesis (M.S.)--University of Missouri-Columbia, 2006. / The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file viewed on (February 23, 2007) Includes bibliographical references.

Thesis (M. Phil.)--University of Hong Kong, 2001. / Includes bibliographical references (leaves 72-80).

Because of the depletion of the world’s petroleum reserves and the increasing environmental concerns, biodiesel, as a low-emission renewable fuel and one of the best substitutes for petro-diesel fuel, has attracted great public interest over the past decades. At present, camelina oil has been considered as a low-cost feedstock for biodiesel production because of its high oil content and environmental benefits. In the present study, the optimization of biodiesel production and purification from camelina oil is studied extensively in order to maximize the biodiesel yield. The orthogonal array design is used to optimize the biodiesel production and four relevant process conditions for affecting biodiesel yield are investigated: methanol to oil ratio, catalyst concentration, reaction time and temperature. For the optimization study on biodiesel purification, five commonly used washing methods are also investigated: cold deionized water washing, hot deionized water washing, phosphoric acid washing, ultrasonic assisted washing, and magnesol washing. The optimization study, based on traditional mechanical stirring process, reveals that the decreasing ranking of significant factors for biodiesel production is catalyst concentration > reaction time > reaction temperature > methanol to oil ratio. The maximum biodiesel yield is found at a molar ratio of methanol to oil of 8:1, a reaction time of 70 min, a reaction temperature of 50℃, and a catalyst concentration of 1 wt.%. After testing the fuel properties of the final product, the optimized biodiesel meets the relevant requirements of the biodiesel standards and thus can be used as a qualified fuel for diesel engines. The optimization study, based on ultrasonic-assisted transesterification process, reveals that the maximal fatty acid methyl ester yield of the final biodiesel product is obtained under a methanol to oil molar ratio of 8:1, catalyst concentration of 1.25 wt.%, reaction time of 50 min and reaction temperature of 55 ℃. Compared with traditional mechanical stirring production process, ultrasonic-assisted transesterification process improves the biodiesel production since it could reduce the production cost and save energy. For the optimization study on biodiesel purification, the fatty acid methyl ester yield of the final biodiesel product, energy consumption and economic costs of different washing methods are compared. The comparisons indicate that the ultrasonic assisted washing method is the best method for biodiesel purification, when energy consumption and operation costs are considered. A preliminary kinetics study of transesterification reaction of camelina oil is carried out. After discussing four cases for overall reaction, a third-order reaction mechanism was proposed to fit the experimental data better because of the highest coefficient of determination. Based on the best-fit plot, the rate constants and activation energy are also determined. To sum up, the present research focuses on the optimization of biodiesel production and purification from camelina oil, and provides insights into the optimal process conditions for maximizing the biodiesel yield. Further research works are finally recommended to be continued. / published_or_final_version / Mechanical Engineering / Doctoral / Doctor of Philosophy

The production of biomass based fuels has long been advocated as a means of utilising solar energy for power generation. The present concern over global warming through the accumulation of carbon dioxide produced from the combustion of fossil fuels gives a further impetus to the consideration of these alternative fuels. They are renewable and photo-synthetically assist to recycle the carbon dioxide they produce on combustion. In particular the plant derived (or vegetable) oils have been shown to be suitable substitutes for hydro-carbon based fuels for use in diesel engines .. The main problems are associated with characteristically low Cetane Numbers and the formation and deposition of residues. However engine tests on both laboratory and commercial type diesel engines show that these oils perform better under normal operating conditions than the Cetane Number would suggest. Furthermore, emulsification with water has been found to reduce emissions of oxides of nitrogen and smoke under certain conditions for both conventional diesel fuel and more particularly for the vegetable oil alternatives and is considered here also as a possible means of reducing residual deposits for the latter. The object of the present work is to study the results of laboratory tests on a single-cylinder diesel engine operating at 750 and 1500 r/min and a four-cylinder diesel engine operating at 2500 and 3500 r/min. Neat diesel and vegetable-oil fuels and their emulsions with 5%, 10% and 15% water, by volume were used in the single-cylinder engine tests at load settings varying from a minimum idling condition to a maximum attainable load condition for each fuel. The single-cylinder engine tests indicated that 10% by volume of water-in-oil in emulsions of both diesel and vegetable oil fuels was the optimum water content. Neat diesel and vegetable-oil fuels and their emulsions with 10% water were thus used in the fourcylinder engine tests. Comparison of the results of the two engines indicates that the trends found in the single-cylinder engine tests also occur in the four-cylinder engine tests. It is shown that both engines perform satisfactorily with vegetable-oil fuel and its emulsion with 10% water, by volume, at a practical running speed despite the low Cetane Number. It is further shown that the Cetane Number. although valid for the conditions of the Cetane test, is not necessarily an appropriate measure of fuel ignitability under different conditions. Ignition-delay values obtained experimentally by analysis of the cylinder-pressure records are compared with calculated values obtained using existing ignition delay correlations. Engine performance parameters and exhaust emissions are not adversely affected when using vegetable-oil fuel or emulsions with 10% water by volume. Indeed the benefits of emulsification on the emissions of smoke and oxides of nitrogen are evident in these tests. This is particularly marked for the vegetable-oil emulsion.

No description available.

The potential health risk of diesel particulate (DP) has stimulated research into its physical and chemical composition. Its interaction with unburnt hydrocarbons (UHC) at exhaust temperatures was studied (i.e. composition and microstructure), at varying engine conditions. A hot whole exhaust filtration system was developed to collect DP on Pallflex TX-40 PTFE coated filters (for minimal artefact formation) down the exhaust of a Ricardo E6/T IDI diesel engine. Electron microscopy (SEM and TEM) and a gravimetric BET method determined particle size, specific surface area (SSA) and pore character. An in vacuo gravimetric thermal degassing (TD) apparatus was constructed to extract adsorbed volatiles (filter extractable sample - FES). The volatile FES was trapped and analysed by gas chromatography and identified as fuel and oil derived UHC's. Ultrasonic and soxhlet extraction techniques were employed for comparison studies. DP are graphitic carbonaceous aggregates of 30-40nm mean particle diameter. Structural analysis indicated that slit-shaped pores (Type II isotherm) were formed between crystallite layers. Highly adsorbed pore-bound FES fractions were identified (fuel i n ultramicropores, 0.355-lnm; fuel/oil in supermicropores, 1-2nm), trapped by overlapping crystallite van der Waal's fields. Engine load influenced micropore adsorption and DP SSA. High loads with high combustion temperatures, efficiently pyrolysed fuel, producing DP with little adsorbed FES and SSA's of 100m² /g. Low loads with lower in-cylinder temperatures, formed less DP and more fuel survived, producing soots of low SSA(<20m² /g). Between aggregated particles, 'ink-bottle' mesopores (2-50nm) were evident (Type IV isotherm) where fuel FES was weakly adsorbed by temperature dependent chemical scavenging as exhaust temperature declined , reducing SSA and increasing particle size. Thermal degassing was more efficient than soxhlet or ultrasonic extraction methods, because the solvent methods failed to penetrate the smallest pores. TD increased soot SSA, greatest for low load samples (by 200m²/g) compared to high load samples (by 50m² /g). TD was highly advantageous for DP extraction and allowed progressive removal of volatiles. A modern DI engine showed structurally similar soots, but the lower DP emissions produced high relative %FES for all engine conditions giving low SSA's. The research findings are related to cylinder and environmental processes for engineers and environmental scientists to improve control strategies.

No description available.

It has been recognised for a number of years that the use of water-in-oil emulsified fuels in diesel engines provides the advantages of improved engine combustion and emissions. At the present time, it is a general practice to burn W/O emulsions on shipboard propulsion diesel engines. To meet the requirements of environmental protection, there exists the possibility of using emulsified fuels on road vehicles in the future. The Department of Marine Technology of The University of Newcastle upon Tyne has been involved in this subject for many years, initially concentrating on the production of emulsions using surfactants, and later using mechanical devices, subsequently concentrating on the engine performance study using W/O emulsions. A multiplicity of experimental data has been obtained from a broad range of diesel engines. In the mean time, there have been many reports in this field from other investigators. It is safe to say that the research on engine performance using emulsified fuels has been comprehensive. This project is a continuation of the application of W/O emulsions in diesel engines. As there is a lack of investigation into W/O emulsion atornisation and combustion, the project alms to a). study the effect of water on fuel atomisation; b). develop the mathematical models for spray atornisation of emulsified fuels; c). investigate the phenomena concerned with the combustion and emissions observed by previous researchers. In the atornisation study of emulsified fuels, it has generally been assumed that the benefits associated with improvements in fuel atomisation are brought about by what is termed the "micro-explosions" effect as observed ill boiler/furnace applications. It has been reported that the positive effect of the micro-explosions in an engine combustion chamber exists only under limited conditions. It is therefore questionable as to whether micro-explosions actually occur in the real engine combustion chamber or not. Even if they do take place it is likely that the explosions are very weak. There is some justification to support the thesis that the perceived benefits of using emulsified fuels may be derived from sources other than micro-explosions. This thesis presents a systematic and detailed investigation on the atornisation of water-in-oil emulsified fuels, which includes the properties of W/O emulsions, atomising fundamentals, test rigs for fuel spray atomisation, mathematical model development and regression of the models, etc. A novel, less expensive and effective method for studying fuel atomisation, is achieved by a high speed camera with a micro lens and an extensive tube, and this has successfully been used in the tests. Test results obtained from the non-combusting bomb indicate that the atornisation of emulsified fuel contributes a major part in the improvements of engine combustion and emissions in the following respects: 1). longer spray penetration; 2). Iarger spray angle; 3). larger fuel specific area/small Sauter mean diameter; 4). more air is available in the spray for combustion. Results are in good agreement with the theoretical study, and explain the mechanisms of the phenomena observed in engine tests by previous researchers. There is also a good consistency between the results and the quantitative descriptions of the models.