Over the past 40 years, several procedures have been proposed for characterizing ideal flotation behavior. These procedures, known as release or tree analysis, generally involve multi-stage flotation in batch, laboratory flotation cells using various combinations of rougher, cleaner, and scavenger configurations. Although some of these procedures have been experimentally compared, there remains considerable controversy as to which approach best approximates the ideal flotation response. In this investigation, modeling and simulation techniques are used in conjunction with experimental studies to compare three procedures commonly used for characterizing flotation behavior. These procedures include timed release analysis, simplified release analysis, and tree analysis. Timed release analysis is shown to produce superior results to simplified release analysis and tree analysis; although simplified release analysis appears to be best suited for locating the "elbow" of the grade-recovery curve. In no case, do any of these techniques approximate a perfect separation. A novel technique, known as reverse release analysis, is described and demonstrated to be superior to the other three procedures. Finally, a theoretical methodology for obtaining the true ideal separation curve is presented. / Master of Science

Field assessments were performed to establish the performance capabilities of a new flotation technology for fine coal upgrading, known as StackCell flotation. Flotation release analysis was performed on all samples to determine the amount of hydrophilic material present in the streams around the flotation cell. Data from this work supported recommendations from the equipment manufacturer that the wash water distribution system should be changed to a drip pan and that the design of the slurry-air distributor from the mixing chamber should be altered. The experimental data showed that as froth depth, rotor speed, and wash water rate changed, the performance of the cell followed expected trends with respect to product quality, but diverged from expected trends with respect to carbon recovery and yield. Other work performed includes the development of a new carbon partitioning test, which uses a blender to provide a high shear environment and uses oil to partition the slurry into a carbon rich oil phase and an ash rich pulp phase. This test is capable of producing results comparable to those of a traditional release analysis. Lastly, a spreadsheet program was developed that can aid users in designing drip pans. This program is capable of producing custom designs or unit cell designs. A study of the effect that plate thickness has on flow rate was performed in order to develop a model for flow through an orifice plate. The results of this work showed that plate thickness has little to no effect on the flow rate. / Master of Science

Diesel engine combustion has been studied during the last decades by researchers in terms of improving the performance of the engine. In order to improve the analysis of the diesel engine combustion, dimensionless parameters were used in this study. It was concluded that the newly introduced dimensionless parameters developed in this study facilitate understanding of diesel engine combustion process. A new method has been proposed to determine the values of the form factor (m) and efficiency factors (a) of the Wiebe equation. This is achieved by developing a modified form of Wiebe equation with only one constant. The modified version of Wiebe equation facilitates the determination of constants accurately, which enhances the accuracy of evaluating the burn fraction. The error induced on the burn fraction f with respect to the values of constants a and m obtained through different methods is discussed and compared. The form factor affects the burn fraction significantly compared to the efficiency factor. A new non-dimensional parameter ‘combustion burn factor (Ci)’ has been identified in the modified Wiebe equation. The burn fraction f was found to be a function of Ci only, thus the benefits of expressing heat release rate with respect to Ci have been presented. The errors associated with the determination of apparent heat release rate (AHRR) and the cumulative heat release (Cum.Hrr) from the measured cylinder pressure data and the assumed specific heat ratio (γ) was determined and compared. The γ affected the calculated AHRR more than the cylinder pressure. Overestimation of γ resulted in an underestimation of the peak value of the AHRR and vice versa, this occurred without any shift in the combustion phasing. A new methodology has been proposed to determine the instantaneous and mean value of γ for a given combustion. A two litre Ford puma Zetec diesel engine, four cylinder and 16 valves was employed to carry out this investigation. This new methodology has been applied to determine γ for a wide range of injection pressure (800 bar to 1200 bar), injection timing (9 deg BTDC to -2 deg BTDC) and engine loads at 2.7 BMEP and 5 BMEP. Standard ultra-low sulphur diesel fuel and two bio-diesels (Rapeseed Methyl Ester and Jatropha Methyl Ester) were studied in this investigation. Ignition delay is one the most important parameter that characterises the combustion and performance of diesel engines. The relation between ignition delay and combustion performance in terms of efficiency and emission was revealed by researchers. Ignition delay period measurements in diesel engine combustion along with the most used correlation for calculating ignition delay are discussed in this work. The effect of constants on accuracy in the correlation were discussed, and induced error on calculated ignition delay periods with respect to constants were calculated and compared. New techniques were proposed to calculate the constant values directly by using the experimental data. It was found that the calculated values for ignition delay using the new techniques matched well with the experimental data. These techniques can improve the accuracy of the ignition delay correlation. Also a new correlation without any constants was introduced in this work. This correlation can be used to predict ignition delay directly by using engine parameters only. The introduced correlation provides better results compared to Arrhenius type correlation presented by Wolfer. This new correlation can be used for feedback control engine combustion process.

Biodiesel is an alternative fuel that can be produced from a variety of lipid feedstocks. It has a number of perceived advantages over conventional petroleum diesel and as a result world production of biodiesel has increased dramatically since the turn of the century. Amongst its reported disadvantages is a widely observed increase in emissions of oxides of nitrogen, or NOx. Several explanations have been proposed for this phenomenon; in reality it is likely to be due to a combination of factors. The interplay of multiple factors affecting NOx emissions means that the increase in NOx when fuelling on biodiesel is not consistent or ubiquitous, but is instead dependent upon operating conditions and the specifics of the fuels being compared. The work documented in this thesis explores the nature and causes of the change in NOx emissions associated with biodiesel. The intention was that, by adjusting operating conditions, and using a wide range of fuels, doped with additives to achieve an even broader range of combustion characteristics, the impact of important variables would be made clearer, making it possible to reduce the problem to its lowest common denominators. In early experiments it was found that NOx emissions from biodiesel tended to be lower than those of petrodiesel under conditions where combustion was relatively highly premixed, but higher under more conventional diesel conditions where diffusion combustion constituted a larger proportion of heat release. The main experimental set revealed a definite increase in NOx emissions when fuelling on biodiesel, for a fixed start of combustion and equivalent degree of premixing. The addition of an oxygenate to petrodiesel elicited comparable NOx emissions to biodiesel, as a function of fuel-bound oxygen content; the data implies that the like-for-like biodiesel NOx increase may be a direct result of fuelbound oxygen. However, the like-for-like biodiesel NOx increase varies dependent upon operating conditions. In part, this may be related to higher apparent heat release rate (AHRR) through the diffusion burn phase when fuelling on biodiesel. This may result from the extended biodiesel injection duration. Across operating conditions, the extent to which smoke emissions when fuelling on petrodiesel exceeded those when fuelling on biodiesel was generally correlated with the magnitude of the biodiesel NOx increase; where the difference in smoke emissions was small, the biodiesel NOx increase was small, and where the difference in smoke emissions was more substantial, so was the difference in NOx emissions. This suggests a possible connection to changes in mixture stoichiometry. When differentiating between fuels, increased cetane number reduces NOx, and increased oxygen content increases NOx. Biodiesel does not necessarily have higher NOx emissions than petrodiesel: the biodiesel NOx increase exists where the difference in cetane number is insuffi cient to counteract the effects of fuel-bound oxygen content.

Uma maneira ecologicamente correta de manejar os recursos energéticos disponíveis e reduzir as emissões de gases de efeito estufa é utilizar biocombustíveis ao invés de combustíveis de origem fóssil em motores de combustão interna. Entretanto, o preço mais alto dos biocombustíveis pode ser um fator limitante para o aumento e viabilização do seu uso. Em relação ao etanol, para se obter misturas com mais de 80% de etanol em água o custo de produção cresce exponencialmente. Assim, se misturas de etanol com alto percentual de água, de menor custo, puderem ser utilizadas em motores de combustão interna com sucesso, esse combustível pode se tornar mais atrativo e mais amplamente utilizado. Este trabalho analisa o desempenho de um motor de ignição por centelha operando com etanol em diferentes percentuais de hidratação, através de simulações computacionais e procedimentos experimentais. Foi utilizado um motor monocilíndrico de 0,668L e naturalmente aspirado, com relação de compressão de 19:1 e injeção direta em pré-câmara, ciclo Diesel, foi modificado para operação em ciclo Otto - injeção de combustível no duto de admissão e relação de compressão de 12:1. Testes em dinamômetro foram conduzidos com o etanol hidratado comercial (95% de etanol e 5% de água) e com misturas de etanol e água com maiores percentuais de hidratação (conteúdo volumétrico de até 60% de etanol e 40% de água). Simulação computacional através de software de volumes finitos unidimensional foi utilizada para realizar a análise da combustão. Foi possível alcançar operação estável com misturas de até 40% de água em etanol e ocorreu aumento de eficiência térmica para misturas de até 30% de água. / An environmentally friendly way to manage the available energetic resources and to reduce greenhouse gas emissions is to use bio instead of fossil fuels in internal combustion engines. However, the sometimes higher prices of biofuels can be a limiting factor for their widespread and viable use. Concerning ethanol and its production costs, to obtain above 80% ethanol-in-water mixtures demands an exponentially increasing energy supply. Hence, if a low-cost high water content ethanol could be successfully burned in internal combustion engines it would be even more attractive and extensively used. This work analyzes the performance of a spark ignition engine running with ethanol with different percentages of hydration through numeric and experimental simulations. To achieve this goal, a 0,668L naturally aspirated single cylinder engine, with compression ratio of 19:1 and pre-chamber direct injection, operating at Diesel cycle was modified to operate in Otto cycle - port fuel injection, with a compression ratio of 12:1. Dynamometer tests were carried out with commercial hydrous ethanol (95% ethanol and 5% water) and water-in-ethanol blends with higher hydration levels (volumetric content up to 60% ethanol and 40% water). Computer simulation through one-dimensional finite volume software was carried out to perform a heat release analysis. It was possible to achieve stable operation with up to 40% water-in-ethanol blends and thermal efficiency increase was achieved for blends with up to 30% of water.

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Uma maneira ecologicamente correta de manejar os recursos energéticos disponíveis e reduzir as emissões de gases de efeito estufa é utilizar biocombustíveis ao invés de combustíveis de origem fóssil em motores de combustão interna. Entretanto, o preço mais alto dos biocombustíveis pode ser um fator limitante para o aumento e viabilização do seu uso. Em relação ao etanol, para se obter misturas com mais de 80% de etanol em água o custo de produção cresce exponencialmente. Assim, se misturas de etanol com alto percentual de água, de menor custo, puderem ser utilizadas em motores de combustão interna com sucesso, esse combustível pode se tornar mais atrativo e mais amplamente utilizado. Este trabalho analisa o desempenho de um motor de ignição por centelha operando com etanol em diferentes percentuais de hidratação, através de simulações computacionais e procedimentos experimentais. Foi utilizado um motor monocilíndrico de 0,668L e naturalmente aspirado, com relação de compressão de 19:1 e injeção direta em pré-câmara, ciclo Diesel, foi modificado para operação em ciclo Otto - injeção de combustível no duto de admissão e relação de compressão de 12:1. Testes em dinamômetro foram conduzidos com o etanol hidratado comercial (95% de etanol e 5% de água) e com misturas de etanol e água com maiores percentuais de hidratação (conteúdo volumétrico de até 60% de etanol e 40% de água). Simulação computacional através de software de volumes finitos unidimensional foi utilizada para realizar a análise da combustão. Foi possível alcançar operação estável com misturas de até 40% de água em etanol e ocorreu aumento de eficiência térmica para misturas de até 30% de água. / An environmentally friendly way to manage the available energetic resources and to reduce greenhouse gas emissions is to use bio instead of fossil fuels in internal combustion engines. However, the sometimes higher prices of biofuels can be a limiting factor for their widespread and viable use. Concerning ethanol and its production costs, to obtain above 80% ethanol-in-water mixtures demands an exponentially increasing energy supply. Hence, if a low-cost high water content ethanol could be successfully burned in internal combustion engines it would be even more attractive and extensively used. This work analyzes the performance of a spark ignition engine running with ethanol with different percentages of hydration through numeric and experimental simulations. To achieve this goal, a 0,668L naturally aspirated single cylinder engine, with compression ratio of 19:1 and pre-chamber direct injection, operating at Diesel cycle was modified to operate in Otto cycle - port fuel injection, with a compression ratio of 12:1. Dynamometer tests were carried out with commercial hydrous ethanol (95% ethanol and 5% water) and water-in-ethanol blends with higher hydration levels (volumetric content up to 60% ethanol and 40% water). Computer simulation through one-dimensional finite volume software was carried out to perform a heat release analysis. It was possible to achieve stable operation with up to 40% water-in-ethanol blends and thermal efficiency increase was achieved for blends with up to 30% of water.

Uma maneira ecologicamente correta de manejar os recursos energéticos disponíveis e reduzir as emissões de gases de efeito estufa é utilizar biocombustíveis ao invés de combustíveis de origem fóssil em motores de combustão interna. Entretanto, o preço mais alto dos biocombustíveis pode ser um fator limitante para o aumento e viabilização do seu uso. Em relação ao etanol, para se obter misturas com mais de 80% de etanol em água o custo de produção cresce exponencialmente. Assim, se misturas de etanol com alto percentual de água, de menor custo, puderem ser utilizadas em motores de combustão interna com sucesso, esse combustível pode se tornar mais atrativo e mais amplamente utilizado. Este trabalho analisa o desempenho de um motor de ignição por centelha operando com etanol em diferentes percentuais de hidratação, através de simulações computacionais e procedimentos experimentais. Foi utilizado um motor monocilíndrico de 0,668L e naturalmente aspirado, com relação de compressão de 19:1 e injeção direta em pré-câmara, ciclo Diesel, foi modificado para operação em ciclo Otto - injeção de combustível no duto de admissão e relação de compressão de 12:1. Testes em dinamômetro foram conduzidos com o etanol hidratado comercial (95% de etanol e 5% de água) e com misturas de etanol e água com maiores percentuais de hidratação (conteúdo volumétrico de até 60% de etanol e 40% de água). Simulação computacional através de software de volumes finitos unidimensional foi utilizada para realizar a análise da combustão. Foi possível alcançar operação estável com misturas de até 40% de água em etanol e ocorreu aumento de eficiência térmica para misturas de até 30% de água. / An environmentally friendly way to manage the available energetic resources and to reduce greenhouse gas emissions is to use bio instead of fossil fuels in internal combustion engines. However, the sometimes higher prices of biofuels can be a limiting factor for their widespread and viable use. Concerning ethanol and its production costs, to obtain above 80% ethanol-in-water mixtures demands an exponentially increasing energy supply. Hence, if a low-cost high water content ethanol could be successfully burned in internal combustion engines it would be even more attractive and extensively used. This work analyzes the performance of a spark ignition engine running with ethanol with different percentages of hydration through numeric and experimental simulations. To achieve this goal, a 0,668L naturally aspirated single cylinder engine, with compression ratio of 19:1 and pre-chamber direct injection, operating at Diesel cycle was modified to operate in Otto cycle - port fuel injection, with a compression ratio of 12:1. Dynamometer tests were carried out with commercial hydrous ethanol (95% ethanol and 5% water) and water-in-ethanol blends with higher hydration levels (volumetric content up to 60% ethanol and 40% water). Computer simulation through one-dimensional finite volume software was carried out to perform a heat release analysis. It was possible to achieve stable operation with up to 40% water-in-ethanol blends and thermal efficiency increase was achieved for blends with up to 30% of water.

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Orientadores : Luiz Fernando Milanez, Jose A. Velasquez / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica / Made available in DSpace on 2018-08-06T09:13:18Z (GMT). No. of bitstreams: 1 Bueno_AndreValente_D.pdf: 1858642 bytes, checksum: 5d8ef42f35d6898a67cb77a3c73c0b7d (MD5) Previous issue date: 2006 / Resumo: As conseqüências da adição de biodiesel ao óleo diesel foram estudadas estabelecendo-se relações de causa e efeito entre o desempenho do motor e os processos de combustão e formação de mistura. Foram incluídos, nesta discussão, aspectos como emissões poluentes, formação de mistura, dinâmica do processo de combustão, eficiência de conversão do combustível,desempenho do motor em carga máxima e consumo específico.Utilizaram-se, sob tal propósito, técnicas tradicionalmente associadas à pesquisa e ao desenvolvimento dos motores de ciclo diesel, tais como a análise de liberação de energia, a análise exergética e ensaios dinamométricos. Devido às pequenas variações observadas nos parâmetros opcionais do motor com a introdução do biodiesel, algumas modificações nos métodos aplicados para a coleta de dados experimentais e nos modelos empregados em seu processamento se mostraram necessárias. Dentre tais ajustes, pode-se destacar a formulação de um novo modelo de análise exergética para os processos ocorrentes no cilindro e a utilização de um arranjo inédito de sistema indicador. Demonstrou-se que a adição de biodiesel em baixas concentrações favorece a conversão da exergia do combustível em trabalho no interior do cilindro, proporcionando uma elevação na eficiência de operação do motor. Para os combustíveis analisados, que compreendem a adição de até 20% de biodiesel em volume, a mistura contendo 10% desta substância ofereceu as melhores características quanto ao desempenho e ao consumo específico / Abstract: The consequences of the biodiesel blends with diesel fuel were analyzed establishing cause and effect relationships between the engine performance and the combustion and mixture preparation processes. In this investigation, aspects like pollutant emissions, mixture preparation,dynamic of the combustion process, fuel conversion efficiency, performance under full load and specific fuel consumption were included.Techniques traditionally associated with diesel engines research and development were utilized for this purpose, including heat release analysis, exergetic analysis and dynamometric bench tests. In order to account for the small effects of the biodiesel introduction on the engine operational parameters, some modifications of the methods and models applied to data acquisition and post-processment were necessary. These modifications include the formulation of a new model for the in cylinder exergetic analysis and a novel arrangement of indicator system. By using the exergetic analysis, it was demonstrated that the blending of biodiesel in low concentrations increases the conversion of fuel exergy into work within the cylinder, causing an elevation on the engine efficiency. For the analyzed fuels, which enclose up to 20% of biodiesel addition in volume, the 10% biodiesel blend has presented the best results of performance and specific fuel consumption / Doutorado / Termica e Fluidos / Doutor em Engenharia Mecânica