The effects of swirl and spark location on combustion duration were studied in a constant volume cylindrical chamber of length-to-diameter ratio of 0.5. A chemically balanced methane-air mixture was swirled up to 628 radians per second by tangential injection. The chamber was closed by a valve before ignition by a spark gap of variable location and electrode geometry. The burning duration, indicated by repeated measurements of combustion pressure rise, was found to be a strong function of swirl intensity and spark location. Increased swirl resulted in decreased burning duration; mid-radius ignition location combined with high swirl resulted in the shortest combustion durations. Spark gap was found to have an important effect on the standard deviation of the burning duration, especially with high swirl. Various "flame holders" were installed to achieve shorter burning durations and lower cyclic variation. Results indicated that the best ignition source geometry was an unshielded, low-drag probe. This gave the least burning durations and the least cyclic variation at the higher swirl values. / Applied Science, Faculty of / Mechanical Engineering, Department of / Graduate

Pressure data measurements have been made in a single-cylinder, spark-ignition engine over 100 consecutive cycles. The engine was operated on natural gas at a wide range of engine speed and equivalence ratios. The effects of spark electrode geometry, combustion chamber geometry, spark gap and throttling have also been examined. From these pressure measurements standard deviations in burning times in mass-fraction-burned values were determined. Because of the existing evidence that the origin of cyclic variations is in the early combustion period, the standard deviations of cyclic variation in time required for a small (almost zero) mass-fraction-burned is estimated by extrapolation. These extrapolated values of standard deviation are compared with the implication of a hypothesis that cyclic variations in combustion in spark-ignition engines originate in the small-scale structure of turbulence (after ignition). The nature of turbulence structure during combustion is deduced from existing knowledge of mixture motion within the combustion chamber of the engine. This research determines the turbulent parameters, such as turbulence intensity, turbulent length scales and laminar burning velocity. The standard deviation in burning times in the early stages of combustion is estimated, within experimental uncertainty, by the parameter ⋋/4uℓ where ⋋ is the Taylor microscale and uℓ is the laminar burning velocity of the unburned mixture. This parameter is the consequence of the Tennekes model of small-scale structure of turbulence and Chomiak's explanation of the high flame propagation rate in regions of concentrated vorticity and the assumption that theignition behaves as though it were from a point source. The general conclusion reached is that the standard deviation in the burning time for small mass-fraction-burned is associated with the early stages of burning-predictable from the knowledge of the Taylor microscale and the laminar burning velocity. / Applied Science, Faculty of / Mechanical Engineering, Department of / Graduate

Thesis (Ph. D.)--Missouri University of Science and Technology, 2008. / Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed April 28, 2008) Includes bibliographical references (p. 170-176).

Elimination or reduction of auxiliary oxygen use in Pulse Detonation Engines (PDEs) is necessary if the technology is to compete with existing Ramjet systems. This thesis investigated a Transient Plasma Ignition (TPI) system and found that the technology can at least reduce and may be able to completely remove the auxiliary oxygen requirement of current PDE systems. TPI was tested and compared with a traditional capacitive discharge spark plug system in a dynamic flow, ethylene/air mixture combustor. Ignition delay time, Deflagration-to-Detonation transition (DDT) distance and time, detonation wave speed and fire success rate performance were analyzed for various mass flow rates and stoichiometric ratios. A transient plasma dualelectrode concept was also employed and analyzed. Results show that TPI is more effective and reliable than the spark plug ignition with considerable improvements to DDT performance. The TPI dual-electrode concept was proven to be the most effective configuration with average reductions in DDT distance and time of 17% and 41% respectively when compared to the capacitive discharge spark plug system configuration.

Typescript (photocopy). / Digitized by Kansas Correctional Industries

Internal combustion engine emissions are currently a major source of air pollution. The harmful impact of engine emissions can be reduced when engines are fuelled by alternatives to petrol and diesel such as natural gas. The use of lean burn technology in spark-ignition engines has been dominant; however, the lean burn technique can not economically satisfy the increasingly restricted future emission standards particularly for NOx emissions. In this thesis, the use of the stoichiometric air-fuel mixture with exhaust gas recirculation (EGR) technique in a spark ignition natural gas engine is investigated. The aim of the research is to optimize the key engine operating conditions in order to obtain the lowest NO emissions accompanied with low fuel consumption and high power. This is achieved via both experimental and computer simulation research. / PhD Doctorate

Thesis (M.S.)--University of Nevada, Reno, 2006. / "August, 2006." Includes bibliographical references. Online version available on the World Wide Web.

Thesis (M.S.)--Michigan State University. Dept. of Mechanical Engineering, 2008. / Title from PDF t.p. (viewed on July 27, 2009) Includes bibliographical references (p. 119-122). Also issued in print.

Thesis (Ph. D.)--University of Texas at Austin, 2004. / Supervisor: Ronald Matthews. Vita. Includes bibliographical references. Also available from UMI.

Made available in DSpace on 2015-03-03T11:52:40Z (GMT). No. of bitstreams: 0 Previous issue date: 2014-06-13Bitstream added on 2015-03-03T12:06:10Z : No. of bitstreams: 1 000801083.pdf: 1280442 bytes, checksum: 6dcfc6fb20131fddca0a32bff15754cf (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Nestre trabalho é desenvolvida uma modelagem matemática para os ciclos irreversíveis Otto e Diesel. Os ciclos são analisados entre dois reservatórios com taxa de capacidade térmica infinita, com os processos de troca de calor ocorrendo em trocadores de calor entre o fluido de trabalho e os reservatórios térmicos. As irreversibilidades são decorrentes dos processos de troca de calor ocorrendo em tempo finito, da taxa de perda de calor do reservatório de alta temperatura para o reservatório de baixa temperatura e dos processos de compressão e expansão não-isoentrópicas. São utilizados três critérios de otimização: função ecológica, coeficiente ecológico de desempenho e potência máxima de saída. Estas funções são otimizadas com relação à temperatura de entrada no processo de adição de calor. São analisados as otimizações ecológicas e então comparadas com a potência máxima. Os resultados são apresentados através das curvas de potência e critério ecológico, eficiência térmica ecológico e taxa de geração de entropia e critério ecológico. São analisados os comportamentos de potência líquida, eficiência térmica e taxa de geração de entropia otimizadas ecologicamente através dos quais são avaliadas as influências de alguns parâmetros nos seus comportamentos. Por fim, são analisadas as razões entre a potência otimizada por critérios ecológicos e a potência máxima, eficiência térmica otimizada por critérios ecológicos e a eficiência térmica na condição de potência máxima, a taxa de geração de entropia otimizada por critérios ecológicos e a taxa de geração de entropia na condição de potência máxima. A análise dos resultados comprova que as otimizações ecológicas apresentam o melhor compromisso entre potência líquida e o ambiente. Os resultados poderão ser utilizados como critério relevante no aperfeiçoamento de projetos dos motores de combustão interna / In this work is developed a mathematical model for the irreversible Otto and Diesel cycles. The cycle is analyzed between two reservois with infinite thermal capacitance, where the processes of heat exchange occuring in the heat exchangers between the working fluid and the thermal reservoir at constant temperatures. The irreversibilities follow from the heat exchange processes occurring in finite time, the loss of heat from the hot source to the cold source and the noisentropic compression and expansion processes. Three optimization criteria are used: ecological function, ecological coefficient of performance and maximum power output. These functions are optimized with respect to the inlet temperature of heat addition process. Ecological optimizations are analyzed and compared to maximum power. The results are presented through the power and ecological creteria, thermal efficiency and ecological criteria and entropy generation rate and ecological criteria curves. The results are presented though the power curves and ecological criteria, thermal efficiency and ecological and entropy generation rate and ecological criteria. Analyzes the behavior of power, efficiency and rate of entropy generation ecologically optimized through which they are evaluated the influences of some parameters on their behavior. Finally, we analyze the ratio between ecological criteria for optimum power and maximum power, optimized thermal efficiency by ecological criteria and the maximum power efficiency, the ratio between the entropy generation rate optimized for ecological criteria and entropy generation rate of maximum power. The results show that the ecological optimizations present the best compromisse between power and environment. The results can be used as an important criterion in developing projects of internal combustion engines