The second law analysis is a powerful tool for assessing the performance of engines and has been employed for few decades now. Turbocharged diesel engines have been explored in much detail with the help of second law analyses. There is also a need to examine the turbocharged spark-ignition engines in greater detail using second law analyses as they are gaining popularity in high performance and conventional automobiles as well. A thermodynamic simulation was developed in order to investigate the effects of turbocharging on spark-ignition engines from second law perspective. The exergy values associated with the components of the turbocharger along with the engine components were quantified as a percentage of fuel exergy. The exergy balance values indicated that turbocharger does not add considerably to the overall irreversibilities and combustion irreversibility is still the major source of exergy destruction. A comprehensive parametric investigation was also performed to investigate the effects of compression ratio, intercooler effectiveness, etc. for the turbocharged spark-ignition engine over the entire load and speed range. The simulation studies helped in understanding the behavior of turbocharged sparkignition engine with these parameters. A simulation study was also performed to compare the turbocharged engine with the naturally aspirated spark-ignition engine. This study examined the engines for operating parameters like bmep and bsfc over the entire speed range and revealed that turbocharging offers higher bmep and lower bsfc values for most of the operating range. In an additional study, these engines were analyzed for the brake thermal efficiency values at part load. The results indicated that turbocharging offers marginally higher brake thermal efficiency at part loads.

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A thermodynamic cycle simulation of the four-stroke spark-ignition engine was used to determine the effects of variations in engine design and operating parameters on engine performance and emission characteristics. The overall objective was to use the engine cycle simulation to determine the difference between a propane-fuelled and an iso-octane-fuelled engine for the same operating conditions and engine specifications. A comprehensive parametric investigation was conducted to examine the effects of variations in load, speed, combustion duration, spark timing, equivalence ratio, exhaust gas recycle, and compression ratio for a 3.3 liter, Chrysler Minivan, V 6 engine operating on propane. Parameters were selected for the analysis. Variations in the brake specific fuel consumption, brake specific NOx emissions, and mean exhaust temperature were determined for both the propane-fuelled and the iso-octane-fuelled engines. Brake specific fuel consumption and mean exhaust temperature values for the propane-fuelled engine were consistently lower (3 to 5 %) than the corresponding values for the iso-octane-fuelled engine. Fuel structure did not have a significant effect on brake specific nitric oxide emissions. Predictions made from the simulation were compared with some of the available experimental results. Predicted brake torque and brake power showed acceptable quantitative agreement (less than 10 % variation) in the low engine speed range (1,000 to 3,000 rpm) and similar trends with the available experimental data.

Based on the GT-Power software, an engine cycle simulation for a biodiesel fueled direct injection compression ignition engine was developed and used to study its performance and emission characteristics. The major objectives were to establish the engine model for simulation and then apply the model to study the biodiesel fueled engine and compare it to a petroleum-fueled engine. The engine model was developed corresponding to a 4.5 liter, John Deere 4045 four-cylinder diesel engine. Submodels for flow in intake/exhaust system, fuel injection, fuel vaporization and combustion, cylinder heat transfer, and energy transfer in a turbocharging system were combined with a thermodynamic analysis of the engine to yield instantaneous in-cylinder parameters and overall engine performance and emission characteristics. At selected engine operating conditions, sensitivities of engine performance and emission on engine load/speed, injection timing, injection pressure, EGR level, and compression ratio were investigated. Variations in cylinder pressure, ignition delay, bsfc, and indicated specific nitrogen dioxide were determined for both a biodiesel fueled engine and a conventional diesel fueled engine. Cylinder pressure and indicated specific nitrogen dioxide for a diesel fueled engine were consistently higher than those for a biodiesel fueled engine, while ignition delay and bsfc had opposite trends. In addition, numerical study focusing on NOx emission were also investigated by using 5 different NO kinetics. Differences in NOx prediction between kinetics ranged from 10% to 65%.

In order to understand the atmospheric branch of the earth's hydrologic cycle on the global scale, an atmospheric moisture balance is diagnostically analyzed from the January and July data of the OSU atmospheric general circulation model, which has been integrated for thirty-nine months of simulation with seasonally-varying sea-surface temperature and solar insolation. The model hydrologic processes analyzed for the balance include the surface evaporation, the precipitation by large-scale and cumulus condensation, the vertical transport by large-scale and cumulus mass fluxes, and the horizontal transport of water vapor. The large-scale transports include the contributions from the standing and transient components of motion. Also analyzed are the potential and stream functions of horizontal transport, and the statistics of seasonal and interannual variabilities of the global and hemispheric effects of the hydrologic processes. As a result of these analyses, the hydrologic cycle is constructed and understood for both January and July of the model. Large-scale vertical transport moistens the upper layer; the standing and transient motions contribute mostly in the tropics and higher latitudes, respectively. Large-scale horizontal transport moistens the continental atmosphere except for the relatively small transport from the continents to the oceans by the standing motion in the upper layer; the runoff occurs in the model to balance the marine transport but seasonal trends exist such that snow assumulates during January and melts during July on the global average. Cumulus convection drys not only the lower layer but also the upper layer of the model, and the penetrating cumuli are a major mechanism of maritime precipitation, whereas the large-scale condensation and penetrating cumuli have the dominating effect on the continental precipitation during January and July, respectively. The seasonal precipitation over the Northern Hemisphere continents concurs with strong surface evaporation in summer and also with strong cyclonic activity in winter. Comparison with other models and observational data indicates that the model reproduced some basic features of the atmospheric branch of the hydrologic cycle and its seasonal variation. The intense evaporation (≥ 5 mm day⁻¹) over the Pacific and Atlantic oceans and the rain belts in the tropics are well simulated for both January and July. The poleward transport in the northern middle and high latitudes is in good agreement with observations. The maximum toward-thermal-equator transport in the tropics occurs, however, at the geographic equator for both January and July, indicating that these maxima are about 5 degrees of latitude closer to the seasonal thermal equator than the observed maxima. Nevertheless the global statistics of the model atmosphere are not significantly different from that of the real atmosphere. Among others, we mention the following common features of the January and July moisture balances in the present model. Most precipitation of penetrating convection occurs in regions of strong surface evaporation even though some occurs in the moisture convergence zones where most of heavy mid-level convection is located. In the regions of intense penetrating convection, however, the standing part of surface evaporation is much larger in magnitude than the negative transient part which is essentially due to the positive correlation between the turbulence intensity and surface humidity over wet surfaces. Moreover, the horizontal structure of the standing part conforms to that of the standing vapor pressure difference between the air and the underlying surface. A strategy for further studies is recommended on the basis of our understanding of these features. / Graduation date: 1982

Este trabalho analisa a necessidade da aplicação dos compensadores estáticos de reativos em sistemas elétricos industriais e em sistemas de potência. Vários tipos de compensadores de reativos são apresentados e também é feita uma comparação entre eles. O trabalho está centralizado no estudo dos compensadores estáticos tiristorisados, principalmente o Reator Controlado a Tiristores (RCT) e o Capacitor Chaveado a Tiristores (CCT). São discutidas as influências de alguns parâmetros nas formas de onda do RCT. É feita a dedução das equações das componentes harmônicas de corrente e tensão do RCT. São também analisados os efeitos das harmônicas e os meios de atenuá-las, de modo a mantê-las dentro de níveis razoáveis. Modelos para a simulação de um RCT, para vários tipos de fenômenos em circuitos monofásicos e trifásicos, são apresentados. São Mostrados gráficos e tabelas de algumas simulações utilizando o programa CSMP (Continuous System Modeling Program) e um programa desenvolvido ciclo a ciclo, utilizando o método passo a passo. As simulações permitem avaliar com razoável precisão o comportamento do RCT associado a um capacitor fixo. Sugestões de estudos afins são apresentadas no final do trabalho. / This work analyses the need of using Var systems in industrial and in power electric systems. Various types of VAr systems are presented and also a comparison among them is done. The work is centralized in the study of thyristor static VAr systems. The thyristor controlled reactor (TCR) and the thyristor switched capacitor (TSC) are analysed in more details. Parametric influences in the wave forms of TCR are discussed. TCR voltage and current harmonic equations are deduced. Harmonic effects and also the methods of producing their attenuation are analysed. TCR simulation models for multiple types of phenomena in one phase and three phase circuits are presented. Some graphics and tables using the CSMP (Continuous System Modeling Program), and a cycle by cycle program that uses the step method are showed. The simulations can evaluate with a reasonable precision the behavior of a TCR with a fixed capacitor (FC). Suggestions of other studies are presented at the end of the work.

Este trabalho analisa a necessidade da aplicação dos compensadores estáticos de reativos em sistemas elétricos industriais e em sistemas de potência. Vários tipos de compensadores de reativos são apresentados e também é feita uma comparação entre eles. O trabalho está centralizado no estudo dos compensadores estáticos tiristorisados, principalmente o Reator Controlado a Tiristores (RCT) e o Capacitor Chaveado a Tiristores (CCT). São discutidas as influências de alguns parâmetros nas formas de onda do RCT. É feita a dedução das equações das componentes harmônicas de corrente e tensão do RCT. São também analisados os efeitos das harmônicas e os meios de atenuá-las, de modo a mantê-las dentro de níveis razoáveis. Modelos para a simulação de um RCT, para vários tipos de fenômenos em circuitos monofásicos e trifásicos, são apresentados. São Mostrados gráficos e tabelas de algumas simulações utilizando o programa CSMP (Continuous System Modeling Program) e um programa desenvolvido ciclo a ciclo, utilizando o método passo a passo. As simulações permitem avaliar com razoável precisão o comportamento do RCT associado a um capacitor fixo. Sugestões de estudos afins são apresentadas no final do trabalho. / This work analyses the need of using Var systems in industrial and in power electric systems. Various types of VAr systems are presented and also a comparison among them is done. The work is centralized in the study of thyristor static VAr systems. The thyristor controlled reactor (TCR) and the thyristor switched capacitor (TSC) are analysed in more details. Parametric influences in the wave forms of TCR are discussed. TCR voltage and current harmonic equations are deduced. Harmonic effects and also the methods of producing their attenuation are analysed. TCR simulation models for multiple types of phenomena in one phase and three phase circuits are presented. Some graphics and tables using the CSMP (Continuous System Modeling Program), and a cycle by cycle program that uses the step method are showed. The simulations can evaluate with a reasonable precision the behavior of a TCR with a fixed capacitor (FC). Suggestions of other studies are presented at the end of the work.

This thesis is about the development and performance enhancement of an induction motor electric vehicle drive system. The fundamental operation of the induction motor drive hardware and control software are introduced, and the different modulation techniques tested are described. A software simulation package is developed to assist in the control design and analysis of the drive system. Next, to establish the efficiency gains obtained by using space vector modulation in the improved drive system, an inverter with hysteresis current control is compared to the same inverter with space vector modulation in steady state and on separate driving profiles. A method for determining induction motor harmonic losses is introduced and is based on obtaining the phase current harmonics from sampled induction motor stator phase currents obtained. Using a semi-empirical loss model, the induction motor losses are compared between different pulse width modulation control strategies throughout the torque versus speed operating region. Next, several issues related to the robustness of the control design are addressed. To obtain good performance in the actual vehicle, a new method for driveline resonance compensation is developed and proven to work well through simulation and experiment. Lastly, this thesis discusses the development of a new method to compensate for the gain and phase error obtained in the feedback of the d-axis and q-axis stator flux linkages. Improved accuracy of the measured stator flux linkages will be shown to improve the field oriented controller by obtaining a more accurate measurement of the feedback electromagnetic torque. / Master of Science