Orientador: Sergio Santos Mühlen / Dissertação (mestrado profissional) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica / Made available in DSpace on 2018-08-18T19:10:57Z (GMT). No. of bitstreams: 1 Hernandes_MarceloRocha_M.pdf: 3294457 bytes, checksum: d5c6210ad1c775f02c1a394d65ab908c (MD5) Previous issue date: 2011 / Resumo: A questão da partida a frio de motores movidos a Diesel ainda é um problema que não foi apropriadamente resolvido e se torna particularmente crítico em face da tendência de redução de níveis de emissões de poluentes a baixas temperaturas e da taxa de compressão do motor visando redução do consumo de combustível. Embora esteja claro que existem alguns fatores-chave que levam a um apropriado processo de partida a frio, sua relevância e relações não são claramente compreendidas. Assim, os esforços para a otimização do processo de partida a frio são principalmente baseados em procedimentos de tentativa e erro em câmaras climáticas a baixas temperaturas, com sérias limitações em termos de confiabilidade da medição em algumas condições, baixa repetibilidade e altos custos com experimentos. O objetivo deste trabalho é estudar os componentes auxiliares de partida a frio dos motores a Diesel com o intuito de adquirir conhecimento sobre este tema para aplicação em propulsores, de maneira que estes possam ser utilizados em regiões com temperaturas negativas com desempenho confiável. Os componentes estudados serão apresentados, bem como sua aplicação e importância na tarefa de proporcionar as condições adequadas à partida a frio do motor. Além disso, uma visão geral será dada em relação à contribuição que estes componentes trazem na redução de emissões de poluentes e consumo de combustível / Abstract: Cold start in Diesel engines is a problem which has not yet been properly solved and becomes particularly critical with the current trend to reduce the emission levels at low temperatures and engine compression ratio addressed to fuel consumption decrease. Although it is clear that there are some key factors whose control leads to a proper cold start process, their individual relevance and relations are not clearly understood. Thereby, the efforts on optimization of the cold start process are mainly based on a trial-and-error procedure in climatic chambers at low ambient temperature, with serious limitations in terms of measurement reliability, low repeatability and high experiments costs. The objective of this work is to study cold start auxiliary components of Diesel engines in order to acquire knowledge on this topic for application in engines in a way that they can be used in regions with low temperatures with reliable performance. The components studied will be presented, as well as its application and importance of providing appropriate conditions to engine cold start. In addition, an overview will be given on the contribution that these components are going to bring in the reduction of emissions and fuel consumption / Mestrado / Eletrônica / Mestre em Engenharia Automobilistica

A modular thermoacoustic engine (TAE) has been designed and fabricated providing a reliable bench test to study thermoacoustic instabilities. Thermoacoustic engines belong to a class of heat engines that produce acoustic power as a result of a fluid dynamic instability. The engine was built with the capability of being converted from a standing-wave thermoacoustic engine to a traveling-wave thermoacoustic engine with relative ease. Different acoustic mediums in the form of gases comprised of Helium, Argon, or Helium-Argon mixtures were used during experimentation across a range of pressures and temperature gradients. It was found that the thermodynamic properties of the acoustic medium greatly influence the thermoacoustic response of the engine in terms of operational frequency and acoustic power output.

Indiana University-Purdue University Indianapolis (IUPUI) / Natural gas substitution for diesel can result in significant reduction in pollutant emissions. Based on current fuel price projections, operating costs would be lower. With a high ignition temperature and relatively low reactivity, natural gas can enable promising approaches to combustion engine design. In particular, the combination of low reactivity natural gas and high reactivity diesel may allow for optimal operation as a reactivity-controlled compression ignition (RCCI) engine, which has potential for high efficiency and low emissions. In this computational study, a lean mixture of natural gas is ignited by direct injection of diesel fuel in a model of the heavy-duty CAT3401 diesel engine. Dual-fuel combustion of natural gas-diesel (NGD) may provide a wider range of reactivity control than other dual-fuel combustion strategies such as gasoline-diesel dual fuel. Accurate and efficient combustion modeling can aid NGD dual-fuel engine control and optimization. In this study, multi-dimensional simulation was performed using a nite-volume computational code for fuel spray, combustion and emission processes. Adaptive mesh refinement (AMR) and multi-zone reaction modeling enables simulation in a reasonable time. The latter approach avoids expensive kinetic calculations in every computational cell, with considerable speedup. Two approaches to combustion modeling are used within the Reynolds averaged Navier-Stokes (RANS) framework. The first approach uses direct integration of the detailed chemistry and no turbulence-chemistry interaction modeling. The model produces encouraging agreement between the simulation and experimental data. For reasonable accuracy and computation cost, a minimum cell size of 0.2 millimeters is suggested for NGD dual-fuel engine combustion. In addition, the role of different chemical reaction mechanism on the NGD dual-fuel combustion is considered with this model. This work considers fundamental questions regarding combustion in NGD dual-fuel combustion, particularly about how and where fuels react, and the difference between combustion in the dual fuel mode and conventional diesel mode. The results show that in part-load working condition main part of CH4 cannot burn and it has significant effect in high level of HC emission in NGD dual-fuel engine. The CFD results reveal that homogeneous mixture of CH4 and air is too lean, and it cannot ignite in regions that any species from C7H16 chemical mechanism does not exist. It is shown that multi-injection of diesel fuel with an early main injection can reduce HC emission significantly in the NGD dual-fuel engine. In addition, the results reveal that increasing the air fuel ratio by decreasing the air amount could be a promising idea for HC emission reduction in NGD dual-fuel engine, too.

The purpose of this study was to examine the possibility of methane as a replacement to traditional fuels. Methane provides several advantages over fuels such as hydrogen. The LABROC VI was used to examine the performance of a small methane and oxygen rocket engine. A theoretical analysis was performed on the LABROC nozzle to compare the effects of changing the mixture ratio and the chamber pressure. The LABVIEW control program was altered to only take data due to problems with the spark plug. The hardware used within the LABROC and the procedure for operation was examined and possible problems are noted. The existing LABVIEW control program was modified to only record data. Experimental data was taken from firing the LABROC and compared to the theoretical values. To check the viability of a methane motor, a nozzle was designed that produces the approximate thrust of small, commercially available, solid rocket motors.

The goal of this study is to assess the potential of the Stirling engine in alternative energy applications including combined cooling, heating, and power (CCHP) and novel waste heat recovery (WHR) technologies. A first and second law model is developed to quantify Stirling engine performance and realize the crucial parameters in Stirling engine design. In addition, analysis of systems employing the Stirling engine as a prime mover can help justify particular design interests for the engine regarding certain applications. A model of a CCHP system is developed with a Stirling engine prime mover. Sensitivity analysis is performed on the CCHP system to gain a deeper understanding of how each component affects the overall performance of the CCHP system. The main objective of these analyses is to provide information on the feasibility of Stirling CCHP on the basis of primary energy consumption and cost. Finally, the potential of the Stirling engine as a waste heat recovery device is investigated. A thermodynamic model is developed to provide estimates of Stirling engine performance based on an available waste heat stream from any specific heat source, while suggesting practical design constraints on the engine based on bounds from the second law. These results are provided to strengthen the feasibility of the Stirling engine as a bottoming prime mover rather than the central power plant.

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After undergoing a study about current engine modelling and mapping approaches as well as the engine modelling requirements for different applications, a major problem found to be present is the extensive and time consuming mapping procedure that every engine has to go through so that all control parameters can be derived from experimental data. To improve this, a cycle-by-cycle modelling approach has been chosen to mathematically represent reciprocating engines starting by a complete dynamics crankshaft mechanism model which forms the base of the complete engine model. This system is modelled taking into account the possibility of a piston pin offset on the mechanism. The derived Valvetrain model is capable of representing a variable valve lift and phasing Valvetrain which can be used while modelling most modern engines. A butterfly type throttle area model is derived as well as its rate of change which is believed to be a key variable for transient engine control. In addition, an approximation throttle model is formulated aiming at real-time applications. Furthermore, the engine inertia is presented as a mathematical model able to be used for any engine. A spark ignition engine simulation (SIES) framework was developed in MATLAB SIMULINK to form the base of a complete high fidelity cycle-by-cycle simulation model with its major target to provide an environment for virtual engine mapping procedures. Some experimental measurements from an actual engine are still required to parameterise the model, which is the reason an engine mapping (EngMap) framework has been developed in LabVIEW, It is shown that all the moving engine components can be represented by a single cyclic variable which can be used for flow model development.

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