O acionamento das máquinas de fluxo, sobretudo as bombas e ventiladores centrífugos, têm no motor elétrico seu principal meio de força motriz. O motor assíncrono, também denominado de motor de indução, é o mais utilizado para esse tipo de acionamento. O presente trabalho mostra as diversas alternativas para avaliar a viabilidade de utilização, em alguns casos, do motor de combustão interna substituindo o motor elétrico para acionamento de algumas máquinas de fluxo. As vantagens na utilização do gás natural como energia final, aliada a evolução tecnológica do motor de combustão interna para uso desse combustível, podem fornecer boas condições na escolha alternativa de acionamento. Certos fatores, tais como razão entre o preço do gás natural e o preço da energia elétrica para cada setor de consumo; o alto investimento para a aquisição do motor de combustão interna a gás natural e o aproveitamento para cogeração, são levados em consideração nas análises do presente trabalho. O aproveitamento do rejeito térmico dos gases de combustão do motor e da água de refrigeração do mesmo contribui favoravelmente para a utilização do motor de combustão interna a gás natural. A análise econômica, que permite a comparação entre os dois sistemas de acionamento de cada caso estudado, é também apoiada com a utilização da termoeconomia. / The driving of flow machines, above all centrifugal pumps and fans, have in electrical motor its main resource of driving power. Asynchrony motor, also called induction motor is the most used for that driving type. The present work shows the several ways for measuring the viability of the replacement of electric motor, in some cases, by the natural gas internal combustion engines driving flow machines. The advantages of employing natural gas, allied to the technological evolution of the internal combustion engine for use of that fuel, can produce good conditions for that drive alternative. Certain factors, such as the ratio between the current price of natural gas and the price of the electric power for each consumption sector; the high investment for the acquisition of natural gas internal combustion engine, as well as the use of this gas for cogeneration are factors to be considered in the analysis performed in this work. The reuse of combustion engines exhaust gas and of cooling system waters may successfully contribute for the choice of natural gas internal combustion engine. Economical analysis, which provides a comparison between the two kinds of driving systems investigate here, can also be supported by employing thermoeconomics tools.

Les émissions polluantes à l’échappement des véhicules automobiles sont l'une des principales sources de pollution de l'air dans le monde d'aujourd'hui. Par conséquent, la législation a évolué afin de limiter ces émissions. L'un des aspects clés pour répondre consiste à bien maîtriser les échanges gazeux au sein du moteur à combustion interne. Cette amélioration est possible par l'optimisation de répartiteurs d'admission d'air. Dans ces répartiteurs d'admission d'air, la maitrise de l’écoulement de type tumble est une piste de progrès. Des volets sont installés à la sortie du répartiteur afin d'améliorer le rapport de tumble et donc le mélange air-carburant (VTS-Variable Tumble System). Une autre caractéristique de l'écoulement à l'intérieur des répartiteurs est l'effet des écoulements pulsés qui engendrent des fluctuations de pression assez importante. Par conséquent, le but de cette étude consiste à simuler le flux d'air pulsé à l'intérieur des répartiteurs d'admission et à identifier l'effet des pulsations de pression sur les composants actifs tels que les volets. Le travail de simulation dans la présente thèse a été effectué à partir du code open source CFD OpenFOAM. Dans un premier temps, l'effet des pulsations de pression est simulé à l'intérieur d'un tube d'acier et une méthodologie de simulation est développée. Les résultats de la simulation sont validés à partir de résultats expérimentaux obtenus sur un dispositif spécifique, le banc dynamique. Ensuite, des simulations ont été effectuées sur le répartiteur d'admission principal avec des volets. Tout d’abord, les simulations sont effectuées en régime permanent avec cinq positions d'ouverture différentes du clapet. Les forces et les moments agissant sur le volet en régime permanent sont obtenus et analysés. Puis, des simulations en régime transitoire avec des effets de pulsation de pression sont effectuées. Les résultats de la simulation instationnaire sont comparés aux résultats expérimentaux en termes de fluctuations de pression relative. Les effets des pulsations de pression sur les forces aérodynamiques et les moments agissant sur les volets sont analysés et commentés. / The exhaust emissions from automobiles are one of the major sources of air pollution in today’s world. Thence,research and development is the key feature of the modern automotive industries to meet strict emission legislation. One of the key aspects to meet these requirements is to improve the gas exchange process within internal combustion engines. It is possible by the design optimization of the air intake manifolds for internal combustion engines. One of such advancement in air intake manifolds is variable tumble systems (VTS). In VTS system, tumble flaps are installed at the exit of the manifold runner in order to improve tumble ratio and hence air-fuel mixing. Another feature of the flow inside the intake manifolds is pressure pulsation effect. Therefore, the aim of the Ph.D. work is to simulate the pulsating air flow inside the air intake manifolds and to identify the effect of the pressure pulsations on the active components like tumble flaps. The simulation work in the present thesis has been carried out on open source CFD code OpenFOAM. In a first step, the effect of pressure pulsations is simulated inside a steel tube and a simulation methodology is developed. The results of the simulation are validated on a specific experimental device, the dynamic flow bench. Then,simulations have been carried out on the main intake manifold with tumble flaps. Firstly, the simulations are performed with five different opening positions of the tumble flap in a steady state configuration. The forces and moments acting on the flap in steady state are obtained and analyzed. Then, unsteady simulations with pressure pulsation effects are performed. The results of obtained from unsteady simulation are compared with the experimental results in terms of relative pressure fluctuations. The effect of the pressure pulsation on the aerodynamic forces and moments acting on the tumble flaps are analyzed and explained.

La compréhension du processus de stabilisation des flammes Diesel constitue un défi majeur en raison de son effet sur les émissions de polluants. En effet, la relation étroite entre la distance de lift-off (distance entre la flamme et l’injecteur) et la production de suie est maintenant bien établie. Cependant, différents mécanismes de stabilisation ont été proposés mais sont toujours sujets à discussion. L'objectif de cette thèse est de fournir une contribution expérimentale et numérique pour identifier les mécanismes de stabilisation majeurs.La combustion d'un spray n-dodécane issu d'un injecteur mono-trou a été étudiée dans une cellule à volume constant en utilisant une combinaison de diagnostics optiques : mesures hautes cadences et simultanées de schlieren, LIF à 355 nm, chimiluminescence haute température ou de chimiluminescence OH *. Des expériences complémentaires sont effectuées au cours desquelles le mélange est allumé entre l’injecteur et le lift-off par plasma induit par laser. L’évolution du lift-off jusqu’à son retour à une position d’équilibre plus en aval est ensuite étudiée pour différentes conditions opératoires. L'analyse de l'évolution du lift-off sans allumage laser révèle deux types principaux de comportement : des sauts brusques en amont et un déplacement plus progressif en aval. Alors que le premier comportement est attribué à des événements d'auto-inflammation, le second est analysé grâce aux résultats obtenus par allumage laser. Il a été constaté que l'emplacement du formaldéhyde avait un impact important sur la vitesse de retour du lift-off.Une simulation numérique directe (DNS en anglais) bidimensionnelle d'une flamme liftée turbulente se développant spatialement dans les mêmes conditions opératoires que les expériences et reproduisant l'évolution temporelle de la distance de lift-off est proposée. Du fait que les expériences montrent que la flamme se stabilise en aval du spray liquide, la DNS ne couvre qu'une région en aval où l’écoulement est réduit à un jet gazeux. La chimie de l’n-dodécane est modélisée à l'aide d'un schéma cinétique (28 espèces transportées) prenant en compte les chemins réactionnels basse et haute température. Comme observé expérimentalement, la stabilisation de la flamme est intermittente : des auto-inflammations se produisent tout d'abord puis se font convecter en aval jusqu'à ce qu'une nouvelle auto-inflammation se produise. Le mécanisme principal de stabilisation est l'auto-inflammation. Toutefois, on observe également à la périphérie du jet diverses topologies de flammes, telles que des flammes triples, qui aident la flamme à se stabiliser en remplissant des réservoirs de gaz brûlés à haute température localisés à la périphérie, ce qui déclenche des auto-inflammations. Toutes ces observations sont résumées dans un modèle conceptuel décrivant la stabilisation de la flamme.Enfin, un modèle prédisant les fluctuations de la distance du lift-off autour de sa valeur moyenne temporelle est proposé. Ce modèle a été développé sur la base d’observations faites dans l’étude expérimentale et numérique : premièrement, le suivi temporel du lift-off a été décomposé en une succession d’auto-inflammations et d’évolutions en aval. Deuxièmement, la période entre deux auto-inflammations et la vitesse d'évolution en aval ont été modélisées à l'aide de corrélations expérimentales disponibles dans la littérature. Troisièmement, le modèle a été adapté afin de prendre en compte l’effet des réservoirs à haute température sur les fluctuations de la flamme. Et enfin, le modèle a été comparé aux données expérimentales, au cours desquelles des variations de la température ambiante, de la concentration en oxygène et de la pression d'injection ont été effectuées. Dès lors que le modèle a montré une bonne correspondance avec les données expérimentales, il peut être utilisé en complément du modèle prédisant la distance du lift-off moyen afin de mieux décrire la stabilisation d’une flamme Diesel. / The understanding of the stabilization process of Diesel spray flames is a key challenge because of its effect on pollutant emissions. In particular, the close relationship between lift-off length and soot production is now well established. However, different stabilization mechanisms have been proposed and are still under debate. The objective of this PhD is to provide an experimental and numerical contribution to the investigation of these governing mechanisms.Combustion of an n-dodecane spray issued from a single-hole nozzle was studied in a constant-volume precombustion vessel using a combination of optical diagnostic techniques. Simultaneous high frame rate schlieren, 355LIF (laser-induced fluorescence) and high-temperature chemiluminescence or OH* chemiluminescence are respectively used to follow the evolution of the gaseous jet envelope, formaldehyde location and lift-off position. Additional experiments are performed where the ignition of the mixture is forced at a location upstream of the natural lift-off position by laser-induced plasma ignition. The analysis of the evolution of the lift off position without laser ignition reveals two main types of behaviors: sudden jumps in the upstream direction and more progressive displacement towards the downstream direction. While the former is attributed to auto-ignition events, the latter is studied through the forced laser ignition results. It is found that the location of formaldehyde greatly impacts the return velocity of the lift-off position.A two-dimensional Direct Numerical Simulation (DNS) of a spatially developing turbulent lifted flame at the same operating conditions than the experiments and reproducing the temporal evolution of the lift-off length is proposed to provide a better understanding of the flame stabilization mechanisms. The DNS only covers a downstream region where the flow can be reduced to a gaseous jet, since experimental observations have shown that the flame stabilized downstream of the liquid spray. N-dodecane chemistry is modeled using a reduced chemical kinetics scheme (28 species transported) accounting for the low- and high temperature reaction pathways. Similar to what has been observed in the experiments, the flame stabilization is intermittent: flame elements first auto-ignite before being convected downstream until another sudden auto-ignition event occurs closer to the fuel injector. The flame topologies, associated to such events, are discussed in detail, using the DNS results, and a conceptual model summarizing the observations made is proposed. Results show that the main flame stabilization mechanism is auto-ignition. However, multiple reaction zone topologies, such as triple flames, are also observed at the jet periphery of the fuel jet helping the flame to stabilize by filling high-temperature burnt gases reservoirs localized at the periphery, which trigger in its turn auto-ignitions.Finally, a model predicting the fluctuations of the lift-off length around its time-averaged value is proposed. This model has been developed based on observations made in the experimental and numerical study: first, the lift-off length time-evolution was decomposed into a succession of auto-ignition events and downstream evolutions. Second, the period between two auto-ignition and the velocity of the downstream evolution was modeled using experimental correlations available in the literature. Third, the model has been adapted to take into account the effect of the high-temperature reservoirs on the flame fluctuations. Last, the model was compared to experimental data, where the ambient temperature, oxygen concentration and injection pressure were varied. Since the model showed good agreement with the experimental data, it can be used in addition to the model predicting the time-averaged lift-off length to better describe the Diesel flame stabilization.

Thesis (Elec.E)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1980. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING. / Includes bibliographical references. / by Wing Hong Lee. / Elec.E

A eletrônica embarcada teve um expressivo ganho de espaço dentro dos veículos ao longo dos últimos anos, mais especialmente no que se refere ao gerenciamento eletrônico do motor á combustão, uma vez que a inteligência empregada nesse sistema vem sofrendo constante evolução, sendo uma das evoluções, a utilização da estratégia FLEX de gerenciamento. O domínio das técnicas de controle de um motor á combustão interna torna-se desafiador em sua própria natureza, haja vista que envolve conceitos heterogêneos e concorrentes entre si em se tratando de aspectos de engenharia. Dessa forma, ainda é restrito o número de profissionais com conhecimento e competência para desenvolver atividades relacionadas ao gerenciamento desse sistema. Esse projeto teve por intuito o emprego de um empenho intelectual realizado em equipe a fim de desenvolver uma unidade de gerenciamento referente ao controle de um motor á combustão interna com estratégia FLEX de gerenciamento, tornando possível a inserção da cultura do estudo de gerenciamento de motores FLEX dentro das universidades, tais como, FATEC-Santo André, Escola Politécnica da USP e principalmente, a FATEC- Sorocaba. Para esse desenvolvimento, uma unidade já existente foi utilizada, sendo a mesma aplicada em seu projeto primitivo no Gol 1.6 com gerenciamento à gasolina e totalmente reprojetada na em seu firmware para o veículo VW Polo 1.6 na atual ocasião. Agora em uma aplicação FLEX, a partir de técnicas de controle, foi possível alcançar resultados similares aos observados na unidade original que equipa o veículo. Embora os resultados obtidos tenham limitações devido às condições de uso do veículo, estrutura da instituição e também do tempo disponível para esse desenvolvimento, foi possível entender e compreender diversos fatores antes maculados pela distância do contato direto com um sistema de gerenciamento real aplicado em um motor à combustão interna. Ademais, dentro das limitações citadas, os resultados obtidos mostraram-se bastante satisfatórios. / The embedded electronics had an expressive gain of space within the vehicles over the last years, more especially regarding the electronic management of the combustion engine since the intelligence employed in this system has been under constant evolution, being one of the evolutions, the use of the FLEX management strategy. The domain of control techniques of an internal combustion engine becomes challenging in its own nature since it involves heterogeneous concepts and competing with each other in the engineering aspects, in this way, the fluency in activities related to the management of this system is very rarefied in the professional and academic environment. The purpose of this project was the use of an intellectual commitment made in a team to develop a management unit for the control of an internal combustion engine with FLEX management strategy, making possible the insertion of the FLEX engine management study culture within the universities, such as, FATEC-Santo André, Polytechnic School of USP and mainly, FATEC-Sorocaba. For this development, an already started unit was used, being applied in its original design in Gol 1.6 with gasoline management and totally redesigned in its firmware for Polo 1.6 in the current occasion, now in a FLEX application, from techniques of control, it was possible to achieve results similar to those observed in the original unit equipping the vehicle. Although the results obtained have limitations due to the conditions of use of the vehicle, structure of the institution and also the time offered for this development, it was possible to understand several factors previously tainted by the distance of direct contact with a real management system applied in a motor to the internal combustion, in addition, within the mentioned limitations, the obtained results were shown quite satisfactory.

<p>The ion current measured from the spark plug in a spark ignited combustion engine is used </p><p>as basis for analysis and control of the combustion variability caused by exhaust gas </p><p>recirculation. Methods for extraction of in-cylinder pressure information from the ion </p><p>current are analyzed in terms of reliability and processing efficiency. A model for the </p><p>recognition of combustion variability using this information is selected and tested on both </p><p>simulated and car data.</p>

The ion current measured from the spark plug in a spark ignited combustion engine is used as basis for analysis and control of the combustion variability caused by exhaust gas recirculation. Methods for extraction of in-cylinder pressure information from the ion current are analyzed in terms of reliability and processing efficiency. A model for the recognition of combustion variability using this information is selected and tested on both simulated and car data.

Environmental pollution is an important problem of our world. Governments are aware of this problem and emission regulations are continuously improved. One of the strictest regulations is about unburned and burned hydrocarbon emissions. In internal combustion engines the origin of the burned and unburned hydrocarbons is fuel and engine oil. As a result of the sanctions and the necessity of improved combustion performance of the engine, manufacturers work on manufacturing technology and engine tribology. With the improvement of these areas oil loss from internal combustion engine is reduced. Engine oil consumption mechanisms are specific research areas in the internal combustion engine development. Oil consumption occurs via to two main routes: &ldquo / Valve train&rdquo / and &ldquo / in cylinder components&rdquo / . In cylinder components have three sub mechanisms: evaporation, ring scraping and blowback. In this thesis, blowback oil loss mechanism is studied. 2D flow model of piston-cylinder mechanism is developed in Fluent. Land pressures and ring end gap flow data are taken from this model. An iterative computer program is developed to calculate backflow oil consumption. In this program, an empirical entrainment correlation compiled from literature is used. The calculated oil consumption values match with the range of the values in the literature.

Oil loss mechanisms in internal combustion engines have been subject to many researches. By the help of technological developments effects of several problems due to oil losses were examined and tried to be reduced. Environmental pollution and performance loss are important issues that oil consumption in internal combustion engines contribute. In this study the effects of individual parameters on the oil accumulation in 2nd land crevice of internal combustion engines, volume between top compression rings, were investigated. The study aimed to investigate the effects of oil film thickness and oil film temperature on the oil accumulation in the 2nd land which contributes to one of the mechanisms of oil consumption in internal combustion engines. Controlled experiments were performed on a modeled piston cylinder assembly. It was seen that oil accumulated in the 2nd land crevice by blow-by gases was affected by the film thickness of lubricating oil and the temperature of the lubricating oil. The amount of oil accumulated increased with increasing oil film thickness. The results also showed that below oil film thickness of 45 &amp / #956 / m / amount of oil accumulated increased with the increase of oil temperature.

No description available.