Este trabalho buscou estudar os efeitos do nível de Swirl e alteração da massa de combustível injetada nas emissões de poluentes de um motor Diesel. Foram selecionados 15 cabeçotes de uma população de 100 cabeçotes e agrupados pelo nível de Swirl. Como o motor testado utiliza 5 cabeçotes, 15 cabeçotes foram separados e classificados em 3 categorias pelo nível de Swirl. Em seguida, o motor foi montado com as 3 categorias de cabeçotes no dinamômetro com o objetivo de levantar os efeitos nas emissões de gases e parâmetros de desempenho do motor. Foram medidas as emissões de NOx, CO, THC, fuligem, fumaça e consumo de combustível nos 13 pontos do ciclo ESC, complementadas com medições de torque e potência à plena carga. Além disso, nas condições de plena carga foi explorado o efeito da alteração da massa de combustível injetado, pela mudança do ponto final de injeção, nos parâmetros de desempenho e emissões. / This work aimed at the investigation of the effects of the level of Swirl and the amount of fuel mass injected in the emissions of pollutants on a diesel engine. Cylinder heads were selected from a population of 100 cylinder heads and them grouped by Swirl level. As the engine used in the tests have 5 cylinder heads, 15 cylinder heads were separated into 3 categories by the Swirl level. The engine was mounted with the 3 Swirl level cylinder heads categories with the aim to investigate all effects on emissions and performance such as NOx, CO, THC, soot, smoke, fuel consumption, power and torque. The tests were performed following the ESC cycle and exploring the full load curve behavior with changes of the end of injection point, therefore altering the amount of fuel mass injected.

Dans la chaîne de fabrication des produits plats sidérurgiques, les brames sont des produits semi-finis sortant de la coulée continue, se présentant sous la forme de parallélépipèdes d'acier de 150 à 320 mm d'épaisseur qui devront passer dans le laminoir à chaud afin de réduire leur épaisseur à quelques millimètres pour être enfin enroulées en bobines de tôle. Pour permettre les importantes déformations du laminage, les brames doivent entrer dans le laminoir à une température comprise entre 800 et 1200°C; elles sont amenées à cette température en traversant un four de réchauffage où leurs faces supérieure et inférieure sont chauffées par des brûleurs de différents types, parmi lesquels figurent des brûleurs à longueur de flamme réglable, qui doivent permettre une variation, en cours de fonctionnement, de la longueur de la flamme générée par le brûleur afin d'adapter le profil de transfert de chaleur aux caractéristiques géométriques du produit à réchauffer. Ce travail a permis de caractériser le fonctionnement et les performances d'un tel brûleur, en particulier de déterminer la réglabilité effective de la longueur de flamme en fonction des conditions opératoires, ainsi que d'établir l'utilité de la modulation de flamme pour le procédé de chauffage en mesurant les effets de cette variation sur le profil de flux de chaleur transmis à la charge. Les conséquences de ces modifications sur la stabilité de la combustion et sur les quantités de polluants émis, en l'occurrence sur les émissions d'oxydes d'azote (NOx), ont également été examinées. Les performances du brûleur à longueur de flamme variable ont été étudiées par le biais de mesures réalisées sur une unité pilote à échelle réduite, conçue et réalisée au cours de ce travail. La détermination de la longueur de flamme a été réalisée par la mesure de l'émission de chimiluminescence du radical $OH$ tandis que la mesure du profil de flux radiatif incident sur la charge a mis en évidence que les transferts de chaleur au sein du four n'étaient que faiblement modifiés par les variations de longueur de la flamme. Les résultats expérimentaux ont également montré que la forme de la flamme n'influençait pas de manière significative le niveau d'émissions de NOx à la sortie du four. Cette approche a été complétée par une démarche de simulation numérique détaillée de l'équipement à l'aide d'un code commercial de CFD (pour Computational Fluid Dynamics) permettant de résoudre les équations différentielles de l'aéro-thermochimie (écoulement, turbulence, combustion et transfert de chaleur) dans le four. La comparaison des données numériques et expérimentales a permis de valider les résultats de simulation et d'établir leur sensibilité aux hypothèses des modèles utilisés. Elle a montré que la prédiction de la forme de la flamme était principalement conditionnée par les paramètres cinétiques du modèle de combustion plutôt que par le choix des modèles de turbulence et de rayonnement; elle a en outre établi que les niveaux d'émissions d'oxydes d'azote de l'ensemble des flammes modélisées ne pouvaient être calculés correctement par des modèles simples de combustion et de production de NOx. Ce travail s'inscrit dans le contexte de recherches réalisées en collaboration avec l'Agence Internationale de l'Energie, portant sur l'étude des phénomènes liés à la combustion du gaz naturel dans des brûleurs alimentés en air préchauffé; il a bénéficié du soutien financier de la Région Wallonne pour l'acquisition des outils expérimentaux et numériques utilisés au cours de cette étude.

To adhere to the current requirements for NOx and CO emissions in combustion systems, modern land and air based gas turbine engines often operate in the fuel lean regime. While operating near the lean blow out (LBO) limit does reduce some harmful emissions, combustor stability is sacrificed and extinction becomes a major concern. To fully understand the characteristics of lean operation, an experimental study was conducted to map the time averaged flow field in a typical industrial, counter-swirling, liquid fuel combustor. This study examined two steady-state operating conditions, both near the lean extinction limit for this swirl burner. Using an LDV/PDPA system, 2-D mean and fluctuating velocities, as well as Reynolds stresses, were measured throughout the combustor. These measurements were taken for both the non-reacting and reacting flow fields, enabling a direct analysis of the result of heat addition and increased load on a turbulent swirling flow field. To further understand the overall flow field, liquid droplet diameter measurements were taken to determine the fuel spray characteristics as a function of operating pressure and rated spray angle. Chemical composition at the combustor exit was also measured, with an emphasis on the concentrations of both CO and NOx emissions. This large database of aerodynamic and droplet measurements improves understanding of the swirling, reacting flow field and aids in the accurate prediction of lean blow-out events. With this understanding of the lean blow-out limit, increased fuel efficiency and decreased pollutant emissions can be achieved in industrial combustors, especially those used for thrust in the airline industry.

A modified furnace, which burns diesel oil is adopted to study the combustion characteristics and the pollution of the exhausting products under certain designing and operating conditions. The different equivalence ratios and swirl numbers can be obtained by adjusting the flow rate of both axial air and tangential air. The controlling ranges of the various experimental parameters include the equivalence ratios from 0.8 to 1.1, the jet oil pressures from 7 kg/cm² to 9 kg/cm², the open angles of the plate 0¢X and 45¢X, the swirl numbers from 0 to 1.0, the flow rates of the recirculated flue gas from 0% to 12%. The effects of the controlling variables on the combustion characteristics and the formations of pollutants within combustion chamber are studied in this reseach. A photographic technology is used to study the flame structures for helping us to understand the behaviors of the flame under various operating conditions. Under the equivalence ratios from 0.8 to1.1, the concentrations of the average NO and CO decrease, at the lower equivalence ratio. However, the concentrations of the average NO and temperature increases monotonously when jet oil pressure increases. The plate open angle 45¢X is useful for the mixing of both fuel and air, so that the open angle of the plate have important effects on both the temperature of combusion gas and the formation of pollutant NO. When the plate open angle 45¢X and the swirl number is 0.6, the flow rate of NO in the exhaust duct is the lowest. At equivalence ratio 0.8, the average NO concentration in exhaust duct decrease, when the flow rate of the recirculated flue gas increase. Our experiments display that the optimized operating condition is at the plate open angle 45¢X, the swirl number 1.0 and the recirculation rate of the flue gas 12%. NO can be reduced to 32% in this condition, and heat efficiency is reduced only about 3.7%, so we can achieve the request of reducing efficiency to much, the formation of pollutant without influencing the combustion. Under the condition of swirl number 0 and the open angle of the plate at 0¢X and 45¢X the color of the flame in the primary combustion region are white-yellow. In the other hand, at the swirl number 1.0, the color of the flame out of the primary combustion region at the swirl number 1.0 exhibits the red color due to the formation of CO2 and water vapor. The red color region at the swirl number 1.0 is much larger than that at the swirl number 0.

O número de swirl de um cabeçote de motor de combustão interna pode ser medido pelo método de vazão em regime permanente. Nesse método o ar é forçado através do cabeçote para diferentes aberturas de válvula. O sensor comumente utilizado nas plataformas para a medição do swirl é o do tipo ISM (impulse swirl meter) que utiliza um retificador de fluxo como o componente principal para capturar o momento angular de rotação do fluxo de ar. Esse trabalho visa encontrar as dimensões geométricas para o retificador de fluxo utilizado em sensor tipo ISM, de tal forma que esse retificador possibilite a realização das medições com a menor interferência possível no resultado final. Dezesseis retificadores de diferentes dimensões foram construídos a partir do processo conhecido como prototipagem rápida. Vários ensaios foram realizados em uma plataforma que utiliza o método de vazão em regime permanente para a medição de swirl em cabeçotes. Para todos os ensaios foi utilizando um mesmo cabeçote de motor diesel como gerador de swirl. No capítulo conclusões são apresentadas as dimensões geométricas que resultaram em menor interferência no fluxo e uma maior eficiência do sensor, bem como sugestões para trabalhos futuros. / The swirl number of a cylinder head can be measured by a steady state flow method in which air is forced through the cylinder head for different valve openings. The sensors commonly used on the swirl measurement platform are of the ISM type (impulse swirl meter) that use a flow straightener as the main component to capture the rotational angular momentum of the air flow. This study objective is to determine the geometric dimensions for the flow straightener used in the ISM sensor, which still allows the measurement but causes the least interference on the measurement result. Sixteen different flow straighteners were constructed by rapid prototyping process. Several tests were performed on a platform that uses the steady state flow method to measure the swirl number of cylinder heads. For all tests the same cylinder head was used as swirl generator. The conclusion chapter presents the geometric dimensions that caused the least interference in the flow and resulted in a greater sensor efficiency, as well as suggestions for future studies.

No description available.

O presente trabalho tem como escopo validar qualitativa e quantitativamente o ensaio de swirl em cabeçotes de motores Diesel realizado de maneira contínua, comparando-o com o padrão estático amplamente aplicado na indústria no controle de qualidade deste componente. A modificação metodológica do ensaio permite ensaios muito mais velozes do que os atuais, podendo, com todas as verificações necessárias, ser extensível a uma linha de montagem, permitindo controle de qualidade diretamente após o processo de usinagem do fundido ou antes de montar o cabeçote no bloco do motor. O presente trabalho apresenta a metodologia aplicada para o tratamento do problema bem como os resultados obtidos até o momento, indicando também os que ainda serão obtidos. No escopo do projeto, apresenta-se de maneira sucinta todo o procedimento utilizado para as simulações estáticas e transiente dos métodos de medição a partir do método do volume finitos de um código comercial, destacando a metodologia para determinação das malhas, seleção dos modelos e esquemas de discretização utilizados, destacando por fim uma comparação entre diferentes aberturas de válvula do ensaio estático e os primeiros resultados da simulação com abertura de válvula ao longo do tempo de simulação. Do ponto de vista experimental, descreveu-se o equipamento utilizado bem como as adaptações realizadas, principalmente no que tangem a automação do controle de válvula, no escopo do presente projeto, apresentando por fim alguns resultados do ensaio contínuo na bancada em comparação com o estático. Os ensaios e simulações numéricas estática e transientes apresentaram coerência em seus resultados. As simulações, quando comparadas entre si e com os resultados do PIV, mostram que os perfis de escoamento são bastante parecidos em todas as situações, o que permite concluir que existe a possibilidade de se realizar o ensaio de swirl de forma dinâmica para esta configuração específica. / The present work aims to validate qualitatively and quantitatively the swirl test in diesel engine heads performed continuously, comparing it with the static standard widely applied in industry in the quality control of this component. The methodological modification of the test allows for tests much faster than the current ones and can be extensible to an assembly line, allowing quality control directly after the cast machining process or before mounting the engine block. The present work presents the applied methodology for the treatment of the problem as well as the results obtained so far, also indicating the ones that will be obtained. In the scope of the project, the whole procedure used for the static and transient simulations of the measurement methods based on the finite volume method of a commercial code is presented, highlighting the methodology for determining the meshes, selection of models and schemes of discretization. At last, a comparison between different valve openings of the static test and the first results of the simulation with valve opening during the simulation time will be presented. From the experimental point of view, the equipment used was described, as well as the adaptations made, mainly in what concerns the automation of valve control, within the scope of the present project. Some results of the continuous test in the bench are presented and compared with the static ones. The static and dynamic tests and simulations presented good coherence among their results. The simulations, when compared one with each other and to the PIV test results, showed great similarities among the in-cylinder flow velocity profiles, what might lead to the conclusion that it is possible to test cylinder heads dynamically, at least with the presented configuration.

<div>In this experiment, swirl injectors were designed and tested to validate their use in spraying liquid </div><div>lead into a Barton pot combustion chamber to produce lead oxide at a smaller particle size than </div><div>the current stream injection. Testing was done with water and air to determine the best design for </div><div>atomization results, and then the injector was fabricated for liquid lead testing. Thermochemistry </div><div>calculations showed that due to lead oxidation being a surface reaction, the combustion process </div><div>was diffusion controlled. These conditions were used to determine residence time inside a Barton </div><div>pot combustion chamber for predicted droplet sizes. Results of the liquid lead testing showed that </div><div>final lead oxide particle size and residence time was reduced when using a swirl atomizer in place </div><div>of a steady feed stream. Further calculations were done to create a model for a standard combustion </div><div>chamber and injection system for lead oxide production.</div>

Ce travail expérimental s’intéresse à l’écoulement en aval d’un swirler statique court. L’induction d’un mouvement de swirl est une solution connue pour augmenter le gradient pariétal de vitesse. L’augmentation du frottement pariétal présente un intérêt industriel dans les échangeurs de chaleur pour accroître leurs potentiels de transfert de chaleur et diminuer leurs vitesses d’encrassement. Nous proposons d’approfondir la connaissance des écoulements avec swirl décroissant à faibles nombres de Reynolds pour lesquels l’intérêt énergétique est a priori plus important. Dans un premier temps, le champ d’écoulement est caractérisé à l’aide de méthodes optiques, pour identifier le type de tourbillon caractérisant le swirl. Dans un second temps, la méthode électrochimique est utilisée pour mesurer le frottement pariétal instationnaire. Par analogie, ces mesures permettent d’obtenir une première estimation du transfert de chaleur en écoulement anisotherme. / This experimental work is interested in understanding the flow downstream a short static swirler. Inducing a swirl motion is a known solution to increase the wall velocity gradient. The increase in wall shear stress is useful in industrial heat exchangers in order to enhance their heat transfer capabilities and reduce their fouling rates. We try to go deeper into knowledge of decaying swirl flows, for low Reynolds number for which energy interest is greater a priori. First, we study the flow field with optical methods in order to identify type of vortex characteristics of the swirl. Second, electrochemical method is used to measure the unsteady wall shear stress. By analogy, these measurements give a first estimate of the heat transfer for the case of non-isothermal flows.

Ce travail traite de la dynamique des flammes turbulentes prémélangées confinées et swirlées soumises à des perturbations de vitesses acoustiques. L'objectif général est d'acquérir une compréhension des mécanismes régissant la réponse de ces flammes et d'en tirer des méthodes de prévision des instabilités de combustion. Les écoulements swirlés sont d'abord examinés en termes de nombre de swirl et de nouvelles expressions sont données pour cette quantité. On traite notamment des effets de perturbations de vitesse et une expression est proposée qui tient compte des fluctuations de vitesses dans l'écoulement. Le système utilisé pour l'étude expérimentale comprend une cavité amont, un injecteur équipé d'un swirler et un tube à flamme transparent permettant la visualisation directe du mouvement de la flamme. Deux points de fonctionnement sont étudiés correspondant à des vitesses débitantes différentes. La cavité amont et le tube à flamme du brûleur peuvent être facilement changés pour étudier plusieurs configurations différentes. L'acoustique du brûleur est également analysée au moyen d'une approche de cavités couplées pour déterminer les fréquences de résonance du système en configuration non-réactive. Des expériences sont menées pour mesurer les fréquences propres du système et l'estimation du coefficient d'amortissement est réalisée à partir de la réponse du système à une modulation externe. Un critère de découplage des mode acoustiques est proposé. La dynamique de l'écoulement est examinée en termes de conversion de modes au niveau de la vrille (swirler) ou dans une grille d'aubes. Cette partie du travail, effectuée au moyen de simulations numériques montre que lorsqu'une grille ou une vrille sont soumis à une onde acoustique, le swirler donne naissance à une onde azimutale convective en plus de l'onde acoustique axiale transmise. Les deux types de swirlers, axial et radial, donnent lieu à ce mécanisme, un fait confirmé par des expériences. Il est montré que ce processus de conversion de mode a un impact important sur la dynamique de la flamme swirlée. La dynamique de la combustion est ensuite analysée en mesurant la fonction de transfert généralisée ainsi que les distributions de taux de dégagement de chaleur au cours du cycle d'oscillation. La fonction de transfert est utilisée pour déterminer la réponse de la flamme à des perturbations acoustiques se propageant dans l'écoulement en amont de la flamme. Il est aussi montré que le nombre de Strouhal est un groupe sans dimensions qui permet de caractériser la réponse de la flamme. La dynamique est également analysée au moyen d'un ensemble de diagnostics comprenant des sondes de pression, un photomultiplicateur et un vélocimètre laser Doppler. Un modèle pour la fonction de transfert linéaire de la flamme est dérivé théoriquement à partir d'une description de la flamme au moyen de l'équation pour une variable de champ G. Les mécanismes physiques de la réponse de la flamme sont identifiés : enroulement tourbillonnaire et fluctuations du nombre de swirl. L'enroulement tourbillonnaire est associé à l'onde acoustique transmise en aval du swirler et qui pénètre dans la chambre de combustion. Tandis que les fluctuations du nombre de swirl sont directement liées aux mécanismes de conversion de mode au swirler qui induit différentes vitesses pour les perturbations axiales et azimutales. L'enroulement tourbillonnaire enroule l'extrémité de la flamme tandis que les fluctuations du nombre de swirl agissent sur l'angle de la flamme. Ces deux mécanismes en compétition se combinent de manière constructive ou destructive conduisant à des gains faibles ou élevés dans la réponse de la flamme en fonction de la fréquence. Ces mécanismes sont retrouvés par simulation aux grandes échelles (LES). / This work is concerned with the dynamics of premixed confined turbulent swirling flames submitted to acoustic velocity disturbances. The general objective is to gain an understanding of the mechanisms governing the response of these flames and to derive predictive methods for combustion instabilities. Swirling flows are first reviewed in terms of swirl numbers and novel expressions for them are given. Perturbed form of the swirl number are suggested taking into account acoustic disturbances in the flow. The experimental system comprises an upstream manifold, an injector equipped with a swirler and a transparent flame tube allowing direct visualization of the flame motion. Two operating points are investigated corresponding to different bulk velocities. The upstream manifold and the flame tube of the burner can be easily change to test several configurations. The burner acoustic is also analyzed in term of coupled cavities approach to determined the resonant frequencies of the system in non reactive cases. Experiments are carried out to measure the system eigen frequencies and the estimate damping coefficient of the various burners arrangements. A criterion for decoupling acoustic mode is suggested. The flow dynamics is examined in terms of mode conversion occurring at the swirler or downstream an airfoil cascade. This part of the work, carried out with numerical simulations, shows that when submitted to an acoustic wave, a swirler gives rise to an azimuthal convective wave in addition to the transmitted acoustic wave. Both axial and radial swirlers are prone to this mechanism as confirmed by experiments. It is found that this mode conversion process has a strong impact on the flame dynamics in swirling flames combustors. Combustion dynamics is then analyzed by measuring the flame describing function (FDF) of this burner. This FDF is used to determine the response of the flame to acoustic velocity disturbances propagating on the upstream flow. It is shown that the Strouhal number is a suitable dimensionless group to characterize the swirling flame response. The flame dynamics is also analyzed with an ensemble of diagnostics including pressure probes, photomultipliers and laser Doppler velocimeter (LDV). A model for the linear swirling flame transfer function is derived theoretically. The physical mechanisms driving the response of the flame are identified : vortex rollup and swirl number fluctuations. The vortex rollup is associated to the acoustic wave transmitted downstream of the swirler and entering in the combustor while the swirl number fluctuations are directly linked to the mode conversion mechanisms downstream the swirler which induced different axial and azimuthal speeds upstream the flame. The rollup phenomena acts at the extremity of the flame while swirl number fluctuations act on the flame angle. These competiting mechanisms act constructively or destructively leading to low or high gains in the flame response depending on the frequency. These mechanisms are retrieved by large eddy simulations of the flame dynamics. Finally, an instability analysis is carried out by combining the experimental flame describing function (FDF) and an acoustic model of the combustor to determine the frequency and the amplitude of the velocity disturbances at the limit cycle. A good agreement between predictions and experiments is obtained in most cases indicating that the method is suitable subject to further developments.