O presente trabalho aborda o gerenciamento eletrônico de motores de combustão interna flex, com foco no desenvolvimento de uma estratégia de controle do avanço de ignição em função da ocorrência de combustão anormal conhecida como detonação, para se maximizar o torque de saída do motor. Primeiramente, é desenvolvido um método para a medição da composição de combustível e correção dos parâmetros de tempo de injeção e avanço de ignição, através de um sensor de composição de combustível. Tais parâmetros são definidos através de mapas que trabalham como um sistema de malha aberta. Em seguida, é desenvolvido um método para a leitura e detecção de detonação, em que são estudadas as particularidades do fenômeno para diferentes composições de combustível e a sua relação com a variação da temperatura do gás de escape e torque de saída do motor. Através do método de detecção e do estudo do fenômeno, é desenvolvido uma estratégia para controle do avanço de ignição em função da ocorrência da detonação. Esta abordagem permite ao sistema aumentar o avanço quando não há ocorrência de detonação, mas este avanço adicional é cancelado quando ocorre detonação. O gerenciamento do motor é realizado através de uma ECU de desenvolvimento modelo Flex-ECU, as estratégias de gerenciamento são desenvolvidos através da plataforma ASCET e a aquisição de dados e calibração de parâmetros são executados em uma ferramenta de medição e calibração. Os benefícios que o controle do avanço de ignição traz ao torque do motor são analisados e discutidos em função da rotação e da composição de combustível utilizado. / The present investigation explores the electronic management of internal combustion engines flex fuel, in which the focus is the development of a strategy for the spark advance angle as function of the abnormal combustion occurrence known ad Knock, in order to maximize the output torque. First, a method is developed for measuring the fuel composition and correction of the injection time and spark advance angle parameters through a fuel composition sensor. This parameter is defined through maps that work as an open loop system. Then, a method for detection of knock is developed, the peculiarities of the phenomenon are studied for different fuel compositions and the relationship of the phenomenon with the variation of the exhaust gas temperature and the engine output torque. Through the method of detection and the study of the phenomenon, an algorithm is developed to control the spark advance angle due to the knock occurrence, in which the approach allows the system to increase the angle when there is no occurrence of knock, but this additional angle is reduced when knock is detected. Engine management is performed through a development ECU model Flex-ECU, management algorithms are developed through the ASCET platform and data acquisition and calibration of and parameters is performed through a measurement and calibration platform. The result that the spark advance angle control brings to the engine torque output is analyzed and discussed depending on the rotation and the fuel composition used.

University of Macau / Faculty of Science and Technology / Department of Computer and Information Science

Not available / text

D. Tech. Mechanical Engineering. / Discusses how to reduce the negative impacts of petroleum oil based fuels in reciprocating engines on the environment through the use of oxygenated (alcohol) blends, while not deteriorating engine performance. The specific objectives are as follows: To evaluate the performance characteristics of n-butanol-diesel blends: B5, B10 and B20, in a direct-injection turbo-charged diesel engine and to compare findings with a study that was carried out by others (Sayin, 2010). To compare the performance, combustion and emission characteristics of dual alcohol-gasoline with single alcohol-gasoline blends fired in a naturally-aspirated (NA) spark ignition (SI) engine. To compare the combustion and emission characteristics of dual alcohol (methanol-n-butanol-gasoline) blends with single alcohol (methanol-gasoline) blends in a single-cylinder SI engine. To evaluate the combustion and regulated emission characteristics of DF and n-butanol/diesel blends (B5, B10, and B20 where B5 represents 5 % shared volume of n-butanol to 95 % diesel fuel) fired in a high load turbo-charged diesel engine and to compare the findings with a study that was conducted by Raslavicius & Bazaras, (2010).

Dans un contexte de diminution des émissions polluantes émises par les moteurs à combustion interne, le secteur des transports assiste à une amélioration des motorisations mais également à une diversification des carburants pour l’automobile. L’utilisation de ces différents carburants entraîne souvent un impact sur les performances de la combustion. Dans le cas du moteur à allumage commandé, la performance dépend du dégagement d’énergie, image de la vitesse de la combustion, soit du front de flamme consommant le mélange air-carburant. Or toute flamme en expansion est théoriquement soumise à des effets de courbure et de cisaillement, toutes deux contributions de l’étirement. La réponse à l’étirement étant propre à chaque type de mélange air-carburant (lié au carburant proprement dit, à la richesse du mélange, à la dilution …), ce travail de thèse est centré sur la compréhension de l’impact de l’étirement sur les performances des carburants dans les moteurs à allumage commandé. Pour cela, différents mélanges air-carburant similaires du point de vue des propriétés thermodynamiques et des vitesses fondamentales de combustion laminaire mais avec des sensibilités à l’étirement différentes ont été sélectionnés. Ces mélanges ont ensuite été étudiés dans différentes configurations expérimentales et à l’aide de différentes techniques de mesure: moteur monocylindre opaque et à accès optiques, chambre sphérique de combustion turbulente. Les résultats montrent que les propriétés de sensibilités à l’étirement déterminées en régime laminaire comme la longueur de Markstein et le nombre de Lewis sont indicatrices du comportement des mélanges en combustion turbulente, comme dans la chambre de combustion caractéristique des moteurs à allumage commandé, et sont des paramètres à prendre en considération afin de prédire les performances plus globales de ces carburants que ce soit expérimentalement qu’en simulation. / In a context of decreasing pollutant emissions, the transport sector is facing an improvement of engine concept as well as a fuel diversification. The use of these different fuels often involves an impact on the combustion performance itself. In the case of Spark ignition engine, the efficiency is a function of the released heat, image of the combustion speed, i.e. the flame front speed consuming the air-fuel mixture. It is well known that every expanding flame is submitted to flame curvature and strain rate which are both contributors to flame stretch. As the answer of each air-fuel mixture (i.e. the fuel itself, the equivalence ratio, the dilution …) is different to flame stretch, the objective of this work is to understand flame stretch impact on fuel performance in Spark-Ignition engines. To achieve this goal, different fuel-air mixtures with similar unstretched laminar burning speed and thermodynamic properties but different responses to stretch were selected. Those mixtures were then studied with different experimental devices with different measurement techniques: single-cylinder metallic and optical engines, turbulent combustion spherical vessel. Results show that flame stretch sensitivity properties such as Markstein length and Lewis number, determined in laminar combustion regime, are relevant parameters to describe the flame propagation in turbulent combustion as in the combustion chamber of the Spark-Ignition engine and need to be taken into consideration to evaluate global performance of these fuels, experimentally and also in modeling simulation.

De nos jours, la conception de moteurs à combustion interne à allumage commandé exige une consommation de carburant réduite et des émissions polluantes faibles, tout en conservant une performance adéquate. Le coût élevé des essais expérimentaux vient en faveur de l'utilisation de la simulation numérique pour l'évaluation de nouvelles définitions techniques. La modélisation phénoménologique zéro-dimensionnelle de combustion permet d'évaluer les différentes définitions techniques en tenant compte de différents aspects de de la combustion à allumage commandé comme la géométrie, la flamme laminaire et l'impact de la turbulence. Ces modèles calculent également la concentration des espèces de gaz d'échappement. Afin de créer un modèle de combustion, qui pourra décrire la physique de la combustion, les aspects principaux de la combustion pré-mélangée laminaire et turbulent sont identifiés. Trois versions de modèles de combustion typiques sont comparées en termes de description physique du processus de combustion. Le résultat de cette comparaison a indiqué le modèle le plus pertinent (le modèle de densité de surface de flamme). Ce modèle est retenu et il est complété avec la modélisation physique des plusieurs phénomènes qui affectent le taux de dégagement de chaleur. Ces phénomènes sont l’interaction flamme-paroi, les réactions post flamme et l’étirement de flamme. Enfin, le modèle proposé est validé pour plusieurs configurations techniques. Chaque configuration a un impact sur un paramètre spécifique de moteur. Cette analyse montre quels sont les intervalles de confiance et les limitations du modèle proposé. / Nowadays, the design of Spark Ignition internal combustion engines is focused on the reduction of fuel consumption and low pollutant emissions, while conserving an adequate output power. The high cost of experimental testing comes in favor of the use of numerical simulations for the assessment of engine technologies. Phenomenological Zero-Dimensional combustion models allow evaluating various technical concepts since they take into account various aspects of spark ignition combustion such as chamber geometry, laminar flame characteristics (thickness and speed) and the impact of turbulence. Such models also calculate species concentration of the exhaust gases. In order to create a zero-dimensional combustion model, which can be able to describe correctly the physics of combustion, the key aspects of laminar and turbulent premixed combustion are identified. Three versions of typical combustion models are compared in terms of physical description of the combustion process. The result of this comparison indicated the most physically pertinent mod-el (the Flame Surface Density model). This model is retained and is enhanced with physical modeling of the several phenomena, which affect the heat release rate. Those phenomena are the wall-flame interaction, post-flame reactions and flame stretch. Finally, the proposed model is validated for several engine configurations. Each configuration has an impact on a specific engine parameter. This analysis shows which are the confidence intervals and the limitations of the proposed model.

Le moteur à allumage commandé fortement downsizé est une des solutions les plus prometteuses utilisée par les constructeurs automobiles pour augmenter le rendement et réduire les émissions de CO2. Cependant, les conditions thermodynamiques plus sévères rencontrées dans ces moteurs favorisent l’apparition de combustions anormales (cliquetis et rumble) qui sont difficiles à analyser expérimentalement vu les risques encourus par le moteur. La méthode Reynolds Averaged Navier-Stokes (RANS) s’est imposée depuis plusieurs années pour l’étude des moteurs à piston dans l’industrie, mais elle n’est pas la plus appropriée pour étudier des phénomènes locaux et sporadiques comme les combustions anormales qui n’affectent pas le cycle moyen simulé en RANS. Grâce à l’utilisation d’un code compressible LES et au développement d’une version améliorée des modèles ECFM-LES (Extended Coherent Flame Model) et TKI (Tabulated Kinetics of Ignition) qui permet un découplage total entre les taux de réaction liés à la propagation de la flamme et à l’auto-inflammation, ces travaux mettent en évidence pour la première fois la capacité de la LES à décrire le phénomène de cliquetis dans une configuration réaliste d’un moteur à allumage commandé. Contrairement aux études précédentes [S. Fontanesi and S. Paltrinieri and A. D’Adamo and G. Cantore and C. Rutland, SAE Int. J. Fuels Lubr., 2013-01-1082, pp. 98-118][G. Lecocq, S. Richard, J.-B. Michel, L. Vervisch, Proc. Combust. Inst. 33 (2011) 3105-3114], une étude quantitative du cliquetis est réalisée grâce à des post-traitements spécifiques et similaires pour les résultats expérimentaux et numériques. La LES est capable de prédire la variabilité de la pression cylindre, la fréquence mais également l’angle moyen d’apparition de l’auto-inflammation sur un balayage d’avance à l’allumage. Une analyse 3D démontre également que le cliquetis se déclenche à différents endroits, mais principalement dans la moitié de la chambre sous les soupapes d’échappement. De plus, l’intensité du cliquetis est proportionnelle à la masse de gaz frais brûlée en auto-inflammation pour les faibles intensités, alors qu’une croissance beaucoup plus forte est observée pour les intensités les plus élevées. Ceci suggère que des facteurs supplémentaires interviennent comme la localisation du cliquetis ou les interactions entre l’acoustique interne et l’auto-inflammation. L’utilisation d’un code LES compressible permet une visualisation directe de ces interactions mettant en évidence que les faibles intensités sont liées à des auto-inflammations locales sans couplage alors qu’une transition de la déflagration vers la détonation est possible en moteur automobile et correspond aux intensités les plus fortes. / Highly boosted spark ignition engines are more and more attractive for car manufacturers in terms of efficiency and CO2 emissions reduction. However, thermodynamic conditions encountered in these engines promote the occurrence of abnormal combustions like knock or super-knock, which are experimentally difficult to analyze due to the risks of engine damages. The Reynolds Averaged Navier-Stokes (RANS) method mainly used in industry for piston engines is not the most appropriate as knock does not always affect the mean cycle captured by RANS. Using an accurate LES compressible code and improved versions of ECFM-LES (Extended Coherent Flame Model) and TKI (Tabulated Kinetics of Ignition) models allowing a full uncoupling of flame propagation and auto-ignition reaction rates, this work demonstrates for the first time that LES is able to describe quantitatively knocking combustion in a realistic downsized SI engine configuration. Contrary to previous studies [S. Fontanesi and S. Paltrinieri and A. D’Adamo and G. Cantore and C. Rutland, SAE Int. J. Fuels Lubr., 2013-01-1082, pp. 98-118][G. Lecocq, S. Richard, J.-B. Michel, L. Vervisch, Proc. Combust. Inst. 33 (2011) 3105-3114], a quantified knock analysis is conducted based on a specific post-processing of both numerical and experimental data. LES is able to predict the in-cylinder pressure variability, the knock occurrence frequency and the mean knock onset crank angle for several spark timings. A 3D analysis also demonstrates that knock occurs at random locations, mainly at the exhaust valves side. Knock intensity is found proportional to the fresh gases mass burned by auto-ignition at low knock intensities, while an exponential increase at the highest intensities suggests the influence of additional factors like the knock location in the cylinder or complex behavior of knocking combustion. A direct LES study of acoustic and autoignition interactions is then achieved. The LES visualizations allows showing that low knock intensities are only linked to local autoignition, but a deflagration to detonation transition occurs in such engine operating conditions and is responsible for the highest knock intensities.

O etanol (álcool etílico) tem sido cada vez mais estudado e testado como combustível alternativo para substituição do uso de alguns derivados de petróleo em motores de combustão interna. O presente trabalho procura abordar o emprego do etanol na forma vaporizada em motores do ciclo Otto, objetivando a obtenção de melhores níveis de rendimento térmico total. Deste modo, um motor para teste de octanagem (motor CFR) foi equipado com um vaporizador de álcool instalado no coletor de escapamento, e após uma série de ensaios, várias análises puderam ser feitas. Essas considerações procuraram se ater a aspectos como rendimento térmico, relação ar/combustível, ângulo de avanço da centelha, temperatura de escape, assim como potência e eficiência volumétrica, levando em conta, sempre, a sua influência no funcionamento geral do motor. Ficou constatado que o motor movido a etanol vaporizado apresenta rendimento consideravelmente maior, menor consumo de combustível e funcionamento mais suave que aqueles verificados quando o mesmo motor e alimentado com álcool líquido. / The ethanol (ethyl alcohol) has been studied more and more as alternative fuel to replace some petroleum derivatives for internal combustion engines. The attached study examines the application of vaporized ethanol for Otto cycle engines, searching for better levels of total thermal efficiency. Therefore, an engine for test of octane number (CFR motor) was equipped with an alcohol vaporizer installed inside the escape pipe, and after many experiences, several analysis were made. The various analysis included aspects as thermal efficiency, air/fuel ratio, advance ignition, escape temperature, power and volumetric efficiency, always considering their influence on the operation of the engine. It was confirmed that the engine moved by vaporized ethanol presents higher thermal efficiency, smaller fuel consumption and smoother working than in case of alimentation by liquid alcohol.

O álcool etílico ou etanol vem se tornando, neste novo século, uma importante referência para estudos e aplicações que procuram um combustível alternativo ao uso de derivados de petróleo em motores de combustão interna. Neste trabalho, o uso do etanol vaporizado pelos gases de escape em motores do ciclo Otto busca a obtenção de melhores níveis de rendimento térmico e emissões de poluentes. Assim sendo, um motor de 1.0 litro foi montado em laboratório com um trocador de calor instalado ao lado do coletor de escapamento, e uma série de testes foram feitos, possibilitando uma cuidadosa análise quanto a rendimento térmico, relação ar/álcool, ângulo de avanço da centelha, temperatura de escape e gases de emissão, entre outros aspectos. Conclui-se que o motor a álcool vaporizado, em certos regimes de funcionamento, apresenta rendimento maior e emissões menores que aqueles verificados no motor a álcool líquido. / The ethyl alcohol or ethanol is becoming, in this new century, an important reference for studies and applications that search for an alternative fuel to be used in internal combustion engines, replacing oil derivatives. In this study, an Otto cycle engine is fueled with ethanol vaporized by the exhaust gases, aiming for better levels of thermal efficiency and exhaust emissions. Therefore, a 1.0 liter engine with a heat exchanger connected to the exhaust manifold was prepared in a test bench, and several tests were made, which allowed a criterious analysis about air/alcohol ratio, spark ignition time, exhaust temperature and exhaust emissions, and others. It was concluded that the engine fueled with vaporized alcohol presents, in some operation points, higher thermal efficiency and less emissions compared to the case of engine fueled with liquid alcohol.

Orientador: Rogério Gonçalves dos Santos / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica / Made available in DSpace on 2018-08-23T13:19:35Z (GMT). No. of bitstreams: 1 Fajgenbaum_Renata_M.pdf: 5459929 bytes, checksum: 05a7fae663d15ca13af6858bbe983761 (MD5) Previous issue date: 2013 / Resumo: A motivação em se estudar os fenômenos que acontecem em cada subsistema de um motor de combustão interna ciclo Otto reside na possibilidade de se prever e otimizar seu funcionamento, em especial com os diferentes combustíveis de nova geração que estão sendo inseridos no mercado. O processo de atomização que ocorre nos bicos injetores de combustível, dispositivos integrantes do sistema de injeção eletrônica do motor, apresenta forte relação com a posterior reação de combustão e, por conseguinte, com a eficiência térmica do motor. No presente trabalho, experimentos foram conduzidos para investigar o efeito da temperatura do líquido em parâmetros de atomização de um atomizador do tipo mecânico-centrífugo utilizado em bicos injetores de combustível automotivos. O aparato experimental consistiu de uma bancada de injeção de combustível conectada a um sistema de controle de calor, este com objetivo de variar a temperatura do combustível. Os parâmetros de atomização foram avaliados por meio da técnica de Shadowgraphy, a fim de se medir diâmetro de gotas, distribuição de partículas e campo de velocidades. Gasolina e etanol em diferentes temperaturas foram usados para fornecer variação nas propriedades do líquido, ambos com a mesma pressão de injeção. Os resultados de tamanho de gota foram dados, principalmente, em termos de Sauter Mean Diameter (SMD) e outros diâmetros representativos que se mostraram pertinentes. Todas as medições foram realizadas em duas diferentes distâncias axiais do orifício de descarga. Para as duas distâncias escolhidas, 25 mm e 100 mm, o SMD e a velocidade se mostraram insensíveis à faixa de temperatura testada, devido à baixa variação das propriedades dos combustíveis. Por outro lado, a distribuição das partículas permitiu visualizar o efeito da temperatura nos diâmetros das gotas, mostrando que o aumento da temperatura proporciona diminuição no tamanho das gotas, e o comparativo entre os parâmetros nas duas distâncias axiais permitiu visualizar o efeito da primeira e segunda atomização sobre o spray / Abstract: The motivation in studying the phenomena that happen in each internal combustion engine subsystem lies in the possibility to predict and optimize its operation. The atomization process that occurs in fuel injectors, devices that belong to engine injection system, has a strong relation with the subsequent combustion reaction and thus with the engine thermal efficiency. Experiments were performed to investigate the liquid temperature effect on atomization parameters in an internal combustion engine pressure-swirl atomizer. The experimental apparatus consisted of a flow control rig connected with a heat control system. The flow rig, which is an injection system, was built specifically for that purpose and the heat system goal was to vary the liquid temperature. The atomization parameters were evaluated by means of Shadowgraphy technique in order to measure drop mean diameter, particle size distribution and drop velocity field. Gasoline and ethanol in different temperatures were used to provide variation in liquid properties and the same injection pressure was used for both fuels. The results for drop sizing were expressed in terms of Sauter Mean Diameter (SMD) and the velocity field as well as the particle size distribution measurements were taken in two different axial distances from the nozzle exit. At both distances, 25 mm and 100 mm, SMD and velocity seemed to be insensitive to the range of temperature used because it provided low variation in fuel properties. On the other hand, particle size distribution allowed the visualization of temperature effect on drop diameters, showing that increasing temperatures decrease droplet sizes, and the comparison between two axial distances allowed seeing the effects of first and second atomization on the spray / Mestrado / Termica e Fluidos / Mestra em Engenharia Mecânica