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

La turbine Pelton est une turbine hydraulique dont le fonctionnement se caractérise par l’interaction d’un jet d’eau avec les augets d’une roue. Cette étude a pour but de comprendre les phénomènes influençant le jet et son interaction avec les augets. Pour cela deux actions différentes ont été menées. Une première a visé à caractériser expérimentalement la fragmentation d’un jet de turbine Pelton. La seconde s’est attachée à développer une méthode numérique pouvant mener`à la simulation précise de jets réels de turbines Pelton. La partie expérimentale a permis de déterminer le mode de fragmentation de ces jets (atomisation turbulente), mais aussi l’influence de la rugosité des parois de l’injecteur sur les performances de la turbine. La participation de ce travail à un projet expérimental a permis de montrer l’influence de l’écoulement en sortie d’injecteur sur la fragmentation du jet. Les phénomènes physiques influençant principalement l’évolution du jet ont ainsi été déterminés. La partie numérique a eu pour but de mettre en place une méthode permettant de simuler l’évolution d’un jet de turbine Pelton (fragmentation) et son interaction avec un auget. Etant donnés les progrès de la méthode SPH-ALE pour la simulation d’impact de jets pour les turbines Pelton, il a été décidé d’adapter cette méthode pour les simulations visées. Ainsi une étude du choix de la vitesse des interfaces de problème de Riemann a permis de réaliser un modèle multiphase stable pour les forts rapports de densité (eau-air). Cette méthode s’est avérée garantir les propriétés de continuité de vitesse normale et de pression à l’interface entre les fluides. L’ajout des phénomènes de tension de surface s’est fait par l’adaptation du modèle CSF (Continuum Surface Force) et le développement d’un second modèle nommé Laplace Law Pressure Correction (LLPC).L’intégration du saut de pression dans le solveur de Riemann a nécessité une étude précise du calcul de la courbure et a permis d’améliorer la simulation de loi de Laplace. La méthode numérique a été ensuite validée sur les cas académiques d’onde gravitaire, de rupture de barrage et d’oscillation de goutte. Les ressources en mémoire et le temps de calcul associé à cette méthode ont nécessité la parallélisation du code de calcul. Le caractère lagrangien de la méthode a très largement influencé la méthode de découpe de domaine pour permettre une bonne répartition de la charge de calcul entre les différents processeurs. En conclusion les phénomènes physiques influençant la fragmentation de jets issus d’injecteurs de turbine Pelton sont désormais mieux connus et ils ont pu être introduits dans la méthode numérique. Les prochains développements porteront sur la simulation de jets dont la condition d’entrée s’attachera à être représentative des caractéristiques d’un écoulement en sortie d’un injecteur de turbine Pelton. / A Pelton turbine is characterized by a water jet which is impacting rotating buckets. The main goal of this study is to understand the phenomena which are impacting the jet and its interaction with the bucket. This study was considering two main works. One is considering experiments which allow determining the jet fragmentation. The second part considers development of a numerical code able to reproduce phenomena linked to Pelton jet fragmentation. The experimental part succeeds to associate Pelton jet behavior with mode of jet fragmentation (turbulent dispersion) and shows the impact of hydraulic roughness on Pelton turbine performances. The access to experimental results from a project involving this PhD work, demonstrates the role of the inlet velocity/turbulence profile on the jet fragmentation. The numerical part used the SPH-ALE (Smoothed Particle Hydrodynamics - Arbitrary Lagrange Euler) method to implement physical models linked with jet fragmentation. This choice was done because of its ability to predict pressure fields resulting of the interaction of a water jet and a rotating bucket. A multiphase model was developed based on a modification of the velocity of the interface of Riemann problem. This model does not diffuse the interface and recovers continuity of normal velocity and pressure at the interface between both fluids. Surface tension effect was implemented through an adaptation of the CSF (Continuum Surface Force) model and through amodel called LLPC for Laplace Law Pressure Correction. A study of the computational methods to determine the interface curvature was performed for the integration of the pressure jump in the Riemann solver. Validation was done on academicals test cases as gravity waves, dam breakor droplet oscillations. The numerical code was parallelized to perform large numerical simulations.To conclude, the numerical code integrates physical phenomena which were shown as important in the experiments. The developments will try to perform jet simulation with inlet condition which will be representative of flow conditions at the outlet of a Pelon turbine injector.

The aim of this diploma thesis was to optimize in detail atomization conditions for antimony hydride in a novel plasma atomizer based on a dielectric barrier discharge (DBD) with atomic absorption spetrometric detection. Argon was found as the best DBD discharge gas employing a flow rate of 50 ml min-1 Ar while the DBD power was optimized at 30 W. Analytical figures of merit including interference study of As, Se and Bi have been subsequently investigated and the results compared to those found in an externally heated quartz tube atomizer (QTA). The limit of detection reached in DBD (0.15 ng ml-1 Sb) is comparable to that observed in QTA (0.14 ng ml-1 Sb). Finally, possibility of stibane preconcentration in a DBD atomizer was studied. Preconcentration efficiency of 102 ± 6 % was found under optimized conditions.

The aim of the thesis is to put a transparent scaled PMMA model of the pressure swirl nozzle into operation, which includes, the selection of working fluids and the preparation of a test set to allow measurements using optical methods (LDA, PDA, PIV, high-speed visualization). The theoretical part describes the basic theory of atomization, optical measurement methods and deals with the problems of optical transition in optically complex systems. It also includes an extensive search for transparent liquids and materials of enlarged models that have been used in experiments, which often aim to match light refractive indices between these materials. In the practical part, attention is paid to the preparation of the test set and tests of chemical effects of several selected liquids on PMMA material are conducted, including a summary of experience with their use, as there was a permanent damage to the material. Several LDA measurements followed, using kerosene, p-cymene, 1-bromonaphthalene and water, evaluated the effect of the refractive index difference on the results. It turned out that no observable influence occurred if the refractive index difference between the nozzle material and the liquid was small. In addition, a visualization of internal flow through a high-speed camera was made. The practical part closes the static pressure measurement in the nozzle chamber, where the pressure ratio was measured on the walls of the chamber as well as on its axis. The measurement confirmed that the pressure on the chamber walls is constant and varies with the distance from the chamber axis.

The dissertation thesis deals with the application of absorption methods for the separation of gaseous pollutants from polluted gaseous mixtures using a pilot plant scrubber. The efficiency of the gaseous pollutant removal was determined based on the hydrodynamic distribution of fluids inside the spray chamber. A TF-28 150 spiral nozzle, which was used to spray the absorption liquid, was experimentally characterized. Specifically, the pressure impact pattern of the liquid produced by the nozzle was investigated using intrusive methods and the effective spray angles, the modes of primary and secondary atomization, the droplet size and liquid velocity distributions were determined using non-intrusive optical methods. Numerical simulations of flow of model gas phase inside the sprinkler head and spraying of the liquid through the spiral nozzle were also carried out. The obtained data can be applied to estimate the interface area and together with the determination of the coefficient of total mass transfer thus define the kinetics of chemisorption for a given absorbent/absorbate combination.

This thesis is concerned with combustion of liquid biofuels, and possibility of using liquid biofuels for lower heat output power units. Overview of basic usable liquid biofuels in Czech Republic is executed in the beginning of the thesis. This part is focused especially on production method and energy effectivity of rape-oil methyl ester (RME) and bioethanol production. Overview of basic atomization method of liquid fuels is executed in next chapters. The focus is stressed on pneumatic atomization, especially effervescent atomization method, which was used in practical experiment. Practical part contains fossil fuel and selected biofuel (RME) combustion test executed on burner testing device. Basic combustion properties was found and test plan was made before executing the test. Various operating conditions are compared in terms of atomization quality, combustion quality and geometrical characteristics of flame. Usability of tested liquid biofuels for lower heat output power units is evaluated in the conclusion.

This master’s thesis deals with measurement of spray characteristics of Effervescent atomizers intended for burning waste and heavy fuels. Atomizers were tested on cold test bench by means of Phase Doppler Anemometry. Spray characteristics were evaluated for many different regimes of pressure, temperature and Gas to liquid ratio. The aim of this measurement is to compare flow regimes and their influence on the quality of spray characteristics. The theoretical part describes basic fundamental principles of liquid atomization, effervescent atomization and principles of laser diagnostic methods. The practical part is engaged with improvements in test bench and setting up and optimization of the laser measuring system. Results contain visualization of spray, velocity profiles and drop size distribution in various operating flow regimes of the jet.

L’objet de cette thèse a été de développer une méthode numérique multi-approche et multiéchelle appliquée à la simulation d’écoulements diphasiques de fluides non miscibles, incompressibles et isothermiques et plus particulièrement à l’atomisation primaire. Cette méthode repose sur une approche couplée entre un maillage local raffiné et un maillage global plus large. Le couplage est explicite avec raffinement en temps, c’est-à-dire que chaque domaine évolue selon son propre pas de temps. Afin de prendre en compte les différentes échelles en temps et en espace dans le processus d’atomisation, cette méthode numérique couple deux méthodes numériques diphasiques différentes : une méthode de capture de l’interface dans le domaine local raffiné près de l’injecteur et une méthode de sous-maille dans le domaine global grossier et la région du spray dispersé. Le code développé et parallélisé dans le logiciel OpenFOAMR s’avère capable de réduire de manière significative le temps de calcul d’une simulation aux grandes échelles de l’atomisation dans un injecteur coaxial, tout en prédisant de manière fiable les données expérimentales. / The purpose of this work has been to develop a multi-approach and multi-scale numerical method applied to the simulation of two-phase flows involving non miscible, incompressible and isothermal fluids, and more specifically primary atomization. This method is based on a coupled approach between a refined local mesh and a coarser global mesh. The coupling is explicit with refinement in time, i.e. each domain evolves following its own time-step. In order to account for the different scales in space and time of the atomization process, this numerical method couples two different two-phase numerical methods: an interface capturing method in the refined local domain near the injector and a sub-grid method in the coarser global domain in the dispersed spray region. The code has been developed and parallelized in the OpenFOAMR software. It is able to reduce significantly the computational cost of a large eddy simulation of a coaxial atomization, while predicting with accuracy the experimental data.

The aim of this thesis was to optimize atomization conditions for selenium hydride in a novel plasma atomizer based on dielectric barrier discharge (DBD) using atomic absorption spectrometry as a detector. Analytical characteristics have been subsequently determined and compared to those reached in a conventional externally heated quartz tube atomizer which was replaced by a sofisticated design of a multiatomizer (MMQTA) in this work. The limit of detection reached in DBD (0,24 ng ml−1 Se) is slightly worse to that observed in MMQTA (0,15 ng ml−1 Se). On the contrary, slightly better resistance towards interferences of Sb, Bi and As was observed in DBD atomizer in comparison with MMQTA. Possibility of selenium preconcentration in a DBD atomizer was studied reaching an overall preconcentration efficiency of 75 ± 5%. The detection limit in a preconcentration mode employing preconcentration period of 300 s has reached 0,012 ng ml−1 Se. Key words: hydride generation atomic absorption spectrometry, dielectric barrier discharge, hydride atomization, hydride trapping, selenium

The aim of this diploma thesis was to optimize in detail atomization conditions for antimony hydride in a novel plasma atomizer based on a dielectric barrier discharge (DBD) with atomic absorption spetrometric detection. Argon was found as the best DBD discharge gas employing a flow rate of 50 ml min-1 Ar while the DBD power was optimized at 30 W. Analytical figures of merit including interference study of As, Se and Bi have been subsequently investigated and the results compared to those found in an externally heated quartz tube atomizer (QTA). The limit of detection reached in DBD (0.15 ng ml-1 Sb) is comparable to that observed in QTA (0.14 ng ml-1 Sb). Finally, possibility of stibane preconcentration in a DBD atomizer was studied. Preconcentration efficiency of 102 ± 6 % was found under optimized conditions.