Dissertations / Theses on the topic 'Combustion LIBS'

This thesis contains the results of optical flame emission measurements of the Vulcain 2.1engine and the plasma emission spectroscopy of the Lumen Project engine. The plume spectroscopyis analyzed, ordered and studied in detail to offer the best possible molecular composition.The main focus relied on the hydroxide radical, blue radiation and other moleculesanalysis of the intensities encountered during the tests. The plasma emission spectroscopy isfocused on the determination of the plasma temperature value in LIBS measurements. Thehydrogen plasma temperature determination of the local thermodynamic equilibrium, followedby the carbon and sequentially oxygen plasma is obtained. The quality of the LTE isto be determined to judge the truthworthness of the determined temperatures. Both the testsare analyzed thanks to the use of spectrographs, cameras and dedicated software for opticalapplications. The results related to the Vulcain 2.1 LOX/LH2 engine showed the evolutionof the plume in different ROF or pressure variations. Furthermore, the results of the LumenProject LOX/methane engine led to the determination of the plasma temperatures and a firstestimation of the LTE quality.
Die vorliegende Arbeit präsentiert die Ergebnisse der Abgasstrahlspektroskopie des H2/LOXVulcain 2.1 Triebwerks und der Zündplasma Spektroskopie des CH4/LOX Triebwerks desLUMEN Projektes. Die Abgasstrahlspektroskopie wurde analysiert und im Detail untersuchtum die am besten passende molekulare Zusammensetzung herauszuarbeiten. DasHauptaugenmerk liegt dabei auf dem Hydroxyl- Radikal, der Blauen Strahlung und molekularerIntensitätsanalyse. Bei der Zündplasmaanalyse liegt der Fokus auf der Bestimmungdes LTE Zustands (Lokales thermodynamisches Gleichgewicht) in LIBS. Die Temperaturdes Wasserstoff-, Kohlenstoff und Sauerstoffplasmas wird herangezogen, um die Qualitätdes LTE Zustands zu beurteilen. Für die Testdurchführung wurden Spektrographen, Kamerasund bestimmte Auswertungstools für optische Anwendungen benutzt. Das Verhaltendes Vulcain 2.1 Abgasstrahls abhängig von verschiedenen ROF und Druckstufen ist in denErgebnissen beschrieben. Für das LUMEN Triebwerk konnten erste Zündplasmatemperaturenbestimmt werden und geben einen Rückschluss auf die Qualität des LTE.

Analyse et simulation numérique d'écoulements supersoniques réactifs. Étude de la stabilisation d'une flamme par effet Mach au sein d'un écoulement air-hydrogène prémélangé bidimensionnel. Analyse phénoménologique des conditions d'allumage et de stabilisation d'une flamme à l'aval d'un système stationnaire d'ondes de choc ; cette analyse montre qu'il faut tenir compte de la réaction chimique dans la structure considérée. Exploration de méthodes de résolution des équations de la cinétique chimique complexe explosive air-hydrogène ; analyse de la stabilité de ces méthodes.

L’objet de ce travail concerne l'analyse et la simulation numérique d'écoulements supersonique réactifs. Dans une première partie, on étudie la stabilisation d'une flamme par effet de mach au sein d'un écoulement air-hydrogène prémélange bidimensionnel. On présente d'abord une analyse phénoménologique des conditions d'allumage et de stabilisation d'une flamme à l'aval d'un système stationnaire d'ondes de chocs. Cette étude montre qu'il est nécessaire de tenir compte de la réaction chimique dans la structure considérée. On explore ensuite la stabilité de quelques méthodes implicites et linéairement implicites pour la résolution des équations de la cinétique chimique complexe explosive air-hydrogène, et on effectue également l'analyse de stabilité de tels schémas dans des cas simplifiés, montrant en particulier leur inadéquation pour des cinétiques rapides et trop fortement exothermiques. Pour des simulations stationnaires ou instationnaires, on adopte une méthode à pas fractionnaires fondée d'une part sur un solveur de Riemann multi-espèces explicite du deuxième ordre, en volumes finis non structurés, et d'autre part sur un solveur spécialisé pour la chimie, tel que Limex ou lsode. On termine cette partie par quelques résultats de simulations bidimensionnelles, pour une combustion air-hydrogène avec cinétique complexe et loi d'état réaliste. Le deuxième volet aborde l'étude des phénomènes de transports diffusif et turbulent. La méthode de résolution des équations de Navier-Stokes laminaires est fondée sur une formulation volumes finis structurés. Le deuxième ordre est atteint par le schéma T. V. D. De Harten, qui se rapporte identiquement au flux de Roe au premier ordre. Pour accélérer la convergence vers un état stationnaire, on utilise un schéma implicite linéarisé. L’inversion du système linéaire résultant s'effectue grâce à une méthode de Gauss-Seidel par lignes. Le terme source chimique fait l'objet d'un traitement particulier, visant à conserver des propriétés de positivité des valeurs propres des matrices jacobiennes intervenant dans l'implication. Les effets de la turbulence sont pris en compte par un modèle k-epsilon, et l'interaction cinétique chimique-turbulence par une approche en densité de probabilité présumée en température. Des essais numériques sont alors effectués d'abord dans quelques situations académiques, en particulier pour une couche de mélange compressible à masse volumique fortement variable. On termine par des comparaisons avec des résultats de la littérature de couche de mélange réactive air-hydrogène, ainsi qu'une expérience de combustion supersonique.

Ce travail porte sur certains problèmes de combustion lies à l'allumage dans les moteurs fusée cryotechniques. Dans les conditions nominales de fonctionnement de ces moteurs, la combustion peut être de type prémélangée (les réactifs se mélangent avant de réagir) ou non-prémélangée. L'allumage se produit par la rencontre entre des gaz chauds et un prémélange partiel, sous la forme d'éléments de flamme. Après la propagation de la flamme vers les injecteurs, les flammes de prémélange disparaissent et des flammes non prémélangées s'établissent dans la cavité. Les chapitres II et III ont été consacrés a l'étude théorique et expérimentale de flammes laminaires prémélangées. Les résultats des calculs concernent des flammes de prémélange et de diffusion et permettent de cerner les domaines de richesse, pression et taux d'étirement ou l'allumage est envisageable. Des mesures spectroscopiques permettent de déterminer le comportement de flammes de méthane et d'hydrogène soumises à différentes conditions. Les trois derniers chapitres de cette thèse sont consacrés à la combustion turbulente, et plus particulièrement à la propagation de la flamme turbulente après l'allumage. On trouve au chapitre IV des rappels concernant plusieurs modélisations de la combustion turbulente dans les cas prémélangé et non-prémélangé. Le chapitre V donne les bases théoriques d'un nouveau modèle mixte destine à la description de la transition entre les deux types de combustion, et le chapitre VI donne une première validation de ce modèle en comparant des résultats expérimentaux avec ceux issus des calculs.

L'hydrodynamique du procédé de combustion de charbon dans un lit fluidisé circulant est étudiée. Cette étude vise, en particulier, l'effet de l'injection d'air secondaire sur le comportement de la suspension. Nous avons utilisé une installation pilote en similitude avec la centrale thermique de Carling (Lorraine, France). L'étude a mis en évidence l'existence de deux régimes hydrodynamiques séparés par une concentration critique de solide. La comparaison des diagrammes de régime, avec et sans air secondaire, a montré que cette concentration est unique dans les deux cas. La structure de l'écoulement diphasique a été étudiée au moyen d'une sonde de prélèvement non-isocinétique et d'une sonde à fibres optiques placées à trois niveaux de la colonne. La combinaison des techniques de prélèvement de solide et de mesure des vitesses de particules a permis de développer une méthode pour estimer la concentration locale de solide. L'étude des profils de flux massiques de solide a montré que la distribution des iso-flux dépend sensiblement de la vitesse superficielle du gaz. De plus, nous avons constaté que ces iso-flux sont indépendants de l'injection d'air secondaire. Par ailleurs, nous avons constaté que la configuration d'arrivée d'air secondaire dans la colonne, est très importante. Pour réduire l'influence de cette injection sur la structure de l'écoulement, il faut éviter la formation de jets au niveau de l'injection d'air secondaire. L'ensemble des informations obtenues dans cette étude, nous a permis de proposer des modèles de profils de flux massique et de concentration de solide sous forme de corrélations adaptées à une extrapolation industrielle.

The development of Laser-Induced Thermal Grating Spectroscopy (LITGS) for diagnostics of combusting and non-combusting flows is described. The first use of LITGS to provide in situ calibration of 2-Dimensional temperature distributions generated using Two-Colour Planar Laser-Induced Fluorescence (TC-PLIF) is reported. Time-resolved measurements of temperature distributions in a firing GDI optical engine obtained by TC-PLIF were made during the compression stroke and calibrated to the absolute temperature scale by simultaneous LITGS measurements. The accuracy and precision of the temperatures derived from LITGS data are evaluated using alternative methods of data analysis - Fast Fourier Transform and Fitting to theoretical models of the experimental data. The relative merits of the two methods are examined for analysis of weak LITGS signals obtained under engine conditions of low pressure and high temperature. The combined TC-PLIF and LITGS system was demonstrated by performing repeated single-shot measurements for 1 in every 10 four-stroke cycles showing excellent correlation of the temperatures derived from both techniques. Direct measurement of the effect of 'charge cooling', of order 5 K, for operation with direct injection is reported. Inhomogeneous temperature distributions were observed during the compression stroke for fired operation with Port Fuel Injection (PFI) and also with Gasoline Direct Injection (GDI). The effects of varying the relative concentrations of toluene and iso-octane in the two-component fuel were investigated. Extension of the LITGS technique to multi-point measurements along a 1-D line is described. By recording signals from 4 points on separate detectors using a fibre-coupled photodiode array the limitations of Streak Cameras used previously for 1-D LITGS measurements were overcome. Demonstration of principle experiments are reported in which simultaneous 4-point measurements were made with 1 mm spatial resolution and a precision of 0.7 % in temperature gradients in gas flows and in boundary layers at surfaces.

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
The intensive search for the reliability of results increases the role of reference materials, mainly in analytical chemistry, because they provide metrological references to ensure traceability of measurements and are still central to the validation of analytical methods. The increasing demand for new reference materials is gradual in all areas of knowledge, but the agricultural and food sectors are among the neediest. In Brazil, this requirement is met only by the import of the material at high costs, being frequently the lack of adequate material to the needs of the country. In this context, this work aimed at the production of reference material for inorganic nutrients and contaminants present in a phosphate rock, the raw material used to manufacture fertilizers. The material was produced by following the next steps, internationally established by ISO GUIDES 30 to 35: preparation and ackaging material, assessment of uniformity, stability test in short and long periods and in prior characterization that was the assembly of the collaborative trial, with the distribution of the prepared material to laboratories that were willing to collaborate with the project.Sample preparation studies also have been conducted, aimed at speed and reduced use of reagents. The evaluation of the estimated minimum mass, homogeneity, and stability of the material was performed using inductively coupled plasma optical emission spectrometry (ICP OES) as determination technique. Phosphorus determination was evaluated by laser-induced breakdown spectroscopy (LIBS).Analysis of single-factor variance (ANOVA) was applied to results and the homogeneity and stability of the material presented averages within the 95% confidence interval. The obtained resultsalong the prepare and with collaborative trialallowed the chemical characterization and the determinationof the uncertainties related to each stage of the preparation of the material, and final preparation of the chart control with results of the reference materialwith the expanded uncertainty for each of the analytes under study.Part of the work was developed by the National Research Council Canada (NRCC) in Ottawa in Canada.The applicability of the microwave-induced combustion for sample preparation of previously prepared national reference materials, bovine liver (RM-Agro E3001a) and forage (RM E1001a-Agro) was evaluated for the determination of As, Cd, Cu, and Pb by inductively coupled plasma mass spectrometry (ICP-MS), and the recults coulb be applied in other organic and inorganic materials.
A intensa busca por confiabilidade de resultados torna cada vez mais importante o papel dos materiais de referência, principalmente em química analítica, pois fornecem referências metrológicas visando assegurar a rastreabilidade de medições e ainda são fundamentais para a validação de métodos analíticos. O aumento da demanda por novos materiais de referência é gradativo em todas as áreas do conhecimento, porém os setores agropecuários e de alimentos estão entre os mais carentes. No Brasil, essa demanda é atendida somente pela importação do material a custos elevados, sendo freqüente a inexistência de materiais adequados às necessidades do país. Nesse contexto, o presente trabalho visou à produção de material de referência para nutrientes e contaminantes inorgânicos em fosfato de rocha, matéria-prima utilizada para a fabricação de fertilizantes. O material foi produzido seguindo as seguintes etapas, estabelecidas internacionalmente pelas ISO GUIAS 30 a 35: preparo e envase do material, avaliação da homogeneidade, teste de estabilidade a curto e a longos períodos e na caracterização prévia, que consistiu na montagem do ensaio colaborativo, com a distribuição do material preparado a laboratórios que se dispuseram a colaborar com o projeto. Ainda foram realizados estudos voltados ao preparo da amostra visando a rapidez e redução de uso de reagentes. A avaliação da estimativa da massa mínima, da homogeneidade e da estabilidade do material foi realizada utilizando-se como técnica de determinação a espectrometria de emissão óptica com plasma indutivamente acoplado (ICP OES). Para a determinação de fósforo foi avaliado o emprego de espectrometria de emissão com plasma induzida por laser (LIBS). Os resultadosforam submetidos à análise de variância e fator único (ANOVA) e a homogeneidade e a estabilidade do material apresentaram médias dentro do intervalo de confiança de 95%. Os resultados obtidos durante o preparo e através do ensaio colaborativo possibilitaram a caracterização química e o calculo das incertezas relativas a cada etapa do preparo do material, sendo elaborada a carta controle com os resultados do material de referência e as incertezas expandidas para cada um dos analitos em estudo. Parte do trabalho foi desenvolvido junto ao National Research Council Canada (NRCC) em Ottawa no Canadá, onde foi avaliada a aplicabilidade do sistema de combustão iniciada por radiação microondas no preparo de amostras de materiais de referência nacionais anteriormente preparados, fígado bovino (RM-Agro E3001a) e forrageira (RM-Agro E1001a), para a determinação de As, Cd, Cu e Pb por espectrometria de massas com plasma indutivamente acoplado (ICP-MS), sendo obtidos resultados que poderão ser aplicados em outros materiais orgânicos e inorgânicos.

This diploma work aims to evaluate the functional connection of the cogeneration unit with an internal combustion engine and an absorption heat pump to increase the heating effect of the cogeneration. The aim of this work is to design a functional system and evaluate it from the technical - economic terms. In the introduction of the theoretical work the applied cogeneration technologies used in combined heat and power production are presented. Then there is described the principle of heat pumps, their basic components and theoretical comparison of compression and absorption heat pumps. In the practical part of this work is for a specific application in the area Technická 2 proposed merger of the cogeneration unit with an internal combustion engine and an absorption heat pump, while detailed design parameters used in absorption heat circulation are set. At the end of this paper there are designed various heat exchangers of applied absorption heat pump. The final part of the work is devoted to technical - economic assessment of applied design. In this assestment three different types of heat pumps are compared: Absorption heat pump with working solution H2O-LiBR, absorption heat pump with working fluids NH3-H2O and compressor heat pump.

This work deals with the development, validation and application of a model of Chemical Looping Combustion (CLC) in a circulating fluidized bed system. Chapter 1 is an introduction on Chemical Looping Combustion. It rst presents the most important utilizations of coal in the energy industry. Then, it shows that because of the CO2 capture policy, new technologies have been developed in the frame of post-combustion, pre-combustion and oxy-combustion. Then, the Chemical Looping Combustion technology is presented. It introduces multiple challenges: the choice of the Metal Oxide or the denition of the operating point for the fuel reactor. Finally, it shows that there are two specicities for CFD modeling: the influence of the collisions between particles of different species and the local production of gas in the reactor due to the gasication of coal particles. Chapter 2 outlines the CFD modeling approach: the Eulerian-Eulerian approach extended to flows involving different types of particles and coupled with the chemical reactions. Chapter 3 consists in the validation of the CFD model on mono-solid (monodisperse and poly-disperse) and poly-solid flows with the experimental results coming from an ALSTOM pilot plant based at the Universite Tchnologique de Compiegne (France). The relevance of modeling the polydispersity of a solid phase is shown and the influence of small particles in a CFB of large particles is characterized. This chapter shows that the pilot plant hydrodynamics can be predicted by an Eulerian-Eulerian approach. Chapter 4 consists in the validation of the CFD model on an extreme bi-solid CFB of particles of same density but whith a large particle diameter ratio. Moreover, the terminal settling velocity of the largest particles are twice bigger than the fluidization velocity: the hydrodynamics of the large particles are given by the hydrodynamics of the smallest. An experiment performed by Fabre (1995) showed that large particles can circulate through the bed in those operating conditions. Our simulations predicted a circulation of large particles, but underestimated it. It is shown that it can be due to mesh size eect. Finally, a simulation in a periodic box of this case was dened and allowed us to show the major influence of collisions between species. Chapter 5 presents the simulation of a hot reactive CLC pilot plant under construction in Darmstadt (Germany). The simulations account for the chemical reactions and describe its eect on the hydrodynamics. Different geometries and operating conditions are tested.

Développement d'une méthode de mesure, basée sur l'émission-absorption du rayonnement thermique dans le proche infrarouge entre 1 et 5 microns, permettant de déterminer des valeurs ponctuelles sur toute l'épaisseur visée pour pouvoir établir les champs radiaux aussi bien qu'axiaux des températures et tester les modèles à deux dimensions

In this work, reactive unsteady three-dimensional numerical simulations of a Chemical Looping Combustion (CLC) plant are performed. The plant is a 120 kWth pilot working with Ca-Mn-based material as selected oxygen carrier. Numerical simulations are performed by NEPTUNE_CFD code using an Euler-Euler approach which computes both the gas and the solid phases in an Eulerian fashion accounting for specific closures in order to model interphase mass, momentum and energy transfers. Reduction and oxidation heterogeneous (i.e. gas-solid) reactions are modeled by means of a grain model (shrinking core model in the grain) accounting for both the competing mechanisms of chemical reaction at the particle internal surface and gaseous diffusion through the product layer. Results from numerical simulations are validated against experimental measurements and analyzed in order to gain insight in the local behaviour of the reactive gas-particle flow in the CLC system. The theoretical/numerical tool developed in this work will be used for design upgrade recommendation in the stage of scaling-up from pilot to industrial facilities.

The origin of this PhD thesis lies in the study of Ebullated Bed Reactors (EBRs). These chemical reactors are very active research topics in chemical processes, notably thanks to their usage in heavy oil processing. Many complex phenomena take place within EBRs, and make their design and optimization difficult. In fluid mechanics, a lot of physical mechanisms present in EBRs are active fields of study (three-phase flow, fluid-body interaction...). Hence, in the present work, a study of the mechanisms participating in the hydrodynamics of an EBR with cylindrical catalysts is performed. In a first part, the impact of the catalyst anisotropy on its fall is investigated. In order to gain insight on the effect of the body anisotropy on its fall dynamics, we investigate experimentally the free fall of a solid cylinder in a fluid at rest. The sensitivity to two dimensionless parameters, the Archimedes number (Ar) and the aspect ratio of the cylinder (L/d) is examined. Experiments are conducted with two orthogonal cameras, and advanced image processing techniques are developed in order to measure the position and orientation of the cylinder in 3D. Within the range of parameters studied (200 < Ar < 1100, 2 < L/d < 20), the cylinders adopt different types of falling motion. Two main types of paths are observed, the first one is a rectilinear fall of the cylinder that keeps its axis horizontal, and the second one is a fluttering oscillatory motion. Other more complex types of motion are observed and discussed. The fluttering motion of the cylinder is analyzed in details. On top of the study of the body motion, the cylinder wake is also visualized and characterized. A large number of particles are present at the same time inside an EBRs (about 40% of the mass). Interactions between multiple objects have a strong impact on the motion of each individual particle, but are very complex. In a first approximation, we take into account the presence of numerous particles by introducing a confined medium. We study experimentally the fall of a single cylinder in a confined vertical thin-gap cell, where the cylinders are free to move in only two directions. The cylinder elongation ratio (3