Experimental measurements of the lift-off velocity and lift-off height, and numerical simulations were conducted on the liftoff and stabilization phenomena of laminar jet diffusion flames of inert-diluted C3H8 and CH4 fuels. Both non-reacting and reacting jets were investigated, including effects of multi-component diffusivities and heat release (buoyancy and gas expansion). The role of Schmidt number for non-reacting jets was investigated, with no conclusive Schmidt number criterion for liftoff previously known in similarity solutions. The cold-flow simulation for He-diluted CH4 fuel does not predict flame liftoff; however, adding heat release reaction leads to the prediction of liftoff, which is consistent with experimental observations. Including reaction was also found to improve liftoff height prediction for C3H8 flames, with the flame base location differing from that in the similarity solution - the intersection of the stoichiometric and iso-velocity contours is not necessary for flame stabilization (and thus lift-off). Possible mechanisms other than that proposed for similarity solution may better help to explain the stabilization and liftoff phenomena. The stretch rate at a wide range of isotherms near the base of the lifted tribrachial flame were also quantitatively plotted and analyzed.

The rapid development of micro/nanofabrication techniques have enabled engineering of material interfacial properties. Micro/nanostructures with unique electrical, mechanical, thermal, magnetic, optical, and biological properties, have found applications in a wide range of fields such as electronics, photonics, biological/chemical sensing, tissue engineering, and diagnostics, etc. As such, numerous strategies have been developed for structuring materials into micro/nano- scale. However, the challenge still lies in the high cost, low throughput, complexity in fabrication, and difficulty in scaling up. This thesis aims to explore fabrication strategies for micro/nanostructured surfaces that are versatile, simple, and inexpensive. The thin film stencil lift-off technique with both Parylene and self-adhesive vinyl has been explored for this purpose. Further applications of the resulted micro/nanostructured surfaces are also presented in this thesis. Through improved Parylene stencil fabrication process, both spontaneously phase-segregated and arbitrary binary supported lipid bilayer patterns have been achieved. Also, the microstructured Parylene surfaces have been ddemonstrated for patterning stacked SLBs that are either homogeneous or phase-segregated. Without any lithography technique involved, vinyl stencil lift-off offers as a facile and inexpensive benchtop method for patterning thin films such as metal and glassy films. Combining the thermal shrinking of shape memory polymer, the patterned feature sizes are further decreased by 60% in both x and y dimensions, pushing the patterning resolution to down to sub-100 μm range. In addition, the shrinking process induces micro/nanostructures onto the deposited thin film, and the structure sizes are easily tunable with film thickness deposited. Further applications of such patterned micro/nanostructured surfaces has also been explored. The structured gold films have served as high-surface-area electrodes for electrochemical sensing. By introducing photoresist as a sacrificial layer, the structured gold thin films can be lifted off and transferred onto elastomeric substrate, and serve stretchable and flexible sensors. Such sensing devices exhibit great stability and reproducibility even when working under external strain. Finally, the micro/nanostructured glassy surfaces have been employed as substrate for cell growth to study topographical effect on cell morphology. It has been concluded that rougher surfaces lead to cell elongation, and finer structures promote filopodia generation. These results underscore the strength and suitability of thin film stencil lift-off as a powerful technique for creating micro- and nanostructured surfaces. These structured surfaces could find applications in many other areas, due to their great properties such as tunable structure size, high surface area, flexibility, and long-term stability. / Thesis / Doctor of Philosophy (PhD)

La préoccupation de plus en plus importante ces dernières décennies, liée à l’épuisement des ressources pétrolières et au réchauffement climatique par les gaz à effet de serre a accentué l’intérêt du butanol comme carburant alternatif dans le secteur des transports grâce à ses propriétés adaptées pour le moteur à allumage par compression. Cependant, le faible rendement des procédés de production et de séparation empêche encore sa commercialisation en tant que carburant. C’est pourquoi le mélange de fermentation intermédiaire de la production de butanol, Acétone-Butanol-Ethanol(ABE), est de plus en plus considéré comme un carburant alternatif potentiel en raison de ses propriétés similaires au butanol et de ses avantages quant à son cout énergétique pour sa fabrication.Dans ce cadre, ce travail a pour objectif d’étudier l’impact des propriétés de différents mélanges d’ABE et n-dodécane en comparaison avec des mélanges d’alcools (éthanol et butanol) sur le processus de pulvérisation et de combustion et ce,pour différentes proportions en volume allant de 20% à 50%. Pour cela, une nouvelle chambre de combustion appelée"New One Shot Engine ", a été réalisée et utilisée car les conditions haute pression et haute température de "Spray-A" (60bars, 800-900 K et 22,8 kg/m³) définies par le réseau Engine Combustion network (ECN) peuvent être atteintes. Autant les phases liquides et vapeur que de combustion ont été caractérisées grâce à l’utilisation des plusieurs techniques optiques (extinction, Schlieren, chimiluminescence d’OH*) dans des conditions non réactives (Azote pur) et réactives (avec15% d'oxygène). Ces résultats expérimentaux ont non seulement permis d’étudier l’impact en oxygène moléculaire et de fournir une nouvelle base de données fiables, mais aussi d’affirmer la possibilité d’utiliser jusque 20% d’ABE en volume dans des moteurs à allumage par compression, grâce à ses caractéristiques de pulvérisation et de combustion similaires au carburant Diesel conventionnel. / The growing concern in recent decades, linked to the depletion of oil resources and global warming by greenhouse gases has increased the interest of butanol as an alternative fuel in the transport sector. However, the low yield of production and separation processes still prevents its commercialization as a fuel. Therefore, the intermediate fermentation mixture of butanol production, Acetone-Butanol-Ethanol (ABE), is increasingly considered as a potential alternative fuel because of its similar properties to butanol and its advantages in terms of the energy and cost in the separation process.The context of this work aims to study the impact of fuel properties on the spray and combustion processes of ABE mixture and alcohol fuels, blended with the diesel surrogate fuel, n-dodecane, in different volume ratio from 20% to 50%. A new combustion chamber called "New One Shot Engine," was designed and developed to reach the high-pressure and high temperatureconditions of "Spray-A" (60 bar, 800-900 K and 22.8 kg/m³) defined by the Engine Combustion Network (ECN).The macroscopic spray and combustion parameters were characterized by using the several optical techniques (extinction,Schlieren, chemiluminescence of OH*) under non-reactive (pure Nitrogen) and reactive (15% of oxygen) conditions. These experimental results not only made it possible to study the molecular oxygen impact and provide a new accurate database,but also to affirm the possibility of using ABE up to 20% by volume in compression-ignition engines, as its spray and combustion characteristics similar to conventional diesel fuel.

Cette thèse de doctorat traite de la mise en œuvre du procédé de soulèvement épitaxial (ou ELO pour epitaxial lift-off) à partir d'un substrat d'InP permettant le détachement des couches actives et le recyclage du substrat afin de rendre économiquement compétitive la fabrication de cellules solaires multi-jonctions pour le photovoltaïque concentré. Ce procédé, qui consiste à sous-graver sélectivement une couche sacrificielle comprise entre le substrat et les couches actives, est bien connu et maîtrisé sur un substrat de GaAs avec l'utilisation d'une couche sacrificielle d'AlAs d'épaisseur voisine de 5 nm, ce qui n'est pas possible sur un substrat d'InP en raison du fort désaccord de maille cristalline existant entre l'AlAs et l'InP. Pour l'adapter à un substrat d'InP, le développement d'une couche sacrificielle spécifique basée sur un super-réseau AlAs/InAlAs a été réalisé, ce qui permet de contourner les problématiques liées au désaccord de maille et à la croissance de matériaux contraints. Après optimisation des conditions de croissance de ce super-réseau, les épaisseurs atteintes et donc les vitesses de sous-gravure obtenues en utilisant ce type de couche sacrificielle ont satisfait aux exigences du procédé ELO. Ensuite, le report et le soulèvement de structures actives de cellules solaires InGaAs en couches minces cristallines ont été développés. Les cellules solaires ainsi fabriquées ont montré des performances semblables à celles réalisées par épitaxie standard sur un substrat d'InP, voire meilleures sous concentration en raison d'effets de confinement optique. Finalement, le recyclage du substrat d'InP réalisé avec un procédé utilisant seulement deux étapes de nettoyage par voies chimiques humides, a permis de produire des surfaces d'InP de qualité suffisante pour réaliser une reprise d'épitaxie satisfaisante. / This PhD thesis deals with the implementation of the epitaxial lift-off (ELO) process from an InP substrate allowing the detachment of active layers and the substrate recycling. The final target is to realize multi-junction solar cells in an economically competitive way for concentrated photovoltaic. The ELO process consists in the under-etching of a sacrificial layer inserted between the substrate and the active layers. It is well known and mastered on a GaAs substrate with the use of a sacrificial layer of AlAs with a thickness of about 5 nm. Such a layer is not usable on an InP substrate due to the high lattice mismatch between AlAs and InP. In order to adapt the ELO process to an InP substrate, this work aimed to develop a specific sacrificial layer based on an AlAs/InAlAs superlattice. Thus, it is possible to circumvent problems related to the lattice mismatch and to the strained layer growth. After optimization of growth conditions of this superlattice, using this type of sacrificial layer, we achieve a sufficient thickness and therefore a sufficient under-etching rate in order to meet the requirements of the ELO process. Then, the transfer and lift-off of thin crystalline film based InGaAs solar cells have been developed. This kind of solar cells showed performances similar to those obtained with a standard epitaxial growth on an InP substrate, or even better under concentration due to optical confinement effects. Finally, the recycling of the InP substrate carried out by a process using only two wet chemical cleaning steps made it possible to produce InP surfaces of sufficient quality to achieve a promising second epitaxial growth.

Trilayer polypyrrole microactuators that can operate in air have previously been developed. They consist of two outer layers ofthe electroactive polymer polypyrrole (PPy) and one inner layer of a porous poly(vinylidene flouride) (PVDF) membranecontaining a liquid electrolyte. The two outer layers of PPy are each connected with gold electrodes and separated by the porousPVDF membrane. This microtool is fabricated by bottom-up microfabrication However, porous PVDF layer is not compatible with bottom upmicrofabrication and highly swollen SPE suffers from gold electrode delamination. Hence, in this MSc project/thesis a novelmethod of flexible electrode fabrication with conducting polymers was developed by soft lithography and drop-on-demandprinting. The gold electrodes were replaced by patterned vapor phase polymerized (VPP) poly(3,4-ethylenedioxythiophene) (PEDOT)electrodes due to its high electrical conductivity and versatile process ability. The replacement of the stiff gold electrodes byflexible and stretchable PEDOT allowed high volume change of the material and motions. The PEDOT electrodes werefabricated by patterning the oxidant iron tosylate using microcontact printing and drop-on-demand printing. Moreover, thePVDF membrane has been replaced by a nitrile butadiene rubber/poly(ethylene oxide) semi-interpenetrating polymer network(IPN) to increase ion conductivity and strechability and hence actuator performance.

Nous étudions la possibilité de réaliser des cellules à base de diséléniure de cuivre, indium et gallium (CIGSe) à absorbeur ultra-mince, en réduisant l'épaisseur de la couche de CIGSe de 2500 nm jusqu'à 100 nm, tout en conservant un haut rendement de conversion.Grâce à l'utilisation d'outils de simulation numérique, nous étudions l'influence de la réduction d'épaisseur de l'absorbeur sur les paramètres photovoltaïques de la cellule. Une importante dégradation du rendement est observée, principalement attribuée à une réduction de la fraction de lumière absorbée par le CIGSe ainsi qu'à une collecte des porteurs de charge réduite dans les dispositifs ultraminces. Des solutions permettant de surmonter ces problèmes sont proposées et leur influence potentielle est numériquement simulée ; nous démontrons qu'une ingénierie de face avant (couche tampon alternative, couche anti-réfléchissante...) et de face arrière (contact arrière réfléchissant, diffusion de la lumière) sur une cellule CIGSe à absorbeur ultramince permet de potentiellement améliorer le rendement de la cellule solaire au niveau de celui d'une cellule à absorbeur référence (2.5 μm).Grâce à l'utilisation de techniques de gravure chimique sur des échantillons standards de CIGSe épais, nous réalisons des cellules solaires avec différentes épaisseurs d'absorbeurs, et nous étudions l'influence de l'épaisseur du CIGSe sur les paramètres photovoltaïques des cellules. Le comportement similaire aux simulations numériques.Une ingénierie du contact avant sur des cellules CIGSe à différentes épaisseurs est réalisée pour spécifiquement améliorer l'absorption dans la couche de CIGSe. Nous étudions l'influence d'une couche tampon alternative de ZnS, de la texturation de la fenêtre avant de ZnO:Al, et d'une couche anti-reflet sur la cellule solaire. D'importantes améliorations sont observées quelque soit l'épaisseur de la couche de CIGSe, ce qui permet d'obtenir des rendements de conversions supérieurs à ceux obtenus dans la configuration standard des dispositifs.Une ingénierie du contact arrière à basse température est également réalisée avec l'utilisation d'un procédé novateur combinant la gravure chimique du CIGSe avec un " lift-off " mécanique de la couche de CIGSe afin de la séparer du substrat de Molybdène. De nouveaux matériaux fortement réflecteur de lumière et précédemment incompatible avec le procédé de croissance du CIGSe sont utilisés comme contact arrière pour des cellules CIGSe ultra-minces. Une étude comparative en fonction de l'épaisseur de CIGSe entre des cellules avec contact arrière réfléchissant en Or (Au) et cellules solaires avec contact arrière standard Mo est effectuée. Le contact Au permet d'augmenter significativement le rendement de conversion des cellules solaires à absorbeur sub-microniques comparé au contact standard Mo avec un rendement de conversion supérieur à 10% obtenu sur une cellule CIGSe de 400 nm (comparé à 7.9% avec Mo).Afin de réduire encore plus l'épaisseur de la couche de CIGSe, jusque 100-200 nm, les modèles numériques montrent qu'il est nécessaire d'utiliser un réflecteur lambertien sur la face arrière de la cellule afin de maximiser l'absorption de la lumière. Un dispositif preuve de concept expérimental est réalisé avec une épaisseur de CIGSe de 200 nm et un réflecteur arrière lambertien, et ce dispositif est caractérisé par spectroscopie de transmission/réflexion. La réponse spectrale est déterminée en combinant des valeurs issues de simulation numérique et la mesure expérimental de l'absorption du dispositif. Nous calculons un courant de court circuit de 26 mA.cm-2 pour ce dispositif avec réflecteur lambertien, bien supérieur à ce qui est calculé pour la même structure sans réflecteur (15 mA.cm-2), et comparable au courant mesuré sur une cellule de référence de 2500 nm (28 mA.cm-2). L'utilisation de réflecteur lambertien pour des cellules CIGSe ultraminces est donc particulièrement adaptée pour maintenir de hauts rendements.

Entre els accidents greus que poden ocórrer a les instal·lacions industrials o durant el transport de substàncies perilloses, els dolls de foc presenten un especial interès. Tot i que tenen una distància relativament més curta d'afectació que altres accidents greus, es caracteritzen per originar grans fluxos de calor i, en cas de contacte de la flama amb un equip, originen sovint un efecte domino, desencadenant una subseqüent explosió, incendi o altres esdeveniments amb greus conseqüències.Diversos estudis experimentals i teòrics han estat efectuats; no obstant això, la majoria d'aquests han estat enfocats a dolls de foc a escala de laboratori, flames subsòniques o torxes, les condicions de les quals difereixen significativament d'aquelles trobades en dolls de foc accidentals reals, que normalment assoleixen majors longituds de flama i velocitats de sortida sònica. Aquesta manca d'investigació és la raó per explicar perquè els dolls de foc eren encara molt mal coneguts i la predicció dels seus efectes i conseqüències era encara un problema. Aquesta tesi ha estat elaborada per a obtenir informació nova i útil sobre els dolls de foc, millorant la comprensió de la seva geometría i de les característiques tèrmiques, mitjançant l'anàlisi, l'experimentació i el modelatge matemàtic.Aquest estudi s'ha centrat alhora en dades existents i en noves dades experimentals, implicant Aixa dolls de foc verticals i horitzontals alliberats en absència de vent, implicant diversos combustibles (hidrogen, metà i propà). L'estudi comprèn una àmplia gamma de variables d'operació (velocitats de sortida del combustible, pressions en la canonada i diàmetres d'orifici de sortida). L'estudi experimental ha implicat dolls de foc amb flames de fins a 10.3 m de longitud i 1.5 m d'amplada. El combustible utilitzat ha estat propà, amb velocitats de sortida sònica i subsònica, utilitzant diversos diàmetres d'orifici de sortida. Els dolls de foc han estat filmats amb dues càmeres de vídeo (VHS) i una càmera termográfica d'alta velocitat (IR). Les principals característiques geomètriques de les flames (dimensions i forma) han estat analitzades en funció de la velocitat de sortida del combustible,del flux màssic i del diàmetre d'orifici de sortida. L'anàlisi i tractament d'imatges infraroges i de les mesures obtingudes amb tres sensors de flux de calor situats a diferents distàncies de la sortida del doll de foc han permès l'obtenció de les seves principals característiques de radiació: flux de calor irradiat als voltants (persones i instal·lacions) en funció de la distancia, poder emissiu i emisivitat de les flames. Diverses expressions han estat proposades per estimar les dimensions de la flama en funció de diverses variables (flux màssic, diàmetre d'orifici de sortida i nombres de Froude i Reynolds). Els resultats i expressions obtinguts en aquest estudi contribueixen a una millor comprensió dels dolls de foc, representant un avanç en les metodologies i l'establiment de noves mesures, normes i polítiques de planificació per a la prevenció i/o el control d'aquest tipus d'accident greu amb foc, tant en establiments industrials com en el transport de materials perillosos. / Among the major accidents that can occur in processing plants or in the transportation of hazardous materials, jet fires are of particular interest. Although they have a relatively shorter distance of influence than other major accidents, they are characterized by high heat fluxes and if there is flame impingement they can originate a domino effect, leading to a subsequent explosion, large fire, or other events with severe effects. Several experimental and theoretical studies have been carried out; however, most of those works have been focused on small-scale jet fires, subsonic flames or flares, the conditions of which significantly differ from those found in real accidental jet fires, usually reaching larger flame lengths and sonic exit velocities. This lack of research is the reason to explain why the current knowledge of jet fires was still rather poor and the accurate prediction of their effects and consequences was still a problem. The present thesis has been addressed to produce a significant amount of novel and useful information on jet fires, by improving understanding of jet fire structure, reach and radiative features, through analyses, experiment and mathematical modelling. This study has been focused on both existing and also new experimental jet flame data, comprising all together, turbulent non-premixed jet flames vertically and horizontally released into still air, involving several fuels (hydrogen, methane and propane), over a wide range of operational conditions (jet exit velocities, release pressures and pipe diameters). The experimental study developed in this thesis has concerned relatively large jet fires with flames of up to 10.3 m in length and 1.5 m in width. The fuel was propane, and both sonic and subsonic jet exit velocities were obtained from different outlet diameters. The jet fires were filmed with two videocameras registering visible light (VHS) and a thermographic camera (IR). The main geometrical features of the flames were analyzed as a function of the fuel velocity, mass flow rate and jet outlet diameter: jet flame size and flame shape. The treatment of infrared images and measurements obtained from three heat flow sensors located at different distances from the jet fire outlet also led the main radiative features of jet fires to be obtained: incident thermal radiation heat over a target, surface emissive power and emissivity of the flames.Expressions for estimating jet flame reach as a function of several variables (mass flow rate, orifice exit diameter, Froude and Reynolds numbers) have also been proposed. The results and the expressions obtained in this study contribute to a better understanding of jet fires for accurate risk assessment, allowing the obtention of important advances in risk assessment methodologies and the establishment of new measures, regulations, and risk planning policies for the prevention and/or control of this type of major fire, occurred world-wide in industrial establishments and in the transportation of hazardous materials.

No description available.

Modelos algébricos para prever o comprimento de uma chama turbulenta têm sido foco de estudo de diversos grupos de pesquisa por suas aplicações na área de engenharia. O método experimental para obter o modelo varia desde visualizações simples, até técnicas fotográficas, este último com parâmetros fotográficos variando entre os autores. Técnicas fotográficas são usadas para estimar a altura de levantamento da base da chama, (Lift-Off) e o comprimento médio visível de chama (Visible Flame Length, VFL). Duas técnicas comuns que podem ser encontradas na literatura: por imagens de chama com baixo tempo de exposição e longo tempo de exposição, são comparados com um terceiro que se baseia na intensidade luminosa e na frequência de imagens de chama que ocupam um pixel. O melhor método foi utilizado para caracterizar o comportamento das chamas turbulentas de gás natural para diferentes regimes de velocidade do escoamento. Modelos algébricos que preveem o comprimento de chama, altura de levantamento e a velocidade crítica de extinção de chama são avaliados com os novos resultados experimentais. Logo após, os coeficientes numéricos dos melhores modelos algébricos são reajustados Finalmente, foram obtidos mapas de estabilidade relacionados à altura de levantamento e à velocidade crítica de extinção de chama para cada diâmetro em função da diluição com CO2 e do número adimensional de Reynolds. A terceira parte deste trabalho está focada no estudo da distribuição de radiação térmica. Em particular, foram consideradas três distâncias radiais medidas em comprimentos de chama (0,5 Lf, 1 Lf, 2 Lf) visando obter a distribuição do fluxo radiante experimental ao longo de um eixo vertical adjacente às chamas. Finalmente, os dados experimentais foram utilizados como dados de entrada em uma análise inversa com o objetivo de calcular os fatores de ponderação do modelo das múltiplas fontes ponderadas (por suas siglas em inglês WMPS). Nesta última parte, são apresentados frações radiantes e distribuições de fluxo de calor radiante de chamas de gás natural diluídas para diversas diluições com dióxido de carbono e diâmetros do queimador. / Predicting models for turbulent diffusion flame lengths have several applications driven the attention of many research groups. Since several studies use photographs to measure the flame length, with photographic parameters varying among authors, in other cases simple visualizations were used. It is important to explore possible discrepancies among measurement technics that could affect the results. Optical visualizations of turbulent diffusion flames are used to estimate the visible average flame length (VFL) and the lift-off. The study presents a study of three different methods to measure the VFL using optical techniques. The effect on the image of the main optic parameters such as focus, exposure time and ISO sensibility are analyzed. The VFL obtained with images in low exposure time and long exposure time are compared with a third optical method that is based on the luminous intensity and the frequency of flame images occupying a pixel. One method was used to characterize the behavior of turbulent diffusion flames of natural gas for a range of flames in function of the flow velocity. Universal non-dimensional models that describe the VFL, lift-off and the blow-out stability limit of gaseous jet diffusion flames in the still air have been compared with new experimental data. The numerical coefficients of the best models are adjusted. Finally, maps of stability related to lift-off and blow-out were obtained for each diameter in function of the dilution with CO2 and flow exit velocity expressed in non-dimensional Reynolds number The third part of this work focuses on the estimation of the thermal distribution of radiative flux from turbulent diffusion flames in laboratory-scale. The experimental measurements were gotten from the previous stability study. In particular, was considered three radial distances measured in flame lengths (0,5 Lf, 1 Lf, 2 Lf) aiming at obtaining the experimental radiant flux along a vertical axis adjacent to the flames. Finally, the experimental data was used as input data in an inverse analysis with the purpose of computing weight coefficients of the weighted multi-point source (WMPS) model. Then, experimental data that include: radiant fractions and radiative heat flux are presents for several flames with different dilutions with carbon dioxide and burner´s diameters.

Modelos algébricos para prever o comprimento de uma chama turbulenta têm sido foco de estudo de diversos grupos de pesquisa por suas aplicações na área de engenharia. O método experimental para obter o modelo varia desde visualizações simples, até técnicas fotográficas, este último com parâmetros fotográficos variando entre os autores. Técnicas fotográficas são usadas para estimar a altura de levantamento da base da chama, (Lift-Off) e o comprimento médio visível de chama (Visible Flame Length, VFL). Duas técnicas comuns que podem ser encontradas na literatura: por imagens de chama com baixo tempo de exposição e longo tempo de exposição, são comparados com um terceiro que se baseia na intensidade luminosa e na frequência de imagens de chama que ocupam um pixel. O melhor método foi utilizado para caracterizar o comportamento das chamas turbulentas de gás natural para diferentes regimes de velocidade do escoamento. Modelos algébricos que preveem o comprimento de chama, altura de levantamento e a velocidade crítica de extinção de chama são avaliados com os novos resultados experimentais. Logo após, os coeficientes numéricos dos melhores modelos algébricos são reajustados Finalmente, foram obtidos mapas de estabilidade relacionados à altura de levantamento e à velocidade crítica de extinção de chama para cada diâmetro em função da diluição com CO2 e do número adimensional de Reynolds. A terceira parte deste trabalho está focada no estudo da distribuição de radiação térmica. Em particular, foram consideradas três distâncias radiais medidas em comprimentos de chama (0,5 Lf, 1 Lf, 2 Lf) visando obter a distribuição do fluxo radiante experimental ao longo de um eixo vertical adjacente às chamas. Finalmente, os dados experimentais foram utilizados como dados de entrada em uma análise inversa com o objetivo de calcular os fatores de ponderação do modelo das múltiplas fontes ponderadas (por suas siglas em inglês WMPS). Nesta última parte, são apresentados frações radiantes e distribuições de fluxo de calor radiante de chamas de gás natural diluídas para diversas diluições com dióxido de carbono e diâmetros do queimador. / Predicting models for turbulent diffusion flame lengths have several applications driven the attention of many research groups. Since several studies use photographs to measure the flame length, with photographic parameters varying among authors, in other cases simple visualizations were used. It is important to explore possible discrepancies among measurement technics that could affect the results. Optical visualizations of turbulent diffusion flames are used to estimate the visible average flame length (VFL) and the lift-off. The study presents a study of three different methods to measure the VFL using optical techniques. The effect on the image of the main optic parameters such as focus, exposure time and ISO sensibility are analyzed. The VFL obtained with images in low exposure time and long exposure time are compared with a third optical method that is based on the luminous intensity and the frequency of flame images occupying a pixel. One method was used to characterize the behavior of turbulent diffusion flames of natural gas for a range of flames in function of the flow velocity. Universal non-dimensional models that describe the VFL, lift-off and the blow-out stability limit of gaseous jet diffusion flames in the still air have been compared with new experimental data. The numerical coefficients of the best models are adjusted. Finally, maps of stability related to lift-off and blow-out were obtained for each diameter in function of the dilution with CO2 and flow exit velocity expressed in non-dimensional Reynolds number The third part of this work focuses on the estimation of the thermal distribution of radiative flux from turbulent diffusion flames in laboratory-scale. The experimental measurements were gotten from the previous stability study. In particular, was considered three radial distances measured in flame lengths (0,5 Lf, 1 Lf, 2 Lf) aiming at obtaining the experimental radiant flux along a vertical axis adjacent to the flames. Finally, the experimental data was used as input data in an inverse analysis with the purpose of computing weight coefficients of the weighted multi-point source (WMPS) model. Then, experimental data that include: radiant fractions and radiative heat flux are presents for several flames with different dilutions with carbon dioxide and burner´s diameters.