Current simulations of atmospheric entry into both Mars and Earth atmospheres for the design of thermal protections systems (TPS) typically invoke conservative assumptions regarding surface-catalyzed recombination and the amount of energy deposited on the surface. The need to invoke such assumptions derives in part from lack of adequate experimental data on gas-surface interactions at trajectory relevant conditions. Addressing this issue, the University of Vermont's Plasma Test and Diagnostics Laboratory has done extensive work to measure atomic specie consumption by measuring the concentration gradient over various material surfaces. This thesis extends this work by attempting to directly diagnose molecular species production in air plasmas. A series of spectral models for the A-X and B-X systems of nitric oxide (NO), and the B-X system of boron monoxide (BO) have been developed. These models aim to predict line positions and strengths for the respective molecules in a way that is best suited for the diagnostic needs of the UVM facility. From the NO models, laser induced fluorescence strategies have been adapted with the intent of characterizing the relative quantity and thermodynamic state of NO produced bysurface-catalyzed recombination, while the BO model adds a diagnostic tool for the testing of diboride-based TPS materials. Boundary layer surveys of atomic nitrogen and NO have been carried out over water-cooled copper and nickel surfaces in air/argon plasmas. Translation temperatures and relative number densities throughout the boundary layer are reported. Additional tests were also conducted over a water-cooled copper surface to detect evidence of highly non-equilibrium effects in the form of excess population in elevated vibrational levels of the A-X system of NO. The tests showed that near the sample surface there is a much greater population in the v'' = 1ground state than is predicted by a Boltzmann distribution.

This study is dedicated to investigation of soot formed during combustion in diesel engine. Measurements were performed in a high speed direct injection optical diesel engine. Initially soot particle size, size distribution and soot volume fraction were investigated using time resolved laser induced incandescence (TR-LII) technique. For this study standard diesel fuel was used and measurements were performed for various injection timing and two different engine loads. Investigation showed that TR-LII is a powerful tool that can be used for characterization of in-cylinder soot in the engines. Subsequently TR-LII technique was developed to measure in-cylinder soot in two dimensional plane (planar laser induced incandescence PLII) and technique was combined with high speed imaging to investigate soot processes for ultra-low sulfur diesel (ULSD) and bio-fuel (RME). Two injection strategies of single and double injection were applied during these measurements. A high speed imaging technique was used to study the soot formation and oxidation during the combustion process within the cylinder and PLII was applied later in the stroke to study qualitatively the relative amount of un-oxidised soot that was left in the combustion chamber. In addition to PLII, TR-LII technique was used simultaneously to explore crank angle resolved variation of primary soot particle size and their size distribution during the expansion stroke. The same measurements were repeated for fuels with different composition investigating the relationship between the fuel properties and soot emission. Finally mathematical model for soot particle size and distribution width was modified by introducing assumption of multi-lognormal in-cylinder soot particle size distribution.

[pt] O presente trabalho apresenta uma análise experimental da combustão turbulenta de sprays de etanol, mediante o uso de técnicas de diagnóstico laser, em queimadores tipo obstáculo. São empregadas a fluorescência induzida por plano laser (PLIF) do radical hidroxila (OH), para mapear a frente de chama, a velocimetria por imagens de partículas (PIV), para determinar o campo de velocidades das gotas do spray e Shadowgraphy, para obter o diâmetro e velocidade de gota. Uma caracterização da estrutura do escoamento de ar a jusante do corpo rombudo é realizada com PIV estéreo para diferentes números de Reynolds. Os resultados mostram uma similitude do escoamento na zona de recirculação. As maiores flutuações turbulentas de velocidades são encontradas na região de vórtice e indicam anisotropia no tensor de Reynolds. Os resultados de Shadowgraphy revelam que as gotas do spray não são perfeitamente esféricas em regiões perto do atomizador. O diâmetro médio Sauter (SMD) foi medido em varias posições na região de recirculação. As gotas de maior diâmetro apresentaram as maiores velocidades e as pequenas são ligeiramente desviadas pela zona de recirculação nas regiões mais afastadas da linha central. Os experimentos reativos realizados com diversos valores de vazão de etanol e ar indicam que a frente de chama é descolada do queimador, sua forma é determinada principalmente pela vazão de etanol e a intensidade de luminescência é aumentada com a velocidade do ar. Em alguns casos o escoamento de ar muda a forma do spray. Uma quantidade de gotas apreciável sempre consegue atravessar a frente de chama. O campo de velocidade das gotas é influenciado pelo incremento da velocidade do escoamento anular de ar. / [en] This work presents an experimental analysis of turbulent combustion of ethanol sprays through the use of laser diagnostic techniques in a bluff-body burner. Are employed the planar laser-induced fluorescence (PLIF) of the hydroxyl (OH), to map the flame front, the particle image velocimetry (PIV) to determine the velocity field of the spray droplets and Shadowgraphy to obtain the droplet diameter and velocity. A characterization of the structure of the air flow downstream of the bluff-body is performed with stereo PIV at different Reynolds numbers. The results evidence flow similarity in the recirculation zone. The largest turbulent velocity fluctuations are found in the vortex region, which implies the anisotropy of the Reynolds stresses. The results of Shadowgraphy indicate that the spray droplets are not perfectly spherical near the atomizer. The evolution of Sauter mean diameter (SMD) is measured at various positions at the recirculation region. The largest diameter droplets have the highest velocity and the smaller are slightly deviated by recirculation zone in the far furthest from the centerline. The reactive experiments are performed with different ethanol and air flow rates and indicate that the flame front is detached from the burner, the shape is determined by the ethanol flow rate and the luminescence intensity increases with the air velocity. In some case the air flow changes the shape of the spray. An appreciable number of droplets always passe through the flame front. The velocity of the droplets is influenced by the increase of speed air velocity.

Sur Mars, la datation par comptage de densité de cratères est actuellement la seule méthode utilisée pour dater les surfaces planétaires. Cependant, sur Mars, elle n’a pas encore été corrigé et complété par des datations absolues. Ce travail consiste à développer un prototype démontrant le potentiel d’une nouvelle approche expérimentale basée sur la méthode K-Ar pour dater les roches martiennes in situ. L’objectif à terme est de proposer une solution instrumentale de datation absolue pour un futur rover d’exploration.Un laser Nd :YAG quadruplé pour tirer à 266 nm ablate un échantillon basaltique mis sous vide secondaire. L’observation du plasma par « Laser Induced Breakdown Spectroscopy » apporte des informations sur la concentration en K et sur la nature chimique et minéralogique de la cible. Puisque l’ablation est faite par un laser UV et sous vide secondaire, l’ablation est reproductible par minéralogie. La reconnaissance stoechiométrique permet donc d’estimer la masse vaporisée. Après purification des gaz libérés, un spectromètre de masse quadripolaire détermine la quantité d’argon.L’ensemble de ces mesures pourvoit un âge avec une incertitude théorique de 13% dans les meilleures conditions.Les calibrations du dispositif expérimental ont apporté de nombreuses informations sur des effets sur les spectres LIBS provoqués par l’ablation sous vide secondaire. L’augmentation de la pression e tla variation de géométrie du cratère d’ablation ont des effets opposés sur les pics des éléments.Nous avons aussi démontré que l’instrument était capable de mesurer l’âge de la mésostase de roche basaltique et qu’il offre des perspectives intéressantes sur certaines phases minérales comme la biotite. / Crater counting is the only method used on Mars to give relative geochronological information but it never had been fitted and corrected by absolute geochronology. This work is about the development of a new prototype demonstrating the ability of a protocol using in situ K-Ar dating. The goal is to propose a solution of an absolute geochronology for the next explorations rovers. A quadrupled Nd:YAG laser at 266 nm ablates a basaltic sample under high vacuum. The light collection by a spectrometer (Laser Induced Breakdown Spectroscopy) gives the rate of potassium and the chemical or the mineralogy of the target. Thanks to the specificities of the ablation in highvacuum and with a UV laser, the ablated mass has a good reproducibility per mineralogy. Thus, theLIBS identification gives an estimation of the ablated mass. After the purification of the released gas,a quadrupole mass spectrometer determines the quantity of argon. All these measures give an age with a theoretical uncertainty of 13% in the best conditions.The calibration of the experiment had given new information about the effects on LIBS spectrarelated to the ablation under high vacuum. The rise of the pressure and the variation of geometry of the pit have opposite effects on the elements peaks. We also demonstrated that the instrument was capable of measuring the age of the groundmass of basalt and has some interesting perspectives on some mineral phases such as biotite.

[pt] Neste trabalho se apresenta um estudo experimental e numérico de escoamentos turbulentos quimicamente reativos em um queimador tipo obstáculo. O objetivo principal é estudar uma chama turbulenta não pré-misturada de configuração geométrica simples. Esta chama, que queima gás natural e ar, é estabilizada por um queimador tipo obstáculo. Inicialmente um estudo bibliográfico do estado da arte de experimentos e da comparação entre experimentos e modelagem neste tipo de queimador é apresentado. Na sequência, a formulação matemática, clássica, de dinâmica dos fluidos computacional é exposta, seguida da apresentação da técnica de medição empregada nos experimentos, a fluorescência induzida por plano laser (PLIF). A discussão dos resultados obtidos neste trabalho é divida em três etapas. Na primeira, comparam-se os resultados de modelagem computacional usando quatro modelos de turbulência e dois modelos de combustão com dados experimentais encontrados na literatura. Esta comparação coloca em evidência o conjunto de modelos que possui melhor capacidade preditiva no que diz respeito a este tipo de configuração. A segunda etapa consiste na apresentação dos resultados experimentais obtidos, os quais permitem caracterizar, em três regimes de combustão distintos, a presença de uma espécie química existente durante o processo de combustão, no caso, o radical hidroxila (OH). Esta caracterização é realizada pelo exame tanto da estrutura instantânea da chama turbulenta quanto da média. Por fim, comparam-se os resultados da modelagem com aqueles obtidos no presente aparato experimental. Esta comparação coloca em evidência as deficiências dos modelos clássicos de combustão empregados e indica a necessidade de serem realizadas medidas simultâneas de velocidade e de concentração de espécies químicas que possibilitem o desenvolvimento de novos modelos de combustão em escoamento turbulento. / [en] This work presents an experimental and numerical study of turbulent chemically reactive flows in a bluff body type burner. The main objective of the present work is to study a non-premixed turbulent flame on a simple geometric configuration. This flame, which burns natural gas and air, is stabilized downstream to a bluff-body. Initially, literature is reviewed on the previous experimental and modeling studies which have been performed on this kind of burner. Then, the mathematical formulation of computational fluid dynamic problem is presented. This is followed by the introduction of the experimental measurements techniques which involve planar laser induced fluorescence (PLIF). The discussion of results obtained in this work is divided in three sections. First, a comparison is made between numerical simulations, using four different turbulent models and two different combustion models, and experimental data found in the literature. Is allows to assess capacity of the different models to predict the reactive flow configuration studied. The second section presents the experimental results obtained for three combustion regimes, which are characterized by laser induced fluorescence emission of the hydroxil radical species (OH). This characterization involves the analysis the instantaneous and the average structure of the turbulent flame. Finally, the modeling results are compared to the experimental data obtained. This comparison in evidences the necessity to perform the simultaneous measurement of velocity and chemical species concentration in order to allow for the development of new models of combustion in turbulent flows.

[pt] O escoamento em um queimador tipo corpo rombudo é estudado experimentalmente. Este queimador, representativo daqueles que podem ser encontrados em fornos industriais, propicia um amplo acesso óptico, fornecendo assim as condições necessárias para um estudo detalhado da combustão em escoamentos turbulentos. São realizadas medições simultâneas da luminosidade emitida pela fluorescência induzida do radical químico Hidroxila (OH) e do campo de velocidade do escoamento aplicando as técnicas de Fluorescência Induzida por Plano Laser (PLIF) e Velocimetria por Imagem de Partículas (PIV), respectivamente. A análise de incerteza das medições realizada mostrou que nos casos reativos as incertezas experimentais associadas às técnicas PIV e PLIF, são de 6 por cento e 25 por cento, respectivamente. O estudo de dois casos quimicamente inertes, um com o escoamento dominado pelo jato e outro pela esteira, serve de base para o cálculo das incertezas nas medições e na análise da estrutura do escoamento. Em seguida são estudados diversos regimes de combustão utilizando diferentes vazões de combustível gás natural e ar. As características da frente de chama e as estruturas do escoamento a jusante da superfície do queimador são analisadas através da distribuição da fluorescência de OH e dos campos de velocidade medidos. A imagem média permite verificar a posição do escoamento em que a chama se estabiliza, além de indicar a superfície de estequiometria e a altura média de ancoramento da chama. Os valores de RMS da fluorescência de OH indicam a flutuação da frente de chama, tanto na posição quanto na intensidade. Uma análise do tensor de Reynolds do escoamento é realizada à luz da hipótese de Boussinesq, ou seja, é investigada a pertinência do mecanismo de conexão entre a taxa de deformação média do escoamento e as tensões de Reynolds, a fim de examinar o desvio em relação à isotropia da turbulência. Os resultados dos casos reativos são semelhantes aos inertes. Assim sendo, a hipótese de Boussinesq parece ser aplicável nos casos em que o escoamento é dominado pelo jato, mas não quando ocorre interrupção deste na região de esteira. Os resultados apresentados contribuem para formação de um banco de dados que possibilitará a validação de novos modelos computacionais destinados a realização de simulações numéricas, visando a otimizar a combustão e propiciar a construção de queimadores mais eficientes que possibilitem a economia de combustível e a diminuição nas emissões de poluentes e material particulado. / [en] Turbulent non-premixed flames stabilized on a bluff-body burner are studied. This burner is representative of industrial furnace applications, provides ample optical access, allowing for the required conditions to perform a detailed combustion study in turbulent flowfield. Measurements of the fluorescence luminosity emitted by OH radical and the velocity field are achieved applying, Planar Laser Induced Fluorescence (PLIF) and Particle Image Velocimetry (PIV) techniques, respectively. An uncertainty analysis is presented considering specifically the reactive case, which yields experimental uncertainties associated to the PIV and PLIF techniques of 6 per cent and 25 per cent, respectively. The study of two chemically inert cases, the first dominated by jet and the second dominated by wake, supports the uncertainty calculations and the flowfield structure analysis. Subsequently, several combustion regimes using Natural Gas and air are studied. The flame front characteristics and flowfield structures are analyzed using the OH fluorescence distribution and measured velocity field. The mean images allow the determination of the flame stabilization position in the flowfield, and also indicate the stoichiometry surface and the mean lift-off height. The RMS values of fluorescence signal quantify the flame front fluctuation, both in position and intensity. The measured components of the Reynolds stress tensor are analyzed with respect to the Boussinesq hypothesis, i.e., the relation between mean strain rate and Reynolds stress tensor, in order to examine the tensor deviation from the isotropy. The Boussinesq hypothesis seems to be valid in cases where the jet is dominant and not valid when jet bursts in the wake region. The presented results are the first step towards the construction of a database to validate computational models aimed at optimizing the combustion process and designing more efficient burners.

Métodos convencionais para o estudo da combustão são geralmente métodos intrusivos (por exemplo, uso de termopares para medida da temperatura da chama), que acarretam distúrbios na queima (efeitos térmicos, catalíticos ou aerodinâmicos). As técnicas de diagnóstico utilizando lasers, além de serem não intrusivas, possuem uma alta resolução temporal e espacial que permite mapear a zona de combustão e identificar em cada ponto da chama os diversos estados em que se formam os radicais transientes. Neste trabalho foi estabelecida a técnica de fluorescência induzida por laser, LIF - \"Laser Induced Fluorescence\" - do radical OH para a determinação da temperatura em chamas de etanol/Oxigênio/ar. Esta técnica é bastante utilizada em outros países, mas no Brasil é inédita. Para o início dos estudos, foi construído um queimador para queima de combustíveis líquidos, produzindo chamas pré-misturadas. Foram testados esquemas de emissão de LIF (309,5 nm-311,5 nm) e de excitação de LIF, esta em duas regiões de absorção do radical OH A2\'sigma\'\'seta\'X2 \'pi\' (0,0) (303 nm e 309 nm) e A2\'sigma\'seta\'X2\'pi\'(1,0) (278 nm - 280 nm). Os melhores resultados foram obtidos pelo método de excitação de LIF na região das transições S21(1) - S21(13) da banda A2\'sigma\'X2\'pi\' (1,0), utilizando o gráfico de Boltzmann. Foram feitas medições em chamas de etanol em várias posições ao longo do seu eixo longitudinal, acima do queimador, e para vazões com razões de equivalência =1,0 = 1,4 e = 0,82. Os resultados foram comparados com os obtidos pela técnica da linha reversa utilizando um sal de sódio e apresentaram dados concordantes dentro dos erros experimentais. As temperaturas obtidas ao longo de 55 mm da chama de etanol variaram de 2008 K +- 40 K a 2246 K +- 90 K para razão de equivalência = 0,82; de 2198 K +- 65 K a 2295 K +- 127 K para razão de equivalência = 1,0 e de 1905 K +- 64 K a 2238 K +- 155 K para razão de equivalência = 1,4. Chamas de GLP também foram estudadas em 3 posições ao longo de 15 mm da chama com razões de equivalência, 1,0; 1,5 e 0,87. As temperaturas variaram de 2423 K +- 102 K a 2622 K +- 106 K para razão de equivalência = 0,87; de 2441 K +- 110 K a 2631 K +- 100 K para razão de equivalência = 1,0 e de 2403 K +- 109 K a 2605 K +- 124 K para razão de equivalência = 1,5. O presente estudo mostrou que a técnica de LIF é adequada para o mapeamento da temperatura de chamas, tanto de combustíveis gasosos quanto líquidos. As temperaturas obtidas apresentaram um desvio experimental menor do que 8 %. / Conventional methods for the study of combustion are usually intrusive methods (for example, the use of thermocouples to measure flame temperatures), which might disturb the burning process (thermal, catalytic or aerodynamic effects). The diagnostics techniques using lasers, in addition to being non-intrusive, have high temporal and spatial resolution. They allow the “mapping" of in which the combustion zone and the identification, at each point of the flame, the various states in which the transient radicals are formed. In this work, the technique of Laser Induced Fluorescence (LIF) was used. This technique is based on the spectral emission from the OH radical species for the determination of the temperature in ethanol/oxigênio/air flames. This technique is largely employed in other countries, but in Brazil it has not been employed to study combustion processes. In the first step of our studies, a liquid fuel burner was constructed, producing premixed flames. Experimental setups for LIF emission (309,5 nm - 311,5 nm) and excitation, in two regions of the OH radical absorption spectrum A-X (0,0) (303 nm and 309 nm) and A-X (1,0) (278 nm - 280 nm) were tested. The best results were obtained by excitation in the region of the transitions S21(1) - S21(13) of the A-X (1,0) band, using the plot of Boltzmann. Measurements in ethanol flames at different positions along the burner vertical axis were obtained, and for flowsrates with equivalence ratios 1.0; 1.4 and 0.82. The results were compared with those obtained with the sodium line-reversal technique and agree within the experimental error values. The temperature values measured throughout a 55 mm distance above the burner in the ethanol flame varied from 2008 K ± 40 K to 2246 K ± 90 K for equivalence ratio 0.82; from 2198 K ± 65 K to 2295 K ± 127 K for equivalence ratio 1.0 and from 1905 64 K ± to 2238 K ± 155 K for equivalence ratio 1.4. Mixture of propane/butane flames were also studied in three positions throughout a 15 mm distance above the burner for equivalence ratios,equivalence ratio 1.0 equivalence ratio = 1.5 and equivalence ratio 0.87. The temperatures measured varied from 2423 K ± 102 K to 2622 K ± 106 K for equivalence ratio 0.87; from 2441 K ± 110 K to 2631 K ± 100 K for equivalence ratio 1.0 and from 2403 K ±109 K to 2605 K ±124 K for equivalence ratio 1.5. The present study shows that the LIF technique is suitable for “mapping" flame temperatures of gaseous as well as liquid. The temperatures measured showed experimental deviations lower than 8 %.

abstract: Transient molecules are of great importance having proposed applications in quantum science and technology and tests of fundamental physics. In the present dissertation, the transient molecules studied are SrOH, ThF, ThCl, YbF and YbOH; each having been selected because of their proposed application. Specifically, SrOH is a candidate of constructing a molecular magneto-optical trap (MOT). The simple actinide molecules, ThF and ThCl, were selected as ligand bonding model systems to gain insight into chemical processing of Spent Nuclear Fuel. The lanthanides YbF and YbOH are venues for the determination of electron electric dipole moment (eEDM) and the studies in this dissertation provide the requisite properties for those experiments. Intense supersonic molecular beams of these transient molecules were generated via laser ablation and spectroscopically characterized using a novel medium-resolution two-dimensional (2D) spectroscopic approach, as well as high-resolution laser induced fluorescence (LIF). The 2D medium resolution approach, which was used in the studies SrOH, ThF, ThCl and YbOH, uses a multiplexing method that simultaneously records dispersed fluorescence and excitation spectra. A significant advantage of 2D-LIF imaging is that all the electronics states can be targeted to determine the electronics states and associated vibrational spacing individually. Consequently, in the 2D spectra of ThF, ThCl and YbOH, several previously unobserved band systems have been detected in one single scan. For the DF spectra of SrOH and YbOH, the determined branching ratios show that the transitions of these molecules are diagonal (i.e. Δv=0), which is essential for the proposed potential for laser cooling. In the high-resolution of YbF, ThF, ThCl and SrOH optical spectra were recorded to an accuracy of ±30 MHz, which represents an unprecedented precision of 1:10+8. In addition to field free spectra, optical Stark and Zeeman studies were performed to determine the most fundamental magneto-and electro-static properties. Effective Hamiltonian operators were employed to analyze the recorded spectra and determine the spectroscopic parameters. This data set also establishes a contribution toward developing new computational methodologies for treating relativistic effects and electron correlation. / Dissertation/Thesis / Doctoral Dissertation Chemistry 2019

An examination of the first laser-induced fluorescence measurements of ion-acoustic wave reflection is presented in this dissertation. The experiment is performed in a multipole cylinindrical chamber using singly-ionized argon (ArII) plasma produced by a means of a hot cathode. Ion-acoustic waves are launched from a mesh antenna and reflected/absorbed by a biased, solid boundary (electrode). A kinetic analysis of wave reflection is carried out through LIF's ability of resolving ion phase-space. A comparison between Langmuir probe and LIF diagnostics is presented, with complementary Electric-field probe measurements.

Shape memory alloys (SMAs) are a unique class of smart materials exhibiting extraordinary properties with a wide range of applications in engineering, biomedical, and aerospace technologies. In this study, an advanced, efficient, low-cost, and highly scalable laser-assisted imprinting method with low environmental impact to create thermally controllable surface patterns is reported. Two different imprinting methods were carried out mainly on Ni50Ti50 (at. %) SMAs by using a nanosecond pulsed Nd:YAG laser operating at 1064 nm wavelength and 10 Hz frequency. First, laser pulses at selected fluences were directly focused on the NiTi surface, which generated pressure pulses of up to a few gigapascal (GPa), and thus created micro-indents. Second, a suitable transparent overlay serving as a confining medium, a sacrificial layer, and a mesh grid was placed on the NiTi sample, whereafter the laser was focused through the confinement medium, ablating the sacrificial layer to create plasma and pressure, and thus pushing and transferring the grid pattern onto the sample. Scanning electron microscope (SEM) and laser profiler images show that surface patterns with tailorable sizes and high fidelity could be obtained. The depth of the patterns was shown to increase and later level off with the increase in laser power and irradiation time. Upon heating, the depth profile of the imprinted SMA surfaces changed where the maximum depth recovery ratio of 30 % was observed. Recovery ratio decreased and saturated at about 15 % when the number of pulses were increased. A numerical simulation of the laser irradiation process was performed showing that considerably high pressure and temperature could be generated depending on the laser fluence. The stress wave closely followed the rise time of the laser pulse to its peak value and followed by the rapid attenuation and dispersion of the stress through the sample.