Cette thèse présente le développement d’une méthode ALE pour la modélisation del’interaction laser–plasma. La particularité de cette méthode est l’utilisation d’une étape de projectiond’ordre élevé. Cette étape de projection consiste en une interpolation conservative des quantitésconservatives du maillage Lagrangien sur un maillage régularisé. Afin d’éviter les oscillationsnumériques non-physiques, les flux numériques d’ordre élevé sont combinés avec des fluxnumériques d’ordre moins élevé. Ces flux numériques sont obtenu en considérant les quantitésconservatives constantes par morceaux. Cette méthode pour la discrétisation cellule–centrée consisteà préserver les maximums locaux pour la densité, la vitesse et l’énergie interne. Aspects particuliersde la méthode sont appliquées pour la projection la quantité de mouvement pour la discrétisation’staggered’. Nous l’utilisons ici dans le cadre de la projection sous la forme de la méthode FluxCorrection Remapping (FCR). Dans cette thèse le volet applicatif concerne la modélisation del’interaction d’un laser énergétique avec de plasma et des matériaux microstructures. Un intérêtparticulier est porté à la modélisation de l’absorption du laser par une mousse de faible densité.L’absorption se fait à deux échelles spatiales simultanément. Ce modèle d’absorption laser à deuxéchelles est mis en oeuvre dans le code PALE hydrodynamique. Les simulations numériques de lavitesse de pénétration du laser dans une mousse à faible densité sont en bon accord avec lesdonnées expérimentales. / This thesis presents the overview and the original contributions to a high–orderArbitrary Lagrangian–Eulerian (ALE) method applicable for the laser–generated plasma modeling withthe focus to a remapping step of the ALE method. The remap is the conservative interpolation of theconservative quantities from a low–quality Lagrangian grid onto a better, smoothed one. To avoidnon–physical numerical oscillations, the high–order numerical fluxes of the reconstruction arecombined with the low–order (first–order) numerical fluxes produced by a standard donor remappingmethod. The proposed method for a cell–centered discretization preserves bounds for the density,velocity and specific internal energy by its construction. Particular symmetry–preserving aspects of themethod are applied for a staggered momentum remap. The application part of the thesis is devoted tothe laser radiation absorption modeling in plasmas and microstructures materials with the particularinterest in the laser absorption in low–density foams. The absorption is modeled on two spatial scalessimultaneously. This two–scale laser absorption model is implemented in the hydrodynamic codePALE. The numerical simulations of the velocity of laser penetration in a low–density foam are in agood agreement with the experimental data.

In the manufacturing process of float glass often atmospheric pressure chemical vapour deposition (APCVD) reactors are integrated on-line for the deposition of functional thin solid films. Such functional films have applications in architectural glass, flat panel displays and solar cells. As glass moves downstream in the process, the thin film is deposited at temperatures between 500 to 700°C. The high temperatures make it difficult to monitor the deposition process and thin film quality control is commonly done at the end of the line or at lower temperatures. A time delay therefore exists between the point of thin film deposition and subsequent quality control, which can lead to large quantities of defective product being produced before faults are detected. It is therefore desirable to monitor in the APCVD reactor for rapid feedback of unexpected deviations from desired process conditions, reaction progress and fault detection. High uniformity of film properties across the substrate are important, but APCVD reactors are often empirically designed and the detailed chemical reaction mechanism is unknown. This leads to inefficient gas flow patterns and precursor utilization as well as difficulties in the design of new reactors. The APCVD deposition of tin oxide from the mono-butyl-tin tri-chloride (MBTC) is an example of such a process. Optical monitoring instruments in-situ and in-line on the APCVD reactor provided rapid feedback about process stability and progress non-invasively. Near infrared diode laser absorption spectroscopy (NIR-LAS) monitored the concentration of the reaction species hydrogen chloride (HCl) in-situ and spatially in the coating zone. A mid-infrared grating absorption spectrometer (IR-GAS) with novel pyro-electric array detector monitored the concentration of precursor entering the coating system simultaneously. In combination these instruments provide the means for rapid process feedback. Fourier transform infrared absorption spectroscopy (FTIR) was used to investigate the unknown decomposition pathway of the precursor to find the yet unknown key tin radical that initiates film growth. Stable species forming during MBTC decomposition over a temperature range of 170 to 760°C were investigated but the tin intermediate remains unknown. Computational fluid dynamics (CFD) is routinely employed in research and industry for the numerical simulation of CVD processes in order to predict reactor flow patterns, deposition rates, chemical species distribution or temperature profiles. Two and three dimensional models with complex geometries and detailed reaction models exist. A three dimensional computational fluid dynamics (CFD) model of the used APCVD reactor was built using the Fluent CFD software. The numerical simulation included a chemical model that predicted qualitatively the chemical species distribution of hydrogen chloride in the gas phase. This was confirmed through comparison with NIR-LAS results. Design shortcomings due to inefficient flow patterns were also identified. In combination the optical tools developed provide the means for safe and efficient manufacturing of thin films in APCVD reactors. CFD simulations can be used to increase precursor utilization and film uniformity in the development of new reactor designs.

This PhD thesis is an analysis of the chemical kinetics and oxidation behavior of fuel components via experiments and correlations. First, a number of experimental studies of the reactivity of OH radicals with unsaturated hydrocarbons are performed at temperatures ranging from 294 to 1400 K by OH absorption and laser induced fluorescence techniques in two different reactors: shock tube and flow reactor. It is found that OH has a tendency to add to the unsaturated CC bond, forming a relatively stable adduct. The thermal stability of these adducts is vital for a better understanding of the kinetics of olefins, poly-olefins, alkynes and other unsaturated components in real and surrogate fuel blends. In this work, the reaction rate coefficient of the reaction of hydroxyl radical with many olefins (butenes, pentenes, hexenes), di-olefins (butadienes, and pentadienes) and allyl radical are measured. A strong competition between H-abstraction and OH-addition pathways is seen particularly in the intermediate temperature window of ~ 400 to 900 K. All of these measured elementary reactions give new insights into the chemical kinetics of fuels and allow modelers to improve the predictive capability of their models. Second, measurements of the ignition delay times of propene, isobutene, 2-methylhexane and 2-methylbutanol in air are performed using a high-pressure shock tube. Details about multi-stage ignition and ignition delay dependence on various thermodynamic properties is investigated for these four hydrocarbons. We followed this with a correlation study of ignition delay times of fuel blends and real fuel streams. The main requirement of these correlations is that these should be predictive enough to compete with the predictive capabilities of detailed chemical kinetic models but at a much reduced computational cost. The obtained correlation scheme does not only predict ignition timing during CFD simulations but also other combustion properties such as low-temperature heat release timing and resulting temperature and pressure increases due to cool flame. A discussion on the weak dependence of high-temperature ignition delay times on the composition of real fuels is also presented, where universal Arrhenius type expressions of ignition delay times of gasoline, diesel and jet fuels are given.

Energy demand is rapidly increasing due to the increase in population and rising living standards. Petroleum-based fuels account for the main source of energy consumed in the world. However, they are also considered to be the main source of the unwanted emissions to the atmosphere. In this context, chemical kinetic studies of combustion processes are essential for a better understanding of the underlying reactions and to achieve increased combustion efficiency and reduced pollutant emissions. In this study, ignition delay times, a global indicator of fuel reactivity, were measured for promising fuels for use in advanced combustion engines. Also, rate coefficients were measured for promising oxygenated hydrocarbons that can be used as additives to conventional fuels. Ignition delay time measurements of four primary reference fuel (PRF) blends, mixtures considered to be some of the simplest gasoline surrogates, were measured behind reflected shock waves to provide a large experimental dataset to validate PRF chemical kinetic models. The kinetic modeling predictions from four chemical kinetic models were compared with the experimental data. Ignition delay correlations were also developed to reduce the simulation cost of complicated models. Recently, naphtha, a low-octane distillate fuel, has been proposed as a low-cost refinery fuel. Likewise, a mid-octane blend which consists of low-octane (light and heavy naphtha) and high-octane (reformate) distillate fuels has been proposed to power gasoline compression ignition (GCI) engines. In this work, experimental and modeling studies were conducted on low and mid-octane distillate fuels (naphtha and GCI blend) and surrogate candidates to assess their autoignition characteristics for use in advanced internal combustion engines. Oxygenated molecules are considered to be promising additives to conventional fuels. Thermal decomposition of three esters (ethyl levulinate, ethyl propionate and diethyl carbonate ) and a five-member cyclic ketone (cyclopentanone) was investigated in this work. Laser absorption technique was employed to follow the reaction progress by measuring ethylene (C2H4) near 10.532 µm using a CO2 gas laser for the decomposition process of the three esters. The reaction progress of the decomposition of cyclopentanone was followed by monitoring CO formation using a quantum cascade laser at a wavelength near 4.556 µm.

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第21756号 / 工博第4573号 / 新制||工||1713(附属図書館) / 京都大学大学院工学研究科機械理工学専攻 / (主査)教授 蓮尾 昌裕, 教授 木村 健二, 教授 江利口 浩二 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

Laser absorption spectroscopy has been a valuable technique for sensitive, non-intrusive, in-situ detection of gaseous and liquid phase target species. The infrared spectral region is specifically attractive as it provides opportunities for selective sensing of a multitude of species in various applications. This thesis explores techniques for interference-free sensing in the infrared region for environmental, combustion, and petrochemical applications. A mid-infrared laser-based sensor was designed to detect trace amounts of benzene using off-axis cavity-enhanced absorption spectroscopy and a multidimensional linear regression algorithm. This sensor achieved unprecedented detection limits, making it ideal for environmental and occupational pollution monitoring. Moreover, wavelength tuning and deep neural networks were employed to differentiate between the broadband similar-shaped absorbance spectra of benzene, toluene, ethylbenzene, and xylene isomers. Benzene sensing was enhanced by recent advancement in semiconductor laser technology, which enabled access to the long wavelength mid-infrared region through commercial distributed feedback quantum cascade lasers. The strongest benzene absorbance band in the infrared is near 14.84 μm, and thus was probed for sensitive benzene detection. Wavelength tuning with multidimensional linear regression were employed to selectively measure benzene, carbon dioxide, and acetylene. Cepstral analysis and wavelength tuning were used to develop a selective sensor for fugitive methane emissions. The sensor was proved to be insensitive to baseline laser intensity imperfections and spectral interference from other present species. In combustion studies, it is desirable to have a diagnostic technique that can detect multiple species simultaneously with high sensitivity, selectivity, and fast time response to validate and improve chemical kinetic mechanisms. A mid-infrared laser sensor was developed for selective and sensitive benzene, toluene, ethylbenzene, and xylenes detection in high-temperature shock tube experiments using deep neural networks. The laser was tuned near 3.3 μm, and an off-axis cavity-enhanced absorption spectroscopy setup was used to enable trace detection. Finally, a novel near-infrared laser-based sensor was developed for water-cut sensing in oil-water flow. The sensor was shown to be immune to the presence of salt and sand in the flow and to temperature variations over 25-60°C. This technique has significant advantages for well and reservoir management, where highly accurate water-cut measurements are required.

<p dir="ltr">This work presents the development and application of novel laser absorption spectroscopy sensors that were deployed to make high-rate (1-15 kHz) measurements of temperature, CO, NO, CO₂, and air-fuel ratio in internal combustion engine (ICE) systems. These sensors provided measurements with unprecedented time resolution in ICE exhaust that allowed for individual cylinder firing events to be detected which will greatly improve understanding of ICE systems and allow for emissions reduction strategies to be tested. </p>

This thesis describes the development of a sensing technique for temperature nonuniformity along the line of sight through combustion exhaust, geared for gas turbine applications. Tunable diode laser absorption spectroscopy is used to measure three absorption lines and compute a variable to characterize the level of temperature nonuniformity along the laser path. Nonuniformity information is obtained from one line of sight sensor because the absorption has a nonlinear dependence on temperature. This dependence is analyzed to determine the behaviour, shape, and response of absorption lines measured through mediums with nonuniform temperature profiles. Based on this analysis a new line selection process for nonuniformity sensing is developed. A sensor for temperature nonuniformity is proposed and demonstrated through computer simulations and experiments in the exhaust of a laboratory-scale combustor. The nonuniformity variable, U, is shown to monotonically track the level of temperature nonuniformity along the laser path. The capabilities of this sensing technique are determined based on a comprehensive analysis of errors and their effect on sensor performance. Methods to mitigate these errors are described, and the overall sensor capability is determined based on the characteristics of state of the art diode laser and absorption sensor technology. Such a sensor is capable of measuring minimum temperature deviations of 17% or more, which is well within the needed capabilities for industrial applications. Furthermore, the results and knowledge presented in this thesis apply to other absorption based sensing techniques.

No description available.

The nature of work conducted during the course of study towards a MSc degree focused on tunable diode laser absorption spectroscopy (TDLAS). This field involves the in-situ detection of gas constituents from low concentration samples. Specifically, I will focus on TDLAS systems utilizing practical optics, readymade electronics, and commercially available near infrared vertical cavity surface emitting lasers (VCSEL). In attempting to lower the minimum detectable concentrations of constituent gases, quantifying contributory noise sources is vital. Consequently, I seek to characterize principle noise sources of a prototypical TDLAS system in order to gain understanding of the limits that inhibit detection of trace gas concentrations. The noise sources which were focused on can be categorized as follows: source laser noise, optical noise, and detection noise. Through this work it was my goal to provide the means of achieving superior sensitivities.