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Urzay, Javier. "Theoretical studies in spiral edge-flame propagation and particle hydrodynamics." Diss., [La Jolla] : University of California, San Diego, 2010. http://wwwlib.umi.com/cr/ucsd/fullcit?p3398270.
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Thesis (Ph. D.)--University of California, San Diego, 2010.Title from first page of PDF file (viewed May 6, 2010). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references.
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Proust, Christophe. "Contribution à l'étude des mécanismes de propagation des flammes dans les mélanges hétérogènes gaz-particules solides." Poitiers, 1988. http://www.theses.fr/1988POIT2268.
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Etude de la propagation d'une flamme laminaire air-particules d'amidon dans un tube. Determination des grandeurs caracteristiques de la flamme. Un des processus possibles de propagation des flammes dans les melanges air-particules d'amidon est celui des ondes de combustion dans les premelanges gazeux
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Li, Dan Chemical Sciences & Engineering Faculty of Engineering UNSW. "Designing functional magnetic nanoparticles with flame spray pyrolysis for bio-applications." Publisher:University of New South Wales. Chemical Sciences & Engineering, 2009. http://handle.unsw.edu.au/1959.4/43346.
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Magnetic nanoparticles (MNPs) hold great promise in the fields of biology and medicine. The synthesis of functional MNPs with precisely controlled crystallographic, physicochemical, and magnetic properties on a large scale still remains the challenge today. This thesis reports the exploration of liquid-fed flame spray pyrolysis (FSP) in the synthesis of functional MNPs, their surface modifications, and potential bio-applications. Superparamagnetic and ferromagnetic maghemite (γ-Fe2O3) nanoparticles, and silica-coated maghemite (SiO2/γ-Fe2O3) nanocomposites were synthesised using FSP. The size of γ-Fe2O3 was controllable from 6 to 53 nm, with morphology evolving from a disordered near-spherical shape to fully ordered 2-D hexagonal/octagonal platelet. The saturation magnetisation (Ms) increased from 21 to 74 emu/g with increasing particle size, up to 13 nm when Ms approached the bulk γ-Fe2O3 characteristics. In the case of SiO2/γ-Fe2O3, three distinct morphologies, namely the single segregated γ-Fe2O3 core- SiO2 shell, transitional mixed morphologies, and multi γ-Fe2O3 cores embedded in submicron SiO2 shell, were obtained. The core size, composite size, and morphology of γ- Fe2O3 were tunable by varying %SiO2 loading and the use of a quartz tube enclosure during flame synthesis. The magnetic behaviour correlated well with the crystal microstructure. Following the core particle design, protein adsorption-desorption behaviour on FSP-madeMNPs was studied. Bovine serum albumin (BSA) adsorption was found to follow the Langmuir isotherm, with high binding capacities (150−348 mg BSA/g particle) and fast association constants. Electrostatically governed BSA orientations were proposed for different particle-buffer systems. The adsorbed BSA was effectively recovered by pH-shift using K2HPO4. Subsequently, terminal amine, aldehyde, carboxylic, epoxy, mercapto and maleimide functionality were anchored onto the FSP-made γ-Fe2O3 particles. These versatile functional groups led to conjugation of active trypsin. The immobilised trypsin exhibited superior durability with >60% residual activity after one week, and excellent reusability for >5 cycles. The trypsin-conjugated MNPs are promising carriers in proteomics, demonstrating good substrate specificity with equivalent or better sequence coverage compared to free trypsin in insulin and BSA digestion. In another application, a refined silanisation procedure simultaneously reduced γ-Fe2O3 to Fe3O4, and generated thiol enriched surface for matrix metalloproteinase-2 (MMP-2) conjugation. The highly active MMP-2-conjugated MNPs could potentially enhance the interstitial transport of macromolecule/nanoparticles in drug delivery.
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Kerl, Johannes. "Development of a particle image velocimetry technique for three-dimensional flame structure analysis." Thesis, Imperial College London, 2013. http://hdl.handle.net/10044/1/18803.
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A technique for the measurement of three-dimensional quantities in turbulent premixed flames was developed. The need for this information arises when a deeper understanding of the flame-flow interactions is sought. As yet, information was mostly obtained in a two-dimensional manner using planar laser light sheet based measurement techniques. Although they are well established, the data gained is only a projection of the reality into a two-dimensional plane. In an effort to gather truly three-dimensional quantities, four laser light sheets have been crossed in a single line and particle image velocimetry (PIV) has been performed in each of them. By using the vaporisation of seeded silicon oil droplets at the flame front, the flame structure can be extracted as additional information. Combining the information about velocity and flame structure, flame displacement speeds were deduced. For the separation of the four laser light sheets, different wavelengths and polarisations were used. The readily available frequency doubled output of a Nd:YAG laser at 532 nm was utilised to illuminate two of the light sheets, separating them by polarisation. A third light sheet was produced with the frequency-tripled output of another Nd:YAG laser at 355 nm. To create the fourth light sheet, a solid state external Raman laser with barium nitrate as the active material was set up. This quad-crossed plane PIV experiment was applied in a model flame stabilised in a diffuser type combustor, which involves decelerating the premixed methane/air flow to a point where the flow velocity matches the turbulent burning velocity and therefore results in a rather flat reaction zone. The diffuser was made from quartz glass to allow optical access. The information gained was compared to established theories and numerical simulation results. Furthermore, a comparison of three-dimensional and two-dimensional data was performed to critically analyse the significance of two-dimensional measurements.
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Marshall, Andrew. "Turbulent flame propagation characteristics of high hydrogen content fuels." Diss., Georgia Institute of Technology, 2015. http://hdl.handle.net/1853/53859.
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Increasingly stringent pollution and emission controls have caused a rise in the use of combustors operating under lean, premixed conditions. Operating lean (excess air) lowers the level of nitrous oxides (NOx) emitted to the environment. In addition, concerns over climate change due to increased carbon dioxide (CO2) emissions and the need for energy independence in the United States have spurred interest in developing combustors capable of operating with a wide range of fuel compositions. One method to decrease the carbon footprint of modern combustors is the use of high hydrogen content (HHC) fuels. The objective of this research is to develop tools to better understand the physics of turbulent flame propagation in highly stretch sensitive premixed flames in order to predict their behavior at conditions realistic to the environment of gas turbine combustors.
This thesis presents the results of an experimental study into the flame propagation characteristics of highly stretch-sensitive, turbulent premixed flames generated in a low swirl burner (LSB). This study uses a scaling law, developed in an earlier thesis from leading point concepts for turbulent premixed flames, to collapse turbulent flame speed data over a wide range of conditions. The flow and flame structure are characterized using high speed particle image velocimetry (PIV) over a wide range of fuel compositions, mean flow velocities, and turbulence levels. The first part of this study looks at turbulent flame speeds for these mixtures and applies the previously developed leading points scaling model in order to test its validity in an alternate geometry. The model was found to collapse the turbulent flame speed data over a wide range of fuel compositions and turbulence levels, giving merit to the leading points model as a method that can produce meaningful results with different geometries and turbulent flame speed definitions. The second part of this thesis examines flame front topologies and stretch statistics of these highly stretch sensitive, turbulent premixed flames. Instantaneous flame front locations and local flow velocities are used to calculate flame curvatures and tangential strain rates. Statistics of these two quantities are calculated both over the entire flame surface and also conditioned at the leading points of the flames. Results presented do not support the arguments made in the development of the leading points model. Only minor effects of fuel composition are noted on curvature statistics, which are mostly dominated by the turbulence. There is a stronger sensitivity for tangential strain rate statistics, however, time-averaged values are still well below the values hypothesized from the leading points model. The results of this study emphasize the importance of local flame topology measurements towards the development of predictive models of the turbulent flame speed.
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Bouvet, Nicolas. "Etude des vitesses fondamentales des flammes laminaires prémélangées : application aux mélanges méthane/air et syngas (H2/CO)/air." Thesis, Orléans, 2009. http://www.theses.fr/2009ORLE2078.
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Cette étude est consacrée à l'élaboration d'une méthodologie de détermination des vitessesfondamentales des flammes laminaires, en utilisant un diagnostic de Vélocimétrie par Imagerie deParticules (PIV). Ce dernier est appliqué aux écoulements réactifs avec point de stagnation, permettant lastabilisation de flammes planes, stationnaires et en conditions quasi adiabatiques. Les effets d’étirementssubits par la flamme sont également quantifiables et parfaitement maîtrisés. L’approche ici développée atout d’abord été appliquée aux mélanges méthane/air pour validation. Une comparaison exhaustive desrésultats obtenus avec les données de la littérature est effectuée. Les codes de combustion 1D (PREMIX,OPPDIF) et 2D (Fluent©) ont été utilisés afin de confirmer la fiabilité et la précision de l’approche proposée.Une attention particulière a été accordée à la caractérisation du mouvement des particules ensemencéesdans les écoulements réactifs divergents, avec notamment la prise en considération de la force dethermophorèse. La méthode développée a ensuite été appliquée à la détermination des vitesses deflammes laminaires de divers mélanges de syngas (H2+CO). Une étude comparative sur ces mélanges aété conduite en utilisant des approches expérimentales multiples comprenant : les flammes à contrecourant,les flammes à propagation sphérique ainsi que les flammes stabilisées coniques. Les résultatsobtenus pour chaque approche ont été confrontés et la sensibilité à l’étirement des flammes de syngas aété caractérisée pour une large gamme de richesses (E.R.=0.4 to 5.0) et de compositions de mélanges(5/95 to 50/50 % H2/CO)In the context of CO2 emission reduction, the present study is devoted to the development of alaminar flame speed measurement methodology, using the Digital Particle Image Velocimetry (DPIV)diagnostic. The latter is applied to stagnation flow flames, seen to have considerable assets for suchstudies. Indeed, flames stabilized in these diverging flows are planar, steady and in near-adiabaticconditions, while subtraction of strain effects on flame is intrinsically allowed. The methodology developedherein has been applied to the well-characterized methane/air mixtures for validation. An extensivecomparison with the literature datasets has been provided. Both 1D (PREMIX, OPPDIF) as well as 2D(Fluent©) numerical tools have been used to confirm the reliability and accuracy of the developed approach.A particular attention has been given to the characterization of the seeding particle motion within thediverging flow, with consideration of the often-neglected thermophoretic force. Fundamental flame velocitiesof various syngas (H2+CO) mixtures have been investigated using multiple experimental approachesincluding the aforementioned counterflow methodology as well as spherical and conical flameconfigurations. Performed measurements from the different approaches have been confronted and flamesensitivities to stretch have been characterized for a wide range of equivalence ratios (E.R.=0.4 to 5.0) andmixture compositions (5/95 to 50/50 % H2/CO)
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Idris, Mahmoud [Verfasser]. "Two-Colour Pyrometer Technique for Coal-Particle Temperature Measurements in a Pulverised Coal Flame / Mahmoud Idris." Aachen : Shaker, 2004. http://d-nb.info/1181603501/34.
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Maugendre, Mathieu. "Etude des particules de suie dans les flammes de kérosène et de diester." Thesis, Rouen, INSA, 2009. http://www.theses.fr/2009ISAM0016/document.
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Les suies se présentent sous la forme de fines particules carbonées de diamètres compris entre quelques dizaines de nanomètres à quelques micromètres. Dans l’atmosphère, elles entraînent des enjeux climatiques, de par leurs propriétés radiatives, mais aussi des enjeux sanitaires, du fait de leur faible taille : elles pénètrent facilement dans le système respiratoire et même, pour les plus fines, dans le système sanguin. L’objectif est de parfaire les connaissances sur les propriétés physiques des suies produites par différents systèmes de combustion. C’est dans le but de mieux comprendre l’influence des systèmes de combustion, faisant intervenir des temps de séjours différents, des propriétés de turbulence, d’oxydation et de pression distinctes que nous avons choisi d’étudier trois types de combustion spécifiques : d’une part, des flammes de diffusion laminaires à pression atmosphérique, initiées dans un brûleur développé au cours de ces travaux ; d’autre part, une flamme de diffusion laminaire sous atmosphère pressurisée (3 à 5 bars) ; enfin, une flamme turbulente produite par une chambre tubulaire, elle aussi sous atmosphère pressurisée (1.2 à 3 bar). Un autre enjeu de ce travail était d’approfondir les informations relatives à la combustion de carburants liquides, à savoir le kérosène et le diester. Les travaux effectués visent à déterminer les caractéristiques morphologiques (dimension fractale, diamètre des monomères...) et l’indice complexe m* des suies issues des différents systèmes de combustion. La technique employée pour la mesure de l’indice complexe de réfraction des suies, repose sur l’analyse d’une partie des fumées produites par les flammes. Ces fumées sont acheminées dans un banc d’analyse permettant la mesure de signaux d’extinction et de diffusion, ainsi que de distributions de taille des suies. Par ailleurs, des analyses de clichés obtenus par microscope en transmission d’électrons (TEM) permettent l’obtention d’informations sur la morphologie des agrégats de suies. L’utilisation de la théorie de la diffusion de la lumière pour des agrégats fractals dans la limite de Rayleigh (RDG-FA) permet d’estimer à partir de ces données deux fonctions de l’indice complexe E(m) et F(m), et ainsi de retrouver m*Soot are carbonaceous fine particles, which diameters are ranged from a few nanometres to a few micrometers. They have an impact on climate, due to their radiative properties, as well as on health, due to their small size. That’s why particulate matter is an important concern. In order to gain a better understanding of the influence of the combustion devices, which implies specific residence time and also specific turbulence, oxidation and pressure properties, we studied three specific kinds of combustion : first, laminar diffusion flames at atmospheric pressure ; then, a laminar diffusion flame a high pressures (3 to 5 bar) ; finally, a turbulent flame produced in a combustor at high pressures (1,2 to 3 bar). Another objective of this work was to improve the knowledge about soot produced by the combustion of liquid fuels, namely kerosene and biofuel. We studied morphological properties (fractal dimension, primary particle size…) and the refractive index m* of soot produced by these combustion systems. The technique employed to characterize the soot refractive index is based on the analysis of a part of smokes produced by flames. These are transported towards two optical cells, so that extinction and scattering coefficients can be measured, in addition to soot size distributions. Furthermore, a morphological characterization of the aggregates is conducted, using transmission electron microscopy (TEM) photographs. Rayleigh-Debye-Gans theory for fractal aggregates is used to determine two functions of the refractive index E(m) and F(m), so that m* can be deduced
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Deng, Lei [Verfasser], and Andreas [Akademischer Betreuer] Kempf. "Numerical investigation of uncertainties in experiments for flame structure analysis and particle synthesis / Lei Deng ; Betreuer: Andreas Kempf." Duisburg, 2017. http://d-nb.info/1131551850/34.
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Seddon, Richard. "Influence of flame retardant additives on the processing characteristics and physical properties of ABS." Thesis, Loughborough University, 2000. https://dspace.lboro.ac.uk/2134/14228.
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Antimony trioxide (Sb203) and halogenated additives are used together in flameretarded formulations due to their synergistic retardant properties. A study has been made to determine the effects of adding different grades of Sb203 (dSD particle sizes 0.11 um, 0.52um and 1.31 um) into ABS polymer either alone or with commercial brominated materials (BTBPE, TBBA, DBDPO) and an experimental bromine grade (sDBDPO). The Sb20 3 was added at 4wt% loadings and the bromines at 20wt% loadings. The results consider the influence of the additives on processing, mechanical, morphological and flame retardant properties. All compounds were produced using a twin-screw co-rotating extruder and then an injection moulder was used to mould notched impact (falling weight testing), flexural, LOI and UL-94 flame test bars. Samples of all the compounded formulations were titrated to determine Sb20 3 and Br contents. Fracture surface, morphology, size and dispersion analysis was carried out using both SEM and TEM equipment. Osmium tetroxide (OS04) staining was used to determine relative locations of filler particles and polybutadiene phase. Additions of the different antimony trioxide grades showed that the 0.52um and 1.31 um grades lowered impact energy absorption (-25 to -30%) when added at 4wt% loading. The use of a sub-micron size grade (0.1 um) did not significantly lower impact properties (-3%) and had similarly small effects on the flexural modulus and flexural strength. Additions of the brominated materials had much greater effects causing large reductions in impact properties (-20 to :70%). The presence of the bromines generally increased flexural modulus and lowered flexural strength with the exception of TB BA, which increased both modulus and strength. Compounds containing both 1.31 um Sb203 and bromines suffered a further reduction in impact energies, with the bromine properties dominating. Using the 0.1 um Sb20 3 grade again improved impact and flexural properties compared to the 1.31 um grade. The 0.1 um grade resulted in improvements in fire resistance as measured by the UL-94 properties when used with all bromine grades.
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Wang, Zhong-Min. "Synthesis of Nanostructured Catalyst Powders and Thin Film Reactors by Flame Aerosol Deposition and Their Applications in Partial Oxidation." University of Cincinnati / OhioLINK, 2004. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1083637906.
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Pinchak, Matthew D. "Enhanced Flame Stability and Control: The Reacting Jet in Vitiated Cross-Flow and Ozone-Assisted Combustion." University of Cincinnati / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1522319737952261.
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Valencia, Correa Andres. "Etude expérimentale des concentrations de suie et des vitesses dans une flamme de paroi verticale." Thesis, Normandie, 2017. http://www.theses.fr/2017NORMR059/document.
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La propagation d’un incendie dans un espace clos s’explique par l’inflammation de matières combustibles. Un cas important est celui de la propagation d’une flamme sur une paroi verticale. En effet si la flamme progresse dans le même sens que l’écoulement (cas co-courant), la croissance est rapide. Dans ce cas, l’émission des vapeurs combustibles (pyrolyse) et le dégagement de la chaleur apportée par la combustion sont couplés par les flux convectés et rayonnés à la paroi. Ces flammes de paroi verticale sont pilotées par les forces de flottabilité, et se caractérisent par un régime de basse vitesse et avec une forte production de suie. Bien que de nombreux travaux aient été consacrés à l’étude des flammes de paroi verticale [1-3], peu d’entre eux ont été dédiés à l’étude de l’écoulement dans la couche limite proche de la paroi et à l’étude des zones de production de suie, lesquels sont des données nécessaires pour la validation des codes de calcul. Pour cela, des mesures simultanées de vitesse par PIV et de concentration de suie par LII ont été réalisées sur un brûleur gaz en configuration paroi-verticale. Dans un premier temps, ces mesures ont permis l’analyse de la forme, de la taille et de la concentration des zones de formation de suies (poches de suie) à différentes hauteurs dans la flamme. Ensuite, les champs 2D de vitesses moyennes (horizontales et verticales) ont été étudiés, ainsi que leurs fluctuations (densités de probabilité et écart-type). Une description de la couche limite réactive, à l’aide d’une échelle caractéristique obtenue avec des mesures de vitesse plus résolues spatialement (PIV « zoomé »), a également été réalisée. Finalement, les mesures de LII et PIV couplées ont permis d’étudier l’influence du champ de vitesse sur la distribution des suies dans la flamme, ainsi que le transport et le flux turbulent de la fraction volumique de suie dans la couche limite réactiveThe fire growth and spread on a confined space depends on the inflammation and combustion of combustible materials. An important case is the fire propagation on a vertical wall configuration, in which the pyrolysis gas and the total heat flux released by the flame are coupled by convective and radiative heat flux from the flame to the wall. This kind of flame is piloted by the buoyancy forces, and is characterized by a low velocity regime and a strong generation of soot particles. Although numerous works have been devoted on the study of vertical wall flames, few have been carried out on the analysis of the flame within the reactive boundary layer and the study of the zones of production of soot particles, which is data necessary for fire simulation codes validation. In this aim, simultaneous measurements of velocity by Particle Image Velocity (PIV) and of soot volume fraction by planar laser induced incandescence (LII) have been carried out on vertical wall fire generated by a vertical porous burner fed with a CH4/C2H4 mixture. First, the characteristics of soot sheet (shape, size, thickness, and peak concentration) have been studied at different heights into the flame, as well as the average and RMS soot volume fraction fields. Then, average and RMS fields of velocity and their probability density function have been analyzed. A description of the reactive boundary layer, through the definition of a characteristic velocity scale in the near-wall zone (viscous sub-layer), has been carried out by using a « PIV Zoom » set-up. Finally, simultaneous LII/PIV measurements have been carried out in order to study the influence of the aerodynamics of the flow on the soot volume fraction distribution, as well as the transport and turbulent flux of soot into the reactive boundary layer
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AGASHE, NIKHIL R. "IN-SITU SMALL ANGLE X-RAY SCATTERING STUDIES OF CONTINUOUS NANO-PARTICLE SYNTHESIS IN PREMIXED AND DIFFUSION FLAMES." University of Cincinnati / OhioLINK, 2004. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1092055991.
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Petrosky, Brian Joseph. "Particle Image Velocimetry Applications of Fluorescent Dye-Doped Particles." Thesis, Virginia Tech, 2015. http://hdl.handle.net/10919/52983.
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Laser flare can often be a major issue in particle image velocimetry (PIV) involving solid boundaries in a flow or a gas-liquid interface. The use of fluorescent light from dye-doped particles has been demonstrated in water applications, but reproducing the technique in an airflow is more difficult due to particle size constraints and safety concerns.
The following thesis is formatted in a hybrid manuscript style, including a full paper presenting the applications of fluorescent Kiton Red 620 (KR620)-doped polystyrene latex microspheres in PIV. These particles used are small and monodisperse, with a mean diameter of 0.87 μm. The KR620 dye exhibits much lower toxicity than other common fluorescent dyes, and would be safe to use in large flow facilities.
The first sections present a general introduction followed by a validation experiment using a standard PIV setup in a free jet. This work was the first to demonstrate PIV using fluorescent KR620-doped microspheres in an airflow, and results from the experiment were compared to similar data taken using standard PIV techniques. For the free jet results, Mie-scattered and fluorescent PIV were compared and showed average velocities within 3% of each other at the nozzle exit. Based on the PIV validation requirements used, this was deemed to be more of an indication of nozzle unsteadiness rather than an error or bias in the data. Furthermore, fluorescent PIV data obtained vector validation rates over 98%, well above the standard threshold of 95%.
The journal article expands on the introductory work and analyzes testing scenarios where fluorescent PIV allows for velocity measurements much closer to a solid surface than standard, Mie-scattered PIV. The fluorescent signal from the particles is measured on average to be 320 ± 10 times weaker than the Mie scattering signal from the particles. This fluorescence-to-Mie ratio was found to be nonuniform, with the typical signal ratio for a single particle expected to fall between 120 and 870. This reduction in signal is counterbalanced by greatly enhanced contrast via optical rejection of the incident laser wavelength. Fluorescent PIV with these particles is shown to eliminate laser flare near surfaces, in one case leading to 63 times fewer spurious velocity vectors than an optimized Mie scattering implementation in a region more than 5 mm from an angled surface.
In the appendix, a brief summary of an experiment to characterize the temperature sensitivity of the KR620 dye is included. This experiment concluded that the KR620 particles did not exhibit sufficient temperature sensitivity to warrant further investigation at the time.Master of Science
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Vaccaro, Danilo. "Experimental determination of burning velocity in metal dust explosions." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2021.
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The modeling of metal dust explosion phenomenon is important in order to safeguard industries from potential accidents. A key parameter of these models is the burning velocity, which represents the consumption rate of the reactants by the flame front, during the combustion process.
This work is focused on the experimental determination of aluminium burning velocity, through an alternative method, called "Direct method".
The study of the methods used and the results obtained is preceded by a general analysis on dust explosion phenomenon, flame propagation phenomenon, characteristics of the metals combustion process and standard methods for determining the burning velocity.
The “Direct method” requires a flame propagating through a tube recorded by high-speed cameras. Thus, the flame propagation test is carried out inside a vertical prototype made of glass. The study considers two optical technique: the direct visualization of the light emitted by the flame and the Particle Image Velocimetry (PIV) technique. These techniques were used simultaneously and allow the determination of two velocities: the flame propagation velocity and the flow velocity of the unburnt mixture. Since the burning velocity is defined by these two quantities, its direct determination is done by substracting the flow velocity of the fresh mixture from the flame propagation velocity. The results obtained by this direct determination, are approximated by a linear curve and different non-linear curves, which show a fluctuating behaviour of burning velocity.
Furthermore, the burning velocity is strongly affected by turbulence. Turbulence intensity can be evaluated from PIV technique data. A comparison between burning velocity and turbulence intensity highlighted that both have a similar trend.
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Hartl, Sandra. "Flamelet/progress variable modelling and flame structure analysis of partially premixed flames." Doctoral thesis, Technische Universitaet Bergakademie Freiberg Universitaetsbibliothek "Georgius Agricola", 2017. http://nbn-resolving.de/urn:nbn:de:bsz:105-qucosa-227684.
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This dissertation addresses the analysis of partially premixed flame configurations and the detection and characterization of their local flame regimes.
First, the identification of flame regimes in experimental data is intensively discussed. Current methods for combustion regime characterization, such as the flame index, rely on 3D gradient information that is not accessible with available experimental techniques. Here, a method is proposed for reaction zone detection and characterization, which can be applied to instantaneous 1D Raman/Rayleigh line measurements of major species and temperature as well as to the results of laminar and turbulent flame simulations, without the need for 3D gradient information. Several derived flame markers, namely the mixture fraction, the heat release rate and the chemical explosive mode, are combined to detect and characterize premixed versus non-premixed reaction zones. The methodology is developed and evaluated using fully resolved simulation data from laminar flames. The fully resolved 1D simulation data are spatially filtered to account for the difference in spatial resolution between the experiment and the simulation, and experimental uncertainty is superimposed onto the filtered numerical results to produce Raman/Rayleigh equivalent data. Then, starting from just the temperature and major species, a constrained homogeneous batch reactor calculation gives an approximation of the full thermochemical state at each sample location. Finally, the chemical explosive mode and the heat release rate are calculated from this approximated state and compared to those calculated directly from the simulation data. After successful validation, the approach is applied to Raman/Rayleigh line measurements from laminar counterflow flames, a mildly turbulent lifted flame and turbulent benchmark cases. The results confirm that the reaction zones can be reliably detected and characterized using experimental data. In contrast to other approaches, the presented methodology circumvents uncertainties arising from the use of limited gradient information and offers an alternative to known reaction zone identification methods.
Second, this work focuses on the flame structure of partially premixed dimethyl ether (DME) flames. DME flames form significant intermediate hydrocarbons in the reaction zone and are classified as the next more complex fuel candidate in research after methane. To simulate DME combustion processes, accurate predictions by computational combustion models are required. To evaluate such models and to identify appropriate flame regimes, numerical simulations are necessary. Therefore, fully resolved simulations of laminar dimethyl ether flames, defined by different levels of premixing, are performed. Further, the qualitative two-dimensional structures of the partially premixed DME flames are discussed and analyses are carried out at selected slices and compared to each other as well as to experimental data. Further, the flamelet/progress variable (FPV) approach is investigated to predict the partially premixed flame structures of the DME flames. In the context of the FPV approach, a rigorous analysis of the underlying manifold is carried out based on the newly developed regime identification approach and an a priori analysis. The most promising flamelet look-up table is chosen for the fully coupled tabulated chemistry simulations and the results are further compared to the fully resolved simulation data.
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Seltz, Andréa. "Application of deep learning to turbulent combustion modeling of real jet fuel for the numerical prediction of particulate emissions Direct mapping from LES resolved scales to filtered-flame generated manifolds using convolutional neural networks Solving the population balance equation for non-inertial particles dynamics using probability density function and neural networks: application to a sooting flame." Thesis, Normandie, 2020. http://www.theses.fr/2020NORMIR08.
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Face à l'urgence climatique, l’efficacité énergétique et la réduction des émissions polluantes est devenue une priorité pour l'industrie aéronautique. La précision de la modélisation des phénomènes physicochimiques joue un rôle critique dans qualité de la prédiction des émissions de suie et des gaz à effet de serre par les chambres de combustion. Dans ce contexte, des méthodes d’apprentissage profond sont utilisées pour construire des modélisations avancées des émissions de particules. Une méthode automatisée de réduction et d’optimisation de la cinétique chimique d’un combustible aéronautique réel est dans un premier temps appliquée à la simulation aux grandes échelles pour la prédiction des émissions de monoxyde de carbone. Ensuite, des réseaux de neurones sont entraînés pour simuler le comportement dynamique des suies dans la chambre de combustion et prédire la distribution de taille des particules émisesWith the climate change emergency, pollutant and fuel consumption reductions are now a priority for aircraft industries. In combustion chambers, the chemistry and soot modeling are critical to correctly quantify engines soot particles and greenhouse gases emissions. This thesis aimed at improving aircraft numerical pollutant tools, in terms of computational cost and prediction level, for engines high fidelity simulations. It was achieved by enhancing chemistry reduction tools, allowing to predict CO emissions of an aircraft engines at affordable cost for the industry. Next, a novel closure model for unresolved terms in the LES filtered transport equations is developed, based on neural networks (NN), to propose a better flame modeling. Then, an original soot model for engine high fidelity simulations is presented, also based on NN. This new model is applied to a one-dimensional premixed sooted flame, and finally to an industrial combustion chamber LES with measured soot comparison
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Arimboor, Chinnan Jacob. "Simulation and validation of in-cylinder combustion for a heavy-duty Otto gas engine using 3D-CFD technique." Thesis, KTH, Förbränningsmotorteknik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-245172.
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Utsläpp från bilar har spelat stor roll de senaste decennierna. Detta har lett till ökad användning av Otto gasmotorer som använder naturgas som bränsle. Nya motordesigner behöver optimeras för att förbättra motorens effektivitet. Ett effektivt sätt att göra detta på är genom användningen av simuleringar för att minska ledtiden i motorutvecklingen. Verifiering och validering av simuleringarna spelar stor roll för att bygga förtroende för och förutsägbarhet hos simuleringsresultaten. Syftet med detta examensarbete är att föreslå förbränningsmodellparametrarna efter utvärdering av olika kombinationer av förbrännings- och tändmodeller för Otto förbränning, vad gäller beräkningstid och noggrannhet. In-cylindertrycksspår från simulering och mätning jämförs för att hitta den bästa kombinationen av förbrännings- och tändmodell. Inverkan av tändtid, antal motorcykler och randvillkor för simuleringsresultatet studeras också. Resultaten visar att ECFM-förbränningsmodellen förutsäger simuleringsresultaten mer exakt när man jämför med mätningarna. Effekten av tändningstiden på olika kombinationer av förbrännings- och tändningsmodell utvärderas också. Stabiliteten hos olika förbränningssimuleringsmodeller diskuteras också under körning för fler motorcykler. Jämförelse av beräkningstid görs även för olika kombinationer av förbrännings- och tändmodeller. Resultaten visar också att flamspårningsmetoden med Euler är mer känslig för cellstorlek och kvalitet hos simuleringsnätet, jämfört med övriga studerade modeller. Rekommendationer och förslag ges om nät- och simulerings-inställningar för att prediktera förbränningen på ett så bra sätt som möjligt. Några möjliga förbättringsområden ges som framtida arbete för att förbättra noggrannheten i simuleringsresultaten.Emission from automobiles has been gaining importance for past few decades. This has gained a lot of impetus in search for alternate fuels among the automotive manufacturers. This led to the increase usage of Otto gas engine which uses natural gas as fuel. New engine designs have to be optimized for improving the engine efficiency. This led to usage of virtual simulations for reducing the lead time in the engine development. The verification and validation of actual phenomenon in the virtual simulations with respect to the physical measurements was quite important. The aim of this master thesis is to suggest the combustion model parameters after evaluating various combination of combustion and ignition models in terms of computational time and accuracy. In-cylinder pressure trace from the simulation is compared with the measurement in order to find the nest suited combination of combustion and ignition models. The influence of ignition timing, number of engine cycles and boundary conditions on the simulation results are also studied. Results showed that ECFM combustion model predicts the simulation results more accurately when compare to the measurements. Impact of ignition timing on various combination of combustion and ignition model is also assessed. Stability of various combustion simulation models is also discussed while running for more engine cycles. Comparison of computational time is also made for various combination of combustion and ignition models. Results also showed that the flame tracking method using Euler is dependent on the mesh resolution and the mesh quality. Recommendations and suggestions are given about the mesh and simulation settings for predicting the combustion simulation accurately. Some possible areas of improvement are given as future work for improving the accuracy of the simulation results.
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Bodor, Agnes Livia. "Numerical modelling of soot formation and evolution in laminar flames with detailed kinetics." Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLC050/document.
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Les suies de combustion sont principalement connues pour leur caractère nocif, dans le cas des feux de forêt, de fumées de cheminées ou d'émissions polluantes d'un tuyau d'échappement. Cependant, le noir de carbone, un produit industriel de combustion d'hydrocarbures largement utilisé dans notre vie quotidienne. La surface d'une particule de suies ou de noir de carbon joue un rôle important tant au niveau de son utilisation que de son effet nocif. Il est donc important de connaître la masse, le volume ainsi que la morphologie des suies. En particulier, la surface des particules est un paramètre important pour prédire leur utilisation ainsi que leur effet nocif. Les suies sont généralement des agrégats présentant une structure fractale constituée d'éléments de forme sphérique, appelés particules primaires. Il est possible de connaître la surface des agrégats à partir de la distribution en taille de particules primaires (PPSD-Primary particules size distribution). Compte tenu de l'intérêt grandissant pour la surface des particules et leurs évolutions, il est aujourd’hui nécessaire d'étendre les modèles numériques pour la prévision de la PPSD. De plus, comme la taille des la particules primaires influence les processus chimiques et les processus de collision, la prise en compte de ce paramètre peut améliorer les prévisions des modèles. Les flammes multidimensionnelles laminaires, comme les flammes de diffusion, sont moins complexes que les flammes rencontrées dans les systèmes de combustion industriels. Cependant, les processus de formation de suies sont analogues dans les deux cas, ce qui rend l'étude de ces flammes intéressante. Afin d'obtenir une description détaillée des processus chimiques ayant lieu dans ces flammes tout en maintenant le coût de calcul à un niveau abordable, l'utilisation de modèles sectionnels discrets chimiques (CDSchemical discret sectional methods) est un choix approprié. Le développement de modèles CDS est au coeur de cette thèse. D'abord, une stratégie numérique pour déterminer la taille des particules primaires est présentée dans le contexte des modéles CDS. Elle repose sur la résolution d'une équation de transport pour la densité en nombre de particules primaires pour chaque section d'agrégats considérée. Pour valider la taille des particules primaires déterminée numériquement, les résultats doivent être comparés avec des données expérimentales obtenues via la technique d'Incandescence Induite par Laser résolue temporellement (TiRe-LII). Cette comparaison, dite inverse, est affectée par les incertitudes expérimentales et les hypothèses sous-jacentes au post-traitement du signal TiRe-LII pour obtenir la PSD. Pour améliorer la stratégie de validation, une nouvelle approche, dite directe, est proposée pour la validation de la PPSD à partir des données obtenues par TiRe-LII. Elle est basée sur la reconstruction numérique de l'évolution temporelle du signal d'incandescence à partir des résultats numériques et de sa comparaison avec le signal mesuré. L'efficacité de l'approche proposée est démontrée a priori en évaluant l'erreur potentiellement évitée par la nouvelle stratégie. Le modèle proposé pour le suivi des particules primaires est ensuite validé en utilisant à la fois les approches ’directe’ et ’inverse’ sur les flammes cibles issues de l'International Sooting FlameWorkshop (ISF): une flamme pré-mélangée éthylèneair et une flamme de diffusion coflow avec deux dilutions différentes. Le caractère général du modèle est discuté en effectuant une étude de sensibilité des résultats aux paramètres du modèle même. Enfin, le modèle est utilisé pour comprendre l'effet de la dilution du combustible sur la taille des particules primaires dans les flammes de diffusion en examinant les corrélations possibles entre phase gazeuse et phase solide ainsi que l'évolution temporelle des particules le long de leur trajectoiresAn image appearing when the phrase soot is heard is the smoke emitted by an exhaust pipe. The imperfect combustion of hydrocarbon fuels is a source of this harmful pollutant. The industrially controlled combustion of hydrocarbons can provide the carbon black, an industrial product widely used in our everyday life. For both its utilization and its harming effect, the surface of these combustion generated particles plays an important role, therefore, it is of interest to possess information on the particle morphology beside its mass or volume. Soot particles were found, at various conditions, to have a fractal-like structure built up from spherical shape building blocks, socalled primary particles. This increased interest in the particle surface and its evolution gives the motivation to extend numerical models to provide related information, i.e. particle surface or primary particle size. Furthermore, as the primary particle size influences the chemical and collisional processes, accounting for this parameter can improve the model predictions. The requirements for numerical models are various depending on the purpose of the simulation. Multidimensional laminar flames, like a laminar coflow diffusion flame, are less complex than flames of industrial combustion systems. However, the soot formation processes are analogous in the two cases, therefore, the investigation of these flames are of interest. In order to obtain a detailed description of the chemical processes, while keeping the computational cost in these flames at an affordable level, using chemical discrete sectional models is a suitable choice. As in their current version, these models do not provide information on the primary particle size their development in this direction is of interest. Guided by the above motivation, a numerical strategy to determine the primary particle size is presented in the context of the chemical sectional models. The proposed strategy is based on solving the transport equation of the primary particle number density for each considered aggregate section. In order to validate numerical primary particle size, the comparison to experimental data is required. Due to its numerous advantages, the Time-Resolved Laser-Induced Incandescence (TiRe-LII) technique is a nowadays popular experimental method. However, the comparison of the numerically and the experimentally obtained primary particle size may be charged with uncertainties introduced by the additional measurements or assumptions of the numerous parameters required to derive primary particle size from the detected signal. In order to improve the validation strategy, an additional approach for primary particle size distribution validation with TiRe-LII is proposed. This is based on the reconstruction of the temporal evolution of incandescence from the numerical results and its comparison with the measured signal. The effectiveness of this ’forward’ method is demonstrated a priori by quantifying the errors potentially avoided by the new strategy. The validity of the proposed primary particle tracking model is tested by both the traditional ’inverse’ and the ’forward’ method on target flames of the International Sooting Flame (ISF) Workshop. In particular a laminar premixed ethylene flame is considered first. Then, two laminar coflow ethylene flames with different dilutions are put under the scope. The sensitivity to the model parameters, such as accounting for the surface rounding and the choice of smallest aggregating particle size, is explored in both the premixed flame and in the coflow flame with highest ethylene content. To understand the effect of the fuel stream dilution on the primary particle size in the coflow flame, first, the flame-flow interaction and the effect of the dilution on the flame structure is investigated. [...]
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Grady, Keith J. "Solar flare particle acceleration in collapsing magnetic traps." Thesis, University of St Andrews, 2012. http://hdl.handle.net/10023/2839.
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The topic of this thesis is a detailed investigation of different aspects of the particle acceleration mechanisms operating in Collapsing Magnetic Traps (CMTs), which have been suggested as one possible mechanism for particle acceleration during solar flares. The acceleration processes in CMTs are investigated using guiding centre test particle calculations. Results including terms of different orders in the guiding centre approximation are compared to help identify which of the terms are important for the acceleration of particles. For a basic 2D CMT model the effects of different initial conditions (position, kinetic energy and pitch angle) of particles are investigated in detail. The main result is that the particles that gain most energy are those with initial pitch angles close to 90° and start in weak field regions in the centre of the CMT. The dominant acceleration mechanism for these particles is betatron acceleration, but other particles also show signatures of Fermi acceleration. The basic CMT model is then extended by (a) including a magnetic field component in the invariant direction and (b) by making it asymmetric. It is found that the addition of a guide field does not change the characteristics of particle acceleration very much, but for the asymmetric models the associated energy gain is found to be much smaller than in symmetric models, because the particles can no longer remain very close to the trap centre throughout their orbit. The test particle method is then also applied to a CMT model from the literature which contains a magnetic X-line and open and closed field lines and the results are compared with the previous results and the findings in the literature. Finally, the theoretical framework of CMT models is extended to 2.5D models with shear flow and to fully 3D models, allowing the construction of more realistic CMT models in the future.
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Battaglia, Marina. "Particle kinematics in solar flares : observations and theory /." Göttingen Cuvillier, 2008. http://d-nb.info/992806011/04.
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Teleki, Alexandra. "Flame synthesis and coating of nanostructured particles in one step." kostenfrei, 2008. http://e-collection.ethbib.ethz.ch/view/eth:30778.
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Merlo, Nazim. "Caractérisation expérimentale d’une flamme turbulente non prémélangée swirlée : effet de l’enrichissement en oxygène." Thesis, Orléans, 2014. http://www.theses.fr/2014ORLE2058/document.
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Cette thèse est une contribution à l’étude des flammes de méthane turbulentes non prémélangées en rotation, dites swirlées, avec ou sans enrichissement en oxygène de l’oxydant. L’étude se focalise sur la stabilité de la flamme, les émissions polluantes et la dynamique du jet en non réactif et réactif. Notre dispositif expérimental se compose d’un brûleur à swirler coaxial avec injection radiale de méthane au voisinage de la sortie du brûleur. Ce dernier est confiné dans une chambre de combustion. La teneur en oxygène dans l’oxydant, le nombre de swirl géométrique et la richesse globale à l’injection sont les principaux paramètres qui peuvent être précisément contrôlés. La stabilité de la flamme est caractérisée par chimiluminescence OH*. Les émissions polluantes sont mesurées par des analyseurs en ligne via un prélèvement dans les gaz brûlés. La dynamique du jet est caractérisée principalement par PIV stéréoscopique dans un plan longitudinal et plusieurs plans transverses. La diffusion du méthane dans le jet swirlé est abordée qualitativement par fluorescence induite par laser de l’acétone dans un plan. À ce jour, peu de travaux portent sur la caractérisation notamment dynamique de ces flammes swirlées avec enrichissement en O2. La mise en rotation du jet est à l’origine d’une zone de recirculation centrale qui favorise la stabilisation de la flamme en régime pauvre et à grand nombre de Reynolds. L’étude des émissions polluantes montre que les régimes de combustion à l’air pour lesquels la flamme est liftée stable sont aussi ceux qui produisent du CO et du CH4 résiduel en des quantités non négligeables. L’enrichissement en oxygène permet alors de convertir les imbrûlés et ce pour de faibles enrichissements tout en améliorant la stabilité de flamme via une diminution de la hauteur d’accrochage et des fluctuations associées comme le confirment de précédentes études. L’augmentation des NOx par la voie thermique a été quantifiée pour des enrichissements en oxygène inférieurs à 30 % vol. L’étude systématique en non réactif et réactif apporte des détails sur la topologie tridimensionnelle du jet swirlé suivant les paramètres de l’étude. L’étude de la décroissance des vitesses et de la décroissance du nombre de swirl dans la direction de l’écoulement permetde mettre en évidence l’effet de la flamme sur le jet swirlé. Un couplage entre l’évolution du taux d’entraînement par la recirculation externe et les émissions polluantes est mis en évidence pour expliquer l’évolution des NOx suivant la richesse globale à l’injection. Nous avons proposé une modélisation des écoulements swirlés qui repose sur les écoulements à vorticité hélicoïdale afin d’identifier les caractéristiques principales des structures hélicoïdales au sein de l’écoulementThis thesis is a contribution to the study of turbulent non-premixed swirling methane flames with or without oxygen addition in the oxidizer. The study deals with the flame stability, the pollutant emissions and the jet dynamic behaviour in non-reacting and reacting conditions. The burner, operating in a combustion chamber, consists of two concentric tubes with a swirler placed in an annular arrangement, which supplied the oxidant flow (air or oxygen-enriched air). The central pipe delivers fuel (methane) radially just below the burner exit plane. The oxygen content in the oxidizer, the geometric swirl number and the global equivalence ratio are the main parameters, which can be precisely set. OH* chemiluminescence imaging is used to characterize flame stability. Multi-gas analyzers are used to measure pollutant emissions in the exhaust gas. The flow is characterized using stereoscopic PIV measurements in different longitudinal and transverse planes. A qualitative study dealing with the methane diffusion imaging is also conducted by use of acetone planar laser-induced fluorescence. Up to now only few studies have examined the dynamic behavior of this type of swirled flames with oxygen addition. Introducing swirl allows creating a central recirculation zone which favors lean flame stabilization at higher Reynolds numbers. The mapping of the combustion regimes combined with the pollutant emission results show that the stable lifted flames are related to high CO and residual CH4 emission levels in the exhaust gas. Oxygen addition, even by a few percent, allows improving CO and unburned hydrocarbons conversion and increasing flame stability at the same time via a decrease of liftoff heights and the related fluctuations. The NOx emissions increase via the thermal pathway with increasing the oxygen-enrichment rate up to 30 % vol. A comparative study in non-reacting and reacting conditions is conducted to give insight into the tridimensional flow field topology varying the above-mentioned parameters. Mean streamwise velocity and swirl number decay rates show the flame effects on the flow dynamics. A coupling mechanism between the entrainment rate of the surroundings via the external recirculation and the pollutant emissions is proposed to explain the NOx emission trend with the global equivalence ratio. A model is also proposed based on the helical vortices to identify the main features of helix structures in the jet in non-reacting and reacting conditions
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Roussillo, Mathieu. "Development of optical diagnostics for soot particles measurements and application to confined swirling premixed sooting flames under rich conditions." Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLC060/document.
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Le contrôle de la production des particules de suies est aujourd'hui un enjeu industriel majeur en raison de leur impact néfaste tant sur le climat que sur la santé humaine et de leur forte contribution aux transferts radiatifs. Pour mieux comprendre et contrôler la production de ces polluants dans les foyers industriels, il est primordial d’améliorer nos connaissances à ce sujet dans un brûleur turbulent. L’objectif de cette thèse est donc de mettre en place des diagnostics optiques pour l’étude des flammes suitées turbulentes et pour caractérise la production de suies dans une nouvelle configuration de combustion prémélangée,confinée, swirlée turbulente académique tout en se rapprochant des configurations industrielles. Une première configuration expérimentale laminaire est donc considérée afin de valider la mise en place de la technique d’Incandescence Induite par Laser (LII) pour mesurer la fraction volumique de suies fv. Il s’agit d’un brûleur conçu à l’université de Yale qui permet la stabilisation d’une flamme laminaire de diffusion éthylène/air. Ce brûleur a été largement étudié dans la littérature nous permettant ainsi de comparer nos mesures aux résultats de différentes équipes internationales. La calibration du signal LII avec la technique MAE (Modulated Absorption Emission) a été effectuée via une collaboration avec l’UPMC, permettant de mesurer quantitativement fv et de comparer les techniques MAE et LII. Le brûleur a ensuite été équipé d’un haut-parleur afin de moduler l’écoulement et de pouvoir étudier les effets d’une perturbation contrôlée sur la production de suies, se rapprochant ainsi des phénomènes instationnaires caractéristiques des écoulements turbulents. Enfin, les effets d’élargissement de la nappe laser sur les résultats de la LII sont examinés afin de pouvoir appliquer ce diagnostic optique dans une configuration turbulente innovante caractérisée par de grandes dimensions. Ce brûleur (EM2Soot) a été développé pour mesurer la production de suies dans une flamme turbulente swirlée riche confinée prémélangée. Il permet de quantifier indépendamment les effets de la richesse, de la puissance et de l’environnement thermique sur la production de suies. Un point de fonctionnement représentatif a alors été étudié et, en parallèle avec la LII, les techniques de vélocimétrie par images de particules (PIV), et de mesure de température des parois par phosphorescence induite par laser (LIP) ont été employées afin de caractériser l’effet de la turbulence sur la production des suies et d’établir une base de données pour la validation de futures simulations numériques. Enfin, la géométrie du brûleur a été modifiée permettant une stabilisation différente de la flamme (en forme d’un V). Un nouveau point de fonctionnement a alors été étudié afin de mettre en évidence le rôle de la géométrie de l’injecteur sur la stabilisation de la flamme et, par conséquent, la production totale de suiesThe control of soot particles production represents today a major industrial issue because of their harmful impact on both the climate and the human health and their strong contribution to the radiative transfers. To better understand and control the production of these polluting emissions, it is essential to improve our knowledge on this subject in a turbulent burner. The objective of this Ph.D. is to set up optical diagnostics for the study of turbulent flames and to experimentally characterize soot production in a new academic turbulent premixed combustion configuration while approaching industrial configurations, generally confined and swirled flows. For this, a laminar experimental configuration is first considered to validate the implementation of the Laser Induced Incandescence (LII) technique to measure the soot volume fraction fv. This burner designed at Yale University allows the stabilization of a laminar ethylene/air diffusion flame. This burner has been widely studied in the literature, so that it is possible to compare the quality of our measurements with the results of different international teams. Through collaborations with the UPMC, we calibrated the LII signal with the MAE (Modulated Absorption Emission) technique, making it possible to quantitatively measure fv and to compare the MAE and LII techniques. Finally, the burner was equipped with a loudspeaker to modulate the flow and to study the effects of a controlled perturbation on the soot production, thus approaching the unsteady phenomena characteristics of turbulent flows. Finally, the effects of the enlargement of the laser sheet on LII results were also investigated in order to be able to apply this diagnostic technique in an innovative large turbulent configuration. This experimental configuration, called EM2Soot, was developed to measure the production of soot in a turbulent swirled rich confined premixed ethylene/air flame. This burner makes it possible to independently quantify the effects of the equivalence ratio, the total flame power and the thermal environment on the total soot production. A representative operating point was then characterized, in parallel with LII measurements, Particle Image Velocimetry (PIV) and Laser Induced Phosphorescence (LIP) techniques have been employed in order to characterize the effect of the turbulence on soot production and to establish a database for the validation of future numerical simulations. Finally, the geometry of the burner has been modified allowing a different stabilization of the flame (V flame shape). A new operating point is then studied in order to highlight the role of the injector geometry on the stabilization of the flame and, consequently, on the total soot production
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Potier, Bruno. "Détermination des champs des températures et des concentrations dans une flamme de charbon pulvérisé de taille semi-industrielle : application au four pilote 1 mw du cerchar." Orléans, 1986. http://www.theses.fr/1986ORLE0012.
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Développement d'une méthode optique de mesure des températures, basée sur l'émission et l'absorption du rayonnement thermique dans le proche infrarouge, et permettant de déterminer la température en un point. Parallèlement aux champs des températures cette méthode permet d'accéder aux champs de concentrations relatives en particules et en dioxyde de carbone et fournir des renseignements sur les valeurs in situ de plusieurs paramètres nécessaires à la modélisation des transferts thermiques.
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Lecordier, Bertrand. "Etude de l'interaction de la propagation d'une flamme prémélangée avec le champ aérodynamique, par association de la tomographie laser et de la vélocimétrie par images de particules." Rouen, 1997. http://www.theses.fr/1997ROUES060.
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Ce travail expérimental a pour but de caractériser les interactions entre la propagation d'une flamme prémélangée propane-air avec un champ aérodynamique. Cette étude a été menée dans une chambre de combustion destinée à reproduire d'une façon simplifiée les conditions aérodynamiques rencontrées dans un moteur à allumage commandé. Les flammes sont allumées par une étincelle au centre de la chambre dans une turbulence en régime de décroissance. La première partie de ce travail a été consacrée au développement de la tomographie rapide et de la vélocimétrie par images de particules. L'association de ces deux diagnostics offre un accès simultané à l'évolution temporelle de la position des zones de réaction et des champs aérodynamiques dans les gaz frais au cours de la propagation des flammes. Une amélioration des mesures de vitesse a été développée en introduisant une approche originale de traitement des images de particules. Des validations de cette approche ont été réalisées à partir d'image de particules synthétiques. L'analyse et l'interprétation des résultats expérimentaux obtenus dans la chambre de combustion constituent la seconde partie de ce travail. Les propriétés aérodynamiques de l'écoulement à froid ont été caractérisées à partir de champs de vitesse instantanés mesurés à différents instants dans la décroissance de la turbulence. Le filtrage spatial des champs de vitesse a mis en évidence la difficulté de définir les propriétés de la turbulence dans les écoulements fortement instationnaires et le rôle prépondérant joué par les grosses structures de l'écoulement dans les phénomènes de dispersion cyclique des mesures de l'énergie de la turbulence. Dans la même chambre, une étude des flammes sphériques laminaires a permis de mesurer l'influence de l'étirement des zones de réaction sur les vitesses de combustion laminaire et d'en déduire des paramètres caractéristiques de ces interactions comme par exemple les longueurs de Markstein. Des mesures quantitatives des grandeurs caractéristiques des interactions entre la chimie et l'aérodynamique ont été obtenues pour la propagation de flammes turbulentes. Une analyse détaillée des propriétés géométriques des zones de réaction comme la courbure et le plissement et de leur évolution au cours de la propagation ont montré la persistance de larges structures sur les fronts de flamme. Enfin, des développements et des analyses spécifiques de la vélocimétrie par images de particules pour l'étude des flammes ont été proposés afin d'améliorer notre compréhension de l'influence de la propagation sur le champ aérodynamique devant la flamme.
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Gai, Guodong. "Modeling of water sprays effects on premixed hydrogen-air explosion, turbulence and shock waves Modeling pressure loads during a premixed hydrogen combustion in the presence of water spray Numerical study on laminar flame velocity of hydrogen-air combustion under water spray effects Modeling of particle cloud dispersion in compressible gas flows with shock waves A new formulation of a spray dispersion model for particle/droplet-laden flows subjected to shock waves Particles-induced turbulence: a critical review of physical concepts, numerical modelings and experimental investigation A new methodology for modeling turbulence induced 1 by a particle-laden flow using a mechanistic model." Thesis, Normandie, 2020. http://www.theses.fr/2020NORMIR14.
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Cette thèse de doctorat est dédiée au développement de modèles physiques pour l’étude des systèmes d’aspersion de gouttelettes d’eau en milieu réactif d’hydrogène-air pré-mélangée dans les centrales nucléaires. Des modèles d’ordre réduit sont développés pour décrire l’évaporation des gouttelettes d’eau dans la flamme, la dispersion des nuages de particules après le passage des ondes de choc et l’évolution de l’échelle caractéristiques de turbulence avec la présence d’un jet d’eau. Une nouvelle méthodologie est proposée pour évaluer les effets de l’évaporation par l’aspersion sur la propagation de la flamme d’hydrogène turbulente à l’intérieur d’un volume fermé et un modèle simple est développé pour la quantification de la décélération de la vitesse laminaire avec l’évaporation des gouttelettes à l’intérieur de la flamme. Également, un modèle analytique est proposé pour la prédiction de la dispersion de nuage de particule après le passage d’une onde de choc en s’appuyant sur le one-way formalisme avec une extension afin de prédire l’apparition d’un pic de densité du nombre de particules en utilisant le two-way formalisme. En ce qui concerne la modulation de la turbulence induite par les particules, un modèle simple est utilisé pour l’estimation des échelles intégrales de la turbulence induites par l’injection de nuage des particules. Ces modèles numériques développés peuvent être couplés pour être mis en œuvre dans les simulations numériques à grande échelle de l’effet du système d’aspersion sur les explosions accidentelles d’hydrogène dans les centrales nucléairesThis PhD dissertation is dedicated to develop simple models to investigate the effect of water spray system on the premixed hydrogen-air combustion in the nuclear power plants. Specific simple models are developed to describe the water droplet evaporation in the flame, particle cloud dispersion after the shock wave passage, and turbulence length scale evolution with the presence of a water spray. A methodology is proposed to evaluate the spray evaporation effects on the propagation of the turbulent hydrogen flame inside a closed volume and a simple model is developed for the quantification of the laminar velocity deceleration with the droplets evaporation inside the flame. An analytical model is proposed for the prediction of particle cloud dispersion after the shock passage in the one-way formalism and another analytical model is dedicated to describe the spray-shock interaction mechanism and predict the appearance of a particle number density peak using the two-way formalism. A review of the important criteria and physical modelings related to the particle-induced turbulence modulation is given and a mechanistic model is used for the estimation of the turbulent integral length scales induced by the injection of particle clouds. These developed numerical models can be coupled to implement in the large-scale numerical simulations of the spray system effects on the accidental hydrogen explosions in the nuclear power plants
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Chong, Kin Hung. "Modelling and simulation of particle formation in laminar flames." Thesis, University of Cambridge, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.336552.
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Mukundan, Mallika. "Phase control in the synthesis of yttrium oxide nano and micro-particles by flame spray pyrolysis." [College Station, Tex. : Texas A&M University, 2007. http://hdl.handle.net/1969.1/ETD-TAMU-1568.
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Hamilton, Brian. "Particle acceleration in dynamically reconnecting X-point solar-flare models." Thesis, University of Glasgow, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.425388.
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Kim, Kibum. "Interaction of iron species and soot particles in an isooctane diffusion flame." [Gainesville, Fla.] : University of Florida, 2006. http://purl.fcla.edu/fcla/etd/UFE0015080.
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Shum-Kivan, Francis. "Simulation des Grandes Echelles de flammes de spray et modélisation de la combustion non-prémélangée." Phd thesis, Toulouse, INPT, 2017. http://oatao.univ-toulouse.fr/18064/1/Shum_Kivan_Francis.pdf.
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La combustion d’hydrocarbures représente encore aujourd’hui une part très majoritaire de la production d’énergie dans le monde, et en particulier dans l’industrie aéronautique. La plupart des brûleurs industriels sont alimentés par un carburant sous forme liquide, injecté directement dans la chambre de combustion, générant ainsi de fortes interactions entre le spray, l’écoulement turbulent et la flamme. Dans le but d’acquérir une meilleure compréhension de la structure complexe des flammes de spray, une étude numérique a été réalisée sur la configuration du brûleur diphasique KIAI, caractérisée de façon précise et complète expérimentalement. Une approche de type simulation des grandes échelles a été utilisée pour simuler la phase gazeuse tandis que la phase liquide était résolue selon un formalisme Lagrangien déterministe (LES-DPS). L’analyse détaillée de la structure de flamme de spray permet de mettre en exergue le rôle important de la combustion non prémélangée dans ce type de flamme. Cela a motivé dans une seconde étape le développement d’une nouvelle approche pour modéliser les flammes de diffusion turbulentes. Le modèle présenté s’appuie sur la réponse des flammes de diffusion laminaires au maillage, à l’étirement et au plissement. Le dégagement de chaleur global de la flamme a été analysé dans des configurations de complexité croissante, et la capacité du modèle à le décrire a été évaluée.
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Yin, Chung-Yuan. "Soot particle size measurements in laminar premixed ethylene flames with laser-induced incandescence and scanning mobility particle sizer." Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2009. http://wwwlib.umi.com/cr/ucsd/fullcit?p1460029.
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Thesis (M.S.)--University of California, San Diego, 2009.Title from first page of PDF file (viewed January 9, 2009). Available via ProQuest Digital Dissertations. Includes bibliographical references (p. 46-48).
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Stanier, Adam. "Magnetic reconnection and particle acceleration in semi-collisional plasmas." Thesis, University of Manchester, 2013. https://www.research.manchester.ac.uk/portal/en/theses/magnetic-reconnection-and-particle-acceleration-in-semicollisional-plasmas(26c3b17d-87ca-4d98-b5b5-3a3d78e0dd03).html.
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Magnetic reconnection is an important mechanism for the restructuring of magnetic fields, and the conversion of magnetic energy into plasma heating and non-thermal particle kinetic energy in a wide range of laboratory and astrophysical plasmas. In this thesis, reconnection is studied in two semi-collisional plasma environments: flares in the solar corona, and the start-up phase of the Mega-Ampere Spherical Tokamak (MAST) magnetic confinement device. Numerical simulations are presented using two different plasma descriptions; the test-particle approach combined with analytical magnetohydrodynamic fields is used to model populations of high-energy particles, and a two-fluid approach is used to model the bulk properties of a semi-collisional plasma. With the first approach, a three-dimensional magnetic null-point is examined as a possible particle acceleration site in the solar corona. The efficiency of acceleration, both within the external drift region and in the resistive current sheet, is studied for electrons and protons using two reconnection models. Of the two models, it is found that the fan-reconnection scenario is the most efficient, and can accelerate bulk populations of protons due to fast and non-uniform electric drifts close to the fan current-sheet. Also, the increasing background field within the fan-current sheet is shown to stabilise particle orbits, so that the energy gain is not limited by ejection. With the second approach, the effects of two-fluid physics on merging flux-ropes is examined, finding fast two-fluid tearing-type instabilities when the strength of dissipation is weak. The model is then extended to the tight-aspect ratio toroidal-axisymmetric geometry of the MAST device, where the final state after merging is a MAST-like spherical tokamak with nested flux-surfaces and a monotonically increasing q-profile. It is also shown that the evolution of simulated 1D radial density profiles closely resembles the Thomson scattering electron density measurements in MAST. An intuitive explanation for the origin of the measured density structures is proposed, based upon the results of the toroidal Hall-MHD simulations.
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Xie, Yanxuan. "Study of Interaction of Entrained Coal Dust Particles in Lean Methane-Air Premixed Flames." Digital WPI, 2011. https://digitalcommons.wpi.edu/etd-theses/1065.
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"This study investigates the interaction of micron- sized coal particles entrained into lean methane €“ air premixed flames. In a typical axisymmetric burner, coal particles are made to naturally entrain into a stream of the premixed reactants using an orifice plate setup. Pittsburgh seam coal dust, with three particle sizes in the range of 0 to 25 µm, 53 to 63 µm, and 75 to 90 µm is used. The effects of different coal dust concentrations (10 €“ 300 g/m3) at three lean equivalence ratios, ϕ (methane-air) of 0.75, 0.80 and 0.85 on the laminar burning velocity are determined experimentally. The laminar burning velocity of the coal dust-methane-air mixture is determined by taking a shadowgraph of the resulting flame and using the cone-angle method. The results show that the addition of coal dust in methane-air premixed flame reduces the laminar burning velocity at particle size of 53 to 63 µm and 75 to 90 µm. However, burning velocity promotion is observed for 0 to 25 µm particles at ϕ = 0.80. Two competing effects are assumed involved in the process. The first is burning velocity promotion effect that the released volatile increases the gaseous mixture equivalence ratio and thus the burning velocity. The second is the heat sink effect of the coal particles to reduce the flame temperature and accordingly the burning velocity. A mathematical model is developed based on such assumption and it can successfully predict the change of laminar burning velocity at various dust concentration. Furthermore, the implication of this study to coal mine safety is discussed."
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Winter, Henry deGraffenried III. "Combining hydrodynamic modeling with nonthermal test particle tracking to improve flare simulations." Thesis, Montana State University, 2009. http://etd.lib.montana.edu/etd/2009/winter/WinterH0509.pdf.
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Solar flares remain a subject of intense study in the solar physics community. These huge releases of energy on the Sun have direct consequences for humans on Earth and in space. The processes that impart tremendous amounts of energy are not well understood. In order to test theoretical models of flare formation and evolution, state of the art, numerical codes must be created that can accurately simulate the wide range of electromagnetic radiation emitted by flares. A direct comparison of simulated radiation to increasingly detailed observations will allow scientists to test the validity of theoretical models. To accomplish this task, numerical codes were developed that can simulate both the thermal and nonthermal components of a flaring plasma, their interactions, and their emissions. The HYLOOP code combines a hydrodynamic equation solver with a nonthermal particle tracking code in order to simulate the thermal and nonthermal aspects of a flare. A solar flare was simulated using this new code with a static atmosphere and with a dynamic atmosphere, to illustrate the importance of considering hydrodynamic effects on nonthermal beam evolution. The importance of density gradients in the evolution of nonthermal electron beams was investigated by studying their effects in isolation. The importance of the initial pitch-angle cosine distribution to flare dynamics was investigated. Emission in XRT filters were calculated and analyzed to see if there were soft X-ray signatures that could give clues to the nonthermal particle distributions. Finally the HXR source motions that appeared in the simulations were compared to real observations of this phenomena.
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Lee, Minkyu. "Influence of the Reactant Temperature on Particle Entrained Laminar Methane-Air Premixed Flames." Digital WPI, 2014. https://digitalcommons.wpi.edu/etd-theses/623.
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This study investigates the laminar burning velocity of premixed methane-air mixtures, having controlled supply of micron-sized (75-90 ¥ìm) coal dust and sand particles over a range of gas phase equivalence ratios (0.9-1.2), dust concentrations (0-250 g/m3) and reactant temperatures (297, 350, 400 K) using a novel Bunsen-burner type experimental design. The experimental results show that, the laminar burning velocity is enhanced by the increase in the reactant temperature, irrespective of the equivalence ratio of the mixture due to enhanced reaction rates. Addition of coal particles in fuel lean (ϕ < 1) mixtures increases the laminar burning velocity initially up to a certain coal dust concentration, but after that, the trend is altered; either it remains constant or shows a decreasing trend. The dust concentration value, which produces the initial or local maximum, increases with increase in reactant temperature. In other words, the reactant temperature plays a significant role in the trend of increase in laminar burning velocity with dust addition. For ϕ > 1, at a given reactant temperature, a linear decay of burning velocity with dust addition is observed. When a combustible dust particle interacts with the flame zone, it extracts energy from the flame (heat sink effect) and releases volatiles, thereby changing the local equivalence ratio around the flame zone. Both, increase in the equivalence ratio and the heat sink effect, are influenced by the reactant temperature. A mathematical model including these effects is developed and the model predictions are compared with the experimental results. The results are in a good agreement for fuel lean and stoichiometric mixtures; whereas the model is found to under predict results for fuel rich cases, and needs further improvements.
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Karakaya, Yasin Hüseyin [Verfasser], and Tina [Akademischer Betreuer] Kasper. "Mass spectrometric gas phase diagnostics in particle forming flames / Yasin Karakaya ; Betreuer: Tina Kasper." Duisburg, 2021. http://d-nb.info/1237221439/34.
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Mihalik, Teresa Ann. "The quenching of gaseous hydrocarbon-air flames in packed beds of spherical particles /." Thesis, McGill University, 2000. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=33337.
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In the present work, the quenching of gaseous hydrocarbon-air flames in packed beds of spherical particles has been investigated experimentally. Experiments were carried out in the standard flammability apparatus of Coward and Jones modified by the insertion of a packed bed of solid monosize spheres in the flame tube. Laminar flames were spark-initiated in quiescent combustible mixtures and failure or successful transmission of the flames through the packed bed was determined by visual observation. The quenching limits were determined as a function of the packed bed parameters (i.e., sphere material, sphere size, length of packed bed, etc.) to elucidate the mechanisms of flame extinction in the bed of spherical particles. The results have direct application to the design of flame arrestors using a packed bed as the flame arresting element.The flame quenching limits are found to be relatively insensitive to the material of the solid spheres, but are dependent on the sphere size through a characteristic length scale that describes the open passages of the packed bed. Flame extinction was always observed to occur within a few millimeters of penetration into the packed bed section indicating that the length of the packed bed has little influence on the quenching of laminar flames. Analysis of the experimental results indicates that the mechanism for flame quenching in a packed bed is governed primarily by heat loss to the sphere surfaces by conduction, convection effects being negligible in the small channels of the packed bed. It is shown that, while conduction is the dominant flame quenching mechanism, selective diffusion and flame stretch also play an important role in the quenching process.
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Casey, Linda J. "Changes in wood-flake properties in relation to heat, moisture, and pressure during flakeboard manufacture." Thesis, Virginia Polytechnic Institute and State University, 1987. http://hdl.handle.net/10919/101369.
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In an attempt to relate different pressing parameters to changes in test flake properties, eight hot-press cycles were used in the manufacture of 24 flakeboard panels, with 2 levels each of platen temperature, initial mat moisture content, and press closing time. Temperature and gas pressure occurring at the face and core of the mat, along with platen pressure, were recorded throughout the press cycles. Data is presented graphically as a function of press time. Face and core equilibrium moisture content conditions throughout the press cycle were estimated for each panel based on corresponding temperature and gas pressure information. Time-integral data on temperature, gas pressure, and platen pressure were determined. Simple linear regressions were performed in an attempt to relate the actual test flake environment to changes in properties.
Two hundred and fifty yellow-poplar (Liriodendron tulipifera) test flakes were consolidated within the face and core of flakeboard mats and recovered. Their individual pre- and post-pressing thickness and specific dynamic bending modulus values were determined and compared with respect to changes in pressing parameters. Platen temperature, initial mat moisture content, and test flake location within the mat were all involved in significant two-way interactions in their effects on flake properties.M.S.
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Bansal, Nakul Raj. "Characterization of kinematic properties of turbulent non-premixed jet flames using high-speed Particle Image Velocimetry." The Ohio State University, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=osu1502968666691545.
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Labor, Serge. "Etude expérimentale d'une flamme de diffusion oxygène-hydrogène ensemencée en particules solides d'alumine." Ecully, Ecole centrale de Lyon, 2003. http://bibli.ec-lyon.fr/exl-doc/slabor.pdf.
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Le processus industriel auquel nous nous sommes intéressés permet, par le transit de particules d'alumine (AL203) dans une flamme, la génération de microsphères de saphir. La flamme de diffusion confinée O2/H2 est dirigée verticalement vers le bas et le jet central d'oxygène est ensemencé. Des études expérimentale (ADL, PIV) et numérique (N3S-Natur) ont été réalisées. (1) L'analyse du comportement a montré que la nature laminaire était conservée en écoulement réactif. Seuls les gradients de vitesse auxquels sont soumises les particules génèreront des collisions. (2) Deux trajectoires caractéristiques, possédant chacune un temps de passage différent dans la zone de haute température, ont été mises en évidence. (3) L'analyse des mesures PIV a permis de montrer que la densité des particules était inhomogène. (4) Contrairement à l'écoulement d'hydrogène, une variation de débit sur le jet central d'oxygène va causer une modification des vitesses de la flamme ainsi que de sa thermiqueMonocristalline sapphire microspheres are generated through the melting of alumine (AL203) particles in a flamme. The alumina particles are injected in a very peculiar 02/H2 confinened diffusion flame as it is a downwards vertical flame having fuel in periphery of a central powdered oxygen jet. Quantitative measurements were carried out (ADL, PIV) and supplemented by a numerical study (N3S-Natur). (1) The laminar behavior of the isothermal conditions is kept through reactive flow. Therefore, particles will mainly collide due to spedd gradients. (2) It has been shown that an axial particle will have a transit time int the high temperature zone very different to that of an off-line one. (3) The PIV date proved that the particle density was not homogeneous. (4) The hydrogen jet hardly influences the flame aerodynamic structure. Conversly, the central oxygen jet is at premium due to its effect on both the flame speed and temperature distribution
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Labor, Serge Escudié Dany. "Etude expérimentale d'une flamme de diffusion oxygène-hydrogène ensemencée en particules solides d'alumine." [S.l.] : [s.n.], 2003. http://bibli.ec-lyon.fr/exl-doc/slabor.pdf.
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Yao, Qifeng. "Experimental Investigation and Statistical Analysis of Entrainment Rates of Particles in Suspended Load." Kyoto University, 2019. http://hdl.handle.net/2433/244513.
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Escudero, Barros Felipe Andrés. "Experimental and numerical contributions to soot production in laminar axisymmetric diffusion flames." Thesis, Aix-Marseille, 2019. http://www.theses.fr/2019AIXM0048.
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Une étude expérimentale a été réalisée avec le but principal de caractériser la production de suie pour différents indices d’oxygène (OI) dans des flammes de diffusion normale (NDF) et inverse (IDF). Pour les IDFs, une augmentation de l’OI augmente la formation de suie mais n’affectent pas les processus d’oxydation, ce qui conduit à une augmentation de la fraction volumique de la suie et de la fraction rayonnée. Une analyse dimensionnelle basée sur le point de fumée (SP) a permis d’unifier les comportements pour les NDFs générées par la combustion de l’éthylène, du propane et du butane en termes de hauteur de flamme, de fraction volumique de suie et de fraction rayonnée au SP. Dans une deuxième étape, une étude numérique a été réalisée avec pour objectif principal d’évaluer les capacités de la méthode sectionnelle (SM) et trois méthodes des moments (MOM) à prédire la structure morphologique des particules de suie. A cette fin, les MOMs ont été implémentées dans un code` parallèle existant pour la simulation des flammes de diffusion laminaires axisymétriques. Les résultats ont montré que la SM est capable de reproduire les données expérimentales disponibles, tandis que les MOMs ne sont pas en mesure de prédire tous les détails de la morphologie des particules de suie avec le même niveau de précision. Une analyse des principales différences entre la SM et les MOM a été réalisée. La principale raison des différences observées entre les MOMs et la SM est liée à l’impossibilité des MOMs à satisfaire l’hypothèse de conservation du nombre densité de particules primaires et du nombre de particules primaires par agrégat pendant les processus de croissance surfacique de la suieAn experimental study was performed with the main objective of characterizing soot production for different oxygen indices (OIs) in normal (NDFs) and inverse (IDFs) diffusion flames. Specific absorption-emission based methods were developed, implemented and validated to measure soot volume fraction and temperature. It was found that for IDFs, an increase on the OI produces an enhancement of soot formation but does not affect oxidation processes, leading to an increase on soot volume fraction and radiant fraction. In addition, a scaling analysis based on the smoke point (SP) resulted on a unified behavior for ethylene, propane and butane fueled NDFs in terms of flame height, soot volume fraction and radiant fraction at SP. In a second step, a numerical study was performed with the main objective of evaluating the predictive capabilities of the sectional method (SM) and three methods of moments (MOMs) for the resolution of the population balance equation (PBE) for soot particle size distribution (PSD). For this purpose, the MOMs were added to an existing parallel code for simulating laminar axisymmetric diffusion flames. The SM was able to reproduce the available experimental data whereas the MOMs were not able to predict details of soot morphology with the same level of accuracy. An analysis on the main differences between the SM and MOMs was performed. The main issue identified for the MOMs was the inability to satisfy the assumption of conservation of number density of primary particles and number of primary particles per aggregate during soot surface processes
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石井, 大祐, Daisuke ISHII, 祐二 中村, Yuji NAKAMURA, 直樹 林, Naoki HAYASHI, 和弘 山本, Kazuhiro YAMAMOTO, 博史 山下, and Hiroshi YAMASHITA. "部分予混合化によるPAHs抑制メカニズムの検討." 日本機械学会, 2006. http://hdl.handle.net/2237/9368.
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Le, Dortz Romain. "Détermination des caractéristiques fondamentales de combustion de pré-mélange air-kérosène, de l’allumage à la vitesse de flamme : représentativité de surrogates mono et multi-composants." Thesis, Chasseneuil-du-Poitou, Ecole nationale supérieure de mécanique et d'aérotechnique, 2018. http://www.theses.fr/2018ESMA0008/document.
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Face à l’explosion du trafic aérien attendue ces prochaines années, l’impact de l’aviation civile sur l’environnement est un enjeu majeur. Les instances environnementales internationales comme l’ACARE (Conseil Consultatif pour la Recherche Aéronautique en Europe), en partenariat avec les grands groupes aéronautiques internationaux, ont fixé des objectifs drastiques pour préserver l’environnement : une réduction des émissions de CO2de 75 %et une réduction de 90 % des rejets d’oxydes d’azote dans l’atmosphère sont attendues d’ici 2050 par rapport aux avions fabriqués au début du 21èmesiècle. Les turbomachines actuelles possédant un degré de maturité très élevé ne permettront pas d’atteindre ces objectifs. Les motoristes cherchent donc à étudier de nouveaux concepts en rupture technologique pour les horizons 2050, comme les moteurs à détonation, ou encore les moteurs de type combustion à volume constant. Actuellement, les phénomènes physiques associés à la combustion du kérosène dans ce type de moteur sont encore mal documentés. L’objectif de cette thèse est donc de contribuer à l’amélioration de la connaissance et de la compréhension de ces phénomènes physiques.Au cours de cette étude, les flammes de pré-mélanges de kérosène et d’air sont étudiées expérimentalement grâce à des diagnostics optiques (strioscopie,PIV) et métrologiques. Le processus de combustion est notamment étudié dans des conditions thermodynamiques semblables à celles rencontrées dans un moteur aéronautique. La phase de propagation est dans un premier temps analysée dans des conditions laminaires et adiabatiques à travers la détermination de la vitesse fondamentale de flamme non-étirée, grandeur qui pilote le processus de combustion. Puis la sensibilité du front de flamme à l’étirement et la formation des instabilités de combustion sont dans un second temps examinées. Enfin, la phase d’allumage des pré-mélanges de kérosène et d’air dans des conditions aérodynamiques critiques est elle aussi traitée.Un second point abordé au cours de cette étude concerne la reproduction d’un kérosène réel par un substitut constitué d’un nombre d’espèces limité pour simplifier les problématiques industrielles et les études amont. En effet, la composition d’un kérosène commercial est complexe et variée et l’utilisation d’un représentant permet de modéliser numériquement le phénomène de combustion plus facilement. La pertinence de quelques surrogates plus ou moins représentatifs, formulés dans la littérature et élaborés au cours de différents travaux est notamment traitée dans cette étude en comparant les résultats obtenus avec ceux d’un kérosène commercial. De plus, la modélisation de ces kérosènes de substitution par un schéma cinétique valide estégalement analysée.Ce travail prend place dans le cadre de la chaire industrielle CAPA sur la combustion alternative pour la propulsion aérobie financée par SAFRANTech, MBDA et l’ANRWith air traffic expected to soar in the next few years, the impact of civil aviation on the environment is a major issue. International environmental organizations such as ACARE (the Advisory Council for Aeronautical Research and Innovation in Europe), in partnership with the main international aeronautical groups, have set drastic objectives to preserve the environment: a reduction of 75 % of CO2emissions and a reduction of 90 % of nitrogen oxide emissions into the atmosphere are sought by 2050, with reference to aircraft produced at the beginning of the 21st century. Current turboshaft engines have a very high degree of maturity and may not achieve these objectives. Engineers are therefore aiming to study new concepts that will become technological breakthroughs at the 2050 horizon, such as detonation engines or constant volume combustion engines. Currently, the physical phenomena associated with the combustion of kerosene in those kinds of engines are still poorly documented. The objective of this PhD thesis is to contribute to the improvement of the knowledge and understanding of these physical phenomena. In this work, premixed flames of kerosene and air are experimentally studied with optical diagnostics (Schlieren, PIV) and metrology techniques. The combustion process is here studied in thermodynamic conditions similar to those encountered in an aeronautical engine. First, the propagation phaseis analyzed in laminar and adiabatic conditions through the determination of the unstretched laminar burning velocity, which drives the combustion process. Then, in a second stage, the sensitivity of the flame front to stretch and the formation of combustion instabilities are examined. Finally, the ignition phase of premixed flames of kerosene and air under critical aerodynamic conditions is also investigated. A second issue tackled in this work is the reproduction of a real kerosene by a surrogate made up of a limited number of species, to simplify industrial problems and initial studies. Indeed, the composition of a commercial kerosene is complex and can vary, and the use of a surrogate allows an easier numerical simulation of the combustion process. The relevance of some more or less representative surrogates, formulated in the literature and elaborated all through different studies, is also studied in this thesis, by comparing the results obtained with those of a commercial kerosene. In addition, the modelling of those surrogates by a valid chemical kinetic mechanism is also analyzed. This research was conducted within the CAPA industrial Chair project dedicated to innovative combustion modes for air-breathing propulsion, financially supported by SAFRAN Tech, MBDA and France’s ANR national research agency
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Verdier, Antoine. "Experimental study of dilute spray combustion." Thesis, Normandie, 2017. http://www.theses.fr/2017NORMIR27/document.
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La combustion diphasique implique de nombreux phénomènes physiques complexes, comprenant l'atomisation, la dispersion, l'évaporation et la combustion. Bien que la simulation numérique soit un outil performant pour aborder ces différentes interactions entre les phases liquides et gazeuses, la méthode doit être validée par des études expérimentales fiables. Par conséquent, des données expérimentales précises sur la structure de la flamme et sur les propriétés de la phase liquide et gazeuse le long des étapes d'évaporation et de combustion sont nécessaires. La complexité des configurations aéronautiques réelles implique d'étudier l'effet des propriétés locales sur la dynamique des flammes pour une configuration canonique. Ce travail, réalisé dans le cadre du projet ANR TIMBER, a pour objectif d'améliorer la compréhension de la combustion en flux diphasique, ainsi que de produire une base de données efficace et originale pour la validation des modèles utilisés dans les LESLiquid fuels are the primary energy source in a wide range of applications including industrial and residential furnaces, internal combustion engines and propulsion systems. Pollutant emission reduction is currently one of the major constraints for the design of the next generation combustion chamber. Spray combustion involves many complex physical phenomena including atomization, dispersion, evaporation and combustion, which generally take place simultaneously or within very small regions in the combustion chambers. Although numerical simulation is a valuable tool to tackle these different interactions between liquid and gas phases, the method needs to be validated through reliable experimental studies. Therefore, accurate experimental data on flame structure and on liquid and gas properties along the evaporation and combustion steps are needed and are still challenging. A joint effort between numerical and experimental teams is necessary to meet tomorrow's energy challenges and opportunities. The complexity of the real aeronautical configurations implies to study the effect of local properties in flame dynamics on a canonical configuration, which presents the essential feature of very well defined boundary conditions. This work, carried out within the framework of the ANR TIMBER project, aims to improve the understanding of two-phase flow combustion, as well as to produce an efficient and original database for the validation of the models used in LES
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Ulianova, V. O., A. T. Orlov, and O. V. Bogdan. "Formation of ZnO Nanostructured Thin Film by Hydrothermal Method." Thesis, Sumy State University, 2013. http://essuir.sumdu.edu.ua/handle/123456789/35191.
Full textAbstract:
Formation of zinc oxide nanostructured thin films at different temperatures on Al-coated silicon and
lithium niobate substrates by hydrothermal method was presented. The comparison of morphology of
nanostructured thin films formed by hydrothermal and electrodeposition method was carried out. The opportunity
to use the hydrothermal method instead electrodeposition to obtain nanostructured films on a
conductive layer was shown. The dependence of morphology and crystallinity from growth temperature
was established using scanning electron microscopy and X-ray diffractometry. The application of synthesized
films as sensing layer of acoustic wave based and electrochemical sensors could enhance its sensitivity
to pollutants in gas or liquid phases by an active area increasing.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/35191