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Abbas, Fakhar. "Numerical Studies of Spray Atomization for Multiphase Flows". Thesis, The University of Sydney, 2022. https://hdl.handle.net/2123/29953.
Pełny tekst źródłaKhuong, Anh Dung. "The Eulerian-Lagrangian Spray Atomization (ELSA) Model of the Jet Atomization in CFD Simulations: Evaluation and Validation". Doctoral thesis, Universitat Politècnica de València, 2012. http://hdl.handle.net/10251/17237.
Pełny tekst źródłaKhuong ., AD. (2012). The Eulerian-Lagrangian Spray Atomization (ELSA) Model of the Jet Atomization in CFD Simulations: Evaluation and Validation [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/17237
Palancia
Aftel, Robert. "Effect of atomization gas properties on droplet atomization in an "air-assist" atomizer". Master's thesis, Virginia Tech, 1996. http://hdl.handle.net/10919/32599.
Pełny tekst źródłaAir, nitrogen, argon and carbon dioxide were used as the atomizing gas in an 'air-assist' spray nozzle to determine the effect of these gases on mean droplet size, number density, velocity and their distributions in kerosene fuel spays and spray flames using a two dimensional phase Doppler interferometer. Data have been obtained with these atomizing gases using a base, air assisted case as a reference, since this is the most commonly used atomizing fluid in almost all applications. Comparisons were made between the gases on a mass and momentum flux basis. Both burning and nonburning sprays were investigated. The results show significant differences in atomization characteristics from the atomizer with different gases and under conditions of constant mass and momentum flux of the gas. The results also show that the presence of oxygen in the air atomized sprays assists in the combustion process, since it produces smaller and faster moving droplets, especially at locations near to the nozzle exit. In nonburning sprays, droplets had similar size and velocity. Lighter gases such as nitrogen more effectively atomized the fuel in comparison to the denser gases. Argon and carbon dioxide produced larger, slower moving droplets than air and nitrogen assisted cases in both the burning and nonburning sprays. Flame photographs revealed the argon and carbon dioxide atomized flames to have greater luminosity than air or nitrogen atomized flames.
Master of Science
Singh, Gajendra. "Atomization and Combustion Characterization of Sprays". Thesis, University of Sydney, 2020. https://hdl.handle.net/2123/23135.
Pełny tekst źródłaBURROUGHS, ERIC WILLIAM. "DEVELOPMENT OF A HIGH-RESOLUTION MECHANICAL SPRAY PATTERNATOR FOR THE CHARACTERIZATION OF FUEL SPRAYS". University of Cincinnati / OhioLINK, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1132346171.
Pełny tekst źródłaValencia, Bejarano Maritza. "Experimental investigation of droplet coalescence in a poly-disperse full-cone spray". Thesis, The University of Sydney, 2003. https://hdl.handle.net/2123/27907.
Pełny tekst źródłaDowner, Roger Anthony. "The impact of spray modifiers on pesticide dose transfer". Thesis, University of Portsmouth, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.327001.
Pełny tekst źródłaFLOHRE, NICHOLAS MATTHEW. "EXPERIMENTAL INVESTIGATION OF SPRAY ATOMIZATION PROPERTIES OF AN AIRCRAFT ENGINE SWIRL CUP". University of Cincinnati / OhioLINK, 2003. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1054322000.
Pełny tekst źródłaPandal, Blanco Adrián. "Implementation and Development of an Eulerian Spray Model for CFD simulations of diesel Sprays". Doctoral thesis, Universitat Politècnica de València, 2016. http://hdl.handle.net/10251/68490.
Pełny tekst źródła[ES] El objetivo principal de este trabajo es el modelado de chorros diésel en condiciones de motor, incluyendo los fenómenos de atomización, transporte y evaporación fundamentales en la formación y desarrollo del chorro. Para este fin, se implementa un modelo de spray euleriano de tipo monofluido en un entorno RANS en la plataforma CFD OpenFOAM. El enfoque de modelado aplicado aquí sigue la idea de un modelo del tipo ⅀-Y. El modelo se fundamenta en la hipótesis de separación de escalas del flujo. En los sistemas de inyección actuales, es posible asumir que el flujo que sale de la tobera opera a altos números de Reynolds y Webber y por tanto, es posible considerar la independencia de fenómenos como el transporte de masa (grandes escalas del flujo) de los procesos de atomización que ocurren a escalas menores. La mezcla líquido/gas se trata como un pseudo-fluido con densidad variable y que fluye según un único campo de velocidad. Además, la geometría promedio de las estructuras de líquido se puede caracterizar mediante el modelado de la superficie de la interfase líquido/gas por unidad de volumen. Completando el modelo de chorro, se ha desarrollado un modelo de evaporación alrededor de las características particulares de las tecnologías actuales de los motores. Esto supone que el proceso de evaporación está controlado por mezcla aire-combustible y las gotas de combustible se evaporan siempre que exista suficiente aire para calentarlas y evaporarlas. Debido a esto, el modelo de evaporación implementado está basado en el enfoque de Flujos Localmente Homogéneos (LHF). Considerando una mezcla adiabática, en la región líquido/vapor, se supone que el chorro tiende a las condiciones adiabáticas de saturación y para determinar este equilibrio entre fases, se utiliza la ley ideal de Raoult. Finalmente, el modelo de chorro se acopla con un modelo avanzado de combustión basado en llamas de difusión aproximadas (ADF), que reduce el coste computacional especialmente para combustibles complejos y supone el paso lógico en el desarrollo del modelo para simular chorros diesel. En primer lugar, el modelo se aplica al cálculo de un caso básico de flujo externo no evaporativo, muy adecuado tanto por la extensa base de datos experimentales disponible como por la simetría geométrica que presenta, permitiendo una importante simplificación de la simulación. Los resultados obtenidos presentan un buen acuerdo con los experimentos, lo cual estimula su aplicación en configuraciones más complejas. En segundo lugar, el modelo se aplica al cálculo del "Spray A" del Engine Combustion Network (ECN), no evaporativo, para reproducir la estructura interna del chorro diesel así como predecir tamaños de gota (SMD) de forma precisa. Finalmente, se realizan estudios evaporativos del "Spray A" junto con la condición nominal reactiva de esta base de datos. La penetración de vapor, la longitud líquida, velocidad, el tiempo de retraso y la longitud de despegue de llama calculados se comparan con los datos experimentales y se analizan en detalle.
[CAT] L'objectiu principal d'aquest treball és el modelatge de dolls dièsel en condicions de motor, incloent els fenòmens d'atomització, transport i evaporació fonamentals en la formació i desenvolupament del doll. Amb aquesta finalitat, s'implementa un model de doll eulerià de tipus monofluid en un entorn RANS a la plataforma CFD OpenFOAM. L'enfocament de modelatge aplicat ací segueix la idea d'un model del tipus ⅀-Y. El model es fonamenta en la hipòtesi de separació d'escales del flux. En els sistemes d'injecció actuals, és possible assumir que el flux que surt de la tovera opera a alts nombres de Reynolds i Webber, i per tant és possible considerar la independència de fenòmens com el transport de massa (grans escales del flux) dels processos d'atomització que ocorren a escales menors. La mescla líquid / gas es tracta com un pseudo-fluid amb densitat variable i que flueix segons un únic camp de velocitat. A més, la geometria mitjana de les estructures de líquid es pot caracteritzar mitjançant el modelatge de la superfície de la interfase líquid / gas per unitat de volum. Completant el model, s'ha desenvolupat un model d'evaporació al voltant de les característiques particulars de les tecnologies actuals dels motors. Això suposa que el procés d'evaporació està controlat per la mescla aire-combustible i les gotes de combustible s'evaporen sempre que hi hagi suficient aire per escalfar i evaporar. A causa d'això, el model d'evaporació implementat està basat en el plantejament de fluxos Localment Homogenis (LHF). Considerant una mescla adiabàtica, a la regió líquid / vapor, se suposa que el doll tendeix a les condicions adiabàtiques de saturació i per determinar aquest equilibri entre fases, s'utilitza la llei ideal de Raoult. Finalment, el model de doll s'acobla amb un model avançat de combustió basat en flamelets de difusió aproximades (ADF), que redueix el cost computacional especialment per a combustibles complexos i suposa el pas lògic en el desenvolupament del model per simular dolls dièsel. En primer lloc, el model s'aplica al càlcul d'un cas bàsic de flux extern no evaporatiu, molt adequat tant per l'extensa base de dades experimentals disponible com per la simetria geomètrica que presenta, permetent una important simplificació de la simulació. Els resultats obtinguts presenten un bon acord amb els experiments, la qual cosa estimula la seva aplicació en configuracions més complexes. En segon lloc, el model s'aplica al càlcul del "Spray A" no evaporatiu de la xarxa Engine Combustion Network (ECN), per reproduir l'estructura interna del doll dièsel així com predir mides de gota (SMD) de forma precisa. Finalment, es realitzen estudis evaporatius del "Spray A" juntament amb la condició nominal reactiva d'aquesta base de dades. La penetració de vapor, la longitud líquida, velocitat, el temps de retard i la longitud d'enlairament de flama calculats es comparen amb les dades experimentals i s'analitzen en detall.
Pandal Blanco, A. (2016). Implementation and Development of an Eulerian Spray Model for CFD simulations of diesel Sprays [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/68490
TESIS
Strasser, Wayne Scott. "Seeking Understanding of Acoustics and Spray Character in a Three-Stream Pulsating Transonic Airblast Injector". Diss., Virginia Tech, 2015. http://hdl.handle.net/10919/77428.
Pełny tekst źródłaPh. D.
Sescu, Carmen. "Experimental and Computational Study on Liquid Atomization by Slinger Injector". University of Toledo / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1310163402.
Pełny tekst źródłaCrialesi, Esposito Marco. "Analysis of primary atomization in sprays using Direct Numerical Simulation". Doctoral thesis, Universitat Politècnica de València, 2019. http://hdl.handle.net/10251/133975.
Pełny tekst źródła[CAT] La comprensió dels fenòmens físics que succeïxen en la regió densa (també coneguda com a camp pròxim) durant l'atomització dels sprays ha sigut una de les majors incògnites a l'hora d'estudiar les seues aplicacions. En el sector industrial, el rang d'interés comprén des de toveres en aplicacions propulsives a sprays en aplicacions mèdiques, agrícoles o culinàries. Esta evident falta de coneixement obliga a realitzar simplificacions en la modelització, provocant resultats poc precisos i la necessitat de grans caracteritzacions experimentals en la fase de disseny. D'esta manera, els processos de ruptura del spray i atomització primària es consideren problemes físics fonamentals, la complexitat dels quals ve donada com resultat d'un flux multifàsic en un règim altament turbulent, originant escenaris caòtics. L'anàlisi d'este problema és extremadament complex a causa de l'absència substancial de teories validades dels fenòmens físics involucrats com són la turbulència i l'atomització. A més, la combinació de la naturalesa multifàsica del flux i el seu comportament turbulent resulten en una gran dificultat per a afrontar el problema. Durant els últims 10 anys les tècniques experimentals han sigut finalment capaces de visualitzar la regió densa, però la confiança, anàlisi i efectivitat dels experiments en esta regió del spray encara requerix de millores substancials. En este context, esta tesi tracta de contribuir en l'enteniment d'estos processos físics i de proporcionar ferramentes d'anàlisi per a estos fluxos tan complexos. Per a això, per mitjà de Direct Numerical Simulations s'ha afrontat el problema resolent les escales de moviment més menudes, al mateix temps que es capturen totes les escales de turbulència i esdeveniments de ruptura. Un dels objectius de la tesi ha sigut avaluar la influència que les condicions de contorn del flux entrant tenen en l'atomització primària i en el comportament turbulent del spray. Per a això, s'han empleat dos condicions de contorn diferents. En primer lloc s'ha empleat una condició de contorn sintètica per a produir turbulència homogènia a l'entrada, simulant el comportament de la tovera. Una de les característiques més interessants d'este mètod és la possibilitat de retocar els paràmetres dins de l'algoritme. En particular, l'escala de longitud integral s'ha variat per a avaluar la influència de les estructures mes grans de la tovera en l'atomització primària. L'anàlisi de la condició de contorn sintètica també ha permés el disseny òptim de simulacions de les quals s'han derivat estadístiques turbulentes significatives. En este escenari, s'han dut a terme estudis més profunds sobre la influència de propietats de les estructures turbulentes com l'homogeneïtat i l'anisotropia tant en l'espectre dels fluxos com en les estadístiques de les gotes. Per a tal fi, s'han desenrotllat metodologies noves per a computar l'anàlisi espectral i l'estadística de les gotes. Entre els resultats d'esta anàlisi destaca la independència de la condició de contorn d'entrada en les estadístiques de les gotes, mentres que d'altra banda, es recalca que les característiques turbulentes desenrotllades en l'interior de la tovera afecten a la quantitat total de massa atomitzada. Estes consideracions es troben recolzades per l'anàlisi espectral realitzat, per mitjà del qual es conclou que la turbulència multifásica compartix el comportament universal descrit per les teories de Kolmogorov.
[EN] The understanding of the physical phenomena occurring in the dense region (also known as near field) of atomizing sprays has been long seen as one of the biggest unknown when studying sprays applications. The industrial range of interest goes from nozzles in combustion and propulsion applications to medical sprays, agricultural and food process applications. This substantial lack of knowledge is responsible for some important simplification in modeling, that often result to be inaccurate or simply partial, leading to the evident need of large experimental characterization during the design phase. In fact, the spray breakup and primary atomization processes are indeed fundamental problems of physics, which complexity results from the combination of a multiphase flow in a highly turbulent regime that leads to chaotic scenarios. The analysis of this problem is extremely problematic, due to a substantial lack of definitive theories about the physical phenomena involved, namely turbulence and atomization. Furthermore, the combination of the multiphase nature of the flow and its turbulent behavior makes substantially difficult to address the problem. Only within the last 10 years, experimental techniques have been capable of visualizing the dense region, but the experiments reliability, analysis and effectiveness in this region still requires vast improvements. In this scenario, this thesis aims to contribute in the understanding of these physical process and to provide analysis tools for these complex flows. In order to do so, Direct Numerical Simulations have been used for addressing the problem at its smallest scale of motion, while reliably capturing all turbulence scales and breakup events. The multiphase nature of the flow is accounted for by using the Volume of Fluid method. One of the goal of the thesis was to assess the influence of the inflow boundary conditions on the primary atomization and on the spray's turbulence behavior. In order to do so, two different boundary conditions were used. In a first place, a synthetic inflow boundary condition was used in order to produce a homogeneous turbulence inflow, simulating the nozzle behavior. One of the interesting features of this method was the possibility of tweaking the parameters within the algorithm. In particular, the integral length scale was varied in order to assess the influence of nozzle larger turbulent structures on the primary atomization. The analysis on the synthetic boundary condition also allowed to optimally design simulations from which derive meaningful turbulence statistics. On this framework, further studies were carried over on the influence of turbulent structures properties, namely homogeneity and anisotropy, on both the flows spectra and droplets statistics. In order to achieve this goal, novel procedures for both computing the flow spectra and analyzing droplets were developed and are carefully addressed in the thesis. The results of the analysis highlight the independence of droplets statistics from the inflow boundary condition, while, on the other hand, remarking how the total quantity of atomized mass is significantly affected by the turbulence features developed within the nozzle. This considerations are supported by the spectrum analysis performed, which also highlighted how multiphase turbulence shares the universal features described in Kolmogorov theories.
Crialesi Esposito, M. (2019). Analysis of primary atomization in sprays using Direct Numerical Simulation [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/133975
TESIS
Fakhri, Syed Abdul Khader Yetter Richard A. Lee Jongguen. "A study on the atomization and spray characteristics of gelled simulants formed by two impinging jets". [University Park, Pa.] : Pennsylvania State University, 2009. http://etda.libraries.psu.edu/theses/approved/WorldWideIndex/ETD-4887/index.html.
Pełny tekst źródłaMandumpala, devassy Bejoy. "Atomization modeling of liquid jets using an Eulerian-Eulerian model and a surface density approach". Thesis, Aix-Marseille, 2013. http://www.theses.fr/2013AIXM4701/document.
Pełny tekst źródłaIn internal combustion engines, the liquid fuel injection is an essential step for the air/fuel mixture preparation and the combustion process. Indeed, the structure of the liquid jet coming out from the injector plays a key role in the proper mixing of the fuel with the gas in the combustion chamber. The present work focuses on the liquid jet atomization phenomena under Diesel engine conditions. Under these conditions, liquid jet morphology includes a separate liquid phase (i.e. a liquid core) and a dispersed liquid phase (i.e. a spray). This manuscript describes the development stages of a new atomization model, for a high speed liquid jet, based on an eulerian two-phase approach. The atomization phenomenon is modeled by defining different surface density equations, for the liquid core and the spray droplets. This new model has been coupled with a turbulent two-phase system of equations of Baer-Nunziato type. The process of ligament breakup and its subsequent breakup into droplets are handled with respect to available experiments and high fidelity numerical simulations. In the dense region of the liquid jet, the atomization is modeled as a dispersion process due to the turbulent stretching of the interface, from the side of liquid in addition to the gas side. Different academic test cases have been performed in order to verify the numerical implementation of the model in the IFP-C3D software. Finally, the model is validated with the recently published DNS results under typical conditions of direct injection Diesel engines
English, Craig Alan. "Development and Characterization of a Synchronously Actuated Response Atomizer for Studying Thermoacoustic Instabilities". Thesis, Virginia Tech, 2012. http://hdl.handle.net/10919/42378.
Pełny tekst źródłaMaster of Science
Yildiz, Dilek. "Experimental Investigation of superheated liquid jet atomization due to flashing phenomena". Doctoral thesis, Universite Libre de Bruxelles, 2005. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/211018.
Pełny tekst źródłaLiquid flashing phenomena holds an interest in many areas of science and engineering. Typical examples one can mention: a) the accidental release of flammable and toxic pressure-liquefied gases in chemical and nuclear industry; the failure of a vessel or pipe in the form of a small hole results in the formation of a two-phase jet containing a mixture of liquid droplets and vapor, b) atomisation improvement in the fuel injector technology, c) flashing mechanism occurrence in expansion devices of refrigerator cycles etc. The interest in flashing events is especially true in the safety field where any unexpected event is undesirable. In case of an accident, flammable or toxic gas clouds are anticipated in close regions of the release because of the sudden phase change .Due to the non-equilibrium nature of the flow in these near field regions, conducting accurate data measurements for droplet size and velocity is a challenging task resulting in scarce data in the very close area.
This research has been carried out at the von Karman Institute (VKI) within the 5th framework of European Commission to fulfill the goal of understanding of source processes in flashing liquids in accidental releases. The program is carried out under name of FLIE (Flashing Liquids in Industrial Environments)(Contract no: EVG1-CT-2000-00025). The specific issues that are presented in this thesis study are the following:a) a comprehensive state of art of the jet break up patterns, spray characteristics and studies related to flashing phenomena; b)flashing jet breakup patterns and accurate characterization of the atomized jet such as droplet diameter size, velocity and temperature evolution through carefully designed laboratory-scale experiments; c) the influence of the initial storage conditions on the final atomized jet; d) a physical model on the droplet transformation and rapid evaporation in aerosol jets.
In order to characterize the atomization of the superheated liquid jet, laser-based optical techniques like Particle Image Velocimetry (PIV), Phase Doppler Anemometry (PDA) are used to obtain information for particle diameter and velocity evolution at various axial and radial distances. Moreover, a high-speed video photography presents the possibility to understand the break-up pattern changes of the simulating liquid namely R-134A jet in function of driving pressure, superheat and discharge nozzle characteristics. Global temperature measurements with an intrusive technique such as thermocouples, non-intrusive measurements with Infrared Thermography are performed. Cases for different initial pressures, temperatures, orifice diameters and length-to-diameter ratios are studied. The break-up patterns, the evolution of the mean droplet size, velocity, RMS, turbulence
intensity and temperature along the radial and axial directions are presented in function of initial parameters. Highly populated drop size and velocity count distributions are provided. Among the initial storage conditions, superheat effect is found to be very important in providing small droplets. A 1-D analytical rapid evaporation model is developed in order to explain the strong temperature decrease during the measurements. A sensitivity analysis of this model is provided.
Doctorat en sciences appliquées
info:eu-repo/semantics/nonPublished
Vonhoff, Sebastian. "The influence of atomization conditions on protein secondary and tertiary structure during microparticle formation by spray-freeze-drying". kostenfrei, 2010. http://d-nb.info/1002481872/34.
Pełny tekst źródłaTambe, Samir B. "Liquid Jets in Subsonic Crossflow". University of Cincinnati / OhioLINK, 2004. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1100876702.
Pełny tekst źródłaVerones, Daniel Antonio Garbim. "Desenvolvimento de micropartículas gastro-resistentes contendo azitromicina por spray-drying". Universidade de São Paulo, 2010. http://www.teses.usp.br/teses/disponiveis/60/60137/tde-17112010-232035/.
Pełny tekst źródłaThe azithromycin is an antibiotic of the macrolide class used in cutaneous and respiratory infections treatments. Its pharmacokinetics properties confer a large cell distribution and accumulation in tissues. Due to its small bioavailability (37%) and acid pH instability, alternatives to the development of gastric-resistance microparticles to be uses in different pharmaceuticals forms were investigated. Azithromycin microparticles were obtained through spray-drying technique with the pH-dependent polymer Eudragit® L30-D55 and triethyl citrate as plasticizer. The experimental development followed a factorial planning Box-Behnken with four factors in three levels. The microparticles were characterized by bulk density, tapped density, Hausner ratio, Carr index, repose angle and HPLC. The drying process was evaluated by azithromycin yield and recover. From the microparticles physics parameters and the process yield, three samples were chosen to be better evaluated. The samples contained 15, 30 and 45% of coat polymer over azithromycin dehydrate. They were evaluated by X-ray powder diffraction (XRPD), calorimetry, infrared, surface electronic microscopy (SEM) and dissolution assay. The factors that most affected the drying process and the microparticles development were Eudragit® L30D-55 concentration and drying air temperature, and lower was the polymer amount and higher was the drying air temperature, better was the process yield. The azithromycin recover for all microparticles were superior to 80%. The microparticles presented low bulk density, but good flow properties for the great part of the samples. The calorimetry and the XRPD evaluations suggest that azithromycin is encapsulated, what can be confirmed through SEM pictures, which showed uniform and spherical structures. The microparticles with higher polymers concentrations showed the best characteristics with gastric protection above 50% and they are promising candidates to the development of oral solid pharmaceutical forms containing gastro-resistant azithromycin.
Patel, Nayan V. "Simulation of Hydrodynamic Fragmentation from a Fundamental and an Engineering Perspective". Diss., Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/16225.
Pełny tekst źródłaMedeiros, Adja Cristina Lira de. "Iogurte caprino probiótico em pó: estudo do processo de secagem, da caracterização do pó e da viabilidade do probiótico". Universidade de São Paulo, 2013. http://www.teses.usp.br/teses/disponiveis/74/74132/tde-22052013-102129/.
Pełny tekst źródłaThe aim of this study was to develop yogurts with the traditional culture and Bifidobacterium animalis subsp. lactis probiotic culture, dehydrate products in spray drying using maltodextrin as a carrier and characterize the powders, as well as determining the resistance of probiotics to atomization process. The present study evaluated three different inlet air temperatures of spray dryer (130, 150 and 170°C) in yoghurts with two different maltodextrin concentrations (10 and 20%), totaling six treatments: T1 (10%malto/130°C), T2 (20%malto/130°C), T3 (10%malto/150°C), T4 (20%malto/150°C), T5 (10%malto/170°C) e T6 (20%malto/170°C). The yogurt drying was performed in a pilot spray dryer and the viable cells of Bifidobacterium animalis subsp. lactis enumeration was performed by pour plate. The powders showed low levels of humidity and high hygroscopicity. The water activity (Aw) of the powders ranged from 0.09 to 0.19 and increased after 30 days of storage, showing the hygroscopic powders character. It was found that after yogurt dehydration, despite their counts were less than integral products, still had counts above 106 CFU/g, therefore were still within regulation limits for a product to be considered as probiotic. The treatments that have undergone higher temperatures during the drying process (T5 and T6) were those who had higher losses of probiotic microorganisms, suggesting that high temperatures had a strong influence on the viability of probiotics. The T1 (130°C/10%) obtained higher counts of the microorganism analyzed, with counts above 106 CFU/g, during 60 days of storage, indicating that is the best treatment among those studied in relation to obtaining a goat probiotic yoghurt powder with longer shelf life. In general, it is concluded that the atomization process allows the obtention of stable goat milk yogurt powder, in a microbiological point of view. Furthermore, it was obtained a product that can be an alternative for increasing the consumption of goat milk as well as probiotics.
Opfer, Lars [Verfasser], Cameron [Akademischer Betreuer] Tropea, Günter [Akademischer Betreuer] Brenn i Ilia [Akademischer Betreuer] Roisman. "Controlling Liquid Atomization using Dilute Emulsions: Mitigation of Pesticide Spray Drift / Lars Opfer. Betreuer: Cameron Tropea ; Günter Brenn ; Ilia Roisman". Darmstadt : Universitäts- und Landesbibliothek Darmstadt, 2014. http://d-nb.info/1110902123/34.
Pełny tekst źródłaSavage, Andrew Patrick. "An investigation into the use of flow-focusing atomization with spray drying for the production of narrow particle size distributions". Thesis, University of Birmingham, 2015. http://etheses.bham.ac.uk//id/eprint/6309/.
Pełny tekst źródłaXUE, JIANQING. "COMPUTATIONAL SIMULATION OF FLOW INSIDE PRESSURE-SWIRL ATOMIZERS". University of Cincinnati / OhioLINK, 2004. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1100228747.
Pełny tekst źródłaLi, Jianing. "Characterization of a Novel Porous Injector for Multi-Lean Direct Injection (M-LDI) Combustor". University of Cincinnati / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1530269081550143.
Pełny tekst źródłaGosselin, Valentin. "Etude expérimentale de la formation d'un spray à partir d'un film liquide annulaire cisaillé". Thesis, Toulouse, INPT, 2019. http://www.theses.fr/2019INPT0004.
Pełny tekst źródłaOne way to increase efficiency and reduce pollution in the transportation and energy domain is designing fuel injectors with better atomization. In this thesis, experiments were performed on a prefilming airblast atomizer often used in gas turbines. For this purpose, a model device with a cylindrical configuration was created to study the shearing of a film of water subjected to an internal high speed air flow. High speed shadowgraphy technique was used to analyse the development of the liquid film (frequency and wave celerity) and the atomization of the sheet at the injector outlet (breakup mode). The modification of the injection parameters (velocity of flows) revealed a link between the topology of the liquid film and the primary atomization regime. Finally,the influence of the geometry of the injector (prefilming length) about the mode of primary atomization was also highlighted with an exploratory study
Wittner, Marc Oliver [Verfasser]. "Application of Air-Core-Liquid-Ring atomization in spray drying processes: Proof of concept and Methods for process design / Marc Oliver Wittner". München : Verlag Dr. Hut, 2020. http://d-nb.info/1220567892/34.
Pełny tekst źródłaSeidu, Iddrisu. "Analytical and Numerical Validation of Nozzle Spray Measurement Data Obtained from a Newly Developed Production System". Cleveland State University / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=csu1446504762.
Pełny tekst źródłaSilva, Paula Luciana Bezerra da. "Deposição por spray pirólise de filmes de ferrita de lantânio dopada com estrôncio e cobalto e sua caracterização microestrutural e de propriedades elétricas". reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2015. http://hdl.handle.net/10183/156322.
Pełny tekst źródłaThis work investigated the deposition conditions of thin lanthanum ferrite films doped with strontium and cobalt – La1-xSrxCo1-yFeyO3-δ (LSCF) through the spray pyrolysis technique using inorganic precursors and silicon as a substrate. Water and ethanol were used in the proportion (3:1) as solvent in the preparation of the solution to be sprinkled. The depositions were carried out at different temperatures: 130°C, 150°C, 170°C and 200°C. The films of LSCF were analyzed by X-ray diffraction and scanning electron microscopy before and after thermal treatment. The XRD results showed the obtainment of crystalline phase of LSCF after thermal treatment at 750°C/2hours and secondary phase of La2O3. The sprays of solutions with different proportions of ethanol (0%, 50%, 75% and 100%) were analyzed using a fast high-resolution camera and a laser with a wavelength of 532nm.The results showed those deposition temperature and solvente boiling points are important parameters to determine the thin morphology Higher ethanol levels promote an increase in the cone angle values and that the property of the surface tension exerts significantly greater influence on issues involving the structure of the spray, the atomization of the liquid, the droplets formation and the breaking point of the solutions. The XRD results showed the obtainment of majority crystalline phase of LSCF after thermal treatment at 750°C/2 hours with the presence of secondary phase of La2O3. The SEM images showed formation of films for the distance of 120 mm, although only at the temperature of 200°C it presents porous morphology before and after thermal treatment. The presence of interdiffusion and microporosity was observed for this film. For different LSCF compositions under the conditions of 120 mm and 200°C, the films of La1-xSrx Co0,2Fe0,8 with x = 0,6; 0,9 and 0,7 presented porous morphology after thermal treatment. Otherwise, the film of La0,8Sr0,2Co0,2Fe0,8 showed the highest ionic/electrical conductivity. The presence of secondary phase (La2O3, SrO2 and La2CoO3) evidenced by XRD promoted a decrease in ionic/electrical conductivity and in the activation energy.
Remigi, Alberto. "Modélisation numérique d'un injecteur aéromécanique : de l'écoulement interne au spray dispersé". Thesis, Normandie, 2021. http://www.theses.fr/2021NORMR012.
Pełny tekst źródłaThe more stringent regulation about aeronautical engines emission posed by ICAO requires always more predictive design tools. The droplets diameter distribution produced during the atomization process is a key parameter in order to predict the pollutant emission released during the combustion process. Thus the study of the atomization phenomenon with itsmulti-scale nature is a relevant and an important challenge. For this reason the objective of this work are: first to review the existent models in the literature to understand their key features in order to define a classification that gives guidelines on the modeling choices; second to apply industrial oriented approaches on an aeronautical configuration, in order to propose an improvement of the available design tools. A systematic classification of the models is done with respect to the length-scale considered to represent the interface characteristics. From this point of view, it is possible to distinguish two kinds of approaches: the separated phases representation and the mixed phases representation. The diffuse interface approaches belongs on the second category together with many other approaches, compressible and incompressible, that share the same characteristic: they considers a mixture that contains both phases. An air-assisted liquid sheet configuration has been built to test different models in order to define a metric of comparison. Two different models using the sharp interface approach (ARCHER and InterFoam ), two models using the diffuse interface approach (CEDRE and ELSA ) and an hybrid model (ICMelsa ) have been considered on this test case. A comparison on two parts, based on statistical quantities, has been proposed. A fist part called "classical study", compare the first order statistics showing that all approaches lead to very similar results, as soon as certain level of mesh resolution is achieved. At the contrary the second order statics present noticeable differences. These results motivate a second part called "phase analysis" to study the link between the small scale representation of the interface and the second-order statics. In particular, the phase marker variance and the associated segregation level are found to be sensible indicators of the interface description. A 1D signal analysis shows that they can be used to detect any departure from the separated phases representation.Then the importance of the phase indicator variance is demonstrated on other second-order statistics: Reynolds stress components and turbulent liquid flux. Thus, second-order statistics are partly described with direct mixed phases representations and require complementary model to be fully recovered. A first attempt, based on a linear approach, is proposed to model the level of segregation of mixed phases representation. It is based on the filtering of a fully segregated signal at a given scale. In a second part of this thesis, an industrial test case (a pressure swirling injector) proposed by SAFRAN Aircraft Engines is studied. Three industrial oriented models, among those studied in the first part, have been applied to simulate this injector flow (InterFoam , ELSA , ICMelsa). Their present numerical approaches are able to work with complex geometries, with a computational effort representative of the industrial current standards. The results of the three models (liquid film thickness, breakup length and Sauter Mean Diameter) have been compared with respect to the available experimental data. Eventually, a proposal to improve the ICMelsa model multi-scale have been successfully tested on the liquid sheet configuration and implemented to further improve the results of the SAFRAN Aircraft Engines industrial case. These results have shown that we are very close to predict the characteristics of a spray produced by a real aeronautical injection system
Le normative più rigorose sulle emissioni dei motori aeronautici poste dall’ICAO, richiedono strumenti di progettazione sempre più predittivi. La distribuzione dei diametri delle droplets prodotte durante il processo di atomizzazione è un parametro chiave per predire l’emissione di inquinanti rilasciati durante il processo di combustione. Lo studio del fenomeno di atomizzazione con la sua natura multi scala diventa una sfida rilevante. Per questo motivo, gli obiettivi di questo lavoro sono: in primo luogo una revisione dei modelli esistenti in letteratura per comprenderne le caratteristiche chiave al fine di definire una classificazione che dia delle linee guida sulle scelte di modellistica; in secondo luogo applicare approcci orientati all’industria ad una configurazione aeronautica, al fine di proporre un miglioramento degli strumenti di progettazione disponibili al giorno d’oggi. Nella prima parte del PhD proponiamo una classificazione sistematica dei modelli rispetto alla scala di lunghezza considerata per rappresentare l’interfaccia. Da questo punto di vista, è possibile distinguere due tipi di approccio: una rappresentazione a fasi separate e una rappresentazione delle fasi miste. Gli approcci a interfaccia diffusa appartengono alla seconda categoria insieme a molti altri approcci (che ricorrano ad un approccio comprimibile o incomprimibile) che condividono la stessa caratteristica: considerano una miscela che contiene entrambe le fasi. È stata realizzata una configurazione air-assisted liquid sheet per testare diversi modelli al fine di definire una metrica di confronto. In questo caso per i test sono stati considerati due diversi modelli che utilizzano l’approccio sharp interface (ARCHER e InterFoam ), due modelli che utilizzano l’approccio a interfaccia diffusa (CEDRE e ELSA ) e un modello ibrido (ICMelsa ). È stato proposto un confronto su due parti, basato su statistiche di diversa natura. Una prima parte chiamata "studio classico", confronta le statistiche del primo ordine, le quali mostrano che tutti gli approcci portano a risultati molto simili non appena viene raggiunto un certo livello di risoluzione della mesh. Al contrario, le statistiche di secondo ordine presentano notevoli differenze. Questi risultati motivano una seconda parte dello studio, chiamata "analisi di fase" sviluppata per studiare il legame tra le piccole scale dell’interfaccia e le statiche di secondo ordine. In particolare, la varianza del marker di fase e il livello di segregazione associato si trovano ad essere indicatori sensibili alla descrizione dell’interfaccia. Un’analisi di un segnale 1D mostra che questi due indicatori possono essere utilizzati per rilevare qualsiasi deviazione dalla rappresentazione a fasi separate. successivamente l’importanza della varianza del marker di fase è dimostrata su altre statistiche di secondo ordine: componenti del tensore degli sforzi di Reynolds e flusso liquido turbolento. Pertanto, le statistiche di secondo ordine che sono descritte con una rappresentazione a fasi miste richiedono un modello complementare per essere completamente recuperate. Un primo tentativo, basato su un approccio lineare, è proposto per modellare il livello di segregazione della rappresentazione a fasi miste. Si basa sul filtraggio di un segnale completamente separato su una data scala. In una seconda parte della tesi viene studiato un caso industriale (un iniettore di tipo swirling) proposto dall’azienda SAFRAN Aircraft Engines . Per simulare il flusso prodotto da questo iniettore sono stati applicati tre modelli (con un approccio industriale) tra quelli studiati nella prima parte (InterFoam , ELSA , ICMelsa )
Delon, Antoine. "Instabilité de flapping : origine et effets sur la structure et le spray d'un jet atomisé". Thesis, Université Grenoble Alpes (ComUE), 2016. http://www.theses.fr/2016GREAI074/document.
Pełny tekst źródłaJet or sheet atomized by a fast coaxial gas jet is currently used in industry, like aeronautical propulsion (turbofan) or spatial propulsion (cryotechnic rocket engine). Many physical processes allows liquid coherent structure fragmentation into drops. Stripping, which appears downstream near injector, has been largely studied (Marmottant et Villermaux 2004, Hong & al 2004), mecanisms has been correctly described.However, the origin of large scale - or 'flapping' instabilities - intervening further downstream, instabilities that are causing the production of large drops, remains poorly understood. This is particularly true for cylindrical jets which, unlike the case of sheets, have been the subject of very few studies. We are therefore committed to understand the origin of the "flapping", to analyze its relationship with interfacial shear instabilities, and to quantify its impact on the structure of the jet as well as on the drops produced. For this, experiments were carried out in water/air on wide set of parameters, both in terms of phasic speed than the dimensions of the gas gap and liquid diameter. Special care were made to the internal flow control.For all the geometries, we showed that the length of the liquid cone is driven by the large scale displacements and not by the stripping process. Furthermore, the length of brokenness jet presents a decline marked with the gas speed, then remains constant beyond a critical gas speed. A model was proposed for this asymptotic behavior in which the break-up length is driven by the report of the liquid injection speed to a capillary speed built on the liquid diameter.Measurement of the frequency of large scale displacement technology has been implemented from images acquired by shadowgraphy proved operational over the gas velocity range considered. This frequency, which varies not spatially, present two behaviors: a first where it increases with the speed of the gas, and a second where it remains independent of the gas speed. This second scheme is not mentioned in the literature. For the original plan, the link between flapping and shear instability has been demonstrated based on analyses of stability. The associated Strouhal number is controlled by the shear gas side. The dependence of the frequency of heartbeat to the thickness of vorticity gas side is thus established when shear instability is driven by an inviscide mechanism. For the second scheme, the opportunistic nature of the flapping has been demonstrated using forcing experience: the flapping amplifies liquid structures of wavelength greater than those associated with shear instability. A Strouhal number built on liquid jet diameter and the speed of the liquid jet at break distance has been proposed. Finally, the ratio of the diameter of the liquid jet at the wavelength of the shear instability seems relevant to define the border between these two regimes.Sizes drops produced on the symmetry axis were measured using an optical probe. It appears that granulometric distribution is evolving strongly with speed gas, and it is multi-modal, reflecting the presence of several mechanisms of brokenness. The average size of the drops decreases overall as UG - 2, in the limit of strong numbers of aerodynamic Weber. This medium size is also very sensitive to geometry: it decreases when the thickness of the gas increases until it reaches a floor value, and it grows with the liquid diameter. Finally, by forcing large amplitude lateral displacement, the average radial distribution of sizes of drops has been made much more homogeneous, and the average size of the drops on the axis has been reduced by a factor of 2. These results therefore open opportunities in terms of control of atomization
Esteves, Bruno Neves. "Influência do processo de secagem por pulverização mecânica (spray dryer) no tamanho de partícula e densidade aparente do café solúvel". Universidade de São Paulo, 2006. http://www.teses.usp.br/teses/disponiveis/3/3137/tde-03072007-172100/.
Pełny tekst źródłaBrazil is a big producer and consumer of coffee. The drink is the second most consumed in the country. Instant coffee is an alternative for daily consumption since it dispenses with all the apparatuses for preparing the drink, being necessary only hot water. The dry particle size is directly related to the bulk density of the product. Coffee extract drying tests were made in a co-current flow spray-dryer with atomization by disc with a varying inlet air temperature (140 - 170 °C) and disc velocity (27000 - 33000 rpm). The particle size analysis has shown the tendency for bigger particles to form at lower drying temperatures (26 - 36 µm). The influence of inlet air temperature and the atomizer disc spin velocity were noted in water activity analysis. The bulk density was not significantly modified by the parameters studied in the experiments.
Martí, Gómez-Aldaraví Pedro. "DEVELOPMENT OF A COMPUTATIONAL MODEL FOR A SIMULTANEOUS SIMULATION OF INTERNAL FLOW AND SPRAY BREAK-UP OF THE DIESEL INJECTION PROCESS". Doctoral thesis, Universitat Politècnica de València, 2014. http://hdl.handle.net/10251/43719.
Pełny tekst źródłaMartí Gómez-Aldaraví, P. (2014). DEVELOPMENT OF A COMPUTATIONAL MODEL FOR A SIMULTANEOUS SIMULATION OF INTERNAL FLOW AND SPRAY BREAK-UP OF THE DIESEL INJECTION PROCESS [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/43719
TESIS
Premiado
Aubignat, Emilie. "Contribution à la compréhension et à la maîtrise du procédé de projection plasma de suspensions céramiques". Thesis, Belfort-Montbéliard, 2014. http://www.theses.fr/2014BELF0238.
Pełny tekst źródłaSuspension plasma spray (SPS) is a surface coating process that consists in injecting a suspension (solid particles of about 1 μm or less, dispersed in a liquid phase) in a high-energy plasma flow. Particles are heated, accelerated towards a substrate, flattened and submitted to a rapid solidification (order of 106 K.s-1). Layer after layer, a coating is formed on the substrate surface and brings new functional properties. This variation of the conventional plasma spray process allows the manufacturing of coatings with finer thickness of few tens of μm and a reduced structural scale that can lead to improved coating properties, like hardness or thermal conductivity. Even though this process has been studied since the middle of the 1990’S and known a fast-growing interest, industrial applications are not finalized and their development needs to be pursued. Indeed, the suspension injection in a thermal jet leads to complex phenomena such as suspension droplet fragmentation or liquid phase evaporation. Up to now, these mechanisms are not perfectly understood and controlled and deserve to be further studied to understand interactions between these fine particles and the plasma. This thesis focuses on the SPS process with ceramic suspensions and a twin-fluid nozzle as injection system. Two materials were chosen: alumina, known for its difficulty to be conventionally sprayed and whose crystalline phase formation represents a source of information about particle thermal history, and also yttria, in order to confirm the tendencies observed for alumina. Firstly, the suspension injection was optimized by working on two areas. The first area concerns suspension formulation. This led to obtain, with different liquid phases, stable and dispersed suspensions, whose properties are perfectly known. Such suspensions ensure reproducibility of the process at this level and limit the risk of injection system clogging. The second area is about the three-step mechanical conception of a pneumatic atomizer, adapted to the SPS process. This study began with the characterization of a commercial nozzle, in particular by testing the suspension injection into a plasma flow. Tests being little convincing, the study was carried on with the development of a new atomizer geometry, inspired from the commercial model. Trials drove to the manufacturing of satisfying spray beads and coatings. This study was finally completed with the optimization of this new geometry by highlighting the influence of several key parameters on the atomized jet features. Secondly, diagnostic tools were implemented to qualify the injection. Suspension jet was characterized in terms of geometry and droplet sizes, using respectively shadowgraphy and laser diffraction. Shadowgraphy was used again for optimizing the suspension injection into plasma by allowing the adjustment in real time of inlet atomizer pressures. In-flight particle properties were then studied thanks to particle collection onto a substrate and particle image velocimetry (PIV). This tool also provided additional information on the suspension injection. Finally, the resulting coatings were characterized in terms of morphology (SEM), porosity rate (SEM image analysis and USAXS) and crystalline phases (DRX and EBSD). The cross-checking of the information obtained with all these techniques brought out the role of the suspension liquid phase and of the mass load on the coating microstructure. These works contributed to enhance the knowledge about the SPS process and justified the use of a twin-fluid nozzle to obtain specific microstructures of coatings, whose functional characterizations have still to be done
Abuzahra, Fakhry. "Etude Expérimentale des Processus d'Atomisation Textuels : Application à des Ecoulements Cavitants". Thesis, Normandie, 2019. http://www.theses.fr/2019NORMR028/document.
Pełny tekst źródłaTextural atomization designates the mechanism of drop peeling from the interface of a free liquid flow. This mechanismis controlled by the characteristics of the flow issuing from the injector and manifests at its vicinity. Almost uninvestigated,textural atomization is a rapid phenomenon, implies very small ligamentary structures and produces a mist of fine droplets.The work of this thesis is an experimental investigation of a textural atomization process observed on flows issuing fromcavitating injector. Three academic transparent atomizers are used and optical diagnostics are implemented: LDV (LaserDoppler Velocimetry) and PDPA (Phase Doppler Particle Analyzer) to describe the internal flow and the spray, respectively,and still imaging at high spatial resolution or high-speed imaging for the internal and external flows. A first observation revealsa strong link between the cavitation regime and the textural atomization process. An analysis implying the measurementof the variability of the internal flow and of the atomization process quantifies this link. Here, the atomization process isdescribed by the measurement of its scale distribution. Associated with the concept of equivalent system, this multi-scaleanalysis returns a mathematical expression for the investigated atomization process. This result is unprecedented. Completedby a mathematical description of the spray drop-diameter distribution, it offers a new support to build a model of ligamentaryatomization processes presented in this work and that connects ligament size and deformation to the drop populations. Thesefine analyses provide a better knowledge of the investigated atomization process. For instance, we learn that, at fixed flowrate, the height of the inlet pipe feeding the orifice has no influence on the atomization process. Furthermore, a criterion hasbeen established to identify the smallest ligament deformation scale implied in the drop production
Deng, Tian. "LES combined with statistical models of spray formation closely to air-blast atomizer". Thesis, Ecully, Ecole centrale de Lyon, 2011. http://www.theses.fr/2011ECDL0037/document.
Pełny tekst źródłaThis thesis introduced an extension to stochastic approach for simulation of air-blast atomization closely to injector. This approach was previously proposed in publications of Gorokhovski with his PHD students. Our extension of this approach is as follows. In the framework of LES approach, the contribution of primary atomization zone is simulated as an immersed solid body with stochastic structure. The last one is defined by stochastic simulation of position-and-curvature of interface between the liquid and the gas. As it was done previously in this approach, the simulation of the interface position was based on statistical universalities of fragmentation under scaling symmetry. Additionally to this, we simulate the outwards normal to the interface, assuming its stochastic relaxation to isotropy along with propagation of spray in the down-stream direction. In this approach, the statistics of immersed body force plays role of boundary condition for LES velocity field, as well as for production of primary blobs, which are then tracked in the Lagrangian way. In this thesis, the inter-particle collisions in the primary atomisation zone are accounted also by analogy with standard kinetic approach for the ideal gas. The closure is proposed for the statistical temperature of droplets. The approach was assessed by comparison with measurements of Hong in his PHD. The results of computation showed that predicted statistics of the velocity and of the size in the spray at different distances from the center plane, at different distances from the nozzle orifice, at different inlet conditions (different gas velocity at constant gas-to-liquid momentum ratio, different gas-to-liquid momentum ratio) are relatively close to measurements. Besides, the specific role of recirculation zone in front of the liquid core was emphasized in the flapping of the liquid core and in the droplets production
Blanchard, Ghislain Emmanuel. "Modélisation et simulation multi-échelles de l'atomisation d'une nappe liquide cisaillée". Thesis, Toulouse, ISAE, 2014. http://www.theses.fr/2014ESAE0043/document.
Pełny tekst źródłaIn order to improve efficiency of aircraft combustion chambers and reduce polluting emissions,engine manufacturers try to achieve a better control on fuel atomization, which is usually injectedas a jet or liquid sheet. As experiments are expensive and time consuming, a numerical tool able to simulate atomization would be a powerful asset in engine conception design. However, simulation ofthe whole atomization process with commonly used approach in computational fluid dynamics is still prohibitive due to the multi-scale nature of the phenomenon.The objective of this thesis is to develop a new approach allowing the simulation of the spray formation for a industrial configuration in the near future. This involves coupling of two types of models.The first one, called two-fluid model, is based on the Navier-Stokes equations for two immiscible compressible fluids. This one is used to describe the large scales of the atomization mechanism corresponding to the formation of ligaments and liquids blobs in the near-injector area. The second one,called spray model, is based on a kinetic equation. Further downstream from the injector, this model describes statistically the evolution of the droplet cloud produced by the primary fragmentation of liquid jet. The main difficulty, in terms of both modeling and algorithmic, is the coupling of these twomodels.This has been achieved by introducing an atomization and an impact models which ensure liquid transfer between the two-fluid model and the spray model.This new approach was applied to the numerical simulation of sheared liquid sheets. Comparisons between numerical and experimental results show how the two-fluid model predicts the influence of injector geometry and injection conditions on the primary atomization of the liquid sheet. Concerning droplets production, the atomization model is able to reproduce the unsteady nature of this mechanism when transferring liquid phase from the two-fluid model to the spray model. Test cases for the impact model also validate the robustness and generality of the coupling approach
Oruganti, Surya Kaundinya. "Stochastic models on residual scales in LES of sprays in diesel-like conditions : spray formation, turbulent dispersion and evaporation of droplets". Thesis, Lyon, 2020. http://www.theses.fr/2020LYSEC042.
Pełny tekst źródłaThis thesis concerns with the Large Eddy Simulations (LES) of fuel sprays in direct-injection engines. Given the high injection velocities of sprays, the resulting turbulent flow may be characterized by energetic intermittent structures at small spatial scales. Therefore, the emphasis in this thesis is put on stochastic simulation of turbulent effects on unresolved scales in the engine relevant conditions. The impact of this effect on spray primary and secondary atomization, on droplets dispersion and evaporation represents the main focus in this thesis. The further assessment and modification of two different approaches, developed recently, was the main objective in this thesis. The first one is addressed to LES-SSAM (stochastic sub-grid acceleration model) approach, in which the Navier-Stokes equations are forced on residual scales. This forcing is given by the Ornstein-Uhlenbeck stochastic process constructed in a way to represent the stochastic properties of the subgrid acceleration, known from the experiment and DNS. In the framework of this approach, with the expression of the acceleration norm modified for the wall-bounded conditions, the first step concerned the simulation of the nozzle internal flow on the coarse grid. The results showed the efficiency of this approach. Another step in this part was to combine LES-SSAM with the interface tracking VOF method in the simulation of the near-field of the spray. The performed assessment of this approach in comparison with measurements and with alternative approaches known from the literature demonstrated a potential of such combination of two methods. The second approach in this thesis, in which the intermittency effects on residual scales are also on target, concerned the stochastic modeling of the secondary breakup, dispersion and evaporation of droplets; introducing the two-way coupling between droplets and a highly turbulent flow. Here, the assessment and further development of stochastic models of droplets represent the main contribution in this thesis. So, the model of the secondary breakup is controlled by the stochastic log-normal process for the viscous dissipation rate. The same stochastic variable is the key variable for the dispersion model of droplets below and above the Kolmogrov scale. The droplet equation of motion for the latter case was modified addressing the significant role to simulation the stochastic direction of the droplet acceleration. Finally, the new stochastic model of the turbulent evaporation, in which the stochastic mixing process is a part of the evaporation model, is also represented in this thesis. The different stochastic models outlined above are assessed in comparison to the state-of-art models available in literature and the experiments of Engine Combustion Network (ECN). The results have shown that stochastic models give a good representation of both macroscopic and microscopic spray characteristics on relatively coarse grids
Zaremba, Matouš. "Experimentální analýza procesu rozpadu kapaliny u šumivé trysky". Doctoral thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2018. http://www.nusl.cz/ntk/nusl-370740.
Pełny tekst źródłaGuézennec, Nicolas. "Contrôle actif de la combustion diphasique". Thesis, Toulouse, INPT, 2010. http://www.theses.fr/2010INPT0022/document.
Pełny tekst źródłaThe present work focuses on active control of two-phase combustion in industrial burners. The generic method explored in this thesis consists in controlling the injected fuel spray with transverse air jets. Two families of these jet actuators are tested on a coaxial airblast atomizer. The first system (Dev) is used to modify the trajectory of the spray, while the second one (Sw) introduces swirl into the spray to modify its spreading rate and mixing with the surrounding air. Experimental characterisations of the controlled flow with Schlieren visualisations and Phase Doppler Anemometry (PDA) show that actuators induce important effect on the spray. The deviation angle reaches 30° for the actuator (Dev) and the expansion rate increases of 80 % in the swirl case (Sw). Simulations of the experiment are then performed with the CFD code AVBP. The gas flow is computed with Large Eddy Simulation (LES). A Lagrangian formulation is used to simulate droplets trajectories. A particular attention is given to the injection of the gas flow and the droplets in the calculations. Therefore, a new non-reflecting characteristic boundary condition (VFCBC) has been derived to inject turbulent flows in compressible LES. A good agreement is observed between simulation and experiment. Control effects on the spray topology ( features, deviation, spread rate) and on the droplets velocities and diameters are correctly described by the Lagrangian LES
Makhlouf, Samir. "Contribution à l'étude de l'impact de la cavitation sur les processus physiques de l'atomisation primaire des jets d'injecteurs essence". Thesis, Rouen, INSA, 2015. http://www.theses.fr/2015ISAM0005/document.
Pełny tekst źródłaIn order to get closer to the homogeneous mixture conditions of a gasoline engine, different fluids are injected into the atmosphere at varying upstream pressure and temperature. Five three-hole real injector prototypes from Continental were used. When injection pressure is increased, the internal flow goes through four regimes where the cavitation development level varies from one to another. The discharge coefficient Cd was found mainly dependent on the cavitation number. At the cavitation critical point, two correlations between Cd and the critical cavitation number on one side respectively, and the correspondent Reynolds number on the other side were found. The near field jet is ruled by three dimensionless numbers : Weber, Reynolds and cavitation. The effect of each one of them on the jet angle at the orifice outlet was obtained. By comparing the results of two injectors, it was found that the length over diameter ratio has a first order influence on the jet angle
Belsito, Danielle L. "Application of Computational Thermodynamic and Solidification Kinetics to Cold Sprayable Powder Alloy Design". Digital WPI, 2014. https://digitalcommons.wpi.edu/etd-dissertations/28.
Pełny tekst źródłaSapík, Marcel. "Testování průhledného modelu tlakové vířivé trysky". Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2018. http://www.nusl.cz/ntk/nusl-378279.
Pełny tekst źródłaBroukal, Jakub. "Effervescent Breakup and Combustion of Liquid Fuels: Experiment and Modelling". Doctoral thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2014. http://www.nusl.cz/ntk/nusl-234230.
Pełny tekst źródłaAhmed, Tushar. "Atomization and Combustion of Hybrid Electrohydrodynamic-Air-Assisted Sprays". Thesis, The University of Sydney, 2022. https://hdl.handle.net/2123/28180.
Pełny tekst źródłaZaremba, Matouš. "Vliv provozních parametrů na kvalitu rozprašování kapalin u dvou-médiových trysek". Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2013. http://www.nusl.cz/ntk/nusl-230587.
Pełny tekst źródłaDemeure, Lauriane. "Comportement thermodynamique de réservoirs d’ergols cryogéniques : étude expérimentale et théorique d’un système de contrôle pour des missions spatiales de longue durée". Thesis, Grenoble, 2013. http://www.theses.fr/2013GRENI068/document.
Pełny tekst źródłaThis PHD thesis deals with the study of a pressure control system inside a cryogenic propellant tank for long duration space missions. This system must be able to reduce propellant losses induced by direct venting, which is the simplest pressure control system. The alternative system which has been studied, called Thermodynamic Vent System (TVS), is based on reinjecting subcooled spray to make the pressure and temperature decrease in a heated tank. The system performance has been analysed developing simultaneously an experimental setup, adapted to laboratory environment, and a theoretical 0D-modelling of subcooled spray impact on tank's thermodynamic characteristics. Facing experimental and theoretical results has permitted to validate the 0D-modelling tool. Inputing the real system characteristics in theoretical modelling has enabled to assess the effective gains of thermodynamic vent system. Finally, optimal solutions to control pressure inside a cryogenic propellant tank for long duration space missions have been proposed
Zaheer, Hussain. "Transient microscopy of primary atomization in gasoline direct injection sprays". Thesis, Georgia Institute of Technology, 2015. http://hdl.handle.net/1853/53611.
Pełny tekst źródłaĎurdina, Lukáš. "Stanovení charakteristik spreje pomocí optických měřících metod". Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2012. http://www.nusl.cz/ntk/nusl-230349.
Pełny tekst źródłaDyson, Joshua. "GPU accelerated linear system solvers for OpenFOAM and their application to sprays". Thesis, Brunel University, 2018. http://bura.brunel.ac.uk/handle/2438/16005.
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