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Auliano, Manuel. "Investigation and validation of void and pressure drop correlations in BWR fuel assemblies". Thesis, KTH, Fysik, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-169548.
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Schroll, Cynthia A. "Spectroelectrochemical Real-Time Monitoring of f-block Elements during Nuclear Fuel Reprocessing". University of Cincinnati / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1367926766.
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Singh, Sandeep. "Thermo-mechanical Behavior of Glass Based Seals for Solid Oxide Fuel Cells". University of Cincinnati / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1288379341.
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Couval, Romain. "Scale up of a test fluid for testing the fuel system robustness against soft particles in biodiesels". Thesis, Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-85745.
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The future of fuels will most probably be a mixture of different fuels, called drop-in fuels. It is already known that these drop-in fuels will lead to solubility issues, with creation of deposit on crucial fuel system parts, due to the formation of soft particles. The fuel system of the future should be robust against any type of soft particles. Today, there is no scaled up test fluid existing for testing full scale fuel systems. The objective of this thesis was to develop a scaled up test fluid which is a key element to the development of a test method to enhance the fuel system robustness against soft particles. A test fluid was achieved by a concentrate of calcium soap diluted two thousand times to reach a volume of 1000 litres with a concentration of 1,4 ppm. The concentration was measured by gas chromatography mass spectroscopy method following a derivatisation as sample preparation. The formation of the concentrate was established by changing the type of fuel, the level of aging, the amount of calcium and other counterions and eventually by addition of third elements. The concentrate was made of aged B100, calcium oxide powder and water. The test fluid was made by diluting the concentrate with fresh B7 and a protocol to characterise the stability of this test fluid was developed. This test fluid was tested under real condition in a filter rig giving homogeneous concentration all along the experiment, which confirmed the stability of the test fluid.
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Hill, Theresa Y. "Understanding Drop-on-Demand Inkjet Process Characteristics in the Application of Printing Micro Solid Oxide Fuel Cells". Wright State University / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=wright156167105938597.
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Hammill, Matthew. "Ignition delay of oxygenated fuel droplets : development of a 1 second drop tower and initial 1-g test results /". Full text available online, 2006. http://www.lib.rowan.edu/find/theses.
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Gunarathne, Duleeka. "Advanced Gasification of Biomass/Waste for Substitution of Fossil Fuels in Steel Industry Heat Treatment Furnaces". Doctoral thesis, KTH, Materialvetenskap, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-190938.
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With the current trend of CO2 mitigation in process industries, the primary goal of this thesis is to promote biomass as an energy and reduction agent source to substitute fossil sources in the steel industry. The criteria for this substitution are that the steel process retains the same function and the integrated energy efficiency is as high as possible. This work focuses on advanced gasification of biomass and waste for substitution of fossil fuels in steel industry heat treatment furnaces. To achieve this, two approaches are included in this work. The first investigates the gasification performance of pretreated biomass and waste experimentally using thermogravimetric analysis (TGA) and a pilot plant gasifier. The second assesses the integration of the advanced gasification system with a steel heat treatment furnace. First, the pyrolysis and char gasification characteristics of several pretreated biomass and waste types (unpretreated biomass, steam-exploded biomass, and hydrothermal carbonized biomass) were analyzed with TGA. The important aspects of pyrolysis and char gasification of pretreated biomass were identified. Then, with the objective of studying the gasification performance of pretreated biomass, unpretreated biomass pellets (gray pellets), steam-exploded biomass pellets (black pellets), and two types of hydrothermal carbonized biomass pellets (spent grain biocoal and horse manure biocoal) were gasified in a fixed bed updraft gasifier with high-temperature air/steam as the gasifying agent. The gasification performance was analyzed in terms of syngas composition, lower heating value (LHV), gas yield, cold gas efficiency (CGE), tar content and composition, and particle content and size distribution. Moreover, the effects on the reactions occurring in the gasifier were identified with the aid of temperature profiles and gas ratios. Further, the interaction between fuel residence time in the bed (bed height), conversion, conversion rate/specific gasification rate, and superficial velocity (hearth load) was revealed. Due to the effect of bed height on the gasification performance, the bed pressure drop is an important parameter related to the operation of a fixed bed gasifier. Considering the limited studies on this relationship, an available pressure drop prediction correlation for turbulent flow in a bed with cylindrical pellets was extended to a gasifier bed with shrinking cylindrical pellets under any flow condition. Moreover, simplified graphical representations based on the developed correlation, which could be used as an effective guide for selecting a suitable pellet size and designing a grate, were introduced. Then, with the identified positive effects of pretreated biomass on the gasification performance, the possibility of fuel switching in a steel industry heat treatment furnace was evaluated by effective integration with a multi-stage gasification system. The performance was evaluated in terms of gasifier system efficiency, furnace efficiency, and overall system efficiency with various heat integration options. The heat integration performance was identified based on pinch analysis. Finally, the efficiency of the co-production of bio-coke and bio-H2 was analyzed to increase the added value of the whole process. It was found that 1) the steam gasification of pretreated biomass is more beneficial in terms of the energy value of the syngas, 2) diluting the gasifying agent and/or lowering the agent temperature compensates for the ash slagging problem in biocoal gasification, 3) the furnace efficiency can be improved by switching the fuel from natural gas (NG) to syngas, 4) the gasifier system efficiency can be improved by recovering the furnace flue gas heat for the pretreatment, and 5) the co-production of bio-coke and bio-H2 significantly improves the system efficiency.QC 20160825
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Russi, Luigi. "modeling the pressure drop and thermal profile of a novel solid oxide fuel cell stack design with a homogenized approach". Master's thesis, Alma Mater Studiorum - Università di Bologna, 2018.
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Le celle a combustibile a ossidi solidi (SOFCs) rappresentano una tecnologia chiave in uno scenario di decarbonizzazione delle attività umane per i prossimi anni.
Gli stack attualmente disponibili presentano elevati gradienti di temperatura e grandi perdite di carico attraverso lo stack, così come distribuzioni di corrente disuniformi, problemi di perdita di contatto e di deterioramento.
Un innovativo design dello stack, detto"Chessboard", è stato ideato al DTU Energy.
La determinazione dei campi di temperatura, pressione e velocità nello stack tramite simulazione risulta fondamentale per valutare la qualità di un certo design. Infatti non sempre è possibile misurare sperimentalmente grandezze fisiche locali all'interno dello stack.
In questo lavoro un modello tridimensionale (3D) dello stack è stato costruito. L'approccio modellistico utilizzato si basa sulla tecnica di omogenizzazione. Un metodo efficiente a livello computazionale basato sull'utilizzo di una geometria semplificata, ma con proprietà termofisiche anisotropiche che rispecchino la vera geometria dello stack per reincrementare il livello di dettaglio.
Fra tutte le fisiche che descrivono i fenomeni in una SOFC, solo il moto dei fluidi e la trasmissione del calore sono effettivamente risolte dal modello nell'attuale stadio di sviluppo, mentre i fenomeni elettrochimici sono definiti come parametri in ingresso.
Una volta impostato il modello, è stato eseguito uno studio parametrico, con lo scopo di ottenere i profili di temperatura e pressione in funzione delle dimensioni dello stack, dell'eccesso d'aria, della pressione in ingresso dell'aria e della dimensione dei pori. Individuando quindi una finestra di esercizio sicura per i 4 parametri considerati.
Dai risultati si evince che è possibile trovare diverse combinazioni di parametri che soddisfino l'obiettivo di progetto dato da limiti sui materiali costituenti lo stack, tutto questo con dei tempi di risoluzione nell'ordine dei minuti.
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Laesecke, Jan. "Production and characterization of biomass fast pyrolysis oil blends for combustion testing as drop-in fuel alternatives in a single cylinder diesel engine". Thesis, University of British Columbia, 2017. http://hdl.handle.net/2429/60409.
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This research sought to demonstrate the potential of biodiesel and softwood derived Fast Pyrolysis Oil (FPO) blends as an alternative low-carbon drop-in diesel fuel. FPO was supplied from an in-house fluidized bed reactor as well as a commercial source. Separate FPO-biodiesel blends from both FPO sources were prepared using initial volumetric ratios of 80:20 and 60:40 (biodiesel:FPO, by volume). Upon blending each performed volumetric ratio, mixing and a 24 hour settling period, two layers formed and the top, biodiesel-rich layers containing about 5 and 10 vol % FPO were decanted and characterized on the basis of a thermogravimetric analysis, viscosity, acid number, water content, elemental analysis, and heating value. Significant decreases in viscosity, acidity, and water content from the original FPO validated blending as means of extracting compounds suitable for use as fuels from pyrolytic liquids in biodiesel. A single cylinder, direct injection diesel engine was used to analyze the combustion performance of the FPO fuel blends against neat diesel and biodiesel. Fuel performance was characterized on the basis of a thermodynamic analysis and corresponding exhaust measurements for CO₂, CO, unburned hydrocarbons, particulate matter, and NOx. Two thermodynamic measurement campaigns were performed in order to provide insight into FPO fuel performance across various engine conditions. In addition to the thermodynamic measurements, in-cylinder high-speed photography was implemented to support the interpretation of thermodynamic combustion data. Engine testing revealed similar indicated efficiencies for biodiesel and diesel at all considered engine-operating modes, while blend fuels showed indicated efficiencies between 75 and 95% of diesel values. FPO fuels exhibited increased ignition delays and shorter combustion durations with greater FPO blend concentrations, though this could be partially compensated for using a pilot injection strategy. The longer ignition delays of the blend fuels resulted in overly lean regions of the cylinder, which produced largely premixed combustion events contributing to brake specific CO and uHC emissions up to 1.5 and 3.5 greater than diesel, respectively. Specific PM emissions were 41-62% lower for blend fuels than diesel. Both blends of in-house FPO showed similar PM emission performance, however at higher concentrations than low blend commercial fuel.Applied Science, Faculty of
Graduate
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Cao, Liu. "Corrosion and Stress Corrosion Cracking of Carbon Steel in Simulated Fuel Grade Ethanol". The Ohio State University, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=osu1345141634.
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CASTRO, ALFREDO J. A. de. "Análise experimental de velocidade crítica em elemento combustível tipo placa plana para reatores nucleares de pesquisa". reponame:Repositório Institucional do IPEN, 2017. http://repositorio.ipen.br:8080/xmlui/handle/123456789/28022.
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Submitted by Pedro Silva Filho (pfsilva@ipen.br) on 2017-11-17T17:27:31Z
No. of bitstreams: 0Made available in DSpace on 2017-11-17T17:27:31Z (GMT). No. of bitstreams: 0
Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)
Os elementos de combustível de um reator nuclear de pesquisa tipo MTR (\"Material Testing Reactor\") são, em sua grande maioria, formados por placas de combustível revestidas com alumínio contendo no cerne silicileto de urânio (U3Si2) disperso em matriz de alumínio. Essas placas possuem espessura da ordem de milímetros e comprimentos muito maiores em relação à sua espessura. Elas são dispostas paralelamente no conjunto que forma o elemento combustível, de maneira a formar canais entre elas com poucos milímetros de espessura, por onde escoa o fluido de refrigeração (água leve ou água pesada). Essa configuração, associada à necessidade de um escoamento com altas vazões para garantir o resfriamento das placas em operação, pode gerar problemas de falhas mecânicas das placas de combustível devido às vibrações induzidas pelo escoamento nos canais e, consequentemente, acidentes de proporções graves no caso de velocidade crítica que possa gerar o colapso das placas. Embora não haja ruptura das placas de combustível durante o colapso, as deflexões permanentes excessivas das placas podem causar bloqueio do canal de escoamento no núcleo do reator e levar ao superaquecimento nas placas. Para este trabalho, foram desenvolvidas uma bancada experimental com capacidade para altas vazões volumétricas (Q=100 m3/h) e uma seção de testes que simula um elemento combustível do tipo placa com três canais de resfriamento. A seção de testes foi construída com placas de alumínio e acrílico e foi instrumentada com sensores de deformação, sensores de pressão, um acelerômetro e um tubo de pitot. As dimensões da seção de testes foram baseadas nas dimensões do Elemento Combustível do Reator Multipropósito Brasileiro (RMB), cujo projeto está sendo coordenado pela Comissão Nacional de Energia Nuclear - CNEN. Os experimentos realizados alcançaram o objetivo de chegar à condição de velocidade crítica de Miller com o colapso das placas. A velocidade crítica foi atingida com 14,5 m/s levando a consequente deformação plástica das placas que formam o canal do escoamento. O canal central na entrada da seção de testes apresentou uma abertura de 3 mm em seu centro, causando um grande bloqueio do escoamento nos canais laterais. Este comportamento foi v constatado visualmente durante a desmontagem da seção de testes, ilustrado e discutido na análise de resultados apresentado neste trabalho. O bloqueio dos canais também foi observado por meio de gráficos de queda de pressão e por gráficos das deformações da entrada, centro e saída das placas contra a velocidade média da seção de testes. Observou-se uma queda da resistência hidráulica da seção de testes devido ao aumento da seção transversal de escoamento no canal central e um aumento exponencial das deformações quando da ocorrência da velocidade crítica. Comparativamente, o valor experimental obtido para velocidade crítica na seção de testes foi da ordem de 85% do valor obtido por cálculo com a expressão teórica de Miller. Os experimentos realizados permitiram um melhor entendimento da interação fluido estrutura em elementos de combustível tipo placa como: valores de frequências de vibrações naturais, instabilidade fluido elástica e desenvolvimento de técnicas para a detecção de valores de velocidade crítica.
Tese (Doutorado em Tecnologia Nuclear)
IPEN/T
Instituto de Pesquisas Energéticas e Nucleares - IPEN-CNEN/SP
CNPq:481193/2012-0
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Ahmed, Aqeel. "LES of atomization and cavitation for fuel injectors". Thesis, Normandie, 2019. http://www.theses.fr/2019NORMR048/document.
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Cette thèse présente la Simulation des Grandes Echelles (LES) de l’injection, de la pulvérisation et de la cavitation dans un injecteur pour les applications liées aux moteurs à combustion interne. Pour la modélisation de l’atomisation, on utilise le modèle ELSA (Eulerian Lagrangian Spray Atomization). Le modèle résout la fraction volumique du combustible liquide ainsi que la densité de surface d’interface liquide-gaz pour décrire le processus complet d’atomisation. Dans cette thèse, l’écoulement à l’intérieur de l’injecteur est également pris en compte pour une étude ultérieure de l’atomisation. L’étude présente l’application du modèle ELSA à un injecteur Diesel typique, à la fois dans le contexte de RANS et de LES.Le modèle est validé à l’aide de données expérimentales disponibles dans Engine Combustion Network (ECN). Le modèle ELSA, qui est normalement conçu pour les interfaces diffuses (non résolues), lorsque l’emplacement exact de l’interface liquide-gaz n’est pas pris en compte, est étendu pour fonctionner avec une formulation de type Volume of Fluid (VOF) de flux à deux phases, où l’interface est explicitement résolu. Le couplage est réalisé à l’aide de critères IRQ (Interface Resolution Quality), qui prennent en compte à la fois la courbure de l’interface et la quantité modélisée de la surface de l’interface. Le modèle ELSA est développé en premier lieu en considérant les deux phases comme incompressibles. L’extension à la phase compressible est également brièvement étudiée dans cette thèse. Il en résulte une formulation ELSA compressible qui prend en compte la densité variable de chaque phase. En collaboration avec l’Imperial College de Londres, la formulation de la fonction de densité de probabilité (PDF) avec les champs stochastiques est également explorée afin d’étudier l’atomisation. Dans les systèmes d’injection de carburant modernes, la pression locale à l’intérieur de l’injecteur tombe souvent en dessous de la pression de saturation en vapeur du carburant, ce qui entraîne une cavitation. La cavitation affecte le flux externe et la formulation du spray. Ainsi, une procédure est nécessaire pour étudier le changement de phase ainsi que la formulation du jet en utilisant une configuration numérique unique et cohérente. Une méthode qui couple le changement de phase à l’intérieur de l’injecteur à la pulvérisation externe du jet est développée dans cette thèse. Ceci est réalisé en utilisant le volume de formulation de fluide où l’interface est considérée entre le liquide et le gaz; le gaz est composé à la fois de vapeur et d’airambiant non condensableThis thesis presents Large Eddy Simulation (LES) of fuel injection, atomization and cavitation inside the fuel injector for applications related to internal combustion engines. For atomization modeling, Eulerian Lagrangian Spray Atomization (ELSA) model is used. The model solves for volume fraction of liquid fuel as well as liquid-gas interface surface density to describe the complete atomization process. In this thesis, flow inside the injector is also considered for subsequent study of atomization. The study presents the application of ELSA model to a typical diesel injector, both in the context of RANS and LES. The model is validated with the help of experimental data available from Engine Combustion Network (ECN). The ELSA model which is normally designed for diffused (unresolved) interfaces, where the exact location of the liquid-gas interface is not considered, is extended to work with Volume of Fluid (VOF) type formulation of two phase flow, where interface is explicitly resolved. The coupling is achieved with the help of Interface Resolution Quality (IRQ) criteria, that takes into account both the interface curvature and modeled amount of interface surface. ELSA model is developed first considering both phases as incompressible, the extension to compressible phase is also briefly studied in this thesis, resulting in compressible ELSA formulation that takes into account varying density in each phase. In collaboration with Imperial College London, the Probability Density Function (PDF) formulation with Stochastic Fields is also explored to study atomization. In modern fuel injection systems, quite oftenthe local pressure inside the injector falls below the vapor saturation pressure of the fuel, resulting in cavitation. Cavitation effects the external flow and spray formulation. Thus, a procedure is required to study the phase change as well as jet formulation using a single and consistent numerical setup. A method is developed in this thesis that couples the phase change inside the injector to the external jet atomization. This is achieved using the volume of fluid formulation where the interface is considered between liquid and gas; gas consists of both the vapor and non condensible ambient air
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Canterle, Joseane Ortiz Breitenbach. "Avaliação da tenacidade à fratura do aço API 5L X70 em diferentes meios de etanol". reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2014. http://hdl.handle.net/10183/114982.
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Com a implementação do Programa Nacional do Álcool (Proálcool), Protocolo de Quioto e substituição do MBTE (metil-terci-butil eter) em alguns países nos últimos anos, houve um aumento significativo da produção de etanol. Os dois maiores produtores mundiais de etanol são os Estados Unidos e o Brasil, sendo o etanol oriundo do Milho e da Cana-de-açucar, respectivamente. Transporte por dutos é a forma mais econômica para grandes quantidades, porém, há evidências de que esses dutos de transporte, e também fundo de tanques de armazenamento, possam ser susceptíveis ao fenômeno de corrosão sob tensão quando operam com etanol. Este fenômeno pode ser avaliado, por exemplo, por ensaios de baixa taxa de deformação (BTD) e de tenacidade à fratura, com corpos de prova definidos em normas já conhecidas internacionalmente. Este trabalho tem por objetivo avaliar a susceptibilidade do aço API X70 em diferentes meios de etanol (Etanol combustível simulado (SFGE), Milho e Cana) através de ensaios de mecânica da fratura. Foram preparados corpos de prova pré-trincados do tipo C(T) (Compact Tension), de acordo com a norma ASTM E647-08. A análise dos resultados foi realizada através das equações da mecânica da fratura linear elástica. Nos ensaios de curvas K-R, apesar de somente o etanol de Milho apresentar uma queda de tenacidade, o K de iniciação aparente e as análises fractográficas, confirmam a fragilização do material nos meios etanol SFGE e Milho. Ensaios de baixa taxa de deformação (BTD) interrompidos e os de step loading com carga flutuante também confirmam estes resultados.In recent years, there have been significant increases in ethanol production due to Brazilian Alcohol Program (Proálcool) implementation, Kyoto Protocol and replacement MBTE in some countries. The world’s largest producers of ethanol are United States and Brazil, being produced from Corn and Sugar Cane, correspondingly. Pipeline transportation is the most cost effective in large volumes, although, there are evidences that these pipelines and the bottom of ethanol storage tanks might be susceptible to the stress corrosion cracking phenomenon. This phenomenon can be assessed, for example, by slow strain rate tests (SSRT) and fracture toughness tests, with specimens well defined by international standards. This study aims to evaluate the susceptibility of steel API X70 in different ethanol environment (Simulated fuel-grade ethanol (SFGE), Corn and Sugar Cane) through fracture mechanics specimens. The tests were carried out on pre-cracked C(T) (Compact Tension) specimens, according to ASTM E647-08. The analysis of results was performed using linear elastic fracture mechanics equations. The analysis of K-R curves initially presented a decrease in toughness only in Corn environment, however the K for crack initiation apparent and fractography investigation confirm the material embrittlement in both SFGE and Corn ethanol environments. Tests of the slow strain rate test (SSRT) interrupted and loading step with fluctuating load also confirm these results.
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Abdel, Alim Richard. "Formation of Soft Particles in Drop-in Fuels". Thesis, KTH, Skolan för kemi, bioteknologi och hälsa (CBH), 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-231462.
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As the mission to the decrease global warming and phase out highly pollutingenvironmental practices globally, regulations including Euro 6 and policies generated by theUnited Nations Framework Convention on Climate Change (UNFCCC) are pushing companiesto be more innovative when it comes to their energy sources. These regulations involve manyfactors related to the cleanliness of the fuel and produced emissions, for example, propertiesof the fuels such as sulfur content, ash content, water content, and resulting emission valuesof Carbon dioxide (CO2) and Nitrogen Oxides (NOx). Furthermore, Sweden has set achallenging target of a fossil-fuel-independent vehicle fleet by 2030 and no net greenhousegasemissions by 2050.One way to cut down on the polluting properties in the fuel, as well as weakening thedependence on fossil fuel based fuel includes utilizing higher blending ratios of biofuels in thetransport sector. This transition to biofuels comes with many challenges to the transportindustry due to higher concentrations of these new fuels leads to clogging of the filters in theengine, as well as, internal diesel injector deposits (IDIDs) that produce injector fouling. Thisclogging of the filters leads to lower performance by the engines which leads to higher repairtimes (uptime) and less time on the road to transport goods. The formation of these softparticles at the root of the clogging issue is a pivotal issue because the precise mechanismsbehind their formation are highly unknown. Scania, a leader in the Swedish automotiveindustry, is very interested in figuring out what mechanisms are the most influential in theformation of these particles in the engine. Understanding the key mechanisms would allowScania to make appropriate adjustments to the fuel or the engines to ensure more time onthe road and less maintenance.There are many conditions known to be possible causes of the formation of softparticles in engines such as water content, ash content, and temperature. After generatingsoft particles using a modified accelerated method, particles were analyzed using infraredtechnology (RTX-FTIR) and a Scanning Electric Microscope (SEM-EDX). Many differentexperiments were performed to be able to make a conclusion as to which mechanisms weremost influential including temperature, time, water, air, and oil. The combination of agingbiofuels (B100, B10, HVO) with metals, and water produced the largest amount of particlesfollowed by aging the biofuels with aged oil, metals, and water. Aging the fuels with aged oilincreased particles, meanwhile the addition of water prevented particle production possiblydue to additives. B100 produced the highest amount of particles when aged with Copper, B10with Brass, and HVO with Iron.
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Mujahid, Raqibul I. "Evaporation of liquid fuel droplet". abstract and full text PDF (UNR users only), 2008. http://0-gateway.proquest.com.innopac.library.unr.edu/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:1460767.
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Caraghiaur, Diana. "On drops and turbulence in nuclear fuel assemblies of Boiling Water Reactors". Doctoral thesis, KTH, Reaktorteknologi, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-107115.
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The study aims to develop the understanding of the mechanistic-type approach to quantify drop deposition in nuclear fuel assemblies of Boiling Water Reactors. This includes the effect of spacers. Spacers have a complex geometry to serve their purposes, but optimization of them alone can improve the thermal limit parameters in nuclear fuel assemblies. Thus, a mechanistic model might prove useful to increase the safety of the reactor as well as economic competitiveness of the nuclear power plant. In this thesis, measurement techniques, such as mobile pressure rod and Laser Doppler Velocimetry are developed and tested to provide local data of the flow around spacers. It is shown experimentally that the effect of spacer on the flow differs depending on the placement of the subchannel in the rod bundle. Partly, because the spacer part differs, but also due to a global velocity profile development. Very few studies in the literature indicate this effect. It is shown that single subchannel models using Computational Fluid Dynamics (CFD) can predict the average velocity increase downstream of the spacer; however, they are not capable of calculating the spacer effect on turbulence parameters. The single subchannel CFD model has limited capability to predict the pressure development inside the spacer part, mainly because cross-flows are not taken into consideration. The deposition of drops in annular two-phase flow is still a scientific challenge. Only empirical correlations are used nowadays to quantify this process. Empirical coefficients are needed for each spacer type to calculate the deposition increase due to obstacle. The discussion about the deposition starts with the phenomenological description. The important input parameter, namely drop size, is carefully analysed, and a new correlation is proposed to calculate the mean drop diameter. The correlation is constructed on a larger experimental data base. Lagrangian Particle Tracking model is tested in its capability to calculate deposition. Additionally, a Eulerian-type model is developed and tested. Turbulent parameters of drops are tightly related to the turbulence of the gas phase and the inertia of the drops. Several approaches are discussed about how to calculate the root-mean-square fluctuating velocities of drops. Both, Lagrangian Particle Tracking and the Eulerian-type of models show good capability in calculating the obstacle effect on deposition, providing improvements are made in prediction of drop size. The effect of increased drop concentration plays a large role and it must be taken into consideration if good quantitative approaches are envisaged.QC 20121207
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Broukal, 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.
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Tato práce se zaměřuje na oblast effervescentních sprejů a jejich aplikace na kapalné spalování s důrazem na průmyslové spalovací komory. Oba aspekty – modelování a experiment – jsou řešeny. Práce obsahuje obecný úvod, ve kterém jsou vysvětleny základní jevy rozpadu kapaliny a vířivého spalování a dále je představena effervescentní atomizace. Poté jsou popsány použité experimentální postupy jak pro měření spreje, tak pro měření tepelných toků do stěn při spalování. V následující kapitole jsou popsány numerické modely a jejich podstata je vysvětlena. Jsou zde uvedeny modely pro rozpad spreje, turbulenci a spalování použité během výzkumu. Vlastní výsledky práce jsou uvedeny formou samostatných článků (vydaných nebo přijatých) s dodatečnou částí věnovanou nepublikovaným relevantním výsledkům. Bylo zjištěno, že standardní modely sprejů jsou do jisté míry schopny popsat effervescentní spreje. Nicméně aby bylo možné predikovat plamen kapalného spreje, jsou zapotřebí detailnější modely sprejů, které dokáží přesně zachytit změnu průměrů kapek v radiálním a axiálním směru. Experimentální měření effervescentních sprejů bylo provedeno pomocí navrhnuté metodiky. Výsledky měření byly analyzovány s důrazem na radiální a axiální vývoj průměrů kapek a některé nové jevy byly popsány. Nepřímá úměrnost mezi gas-liquid-ratio a středním průměrem kapek byla potvrzena. Dále by popsán jev, kdy pro různé axiální vzdálenosti které dojde k úplnému převrácení závislosti středního průměru na axiální vzdálenosti. V závěru je uvedeno shrnutí, které rekapituluje hlavní výsledků a závěry. V závěrečných poznámkách je nastíněn možný budoucí postup. Experimentální data pro ověřování budoucích effervescentních modelů jsou poskytnuta.
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Valencia, 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.
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Droplet collisions and coalescence play an important role in the droplet size evolution in
several processes involving sprays. These processes strongly affect the spray characteristics,
making it difficult to control and predict the final droplet size. This thesis has experimentally
quantified the effect of the operating conditions and multi-nozzle atomisation on droplet
coalescence in a full-cone spray. The coalescence mechanisms that lead to droplet collisions
and coalescence in the spray have also been investigated.
This experimental investigation was carried using two-fluid atomising nozzles with external
mixing for low flowrates, model number Mt” XAOOSROSOA from BETE, which produce a
poly-dispersed full-cone spray with an angle of 17-22°. In this work, measurements of the
integrated Sauter mean diameter, across the spray at various positions downstream of the
nozzle, were obtained by means of a laser diffraction instrument from Malvern Instruments
(Malvern 2600C). The measurements were carried out at five different operating conditions
for one-nozzle atomisation, where the principal manipulated variables were the water
flowrates, from 16.7 to 40 ml/min, and air flowrates, from 11.5 to 14.6 l/min. For the twonozzle
atomisation case, two nozzles were pointed towards each other, and the measurements
were carried out at the most favourable operating conditions for coalescence, found in the
single nozzle experiments.
The coalescence mechanisms involved in droplet collisions and coalescence were investigated
from the local values of the droplet size, and droplet mean and fluctuating velocities, which
were measured using a two component phase—Doppler anemometer RSA 3100 from
Aerometrics, Inc. The measurements were carried out for one and two nozzle atomisation, and
the droplet trajectories were studied for the two—nozzle atomisation case.
This work quantitatively confirms that droplet coalescence depends on the operating
conditions used. The most favourable operating conditions for coalescence were found when
the droplets generated were smaller, which corresponded to relatively low water flowrates
(16.7 ml/min) and high air flowrates (14.6 l/min) for this type of nozzle. At these conditions
the greatest size increase (52%) was obtained, the initial droplet size was the smallest (12.6
um), and the estimated droplet number concentration was the highest (6.7x107 m'3). By
contrast, a lower size increase (27%) was obtained when larger droplets were generated, at a
lower air flowrate of 13.1 l/min and a constant water flowrate of 16.7 ml/min. At these
conditions, the initial droplet size was approximately 18 am, and the estimated droplet
number concentration was just half (3.5x107 m’3) that for the most favourable operating
conditions for coalescence.
The results for the two-nozzle atomisation case have quantitatively demonstrated that droplet
coalescence is further increased by pointing two nozzles towards each other. The size increase
observed for the two nozzle atomisation was significantly greater (86%) compared with that
for the single nozzle case (52%). This is the result of an increase in estimated droplet number
concentration, from 6.7x107 m"3 to l.3><108 m‘3, which was achieved using two nozzles.
Coalescence among droplets interacting can be induced by different mechanisms, such as
Brownian motion, shearing flow and turbulence, differential motion by external forces
(gravity or centrifugal forces), aerodynamic and electrical forces, and acoustic fields. The
mechanism of coalescence was found to be mainly the differential velocity between droplets
of different sizes induced by the differential inertia between them, and the differential velocity
associated with the eddying fluid motion or turbulence. This differential velocity allows
droplets to approach each other, collide and coalescence. Droplet number concentration (inter
particle distance) is also an important parameter, as shown by the results for the two-nozzle
case compared with those for one nozzle.
Finally, a more detailed study at the edge of the spray at two different operating conditions,
generating relatively small and large droplets, quantitatively suggested that the greatest size
increase observed in this case for the smaller droplets case was because of both a 50%
increase in the velocities and a 20% increase in droplet number concentration when
generating smaller droplets.
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Varady, Mark Jordan. "Fuel reformation and hydrogen generation in direct droplet impingement reactors". Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/42826.
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Distributed hydrogen generation from liquid hydrocarbon fuels to supply portable fuel cells presents an attractive, high energy density alternative to current battery technology. Traditional unit operation reactor design for hydrogen generation becomes inadequate with decrease in scale because of the unique challenges of size and weight minimization. To address the challenge of reactor scale-down, the concept of multifunctional reactors has emerged, in which synergistic combination of different unit operations is explored to achieve improved performance. The direct droplet impingement reactor (DDIR) studied here is based on this approach in which the liquid feed is atomized using a regularly spaced array of droplet generators with unparalleled control over droplet characteristics, followed by vaporization and reaction directly on the catalyst surface. Considering each droplet generator in the array as a unit cell, a comprehensive, first-principles model of the DDIR has been developed by considering the intimately coupled processes of 1) droplet transport, heating, evaporation, and impingement on the catalyst surface, 2) liquid reagent film formation, capillary penetration, and vaporization within the catalyst layer, and 3) gas phase heat and mass transfer and catalytic reactions. Simulations are performed to investigate the effect of reactor operating parameters on performance. Experimental validation of the model is carried out by visualizing droplet impingement and liquid film accumulation while simultaneously monitoring reaction product composition over a range of operating conditions. Results suggest an optimal unit cell shape for reaction selectivity based on a balance between reagent back diffusion and catalyst bed thermal resistance. Further, achieving a target throughput is best accomplished by adding together a larger number unit cells with optimized geometry and lower throughput (per unit cell) to more effectively spread heat and avoid hotspots at the catalyst interface. At the same time, conditions must be satisfied for ensuring droplet impingement on the catalyst surface, which become more stringent as unit cell throughput is decreased.
20
Harizi, Hedi [Verfasser]. "Full Chip Dynamic Voltage Drop Analysis Using Automated Abstractions of Cell and Block Properties / Hedi Harizi". München : Verlag Dr. Hut, 2010. http://d-nb.info/1009095439/34.
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Shriharsha, Swarga. "Development of a method that quantifies the filtration efficiency of soft particles in drop-in fuels". Thesis, KTH, Skolan för kemi, bioteknologi och hälsa (CBH), 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-261143.
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The global carbon footprint is increasing with course of time. World is moving towards fossil free and reduce the dependency of fossil fuels to meet their daily needs. Transportation industry is the major user of fossil fuels today and major contributor to the CO2 emissions which leads to global warming. Biofuels are promising and sustainable alternative to the fossil fuels. If biofuel is used in its pure form in the vehicles, it asks for engine modifications. Hence, the concept of drop-in fuels are introduced. Drop-in fuels are those fuels in which conventional fossil fuel is blended with biofuel. This blending leads to several advantages like less amount of unburnt hydrocarbons, less toxic and leads to better lubricity of the fuel. On the other hand, in case of blending fossil diesel in biodiesel lead to formation of insoluble organic compounds called as soft particles. These soft particles get accumulated on fuel filter and in turn reduce the amount of fuel entering the engine causing a pressure drop in the flow. This reduction in amount of fuel entering the engine leads to lower engine performance. The study conducted here was successful in developing a method to quantify the soft particles in drop-in fuels where B10 was used as test fuel. The earlier phase of the work comprises literature study on the contaminants in biofuels, working of fuel filters and on some chemical analysis techniques. Literature study is followed by series of experiments that guide through to successfully quantify the soft particles. The earlier stage of experiments included, finding a method to synthesize soft particles in a laboratory scale. This was followed by adding soft particles to fuel and making a synthetic test fluid. Analyzing the filter deposit after filtration helped to quantify the soft particles. The chemical analysis techniques like Gas Chromatography and Mass Spectroscopy (GC/MS) and Fourier Transform Infrared Spectroscopy (FTIR) were used for analysis.Det globala koldioxidavtrycket ökar med tidens gång. Världen rör sig mer mot ökad fossilfrihet och minskat beroende av fossila bränslen för dagliga behov. Transportsektorn är idag den största användaren av fossila bränslen och den största bidragaren till de CO2-utsläpp som leder till global uppvärmning. Biobränslen utgör ett lovande och hållbart alternativ till fossila bränslen. Om biobränslen används i sin rena form i fordonen krävs det att motorerna anpassas. Därför introduceras konceptet drop-in fuels. Drop-in fuels är fossila bränslen som blandats med biobränslen. Dessa bränsleblandningar har flera fördelar, som en minskad mängd oförbrända kolväteföreningar och en minskad toxicitet. Å andra sidan leder blandandet av fossila bränslen och biobränslen till bildandet av olösliga organiska föreningar även kallade mjuka partiklar. Dessa mjuka partiklar ackumuleras i bränslefiltret och leder till ett tryckfall som minskar bränsleflödet in i motorn. Ett minskat inflöde av bränsle till motorn leder till en försämrad motorprestanda. Denna studie ämnar utveckla en metod för att kvantifiera mängden mjuka partiklar i drop-in fuels med en filtreringsteknik. Den första fasen av studien innefattar en litteraturstudie om föroreningar i drop-in fuels, olika filtreringstekniker och några olika analysmetoder. Litteraturstudien följs av en serie experiment som ämnar kvantifiera mängden mjuka partiklar. Den första delen av denna experimentserie ämnade utveckla en metod för att framställa dessa mjuka partiklar. Efterföljande experimentserie innefattade att tillsätta dessa mjuka partiklar till en bränslevätska för att framställa en syntetisk testvätska. Slutligen, genom att filtrera denna testvätska och analysera vätskan före och efter filtret, kan effektiviteten av filtreringsprocessen bestämmas. Analysmetoder som Gaskromatografi och masspektroskopi (GC/MS) och Fourier Transform Infraröd Spektroskopi (FTIR) användes för analysen.
22
Boodoo, Sudesh. "Estimation of drop-size distributions from deconvolved doppler radar data". Thesis, McGill University, 1993. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=69698.
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A 915 MHz Doppler radar was able under certain conditions to provide Doppler spectra containing separate and distinct modes due to scattering by rain and by the clear air. The rain spectra are broadened and shifted on the velocity axis due to turbulent air motions. Information in the clear air mode is used to correct for these effects, leaving in the rain spectra the reflectivity-weighted distribution of drop fall speed, from which the drop-size distribution can be computed.The fast Fourier transform and two iterative methods of deconvolution were applied to simulated Doppler spectra. We concluded that the iterative methods of deconvolution are more appropriate than the fast Fourier transform. Of the two iterative methods, Jansson's method of deconvolution, including prefiltering of the data, was found to give better results than Van Cittert's method.
Jansson's method was applied to biomodal spectra obtained from the HARP project of 1990 in Hawaii and to spectra obtained from a similar radar operated in Montreal. Evident is the different characteristics of rainfall in both regions and the appropriateness of the same deconvolution method to different classes of spectra.
23
Fekete, Denise M. "Pro-drop and verb-second : romance and germanic in Old French". Thesis, McGill University, 1987. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=63760.
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Lee, Gyu Won. "Errors in rain mearurement by radar : effect of variability of drop size distributions". Thesis, McGill University, 2003. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=19509.
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In this work, the various sources of errors in radar rain estimation are quantified and procedures are developed to reduce them. The few topics explored here are: the variability of drop size distributions (DSDs), radar calibration, and errors in polarimetric rain estimation. The findings resulting from this study include 1) a new filtering technique that reduces the spurious DSD sampling variability while maintaining the physical variability, 2) a generalization of previously suggested DSD models in terms of scaling concepts, 3) the experimental evidence of the physical interpretation of DSD evolution and of R-Z relationships, 4) the time scale dependence of the DSD variability and its implication for radar rain estimation, 5) the quantification of error sources in polarimetric rain estimation and its feasibility in operational environment, and 6) a complete set of stable radar calibration methods and their theoretical limits. All error statistics from this work will be used as a guideline in radar rain estimation.
25
Duangsuwan, Wiriya. "Experimental studies of the mixing of alcohols with vegetable oil using gas-liquid compound drops for applications in bio-fuel production". Thesis, University of Surrey, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.521716.
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Lim, Albert Kee Wah. "Non-linear response of reinforced concrete coupling slab with drop panel in earthquake-resisting shear wall structures". Thesis, McGill University, 1989. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=55618.
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Edwards, Kerri. "Greenhouse gas emissions from drip irrigated tomato fields". Thesis, McGill University, 2014. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=123327.
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Irrigation practices change the soil moisture in agricultural fields, and in turn influence the emissions of greenhouse gases. A two year field study was conducted to assess the emissions of CO2, CH4 and N2O from surface drip and subsurface drip irrigated tomato fields in Southwestern Ontario, Canada. Gas fluxes were obtained through the static chamber method, taking samples every 15 minutes over a one hour time period. Soil moisture and soil temperature were measured once per chamber per hour and used to help explain the gas emissions. A peak mean N2O flux at 405 µg N2O-N m-2 h-1 was observed from the five chambers in the surface drip irrigation treatment on July 8th, 2013, shortly following a rainfall event. Most N2O fluxes which occurred during the irrigated portion of the growing season were around 50 µg N2O-N m-2 h-1 in both treatments, water added here was less than some of the large rainfall where peaks occurred. Both the lowest CO2 mean treatment fluxes (12 mg CO2-C m-2 h-1) and highest (12 mg CO2-C m-2 h-1) were observed in the surface drip irrigation plots. Seasonal emissions of CO2 were significantly greater in surface drip plots than subsurface drip plots in 2013, but not in 2012, and this is likely attributed to soil temperature differences. Methane ¬fluxes were mainly negative, indicating that the soil is a sink, as opposed to a source for this gas. Generally, there was no significant difference in soil moisture between the types of drip system. Consequently, there were only a few days which showed significant differences between subsurface drip irrigation and surface drip irrigation treatments for the hourly collected gas fluxes throughout the two growing seasons. Overall, the use of subsurface drip irrigation or surface drip irrigation does not affect the emissions of greenhouse gases from the tomato fields in this study.Les techniques d'irrigation affectent l'humidité du sol dans les terres agricoles, ce qui affecte les émissions de gaz à effets de serre. Une étude sur le terrain d'une durée de deux ans a été menée dans le sud-ouest de l'Ontario au Canada afin de déterminer les émissions de CO2, CH4 et N2O de champs de tomates irrigués au goutte-à-goutte de surface et au goutte-à-goutte souterrain. Les flux de gaz ont été obtenus en prenant des échantillons à chaque 15 minute pour une durée d'une heure, en utilisant la méthode de chambre statique. L'humidité et la température des sols ont été mesurés et utilisés afin d'expliquer les émissions de gaz. La moyenne de flux de N2O a atteint un sommet de 405µg N2O-N m-2 h-1 dans le cas de l'irrigation au goutte-à-goutte de surface, peu de temps après un épisode de pluie. La majorité des flux de N2O qui se sont produits pendant le moment de la saison utilisant de l'irrigation était d'environ 50 µg N2O-N m-2 h-1 dans les deux traitements. La plus faible (12mg CO2-C m-2 h-1) et la plus haute (123mg CO2-C m-2 h-1) moyenne des flux des traitements ont toutes les deux été observées dans les champs irrigués au goutte-à-goutte de surface. Les flux de CH4 étaient principalement négatifs ce qui indiquent que les sols sont des puits, plutôt qu'une source de ce gaz. Une différence significative entre les flux des traitements a été démontrée seulement pour un nombre limité de jour parce que l'humidité des sols créée par les deux systèmes d'irrigation de goutte-à-goutte était similaire. Les émissions saisonnières de CO2 étaient significativement plus hautes dans le cas des champs irrigués au goutte-à-goutte de surface que les champs irrigués au goutte-à-goutte souterrain en 2013, mais pas en 2012, ce qui est probablement dû aux différences dans les températures des sols. Globalement, l'utilisation de l'irrigation au goutte-à-goutte de surface ou de l'irrigation au goutte-à-goutte souterraine n'a pas d'effet majeur sur les émissions de gaz des sols dans les champs de tomates.
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Monette, Liza. "Numerical simulations of nucleation and growth phenomena". Thesis, McGill University, 1987. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=64053.
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Parikh, Anand. "LONG-TERM CRANIAL RECONSTRUCTIONS IN FULL THICKNESS DEFECTS USING CARBONATED CALCIUM PHOSPHATE CEMENT WITH TITANIUM MESH SCAFFOLD IN A SHEEP MODEL: BIOMECHANICAL ANALYSIS". Akron, OH : University of Akron, 2006. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=akron1164993505.
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Thesis (M.S.)--University of Akron, Dept. of Biomedical Engineering, 2006."December, 2006." Title from electronic thesis title page (viewed 06/27/2007) Co-Advisors, Glen O. Njus, Daniel B. Sheffer; Faculty Reader, Mary C. Verstraete; Department Chair, Daniel B. Sheffer; Dean of the College, George K. Haritos; Dean of the Graduate School, George R. Newkome. Includes bibliographical references.
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Mensah, Joel B. [Verfasser], Regina Akademischer Betreuer] Palkovits i Lars Mathias [Akademischer Betreuer] [Blank. "Chemo-catalytic and electrochemical deoxygenation of bio-derivable 3-hydroxydecanoic acid : production of drop-in fuels and fine chemicals / Joel Boakye Mensah ; Regina Palkovits, Lars M. Blank". Aachen : Universitätsbibliothek der RWTH Aachen, 2020. http://d-nb.info/1226303811/34.
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Koziol, Anna S. (Anna Sophia). "The effect of turbulence on the collision rates of small cloud drops". Thesis, McGill University, 1995. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=28802.
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The role of turbulence in the process of collision and coalescence of small cloud droplets is still an outstanding problem in the area of cloud physics. In particular, the growth of droplets in the radius range for 10 to 15 $ mu$m is not well understood. The present research has been motivated by the curiosity whether or not turbulence affects the growth rate of such small drops.We developed a method to calculate collision rates of small hydrodynamically interacting drops embedded in an external flow field; we call it the flux method. Then, the method was tested for simple cases of laminar flows such as linear shear and a two-dimensional deformation field. The tests were designed not only to validate the method but also to examine the mechanisms associated with the simplified types of external flows which may be equally important for real turbulent flows.
In order to obtain estimates of collision rates for turbulent flows, the flux method was used in conjunction with a probabilistic approach. Numerous simulations of trajectories of two hydrodynamically interacting droplets in a turbulent field were carried out. The ratio of the number of collisions to the total number of simulations gave the probability of collision for different relative positions of the drops. Because the Reynolds number of the flow around droplets (based on the drop radius and terminal velocity) is small, the trajectories were calculated with the help of a model based on the linear Stokes hydrodynamics. Turbulence was modelled in the form of random Fourier modes with both the space and the time spectrum prescribed. Both spectra were characterized by Kolmogorov scaling. The space spectrum was modelled in the inertial and dissipation subranges. On the basis of scale analysis, only small scale time variations were allowed, and, the so called Eulerian-Lagrangrian time spectrum was applied.
The results show that most collision rates increase moderately in a turbulent flow characterized by a rate of energy dissipation of the order of 1, 10, and 100 cm$ sp2$ sec$ sp{-3}.$ The estimated increase in collision efficiencies, however, is not uniform, and a rather complicated relation between the increase in the collision efficiency and the parameters--the drop radii, and the rate of energy dissipation--can be observed.
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Cunningham, Mark Huzzard. "Effect of coolant velocity on the fragmentation of single melt drops in water". Thesis, McGill University, 1996. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=27214.
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Flash X-ray and high speed photography were used to experimentally investigate the fragmentation process of single tin drops (0.5 g) in water during a steam explosion. Water velocities ranging from 9 to 28 m/s and a melt temperature of 800$ sp circ$C were used in order to study the effect of the water velocity on the drop fragmentation. Tests were also conducted in which the drop break-up was due entirely to hydrodynamic effects to evaluate the influence of the thermal energy on the fragmentation mechanism.Results showed that there was a transition from thermal to hydrodynamic fragmentation through an intermediate stage in which the drops initially underwent hydrodynamic fragmentation followed by the formation of a vapour bubble. For low velocities (9 m/s) this bubble collapsed, fragmenting the remainder of the drop while at great velocities (15 m/s) the drop broke up within the bubble before it condensed. At 22 and 28 m/s there was no vapour formation and the drop fragmented due to hydrodynamic effects. The total non-dimensional break-up time was 2.0-2.5 for all cases.
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Pilon, Mark J. (Mark Joseph). "A numerical and observational study of bimodal surface raindrop size distributions /". Thesis, McGill University, 1985. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=66028.
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Ciccarelli, Gaby. "Investigation of vapor explosions with single molten metal drops in water using flash X-ray". Thesis, McGill University, 1991. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=39276.
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In the present study, flash x-ray photography as well as high speed regular photography was used to investigate the fragmentation process during the vapor explosion of single drops of molten metal in water. For drops heated to 700$ sp circ$C, a vapor bubble is formed around the drop after a short induction time of about 80 $ mu$s which grows to a maximum diameter and then collapses. X-ray radiographs, which can "see through" the vapor bubble, show that filaments of metal protruding from the drop surface are produced during the bubble growth. At the time of the bubble collapse, the drop surface is highly convoluted and a second interaction is initiated producing an even larger second bubble in the case of tin drops. A mechanism based on nonuniform superheating and evaporation of the water upon unstable film collapse is proposed to describe the origin of the melt filaments. For liquid drops under isothermal conditions with the water, fragmentation occurs as mass is stripped off the surface due to relative motion of the water. For hot drops at higher flow velocities (i.e., $>$45 m/s) initially a vapor bubble forms but it is quickly displaced downstream. It is proposed that evaporation at the upstream surface of the bubble generates a vapor flow around the drop surface which strips the drop surface. The vapor flow carries the fragments into the bubble region behind the drop. The vapor later condenses leaving a cloud of fragments which are subsequently dispersed by the water. The dynamics of the vapor bubble produced by the explosion of a hot drop under low flow conditions is modeled using a parametric model incorporating the Rayleigh equation for bubble dynamics and an energy equation for the vapor to account for added heat transfer from the distorting drop surface. Estimates of the total heat transferred from the drop show that only 3% of the initial drop thermal energy is converted into work done by the vapor bubble.
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Mafuta, Million Trocco. "Design and implementation of an efficient solar powered irrigation management system for drip irrigated maize field". Thesis, University of Strathclyde, 2014. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=24708.
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Purpose - The thesis investigates effects of automatic variation of the deficit irrigation level with the growth stage of drip irrigated maize on grain yield and crop Water Use Efficiency (WUE). It further examines the impact of water-efficient irrigation controllers on the solar Photovoltaic energy level requirements for water pumping systems. Methodology - A Wireless Sensor and Actuator Network was deployed to monitor field conditions and actuate irrigation valves according to whether the level of moisture was within the set points. A Control Treatment (CT) field was fully irrigated using constant moisture threshold levels, while an Experimental Treatment (ExT) field had the highest level of deficit irrigation at the early and later growth stages. Full irrigation was applied at the middle growth stage. Irrigation depths and grain yields were measured, while WUE and the solar energy required by the water pumping system were calculated. Findings - The findings show that 880 mm and 560 mm of water were applied to CT and ExT fields, respectively. This represents a 36% water saving and a corresponding water pumping energy saving of 36% in the ExT field. The grain yields were 0.752 kg/m2 and 0.812 kg/m2 for CT and ExT fields, respectively. This shows that, despite applying a lower amount of water, the ExT improved the grain yield by 7.4%. Furthermore, the results show an increase in WUE from 0.86 kg/m3 for the CT field to 1.45 kg/m3 for the ExT field, representing a 69% improvement. Research limitations/implications - This study focused on the maize production under Malawi's weather conditions. However, the concept would easily be replicated in other crops and in other parts of the world with two modifications: firstly, sensor calibration must be done on-site; and secondly, the specific crop coefficient pattern must be used to develop the irrigation scheduling strategy.
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Kafadar, Cemal 1954. "When coins turned into drops of dew and bankers became robbers of shadows : the boundaries of Ottoman economic imagination at the end of the sixteenth century". Thesis, McGill University, 1986. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=75361.
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Starting from the final decades of the sixteenth century, Ottoman intellectuals were deeply concerned with what they perceived to be the decline of their traditional order. This decline consciousness, which later crystallized into a reform literature, is reflected in the works of this period's major historians.Chapter I surveys the development of Ottoman historiography prior to the late sixteenth century, with the aim of highlighting the novelty of the critical perspectives developed by historians of the era like Ali, Lokman and Selaniki. The attitudes and analyses of these historians concerning disturbing economic processes such as monetary turbulence and price movements constitute the focus of Chapters II and III respectively. These chapters argue that Ottoman decline consciousness grew partly in response to a keen awareness of newly emerging social and economic forces that Ottoman reform literature chose not to understand and accomodate but to resist and suppress. The failure of Ottoman intellectuals to come to terms with the new market forces of the early modern world was not due to an anti-mercantile bias, but to the primacy of politics in the Ottoman order. Chapter IV traces the international commercial activities of Ottoman Muslims in the context of a comparison between Ottoman decline consciousness and European mercantilism.
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Castrillon, Escobar Sebastian. "Instabilité et dispersion de jets de corium liquides : analyse des processus physiques et modélisation dans le logiciel MC3D". Thesis, Université de Lorraine, 2016. http://www.theses.fr/2016LORR0102/document.
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Lors d’un accident grave dans un réacteur nucléaire (REP ou REB en particulier), le combustible fondu (corium) peut se déverser dans le réfrigérant (eau). L’interaction entre les deux fluides est appelée Interaction Combustible-Réfrigérant. Sous certaines conditions, cette interaction peut conduire à une «explosion de vapeur» qui peut menacer le confinement du réacteur nucléaire. L’ICR est une interaction de caractère multiphasique complexe où divers phénomènes physiques interviennent de manières couplées. Elle débute par une phase de mélange entre les fluides (prémélange), se traduisant par la fragmentation du corium et sa dispersion dans le réfrigérant. Ce processus de fragmentation impacte les échanges thermiques (ébullition et mise en mouvement du fluide environnant (réfrigérant)) et les processus chimiques (oxydation du corium et génération d’hydrogène). Cette thèse apporte de nouveaux éléments concernant la compréhension physique et la modélisation du phénomène de fragmentation du corium, dont l’objectif principal est d’améliorer la modélisation dans le logiciel de thermohydraulique multiphasique MC3D, développé par l’IRSN. L’étude proposée se base sur l’hypothèse de la modélisation de la fragmentation comme un phénomène multi-échelle avec un découplage entre taux de fragmentation du jet et dimension des gouttes résultantes. Elle suppose un processus de fragmentation qui est le résultat d’une déstabilisation primaire (passage jet -> grosses gouttes) pilotée par les grandes échelles de l’écoulement et d’un processus de déstabilisation secondaire menant à une fragmentation finale dépendante des paramètres plus «locaux» de l’écoulement. Nous avons conjugué notre modélisation avec une méthode de type MUSIG récemment introduite dans le logiciel MC3D. Les gouttes de corium y sont représentées, via un découpage en classes, par plusieurs champs de masse et d’énergie avec des diamètres distincts. Malgré les avancées dans la modélisation de la fragmentation, la compréhension des mécanismes et la caractérisation de la fragmentation des gouttes liquides est encore très imparfaite, particulièrement dans le cas liquide/liquide. Le travail de thèse s’est alors orienté vers l’analyse de ce processus en utilisant le logiciel de simulation GERRIS. L’étude conduit à proposer une nouvelle carte de régimes de fragmentation en configuration liquide/liquide, une compréhension plus approfondie de la dynamique de fragmentation et une analyse sur l’interaction vortex-goutte pilotant la transition entre les régimesIn the case of a severe accident in a nuclear power plant, the molten core may flow into water and interact with it. The consequences of this fuel-coolant interaction (FCI) for the follow-up of the accident may be numerous so the phenomenon needs to be described accurately, one of them called “steam explosion” can lead to the failure of the nuclear reactor containment. FCI is a complex multiphase interaction involving several physical phenomena. The premixing phase of the interaction consists in the fragmentation and dispersion of corium in the coolant pool. This phase is driven by the fragmentation process which modifies heat transfers (coolant boiling dynamics) and chemical reactions (corium oxidation and hydrogen generation). This thesis brings new elements about the corium jet and droplet breakup with the main goal of improve fragmentation models on the MC3D multiphase code, developed by the IRSN. Our study is based on a multi-scale fragmentation process where the jet fragmentation rate and final droplet dimensions are not coupled themselves. We suppose a fragmentation process resulting from a primary instability (mass transfer within jet and big droplets) depending on the large flow scales and a secondary instability depending on the small flow scales (leading to final droplet breakup). This model has been implemented in MC3D in combination with the MUSIG method recently added to MC3D. In this method, droplets are represented using several classes, each of them with their own droplet diameter, mass and energy fields. Despite new improvements on modeling corium fragmentation, there is still a lack on the comprehension and characterization on the liquid droplet fragmentation, particularly on liquid/liquid configurations. In this thesis, we study in detail droplet breakup using the computational fluid dynamics software GERRIS. As a result, we find a new droplet breakup classification in liquid/liquid configurations, we improve the droplet breakup dynamics comprehension and we analyze the droplet-vortex interaction to determine breakup regime transition
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Akshay, S. "Fuel Drop Splashing on Heated Solid Surfaces". Thesis, 2021. https://etd.iisc.ac.in/handle/2005/5118.
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Droplet-wall interactions on heated surfaces are significantly encountered in applications such as fuel spray impingement in combustors and spray cooling. The present thesis is focused on the splashing of fuel drops on heated solid surfaces and aims to understand the effect of surface temperature in altering the morphology of splash outcome. High-speed imaging is employed as part of the experimental investigation to understand the regimes of splashing impact by varying the impact Weber number (We) and surface temperature (T_S), for the three test fuels (ethanol, n-butanol, diesel) considered. Splash focused experiments conducted at constant We and increasing T_S from ambient to below the Leidenfrost point of respective fuel, reveal that the effect of surface temperature is to suppress corona splashing, as evidenced by the shift of impact morphology from thin-sheet corona splashing to pure spreading via a transition regime. Splash threshold experiments are also conducted to estimate the threshold We for different T_S , which further show that the threshold We increases with the surface temperature for all fuels considered. It is reasoned that the variation of gas viscous stresses or a reduction in the localized gas phase density close to the heated surface could be responsible for the observed transitions.
The experimental data from the threshold and constant We experiments are correlated with corresponding theoretical predictions of splash threshold parameters reported by Xu et al. (2005) and Riboux and Gordillo (2014), by incorporating the temperature parameter into these models. The analytical predictions so derived also point towards the experimentally observed suppression effect. The transition regime is characterized by the tendency of the ejected liquid sheet to re-contact the spreading lamella and is quantified in terms of the re-contact time and the transition surface temperatures, experimentally. Interestingly, the experimental transition surface temperature data between splashing and re-contacting regimes match fairly well with the predictions made using the air film instability model proposed by Liu et al. (2015). The so derived comparisons hint at the role of low wavelength Kelvin - Helmholtz instabilities acting in the thin gas layer close to the surface in altering the splash outcome with surface temperature.
To gain further insights into the actual mechanisms responsible for the observed splash suppression with temperature, direct numerical simulations are carried out using Basilisk, to ascertain how much the variations in the density and viscosity ratios of the two phases with temperature, contribute to the observed splash outcomes. Variation of density ratio with gas phase temperature reduces the spatial growth of the liquid sheet. Variation of the gas phase viscosity with temperature through Sutherland’s law delays the liquid-solid contact and hence aids in splash suppression. The direct numerical simulations carried out thus hint at possible roles of gas phase density and viscosity variations in altering the thin sheet behavior, and thereby the overall splash outcome.
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Shih, Yu-Cheng, i 石育政. "Combustion Applications of Fuel Oil Additives and Liquid Drop-Jet Collisions". Thesis, 2003. http://ndltd.ncl.edu.tw/handle/63180139210880611204.
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碩士國立成功大學
機械工程學系碩博士班
91
A multi-functional multi-fuel industrial furnace simulator was utilized to study the burning characteristics and pollutant emissions of fuel oils containing various additives. Three specimens were tested. The first was light-oil-added fuel oil, which burned well and could reduce the emission of SOX and NOX. The second was water-emulsified fuel oil, which decreased the burning intensity and reduced SOX emission. For NOX reduction, the amount of water added had to be over 10%. The third was fuel oil with trace additives. Some additives could intensify burning. Some showed reduction in NOX. But none of them changed SOX emission. For drop-jet collision experiment, we utilized a piezo-electric drop generator to produce a stream of uniform droplets, which was directed to collide with a liquid jet of the same diameter as the drop. The dimensionless parameters governing the collision phenomena are the jet-axial Weber number, the jet-cross-sectional Weber number, and the impact parameter. We have discovered four types of collision outcome: (a) Segmenting coalescence-this happens at high jet-cross-sectional Weber number, low jet-axial Weber number. (b) Clinging coalescence-this happens at low jet-cross-sectional Weber number, high jet-axial Weber situation. (c) Stretching separation-this happens at high impact parameters. (d) Reflecting separation-only occurs at low impact parameters and a specific jet-axial Weber number range.
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Bhat, Maanasa. "Experimental Investigation of Fuel Drop Impact on Unheated and Heated Solid". Thesis, 2018. https://etd.iisc.ac.in/handle/2005/4720.
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The modelling of spray-wall interaction encountered in engine combustors relies heavily on studies of single drop impact on heated solid surfaces. In the present thesis, the impact of a single fuel drop on a hot, smooth stainless-steel surface is experimentally examined using high speed visualization. Four different fuels of significantly varying physical properties (heptane, decane, Jet A-1 and diesel) are considered. The condition of impacting fuel drop, characterized in terms of Weber number (We), is varied in the range 27-903. The temperature of the solid surface (Ts) is varied in the range 25-410 oC encompassing all heat transfer regimes from convection to film boiling. The analysis of fuel drop impact on an unheated surface (Ts = 25 oC) reveals that the lamella spreads sluggishly even beyond the end-point of the inertia driven primary spreading phase. This new phase of fuel impact dynamics is termed in the present study as ‘post-spreading’. The spreading rate of the fuel drops in the post-spreading phase is dependent on We and is much lower than that dictated by Tanner’s Law for spontaneous drop spreading. For the impact of fuel drops on hot stainless-steel surfaces, regime maps with We on the X-axis and Ts on the Y-axis, highlighting various heat transfer regimes and morphological outcomes are constructed. Quantitative trends on the variation of maximum spread factor (max) for the fuel drops on the hot surface are presented. With the help of existing theoretical models for predicting max, it is concluded that viscosity of the fuel plays a major role in the determination of temperature dependency of βmax. For drop impact in film evaporation regime, an empirical model for max involving an explicit surface temperature term in the form of normalized value T* is formulated from the experimental data and is found to agree well with similar data from literature. Further details of fuel drop impact dynamics on the hot surface in other heat transfer regimes including contact boiling and Leidenfrost regimes are presented.
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Liang, Jason Jian. "Design and Development of an Experimental Apparatus to Study Jet Fuel Coking in Small Gas Turbine Fuel Nozzles". Thesis, 2013. http://hdl.handle.net/1807/43080.
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An experimental apparatus was designed and built to study the thermal autoxidative carbon deposition, or coking, in the fuel injection nozzles of small gas turbine engines. The apparatus is a simplified representation of an aircraft fuel system, consisting of a preheating section and a test section, which is a passage that simulates the geometry, temperatures, pressures and flow rates seen by the fuel injection nozzles. Preliminary experiments were performed to verify the functionality of the apparatus. Pressure drop across the test section was measured throughout the experiments to monitor deposit buildup, and an effective reduction in test section diameter due to deposit blockage was calculated. The preliminary experiments showed that the pressure drop increased more significantly for higher test section temperatures, and that pressure drop measurement is an effective method of monitoring and quantifying deposit buildup.
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Pacheco, Gonçalo de Sousa Pina Pernicha. "Single droplet ignition and combustion of jet-A1, hydroprocessed vegetable oil and their blends in a drop tube furnace". Master's thesis, 2019. http://hdl.handle.net/10400.6/10388.
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The environmental impact and the dependence of fossil fuels in the aeronautical sector have
promoted the demand for alternative and greener fuels. This is one of the main challenges for
this sector in the near future. A possible solution in the near future might be the blending of
biofuels with jet fuel, which would allow the use of greener fuels, and a reduction in the
greenhouse gases and emissions without significant changes in the existing fleets of the
companies, which means the development of a “drop in” fuel. In this context, this work
examines the ignition and the combustion characteristics of single droplets of jet-A1 (JF),
hydroprocessed vegetable oil (NExBTL) and their mixtures in a drop tube furnace (DTF). The
objective of this work is to evaluate the influence of the fuel mixture composition on the fuel
characteristics. Droplets with diameters of 155 ± 5 µm, produced by a commercial droplet
generator, were injected into the DTF, whose wall temperature and oxygen concentration were
controlled. Experiments were conducted for three temperatures (900, 1000 and 1100 ºC). The
ignition and combustion of the droplets were evaluated through the images obtained with a
high-speed camera coupled with a high magnification lens, and an edge detection algorithm.
The images allowed for the observation of the burning phenomena, and data are reported for
temporal evolution of droplet sizes and burning rates. The results revealed that the fuel
mixtures followed the ??
2
law, except the mixture with 75% JF for a DTF wall temperature of
1100 ºC. This was due to the occurrence of puffing and micro explosions, which enhanced the
burning rates. In addition, it was observed that the mixtures with a higher content of JF present
brighter flames, and higher burning rates.O impacto ambiental e a dependência de combustíveis fósseis no setor aeronáutico promoveram a procura por combustíveis alternativos e ecológicos. Este é um dos principais desafios para este setor no futuro. Uma possível solução num futuro próximo pode ser a mistura de biocombustíveis com combustível de aviação, o que permitiria o uso de combustível mais ecológico e a redução de gases de efeito estufa e emissões sem alterações significativas nas frotas existentes das empresas, isto é, o desenvolvimento de um combustível “drop-in”. Neste contexto, este trabalho examina as características de ignição e combustão de gotas isoladas de jet-A1 (JF), óleo vegetal hidroprocessado (NExBTL) e suas misturas num forno de queda livre (DTF). O objetivo deste trabalho é avaliar a influência da composição da mistura nas características do combustível. Gotas com diâmetros de 155 ± 5 µm, produzidas por um gerador comercial de gotas, foram injetadas no DTF, cuja temperatura da parede e concentração de oxigênio eram controladas. Os testes foram conduzidos para três temperaturas (900, 1000 e 1100 ºC). A ignição e a combustão das gotículas foram avaliadas através das imagens obtidas com uma câmara de alta velocidade acoplada a uma lente de alta ampliação e um algoritmo de deteção de limites. As imagens permitiram a observação dos fenómenos de queima e avaliar a evolução temporal do tamanho das gotas e das taxas de queima. Os resultados revelaram que as misturas de combustível seguem a lei D2 , exceto a mistura com 75% de JF para uma temperatura de 1100 ºC na parede do DTF. Isso ocorreu devido à ocorrência de puffing e microexplosões, o que aumentou as taxas de queima. Observou-se ainda que as misturas com maior teor de JF apresentam chamas com maior intensidade luminosa e maiores taxas de queima.