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The thesis deals with experimental research of mechanism of liquid breakup at twin-fluid atomizers. Four different atomizers were examined at the beginning of the research. Two of them were of standard design (Y-jet and effervescent nozzles), and the rest two atomizers were developed as a part of the thesis (so called CFT and inversed effervescent atomizers). Results show that only the inversed effervescent atomizer was capable of generating stable spray under examined conditions due to the specific breakup mechanism. This mechanism is similar to what was observed in effervescent atomizers. However, the mixing process inside the inversed effervescent atomizer is very different. The specific breakup mechanism was then defined as the main scope of the thesis. It was investigated by the high-speed imaging. The images were then processed by proper orthogonal decomposition and by fast Fourier transformation. Spray spatial development was examined using phase Doppler anemometer. The data was analyzed to describe the dynamics of the spray. A detailed description of the breakup mechanism is made from the combination of the experimental and post-processing techniques. The thesis brings new insight into the understanding of the liquid breakup mechanism and shows a potential for a further development of the inversed effervescent atomizer.

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The focus of this Ph.D. thesis research is a new piezoelectrically driven micromachined ultrasonic atomizer concept that utilizes fluid cavity resonances in the 15 MHz range along with acoustic wave focusing to generate the pressure gradient required for droplet or jet ejection. This ejection technique exhibits low-power operation while addressing the key challenges associated with other atomization technologies including production of sub-5 um diameter droplets, low-temperature operation, the capacity to scale throughput up or down, and simple, low-cost fabrication. This thesis research includes device development and fabrication as well as experimental characterization and theoretical modeling of the acoustics and fluid mechanics underlying device operation. The main goal is to gain an understanding of the fundamental physics of these processes in order to achieve optimal design and controlled operation of the atomizer. Simulations of the acoustic response of the system for various device geometries and different ejection fluid properties predict the resonant frequencies of the device and confirm that pressure field focusing occurs. High-spatial-resolution stroboscopic visualization of fluid ejection under various operating conditions is used to investigate whether the proposed atomizer is capable of operating in either the discrete-droplet or continuous-jet mode. The results of the visualization experiments combined with a scaling analysis provide a basic understanding of the physics governing the ejection process and allow for the establishment of simple scaling laws that prescribe the mode (e.g., discrete-droplet vs. continuous-jet) of ejection. In parallel, a detailed computational fluid dynamics (CFD) analysis of the fluid interface evolution and droplet formation and transport during the ejection process provides in-depth insight into the physics of the ejection process and determines the limits of validity of the scaling laws. These characterization efforts performed in concert with device development lead to the optimal device design. The unique advantages enabled by the developed micromachined ultrasonic atomizer are illustrated for challenging fluid atomization examples from a variety of applications ranging from fuel processing on small scales to ultra-soft electrospray ionization of biomolecules for bioanalytical mass spectrometry.

EN The present diploma thesis deals with the electrochemical generation of volatile tellurium compounds in connection with atomic absorption spectrometry with the main goal to increase the response of the tellurium signals and thus expand the existing knowledge about this element. Tellurium is one of the heavier elements that forms less stable volatile compounds. The reason for choosing these elements was the fact that its concentration increases mainly in landfills where it is released into the environment, which can have an ecological impact and an impact on human health. In the first step, two types of electrochemical cells were constructed - a thin-film flow electrochemical cell with and without an ion exchange membrane and an apparatus with a flow injection arrangement. The choice of cell types, cathode and anode material and apparatus design was chosen based on a literature research. Attention was paid to the optimization of reaction conditions for electrochemical generation of volatile tellurium compounds, which significantly affect the efficiency of generation using a heated quartz tube atomizer. The optimized parameters were electrolyte concentration, carrier gas volume flow rate, electrolyte volume flow rate and generation current. In the second step, the effect of the temperature of the...

The aim of the diploma thesis was an improvement of the efficiency of electrochemical generation of volatile form of cadmium used in atomic spectrometric methods. The increase of the efficiency of electrochemical generation of volatile form results in overall improvement of the sensitivity of measurement and therefore, it is possible to achieve lower values of detection limits and limits of determination. One of all the possibilities for improving of overall efficiency is a minimization of loss of volatile form of Cd during transport. Another essential possibility is coupling of the technique of electrochemical generation of volatile form of Cd with in-situ collection (and atomization) in graphite furnace of atomic absorption spectrometer. Keywords: Atomic absorption spectrometry, electrochemical generation of volatile compounds, generation efficiency, electrolytic flow-through generation cell, quartz-tube atomizer, graphite furnace, in-situ trapping, cadmium

L’objectif de ce travail est de concevoir un outil d’atomisation adapté à la production de poudres de carburede tungstène dans l’entreprise Technogenia, située à Saint-Jorioz (74). Plus généralement, nous avons étudiéune nouvelle conception d’atomiseur rotatif pour lequel les surfaces d’atomisation sont orientées selon un angled’incidence non nul. Une telle orientation permet alors d’exploiter de façon plus efficace la fréquence de rotationde l’atomiseur ainsi que les forces de centrifugation et de Coriolis. A partir de cette base de réflexion, troisgéométries de surface d’atomisation ont été étudiées : des surfaces lisses, des surfaces pourvues de structurationsde long de leur bord de fuite et des surfaces matricées de perforations.Les différents modes de déstabilisation des écoulements liquides ont été observés grâce à l’acquisition de vidéosultra-rapides des différentes étapes de l’impact d’une goutte unique sur les différentes géométries de surfacesd’atomisation étudiées. Les processus d’atomisation peuvent ainsi varier entre la rupture de jets liquides régulierscausée par des instabilités de type Rayleigh-Plateau et la rupture de nappes liquides causée par des instabilitésde type Rayleigh-Taylor et/ou l’initiation de perforations au coeur des nappes et films liquides. Les vidéos dessprays aqueux ainsi que l’observation au microscope des poudres métalliques nous permettent de caractériser lessprays produits. Sur l’ensemble de nos expériences nous observons que la finesse de l’atomisation s’améliore àmesure que la fréquence de rotation augmente ; ce qui constitue l’objectif prioritaire du procédé développé dans lathèse. Cependant, les surfaces texturées, certes compatibles avec les liquides classiques (aqueux ou organiques),ne le sont plus avec les contraintes induites par du métal à haute température de fusion, tel le carbure detungstène fondu objet de la thèse. En conséquence, seules les surfaces lisses sont aujourd’hui retenues et fontl’objet de développements dans le cadre de la production de poudres métalliques au sein de Technogenia. / The aim of this work is to design a spray tool for the production of tungsten carbide powder for the companyTechnogenia, located in Saint-Jorioz (74). Thus, we have studied a new design of rotary atomizer based onatomization surface oriented at a non-zero incidence angle. Such an orientation can then allow to use moreeffectively the rotation frequency of the atomizer and the centrifugal and Coriolis forces. From this base reflection,three geometries of atomization surface were studied : smooth surfaces, surfaces with serrated structurationsalong their trailing edge and multi-perforated surfaces.The different destabilization modes of liquid flows were observed through high-speed videos of the different stagesof the single drop impact on each atomization surfaces. The atomization process can thus vary between liquid jetbreakup caused by Rayleigh-Plateau instabilities and liquid sheet breakup caused by Rayleigh-Taylor instabilitiesand/or initiating of holes in liquid films or sheets. Videos of aqueous sprays and microscopic observation of metalpowders allow us to characterize sprays. On all of our experiments, we observe that the atomisation gets better(producing finer spray), as the frequency of rotation increases. Although the textured surfaces are compatiblewith usual liquids (aqueous or organical), they can’t stand the constraints imposed by metal with a high meltingtemperature such as tungsten carbide, the object of this thesis. Therefore, only the smooth surfaces are nowthe subject of an industrial development to produce metallic powder with Technogenia company.

Made available in DSpace on 2014-12-17T14:08:43Z (GMT). No. of bitstreams: 1 AluisioAN_DISSERT.pdf: 2010955 bytes, checksum: 9d4c76c749552efd65c7156a389b51c8 (MD5) Previous issue date: 2010-11-19 / Universidade Federal do Rio Grande do Norte / Biomass is considered the largest renewable energy source that can be used in an environmentally sustainable. From the pyrolysis of biomass is possible to obtain products with higher energy density and better use properties. The liquid resultant of this process is traditionally called bio-oil. The use of infrared burners in industrial applications has many advantages in terms of technical-operational, for example, uniformity in the heat supply in the form of radiation and convection, with a greater control of emissions due to the passage of exhaust gases through a macroporous ceramic bed. This paper presents a commercial infrared burner adapted with an ejector proposed able to burn a hybrid configuration of liquefied petroleum gas (LPG) and bio-oil diluted. The dilution of bio-oil with absolute ethanol aimed to decrease the viscosity of the fluid, and improving the stability and atomization. It was introduced a temperature controller with thermocouple modulating two stages (low heat / high heat), and solenoid valves for fuels supply. The infrared burner has been tested, being the diluted bio-oil atomized, and evaluated its performance by conducting energy balance. The method of thermodynamic analysis to estimate the load was used an aluminum plate located at the exit of combustion gases and the distribution of temperatures measured by thermocouples. The dilution reduced the viscosity of the bio-oil in 75.4% and increased by 11% the lower heating value (LHV) of the same, providing a stable combustion to the burner through the atomizing with compressed air and burns combined with LPG. Injecting the hybrid fuel there was increase in the heat transfer from the plate to the environment in 21.6% and gain useful benefit of 26.7%, due to the improved in the efficiency of the 1st Law of Thermodynamics of infrared burner / A biomassa ? considerada a maior fonte renov?vel de energia, podendo ser usada de forma ambientalmente sustent?vel. A partir da pir?lise da biomassa ? poss?vel a obten??o de produtos com maior densidade energ?tica e propriedades de uso melhores. O l?quido resultante do seu processo ? tradicionalmente chamado de bio-?leo. A utiliza??o de queimadores infravermelhos em aplica??es industriais apresenta muitas vantagens do ponto de vista t?cnico-operacional, como por exemplo, homogeneidade no fornecimento de calor, na forma de radia??o e convec??o, apresentando um maior controle das emiss?es devido ? passagem dos gases de exaust?o atrav?s de um leito cer?mico macroporoso. O presente trabalho apresenta um queimador infravermelho comercial adaptado com um ejetor proposto capaz de queimar numa configura??o h?brida de g?s liquefeito de petr?leo (GLP) e bio-?leo dilu?do. A dilui??o do bio-?leo com ?lcool et?lico absoluto teve como principal objetivo diminuir a viscosidade do fluido, e melhorar a estabilidade e a atomiza??o. Foi introduzido um controlador de temperatura com termopar modulando dois est?gios (fogo baixo/alto), e eletrov?lvulas para alimenta??o dos combust?veis. O queimador infravermelho foi submetido a testes e ensaios, sendo atomizado o bio-?leo dilu?do, e avaliado o seu desempenho mediante a realiza??o de balan?o de energia. Como m?todo de an?lise termodin?mica para estimativa de carga foi utilizado uma placa de alum?nio localizada na sa?da dos gases de combust?o, sendo a distribui??o de temperaturas medida por termopares. A dilui??o reduziu a viscosidade do bio-?leo em 75,4% e aumentou em 11% o poder calor?fico inferior do mesmo, propiciando ao queimador uma combust?o est?vel atrav?s da atomiza??o com o ar comprimido e queima conjunta com GLP. Injetando o combust?vel h?brido houve aumento na transfer?ncia de calor da placa para o meio ambiente em 21,6% e ganho energ?tico ?til de 26,7%, em fun??o da melhora na efici?ncia da 1? Lei da Termodin?mica do queimador infravermelho

Made available in DSpace on 2014-06-11T19:25:18Z (GMT). No. of bitstreams: 0 Previous issue date: 2010-06-30Bitstream added on 2014-06-13T18:53:11Z : No. of bitstreams: 1 alandiaroman_ra_me_jabo.pdf: 1589169 bytes, checksum: ec84315ef69508575519f6e0e74d4440 (MD5) / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Objetivou-se avaliar a características do tamanho de gota, a distribuição volumétrica, cobertura e deposição por bicos de energia centrífuga e hidráulica, assim como o controle do bicudo-do-algodoeiro e produtividade da cultura do algodão. No Laboratório de Análises do Tamanho de Partículas, com utilização de um medidor de gotas por difração a luz laser, foram realizadas todas as avaliações referentes ao tamanho de gota de todos os experimentos. Na primeira avaliação referente ao tamanho de gotas foi utilizado delineamento inteiramente casualizado com as seguintes variáveis: três dosadores (0,068; 0,129 e 0,181 L.min-1) três rotações (1780, 2760 e 3610 rpm) e duas caldas (água e água com adição de éster metílico) formando um arranjo fatorial 3x3x2 com três repetições. Os mesmos tratamentos foram utilizados para a realização do estudo da distribuição volumétrica. O segundo experimento realizado no laboratório foi com esquema fatorial 3x4+1, sendo três modelos de bicos (TT11001, XR11001 e ECOS), quatro caldas (endosulfan, endosulfan + óleo vegetal, endosulfan + óleo mineral e endosulfan + nonilfenol) com três repetições. Para o terceiro experimento foi utilizado o esquema fatorial 2x2+2, sendo dois modelos de bicos rotativos (Turbotrator e ECOS), duas caldas (endosulfan e endosulfan + óleo vegetal) e duas testemunhas (Com e sem aplicação). Os tratamentos utilizados no segundo e terceiro experimento foram aplicados a campo na UNESP, Câmpus de Jaboticabal-SP, nas safras 2008/2009 e 2009/2010. Foi avaliada a cobertura pelas gotas aspergidas com utilização de papéis hidrossensíveis; a deposição por meio da extração do marcador manganês em espectrofotômetro de absorção atômica; o controle do bicudo-do-algodoeiro e a produtividade da cultura do algodão. De acordo com os resultados pode-se concluir que os bicos de energia centrífuga... / The aim of this work was to evaluate the characteristics of the droplet size, distribution volume, coverage and deposition by centrifugal and hydraulic energy nozzles as well as control of the boll weevil and productivity of cotton. In the Laboratory of Particle Size Analysis, using a meter drops by laser light diffraction were carried out all assessments relating to the droplet size for all experiments. In the first evaluation regarding the droplet size was used a randomized design with the following variables: three feeders (0.068, 0.129 and 0.181 L.min-1) three rotations (1780, 2760 and 3610 rpm) and two spay liquids (water and water with addition of methyl ester) to form a 3x3x2 factorial design with three replications. The same treatments were used for the study of the distribution volume. The second experiment was conducted in the laboratory with 3x4 +1, three types of nozzles (TT11001, XR11001 and ECOS), four spray liquids (endosulfan, endosulfan + vegetable oil, endosulfan + mineral oil and endosulfan + nonylphenol) with three replications. For the third experiment we used a factorial 2x2+2, two models of spinning disc atomizerss (Turbotrator and ECOS), two spray liquids (endosulfan + endosulfan and vegetable oil) and two controls (With and without spray). The treatments in the second and third experiment were applied to field level at UNESP in Jaboticabal-SP, harvests in 2008/2009 and 2009/2010. Were evaluated the coverage by droplets sprayed with use of hidrossensitive papers; vi deposition by extracting the marker manganese in atomic absorption spectrophotometer; the control of the boll weevil and productivity of cotton. According to the results we can conclude that the centrifugal energy nozzles are more uniform droplet spectrum consequently less risk of drift when compared to hydraulic energy nozzles. Factors such as speed, flow and addition of adjuvant to interfere ... (Complete abstract click electronic access below)