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1
Suchánek, Petr. "Zkoušky rozprašovacích hlav kapalných paliv." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2010. http://www.nusl.cz/ntk/nusl-229069.
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This thesis is dealing with testing of two atomizers in combustion of liquid fuels and natural gas. There is a simple analysis of problems, principles and methods of atomizing liquids executed. Problem of pneumatic atomizing liquids is also described in detail. In the next chapters there is a plan and running of testing processed. Overall behavior of the atomizers and flame is evaluated from the outcome measurement and the power characteristics of atomizers and influence of GLR on the quality of combustion are determined. Overall rating of the testing is presented in conclusion this thesis.
2
Katskov, DA. "Graphite filter atomizer in atomic absorption spectrometry." Elsevier, 2006. http://encore.tut.ac.za/iii/cpro/DigitalItemViewPage.external?sp=1000798.
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Graphite filter atomizers (GFA) for electrothermal atomic absorption spectrometry (ETAAS) show substantial advantages over commonly
employed electrothermal vaporizers and atomizers, tube and platform furnaces, for direct determination of high and medium volatility elements in
matrices associated with strong spectral and chemical interferences. Two factors provide lower limits of detection and shorter determination cycles
with the GFA: the vaporization area in the GFA is separated from the absorption volume by a porous graphite partition; the sample is distributed
over a large surface of a collector in the vaporization area. These factors convert the GFA into an efficient chemical reactor. The research
concerning the GFA concept, technique and analytical methodology, carried out mainly in the author's laboratory in Russia and South Africa, is
reviewed. Examples of analytical applications of the GFA in AAS for analysis of organic liquids and slurries, bio-samples and food products are
given. Future prospects for the GFA are discussed in connection with analyses by fast multi-element AAS.
3
Chinn, John Joss. "The internal flow physics of swirl atomizer nozzles." Thesis, University of Manchester, 1996. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.488302.
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The internal flow of pressure swirl atomizers is studied with the ultimate aim of developing a design tool for such atomizers, particularly to enable the production of the finest possible water sprays (for any given supply pressure) for fire suppression purposes. The primary direction of the research was in computationally modelling this flow with a two-dimensional assumption and a methodology is described which is capable of determining the velocity profiles and, for the first time in the literature, the air-core topology and discharge coefficient, for nozzles which approximate the axially-symmetric condition. The results are compared with the experimental results from both the literature and also from research which was carried out under the supervision of the author. The predictions show important flow features, which are found in the experiments and have not been recognised in the "classically" assumed internal flow. These include concentration of the axial flow near the air-core and toroidal vortices, similar to Taylor-Göertler vortices found in Taylor-Couette flow, which are visible in planes through the nozzle axis. The secondary direction of the research is in both reviewing and improving upon simplified analytical techniques which have been used to estimate the size of the air-core radius at the nozzle exit together with the values of the discharge coefficient and the cone angle of the resultant spray. A critical review is given of many of the existing analytical techniques and a new analytical theory is presented which is based upon a balance of the axial momentum across a control volume. The results of the new theory are compared with the experimental findings reported in the literature and show the need to include the swirl chamber/nozzle orifice ratio as an independent variable. Suggestions are given on how the computational methodology might be employed to determine the spray drop size for a given atomizer design and on the direction the computational work might take in order to predict a full two-phase internal flow using volume of fluid (VOF) techniques.
4
Phanphanit, Phattharawdee. "Experimental and computational study of an ultrasonic atomizer." Thesis, University of Manchester, 2011. https://www.research.manchester.ac.uk/portal/en/theses/experimental-and-computational-study-of-an-ultrasonic-atomizer(f4cb285b-c847-4b15-bd0c-64fa1bd142ce).html.
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A fountain type ultrasonic atomizer was chosen to be a possible device to be used to assist in the alleviation of global warming. Atomization of seawater by an ultrasonic atomizer will enhance more cloud condensation nuclei; as a result, more UV radiation will be reflected back into the space. There are two crucial spray characters: droplet size and the number of droplets. The droplet size needs to be in a certain size range, so that they can stay in the atmosphere. The number of droplets needs to be as high as possible; the more cloud nuclei, the more UV radiation is reflected. The characteristics of sprays are affected by many parameters: liquid properties and the atomizer design. In this study, we characterized two different atomizers: one with a fixed frequency atomizer at 1.72 MHz and one with adjustable frequency and voltage atomizer with a calculated resonant frequency of 2.24 MHz. In addition for the fixed atomizer, different liquid media: tap water (20° C), hot water (46° C), cold water (14° C) and salt waters with different percents salinity (2% - 3.5% by volume), were studied. A Phase Doppler Anemometer was used to measure the characteristics of sprays: droplet velocity, droplet size and number of droplets in a required size range. It was found that the droplet velocity is barely affected by the liquid properties and liquid depth except for the hot water. The relatively high temperature liquid appears to alter the characteristics of the piezo disk; in addition, the inconsistent temperature could vary the characteristics of the spray. The droplet size is strongly dependent on liquid properties and frequency of vibration. The number of droplets is obviously affected by liquid properties and atomizer designs; there is not yet a known correlation between the number of droplets and other parameters. A theoretical study was undertaken in order to compare predicted acoustic properties of acoustic waves with the measured number of droplets generated. The mathematical model was constructed based on applying boundary conditions to a general 2- Dimensional wave equation in cylindrical coordinates. The predicted results satisfy the boundary conditions very well. Since we deal with high frequency acoustic waves, the number of wave modes used in the prediction is significant. It is important to be ensure that all the cut-on wave modes are included otherwise the predicted results will not be very accurate. The more modes that are included, the more computer storage is required; therefore, the number of modes need to be enough to obtain accurate result but not too many to be over the limit of computer storage. The high number of modes used also decreases computer speed, increasing the running time. The mathematical model was used to predict acoustic properties. It was found that the predicted maximum acoustic pressure inside the central small region, where the disk is located, has the best correlation with the number of droplets for all liquid media and all operating conditions. The mathematical model can only predict which operating condition and atomizer design will provide the maximum acoustic pressure. As a result, we can optimize the fountain type ultrasonic atomizer in order to obtain the best result, suiting each application applied. If the geometry is changed, the model is also required to be re-written so that it will predict accurate results.
5
Rigit, Andrew Ragai Henry. "Performance of charge injection electrostatic atomizer and spray characteristics." Thesis, Imperial College London, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.405844.
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6
Mandal, Anirban. "Computational Modeling of Non-Newtonian Fluid Flow in Simplex Atomizer." University of Cincinnati / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1202997834.
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7
Colbert, Steven Anthony ACairncross Richard A. "Numerical simulations of droplet trajectories from an electrostatic rotary-bell atomizer /." Philadelphia, Pa. : Drexel University, 2007. http://hdl.handle.net/1860/1877.
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8
Billingsley, Matthew C. "Plasma Torch Atomizer-Igniter for Supersonic Combustion of Liquid Hydrocarbon Fuels." Thesis, Virginia Tech, 2005. http://hdl.handle.net/10919/36331.
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To realize supersonic combustion of hydrocarbons, an effective atomizer-igniter combination with the capabilities of fuel preheating, atomization, penetration, mixing, ignition and flameholding is desired. An original design concept incorporating these capabilities was built and tested at Virginia Tech, and was found to provide good penetration, effective atomization, and robust ignition and flameholding. Quiescent testing with kerosene and JP-7 provided initial performance data. The atomizer-injector design was then modified for insertion into a supersonic wind tunnel, and tested with kerosene in an unheated Mach 2.4 flow with typical freestream conditions of To = 280 K and Po = 360 kPa. Water injection was utilized in both cases for comparison and to analyze atomization behavior.
In the quiescent environment, the regeneratively cooled plasma torch igniter was found to significantly increase electrode life while heating, atomizing, and igniting the liquid fuel. Jet breakup length was measured and characterized, and mean droplet size was estimated using an existing correlation. Several qualitative observations regarding quiescent combustion were made, including torch power effects and the process of flame formation. In the supersonic environment, the effect of fuel injection direction was analyzed. Best results were obtained when fuel was injected with a velocity component opposite to the direction of main tunnel flow. Repeatable ignition occurred in the supersonic boundary layer at the fuel stagnation location near the plasma torch plume. Direct, filtered, shadowgraph, and schlieren photographs, temperature measurements, and visible emission spectroscopy provided evidence of combustion and the details of the flame structure.
The new atomizer-igniter design provided robust and reliable ignition and flameholding of liquid hydrocarbon fuels in an unheated supersonic flow at M=2.4, with no ramp, step, or other physical penetration into the flowpath.Master of Science
9
WANG, DEXIN. "STRONGLY SWIRLING FLOW STUDY ON PRESSURE-SWIRL ATOMIZER AND CYCLONE COMBUSTOR." University of Cincinnati / OhioLINK, 2002. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1032210020.
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10
Srinivasan, Vedanth. "A NUMERICAL STUDY OF A NEW SPRAY APPLICATOR." UKnowledge, 2006. http://uknowledge.uky.edu/gradschool_diss/388.
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This study focuses on the design and development of a new spray applicator design utilizing effects of imposed pressure oscillations in conjunction with cavitation collapse energy to create distribution of fine droplets. An oscillating horn placed inside the nozzle performing high frequency oscillations is envisioned to provide the necessary pressure perturbations on the exiting liquid jet, while the nozzle geometry design in configured to amplify cavitation process. Initially, a two-zone approach modeling the nozzle interior and exterior in a separate fashion and later, a coupled strategy is proposed. Parametric studies describing the effect of horn stroke length, frequency, its position inside the nozzle in combination with different nozzle designs and liquid flow rates are explored to identify their contribution in obtaining desired cavitation characteristics. In this regard, incorporation of a backward facing step profile within the nozzle shows strong capability of generating the required cavitation and flow field distribution at the nozzle exit. The velocity modulations occuring at the nozzle exit due to oscillating horn structure result in a wide gamut of liquid structures specific to the imposed oscillation frequency and modulation amplitude. The disintegration characteristics of these modulated liquid jets are studied using a Volume-of-Fluid (VOF) interface capturing approach based on finite volume methodology employing an interface compression scheme. VOF methods are validated against experimental results and then subsequently used to study scaling parameters governing the modulated liquid jets. To perform coupled interior-exterior nozzle computations with cavitation, two new cavitation models are presented: First, a model based on Homogeneous Equilibrium assumptions for tracking cavitation events in a compressible framework is presented. Owing to its inability to simulate incompressible cavitating flows, a new cavitation event tracking model based on a Cavitation-Induced-Momentum-Defect (CIMD) correction approach is formulated utilizing a scalar transport model for vapor volume fraction with relevant transport, diffusion and source terms. Validations of both the models against experimental observations are detailed. Coupled internal-external liquid flow computations from the proposed atomizer design using a VOF-CIMD strategy shows strong potential for rapid drop formation in the presence of cavitation effects. A prototype model of a new spray applicator design is presented.
11
Li, Huiping. "A study of centrifugal atomization of melts." Thesis, University of Surrey, 1999. http://epubs.surrey.ac.uk/842800/.
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The literature on atomization of melts has been reviewed. Models have been developed and applied to analyze the phenomena associated with centrifugal atomization of melts using rotating disk method. Some suggestions and guidelines for the development and operation of a centrifugal atomizer have been given. Previous experiments of melt atomization and present observations of water disintegration at the edge of a rotating disk have confirmed that the disintegration of melts or water occurs in one of three basic modes: direct droplet formation (DDF), ligament formation (LF) and film formation (FF). Wave theories have been used to analyze the disintegration of melts in the different regimes. The equations for the fastest growing wave number have been derived. Models for the calculation of powder particle sizes have been suggested and the calculated results have compared with available experimental data in the literature. Calculations have shown that disk diameter and disk rotating speed are two very important atomizing parameters. The type of melt and melt superheat also affect the powder particles size. In general, fine powder particles can be obtained by increasing disk rotating speed and using large diameter disk, provided that the melt does not solidify on the disk. In the DDF regime waves forming at the periphery of a disk are responsible for the break up of melts. The fastest growing wave number depends on the disk speed, disk diameter and properties of melt. In the FF regime sheet wave theory of Dombrowski and Johns was used to study the collapse of the melt sheet. The fastest growing wave number is a complex function of the speed and thickness of film and the properties of melt and atomizer atmosphere. The effects of disk diameter, disk rotating speed and melt flow rate on atomization are achieved through influencing the speed and thickness of film. The studies on the flow of melts on rotating disks have shown that the film forming on the disk was very thin, about tens of microns and the tangential velocity of melts was much higher than the radial velocity. The analysis of heat transfer of melts on a rotating disk has shown that partial solidification of melts on the disk is possible. To obtain a good atomization condition it is necessary to control the partial freezing of melts on the disk. A large melt superheat and a high melt flow rate are required to prevent melts from freezing on the disk. The use of a small diameter disk can also avoid freezing of the melt on the disk. Combining the calculations of heat transfer on the disk with the prediction of wave theory for particle sizes, it is shown that a disk of small diameter rotating at high speed is desirable for the production of fine powders. The cooling ability obtained by centrifugal atomization using the rotating disk method depends on the design of atomizer, the operating conditions and the type of material to be atomized. A large diameter disk on which solidification of melt is avoided and a high disk rotating speed result to the formation of fine powder particles which experience a high cooling rate. The nucleation undercooling of melt depends on particle size, disk speed, material to be atomized and the nucleation condition. A small particle size and a high disk speed lead to a large undercooling. The times for the completion of solidification of powder particle of typical sizes produced by centrifugal atomization have been calculated and their effects on the atomizer vessel diameter have been discussed.
12
Amedorme, Sherry Kwabla. "Computational and experimental study of two phase flow in pressure swirl atomizer." Thesis, University of Leeds, 2018. http://etheses.whiterose.ac.uk/21590/.
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Atomizers are used in many engineering applications including spray combustion in furnaces, diesel engines, direct injection petrol engines and gas turbine engines. They are also commonly used in applying agricultural chemicals to crops, paint spraying, food processing and cooling of nuclear cores. Pressure swirl atomizers occupy a special position amongst other atomizers because they differ in quality of atomization, simplicity of construction, reliability and low pumping power requirements. Turbulent mixing of the liquid and gas in these atomizers is indispensable consideration in the process of atomization. This thesis presents a recent Eulerian modelling of two-phase flow in a pressure swirl atomizer using Computational Fluid Dynamics (CFD) STAR-CD code and assesses its capabilities and validation. In this novel Ʃ-Y_liq atomisation model, an Eulerian description is applied to solve the two-phase flow assuming both liquid and gas phases as a single continuum with high-density variation at large Reynolds and Weber numbers. The transport equations for the liquid mass fraction and interfacial surface density as well as the average density of the liquid and gas phases are modelled, liquid dispersion correctly captured and their numerical results presented. The results also show atomization characteristics such as droplet velocity and predicted droplet Sauter Mean Diameter (SMD) with reasonable order-of-magnitudes. The predictions show good agreement with experimental results obtained from a laser-diffraction-based drop size analyser (Malvern Spraytec). Different RANS turbulence models are evaluated in order to achieve the best configuration in comparison with experimental measurements and the standard k-ε turbulence model has shown the best performance. Parametric studies were conducted to analyse the influence of the liquid viscosity, surface tension, liquid and gas velocities, liquid and gas densities and pressure on the spray droplet SMD at different locations on the spray centre line and radial distances from the symmetry line of the atomizer. A combination of CFD modeling and the statistical Design of Experiments (DoE) technique known as modified Latin Hypercube Designs (LHD) is applied in order to improve SMD predictions from Ʃ-Y_liq atomisation model. With 4-factor DoE, eighty-seven (87) cases were simulated with the variations and combinations in the design variables such as liquid viscosity 0.31 to 200 mPa.s, surface tension 20 to 75 mN/m, nozzle exit orifice diameter 1.5 to 3.5 mm and liquid velocity from 1 to 6 m/s. The results for the SMD at the axial distances along the spray centreline were obtained. Combinatorial optimization was performed to identify and obtain the optimal nozzle exit orifice diameters, operating conditions and fluid properties that give the most minimum droplet SMD at the spray centreline. The results show remarkable improvement on SMD and new SMD correlation for the model.
13
Ngobeni, P., C. Canario, DA Katskov, and Y. Thomassen. "Transverse heated filter atomizer: atomic absorption determination of Pb and Cd in urine." Journal of Analytical Atomic Spectroscopy, 2003. http://encore.tut.ac.za/iii/cpro/DigitalItemViewPage.external?sp=1000894.
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A transverse heated filter atomizer (THFA) was applied to the direct determination of Cd and Pb in urine, and
its analytical performances were investigated using a PerkinElmer SIMAA 6000 atomic absorption
spectrometer. Seronorm certified human urine reference materials and six realistic samples collected locally were
used for the method validation. The urines were diluted ten- or five-fold with 0.2% HNO3. Cd and Pb nitrate
solutions were employed as standards. Recoveries of the elements from the urine samples were investigated with
the analyte addition method. Compared to the transverse heated graphite atomizer (THGA) with a platform,
the THFA provided a significant reduction of spectral background and chemical interferences from the urine
matrix, without the use of chemical matrix modifiers, a 1.5–2 times increase of the determination sensitivity
and, therefore, a reduction of limits of detection up to 0.018 and 0.2 mg L21 for Cd and Pb, respectively. The
use of a THFA collector made from carbon fiber and a tungsten wire improved recoveries of lead and
cadmium in urine (¢92%). A sampling temperature 150 uC enabled us to skip the drying period, thus a
significantly reduced temperature program was obtained. The accuracies of the measurements of Cd and Pb in
the Seronorm urine materials were in good agreement with the recommended values: 4.1 ¡ 0.1 mg L21 of Cd
(recommended 5) and 92 ¡ 1 mg L21 of Pb (recommended 85). The lifetime of the THFA for Pb determination
was longer than 700 firings, with the sensitivity loss not more than 25% after 500 firings.
14
Aftel, Robert. "Effect of atomization gas properties on droplet atomization in an "air-assist" atomizer." Master's thesis, Virginia Tech, 1996. http://hdl.handle.net/10919/32599.
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Air, nitrogen, argon and carbon dioxide were used as the atomizing gas in an 'air-assist' spray nozzle to determine the effect of these gases on mean droplet size, number density, velocity and their distributions in kerosene fuel spays and spray flames using a two dimensional phase Doppler interferometer. Data have been obtained with these atomizing gases using a base, air assisted case as a reference, since this is the most commonly used atomizing fluid in almost all applications. Comparisons were made between the gases on a mass and momentum flux basis. Both burning and nonburning sprays were investigated. The results show significant differences in atomization characteristics from the atomizer with different gases and under conditions of constant mass and momentum flux of the gas. The results also show that the presence of oxygen in the air atomized sprays assists in the combustion process, since it produces smaller and faster moving droplets, especially at locations near to the nozzle exit. In nonburning sprays, droplets had similar size and velocity. Lighter gases such as nitrogen more effectively atomized the fuel in comparison to the denser gases. Argon and carbon dioxide produced larger, slower moving droplets than air and nitrogen assisted cases in both the burning and nonburning sprays. Flame photographs revealed the argon and carbon dioxide atomized flames to have greater luminosity than air or nitrogen atomized flames.
Master of Science
15
English, Craig Alan. "Development and Characterization of a Synchronously Actuated Response Atomizer for Studying Thermoacoustic Instabilities." Thesis, Virginia Tech, 2012. http://hdl.handle.net/10919/42378.
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Increasing concerns over the condition of our environment and its long term health have led to the development of greener combustion techniques for use in turbomachinery applications. Lean Direct Injection is an active area of research for how fuel is introduced and burned in the combustor section of a jet engine or land based liquid fuel turbine. Overall lean combustion results in lower NOx emmisions while direct injection insures shorter combustor lengths. Lean Direct Injection and other lean burning combustor designs are susceptible to thermoacoustic instabilities. The SARA or Synchronously Actuated Response Atomizer is a liquid fuel atomizer and supply system designed to allow for the active control of droplet size, cone angle, and mass flow rate. These three parameters have been shown to be important in controlling combustion quality and heat release. This research investigates the capabilities of the SARA design in a series of non-reacting tests. Static and Dynamic tests were performed on the SARA nozzle with a maximum actuation of 400 Hz. Also, a novel use of hot-film anemometry was developed to measure the dynamic flow rate fluctuations.Master of Science
16
Deng, Tian. "LES combined with statistical models of spray formation closely to air-blast atomizer." Thesis, Ecully, Ecole centrale de Lyon, 2011. http://www.theses.fr/2011ECDL0037/document.
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Cette thèse présente une extension de l'approche stochastique de l'atomisation primaire de type air assisté près d'un injecteur. Cette approche avait déjà été introduite dans les publications de Gorokhovski et al. Dans le cadre de la simulation des grandes échelles, la zone d'atomisation primaire est simulée comme un corps immergé avec une structure stochastique. Ce dernier est défini par la simulation stochastique de la position et de la courbure de l'interface entre le liquide et le gaz. La simulation de la position de l'interface est basée sur l'hypothèse de symétrie d'échelle pour la fragmentation. La normale extérieure à l'interface est modélisée en supposant une relaxation statistique vers l'isotropie. Les statistiques de la force du corps immergé servent de conditions aux limites pour le champ de vitesse issu de la LES ainsi que pour la production des gouttes de l'atomisation primaire. Celles-ci sont ensuite transportées par une approche lagrangienne. Les collisions entre les gouttes dans la zone d'atomisation primaire sont prises en compte par analogie avec l'approche standard de la théorie cinétique des gaz. Une fermeture est proposée pour la température statistique des gouttelettes. Cette approche est validée par des comparaisons avec les mesures expérimentales de la thèse de Hong. Les résultats numériques pour la vitesse et de la taille des gouttes dans le spray à différentes distances du centre du jet et de l'orifice de la buse sont relativement proches des résultats expérimentaux. Différentes conditions d'entrée pour la vitesse sont testées et comparées aux résultats expérimentaux. Par ailleurs, le rôle spécifique de la zone de recirculation devant le dard liquide est soulignée par le battement du dard liquide et la production de gouttelettesThis thesis introduced an extension to stochastic approach for simulation of air-blast atomization closely to injector. This approach was previously proposed in publications of Gorokhovski with his PHD students. Our extension of this approach is as follows. In the framework of LES approach, the contribution of primary atomization zone is simulated as an immersed solid body with stochastic structure. The last one is defined by stochastic simulation of position-and-curvature of interface between the liquid and the gas. As it was done previously in this approach, the simulation of the interface position was based on statistical universalities of fragmentation under scaling symmetry. Additionally to this, we simulate the outwards normal to the interface, assuming its stochastic relaxation to isotropy along with propagation of spray in the down-stream direction. In this approach, the statistics of immersed body force plays role of boundary condition for LES velocity field, as well as for production of primary blobs, which are then tracked in the Lagrangian way. In this thesis, the inter-particle collisions in the primary atomisation zone are accounted also by analogy with standard kinetic approach for the ideal gas. The closure is proposed for the statistical temperature of droplets. The approach was assessed by comparison with measurements of Hong in his PHD. The results of computation showed that predicted statistics of the velocity and of the size in the spray at different distances from the center plane, at different distances from the nozzle orifice, at different inlet conditions (different gas velocity at constant gas-to-liquid momentum ratio, different gas-to-liquid momentum ratio) are relatively close to measurements. Besides, the specific role of recirculation zone in front of the liquid core was emphasized in the flapping of the liquid core and in the droplets production
17
Mohapatra, Chinmoy Krushna. "Computational Study of Internal Two Phase Flow in Effervescent Atomizer in Annular Flow Regime." University of Cincinnati / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1470741568.
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Corber, P. Andrew. "The performance of a pressure atomizer with a flow obstruction upstream of the nozzle." Thesis, University of Ottawa (Canada), 2009. http://hdl.handle.net/10393/28335.
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The internal flow and the spray formed by a pressure atomizer with an orifice diameter of 1mm and a length to diameter ratio of 10 were studied at injection pressures between 70 and 5000 kPa. Obstructions to flow were also introduced inside the injector to examine their effect on the injector's performance. Visualization of the flow inside the injector indicated that the obstructions caused the flow to cavitate. However, even without any obstruction, cavitation occurred at injection pressures as low as 170 kPa. These results also showed that cavitation can occur in four different modes, depending on the mass flow rate of fuel through the nozzle and the type of obstruction. Images of the resulting spray indicated that the cavitation enhances atomization significantly. Single-component phase Doppler particle analysis and laser diffraction particle sizing were conducted 50 mm, 100mm and 150 mm downstream of the nozzle face to examine the size and velocity distributions of the droplets in the spray. These measurements indicated that for a given liquid flow rate the droplet size was not affected by the structure of the cavitation. Velocity measurements in the spray indicated that the cavitation produces a wider spray cone angle at lower mass flow rates.
19
Meacham, John Marcus. "A Micromachined Ultrasonic Droplet Generator: Design, Fabrication, Visualization, and Modeling." Diss., Available online, Georgia Institute of Technology, 2006, 2006. http://etd.gatech.edu/theses/available/etd-07072006-103414/.
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Thesis (Ph. D.)--Mechanical Engineering, Georgia Institute of Technology, 2007.Mark Papania, MD, Committee Member ; Mark Allen, Committee Member ; Yves Berthelot, Committee Member ; Ari Glezer, Committee Member ; F. Levent Degertekin, Committee Chair ; Andrei G. Fedorov, Committee Chair.
20
Akafuah, Nelson Kudzo. "VISUALIZATION AND CHARACTERIZATION OF ULTRASONIC CAVITATING ATOMIZER AND OTHER AUTOMOTIVE PAINT SPRAYERS USING INFRARED THERMOGRAPHY." UKnowledge, 2009. http://uknowledge.uky.edu/gradschool_diss/792.
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The disintegration of a liquid jet emerging from a nozzle has been under investigation for several decades. A direct consequence of the liquid jet disintegration process is droplet formation. The breakup of a liquid jet into discrete droplets can be brought about by the use of a diverse forcing mechanism. Cavitation has been thought to assist the atomization process. Previous experimental studies, however, have dealt with cavitation as a secondary phenomenon assisting the primary atomization mechanism. In this dissertation, the role of the energy created by the collapse of cavitation bubbles, together with the liquid pressure perturbation is explicitly configured as a principal mechanism for the disintegration of the liquid jet. A prototype of an atomizer that uses this concept as a primary atomization mechanism was developed and experimentally tested using water as working fluid.
The atomizer fabrication process and the experimental characterization results are presented. The parameters tested include liquid injection pressure, ultrasonic horn tip frequency, and the liquid flow rate. The experimental results obtained demonstrate improvement in the atomization of water.
To fully characterize the new atomizer, a novel infrared thermography-based technique for the characterization and visualization of liquid sprays was developed. The technique was tested on the new atomizer and two automotive paint applicators. The technique uses an infrared thermography-based measurement in which a uniformly heated background acts as a thermal radiation source, and an infrared camera as the receiver. The infrared energy emitted by the source in traveling through the spray is attenuated by the presence of the droplets. The infrared intensity is captured by the receiver showing the attenuation in the image as a result of the presence of the spray.
The captured thermal image is used to study detailed macroscopic features of the spray flow field and the evolution of the droplets as they are transferred from the applicator to the target surface. In addition, the thermal image is post-processed using theoretical and empirical equations to extract information from which the liquid volume fraction and number density within the spray are estimated.
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ABU-NABAH, BASSAM ABDEL-JABER. "SWIRL ORIENTATION EFFECT ON THE INSTABILITY AND THE BREAKUP OF ANNULAR LIQUID SHEETS." University of Cincinnati / OhioLINK, 2003. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1060978117.
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Lessmann, Nils. "Numerical and experimental investigations of the disintegration of polymer melts in an ultrasonic standing wave atomizer." [S.l. : s.n.], 2004. http://deposit.ddb.de/cgi-bin/dokserv?idn=974405027.
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Seidu, Iddrisu. "Analytical and Numerical Validation of Nozzle Spray Measurement Data Obtained from a Newly Developed Production System." Cleveland State University / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=csu1446504762.
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XUE, JIANQING. "COMPUTATIONAL SIMULATION OF FLOW INSIDE PRESSURE-SWIRL ATOMIZERS." University of Cincinnati / OhioLINK, 2004. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1100228747.
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Klassen, Aline. "Avaliação de tubo metalico como atomizador na tecnica de HG-AAS : analise de parametros analiticos e morfologicos." [s.n.], 2007. http://repositorio.unicamp.br/jspui/handle/REPOSIP/248578.
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Orientador: Marco Aurelio Zezzi ArrudaDissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Quimica
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Resumo: Nesta Dissertação foi avaliada a eficiência do atomizador metálico (liga INCONEL600®) na técnica de HG-AAS (do inglês, hydride generation atomic absorption spectrometry) . A dissertação está dividida em três Capítulos sendo cada um referente ao desenvolvimento da metodologia para determinação de As, Bi e Se, respectivamente. Foram avaliadas variáveis físicas e químicas por meio do uso de soluções de referência de 50 mg L para As e Bi, e de 400 mg L para Se. Dentre estas variáveis podemos citar: concentração de ácido (exceto no caso do Se, em que a concentração foi mantida em 7 mol L), de NaBH4 e de NaOH, comprimento do reator, alça de amostragem, vazão de solução carregadora, vazão de gás de arraste, diâmetro interno do capilar cerâmico entre outros. Alguns parâmetros analíticos foram obtidos, respectivamente para As, Bi e Se: limite de detecção (LD), ( 2,3; 0,7; 1,8 mg L), desvio padrão relativo (RSD), (5,8; 2,7; 10%) e coeficiente de regressão (R), (0,9978; 0,9997; 0,9974). O desvio padrão relativo do método foi baseado nas réplicas das amostras. Posteriormente, foi realizado um estudo de possíveis concomitantes na determinação de As, Bi e Se. As proporções de analito:concomitante foram baseadas no universo das amostras usadas nesta dissertação para os elementos As e Se. Com esse estudo, pôde ser verificado que a seletividade foi grandemente afetada pela presença de Cu, Fe e Ni, para a determinação de As e Bi, no entanto, para a determinação de Se, os elementos Cu, Bi e As interferiram. Os testes de exatidão dos métodos propostos foram averiguados por meio do uso de materiais de referência certificados de amostras ambientais, bem como de interesse medicinal. Os valores encontrados foram concordantes com os valores certificados, segundo um intervalo de confiança de 95% de acordo com o teste t. Após o término do desenvolvimento de cada metodologia, os atomizadores foram cortados em diferentes pontos e foram obtidas algumas micrografias, bem como a composição da liga, por meio do detector de Raios-X. Com esse estudo foi possível inferir algumas explicações sobre a necessidade da injeção de um padrão concentrado no sistema para determinação de arsênio, bem como a descoberta de nanotubos de carbono na superfície do atomizador empregado na metodologia para determinação de bismuto. A existência de nanotubos de carbono foi confirmada por meio da técnica de TEM. Esse resultado é interessante, uma vez que o custo dos nanotubos é elevado e o mesmo tem sido empregado em diversas aplicações na Ciência.
Abstract: In this work, the metal atomizer (alloy INCONEL600®) efficiency in the HG-AAS technique was evaluated. It was divided into three Chapters, each one referring to the development of methodologies for arsenic, bismuth and selenium. Physical and chemical variables were evaluated using reference solutions of 50 mg L for As and Bi, and 400 mg L for Se. The evaluated variables were: acid, NaBH4 and NaOH concentration, length of the reaction coil, injected volume, carrier flow rate, argon carrier flow rate, inner diameter of the capillary, among others. The acid concentration for selenium determination was fixed at 7 mol L. After methodology optimization, some analytical parameters were obtained, respectively for As, Bi and Se: limit of detection - LOD, 2.3, 0.7 and 1.8 mg L, relative standard deviation - RSD, 5.8, 2.7 and 10% and regression coefficient - R, 0.9978, 0.9997 and 0.9974. The RSD of the method was based on As, Bi and Se analytical repeatability from samples. Then, a concomitant study was carried out for As, Bi and Se determination. The analyte:concomitant proportion for As and Se was based on those samples used in this work. This result showed that the presence of Cu, Fe and Ni greatly affected the selectivity for As and Bi, as well as Cu, Bi and As can be considered potential concomitants for Se. Certified reference materiais as well as medical samples were used for checking the accuracy of the proposed methods. By analyzing the results using the t test, no statistical difference at the 95% confidence level was found. After finishing the development of the analytical procedure as well as its application to real samples, each metal atomizer used for each developed methodology was then cut in different parts and morphological as well as X-ray analysis were performed to evaluate the metal distribution on the atomizer. From this study, some explanation was made about the necessity of the standard solution injection into the system for As determination. Additionally, carbon nanotubes were also found in the atomizer surfaces when it was applied to Si determination. Its presence was confirmed by the transmission electronic microscopy technique.
Mestrado
Quimica Analitica
Mestre em Química
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Loney, Drew Allan. "Coupled electrical and acoustic modeling of viscous fluid ejectors." Diss., Georgia Institute of Technology, 2014. http://hdl.handle.net/1853/54247.
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The focus of this dissertation is the development of a fundamental understanding of the acoustics and piezoelectric transducer governing the operation of piezoelectric inkjets and horn-based ultrasonic atomizers when utilizing high viscosity working fluids. This work creates coupled, electro-mechanical analytical models of the acoustic behavior of these devices by extending models from the literature which make minimal simplifications in the handling terms that account for viscous losses. Models are created for each component of the considered fluid ejectors: piezoelectric transducers, acoustic pipes, and acoustic horns. The acoustic pipe models consider the two limited cases when either the acoustic boundary layer or attenuation losses dominate the acoustic field and are adapted to account for changes in cross-sectional area present in acoustic horns. A full electro-mechanical analytical model of the fluid ejectors is formed by coupling the component models using appropriate boundary conditions.
The developed electro-mechanical model is applied to understand the acoustic response of the fluid cavity alone and when combined with the transducer in horn-based ultrasonic atomizers. An understanding of the individual and combined acoustic response of the fluid cavity and piezoelectric transducer allow for an optimal geometry to be selected for the ejection of high viscosity working fluids. The maximum pressure gradient magnitude produced by the atomizer is compared to the pressure gradient threshold required for fluid ejection predicted by a hydrodynamic scaling analysis. The maximum working fluid viscosity of the standard horn-based ultrasonic atomizer and those with dual working fluid combinations, a low viscosity and a high viscosity working fluid to minimize viscous dissipation, is established to be on the order of 100mPas.
The developed electro-mechanical model is also applied to understand the acoustic response of the fluid cavity and annular piezoelectric transducer in squeeze type ejectors with high viscosity working fluids. The maximum pressure gradient generated by the ejector is examined as a function of the principle geometric properties. The maximum pressure gradient magnitude produced by the ejector is again compared to the pressure gradient threshold derived from hydrodynamic scaling. The upper limit on working fluid viscosity is established as 100 mPas.
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IBRAHIM, ASHRAF. "COMPREHENSIVE STUDY OF INTERNAL FLOW FIELD AND LINEAR AND NONLINEAR INSTABILITY OF AN ANNULAR LIQUID SHEET EMANATING FROM AN ATOMIZER." University of Cincinnati / OhioLINK, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1154536582.
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MA, ZHANHUA. "INVESTIGATION ON THE INTERNAL FLOW CHARACTERISTICS OF PRESSURE-SWIRL ATOMIZERS." University of Cincinnati / OhioLINK, 2002. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1016634882.
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Malý, Milan. "Experimentální studie vlastností spreje a funkčnosti malých tlakových vířivých trysek." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2016. http://www.nusl.cz/ntk/nusl-254386.
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Diplomová práce se zabývá experimentální studií vlastností spreje z několika malých tlakových vířivých trysek používaných ve spalovacích komorách proudových motorů. Po desetiletí byla snaha zlepšit jejich rozprašovací charakteristiky a stále jsou možnosti, které nebyly téměř prozkoumány. Výzkum byl proveden za použití různých geometrií jednotlivých dílů trysky za účelem zjištění jejich vlivu na sprej. Byl použit různý počet vstupních portů (2, 3 a 4), různé vířivé komůrky (kulová, kuželová, konvexní, nízká kuželová) a rozdílné návrhy obtokového otvoru (osové, mimosové). Důraz byl kladen na posouzení stability spreje, kde pulzující sprej negativně ovlivňuje provozní charakteristiky spalovací komory. Vlastnosti spreje byly proměřeny fázovým dopplerovským analyzátorem, cirkulární homogenita byla hodnocena mechanickým paternátorem a rozpad kapaliny byl vizualizován pomocí jednoduchého laserového stínografu.
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Schenk, Robert [Verfasser], Rafael [Akademischer Betreuer] Macián-Juan, Winfried [Gutachter] Petry, and Rafael [Gutachter] Macián-Juan. "REP Atomizer Engineering & UMo Fuel-Powder Fabrication / Robert Schenk ; Gutachter: Winfried Petry, Rafael Macián-Juan ; Betreuer: Rafael Macián-Juan." München : Universitätsbibliothek der TU München, 2016. http://d-nb.info/1156713447/34.
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Malý, Milan. "Internal Flow of Spill-Return Pressure-Swirl Atomizers." Doctoral thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2021. http://www.nusl.cz/ntk/nusl-437981.
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Tlakové vířivé trysky (TVT) jsou používané v mnoha aplikacích, kde je potřebná velká plocha kapek nebo kde povrch musí být nanesen kapalinou, např. spalování, sprejové chlazení nebo nanášení barev. Parametry spreje z TVT jsou úzce spojené s jejich vnitřním prouděním. Obtokové trysky vylepšují koncepci klasických TVT přítomností otvoru, skrz který může kapalina odtékat zpět do nádrže. Díky této koncepci je možné regulovat vstřikovací množství kapaliny změnou průtoku tímto otvorem, zatímco se ve vířivé komůrce udržuje vysoký tlak, který zaručí dobrou kvalitu spreje. Obtokové trysky byly historicky málo prozkoumány a jejich vnitřní proudění nebylo studováno téměř vůbec. V této práci je popsáno vnitřní proudění několika obtokových trysek jak experimentálně, tak numericky. Tato data jsou následně korelována s měřenými vlastnostmi spreje. Výsledky ukazují, že přidání obtokového otvoru silně ovlivní vnitřní proudění i v případech, kdy obtokem neproudí žádná kapalina. V některých případech se vůbec nezformuje vzdušné jádro a tím se destabilizuje výtok z trysky, čímž vznikne nestabilní sprej. Mimoosé obtokové otvory generují a stabilizují vzdušné jádro, což pomáhá formovat kapalinovou stěnu a vysoce kvalitní sprej. Nicméně některé konfigurace změnily charakter rozpadu kapalinové stěny, což se projevilo i na kvalitě spreje. Navíc regulační schopnost a stabilita spreje závisí na vzdálenosti obtokových otvorů od osy vířivé komůrky. Na závěr byla upravena neviskózní teorie, která analyticky popisuje vnitřní proudění v TVT, tak aby byla aplikovatelná i na obtokové trysky. Pomocí tohoto přístupu byla odvozena teoretická predikce výtokového součinitele a velikosti vzdušného jádra v závislosti na obtokovém poměru (SFR). Zároveň byly pro obtokové trysky upraveny empirické korelace původně odvozené pro TVT. Tato práce přináší nový vhled k porozumění vnitřního proudění obtokových trysek a její výsledky najdou uplatnění při jejich návrhu.
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Mattes, William Patrick 1967. "An evaluation of habitat conditions and species composition above, in, and below the atomizer falls complex of the Little Colorado River." Thesis, The University of Arizona, 1993. http://hdl.handle.net/10150/292043.
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Water chemistry (carbon dioxide, pH, alkalinity, hardness, and turbidity) and physical habitat (depth, velocity and substrate) change gradually on the Little Colorado River, Arizona, downstream from Blue Springs (river kilometer 11.40 to 21.06). Fish distribution is correlated with changes in water chemistry and physical habitat. Monthly trends in water chemistry and physical habitat depended upon seasonal conditions: summer rain runoff (July and September 1992), spring runoff (April 1993), and base flow (June and July 1993).
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Kuhnhenn, Maximilian [Verfasser], Cameron [Akademischer Betreuer] Tropea, Ilia V. [Akademischer Betreuer] Roisman, and Peter [Akademischer Betreuer] Walzel. "Rotary Atomizer: Investigation of the Internal and External Liquid Flow and Atomization / Maximilian Kuhnhenn ; Cameron Tropea, Ilia V. Roisman, Peter Walzel." Darmstadt : Universitäts- und Landesbibliothek Darmstadt, 2019. http://d-nb.info/117936158X/34.
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Li, Jianing. "Characterization of a Novel Porous Injector for Multi-Lean Direct Injection (M-LDI) Combustor." University of Cincinnati / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1530269081550143.
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Furdíková, Zuzana. "Studium generování, záchytu a atomizace těkavých hydridů pro metody atomové spektrometrie." Doctoral thesis, Vysoké učení technické v Brně. Fakulta chemická, 2009. http://www.nusl.cz/ntk/nusl-233290.
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Interference effects of co-generated hydrides of arsenic, antimony, bismuth and selenium on trapping behavior of selenium or antimony hydrides (analytes) within iridium modified, transversely heated graphite tube atomizer (THGA) was investigated. A twin-channel hydride generation system was used for independent separate generation and introduction of analyte and interferent hydrides, i.e. in simultaneous and/or sequential analyte-interferent and interferent-analyte mode of operation. Influence of the analyte and modifier mass, interferent amount, trapping temperature and composition of the gaseous phase was studied. A simple approach for elimination of mutual interference effects by modification of the gaseous phase with oxygen in substoichiometric ratio to chemically generated hydrogen is proposed and suppression of these interference effects is demonstrated. A hypothesis on mechanism of trapping and mutual interference effects is drawn.
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Mead, Ryan M. "Analysis of Flow in a Spray Nozzle With Emphasis on Exiting Jet Free Surface." [Tampa, Fla.] : University of South Florida, 2003. http://purl.fcla.edu/fcla/etd/SFE0000138.
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Zaremba, Matouš. "Experimentální analýza procesu rozpadu kapaliny u šumivé trysky." Doctoral thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2018. http://www.nusl.cz/ntk/nusl-370740.
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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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Durand, Corinne. "Atomisation de gouttes liquides sur une cible tournante microstructurée." Thesis, Grenoble, 2014. http://www.theses.fr/2014GRENI035.
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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 TechnogeniaThe 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
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Hong, Chin Tung. "Analysis of flow in a 3D chamber and a 2D spray nozzle to approximate the exiting jet free surface." [Tampa, Fla.] : University of South Florida, 2004. http://purl.fcla.edu/fcla/etd/SFE0000560.
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Leme, Flavio de Oliveira. "\"Avaliação do método das médias móveis no tratamento de sinais de absorção atômica de cádmio, chumbo e crômio obtidos por atomização eletrotérmica em filamento de tungstênio\"." Universidade de São Paulo, 2006. http://www.teses.usp.br/teses/disponiveis/75/75132/tde-05062007-142325/.
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Este trabalho teve como objetivo avaliar o uso do método das médias móveis na atomização de cádmio, crômio e chumbo utilizando filamento de tungstênio de 150 W (OSRAM) como atomizador eletrotérmico. Realizou-se um estudo sistemático da influência da altura de observação, da temperatura e taxa de aquecimento na atomização dos analitos e a viabilidade do uso do método das médias móveis no tratamento dos sinais transientes gerados na atomização. O estudo da influência da altura de observação foi realizado posicionado-se o filamento no centro (0 mm), 1 e 2 mm abaixo do feixe de radiação. A influência da temperatura e da taxa de aquecimento foi estudada utilizando temperaturas na etapa de atomização entre 1890 e 2780 °C. O método das médias móveis foi aplicado aos sinais transientes gerados na atomização, com o filamento posicionado no centro (0 mm), 1 e 2 mm e com temperatura de atomização entre 2060 e 2780 °C, utilizando fatores 0, 3, 5, 7 e 9. No estudo da temperatura e da taxa de aquecimento foram aplicadas ddps no software de controle na etapa de atomização entre 4 e 12 V. As soluções usadas no desenvolvimento deste trabalho foram preparadas em meio 0,1 % v/v HNO3. Utilizou-se como gás de proteção a mistura de 90% Ar+10 % H2. Para o cádmio, recomenda-se a utilização da altura de observação de 1 mm, para o chumbo recomenda-se 0 mm e para o crômio a altura recomendada é a de 2 mm. Os estudos comprovaram a dependência dos sinais de absorção atômica em altura de pico com a temperatura e a taxa de aquecimento. O cádmio foi o analito em que a taxa de aquecimento foi a menos crítica para a atomização, enquanto que o crômio foi o mais afetado pela variação da taxa de aquecimento. Não foi observada diferença significativa entre os sinais de cádmio com alturas de observação de 0 e 1 mm. Para o chumbo, a diferença entre os sinais com altura de observação de 0 e 1 mm foi constante em todas as taxas de aquecimento estudadas. A 2 mm a diferença entre os sinais aumentou com o aumento da taxa de aquecimento. Para o crômio, não ocorreu uma diferença significativa entre os sinais nas alturas de 1 e 2 mm com atomização até 2180 °C. Nos três analitos a sensibilidade aumentou com o aumento da taxa de aquecimento. O método das médias móveis permitiu a diminuição da variação dos sinais transientes do branco e do ruído. Para o cádmio, não ocorreu uma melhora no limite de detecção do método com a aplicação das médias móveis em nenhuma condição. Para o chumbo e crômio, ocorreu uma melhora no limite de detecção do método nas alturas de observação de 0 e 1 mm. O limite de detecção instrumental apresentou uma melhora significativa para os três elementos em todas as condições estudadas.The aim of this paper was to evaluate the use of moving averages of cadmium, chromium and lead transient atomic absorption signals generated by 150 W (OSRAM) tungsten coil electrothermal atomizer. A systematic study dealing with the influence of observation height, temperature and heating rate on atomization was carried through in order to demonstrate the viability of moving averages in the treatment of the transient signals during the atomization step. The influence of observation height was carried out with the tungsten coil in the center (0 mm), at 1 and 2 mm below the radiation beam. The influence of atomization temperature and heating rate were evaluated between 1890 °C (3.3 K.ms-1) and 2780 °C (9,3 K.ms-1). The transient moving averages were obtained by using factors 0, 3, 5, 7 and 9, with the tungsten coil in the center (0 mm), 1 and 2 mm and with atomization between 2060 and 2780 °C. For obtaining different temperatures and heating rates, an appropriate power supply was used by applying 4 to 12 V (40 to 120 W) to the atomizer during atomization and a mixture 90% Ar+10% H2 was used as purge/atomization gas. Blanks and reference solutions were prepared in 0,1% v/v HNO3. Best results for cadmium were obtained at 1 mm. For lead it is recommended 0 mm and for chromium 2 mm. The studies had proven the dependence of peak height absorbance signals with temperature and heating rate. Cadmium was the analyte where the heating rate was to less critical for the atomization, whereas chromium was affected by the variation of the heating rate. Significant differences were not observed between cadmium signals with observation heights of 0 and 1 mm. For lead, the difference between the absorbance signals with observation heights of 0 and 1 mm were constant in all tested heating rates. At 2 mm the difference between signals increased by increasing the heating rates. For chromium, a significant difference was not noticed between peak height absorbance signals at 1 and 2 mm with up to 2180 °C. As expected, sensitivity increased for all three analytes by increasing the heating rate. The moving average is a powerful mathematical treatment for minimizing unpredictable fluctuations of the base line during the chosen time interval for measuring the transient absorbance signals. With the exception of Cd, where no improvements on the method detection limit were noticed, the application of the moving average for the lead and chromium showed 3 to 4 fold improvement in the LDmet at 0 and 1 mm observation heights, respectively. The LDinstr presented a significant improvement (3 to 6 fold) for the three analytes in all studied conditions.
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Beinstein, Zbyněk. "Nestability spreje u trysek typu effervescent." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2009. http://www.nusl.cz/ntk/nusl-228558.
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Master thesis focused on the research of the effervescent atomizers. Effervescent atomizers belong to a group of two-phase atomizers, which are often used in combustion applications. Right there in combustion applications, the degree of the stability sprays has a significant impact on combustion efficiency and exhaust gas emissions. The main aim of this work was to asses the level of spray unsteadiness depending on the atomizer design and its operating mode. The effect of construction was studied on the diameter and length of mixing chamber, and then on the size, number and location of aeration holes. Seventeen specific variants of the atomizer were constructed by different combinations of these design parameters. Each of these variants was measured in three operating modes, which were represented by a liquid pressure at the inlet to the atomizer and gas-to-liquid mass flow ratio (GLR). To evaluate the level of spray unsteadiness was used a methodology, which compares the ideal element´s distribution into the interparticle time bin, defined for the ideal (stable) spray, with the experimentally observed distribution. The laser measurement system P/DPA (Phase Doppler Particle Analyzer) was used to determine the experimental interparticle distribution. The result of the comparison of the ideal and the experimental distribution was the parameter , which expresses the level of spray unsteadiness for a specific atomizer and operating mode. With that parameter it was possible to compare the individual atomizers and determinate to the benefit of various construction´s correction of the atomizer. The results showed the recommendation for the modifications of the atomizer, creating a spray with a minimum level of spray´s unsteadiness. For the surveyed atomizer and his individual costruction´s variations the drawing was made.
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Chen, Ming-Yong, and 陳明永. "Ultrasonic atomizer." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/86520565466273631519.
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碩士國立雲林科技大學
電機工程系碩士班
100
In this paper the use of vibrator inverse piezoelectric effect, generate ultrasonic frequency range of electrical signals through electronic drive circuit to generate high frequency oscillation principle to promote the piezoelectric oscillator , resulting in their deformation behavior of ceramic materials, squeeze the liquid through the deformation, to current into mechanical vibrations of the ultrasonic wave frequency of vibration of liquid mist particles into very small , that the ultrasonic nebulizer. Production of this paper complete the following five parts of the internal circuit design : (A)the power circuit : 110V 60Hz step-down transformer to generate the required input by the three groups of power , DC24V for the oscillator circuit, fan use , DC 5V micro- controller IC for use. (B) ultrasonic oscillation circuit: the decision of high volatility, piezoelectric oscillator. (C) MCU control circuit: charge (1) control oscillator circuit of the power supply. (2) the strength of spray volume control. (3) low- level detection. (4) PWM three-color LED lights change color mixing. (5) the working state light control. (D) micro- controller IC: to HT4806A-1 as the main control circuit , writing assembly language. (E) the water level detection control circuit: the use of C1815 transistors water level probe to the 1K resistor connected to the MCU''s I / O, the voltage level of the High / Low in the low water level to determine whether state.
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Goung, Wei-Young, and 龔偉揚. "Combustion Characteristics of the Swirl Atomizer." Thesis, 1996. http://ndltd.ncl.edu.tw/handle/76909550857646411426.
Full textAbstract:
碩士國立成功大學
機械工程研究所
84
In order to research the hollow-cone spray flames formed by the SIMPLEX pressure-swirl nozzle,the equipments founded the ethanol and gasoline spray flames in open space have been set up. A measurement is experimentally developed to investigate the influence of spray flame shape,stability,lift-off height and spray angle by the different fuel injection pressure.The temperature distribution of spray flames is know by a thin thermocouple.Using Malvern 2600 laser diffraction instrument, distribution of droplet sizes along the axial distance has been measured in the experiment.Hense,the phenomenon that droplet collision would be discussed.The results show the different spray flames structure of ethanol and gasoline spray flames,and the group combustion in these two type spray flames is also discussed. Besides,the study of gasoline spray flames in a uniform periphery stream which include variable gas composition and flow rates reveals the structure of flame front,the position of stable flame type which accured suddently and the decrease of lift-off distance by the increase of oxygen concentraction.A special case is also found that an increase in oxygen concentraction forms a stretching internal flame. These experiments will provide an information about the characteristics of spray flames,and expect to improve the designed method and manufactured technology of the SIMPLEX pressure-swirl nozzle.
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Su, Chien-Chan, and 蘇健展. "Fabrication and Simulation of Piezoelectric Micro-Atomizer." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/93316663718657063975.
Full textAbstract:
博士國立中正大學
機械工程所
95
The main purpose of this study presents the design and the micromachined fabrication of a bimorph PZT-driven atomizer. The developed atomizer can produce smaller droplets and eject large amount of flow rate. The phenomenon of atomization is investigated in this study. The large displacement of PZT bimorph plate used and the trumpet-shape micro-nozzle array obtained by using the micro-electroplated method are the characteristics of this study. The experimental measurement and numerical simulation have been performed to gain the insight of atomized droplet behavior. The fluid dynamics simulation package of CFD-RC is used to simulate the droplets ejected from the nozzles plate. It is coupled with volume of fluid (VOF) and piecewise linear interface calculation (PLIC) techniques to conduct the volume fractions of liquid, and reconstruct the interface of the liquid/gas, which involves the two phases flow in the formation and ejection process. The effects of the surface tension of the liquid are evaluated by the CSF model in the momentum equations. From the experimental results of the testing liquid methyl alcohol with viscosity of 0.26cp and the nozzle diameter of 6.5μm, it reveals that the atomizer is capable of generating droplets with an SMD of 4.24 mm under the operating voltage of 22 Vpk-pk, current of 180mA, and frequency of 24 kHz. It shows that this atomizer has the potential for applications that need fine droplets, such as methanol injectors in Direct Methanol Fuel Cell (DMFCs), odor generators, cosmetic and medical applications, etc. The performance of the atomizer exhibiting uniformly relative size distribution of ejected droplets is a characteristic. From the present investigations, we can clearly realize that the injection flow rate can be maximized by setting the frequency of the operating voltage at the resonant frequency of the piezoelectric actuator. Air trapped within the atomizer reservoir adversely affects the injection performance. As the viscosity of the ejected liquid increases, the flow rate is reduced and the average particle size increases. The diameter of particles can be reduced by increasing the operating frequency. Keywords : Micro-atomizer, Micro-electroplating.
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Chen, Hong-Ting, and 陳泓廷. "Preparation of Chitosan Microparticles by Ultrasonic Atomizer." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/ag7xv8.
Full textAbstract:
碩士國立臺北科技大學
生物科技研究所
97
Chitosan solutions were ultrasonic atomized; then dried by a heated column. The size and morphology of the dried chitosan particles were observed by a scanning electron microscope (SEM). Chitosan particles with narrow distributed diameter from about 0.2 through 3um can be prepared by the ultrasonic atomization under different composition of solution. It was found that the particle size increases with increasing of the concentration of chitosan in acetic solution. Furthermore, chitosan particles loaded with theophylline were prepared by a co-spray drying with the crosslinking agent.
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C, P. Chien, and 簡金品. "A Study of Thermal Micropump for Fuel Atomizer." Thesis, 2003. http://ndltd.ncl.edu.tw/handle/94717163536254129057.
Full textAbstract:
碩士國立臺北科技大學
冷凍與低溫科技研究所
91
In the research study, the commonly used analytical software in computational fluid dynamics, CFD-RC, was employed to analyze the simulated droplet injection speed, shape, motion path, internal flow of the micropump, and replenishing rate of the working fluid in the micropump after the injection. The observed data from the experiments would be used to confirm the analysis results. The objective of this study was to analyze the injection characteristics of the micropump under ambient temperature, high temperature, and still air at 15m/sec flow speed, given that the micropump motion frequency was 5kHz. The fluid and external gas were incompressible fluids, the governing equation was mass and momentum conservation equation and the energy conservation equation. Volume-Of-Fluid (VOF) method was used to describe the size and motion path of the droplets. Finite Volume method was used, and Pressure Based SIMPLEC algorithm was employed for solution. Studying the impact of varied fluid, array injection, external air flow, and external high temperature, the results showed that the flow speed of Stoddard solvent droplet was 16.0m/s and the water droplet was 15.0m/s at low external air flow, and the flow speed of Stoddard solvent droplet was 16.0m/s and the water droplet was 14.0m/s at high external air flow in the fuel atomizer injection system. The replenishing rate was 97%. Based on the observation data, a larger flow rate was generated when the voltage was 26V, the frequency was 5KHz, and the bandwidth was 4~5µs, the Stoddard solvent droplet was 17m/sec, the motion path at 1000µm away from the injection hole.
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Lai, Chung-Wei, and 賴春維. "Performance of an Ultrasonic Atomizer with Hartman Resonator." Thesis, 2001. http://ndltd.ncl.edu.tw/handle/39262452625676326229.
Full textAbstract:
碩士國立成功大學
航空太空工程學系
89
An experimental study is conducted to investigate the atomization performance of an Ultrasonic Atomizer with Hartman resonator. The atomization mechanism of the liquid spray comes the energy of high frequency vibration in the resonator. A typical resonator is called “Hartman generator.” The experiments have a controlling device to control the mass flow rates of the liquid and the atomization gas. The flow field and the droplet size of the spray are measured with the image processing system and Insitec particle sizer. The observation of the flow field shows that the spray cone angles are less than 180 o when the atomizer is operated at appropriate liquid and air pressure. If the liquid pressure is less than the critical liquid pressure, the spray cone angles will be larger than 180 o , a condition called the unstable operation. The unstable operation happens when the reversal air momentum is not balanced by the mechanism of momentum of the incoming air and liquid flow. However, this unstable condition can be improved by increasing the liquid pressure. It is also found the liquid and gas flow rates are mainly determined by the diameters of liquid flow path and the outlet orifice of the atomizers, respectively. The air and liquid flow rates are also controlled by the air and liquid pressures. Results further show that the Sauter mean diameter of this typical spray is better than that from the conventional atomizer. For example, under Pw = 5kg/cm2 and Pa=6 kg/cm2, SMD varies from 10.57 μm to 14.36μm as the resonator size increases from 2.0mm to 3.0mm. Therefore we can see that the resonator plays a very effective role in the atomization. Results also show that the performance of the atomizer is essentially dependent on the air/liquid mass ratio and is approaching a limit when the air/liquid mass ratio is over 1.0. It implies that further atomization of the spray droplets becomes more difficult when they are small length. Hence the increase in atomization gas is less effective to produce smaller droplets. Moreover, the increase of atomization gas is limited by the choking condition of the gas flow at the nozzle outlet. Comparison of various air-assist atomizers indicates that the drop size distribution of internal mixing atomizers in this study, such as CK-5 and H-1 atomizers, is more uniform and the particle sizes are smaller than other atomizers. It is suggested that the atomization mechanism with internal mixing of liquid and gas inside the nozzle is more efficient than that with external mixing mechanism when air speed is less than speed of sound.
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Wang, Chih-Chi, and 王郅期. "Investigation of atomization phenomenon in a rotary atomizer." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/32mj93.
Full textAbstract:
碩士國立交通大學
機械工程系所
105
The rotary atomizer is widely used in industrial applications such as painting and powder production. This method in industry is better than traditional nozzle spray because of wider spray area, higher speed of droplets, and higher efficiency of droplets transfer. In the category of electronic heat dissipation, favorable performance using the rotary atomizer can be applied for the spray cooling. This research used water as the working fluid and investigated the physical phenomenon of low viscosity liquid. Global sizing velocimetry system was used to measure the diameter, velocity, and number of spray droplets under different parameters. There were two types of rotary atomizer cups in the experiment. These aluminum alloy rotary cups had the diameters of 50mm. Regarding the cup geometry, one cup exhibited 0 degree and the other cup exhibited 45 degree between inner face and outer face of the cup. A motor and an inverter were employed to control the rotary speed between 3000rpm and 12000rpm, and the injected water flow rates were 9l/h and 18l/h. The results from the current research can be used for future development of the rotary atomizer.
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Yang, Fu-Lin, and 楊富麟. "Particle Separation Process Using Ultrasonic Atomizer and Impactor." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/psg248.
Full textAbstract:
碩士國立臺北科技大學
機電整合研究所
96
This study aims at exploring a laboratory-made micro-fog condensing system and micro-fog impactor which applies the benefits of vibrating foggy effect onto separation of particles. This work also discusses how to process a better separation way in order to get sub-micro or nanoscaled particles. The experiment uses ball-milled ZnO powders as the test sample. This separation mechanism is achieved through the formation of fog created using ultrasonic vibrator. With the aid of fanning and pump, the fog will pass through into impactor, used inertia of particles to separate micro-fog. The ultrasonic atomization is proven to be able to separate micron and nanoscaled particle from aqua. The smallest particle size is 68nm from the experiment and the tendency of separation was the same with little particles inertia. They most influenced with the efficiency of separation in the impactor that changing the entrance of flow velocity and the jet flow diameter by the experiment.
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Chang, Shao-Jui, and 章劭睿. "Power ultrasonic driving circuit model applying to atomizer." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/23469989452139798875.
Full textAbstract:
碩士國立臺灣大學
工程科學及海洋工程學研究所
98
In recent years, accompanying with the development of the high-speed switch device and microprocessor technology, the range of high power ultrasonic application becomes very broad. The power ultrasonic usually applies to sonar, atomization, cleaning technology, and medical instrument, etc. However, a good designed ultrasonic driving circuits for the power ultrasonic system is very deficient. In General, frequency of high power ultrasonic circuit reaches a maximum of hundreds of thousands hertz, whereas the high frequency circuit can just provide limited power. Long-term steady-going operating is also a problem for power ultrasonic driving circuit on design and in use. Therefore, this paper shows a high power ultrasonic driving circuit model and describes the concepts and manners in detail of each subtle circuit in this circuit model. This circuit model can drive from hundreds of thousands to several millions hertz on the high power condition, and it has high conversion efficiency between mechanical terminals and electrical ones. Even though the application of ultrasonic atomization in engineering is more general and more important, it is rare to have a good ultrasonic atomization system with high efficiency and excellent atomization effect. As result, in this paper, we are going to apply this circuit model to the ultrasonic atomization system. This circuit can drive transducers with resonance frequency between 500KHz to 2MHz. Its output voltage can be adjusted and the maximum rated output power is 30W. Besides, we’re going to observe and discuss the atomization phenomenon of this atomizer, which includes the relationship between the sizes of droplet and driving frequency, the atomization velocity, and the relationship between the droplet size distribution and the driving voltage.