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Artykuły w czasopismach na temat "Atomization and Sprays"
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Panão, Miguel. "Ultrasonic Atomization: New Spray Characterization Approaches". Fluids 7, nr 1 (7.01.2022): 29. http://dx.doi.org/10.3390/fluids7010029.
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In particle engineering, spray drying is an essential technique that depends on producing sprays, ideally made of equal-sized droplets. Ultrasonic sprays appear to be the best option to achieve it, and Faraday waves are the background mechanism of ultrasonic atomization. The characterization of sprays in this atomization strategy is commonly related to the relation between characteristic drop sizes and the capillary length produced by the forcing frequency of wavy patterns on thin liquid films. However, although this atomization approach is practical when the intended outcome is to produce sprays with droplets of the same size, drop sizes are diverse in real applications. Therefore, adequate characterization of drop size is paramount to establishing the relations between empirical approaches proposed in the literature and the outcome of ultrasonic atomization in actual operating conditions. In this sense, this work explores new approaches to spray characterization applied to ultrasonic sprays produced with different solvents. The first two introduced are the role of redundancy in drop size measurements to avoid resolution limitation in the measurement technique and compare using regular versus variable bin widths when building the histograms of drop size. Another spray characterization tool is the Drop Size Diversity to understand the limitations of characterizing ultrasonic sprays solely based on representative diameters or moments of drop size distributions. The results of ultrasonic spray characterization obtained emphasize: the lack of universality in the relation between a characteristic diameter and the capillary length associated with Faraday waves; the variability on drop size induced by both liquid properties and flow rate on the atomization outcome, namely, lower capillary lengths produce smaller droplets but less efficiently; the higher sensibility of the polydispersion and heterogeneity degrees in Drop Size Diversity when using variable bin widths to build the histograms of drop size; the higher drop size diversity for lower flow rates expressed by the presence of multiple clusters of droplets with similar characteristics leading to multimodal drop size distributions; and the gamma and log-normal mathematical probability functions are the ones that best describe the organization of drop size data in ultrasonic sprays.
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Arrowsmith, A. "Atomization and Sprays." Chemical Engineering Science 45, nr 5 (1990): 1435. http://dx.doi.org/10.1016/0009-2509(90)87140-n.
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Ding, Hong Yuan, Peng Deng, Xu Yao Mao i Chao Wu. "Flash Boiling Spray Simulation Based on Void Fraction and Superheat Controlling". Applied Mechanics and Materials 737 (marzec 2015): 289–95. http://dx.doi.org/10.4028/www.scientific.net/amm.737.289.
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A new flash boiling spray model whose atomization criterion based on the void fraction and superheat while evaporation model based on the dual-zone method is established to simulate the flashing sprays. The model function is implemented in KIVA program. Flash boiling spray model predicts spray penetration and spray cone angle and its development trend, in good agreement with the experimental results. The model has a good capability in simulating flash sprays at low superheat conditions, which breakup is controlled by void fraction, as well as high superheat transition process. It can also predict flare flashing sprays to some extent at higher superheat conditions.
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Prasad, Arvind, i Hani Henein. "Droplet cooling in atomization sprays". Journal of Materials Science 43, nr 17 (wrzesień 2008): 5930–41. http://dx.doi.org/10.1007/s10853-008-2860-2.
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Hu, Zuxiang, Benyi Zhang i Haoqian Chang. "A Study on Dust-Control Technology Used for Large Mining Heights Based on the Optimization Design of a Tracking Spray Nozzle". Atmosphere 14, nr 4 (26.03.2023): 627. http://dx.doi.org/10.3390/atmos14040627.
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Intense cutting-induced dust production in fully mechanized mining faces (FMMFs) with large mining heights produces a high amount of dust that is difficult to capture and severely affects the working environment, threatening the health of occupational staff. The effective spray range and atomization performance of tracking sprays are counteracted by the influences of the mine’s height and ventilation airflow in FMMFs. Thus, optimizing the spray’s parameters and relationship between the effective spray range and atomization performance to reduce dust levels is the main priority of dust-control techniques. In this study, a new swirl-core atomization nozzle is developed based on fluid mechanics and the solid–liquid coalescence mechanism. The liquid generates a circumferential velocity when passing through the swirl core, which considerably increases the droplet breaking power and reduces the droplet cohesion factor, achieving a remarkable atomization effect. The spray angle of the new nozzle is 57°, which is 80.9% greater than the GZPW-16 mine-use nozzle (31.5°); the effective spray range increases from 5.2 to 5.9 m; and the spray’s mist saturation is significantly better than the GZPW-16 mine-use nozzle. Under different test pressures, the particle size range of the droplets produced by the new nozzle and dust particles on site satisfied the best synergy of droplet–dust coalescence. The total and respirable dust-reduction rates were 78% and 75.1%, respectively, which were 42% and 65% higher than those of the original nozzle. The new nozzle effectively improves the efficiency of the single dust-control technique of the tracking spray, which is significant for the dust-prevention and -control technology of FMMFs with large mining heights.
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Sparacino, Berni, d’Adamo, Krastev, Cavicchi i Postrioti. "Impact of the Primary Break-Up Strategy on the Morphology of GDI Sprays in 3D-CFD Simulations of Multi-Hole Injectors". Energies 12, nr 15 (26.07.2019): 2890. http://dx.doi.org/10.3390/en12152890.
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The scientific literature focusing on the numerical simulation of fuel sprays is rich in atomization and secondary break-up models. However, it is well known that the predictive capability of even the most diffused models is affected by the combination of injection parameters and operating conditions, especially backpressure. In this paper, an alternative atomization strategy is proposed for the 3D-Computational Fluid Dynamics (CFD) simulation of Gasoline Direct Injection (GDI) sprays, aiming at extending simulation predictive capabilities over a wider range of operating conditions. In particular, attention is focused on the effects of back pressure, which has a remarkable impact on both the morphology and the sizing of GDI sprays. 3D-CFD Lagrangian simulations of two different multi-hole injectors are presented. The first injector is a 5-hole GDI prototype unit operated at ambient conditions. The second one is the well-known Spray G, characterized by a higher back pressure (up to 0.6 MPa). Numerical results are compared against experiments in terms of liquid penetration and Phase Doppler Anemometry (PDA) data of droplet sizing/velocity and imaging. CFD results are demonstrated to be highly sensitive to spray vessel pressure, mainly because of the atomization strategy. The proposed alternative approach proves to strongly reduce such dependency. Moreover, in order to further validate the alternative primary break-up strategy adopted for the initialization of the droplets, an internal nozzle flow simulation is carried out on the Spray G injector, able to provide information on the characteristic diameter of the liquid column exiting from the nozzle.
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Mohandas, Anu, Hongrong Luo i Seeram Ramakrishna. "An Overview on Atomization and Its Drug Delivery and Biomedical Applications". Applied Sciences 11, nr 11 (2.06.2021): 5173. http://dx.doi.org/10.3390/app11115173.
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Atomization is an intricate operation involving unstable and complex networks with rupture and fusion of liquid molecules. There are diverse details that typify the spray formation, which are the technique and configuration of the atomization process, dimension and structure of the nozzle, experimental parameters, etc. Ultimately, the process generates fine sprays from the bulk of a liquid. Some examples of atomization that we come across in our day-to-day life are antiperspirant or hair spray, shower head, garden sprinkler, or cologne mist. In this review paper we are briefly discussing the theoretical steps taking place in an atomization technique. The instabilities of the jet and sheet are explained to understand the underlying theory that breaks the jet or sheet into droplets. Different types of atomization processes based on the energy sources are also summarized to give an idea about the advantages and disadvantages of these techniques. We are also discussing the various biomedical applications of the electrohydrodynamic atomization and its potential to use as a drug delivery system. In short, this paper is trying to demonstrate the diverse applications of atomization to show its potency as a user friendly and cost-effective technique for various purposes.
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Balasubramanyam, M. S., C. P. Chen i H. P. Trinh. "A New Finite-Conductivity Droplet Evaporation Model Including Liquid Turbulence Effect". Journal of Heat Transfer 129, nr 8 (7.12.2006): 1082–86. http://dx.doi.org/10.1115/1.2737481.
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A new approach to account for finite thermal conductivity and turbulence effects within atomizing droplets of an evaporating spray is presented in this paper. The model is an extension of the T-blob and T-TAB atomization/spray model of Trinh and Chen [Atomization and Sprays, 16(6), pp. 907–932]. This finite conductivity model is based on the two-temperature film theory in which the turbulence characteristics of the droplet are used to estimate the effective thermal diffusivity for the liquid-side film thickness. Both one-way and two-way coupled calculations were performed to investigate the performance of this model against the published experimental data.
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Manna, Lucia, Claudia Carotenuto, Roberto Nigro, Amedeo Lancia i Francesco Di Natale. "Primary atomization of electrified water sprays". Canadian Journal of Chemical Engineering 95, nr 9 (11.04.2017): 1781–88. http://dx.doi.org/10.1002/cjce.22841.
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Post, Scott L., i Andrew J. Hewitt. "Flat-Fan Spray Atomization Model". Transactions of the ASABE 61, nr 4 (2018): 1249–56. http://dx.doi.org/10.13031/trans.12572.
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Abstract. In pesticide application, the lack of a suitable theoretical atomization model for flat-fan spray nozzles forces a reliance on empirical data and correlations, even for computational simulations. There is considerable difficulty in the theoretical analysis of the liquid sheet emanating from flat-fan nozzles because no simplification to a two-dimensional analysis can be employed, as is done for cylindrical jets. Nonetheless, 50 years ago, Dombrowski and co-workers used linear stability analysis to analyze the breakup of flat-fan spray sheets into ligaments and from ligaments to droplets. Their correlations have not found use because they include parameters that are difficult, if not impossible, to measure. In this work, the Dombrowski model is simplified using dimensional analysis, resulting in a correlation to predict the volume median diameter of flat-fan sprays in terms of common user parameters, i.e., the nozzle size and operating pressure. Keywords: Atomization, Droplet size, Nozzles, Pesticides, Sprayers.
Rozprawy doktorskie na temat "Atomization and Sprays"
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Singh, Gajendra. "Atomization and Combustion Characterization of Sprays". Thesis, University of Sydney, 2020. https://hdl.handle.net/2123/23135.
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This thesis presents an extensive study of turbulent air-blasted sprays aimed at advancing the current understanding of the atomization and the turbulent combustion of dense sprays. The burner employed controls the spray quality by recessing the liquid-injecting needle inside the air-blast tube to transition the spray from dilute to dense. A pilot is used to stabilize the flame to the burner which is sitting in a co-flowing stream of secondary air. Three fuels, acetone, ethanol, and biodiesel, are used to generate several sprays that cover a broad range of non-dimensional numbers. Probability distributions of wavelength and amplitude of instabilities forming on coaxial air-blast atomizers are measured directly using high-speed shadowgraphs (or back-lit microscopic imaging), in a range of cases that investigate the independent effects of a suite of parameters. The influence of jet velocity and gas velocity on the initiation and growth of jet instabilities is discussed. The range of mechanisms governing the formation of liquid fragments and their relation to surface instabilities is discussed. Previous work suggested that the mean wavelength scales with the boundary layer thickness. This is confirmed here and extended to demonstrate that the wavelength probability distribution correlates well with the ligament length probability distribution. This establishes a direct link between interfacial instabilities and ligament formation in air-assisted primary atomization. The complete structure of atomizing liquid fragments is analyzed by employing multi-dimensional visualization techniques and advanced image processing, where objects from multiple views are matched to extract three-dimensional information. An in-house MATLAB script is developed to extract the spray volume, which employs the principle of image discretization, where each image is divided into a number of slices, and the individual slice from each camera is matched to compute the liquid volume fraction in each image. The volume of individual objects is calculated based on their planar area and orientation. An error analysis is performed using dozens of three-dimensional virtual models of fragment-like shapes with a known volume. Local characteristics of atomizing fragments are discussed by using the information obtained through the slicing method. A detailed account of fragment statistics are provided for the atomizing sprays. The LIF-OH-CH2O technique is used to measure the product of OH and CH2O ([OH]*[CH2O]) and hence the heat release zones in turbulent, moderately dense spray flames of ethanol and biodiesel fuels. A combination of several filters is used to remove interference from droplet luminosity. Mie scattering is measured jointly on a separate camera to locate the droplets with respect to the reaction zones. It is found that while the overall flame structure is similar to that of a diffusion flame. Structures referred to as burning rings of different sizes are observed, and these are ignited by heat source before they grow, propagate, and burnout. Statistics about the occurrence of these rings, with and without clouds of fragments within them, are presented. Occurrences of single-droplet combustion are also noted. Overall this thesis expands the current understanding of the primary and secondary atomization zones and provides new insights into the turbulent combustion characteristics of denser sprays. An extensive and novel data set in generated, and this will be made available to modelers with the aim of changing the predictive capability of both atomization and combustion of such flows.
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Ahmed, Tushar. "Atomization and Combustion of Hybrid Electrohydrodynamic-Air-Assisted Sprays". Thesis, The University of Sydney, 2022. https://hdl.handle.net/2123/28180.
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This thesis presents an extensive study of the atomization and combustion of dielectric liquids using a hybrid air-blast electrostatic atomizer. While airblast atomization relies on the shear stresses generated at the liquid-air interface, electrostatic atomization introduces an electric charge into the bulk liquid, and the resulted Coulombic repulsive force facilitates the fragmentation process. The atomizer introduced in this contribution is specifically designed to operate in either a single (air-blast or electrostatic) or hybrid mode to enable the delivery of a charged and/or air-assisted spray for combustion applications. The aim is to understand the effect of adding electric charge to a liquid jet which is subject to break up in a co-flowing air stream. In addition to analysis of atomization processes, the influence of charge on flame structure is also analyzed. Laser diagnostics are utilized for measurements and the results obtained for the atomizer in hybrid mode (air-blast + electrostatic) are compared with the pure air-blast mode.
Firstly, a high-speed microscopic shadowgraphy technique is implemented to examine near-field spray structure. Diesel is used as a dielectric liquid to create various sprays that cover a range of non-dimensional numbers. The effect of charge on liquid jet unsteadiness and on the probability distribution of wavelength and amplitude of instabilities is discussed. The influence of charge on droplet and ligament size and their population is also analyzed. The findings show that the application of charge makes the liquid jet more unstable and the instabilities forming on the liquid core exhibit a shift to a shorter wavelength with a broadening in the probability distribution of wave amplitude. In addition, a droplet and ligament size reduction along with an increase in droplet count is observed with the addition of charge.
The thesis then progresses to discussing results from reacting sprays stabilized on a pilot where kerosene is chosen as the liquid. A premixed pilot flame is used to provide a steady heat source for stabilizing the hybrid atomized sprays. Flame stability characteristics, in terms of blow-off velocity, are presented as a function of controlling parameters, without and with charge. Downstream droplet statistics and flow field for both non-reacting and reacting sprays are shown using laser Doppler velocimetry/phase Doppler anemometry (LDV/PDA) revealing key features in the droplet fields from this burner. Due to relatively low spray specific charge for the aerodynamic Weber numbers investigated, the droplet size and velocity remained largely unaffected through the addition of charge, however, a rise in particle concentration at the center of the spray was noted.
Finally, high-speed hydroxyl planar laser induced fluorescence (OH-PLIF) is used to locate reaction zones and comment on the morphology of the reaction zone structures. In a hybrid mode, the charge was seen to push reaction zones radially outward and assisted in stabilizing the flame by keeping OH islands more connected when compared to a pure air-blast mode. This observation was also consistent with a slight improvement in flame stability with the addition of charge.
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BURROUGHS, ERIC WILLIAM. "DEVELOPMENT OF A HIGH-RESOLUTION MECHANICAL SPRAY PATTERNATOR FOR THE CHARACTERIZATION OF FUEL SPRAYS". University of Cincinnati / OhioLINK, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1132346171.
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Zaheer, Hussain. "Transient microscopy of primary atomization in gasoline direct injection sprays". Thesis, Georgia Institute of Technology, 2015. http://hdl.handle.net/1853/53611.
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Understanding the physics governing primary atomization of high pressure fuel sprays is of paramount importance to accurately model combustion in direct injection engines. The small length and time scales of features that characterize this process falls below the resolution power of typical grids in CFD simulations, which necessitates the inclusion of physical models (sub-models) to account for unresolved physics. Unfortunately current physical models for fuel spray atomization used in engine CFD simulations are based on significant empirical scaling because there is a lack of experimental data to understand the governing physics. The most widely employed atomization sub-model used in current CFD simulations assumes the spray atomization process to be dominated by aerodynamically-driven surface instabilities, but there has been no quantitative experimental validation of this theory to date. The lack of experimental validation is due to the high spatial and temporal resolutions required to simultaneously to image these instabilities, which is difficult to achieve.
The present work entails the development of a diagnostic technique to obtain high spatial and temporal resolution images of jet breakup and atomization in the near nozzle region of Gasoline Direct Injection (GDI) sprays. It focuses on the optical setup required to achieve maximum illumination, image contrast, sharp feature detection, and temporal tracking of interface instabilities for long-range microscopic imaging with a high-speed camera. The resolution and performance of the imaging system is characterized by evaluating its modulation transfer function (MTF). The setup enabled imaging of GDI sprays for the entire duration of an injection event (several milliseconds) at significantly improved spatial and temporal resolutions compared to historical spray atomization imaging data. The images show that low to moderate injection pressure sprays can be visualized with a high level of detail and also enable the tracking of features across frames within the field of view (FOV)
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Crialesi, Esposito Marco. "Analysis of primary atomization in sprays using Direct Numerical Simulation". Doctoral thesis, Universitat Politècnica de València, 2019. http://hdl.handle.net/10251/133975.
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[ES] La comprensión de los fenómenos físicos que acontecen en la región densa (también conocida como campo cercano) durante la atomización de los sprays ha sido una de las mayores incógnitas a la hora de estudiar sus aplicaciones. En el sector industrial, el rango de interés abarca desde toberas en aplicaciones propulsivas a sprays en aplicaciones médicas, agrícolas o culinarias. Esta evidente falta de conocimiento obliga a realizar simplificaciones en la modelización, provocando resultados poco precisos y la necesidad de grandes caracterizaciones experimentales en la fase de diseño. De esta manera, los procesos de rotura del spray y atomización primaria se consideran problemas físicos fundamentales, cuya complejidad viene dada como resultado de un flujo multifásico en un régimen altamente turbulento, originando escenarios caóticos.
El análisis de este problema es extremadamente complejo debido a la ausencia sustancial de teorías validadas referentes a los fenómenos físicos involucrados como son la turbulencia y la atomización. Además, la combinación de la naturaleza multifásica del flujo y su comportamiento turbulento resultan en una gran dificultad para afrontar el problema. Durante los últimos 10 años, las técnicas experimentales han sido finalmente capaces de visualizar la región densa, pero la confianza, análisis y efectividad de dichos experimentos en esta región del spray todavía requiere de mejoras sustanciales.
En este contexto, esta tesis trata de contribuir al entendimiento de estos procesos físicos y de proporcionar herramientas de análisis para estos flujos tan complejos. Para ello, mediante Direct Numerical Simulations se ha afrontado el problema resolviendo las escalas de movimiento más pequeñas, y capturando todas las escalas de turbulencia y eventos de rotura.
Uno de los objetivos de la tesis ha sido evaluar la influencia de las condiciones de contorno del flujo entrante en la atomización primaria y en el comportamiento turbulento del spray. Para ello, se han empleado dos condiciones de contorno diferentes. En primer lugar se ha empleado una condición de contorno sintética para producir turbulencia homogenea a la entrada, simulando el comporamiento de la tobera. Una de las características más interesantes de este método es la posibilidad de retocar los parámetros dentro del algoritmo. En particular, la escala de longitud integral se ha variado para evaluar la influencia de las estructuras mas grandes de la tobera en la atomización primaria.
El análisis de la condición de contorno sintética también ha permitido el diseño óptimo de simulaciones de las cuales se han derivado estadísticas turbulentas significativas. En este escenario, se han llevado a cabo estudios más profundos sobre la influencia de propiedades de las estructuras turbulentas como la homogeneidad y la anisotropía tanto en el espectro de los flujos como en las estadísticas de las gotas. Para tal fin, se han desarrollado metodologías novedosas para computar el análisis espectral y la estadística de las gotas
Entre los resultados de este análisis destaca la independencia de la condición de contorno de entrada en las estadísticas de las gotas, mientras que por otra parte, recalca que las características turbulentas desarrolladas en el interior de la tobera afectan a la cantidad total de masa atomizada. Estas consideraciones se encuentran respaldadas por el análisis espectral realizado, mediante el cuál se concluye que la turbulencia multifásica comparte el comportamiento universal descrito por las teorías de Kolmogorov.[CAT] La comprensió dels fenòmens físics que succeïxen en la regió densa (també coneguda com a camp pròxim) durant l'atomització dels sprays ha sigut una de les majors incògnites a l'hora d'estudiar les seues aplicacions. En el sector industrial, el rang d'interés comprén des de toveres en aplicacions propulsives a sprays en aplicacions mèdiques, agrícoles o culinàries. Esta evident falta de coneixement obliga a realitzar simplificacions en la modelització, provocant resultats poc precisos i la necessitat de grans caracteritzacions experimentals en la fase de disseny. D'esta manera, els processos de ruptura del spray i atomització primària es consideren problemes físics fonamentals, la complexitat dels quals ve donada com resultat d'un flux multifàsic en un règim altament turbulent, originant escenaris caòtics. L'anàlisi d'este problema és extremadament complex a causa de l'absència substancial de teories validades dels fenòmens físics involucrats com són la turbulència i l'atomització. A més, la combinació de la naturalesa multifàsica del flux i el seu comportament turbulent resulten en una gran dificultat per a afrontar el problema. Durant els últims 10 anys les tècniques experimentals han sigut finalment capaces de visualitzar la regió densa, però la confiança, anàlisi i efectivitat dels experiments en esta regió del spray encara requerix de millores substancials. En este context, esta tesi tracta de contribuir en l'enteniment d'estos processos físics i de proporcionar ferramentes d'anàlisi per a estos fluxos tan complexos. Per a això, per mitjà de Direct Numerical Simulations s'ha afrontat el problema resolent les escales de moviment més menudes, al mateix temps que es capturen totes les escales de turbulència i esdeveniments de ruptura. Un dels objectius de la tesi ha sigut avaluar la influència que les condicions de contorn del flux entrant tenen en l'atomització primària i en el comportament turbulent del spray. Per a això, s'han empleat dos condicions de contorn diferents. En primer lloc s'ha empleat una condició de contorn sintètica per a produir turbulència homogènia a l'entrada, simulant el comportament de la tovera. Una de les característiques més interessants d'este mètod és la possibilitat de retocar els paràmetres dins de l'algoritme. En particular, l'escala de longitud integral s'ha variat per a avaluar la influència de les estructures mes grans de la tovera en l'atomització primària. L'anàlisi de la condició de contorn sintètica també ha permés el disseny òptim de simulacions de les quals s'han derivat estadístiques turbulentes significatives. En este escenari, s'han dut a terme estudis més profunds sobre la influència de propietats de les estructures turbulentes com l'homogeneïtat i l'anisotropia tant en l'espectre dels fluxos com en les estadístiques de les gotes. Per a tal fi, s'han desenrotllat metodologies noves per a computar l'anàlisi espectral i l'estadística de les gotes. Entre els resultats d'esta anàlisi destaca la independència de la condició de contorn d'entrada en les estadístiques de les gotes, mentres que d'altra banda, es recalca que les característiques turbulentes desenrotllades en l'interior de la tovera afecten a la quantitat total de massa atomitzada. Estes consideracions es troben recolzades per l'anàlisi espectral realitzat, per mitjà del qual es conclou que la turbulència multifásica compartix el comportament universal descrit per les teories de Kolmogorov.
[EN] The understanding of the physical phenomena occurring in the dense region (also known as near field) of atomizing sprays has been long seen as one of the biggest unknown when studying sprays applications. The industrial range of interest goes from nozzles in combustion and propulsion applications to medical sprays, agricultural and food process applications. This substantial lack of knowledge is responsible for some important simplification in modeling, that often result to be inaccurate or simply partial, leading to the evident need of large experimental characterization during the design phase. In fact, the spray breakup and primary atomization processes are indeed fundamental problems of physics, which complexity results from the combination of a multiphase flow in a highly turbulent regime that leads to chaotic scenarios. The analysis of this problem is extremely problematic, due to a substantial lack of definitive theories about the physical phenomena involved, namely turbulence and atomization. Furthermore, the combination of the multiphase nature of the flow and its turbulent behavior makes substantially difficult to address the problem. Only within the last 10 years, experimental techniques have been capable of visualizing the dense region, but the experiments reliability, analysis and effectiveness in this region still requires vast improvements. In this scenario, this thesis aims to contribute in the understanding of these physical process and to provide analysis tools for these complex flows. In order to do so, Direct Numerical Simulations have been used for addressing the problem at its smallest scale of motion, while reliably capturing all turbulence scales and breakup events. The multiphase nature of the flow is accounted for by using the Volume of Fluid method. One of the goal of the thesis was to assess the influence of the inflow boundary conditions on the primary atomization and on the spray's turbulence behavior. In order to do so, two different boundary conditions were used. In a first place, a synthetic inflow boundary condition was used in order to produce a homogeneous turbulence inflow, simulating the nozzle behavior. One of the interesting features of this method was the possibility of tweaking the parameters within the algorithm. In particular, the integral length scale was varied in order to assess the influence of nozzle larger turbulent structures on the primary atomization. The analysis on the synthetic boundary condition also allowed to optimally design simulations from which derive meaningful turbulence statistics. On this framework, further studies were carried over on the influence of turbulent structures properties, namely homogeneity and anisotropy, on both the flows spectra and droplets statistics. In order to achieve this goal, novel procedures for both computing the flow spectra and analyzing droplets were developed and are carefully addressed in the thesis. The results of the analysis highlight the independence of droplets statistics from the inflow boundary condition, while, on the other hand, remarking how the total quantity of atomized mass is significantly affected by the turbulence features developed within the nozzle. This considerations are supported by the spectrum analysis performed, which also highlighted how multiphase turbulence shares the universal features described in Kolmogorov theories.
Crialesi Esposito, M. (2019). Analysis of primary atomization in sprays using Direct Numerical Simulation [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/133975
TESIS
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Khuong, Anh Dung. "The Eulerian-Lagrangian Spray Atomization (ELSA) Model of the Jet Atomization in CFD Simulations: Evaluation and Validation". Doctoral thesis, Universitat Politècnica de València, 2012. http://hdl.handle.net/10251/17237.
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Fuel sprays play a major role in order to achieve the required combustion characteristics and pollutant emissions reduction on internal combustion engines, and thus, an accurate prediction of its behavior is required to perform reliable engine combustion and pollutant simulations. A great effort both on experimental and theoretical studies of spray atomization and dispersion has been performed in the latest years. As a result, Computational Fluid Dynamics (CFD) calculations have become a standard tool not only for spray physics understanding but also for design and optimization of engine spray systems.
However, spray modeling in its different uses in the Internal Combustion Engine (ICE) context is still nowadays a challenging task due to the complex interrelated phenomena taking place, some of them still not fully understood. Primary atomization and secondary breakup, droplet collision, coalescence and vaporization, turbulent interactions between phases have to be solved under high Reynolds (so they are turbulent) and Weber numbers conditions due to the high speed (~500 m/s) and small nozzle diameter (~100 µm) imposed by current engine injection systems technologies. Moreover, Taylor numbers cover a wide range, according to the composition of the injected liquid. Those conditions make experimental observations quite challenging and probably insufficient, especially in the very near nozzle region, where primary atomization takes place.
Most of the CFD spray models are currently based on the Discrete Droplet Method. The continuous liquid jet is discretized into 'blobs' or 'parcels', which consists in a number of droplets with the same characteristics. A Lagrangian method is applied to track the liquid phase parcels, which are subject to breakup according to atomization models mainly based on the linear instability theory proposed by Reitz and later extended by Huh and Gosman for liquid turbulence effects to be considered. This approach has been successfully applied bKhuong ., AD. (2012). The Eulerian-Lagrangian Spray Atomization (ELSA) Model of the Jet Atomization in CFD Simulations: Evaluation and Validation [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/17237
Palancia
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Abbas, Fakhar. "Numerical Studies of Spray Atomization for Multiphase Flows". Thesis, The University of Sydney, 2022. https://hdl.handle.net/2123/29953.
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The current study aims to investigate and develop numerical tools for the simulation of interfacial flows, including those with turbulence and primary spray atomization. In the past, many approaches were developed to track the interface of a multi-phase/immiscible flow system. Two of them, the volume of fluid (VoF) and the level set (LS), have shown promising findings and have been considered a benchmark for further research. VoF methods have proved good mass conservation behaviour during the advection of solution. However, LS methods have shown better interface representation when used for the calculations of interfacial flows. Most of the recent development in this context either originated from VoF, LS or a combination of both.
In the first part of this thesis importance of the current study is highlighted in detail, and an overview of the recent developments for the numerical solutions of immiscible flows is presented. A detailed description of interface-capturing methods and their development over time is presented in a systematic way, leading to the issues addressed in this study. A stochastic field PDF-LES solution of the VoF approach is analyzed against the Sydney needle spray measurements. Solution behaviour for different combinations of stochastic fields and LES grid cells are examined in detail.
In the second part of this work, three different LES treatment for unresolved sub-grid fluctuations, TFVoF, TF-AC and newly developed EVD, has been presented. The performance analysis of two already existing solutions, TFVoF and TF-AC, is compared with the EVD approach. Sydney needle spray measurements are used as a benchmark for this comparison. The suitability of the EVD approach is also tested for different flow conditions. Simulation results confirm that sub-grid surface tension plays an important role in the realistic prediction of the jet decay rate, and proper closure models to account for sub-grid surface tension are very necessary. An already existing sub-grid surface tension closure model is incorporated into OpenFOAM and tested for all three LES filtered solutions.
The findings of this work suggest that the newly developed EVD approach has shown promising improvements to produce more reliable and realistic solutions for multi-phase flow
applications. Sub-volume surface tension closure model, following the EVD formulation, is helpful for more accurate jet decay rate predictions.
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Dyson, Joshua. "GPU accelerated linear system solvers for OpenFOAM and their application to sprays". Thesis, Brunel University, 2018. http://bura.brunel.ac.uk/handle/2438/16005.
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This thesis presents the development of GPU accelerated solvers for use in simulation of the primary atomization phenomenon. By using the open source continuum mechanics library, OpenFOAM, as a basis along with the NVidia CUDA API linear system solvers have been developed so that the multiphase solver runs in part on GPUs. This aims to reduce the enormous computational cost associated with modelling primary atomization. The modelling of such is vital to understanding the mechanisms that make combustion efficient. Firstly, the OpenFOAM code is benchmarked to assess both its suitability for atomization problems and to establish efficient operating parameters for comparison to GPU accelerations. This benchmarking then culminates in a comparison to an experimental test case, from the literature, dominated by surface tension, in 3D. Finally, a comparison is made with a primary atomizing liquid sheet as published in the literature. A geometric multigrid method is employed to solve the pressure Poisson equations, the first use of a geometric multigrid method in 3D GPU accelerated VOF simulation. Detailed investigations are made into the compute efficiency of the GPU accelerated solver, comparing memory bandwidth usage to hardware maximums as well as GPU idling time. In addition, the components of the multigrid method are also investigated, including the effect of residual scaling. While the GPU based multigrid method shows some improvement over the equivalent CPU implementation, the costs associated with running on GPU cause this to not be significantly greater.
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Pandal, Blanco Adrián. "Implementation and Development of an Eulerian Spray Model for CFD simulations of diesel Sprays". Doctoral thesis, Universitat Politècnica de València, 2016. http://hdl.handle.net/10251/68490.
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[EN] The main objective of this work is the modeling of diesel sprays under engine conditions, including the atomization, transport and evaporation processes pivotal in the diesel spray formation and its development. For this purpose, an Eulerian single fluid model, embedded in a RANS environment, is implemented in the CFD platform OpenFOAM.
The modeling approach implemented here is based on the ⅀-Y model. The model is founded on the assumption of flow scales separation. In actual injection systems, it can be assumed that the flow exiting the nozzle is operating at large Reynolds and Weber numbers and thus, it is possible to assume a separation of features such as mass transport (large scales) from the atomization process occurring at smaller scales. The liquid/gas mixture is treated as a pseudo-fluid with variable density and which flows with a single velocity field. Moreover, the mean geometry of the liquid structures can be characterized by modeling the mean surface area of the liquid-gas interphase per unit of volume. Additionally, an evaporation model has been developed around the particular characteristics of the current engine technologies. This means that vaporization process is limited by fuel-air mixing rate and fuel droplets evaporate as long as there is enough air for them to heat up and vaporize. Consequently, the evaporation model is based on the Locally Homogeneous Flow (LHF) approach. Under the assumption of an adiabatic mixing, in the liquid/vapor region, the spray is supposed to have a trend towards adiabatic saturation conditions and to determine this equilibrium between phases Raoult's ideal law is considered. Finally, the spray model is coupled with an advanced combustion model based on approximated diffusion flames (ADF), which reduces the computational effort especially for complex fuels and is a natural step for modeling diesel sprays.
First, the model is applied to a basic external flow case under non-vaporizing conditions, extremely convenient due to both the experimental database available and the symmetric layout which allows important simplification of the modeling effort. Good agreement between computational results and experimental data is observed, which encourages its application to a more complex configuration. Secondly, the model is applied to the "Spray A" from the Engine Combustion Network (ECN), under non-vaporizing conditions, in order to reproduce the internal structure of diesel sprays as well as to produce accurate predictions of SMD droplets sizes. Finally, vaporizing "Spray A" studies are conducted together with the baseline reacting condition of this database. The calculated spray penetration, liquid length, spray velocities, ignition delay and lift-off length are compared with experimental data and analysed in detail.[ES] El objetivo principal de este trabajo es el modelado de chorros diésel en condiciones de motor, incluyendo los fenómenos de atomización, transporte y evaporación fundamentales en la formación y desarrollo del chorro. Para este fin, se implementa un modelo de spray euleriano de tipo monofluido en un entorno RANS en la plataforma CFD OpenFOAM. El enfoque de modelado aplicado aquí sigue la idea de un modelo del tipo ⅀-Y. El modelo se fundamenta en la hipótesis de separación de escalas del flujo. En los sistemas de inyección actuales, es posible asumir que el flujo que sale de la tobera opera a altos números de Reynolds y Webber y por tanto, es posible considerar la independencia de fenómenos como el transporte de masa (grandes escalas del flujo) de los procesos de atomización que ocurren a escalas menores. La mezcla líquido/gas se trata como un pseudo-fluido con densidad variable y que fluye según un único campo de velocidad. Además, la geometría promedio de las estructuras de líquido se puede caracterizar mediante el modelado de la superficie de la interfase líquido/gas por unidad de volumen. Completando el modelo de chorro, se ha desarrollado un modelo de evaporación alrededor de las características particulares de las tecnologías actuales de los motores. Esto supone que el proceso de evaporación está controlado por mezcla aire-combustible y las gotas de combustible se evaporan siempre que exista suficiente aire para calentarlas y evaporarlas. Debido a esto, el modelo de evaporación implementado está basado en el enfoque de Flujos Localmente Homogéneos (LHF). Considerando una mezcla adiabática, en la región líquido/vapor, se supone que el chorro tiende a las condiciones adiabáticas de saturación y para determinar este equilibrio entre fases, se utiliza la ley ideal de Raoult. Finalmente, el modelo de chorro se acopla con un modelo avanzado de combustión basado en llamas de difusión aproximadas (ADF), que reduce el coste computacional especialmente para combustibles complejos y supone el paso lógico en el desarrollo del modelo para simular chorros diesel. En primer lugar, el modelo se aplica al cálculo de un caso básico de flujo externo no evaporativo, muy adecuado tanto por la extensa base de datos experimentales disponible como por la simetría geométrica que presenta, permitiendo una importante simplificación de la simulación. Los resultados obtenidos presentan un buen acuerdo con los experimentos, lo cual estimula su aplicación en configuraciones más complejas. En segundo lugar, el modelo se aplica al cálculo del "Spray A" del Engine Combustion Network (ECN), no evaporativo, para reproducir la estructura interna del chorro diesel así como predecir tamaños de gota (SMD) de forma precisa. Finalmente, se realizan estudios evaporativos del "Spray A" junto con la condición nominal reactiva de esta base de datos. La penetración de vapor, la longitud líquida, velocidad, el tiempo de retraso y la longitud de despegue de llama calculados se comparan con los datos experimentales y se analizan en detalle.
[CAT] L'objectiu principal d'aquest treball és el modelatge de dolls dièsel en condicions de motor, incloent els fenòmens d'atomització, transport i evaporació fonamentals en la formació i desenvolupament del doll. Amb aquesta finalitat, s'implementa un model de doll eulerià de tipus monofluid en un entorn RANS a la plataforma CFD OpenFOAM. L'enfocament de modelatge aplicat ací segueix la idea d'un model del tipus ⅀-Y. El model es fonamenta en la hipòtesi de separació d'escales del flux. En els sistemes d'injecció actuals, és possible assumir que el flux que surt de la tovera opera a alts nombres de Reynolds i Webber, i per tant és possible considerar la independència de fenòmens com el transport de massa (grans escales del flux) dels processos d'atomització que ocorren a escales menors. La mescla líquid / gas es tracta com un pseudo-fluid amb densitat variable i que flueix segons un únic camp de velocitat. A més, la geometria mitjana de les estructures de líquid es pot caracteritzar mitjançant el modelatge de la superfície de la interfase líquid / gas per unitat de volum. Completant el model, s'ha desenvolupat un model d'evaporació al voltant de les característiques particulars de les tecnologies actuals dels motors. Això suposa que el procés d'evaporació està controlat per la mescla aire-combustible i les gotes de combustible s'evaporen sempre que hi hagi suficient aire per escalfar i evaporar. A causa d'això, el model d'evaporació implementat està basat en el plantejament de fluxos Localment Homogenis (LHF). Considerant una mescla adiabàtica, a la regió líquid / vapor, se suposa que el doll tendeix a les condicions adiabàtiques de saturació i per determinar aquest equilibri entre fases, s'utilitza la llei ideal de Raoult. Finalment, el model de doll s'acobla amb un model avançat de combustió basat en flamelets de difusió aproximades (ADF), que redueix el cost computacional especialment per a combustibles complexos i suposa el pas lògic en el desenvolupament del model per simular dolls dièsel. En primer lloc, el model s'aplica al càlcul d'un cas bàsic de flux extern no evaporatiu, molt adequat tant per l'extensa base de dades experimentals disponible com per la simetria geomètrica que presenta, permetent una important simplificació de la simulació. Els resultats obtinguts presenten un bon acord amb els experiments, la qual cosa estimula la seva aplicació en configuracions més complexes. En segon lloc, el model s'aplica al càlcul del "Spray A" no evaporatiu de la xarxa Engine Combustion Network (ECN), per reproduir l'estructura interna del doll dièsel així com predir mides de gota (SMD) de forma precisa. Finalment, es realitzen estudis evaporatius del "Spray A" juntament amb la condició nominal reactiva d'aquesta base de dades. La penetració de vapor, la longitud líquida, velocitat, el temps de retard i la longitud d'enlairament de flama calculats es comparen amb les dades experimentals i s'analitzen en detall.
Pandal Blanco, A. (2016). Implementation and Development of an Eulerian Spray Model for CFD simulations of diesel Sprays [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/68490
TESIS
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Vu, Henry H. "Thermo-fluid dynamics of flash atomizing sprays and single droplet impacts". Diss., [Riverside, Calif.] : University of California, Riverside, 2010. http://proquest.umi.com/pqdweb?index=0&did=2019869981&SrchMode=2&sid=4&Fmt=2&VInst=PROD&VType=PQD&RQT=309&VName=PQD&TS=1274205996&clientId=48051.
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Thesis (Ph. D.)--University of California, Riverside, 2010.Includes abstract. Available via ProQuest Digital Dissertations. Title from first page of PDF file (viewed May 18, 2010). Includes bibliographical references. Also issued in print.
Książki na temat "Atomization and Sprays"
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Lefebvre, Arthur H., i Vincent G. McDonell. Atomization and Sprays. Second edition. | Boca Raton : Taylor & Francis, CRC Press, 2017.: CRC Press, 2017. http://dx.doi.org/10.1201/9781315120911.
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Atomization and sprays. New York: Hemisphere Pub. Corp., 1989.
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Nasr, G. G., A. J. Yule i L. Bendig. Industrial Sprays and Atomization. London: Springer London, 2002. http://dx.doi.org/10.1007/978-1-4471-3816-7.
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Ashgriz, Nasser, red. Handbook of Atomization and Sprays. Boston, MA: Springer US, 2011. http://dx.doi.org/10.1007/978-1-4419-7264-4.
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Alan, Williams. Combustion of liquid fuel sprays. London [England]: Butterworths, 1989.
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J, Sutherland J., i United States. Environmental Protection Agency., red. Entrainment by low air-liquid ratio effervescent atomizer produced sprays. [Washington, D.C.?: U.S. Environmental Protection Agency, 1996.
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H, Chiu H., i Chigier N. A, red. Mechanics and combustion of droplets and sprays. New York: Begell House, 1995.
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Center, Lewis Research, red. LOX/hydrogen coaxial injector atomization test program. [Cleveland, Ohio]: National Aeronautics and Space Administration, Lewis Research Center, 1990.
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United States. National Aeronautics and Space Administration., red. Characteristics of vaporizing cryogenic sprays for rocket combustion modeling. [Washington, DC]: National Aeronautics and Space Administration, 1994.
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United States. National Aeronautics and Space Administration., red. Characteristics of vaporizing cryogenic sprays for rocket combustion modeling. [Washington, DC]: National Aeronautics and Space Administration, 1994.
Znajdź pełny tekst źródłaCzęści książek na temat "Atomization and Sprays"
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Bogno, Abdoul-Aziz, Hani Henein, Volker Uhlenwinkel i Eric Gärtner. "Single Fluid Atomization Fundamentals". W Metal Sprays and Spray Deposition, 9–48. Cham: Springer International Publishing, 2017. http://dx.doi.org/10.1007/978-3-319-52689-8_2.
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Anderson, Iver E., i Lydia Achelis. "Two Fluid Atomization Fundamentals". W Metal Sprays and Spray Deposition, 49–88. Cham: Springer International Publishing, 2017. http://dx.doi.org/10.1007/978-3-319-52689-8_3.
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Lefebvre, Arthur H., i Vincent G. McDonell. "General Considerations". W Atomization and Sprays, 1–16. Second edition. | Boca Raton : Taylor & Francis, CRC Press, 2017.: CRC Press, 2017. http://dx.doi.org/10.1201/9781315120911-1.
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Lefebvre, Arthur H., i Vincent G. McDonell. "Basic Processes in Atomization". W Atomization and Sprays, 17–54. Second edition. | Boca Raton : Taylor & Francis, CRC Press, 2017.: CRC Press, 2017. http://dx.doi.org/10.1201/9781315120911-2.
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Lefebvre, Arthur H., i Vincent G. McDonell. "Drop Size Distributions of Sprays". W Atomization and Sprays, 55–70. Second edition. | Boca Raton : Taylor & Francis, CRC Press, 2017.: CRC Press, 2017. http://dx.doi.org/10.1201/9781315120911-3.
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Lefebvre, Arthur H., i Vincent G. McDonell. "Atomizers". W Atomization and Sprays, 71–104. Second edition. | Boca Raton : Taylor & Francis, CRC Press, 2017.: CRC Press, 2017. http://dx.doi.org/10.1201/9781315120911-4.
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Lefebvre, Arthur H., i Vincent G. McDonell. "Flow in Atomizers". W Atomization and Sprays, 105–32. Second edition. | Boca Raton : Taylor & Francis, CRC Press, 2017.: CRC Press, 2017. http://dx.doi.org/10.1201/9781315120911-5.
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Lefebvre, Arthur H., i Vincent G. McDonell. "Atomizer Performance". W Atomization and Sprays, 133–82. Second edition. | Boca Raton : Taylor & Francis, CRC Press, 2017.: CRC Press, 2017. http://dx.doi.org/10.1201/9781315120911-6.
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Lefebvre, Arthur H., i Vincent G. McDonell. "External Spray Characteristics". W Atomization and Sprays, 183–205. Second edition. | Boca Raton : Taylor & Francis, CRC Press, 2017.: CRC Press, 2017. http://dx.doi.org/10.1201/9781315120911-7.
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Lefebvre, Arthur H., i Vincent G. McDonell. "Drop Evaporation". W Atomization and Sprays, 207–42. Second edition. | Boca Raton : Taylor & Francis, CRC Press, 2017.: CRC Press, 2017. http://dx.doi.org/10.1201/9781315120911-8.
Pełny tekst źródłaStreszczenia konferencji na temat "Atomization and Sprays"
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Prithiviraj, Manikandan, i Malcolm J. Andrews. "Atomization of Coal Water Slurry Sprays". W International Congress & Exposition. 400 Commonwealth Drive, Warrendale, PA, United States: SAE International, 1994. http://dx.doi.org/10.4271/940327.
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Jacobsohn, Gabriel L., Eli T. Baldwin, David P. Schmidt, Benjamin R. Halls, Alan Kastengren i Terrence R. Meyer. "Diffuse Interface Eularian Spray Atomization Modeling of Impinging Jet Sprays". W 2018 AIAA Aerospace Sciences Meeting. Reston, Virginia: American Institute of Aeronautics and Astronautics, 2018. http://dx.doi.org/10.2514/6.2018-2078.
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Corcoran, T., A. Mansour i N. Chigier. "Medical Atomization Design for Inhalation Therapy". W ASME 1997 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 1997. http://dx.doi.org/10.1115/imece1997-0779.
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Abstract The medical community has lately shown increased interest in drug administration via the internal surfaces of the lung. Administration of medication to the lungs is typically performed using either an aerosol or a spray, that is inhaled by the patient. Spray droplet size distribution is a primary determinant of whether medication will deposit effectively within the lungs. Spray liquid flow rates will determine required treatment time. Examination of three typical atomizer (nebulizer) designs used to generate inhalation sprays is presented. The separate stages in the design of these nebulizers include entrainment (jet pump), atomization, and conveyance stages. Mass flow rate of liquid in the sprays delivered from all examined designs was at least two orders of magnitude less than the mass flow rates of liquid pumped through the atomization stages. This indicated that liquid typically circulated through the atomization stages many times before being completely administered. Visualization was performed on the atomization stages showing less than ideal mechanisms for break up. Final outlet droplet cumulative number distributions obtained via Phase Doppler Particle Analyzer (PDPA) demonstrate that approximately 80% of the droplets generated by each design are within the range of sizes generally considered desirable for inhaled administration. (1–5 μm).
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GOMEZ, ALESSANDRO, i GUNG CHEN. "Secondary atomization in the combustion of electrostatic sprays". W 29th Joint Propulsion Conference and Exhibit. Reston, Virigina: American Institute of Aeronautics and Astronautics, 1993. http://dx.doi.org/10.2514/6.1993-2332.
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CHILDS, ROBERT, i NAGI MANSOUR. "Simulation of fundamental atomization mechanisms in fuel sprays". W 26th Aerospace Sciences Meeting. Reston, Virigina: American Institute of Aeronautics and Astronautics, 1988. http://dx.doi.org/10.2514/6.1988-238.
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Micci, M., R. Kujala, D. Gandilhon, M. Ferraro, M. Schmidt, M. Micci, R. Kujala, D. Gandilhon, M. Ferraro i M. Schmidt. "Unsteady hot wire atomization measurements in injector sprays". W 33rd Joint Propulsion Conference and Exhibit. Reston, Virigina: American Institute of Aeronautics and Astronautics, 1997. http://dx.doi.org/10.2514/6.1997-2845.
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Costa, Mário, Bruno Pizziol, Miguel Panao i André Silva. "Multiple Impinging Jet Air-Assisted Atomization". W ILASS2017 - 28th European Conference on Liquid Atomization and Spray Systems. Valencia: Universitat Politècnica València, 2017. http://dx.doi.org/10.4995/ilass2017.2017.4737.
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The growth of the aviation sector triggered the search for alternative fuels and continued improvements in thecombustion process. This work addresses the technological challenges associated with spray systems and theconcern of mixing biofuels with fossil fuels to produce alternative and more ecological fuels for aviation. This workproposes a new injector design based on sprays produced from the simultaneous impact of multiple jets, using anadditional jet of air to assist the atomization process. The results evidence the ability to control the average dropsize through the air-mass flow rate. Depending on the air-mass flow rate there is a transition between atomizationby hydrodynamic breakup of the liquid sheet formed on the impact point, to an aerodynamic breakup mechanism,as found in the atomization of inclined jets under cross-flow conditions. The aerodynamic shear breakupdeteriorates the atomization performance, but within the same order of magnitude. Finally, our experiments showthat mixing a biofuel with a fossil fuel does not significantly alter the spray characteristics, regarded as a stepfurther in developing alternative and more ecological fuels for aero-engines.DOI: http://dx.doi.org/10.4995/ILASS2017.2017.4737
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Araneo, Lucio, Robert Dondè, Lucio Postrioti i Andrea Cavicchi. "Analysis of PDA measurements in double injection GDI sprays". W ILASS2017 - 28th European Conference on Liquid Atomization and Spray Systems. Valencia: Universitat Politècnica València, 2017. http://dx.doi.org/10.4995/ilass2017.2017.5007.
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A N-heptane spray from a GDI multi-hole injector operated in ambient air at fixed conditions and with doubleinjection commands is studied with different experimental techniques to better understand the spray behaviors, focusing the analysis on the effect of different dwell times between the two pulses. Results from spray photographic analysis, fuel injected quantity, droplet velocity and sizing by Phase Doppler Anemometry are presented and compared. The peculiarities and usefulness of a complementary application of the different techniques is illustrated. The two spray pulses have the same time length, so that the first spray evolves in a nearly quiescent and clean ambient, while the second, nominally identical to the first one, evolves in its trailing edge. The direct comparison allows an immediate perception of the differences among the two sprays, at the different dwell times, where the shorter tested, 160 microseconds, was chosen as the one that shows the first appreciable effect with at least one of the used techniques; the differences are clearly evident in the PDA results, sufficiently visible from the injection rate, not appreciable in the imaging at short distance. The effect of the longerdwell times becomes more evident and is illustrated.DOI: http://dx.doi.org/10.4995/ILASS2017.2017.5007
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Boust, Bastien, Quentin Michalski, Alain Claverie, Clément Indiana i Marc Bellenoue. "Characterization of Liquid Impinging Jet Injector Sprays for Bi-Propellant Space Propulsion: Comparison of PDI and High-Magnification Shadowgraphy". W ILASS2017 - 28th European Conference on Liquid Atomization and Spray Systems. Valencia: Universitat Politècnica València, 2017. http://dx.doi.org/10.4995/ilass2017.2017.5001.
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Impinging jet sprays are investigated in the reference case of like-doublet injector, for application to bi-propellantcombustion. Green propellants are considered, namely ethanol as a fuel and hydrogen peroxide as an oxidizer, that is well represented by water. This study reports original comparisons between standard spray characterization (PDI) and high-magnification shadowgraphy of the spray (2.5 x 3.2 mm, 2.5 µm per pixel) based on short laser backlight illumination (5 ns). Shadowgraphy images describe accurately the inner spray structure and provide the size and velocity of droplets. This diagnostic is used to analyse the influence of jet momentum (driven by injection pressure) on impinging jet atomization, as well as the evolution of spray topology, drop size distribution and average diameter along the spray centreline. The application of shadowgraphy to the dense region of water and ethanol sprays shows the different atomization behaviour of these two fluids with respect to their surface tension. Elliptical droplets are characterized inside the spray, which confirms the interest of a direct visualization of droplets in suchdense sprays.DOI: http://dx.doi.org/10.4995/ILASS2017.2017.5001
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Son, S. Y., i K. D. Kihm. "Effect of Coal Particle Size on Coal-Water Slurry (CWS) Atomization". W ASME 1997 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 1997. http://dx.doi.org/10.1115/imece1997-0885.
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Abstract The effect of coal particle size on coal-water slurry (CWS) atomization is examined by comparing classified CWS sprays containing coal particles in different size ranges. The sprays are generated by injecting a CWS mixture into a sonic air jet and the Malvern sizing system nonintrusively measures spray Sauter mean diameters (SMD). The results consistently show that the spray SMDs of the CWS containing smaller coal particles are larger than the spray SMDs of the CWS containing larger coal particles. The internal capillary holding force between the particles and water increases with decreasing particle sizes because of their smaller radii of curvature. This increased holding force strongly resists against the external airblast and makes the atomization difficult. On the other hand, the relatively small capillary holding force of the CWS containing larger coal particles carries weaker resistance to the external airblast, and smaller spray SMDs result.
Raporty organizacyjne na temat "Atomization and Sprays"
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Lin, S. P. Mechanism of Atomization and Behavior of Non-Dilute Sprays. Fort Belvoir, VA: Defense Technical Information Center, czerwiec 1992. http://dx.doi.org/10.21236/ada254902.
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Genzale, Caroline. Development of a Turbulent Liquid Spray Atomization Model for Diesel Engine Simulations. Office of Scientific and Technical Information (OSTI), czerwiec 2021. http://dx.doi.org/10.2172/1785712.
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Oefelein, Joseph. Development of high-fidelity models for liquid fuel spray atomization and mixing processes in transportation and energy systems. Office of Scientific and Technical Information (OSTI), kwiecień 2015. http://dx.doi.org/10.2172/1494618.
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