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Artykuły w czasopismach na temat "Air in liquid compound droplets"
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Mota, Alisson A. B., Ulisses R. Antuniassi, Rodolfo G. Chechetto, Rone B. de Oliveira i Anne C. A. e. Silva. "Effect of adjuvants on the amount of air included in droplets generated by spray nozzles". Engenharia Agrícola 33, nr 6 (grudzień 2013): 1281–88. http://dx.doi.org/10.1590/s0100-69162013000600020.
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The air included in droplets generated by spray nozzles directly int0erferes in transport, deposition and retention of the droplets after its impact on the target. The objective of this study was to analyze the interference of adjuvants in the amount of air included in droplets generated by spray nozzles. The treatments were composed by four spray solutions containing mineral oil, vegetable oil, surfactant and water, and three spray nozzles, two air induction type and one pre-orifice. The air included was calculated by the difference between the volume of spray mix (air plus liquid) and only the liquid, which was made by means of sprayed samples captured in a funnel and collected in a graduated cylinder. The surface tension was estimated by the gravimetric method using a precision scale and a graduated pipette. The surfactant provided the largest percentage of air included in the spray. For the surface tension, the mineral oil and the surfactant had the lowest values. It was concluded that the use of adjuvants had a direct influence on the percentage of air included. In addition, products with greater ability to reduce surface tension and to form homogeneous solutions provided the increase in the percentage of air included in the droplet.
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Shinjo, J., J. Xia, L. C. Ganippa i A. Megaritis. "Puffing-enhanced fuel/air mixing of an evaporating -decane/ethanol emulsion droplet and a droplet group under convective heating". Journal of Fluid Mechanics 793 (18.03.2016): 444–76. http://dx.doi.org/10.1017/jfm.2016.130.
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Puffing of a decane/ethanol emulsion droplet and a droplet group under convective heating and its effects on fuel/air mixing are investigated by direct numerical simulation that resolves all of the liquid/gas and liquid/liquid interfaces. With distinct differences in the boiling point between decane and ethanol, the embedded ethanol sub-droplets can be superheated and boil explosively. Puffing, i.e. ejection of ethanol vapour, occurs from inside the parent decane droplet, causing secondary breakup of the droplet. The ejected ethanol vapour mixes with the outer gas mixture composed of air and vapour of the primary fuel decane, and its effects on fuel/air mixing can be characterised by the scalar dissipation rates (SDRs). For the primary-fuel SDR, the cross-scalar diffusion due to ethanol vapour puffing plays a dominant role in enhancing the micromixing. When the vapour ejection direction is inclined towards the wake direction, the wake is elongated, but the shape of the stoichiometric mixture fraction isosurface is not changed much, indicating a limited effect on droplet grouping in a spray. On the other hand, when the ejection direction is inclined towards the transverse direction, the stoichiometric surface is pushed further away in the transverse direction, and its topology is changed by the puffing. The trajectories of ejected ethanol vapour pockets can be predicted by the correlation obtained for a jet in cross-flow, and the vapour pockets may reach a few diameters away from the droplet. Therefore, in a multiple-droplet configuration, the transverse ethanol vapour ejection due to puffing may transiently change the droplet grouping characteristics. In simulation cases with multiple droplets, the interaction changing the droplet grouping due to puffing has been confirmed, especially for droplets in the most upstream position in a spray. This implies that puffing should be accurately included in the mixing and combustion modelling of such a biofuel-blended diesel spray process.
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Yasuda, Naohiro, Koji Yamamura i Yasuhiko H. Mori. "Impingement of liquid jets at atmospheric and elevated pressures: an observational study using paired water jets or water and methylcyclohexane jets". Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 466, nr 2124 (9.06.2010): 3501–26. http://dx.doi.org/10.1098/rspa.2010.0144.
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We have observed the impingement of two cylindrical liquid jets of either the same liquid, water, or two mutually immiscible liquids, water and methylcyclohexane (MCH), in either air under normal pressure (0.101 MPa) or nitrogen gas under elevated pressures up to 4.0 MPa. The flow rates of the two jets were adjusted such that they had equal axial momentum. Irrespective of the system pressure, we distinguished two characteristic regimes: the lower flow-rate regime, in which the jet impingement formed a regularly shaped planar sheet, and a higher flow-rate regime, in which a wrinkled sheet repeated azimuthal breakup. The transition from the former to the latter regime occurred at a lower flow rate for the water–MCH impingement than for the water–water impingement. An increase in the system pressure tended to shrink the liquid sheets, to promote the transition to the sheet-breakup regime and to intensify the liquid atomization. The formation of water–MCH compound droplets by the water–MCH impingement was confirmed visually.
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Shibaev, P. V., M. Wenzlick, J. Murray, A. Tantillo i J. Howard-Jennings. "Rebirth of Liquid Crystals for Sensoric Applications: Environmental and Gas Sensors". Advances in Condensed Matter Physics 2015 (2015): 1–8. http://dx.doi.org/10.1155/2015/729186.
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Films and droplets of liquid crystals may soon become an essential part of sensitive environmental sensors and detectors of volatile organic compounds (VOCs) in the air. In this paper a short overview of recent progress in the area of sensors based on liquid crystals is presented, along with the studies of low molar mass liquid crystals as gas sensors. The detection of VOCs in the air may rely on each of the following effects sequentially observed one after the other: (i) slight changes in orientation and order parameter of liquid crystal, (ii) formation of bubbles on the top of the liquid crystalline droplet, and (iii) complete isotropisation of the liquid crystal. These three stages can be easily monitored by a photo camera and/or optical microscopy. Detection limits corresponding to the first stage are typically lower by a factor of at least 3–6 than detection limits corresponding to isotropisation. The qualitative model taking into account the reorientation of liquid crystals is presented to account for the observed changes.
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Dupuy, R., P. Laj i K. Sellegri. "Cn to ccn relationships and cloud microphysical properties in different air masses at a free tropospheric site". Atmospheric Chemistry and Physics Discussions 6, nr 1 (1.02.2006): 879–98. http://dx.doi.org/10.5194/acpd-6-879-2006.
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Abstract. The fraction of aerosol particles activated to droplets (CCN) is often derived from semi-empirical relationships that commonly tend to overestimate droplet number concentration leading to major uncertainties in global climate models. One of the difficulties in relating aerosol concentration to cloud microphysics and cloud albedo lies in the necessity of working at a constant liquid water path (LWP), which is very difficult to control. In this study we observed the relationships between aerosol number concentration (NCN), cloud droplet concentration (Nd) and effective radius (Reff), at the Puy de Dôme (France). A total of 20 cloud events were sampled representing a period of more than 250 h of cloud sampling. Samples are classified first according to air mass origins (Modified Marine, Continental and Polluted) and then according to their liquid water content (Thin, Medium and Thick clouds). The CCN fraction of aerosols appears to vary significantly according to the air mass origin. It is maximum for Continental air masses and minimum for Polluted air masses. Surprisingly, the CCN fraction of Modified Marine air masses fraction is lower than the continental air mass and from expected from previous studies. The limited number of activated particles in Modified Marine air masses is most likely the result of the presence of hydrophobic organic compounds. The limited activation effect leads to a 0.5 to 1 μm increase in Reff with respect to an ideal Marine case. This is significant and implies that the dReff/dNCN of low-continental clouds is higher than expected.
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Kim, Jinhong, i Sung-Jin Park. "In-Situ Photo-Dissociation and Polymerization of Carbon Disulfide with Vacuum Ultraviolet Microplasma Flat Lamp for Organic Thin Films". Applied Sciences 11, nr 6 (15.03.2021): 2597. http://dx.doi.org/10.3390/app11062597.
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Vacuum UV (VUV) photo-dissociation for a liquid phase organic compound, carbon disulfide (CS2), has been investigated. 172 nm (7.2 eV) VUV photons from Xe2* excimers in a microcavity plasma lamp irradiated free-standing liquid droplets on Si substrate in each a nitrogen environment and an atmospheric air environment. Selective and rapid dissociation of CS2 into C-C, C-S or C-O-S based fragments was observed in the different gas environments during the reaction. Thin-layered polymeric microdeposites have been identified by characterization with a Scanning electron microscope (SEM), Energy dispersive x-ray spectroscopy (EDX), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). This novel photo-process from the flat VUV microplasma lamp introduces another pathway of low-temperature organic (or synthetic) conversion for large area deposition. The in-situ, selective conversion of various organic precursors can be potentially used in optoelectronics and nanotechnology applications.
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Huang, Shuquan, Jessica Connolly, Andrei Khlystov i Richard B. Fair. "Digital Microfluidics for the Detection of Selected Inorganic Ions in Aerosols". Sensors 20, nr 5 (27.02.2020): 1281. http://dx.doi.org/10.3390/s20051281.
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A prototype aerosol detection system is presented that is designed to accurately and quickly measure the concentration of selected inorganic ions in the atmosphere. The aerosol detection system combines digital microfluidics technology, aerosol impaction and chemical detection integrated on the same chip. Target compounds are the major inorganic aerosol constituents: sulfate, nitrate and ammonium. The digital microfluidic system consists of top and bottom plates that sandwich a fluid layer. Nozzles for an inertial impactor are built into the top plate according to known, scaling principles. The deposited air particles are densely concentrated in well-defined deposits on the bottom plate containing droplet actuation electrodes of the chip in fixed areas. The aerosol collection efficiency for particles larger than 100 nm in diameter was higher than 95%. After a collection phase, deposits are dissolved into a scanning droplet. Due to a sub-microliter droplet size, the obtained extract is highly concentrated. Droplets then pass through an air/oil interface on chip for colorimetric analysis by spectrophotometry using optical fibers placed between the two plates of the chip. To create a standard curve for each analyte, six different concentrations of liquid standards were chosen for each assay and dispensed from on-chip reservoirs. The droplet mixing was completed in a few seconds and the final droplet was transported to the detection position as soon as the mixing was finished. Limits of detection (LOD) in the final droplet were determined to be 11 ppm for sulfate and 0.26 ppm for ammonium. For nitrate, it was impossible to get stable measurements. The LOD of the on-chip measurements for sulfate was close to that obtained by an off-chip method using a Tecan spectrometer. LOD of the on-chip method for ammonium was about five times larger than what was obtained with the off-chip method. For the current impactor collection air flow (1 L/min) and 1 h collection time, the converted LODs in air were: 0.275 μg/m3 for sulfate, 6.5 ng/m3 for ammonium, sufficient for most ambient air monitoring applications.
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Zamora, Rosendo, Juan Martínez-Pastor i Félix Faura. "Thermal, Viscoelastic and Surface Properties of Oxidized Field’s Metal for Additive Microfabrication". Materials 14, nr 23 (2.12.2021): 7392. http://dx.doi.org/10.3390/ma14237392.
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Field’s metal, a low-melting-point eutectic alloy composed of 51% In, 32.5 Bi% and 16.5% Sn by weight and with a melting temperature of 333 K, is widely used as liquid metal coolant in advanced nuclear reactors and in electro–magneto–hydrodynamic two-phase flow loops. However, its rheological and wetting properties in liquid state make this metal suitable for the formation of droplets and other structures for application in microfabrication. As with other low-melting-point metal alloys, in the presence of air, Field’s metal has an oxide film on its surface, which provides a degree of malleability and stability. In this paper, the viscoelastic properties of Field’s metal oxide skin were studied in a parallel-plate rheometer, while surface tension and solidification and contact angles were determined using drop shape analysis techniques.
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Simon, Julianna C., Oleg A. Sapozhnikov, Vera A. Khokhlova, Lawrence A. Crum i Michael R. Bailey. "Ultrasonic atomization of liquids in drop-chain acoustic fountains". Journal of Fluid Mechanics 766 (2.02.2015): 129–46. http://dx.doi.org/10.1017/jfm.2015.11.
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AbstractWhen focused ultrasound waves of moderate intensity in liquid encounter an air interface, a chain of drops emerges from the liquid surface to form what is known as a drop-chain fountain. Atomization, or the emission of micro-droplets, occurs when the acoustic intensity exceeds a liquid-dependent threshold. While the cavitation-wave hypothesis, which states that atomization arises from a combination of capillary-wave instabilities and cavitation bubble oscillations, is currently the most accepted theory of atomization, more data on the roles of cavitation, capillary waves, and even heat deposition or boiling would be valuable. In this paper, we experimentally test whether bubbles are a significant mechanism of atomization in drop-chain fountains. High-speed photography was used to observe the formation and atomization of drop-chain fountains composed of water and other liquids. For a range of ultrasonic frequencies and liquid sound speeds, it was found that the drop diameters approximately equalled the ultrasonic wavelengths. When water was exchanged for other liquids, it was observed that the atomization threshold increased with shear viscosity. Upon heating water, it was found that the time to commence atomization decreased with increasing temperature. Finally, water was atomized in an overpressure chamber where it was found that atomization was significantly diminished when the static pressure was increased. These results indicate that bubbles, generated by either acoustic cavitation or boiling, contribute significantly to atomization in the drop-chain fountain.
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Zhao, Ning-Ning, Xin-Yu Xiao, Feng-Xian Fan i Ming-Xu Su. "Ultrasonic attenuation model of mixed particle three-phase system based on Monte Carlo method". Acta Physica Sinica 71, nr 7 (2022): 074303. http://dx.doi.org/10.7498/aps.71.20211869.
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From the perspective of calculating ultrasonic absorption and scattering properties of individual solid particle and droplet, the ultrasonic wave is treated as discrete phonons. And by tracking their motion process and event statistics, a new prediction model of ultrasonic attenuation of spherical mixed particles in gaseous medium is established with Monte Carlo method. Considering the difference in physical properties between solid particles and liquid particles, the ultrasonic absorption characteristics of the two kinds of particles are obviously different, and when dimensionless particle size <i>kR</i> ≤ 1, the backscattering of particles is uniform and dominant, then the ultrasonic scattering pressures gradually transit from the dominant position of backscattering to the trend of forward enhancement with the increase of dimensionless particle size. The numerical simulation results for the system with a single particle type are compared with those from various standard models such as classical ECAH model and McC model, showing that they are in good agreement. Similarly, the results are then compared with experimental results, which accord with each other in general. After calculating and verifying the ultrasonic attenuation of aluminum particles and submicron droplets respectively in air, the method is extended to the three-phase monodisperse and polydisperse mixed particle system composed of aluminum particles and liquid droplets. In the three-phase system of gas-liquid-solid mixed particles, the particle type has a significant influence on ultrasonic attenuation, and the attenuation contribution of different particles against mixing ratio does not follow the linear gradient with the increase of volume concentration. For a polydisperse system, the ultrasonic attenuation spectrum is greatly affected by the average particle size, but it is insensitive to the width of particle size distribution. The numerical results also show that both the particle type and particle distribution size should be carefully take into account in the polydisperse system. Moreover, the MCM model can be further extended to non-spherical particles and combined with mathematical inversion to form the theoretical basis for the measurement of mixed particle system.
Rozprawy doktorskie na temat "Air in liquid compound droplets"
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Wang, Miao. "Study of Volatile Organic Compounds (VOC) in the cloudy atmosphere : air/droplet partitioning of VOC". Thesis, Université Clermont Auvergne (2017-2020), 2019. http://www.theses.fr/2019CLFAC080.
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Les composés organiques volatils (COV), les hydrocarbures saturés, insaturés et autres hydrocarbures substitués, jouent un rôle majeur dans la chimie atmosphérique. Ils sont principalement émis par des sources anthropiques et biogéniques dans l'atmosphère; ils sont également transformés in situ par des réactions chimiques, et plus spécifiquement par photo-oxydation conduisant à la formation d'ozone (O3) et d'aérosol organique secondaire (SOA). En modifiant la fraction organique des particules d'aérosol, les COV modifient l'équilibre radiatif de la Terre par un effet direct (absorption et diffusion du rayonnement solaire) ou par un effet indirect en altérant les propriétés microphysiques des nuages. Ils présentent également un effet direct sur la santé humaine et l'environnement. Au cours de leur transport atmosphérique, les COV et leurs produits d'oxydation, les composés organiques volatils oxygénés (OVOC), peuvent se répartir entre les phases gazeuses et aqueuses en fonction de leur solubilité. Les nuages ont un effet significatif sur la chimie troposphérique en redistribuant les traces de constituants entre les phases et en fournissant de l'eau liquide dans laquelle la chimie de la phase aqueuse peut avoir lieu. En effet, pendant la durée de vie des nuages, les composés chimiques et notamment les COV se transforment efficacement car les nuages favorisent le développement d'une «chimie multiphasique». Cette dernière présente plusieurs particularités. Premièrement, les processus photochimiques à l'intérieur des gouttelettes sont importants dans la transformation des composés chimiques. Deuxièmement, les réactions chimiques aqueuses sont efficaces et peuvent être plus rapides que les réactions équivalentes en phase gazeuse. Cela peut être lié à la présence d'oxydants puissants tels que le peroxyde d'hydrogène H2O2 ou les ions métalliques de transition (TMI), qui participent à la formation de radicaux tels que les radicaux hydroxyles (HO •) qui favorisent les processus d'oxydation. De plus, la présence de micro-organismes viables a été mise en évidence et a montré sa participation aux transformations des espèces chimiques. Enfin, ces transformations dans les nuages sont également fortement perturbées par des processus microphysiques qui contrôlent la formation, la durée de vie et dissipation des nuages. Ces processus redistribueront les espèces chimiques entre les différents réservoirs (eau de nuages, pluie, phase particulaire, phase gazeuse et phase de glace solide). Dans ce cadre, la transformation des COV dans le milieu nuageux peut conduire à la production de composés secondaires contribuant à la formation de SOA, appelés «nuage aqSOA». Cette masse d'aérosol organique secondaire produite pendant la durée de vie du nuage pourrait expliquer en partie l'ubiquité des petits acides dicarboxyliques et céto et des composés de haut poids moléculaire mesurés dans les particules d'aérosol, l'eau de brouillard, l'eau de nuage ou l'eau de pluie à de nombreux endroits, car ils n'ont ni sources d'émission directe ni aucune source importante identifiée en phase gazeuse. Cette masse d'aqSOA reste en phase particulaire après évaporation des nuages impliquant une modification des propriétés (micro) physiques et chimiques des particules d'aérosol (taille des particules, composition chimique, morphologie). Ceci conduit à des modifications de leurs impacts sur les cycles consécutifs de nuages ou de brouillard (effets indirects des aérosols) et de leurs interactions avec les rayonnements entrants par diffusion / absorption (effet direct des aérosols). (...)Volatile Organic Compounds (VOC), including saturated, unsaturated, and other substituted hydrocarbons, play a major role in atmospheric chemistry. They are primarily emitted by anthropogenic and biogenic sources into the atmosphere; they are also transformed in situ by chemical reactions, and more specifically, by photo-oxidation leading to the formation of ozone (O3) and Secondary Organic Aerosol (SOA). By altering the organic fraction of aerosol particles, VOC modify the Earth’s radiative balance through a direct effect (absorption and scattering of solar radiation) or through indirect effect by altering cloud microphysical properties. They also present a direct effect on human health and on the environment.During their atmospheric transport, VOC and their oxidation products, Oxygenated Volatile Organic Compounds (OVOC), may partition between the gaseous and aqueous phases depending on their solubility. Clouds have a significant effect on tropospheric chemistry by redistributing trace constituents between phases and by providing liquid water in which aqueous phase chemistry can take place. Indeed, during the cloud lifetime, chemical compounds and particularly VOC are efficiently transformed since clouds favor the development of complex “multiphase chemistry”. The latter presents several particularities. First, photochemical processes inside the droplets are important in the transformation of chemical compounds. Second, aqueous chemical reactions are efficient and can be faster than the equivalent reactions in the gas phase. This can be related to the presence of strong oxidants such as hydrogen peroxide H2O2 or Transition Metal Ions (TMI), which participate in the formation of radicals such as hydroxyl radicals (HO•) that favor oxidation processes. Furthermore, the presence of viable microorganisms has been highlighted and shown to participate in transformations of the chemical species. Finally, these transformations in clouds are also strongly perturbed by microphysical processes that control formation, lifetime and dissipation of clouds. These processes will redistribute the chemical species between the different reservoirs (cloud water, rain, particle phase, gaseous phase, and solid ice phase). In this frame, the transformation of VOC in the cloud medium can lead to the production of secondary compounds contributing to SOA formation, reported as “cloud aqSOA”. This secondary organic aerosol mass produced during the cloud lifetime could explain in part the ubiquity of small dicarboxylic and keto acids and high molecular-weight compounds measured in aerosol particles, fog water, cloud water, or rainwater at many locations, as they have neither substantial direct emission sources nor any identified important source in the gas phase. This aqSOA mass stays in the particle phase after cloud evaporation implying a modification of the (micro)physical and chemical properties of aerosol particles (particle size, chemical composition, morphology). This leads to modifications of their impacts on consecutive cloud or fog cycles (aerosol indirect effects) and of their interactions with incoming radiation by scattering/absorbing (aerosol direct effect). (...)
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Wiese, Jessica A. "Determination of benzotriazole and analog compounds by liquid chromatography-mass spectrometry in surface runoff water samples from Wilmington Air Park". Wright State University / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=wright1576573860964496.
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Gunawardana, Wahalathanthriga Dhanapala. "A study of the efficiency of recovery of micron size droplets from high velocity air-liquid mixtures in a centrifugal field, employing a metal and plastic porous disc". Thesis, University of East London, 2002. http://roar.uel.ac.uk/3871/.
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This work is specially contributes to the knowledge in the field of efficient removal of entrained micron size liquid drops from air mist in a centrifugal field using bimetallic and bi-surface (low and high energy) porous discs. The available equipment was suitably modified, commissioned and utilised in this investigation. The variables investigated include: different rotational speeds; various air and liquid flow-rates; three materials of construction and five porosities of the rotating porous discs. The average residence time of two-phase two-component flow of fine air mist through the rotating porous disc was in the range of 0.7ms to 3.0ms. A high-resolution and magnification optical method has been used to record, explain and understand the mechanism of wettability of the bi-metal and bi-surface energy porous discs. Navier-Stokes equations of momentum have been used to develop a mathematical model to predict the width of a liquid film formed on top of the rotating porous disc. The predictions of the model compared very favorably with the experimental data. The final empirical equations that represents the separation efficiency, (45 to near 100 %) of the bi-metallic and bi-surface energy (high and low) porous disc rotating at, 0+ to 6100 r/min, are [equation 1] for inline arragement of openings/holes in the porous disc. And [equation 2] for staggered arrangement of openings/holes in the porous disc. Artificial neural networks have been successfully used for the modelling and correlation of experimental data, collected from six porous discs with five porosities and three materials of construction with high and low surface energies, on percent separation efficiency from mixture of air-water mist. The correlation coefficient between the experimental and predicted separation efficiency was found to be 0.95. The Lockhart- Martinelli approach has been used to develop an empirical equation for the constant B, as defined by Lockhart- Martinelli that may be used for the calculation of co-current plus cross-current two-phase two-component pressure drop in this system. [equation 3] An empirical equation that has been developed to predict the liquid film's width is [equation 4] The correlation coefficient between the experimental and predicted film widths was found to be 0.92. Equations 1 to 4 may be used to design a new system for the continuous removal/separation of entrained micron size drops from high velocity air mist.
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Bois, André. "Proprietes dynamiques des monocouches de molecules amphiphiles a l'interface eau-air". Aix-Marseille 1, 1987. http://www.theses.fr/1987AIX11080.
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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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Jadaud, Philippe. "Separation d'hydrocarbures polynucleaires aromatiques par chromatographie en phase liquide". Paris 6, 1987. http://www.theses.fr/1987PA066442.
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Preconcentration par chromatographie par transfert de charges sur silice greffee tetrachlorophtalimidopropyle. La retention varie de 80 (fluoranthene) a 2600 (benzo(ghi)perylene). Detection spectrofluorometrique
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Naidu, Ponnana Deekshith. "Classical Approach to Understanding the Impact Dynamics of Hollow Droplets". Thesis, 2022. https://etd.iisc.ac.in/handle/2005/5914.
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Compound droplets are utilized in applications ranging from the preparation of emulsion to
biological cell printing and additive manufacturing. Here, we report on the impact dynamics of
a compound hollow droplet on a solid substrate. Contrary to the impact of simple droplets and
compound droplets with liquids of similar densities, the compound droplet with an
encapsulated air bubble demonstrates the formation of a counterjet in addition to the lamella.
Here, we experimentally investigate the influence of the size of the air bubble, liquid viscosity,
and height of impact on the evolution of counterjet and the spreading characteristics of the
lamella. For a given hollow droplet, the volume of the counterjet is observed to depend on the
volume of air and liquid in the droplet and is independent of the viscosity of the liquid and
impact velocity of the droplet. We observe that the spread characteristics, counterintuitively,
do not vary significantly compared to that of a simple droplet having an identical liquid volume
as the hollow droplet. We propose a model to predict the maximum spread during the impact
of a hollow droplet on a substrate based on the energy interaction between the spreading liquid
and the liquid in the counterjet during the impact process. Furthermore, the maximum spread
diameter during the impact of a HD obtained using the model developed is in excellent
agreement with that observed in experiments.
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yen-wen, Chen, i 陳彥文. "Experiment and Analysis of the Drag Force of Freely-Falling Liquid Droplets in Air". Thesis, 2002. http://ndltd.ncl.edu.tw/handle/61478820771518499845.
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碩士國立臺灣大學
機械工程學研究所
90
In this study we investigated the effect of freely-falling droplets on drag force. A single stream of mono-sized stable droplets were generated by piezo-electric transducer and fell into quiescent surrounding air, then we recorded the trajectory of droplets by CCD camera. The species of droplets included water, hexadecane and heptane. By measuring the velocity and diameter of droplet with time, we got the acceleration profile of droplets and the drag force of droplet along the path. Our experiments included two parts. One was the effect of acceleration and properties on the drag coefficient in isolated droplet；the other was the influence of droplet spacing on the drag coefficient in steady, monodisperse droplet stream. We then tried to nondimensionalize the experiment data as CD, Re, Ac, and S/d ratio. The range of Reynolds numbers were from 5 to 200 and experimental uncertainties were typically less than 5 percent.
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Roy, Durbar. "Experimental and Theoretical Insights into Impact Phenomena of Small Scale Liquid Interfacial Systems". Thesis, 2023. https://etd.iisc.ac.in/handle/2005/6128.
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This work explores impact phenomena experimentally and theoretically for various
interfacial systems ranging from medical diagnostics to drop impacts on solids and
immiscible liquids. We study a hitherto unexplored impact phenomenon during
an ophthalmology procedure called Non-Contact Tonometry. Using high fidelity
experiments and theoretical modeling, we show that noninvasive ocular diagnostics
demonstrate a propensity for droplet generation and present a potential pathway for
pathogen transmission. The air puff-induced corneal deformation and subsequent
capillary waves lead to flow instabilities (Rayleigh–Taylor, Rayleigh–Plateau) that
lead to tear film ejection, expansion, stretching, and subsequent droplet formation.
Effective cooling is one of the significant application areas of impact systems. In
the context of cooling problems, we provide new insights using ab initio scaling and
boundary layer analysis of the integral and differential forms of the conservation
equations. We have probed the limiting scaling regimes by incorporating the evap-
orative effects at the liquid-vapor interface. The dependence of liquid film thickness
and Nusselt number on various non-dimensional numbers has been explored. We
then investigate the class of drop impact problems where we study impacts on solids,
bio-inspired substrates, and immiscible liquid pools at low to moderate impact en-
ergies. We explore impacts on glass, PDMS, and soft lithographically fabricated
replicas of the lotus leaf and rose petals. Surprisingly, the rose petal and lotus leaf
replicas manifest similar impact dynamics. The observation is extremely intriguing
and counter-intuitive, as rose petals and their replicas are sticky in contrast to lotus
leaves. Air entrapment in the micrometer features of bio-inspired surfaces prevents
frictional dissipation of droplet kinetic energy, leading to contact edge recession and
subsequent break-up modes of the droplet. We explore the air entrapment dynamics
beneath an impacting droplet on an immiscible viscous liquid pool using high-speed
reflection interferometry imaging and linear stability analysis. We have detected
unique hydrodynamic topology in thin air film surrounding the central air dimple
(peripheral disc). The pattern resembles spinodal and finger-like structures typi-
cally found in various thin condensed matter systems. We attribute the formation
of multi-scale thickness perturbations, associated ruptures, and finger-like protru-
sions in the draining air film as a combined artifact of thin-film and Saffman–Taylor
instabilities. We also investigate the air craters formed on the surface of the impact-
ing droplet and attribute its formation to the rapid deceleration of the droplet due to
viscous drag force. The droplet response to the external impulsive decelerating force
induces oscillatory modes on the surface exposed to the air forming capillary waves
that superimpose to form air craters of various shapes and sizes. We introduce a
non-dimensional parameter, the ratio of the drag force to the capillary force acting
on the droplet to characterize the air craters. Further, we generalize the local droplet
response with a global response model for low-impact energies based on an eigenvalue problem. We represent the penetrating drop as a constrained Rayleigh drop
problem with a dynamic contact line. The air-water interface dynamics are analyzed
using an in-viscid droplet deformation model for small deformation amplitudes. The
local and global droplet response theories conform and depict that the deformation
profiles could be represented as a linear superposition of eigenmodes in a Legendre
polynomial basis. We further study air layer dynamics beneath an impacting droplet
on a heated surface at various surface temperatures at low impact energy. The air
layer thickness profile consisting of the dimple and the peripheral disc has been
measured using high-speed reflection interferometric imaging. We decipher that a
Gaussian profile can approximate the dimple height profile characteristics. The dim-
ple thickness profile has a weak dependence on the substrate temperature and is a
function of impact energy in general. The air layer rupture time scale and rupture
radius increase with an increase in the substrate temperature. We characterize the
air layer profile as a Knudsen field and show that a unified treatment, including
continuum and non-continuum mechanics, is required to understand the air layer
dynamics. The asymmetric wetting of the substrate by the impacting droplet initi-
ates in the peripheral disc region. In the non-continuum regimes in the peripheral air
disc, we discover intriguing asymmetric interface perturbations. These perturbative
structures cause asymmetric wetting/contact between the droplet and the substrate.
The sub-micron length scales of the structures exist due to the asymptotic effects of
capillary and Van-der Waals interaction in the disc region.
Części książek na temat "Air in liquid compound droplets"
1
Holló, G., Á. Leelossy, R. Tóth i I. Lagzi. "Chapter 7. Tactic Droplets at the Liquid–Air Interface". W Theoretical and Computational Chemistry Series, 167–81. Cambridge: Royal Society of Chemistry, 2018. http://dx.doi.org/10.1039/9781788013499-00167.
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Mutenhabundo, Winnie, Tawanda Mushiri, Timothy Gutu i Patson Zvandasara. "Liquid Desiccant Dehumidification Systems: Jet Cross-Talking Effect in Multi-electrosprays". W Lecture Notes in Mechanical Engineering, 258–65. Cham: Springer International Publishing, 2023. http://dx.doi.org/10.1007/978-3-031-28839-5_29.
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AbstractWhen liquid desiccant systems are employed to dehumidify air electrospraying technique helps to increase the surface area of the liquid. Multiplexing of the jets by introducing several emitters for increased efficiency is commendable but, there is a tendency of the jets to cross talk with each other due to electrical shielding. Cross talking of jets will result in the failure of the jets to break properly into droplets for effective dehumidification. This piece of work analyzed the conditions for electrical shielding among jets which results in efficient electrospray. To evaluate how cross talking affects multiple emitter nozzles, the mathematical model was built by superimposing the electric potentials of one emitter in an array of emitters. A Computational Fluid Dynamics simulation model was developed to investigate the conditions for electrical shielding among jets during electrospray process with glycerol as the working substance. In flow modelling, Ansys Fluent with Volume of Fluid and the Taylor Dielectric model were involved. The flow rate that guarantees stability in the electrospray was determined together with the optimum voltage resulting in a spray current which reduces electrical shielding. An analysis on the electrical conductivity of the liquid to ensure stability and efficiency in electrospray was done. The pressure contours of the nozzle were determined together with velocity of the desiccant against density. Emitter spacing, applied voltage, flow rate and the electrical conductivity plays a pivotal role on the prevention of cross talking of jets during the electrospraying process.
3
Eckhoff, Rolf K. "Explosions of Clouds of Combustible Liquid Droplets in Air". W Explosion Hazards in the Process Industries, 209–32. Elsevier, 2016. http://dx.doi.org/10.1016/b978-0-12-803273-2.00005-0.
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Eckhoff, Rolf K. "Explosions in Clouds of Liquid Droplets in Air (Spray/Mist)". W Explosion Hazards in the Process Industries, 149–73. Elsevier, 2005. http://dx.doi.org/10.1016/b978-0-9765113-4-2.50008-7.
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Whiteman, C. David. "Air Pollution Dispersion". W Mountain Meteorology. Oxford University Press, 2000. http://dx.doi.org/10.1093/oso/9780195132717.003.0021.
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Air pollutants are harmful airborne substances (solids, liquids, or gases) that, when present in high-enough concentrations, threaten human health or welfare, harm vegetation, animals, or structures, or affect visibility. Visibility alone is not, however, a reliable indicator of the presence of pollutants. A visible plume of condensed water vapor from an industrial cooling tower decreases solar radiation and increases the frequency of fog and icy road conditions near the cooling tower, but it is not an air pollution plume because it is composed entirely of water. In contrast, an industrial pollutant plume may be nearly invisible after the gross particulate matter has been removed by pollution control equipment, but it may still contain large quantities of pollutant gases. Air pollutants can come from either natural or anthropogenic (human) sources. The distinction between the two categories is not always clear. Natural emissions include ash and dust from volcanoes, certain highly volatile chemicals from forests, aeroallergens such as ragweed pollen, wind-entrained dust from natural land surfaces, and smoke and ash from wildfires. Wind-entrained dust can, however, come from roadways or land surfaces that have been disturbed by man, some aeroallergens come from plant species introduced to a new habitat by man, and many fires are prescribed fires —natural or man-made fires (whether accidental or deliberate) that are allowed to burn in order to meet forest or land management objectives. Pollutants can be emitted directly into the atmosphere (primary pollutants] or produced in the atmosphere (secondary pollutants) as a result of chemical or physical transformations of primary pollutants when exposed to other components of air, including other pollutants or water vapor. Examples of transformations include the clumping or coagulation of small particulates into larger particles and the conversion of sulfur dioxide gas emitted from coal-fired power plants to particulate sulfates under humid conditions or to acid rain droplets if clouds are present. Some secondary pollutants, such as photochemical smog or ozone, result from photochemical reactions, that is, chemical reactions that occur only in the presence of solar radiation. Pollutants may come from point, area, or line sources; the emissions may be continuous or intermittent; and the source strength may be variable or constant.
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Mishra, Loveneet, Usha Chauhan, S. P. S. Chauhan i Harshit Singh. "Air Pollution Effects on the Habitat of Insects and Strategic Control to Improve Productivity". W Advances in Electronic Government, Digital Divide, and Regional Development, 216–27. IGI Global, 2023. http://dx.doi.org/10.4018/978-1-6684-6418-2.ch012.
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Urbanization has significantly worsened the ecosystem by releasing harmful substances and gases into the air through air pollution, which has an impact on the population demographics of insect herbivores. A pest outbreak and the formation of new pest biotypes are caused by the careless application of wide spectrum pesticides, which decimate the population of important pollinators and foragers. The potential efficiency of phloem-feeding homopteran insects such aphids is increased by pollutants like sulphur dioxides, oxides of nitrogen, fluorides, and heavy metals in the environment. Industrial melanism in moths is caused by a decline in the light-coloured lichens as a result of pollution. However, trophic amplification caused by high toxicant concentrations reduces the susceptibility of the parasitise & predators. The population growth of invading alien pest species & tropical disease vectors is amplified by air pollution and the acceleration of global warming. However, steps have been taken to reduce air pollution and boost agricultural output. The fabric filtration method uses filter cakes to remove air contaminants in this manner. Successful electrostatic precipitation strategies remove charged droplets of solid or liquid from syngas where the suspended particles exist. However, methods like thermal incineration & catalytic oxidation, which essentially use a catalyst activator to transform organic chemicals in waste gas streams into CO2, liquid water vapor, as well as inorganic-gases at extreme temps, are in use. Additional to these methods Due to their low operating and capital expenses, biofilters could be employed in conjunction with the other treatment technologies. Thus, successful reduction of air pollution can restore the health of agricultural plants and lessen food shortage.
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Brendler Goettems Fiorin, Pauline, Mirna Stela Ludwig, Matias Nunes Frizzo i Thiago Gomes Heck. "Environmental Particulate Air Pollution Exposure and the Oxidative Stress Responses: A Brief Review of the Impact on the Organism and Animal Models of Research". W Reactive Oxygen Species [Working Title]. IntechOpen, 2021. http://dx.doi.org/10.5772/intechopen.101394.
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Particulate matter (PM) is a mixture of solid particles and liquid droplets found in the air, and it is one of the most harmful air pollutants. When inhaled, it affects the pulmonary system, cardiovascular systems, and other tissues. The size, composition, and deposition of PM, mainly related to fine and ultrafine particulate matter, are factors that determine the harmful effects of exposure to particles. Among the main effects is the inducer of ROS production, and consequently oxidative tissue damage in target organs and other responses, mediated by inflammatory cytokines and cellular stress response. The main pathway through which particles are potent mediators of oxidative stress is the damage caused to DNA and lipid molecules, whereas the pro-inflammatory response involves an immune response against PM, which in turn, it is related to cell stress responses observed by heat shock proteins (HSPs) expression and release. Thus, the ability of an organism to respond to PM inhalation requires anti-oxidative, anti-inflammatory, and cellular stress defenses that can be impaired in susceptible subjects as people with chronic diseases as diabetes and obesity. In this chapter, we discuss the mechanistic aspects of PM effects on health and present some animal research models in particle inhalation studies.
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Schumann, Ulrich. "Contrail Cirrus". W Cirrus. Oxford University Press, 2002. http://dx.doi.org/10.1093/oso/9780195130720.003.0015.
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A contrail (a term introduced for “condensation trail” in 1942 by British pilots) is a visible cloud forming behind aircraft, mainly due to water vapor emissions from the engines. Contrails were first observed behind propeller-driven aircraft in 1915 but form as well from the exhaust of jet engines in cold ambient air (Schumann 1996a). Contrails are visible indicators of cruising aircraft and may impact the Earth's climate. Aircraft exhaust may influence cloud formation either directly by forming contrails or indirectly by causing an aerosol of black carbon soot, volatile particles, and metallic particles which later impact the formation and properties of cirrus clouds in the same air mass at other places. Though the cover by contrails is small compared to the cover by natural cirrus clouds, the potential climatic importance of contrails is being studied intensively. A review of the results obtained so far has been prepared for an assessment on Aviation and the Global Atmosphere (IPCC 1999). It reveals considerable progress in understanding aviation-produced aerosols and cloudiness (Fahey and Schumann 1999). Contrail studies also aid in learning about cirrus formation because contrails are cirrus clouds that form under relatively well defined and reproducible conditions. This chapter reviews some of the progress in understanding contrail formation, occurrence, properties, and radiative impact and identifies some important unanswered questions. Contrail formation can be accurately predicted for given atmospheric temperature and humidity conditions. Contrails form thermodynamically according to the Schmidt-Appleman criterion (Schmidt 1941; Appleman 1953) when the relative humidity (RH) in the plume of exhaust gases mixing with ambient air temporarily reaches or exceeds liquid saturation, so that liquid droplets form on cloud-condensation nuclei (CCN) and soon freeze to ice particles. Measurements have shown that liquid saturation is indeed necessary (see fig. 11.1) and that contrails do not form when the RH exceeds ice saturation (Jensen et al. 1998b; Kärcher et al. 1998a; Schumann et al. 2000). The maximum RH reaches liquid saturation when the ambient temperature is below a threshold temperature of typically -50° to -35°C, depending on ambient pressure and humidity and aircraft properties. This maximum is reached in the young plume (age <0.5 s) closely behind the aircraft.
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Whiteman, C. David. "Precipitation". W Mountain Meteorology. Oxford University Press, 2000. http://dx.doi.org/10.1093/oso/9780195132717.003.0015.
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Precipitation is often the primary weather factor affecting outdoor activities. Precipitation that is of an unexpected type or intensity or that comes at an unexpected time or recurs more frequently than expected can disrupt both recreational and natural resource management plans. Heavy rain or snowfall can interfere with travel and threaten safety. Precipitation is water, whether in liquid or solid form, that falls from the atmosphere and reaches the ground. Table 8.1, adapted from Federal Meteorological Handbook No. 1 (National Weather Service, 1995), describes the different types of precipitation particles, collectively called hydrometeors. International guidelines for the reporting of precipitation do not include a category for sleet. Meteorologists in the United States use the term to describe tiny ice pellets that form when rain or partially melted snowflakes refreeze before reaching the ground. These particles bounce when they strike the ground and produce tapping sounds when they hit windows. Colloquial usage of the term, often used by the news media, coincides with British usage, which defines sleet as a mixture of rain and snow. Snow pellets, or graupel, are common in high mountain areas in summer. Graupel are low density particles (i.e., not solid ice) formed when a small ice particle (an ice crystal, snowflake, ice pellet, or small hailstone) falls through a cloud of supercooled (section 8.4) water droplets. The tiny droplets freeze as they impact the larger ice particle, building it into a rounded mass containing air inclusions (figure 8.1). This coating of granular ice particles is called rime, and the particle is said to be rimed. Graupel is usually produced in deep convective clouds that extend above the freezing level. Whereas graupel reaches the ground at high elevations, it usually melts to form rain before reaching the ground at lower elevations. As falling snow accumulates, a snowpack develops that can be described in terms of water content and density. The water content of snow is usually expressed as specific gravity, a number obtained in this application by dividing the water-depth equivalent of snow by the actual snow depth.
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Fawcett, W. Ronald. "Liquids and Solutions at Interfaces". W Liquids, Solutions, and Interfaces. Oxford University Press, 2004. http://dx.doi.org/10.1093/oso/9780195094329.003.0012.
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When the properties of liquids and solutions are considered, attention is normally focused on the bulk of the phase, and the properties of the system at its boundaries are ignored. Significant effects are associated with the region near the surface of a liquid phase and an understanding of these is an important part of solution chemistry. As a simple example, consider a beaker of pure water at room temperature in a closed inert environment. As has been seen in the consideration of liquid structure, the properties of water are strongly influenced by hydrogen bonding between neighboring molecules, and to a lesser extent by dipole–dipole interactions. As an observer at the molecular level, one would find that the molecules near the boundaries of the water phase have different properties. There are two boundaries in this system, the water | air interface and the water | glass interface. At the water | air interface, the important feature is the termination of intermolecular interactions, so that molecules must adjust to an environment where the number of nearest neighbors is reduced. At the water | glass interface, water molecules meet the components of glass, a supercooled liquid with silicon dioxide as the major component. Interaction between water and silicon dioxide is different from interaction among water molecules. It is clear that the molecular environment at these interfaces is very different than it is in the bulk. As a result, local properties are different. Now imagine that the water in the beaker is dispersed as a fog, that is to say, as many very small droplets for which the ratio of surface area to volume is much larger than for the water in the beaker. It is obvious that the thermodynamic properties of the fog, a colloidal system, are very different from those of the water as a macrosystem in a beaker. In order to create the fog considerable work must be done to form a system with a much larger surface area. This means that the Gibbs energy of a fog containing the same number of water molecules as the beaker of water is much higher.
Streszczenia konferencji na temat "Air in liquid compound droplets"
1
Nakao, Yasuhiro, Naoki Horiguchi, Hiroyuki Yoshida, Tetsuya Kanagawa, Akiko Kaneko i Yutaka Abe. "Measurement of Flow Rate of Droplets and Liquid Film in Venturi Scrubber". W 2016 24th International Conference on Nuclear Engineering. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/icone24-60641.
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As one of filtered venting systems which should be installed in light water reactors from viewpoint of protecting a containment vessel and suppressing the diffusion of radioactive materials, there is a system composed of venturi scrubbers. The radioactive materials in the contaminated gas are collected into liquid. By dispersed flow formed in the venturi scrubber, large interfacial area between liquid and gas was obtained, and large decontamination factor is realized. In evaluation for the decontamination performance of the venturi scrubber, interface of droplets and liquid film are important. However, there is a little knowledge about the interfacial area in the venturi scrubber for filtered venting. In this study, to obtain the interfacial area data, amount of the droplets and the liquid film in the venturi scrubber is evaluated by visualizing observation and sampling the liquid film at the outlet of the venturi scrubber. In the venturi scrubber, a pressure drop occurs in the throat part by the inflow of air from the compressor. Water flows from the tank by a pressure difference between a suctioned hole with head pressure and a throat part. An annular spray flow is then formed in the venturi scrubber. Therefore, the liquid flow rate changes according to the gas phase flow rate. To discharge separately the droplets and the liquid film, a rectangular separator is installed at the venturi scrubber outlet. The superficial gas phase flow rate is 25.2–292.3 m/s in the throat. As a result, the liquid film and the droplets through the wall were confirmed to be discharged separately by the separator. The ratio of the liquid film to the total amount of liquid is 80 to 95% and that of the droplets was estimated as 5 to 20%. However, the change of the liquid film thickness caused by the increase of gas phase flow rates was observed. When the liquid film thickness is large, it is possible that some liquid film flowing into the droplet side.
2
Wei, Sheng, Brandon Sforzo i Jerry Seitzman. "Fuel Composition Effects on Forced Ignition of Liquid Fuel Sprays". W ASME Turbo Expo 2018: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/gt2018-77196.
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In gas turbine combustors, ignition is achieved by using sparks from igniters to start a flame. The process of sparks interacting with fuel/air mixture and creating self-sustained flames is termed forced ignition. Physical and chemical properties of a liquid fuel can influence forced ignition. The physical effects manifest through processes such as droplet atomization, spray distribution, and vaporization rate. The chemical effects impact reaction rates and heat release. This study focuses on the effect of fuel composition on forced ignition of fuel sprays in a well-controlled flow with a commercial style igniter. A facility previously used to examine prevaporized, premixed liquid fuel-air mixtures is modified and employed to study forced ignition of liquid fuel sprays. In our experiments, a wall-mounted, high energy, recessed cavity discharge igniter operating at 15 Hz with average spark energy of 1.25 J is used to ignite liquid fuel spray produced by a pressure atomizer located in a uniform air coflow. The successful outcome of each ignition events is characterized by the (continued) presence of chemiluminescence 2 ms after spark discharge, as detected by a high-speed camera. The ignition probability is defined as the fraction of successful sparks at a fixed condition, with the number of events evaluated for each fuel typically in the range 600–1200. Ten fuels were tested, including standard distillate jet fuels (e.g., JP-8 and Jet-A), as well as many distillate and alternative fuel blends, technical grade n-dodecane, and surrogates composed of a small number of components. During the experiments, the air temperature is controlled at 27 C and the fuel temperature is controlled at 21 C. Experiments are conducted at a global equivalence ratio of 0.55. Results show that ignition probabilities correlate strongly to liquid fuel viscosity (presumably through droplet atomization) and vapor pressure (or recovery temperature), as smaller droplets of a more volatile fuel would lead to increased vaporization rates. This allows the kernel to transition to a self-sustained flame before entrainment reduces its temperature to a point where chemical rates are too slow. Chemical properties of the fuel showed little influence, except when the fuels had similar physical properties. This result demonstrates that physical properties of liquid fuels have dominating effects on forced ignition of liquid fuel spray in coflow air.
3
Ponticaud, C., A. Grimaud, A. Denoirjean, P. Lefort i P. Fauchais. "Atmospheric Plasma Spraying of Ti Particles — In-Flight Particle Reactivity — Coating Properties". W ITSC2001, redaktorzy Christopher C. Berndt, Khiam A. Khor i Erich F. Lugscheider. ASM International, 2001. http://dx.doi.org/10.31399/asm.cp.itsc2001p0691.
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Abstract Titanium powder has been sprayed with nitrogen or Ar/H2 d.c. plasma jets flowing in air. Particles have been collected at several distances downstream of the nozzle exit. In the first 40- 60 mm, convective movements created within the liquid droplets entrain homogeneously nitrogen and oxygen in the particle cores. Farther downstream, convection is less important and absorption of nitrogen and oxygen is controlled by diffusion from the particles surface. After solidification induced by high quenching rates (in the order of 10 K/s) due to different cooling means, particles are composed by a superficial layer which is an oxi-nitride of titanium and in their core by a solid solution α-Ti containing both nitrogen and oxygen.
4
Rahman, Mosfequr, Andrew Hudson, Gustavo Molina i Valentin Soloiu. "Numerical Analysis of Laminar Natural Convection in Rectangular Enclosures of Different Aspect Ratios With and Without Aerosol Nanofluid". W ASME 2013 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/imece2013-65056.
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Natural convection heat transfer in rectangular enclosures is important in many real-world engineering applications. Included in these applications are the energy efficient design of buildings, operation and safety of nuclear reactors, solar collector design, passive energy storage, heat transfer across multi-pane windows, thermo-electric refrigeration and heating devices, and the design-for-mitigation of optical distortion in large-scale laser systems, environmental engineering and electronic packaging. A common industrial application of natural convection is free air cooling without the aid of fans and can happen on small scales such as computer chips to large scale process equipment. In addition to temperature gradient convection strength within the enclosure can vary due to the existence of nanoparticles with the base fluid. The field of nanofluid research has been expanding in recent years. Most of the research performed for the purpose of heat transfer using nanofluids has been conducted on liquid based nanofluids, leaving the aerosol-based nanofluid research lagging. There is also a deficit in the research previously performed to develop a computer model of heat transfer enhancement using nanofluid. The transport of solid particles and liquid droplets in a fluid has long been a subject of great interest. Understanding, measuring, and quantifying the deposition of aerosol on walls is important in various sectors of science and technology. Some examples are the deposition of drugs and harmful substances in the nasal and respiratory tracts in medical science and engineering; deposition of particles and droplets in gas and steam turbines in power plant engineering; the atmospheric dispersal of pollutants and the determination of indoor air quality in environmental science; the transport and sedimentation of various substances in rivers in civil engineering; fouling of process and heat transfer equipments in process industries; and the transport of chemical aerosols in chemical process engineering. In this research work the case of pure air was first solved for 6 different aspect ratios, then the nanofluid was introduced and the resulting heat transfer was observed. The aerosol nanofluid used was composed of air with copper nanoparticles suspended in an enclosure. This procedure was repeated for multiple aspect ratios. This research also develops a functional computer model for heat transfer enhancement using nanofluid.
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Voleník, K., B. Kolman, J. Dubský i P. Chráska. "In-Flight Behavior of Ni-Al Powder During Its Plasma Spraying". W ITSC2005, redaktor E. Lugscheider. Verlag für Schweißen und verwandte Verfahren DVS-Verlag GmbH, 2005. http://dx.doi.org/10.31399/asm.cp.itsc2005p1175.
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Abstract A Ni-Al pseudo-alloy powder was studied from the point of view of spheroidization during spraying by a water-stabilized plasma gun. The powder particles of irregular shape were conglomerates of elemental Ni and Al, the average Al content being 9.7 %. To conserve the shape and composition of particles flying in the plasma stream, these were trapped in liquid nitrogen. Scanning electron microscopy and X-ray microanalysis were used to obtain information about particle shape and element distribution. Most plasma sprayed particles trapped in liquid nitrogen were composed of a Ni-Al alloy, where the Al content varied in a wide range. Spherical "caps" composed of Al-oxide covered partially their surfaces. It follows that on the interface between molten Ni and Al, the interaction of both components gave rise to a Ni-Al alloy. On the contrary, if Al was exposed to air, it oxidized rapidly during the flight of the particles. The X-ray diffraction lines of the metallic phase in the particles trapped in liquid nitrogen were shifted from the positions corresponding to pure Ni as observed in the feedstock powder. This, together with the line asymmetry, showed the presence of Ni-Al alloy containing varying amounts of Al. The X-ray diffraction did not find any elemental Al in the liquid nitrogen trapped powder, i.e. neither in the metallic phase nor in the "caps". This means that all Al accessible to the ambient oxygen was converted into oxide. The "caps" contained metastable γ- and δ- Al2O3. The mechanism of the "cap" formation appears to be based on the fact that after an acceleration and melting period, significant slowing down of a molten particle occurs. Due to the drag forces, the lighter Al2O3 melt concentrates on the rear part of the droplet surface. The main condition, under which this mechanism holds, is the presence of two immiscible melts in the droplets and the significantly differing densities of both melts.
6
Gordon, Robert, Christos Markides i Epaminondas Mastorakos. "Autoignition of Liquid Fuel Droplets in a Turbulent Cross-Flow of Air". W 49th AIAA Aerospace Sciences Meeting including the New Horizons Forum and Aerospace Exposition. Reston, Virigina: American Institute of Aeronautics and Astronautics, 2011. http://dx.doi.org/10.2514/6.2011-794.
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Liu, L., Q. C. Bi, Victor I. Terekhov, Nikolay E. Shishkin, Liejin Guo, D. D. Joseph, Y. Matsumoto, Y. Sommerfeld i Yueshe Wang. "Experimental Investigation Evaporation of Liquid Mixture Droplets during Depressurization into Air Stream". W THE 6TH INTERNATIONAL SYMPOSIUM ON MULTIPHASE FLOW, HEAT MASS TRANSFER AND ENERGY CONVERSION. AIP, 2010. http://dx.doi.org/10.1063/1.3366370.
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Palaniappan, D. "Viscous Flows Involving a Liquid-Vapor Compound Droplet". W ASME 2001 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2001. http://dx.doi.org/10.1115/imece2001/fed-24942.
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Abstract Exact analytical solutions for steady-state axisymmetric creeping flows in and around a compound multiphase droplet are presented. The solutions given here explain the droplet fluid interactions in uniform and nonuniform flow fields. The compound droplet has a two-sphere geometry with the two spherical surfaces (of unequal radii) intersecting orthogonally. The surface tension forces are assumed to be sufficiently large so that the interfaces have uniform curvature. The singularity solutions for the uniform and paraboloidal flows in the presence of a compound droplet are derived using the method of reflections. The exact solutions for the velocity and pressure fields in the continuous and dispersed phases are given in terms of the fundamental singularities (Green’s functions) and their derivatives. It is found that flow fields and the drag forces depend on two parameters namely, the viscosity ratio and the radii ratio. In the case of paraboloidal flows, a single or a pair of eddies is noticed in the continuous phase for various values of these parameters. The eddies changes their size and shape if the size of the droplet is altered. These observations may be useful in the study of hydrodynamic interactions of compound droplets in complex situations. It is found that the Stokes resistance is greater when the liquid volume is large compared to the vapor volume in uniform flow. It is also noticed that the maximum value of the drag in paraboloidal flow depends on the viscosity ratio and significantly on the liquid volume in the dispersed phase. The exact solutions presented here may be useful for boundary integral formulations that are based on special kernels and also in validating numerical algorithms and codes on multiphase flow and droplet-fluid interactions.
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Chen, Morgan J., i Seyed A. Tabatabaei. "Broadband, Thin-Film, Liquid Crystal Polymer Air-Cavity Quad Flat No-Lead (QFN) Package". W 2009 Annual IEEE Compound Semiconductor Integrated Circuit Symposium. IEEE, 2009. http://dx.doi.org/10.1109/csics.2009.5315596.
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Armstrong, Robert L., i A. Zardecki. "Diffusive and convective evaporation of irradiated droplets". W International Laser Science Conference. Washington, D.C.: Optica Publishing Group, 1986. http://dx.doi.org/10.1364/ils.1986.thi7.
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The evaporation of a spherically symmetric liquid droplet subject to a high-irradiance laser flux is investigated on the basis of a hydrodynamic description of the system composed of the ejected vapor and ambient gas. For low irradiance beams, diffusive mass transport and conductive energy transport are the dominant interactions between the droplet and its environment.1 In this isobaric case, changes in the state of the ambient medium are small. For higher-flux beams, convective mass transport becomes significant, and droplet vaporization is accompanied by the production of strong shock waves in the surrounding gas. Following Knight,2jump conditions at the droplet boundary aid us in solving the hydrodynamic boundary value problem. An extension of Knight’s analysis to include both diffusive and convective mass flux allows the transition regime between the low-flux isobaric case and the high-flux shock-wave dominated case to be investigated. Numerical solutions illustrating droplet vaporization and ambient-medium hydrodynamic effects are presented for selected droplet-beam configurations.
Raporty organizacyjne na temat "Air in liquid compound droplets"
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Lawson. L51597 Feasibility Study of New Technology for Intake Air Filtration. Chantilly, Virginia: Pipeline Research Council International, Inc. (PRCI), czerwiec 1989. http://dx.doi.org/10.55274/r0010105.
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Inlet air filters are widely used to remove solids and liquid droplets from the ambient air before it enters the compressor of a gas turbine. Clean inlet air provides many advantages: Less corrosion of the compressor and of gas-path hot parts, such as the turbine, decreased compressor fouling, less erosion of the compressor bladeThese in turn prevent deterioration of output and heat rate, and reduce maintenance costs. Compressor fouling is caused by the ingestion of substances that deposit and adhere to blade surfaces, resulting in reduced aerodynamic efficiency and decreased available output. Air contamination could be significantly reduced by the use of more efficient air filtration systems, especially through the reduction of the quantity of smaller particles ingested. The consequent lower loss of output power and decreased cleaning efforts provide lower costs of operation and increased shaft power. This work was composed of three major efforts: 1) A literature search was performed to establish the state of the art for particle removal from gases, particularly by electrostatic precipitation, and to identify the leading vendors of the equipment-considering both experience and technical expertise. 2) Two chosen companies were visited to determine their technical capabilities as they apply to gas turbine inlet air filtration. 3) A representative gas turbine was specified by PRCI as being the equivalent of a GE Model 3002J turbine, with airflow of 91,200 acfm. A specification based upon that airflow was prepared and submitted to the two vendors. Each vendor prepared a proposal for a filter system compliant with the specification. The proposed air filtration equipment is sufficiently different from existing products that it was judged not beneficial to visit manufacturing facilities. Both vendors are reputable suppliers of air filtration equipment. This study is intended to provide definitive information relative to the use of new technology for air inlet filtration on gas turbines in gas pipeline pumping applications.