Journal articles: 'Hollow droplets'

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Vu, Truong V., Hiep T. Nguyen, and Nang X. Ho. "A numerical study of the coalescence of hollow droplets under solidification." Physics of Fluids 34, no. 5 (May 2022): 053318. http://dx.doi.org/10.1063/5.0093835.

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This paper presents the results of numerical simulations of the coalescence and solidification of two hollow droplets. A base droplet (i.e., a pre-solidified droplet) stays on a supercool surface that causes its shell liquid to solidify. An incoming droplet then flows toward and coalesces with the base droplet. After coalescence of the droplets, the two hollow cores can coalesce depending on the momentum of the incoming hollow core and the solidification rate. A high solidification rate corresponding to a high Stefan number St prevents the hollow cores from coalescing and thus induces a discrete hollow-core solidified product, whereas a low St number results in a coalesced hollow-core (CH) droplet. However, the coalescence of two droplets and/or their hollow cores does not affect the apex at the top of the final solidified droplet, which is created by volume expansion upon phase change. Some other parameters including the Peclet number Pe, the Weber number We, the size Ris of the incoming inner core, the position Hs of the incoming droplet and the number of cores Ni of the incoming droplet also affect the coalescence and phase transition of the droplets. It is found that transition from a CH region to a discrete hollow-core region occurs for lower Pe, Ris, or Ni. In contrast, decreasing the value of We or Hs enhances the CH region. Moreover, we provide regime diagrams based on the supercooling degree, the Peclet number, and the size of the inner core of the incoming droplet.

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Yao, Y. M., P. Joo, and S. C. Jana. "A Surfactant-Free Microfluidic Process for Fabrication of Multi-Hollow Polyimide Aerogel Particles." International Polymer Processing 35, no. 5 (November 1, 2020): 481–92. http://dx.doi.org/10.1515/ipp-2020-350510.

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Abstract This work focuses on fabrication of multi-hollow polyimide gel and aerogel particles from a surfactant-free oil-in-oil emulsion system using a microfluidic droplet generator operating under dripping mode. The multi-hollow gel and aerogel particles have strong potential in thermal insulation. Under jetting and tip-streaming regime of microfluidic flows, droplets are generated with no occluded liquid phase. The present study investigates a means of designing polyimide gel particles with plurality of internal liquid droplets by strategically manipulating the flow rates of the continuous and dispersed phase liquids through the microfluidic droplet generator. The multi-hollow polyimide aerogel particles obtained after supercritical drying of the gel particles present mesopores, high BET surface area, and excellent prospect for thermal insulation.

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Jabar, Ban, and Ahmed Abed al-Kadhem Majhool. "Visualization and Analysis Studies of Hollow Cone Spray under low Air Cross Flow Velocity under Atmospheric Condition." Al-Qadisiyah Journal for Engineering Sciences 12, no. 2 (July 30, 2019): 105–11. http://dx.doi.org/10.30772/qjes.v12i2.602.

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This study deals with the atomization of hollow cone spray water with low air cross ﬂow. The visualization of the hollow cone spray by shadowgraphy, from the nozzle exit. The diameter of the nozzle allows to observe diﬀerent modes of breakup and diﬀerent structures (ligaments, helices, ...). The treatment of these images makes it possible to determine the drop size distribution of the spray droplets in function of length scales of the downstream ﬂow. In the measurements of water hollow cone spray with injection pressures of 25kPa and air velocity of 10 m/sec. The calculations at the exit of the injector, in two planes perpendicular, and the average droplet sizes in the presence of air low cross ﬂow conditions. The structure and characteristics of the whole and sectional body of the spray are investigated at diﬀerent times. The results show the droplet trajectory proﬁle of the liquid droplets is in a good an agreement with analytical solution.

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Widiyastuti, W., Wei-Ning Wang, I. Wuled Lenggoro, Ferry Iskandar, and Kikuo Okuyama. "Simulation and experimental study of spray pyrolysis of polydispersed droplets." Journal of Materials Research 22, no. 7 (July 2007): 1888–98. http://dx.doi.org/10.1557/jmr.2007.0235.

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The size distribution and morphology of particles (dense or hollow) produced from polydispersed droplets in spray pyrolysis were studied both experimentally and theoretically. Zirconia, generated from a zirconyl hydroxychloride precursor, was selected as a model material. The simulation method that was previously developed by our group [J. Mater. Res., 15, 733 (2000)], in which droplets were assumed to be uniform, was improved to evaluate the effect of polydispersity in droplets on the size and morphology of the resulting particles. Simultaneous equations for heat and mass transfer of solvent evaporation and solute mass transfer inside droplets were solved numerically for a number of discrete classes of droplet size distribution. The role of the decomposition reaction was also included after the evaporation stage of polydispersed droplets in an attempt to explain the densification of particles. In hollow particle generation, this simulation was used to evaluate the thickness of a particle shell. The experimental results were in good agreement with the simulation data, suggesting that the model provides a more realistic prediction.

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Okamoto, Tatsuyuki, Toshimi Takagi, Toshikazu Kaji, Katsunori Shimazaki, and Kenji Nakanishi. "Studies on the Behavior of Droplets and the Air Flow in a Hollow-Cone Spray." Journal of Fluids Engineering 120, no. 3 (September 1, 1998): 586–92. http://dx.doi.org/10.1115/1.2820704.

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Experimental and numerical investigations are made on the behavior of droplets in a hollow-cone spray paying attention to the liquid sheet formed at the orifice of pressure-swirl atomizer. Simultaneous measurements of droplet sizes and velocities are made by phase-Doppler technique and numerical simulations are carried out based on the transient Eulerian equations for the gas and the Lagrangian equation for the droplets, taking account of the liquid sheet formed at the atomizer orifice. It is shown that the simulation gives good predictions by incorporating the existence of the liquid sheet. The predicted results indicate that the movement of the liquid sheet induces a strong air stream which acts as a strong side wind against the droplets immediately after breakup. This air stream selectively transports small droplets toward the central region and plays an essential role in the classification of droplets by size. Accordingly, the existence of the liquid sheet is significant for the characteristics of droplet dispersion and it should not be neglected in the prediction of hollow-cone spray flows. In addition, the shape of the liquid sheet is theoretically computed based on the simplified equations of motion. The comparison between the theoretical computation and the experimental result suggests that the surface tension of liquid is predominant in determining the shape of the liquid sheet.

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Zhang, Xiaoxuan, Lingyu Sun, Yu Wang, Feika Bian, Yuetong Wang, and Yuanjin Zhao. "Multibioinspired slippery surfaces with wettable bump arrays for droplets pumping." Proceedings of the National Academy of Sciences 116, no. 42 (September 30, 2019): 20863–68. http://dx.doi.org/10.1073/pnas.1912467116.

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Droplet manipulation is playing an important role in various fields, including scientific research, industrial production, and daily life. Here, inspired by the microstructures and functions of Namib desert beetles, Nepenthes pitcher plants, and emergent aquatic plants, we present a multibioinspired slippery surface for droplet manipulation by employing combined strategies of bottom-up colloidal self-assembly, top-down photolithography, and microstructured mold replication. The resultant multilayered hierarchical wettability surface consists of hollow hydrogel bump arrays and a lubricant-infused inverse opal film as the substrate. Based on capillary force, together with slippery properties of the substrate and wettability of the bump arrays, water droplets from all directions can be attracted to the bumps and be collected through hollow channels to a reservoir. Independent of extra energy input, droplet condensation, or coalescence, these surfaces have shown ideal droplet pumping and water collection efficiency. In particular, these slippery surfaces also exhibit remarkable features including versatility, generalization, and recyclability in practical use such as small droplet collection, which make them promising candidates for a wide range of applications.

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Takahashi, Minoru, Arun Kumar Nayak, Shin-ichi Kitagawa, and Hiroyuki Murakoso. "Heat Transfer in Direct Contact Condensation of Steam to Subcooled Water Spray." Journal of Heat Transfer 123, no. 4 (January 30, 2001): 703–10. http://dx.doi.org/10.1115/1.1370510.

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The condensation heat transfer of saturated steam to a hollow-cone spray of subcooled water was investigated experimentally and analytically. The spray water temperature rose more steeply in flow direction than those in the previous studies, because of the use of smaller thermocouple which was capable of measuring the temperature in a thin water sheet and water droplets more accurately. The result of the condensation heat transfer coefficient suggested the breakup of the water sheet into droplets. A pure conduction model underpredicted the heat transfer in the sheet region significantly, which was better predicted by considering turbulence in the sheet. The heat transfer in the droplet region was well estimated by considering internal circulation and mixing inside the droplets.

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Chen, Hongyue, Yongjian Zhang, Heyi Wang, Xin Dong, and Duyang Zang. "Evaporation Caused Invaginations of Acoustically Levitated Colloidal Droplets." Nanomaterials 13, no. 1 (December 27, 2022): 133. http://dx.doi.org/10.3390/nano13010133.

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Controlled buckling of colloidal droplets via acoustic levitation plays an important role in pharmaceutical, coating, and material self-assembly. In this study, the evaporation process of PTFE colloidal droplets with two particle concentrations (60 wt% and 20 wt%) was investigated under acoustic levitation. We report the occurrence of surface invagination caused by evaporation. For the high particle concentration droplet, the upper surface was invaginated, eventually forming a bowl-shaped structure. While for the low particle concentration droplet, both the upper and lower surfaces of the droplet were invaginated, resulting in a doughnut-like structure. For the acoustically levitated oblate spherical droplet, the dispersant loss at the equatorial area of the droplet is greater than that at the two poles. Therefore, the thickness of the solid shell on the surface of the droplet was not uniform, resulting in invagination at the weaker pole area. Moreover, once the droplet surface was buckling, the hollow cavity on the droplet surface would absorb the sound energy and results in strong positive acoustic radiation pressure at bottom of the invagination, thus further prompting the invagination process.

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Gebhardt, Maurice R. "Rotary Disk Atomization." Weed Technology 2, no. 1 (January 1988): 106–13. http://dx.doi.org/10.1017/s0890037x00030189.

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In the late 1930s, European engineers discovered that, for very low flow rates, rotary disk atomizers produced a more definable range of droplet sizes than hydraulic atomizers. In the late 1970s, a cup-like spinning atomizer was developed to apply herbicides at low and ultra-low volumes. Rotary atomizers distribute droplets in a pattern similar to hollow cone nozzles. The droplet trajectory could affect deposits adversely since droplets released horizontally are exposed to wind and other environmental effects longer than hydraulic spray nozzles. Propellers and fans were used to enhance downward movement of droplets without considering that droplet impingement velocity was critical for efficient deposition. In the early 1980s, rotary atomizers were promoted to reduce herbicide rates, but the claims were products of unconfirmed testing. Herbicide efficacy in confirmed research was not influenced by application with the rotary atomizer, but lower carrier rates reduced the amount of water handled during the spraying operation. The cost of the atomizer, more maintenance, and greater care during operation with no decrease in herbicide rates discourage continued use.

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Wang, Hong Cheng, Li Jun Yang, Jia Liu, and Zhen Dong Dai. "Controlled Encapsulation of Micron-Sized Beads in a Droplet Based on Pulse Inertia Force Driving of Micro-Fluids." Key Engineering Materials 645-646 (May 2015): 1009–15. http://dx.doi.org/10.4028/www.scientific.net/kem.645-646.1009.

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Loading drops with discrete objects, such as particles and cells, is often necessary when performing chemical and biological assays in microfluidic devices. The vast majority of reported encapsulating methods of particles into monodisperse picolitre droplets are based on micro-fluidic chip using the standard soft lithography technique are necessary. This paper presents a new approach, not based on micro-fluidic chip, for encapsulating particles into droplets actuated by microfluidic pulse inertia force. The polystyrene bead suspension can be ejected out of a tapered glass capillary in mineral oil drop by drop actuated by an enough pulse inertia force which is produced by a hollow PZT stack. The polystyrene beads will be randomly encapsulated in monodisperse picolitre droplets. The tapered glass capillary has the advantages of good chemical resistance, low friction, easy to manufacture and low cost and is suitable for chemical and biological analysis. The minimum size of the spherical droplets can reach 12 μm in diameter and about 1 picolitre in volume. The percentage of the droplets with single 5 μm-diameter polystyrene bead can reach 40% when the droplet size is 40 μm and the concentration of the bead suspension is 1×107 beads per milliliter. The experiment result can be applied in droplet-based single cell encapsulating and analyzing.

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Cao, Na, Liang Cao, Chang Cai Han, Qing Xu, Lan Lei, Ji Ye Du, Jun Xue, and Zhan Hong Zhang. "A Study of the Spray Characterization from a Centrifugal Nozzle by Pulsed Laser Holography." Applied Mechanics and Materials 152-154 (January 2012): 846–51. http://dx.doi.org/10.4028/www.scientific.net/amm.152-154.846.

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Centrifugal nozzle is an important part of an areoengine in which fuel atomization has strong influence on engine performance. For investigating the fuel spray characteristics, a promising method named off-axis particle holographic measuring system is used here. Characteristics of the nonevaporating spray ejected from a new type of centrifugal nozzle which would be used in the near future are obtained under various injection conditions. By automatic analysis of the holographic reconstructed droplets images, a hollow-cone shape spray with most droplets concentrated in the surface of the cone is observed, and the spray cone angle, droplet sizes and their spatial locations in concerned region are obtained quantitativly. In the near region of the nozzle exit, droplets show greater SMD value, while at a certain distance from the nozzle, the droplets SMD differences become unconspicuous which shows a better atomization. These informations are helpful to understand characteristics of the centrifugal nozzle and offer a database for validating the spray simulation code.

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Baesso, Murilo Mesquita, Francelino Augusto Rofrigues Junior, Ronaldo Goulart Magno Junior, Mauri Martins Teixeira, and Alcir Jose Modolo. "POPULATION AND SPECTRUM OF DROPLETS PRODUCED DURING ELECTROSTATIC SPRAYING AND HYDRAULIC SPRAYING USING AIR ASSISTANCE - DOI: 10.13083/1414-3984.v22n05a02." REVISTA ENGENHARIA NA AGRICULTURA - REVENG 22, no. 5 (October 23, 2014): 408–12. http://dx.doi.org/10.13083/reveng.v22i5.427.

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The droplet population produced during spraying influences the efficiency of pesticide application. It is possible to define a minimum number of droplets per unit area depending on the treatment and product to be applied. This study aimed to evaluate the characteristics of the populations and the spectra of droplets produced during electrostatic and air-assisted spraying. Factors including types of nozzles, spray volume, type of spray and its influence on the percentage coverage and density of droplet population. The experiment was arranged in a 2 x 2 x 2 factorial [two types of nozzles (Jacto JA-4, hollow cone and Jacto AXI-110-04, flat fan nozzle tip), two spray volumes (200 L ha-1 and 400 L ha-1) and two sprayer types (air-assistance in the spraying sleeve boom and electrostatic spraying)] in a randomized block design with four replications. The electrostatic sprayer increased droplet density per cm2 of leaf.

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Bayer, Tânia, Milton F. Cabezas-Guerrero, Casimiro D. Gadanha Junior, and Alci E. Loeck. "Systems and rates of aerial application of fungicides in irrigated rice." Revista Brasileira de Engenharia Agrícola e Ambiental 22, no. 2 (February 2018): 143–47. http://dx.doi.org/10.1590/1807-1929/agriambi.v22n2p143-147.

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ABSTRACT The present research studied the performance of flat-fan and hollow-cone nozzles, with application rates of 20 and 30 L ha-1, and rotary disc atomizer with application rates of 10 and 15 L ha-1. The test was conducted with a fungicide spray tank composed of Azoxystrobin + Difenoconazole, in which the density and penetration of droplets into the canopy were evaluated using a water-sensitive paper and the distribution of the active ingredients in the plant was evaluated through the chromatographic analysis. Higher application rates resulted in higher droplet density in the upper stratum of plants. In all treatments, the penetration of the droplets was 26% into the middle stratum and 23% into the lower stratum, in relation to the top of the crop, resulting in an average 25% penetration of droplets into the leaf canopy. The active ingredients were distributed in greater quantity in the upper stratum of the plant. For the same weight, the upper part of the ‘Puitá Inta CL’ rice cultivar has a leaf area 6.4 times larger than the lower part. It was concluded that higher application rate leads to higher droplet density in the upper stratum of the leaf canopy and that all systems and application rates promoted similar penetration of droplets into the canopy.

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Leun, E. V. "The basics of construction of jet-drop optical systems for measuring electric field strength. Parth 2." Omsk Scientific Bulletin, no. 181 (2022): 78–88. http://dx.doi.org/10.25206/1813-8225-2022-181-78-88.

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In this part of the article, the discussion of the construction of jet-drop optical measuring systems (JDOMS) for monitoring the electric field strength continues. The possibilities of increasing the resolution are considered. A variant of the interference JDOMS using triangulation stroboscopic measurements of displacements of charged moving droplets using a pulsed acousto-optic interferometer of transverse displacements of a laser beam is presented. The possibilities of increasing the charge/mass ratio of charged droplets, the features of using liquid metals and their two- and three-component alloys as liquids, the use of inhomogeneous droplets in the form of hollow, hollow microspheres similar to soap bubbles and/or based on a porous (dispersed) material are discussed.

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Vladisavljevic, Goran, Sabine Brösel, and Helmar Schubert. "Characterization of water-in-oil emulsions produced with microporous hollow polypropylene fibers." Journal of the Serbian Chemical Society 65, no. 11 (2000): 829–37. http://dx.doi.org/10.2298/jsc0011829v.

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The preparation of fine and monodispersed water-in-oil (W/O) emulsions by utilizing hydrophobic hollow polypropylene fibers with 0.4 mm pores was investigated in this work. The experiments were carried out using demineralized water as the disperse phase, mineral oil Velocite No. 3 as the continuous phase, and polyglycerol polyricinoleate (PGPR 90) in the concentration range of 2.5 - 10 wt % as the oil-soluble emulsifier. The size of the water droplets in the prepared emulsions and the droplet size distribution strongly depend on the content of the disperse phase, the transmembrane pressure difference, and the emulsifier concentration. Stable emulsions with a very narrow droplet size distribution and a mean droplet diameter lower than 0.27 ?m were produced using 10 wt % PGPR 90 at a pressure difference below 30 kPa.

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Mishra, Yogeshwar Nath, Timo Tscharntke, Elias Kristensson, and Edouard Berrocal. "Application of SLIPI-Based Techniques for Droplet Size, Concentration, and Liquid Volume Fraction Mapping in Sprays." Applied Sciences 10, no. 4 (February 18, 2020): 1369. http://dx.doi.org/10.3390/app10041369.

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Structured laser illumination planar imaging (SLIPI)-based techniques have been employed during the past decade for addressing multiple light scattering issues in spray imaging. In this article, SLIPI droplet sizing based on the intensity ratio of laser-induced fluorescence (LIF) over Mie scattering (SLIPI-LIF/Mie) and SLIPI-Scan for extinction-coefficient (µe) mapping are applied simultaneously. In addition, phase Doppler anemometry (PDA) and numerical calculations based on the Lorenz–Mie theory are also employed in order to extract the droplets Sauter mean diameter (SMD), the droplets number density (N), and the liquid volume fraction (LVF) in a steady asymmetric hollow cone water spray. The SLIPI-LIF/Mie ratio is converted to droplets SMD by means of a calibration procedure based on PDA measurements. The droplet SMD for the investigated spray varies from 20 µm to 60 µm, the N values range from 5 to 60 droplets per mm3, and the LVF varies between 0.05 × 10−4 and 5.5 × 10−4 within the probed region of the spray. To generate a series of two-dimensional images at different planes, the spray scanning procedure is operated in a “bread slicing” manner by moving the spray perpendicularly to the light sheet axis. From the resulting series of images, the procedure described here shows the possibility of obtaining three-dimensional reconstructions of each scalar quantity, allowing a more complete characterization of droplet clouds forming the spray region.

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Helling, Tobias, Florian Reischl, Andreas Rosin, Thorsten Gerdes, and Walter Krenkel. "Atomization of Borosilicate Glass Melts for the Fabrication of Hollow Glass Microspheres." Processes 11, no. 9 (August 26, 2023): 2559. http://dx.doi.org/10.3390/pr11092559.

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Direct atomization of a free-flowing glass melt was carried out using a high-speed flame with the aim of producing tiny, self-expanding glass melt droplets to form hollow glass microspheres. Atomization experiments were carried out using a specially adapted free-fall atomizer in combination with a high-power gas burner to achieve sufficient temperatures to atomize the melt droplets and to directly expand them into hollow glass spheres. In addition, numerical simulations were carried out to investigate non-measurable parameters such as hot gas velocities and temperatures in the flame region by the finite volume-based software Star CCM+® (v. 2022.1.1), using the Reynolds-Averaged Navier–Stokes (RANS) turbulence and the segregated flow model. To calculate the combustion process, the laminar flamelet method was used. The experiments and simulations indicated that a maximum gas velocity of about 170 m/s was achieved at the point of atomization in the flame. The particle size distribution of the atomized glass droplets, either solid or hollow, ranged from 2 µm to 4 mm. Mean particle sizes in the range of 370 µm to 650 µm were highly dependent on process parameters such as gas velocity. They were in good agreement with theoretically calculated median diameters. The formation of hollow glass microspheres with the proposed concept could be demonstrated. However, only a small fraction of hollow glass spheres was found to be formed. These hollow spheres had diameters up to 50 µm and, as expected, a thin wall thickness.

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He, Yanping, Xin Li, Tianci Zhu, Mengxing Shan, Linhua Zhu, Tian Si, Hong Wang, and Yanlin Sun. "Controlling the Internal Structures of Polymeric Microspheres via the Introduction of a Water-Soluble Organic Solvent." Polymers 10, no. 7 (July 18, 2018): 789. http://dx.doi.org/10.3390/polym10070789.

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Polymeric microspheres with different internal structures have been widely used because of their characteristics in the structures. This paper reports a method of controlling the internal structures of polymeric microspheres via the introduction of a water-soluble organic solvent to the continuous phase in the foam phase preparation of porous polymeric microspheres. The introduction of a water-soluble organic solvent enables the control of polymeric microspheres’ internal structures, from porous to hollow. Because a water-soluble organic solvent is introduced, the organic solvent may be diffused toward the interface because of the affinity between the organic solvent and the oil droplets, resulting an accumulation of organic solvent molecules at the interface to form an organic solvent layer. The presence of this layer may decrease the evaporation rate of the internal organic solvent in an oil droplet, which extends the time for the mingling of porogen droplets to form a few large pores or even an extremely large single pore inside. This method is also capable of altering the thickness of hollow microspheres’ shells in a desired way, with improved efficiency, yield and the capacity for continuous use on an industrial scale.

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Wu, Wangxia, Bing Wang, and Gaoming Xiang. "Impingement of high-speed cylindrical droplets embedded with an air/vapour cavity on a rigid wall: numerical analysis." Journal of Fluid Mechanics 864 (February 15, 2019): 1058–87. http://dx.doi.org/10.1017/jfm.2019.55.

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The high-speed impingement of hollow droplets embedded with a cavity has fundamental applications in various scenarios, such as in spray coating and biomedical engineering. The impingement dynamics is modulated by the wrapping medium, different from that of denser solid droplets. With air and vapour cavities, the impingement of two kinds of hollow cylindrical droplets is simulated in the present study to investigate the morphology and physical mechanisms regarding droplet and cavity dynamics. The compressible two-phase Eulerian model is used to couple with the phase transition procedure. The results detail the evolution of droplets and collapsing dynamics of the two kinds of cavities. Processes are captured in which the impinging water-hammer shock wave interacts with the cavity, and vertical liquid jets are induced to impact the embedded cavity. For the case of the air cavity, a transmitted shock wave is formed and propagates inside the cavity. The air cavities are compressively deformed and broken into a series of small cavities. Subsequently, a range of intermittent collapsing compression wavelets are generated due to the interface collapse driven by local jets. As for the vapour cavity in the saturated state, initially, once it is impacted by the impinging shock wave, it gradually shrinks accompanied by local condensation but without generation of transmitted waves. Following the first interaction between the lower and upper surfaces of the cavity, the vapour cavity undergoes continuous condensation and collapse with repeated interface fusion. The vapour cavity finally turns into liquid water blended into the surroundings, and the strong collapsing shock waves are expanded inside the droplet. The radius ratios and initial impinging speeds are chosen to analyse the variation of the collapsing time, maximum collapsing pressure and mean pressure on the rigid wall. The pressure withstood by the wall due to the collapsing cavity increases with the initial size of the cavity and initial impinging speed. The maximum local pressures in the entire fluids and the mean pressure on the wall during the collapsing of the vapour cavities are higher than those for the air cavities.

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Pochert, Alexander, Sebastian Ziller, Sasa Kapetanovic, Gregor Neusser, Christine Kranz, and Mika Lindén. "Intermediate pickering emulsion formation as a means for synthesizing hollow mesoporous silica nanoparticles." New Journal of Chemistry 40, no. 5 (2016): 4217–22. http://dx.doi.org/10.1039/c5nj02855h.

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Leun, E. V. "The basics of construction of jet-drop optical systems for measuring the electric field strength. Part 1." Omsk Scientific Bulletin, no. 178 (2021): 83–90. http://dx.doi.org/10.25206/1813-8225-2021-178-83-90.

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The article discusses the principles and possibilities of using jet-drop optical measuring systems for monitoring the electric field strength (EFS). Two applied techniques are considered. First, the deflection of flying charged droplets (balls, hollow granules) used as micro-objects sensitive to EFS and deviating from a given rectilinear trajectory of motion, like an electron in a kinescope. Secondly, stroboscopic determination of the position and/or displacement of drops by pulsed illumination of the side of the deflected drop by the optical flow and measurement of the reflection angle for it. The possibilities of implementing the differential method of EFS measurements are discussed. The features of the use of liquids with the addition of metal nanopowders or based on liquid metals, as well as hollow droplets in the form of microspheres or hollow granules are considered

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Zhang, Xiaoli, Juan Wei, and Xiaoming Zhang. "Encapsulated liquid nano-droplets for efficient and selective biphasic hydroformylation of long-chain alkenes." New Journal of Chemistry 43, no. 35 (2019): 14134–38. http://dx.doi.org/10.1039/c9nj02493j.

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Cai, Xu Dong, Jian Jiang Wang, Bao Cai Xu, Hong Fei Lou, and Xing Jian Huo. "Hollow Multiphase Ceramic Microspheres of Al+Cr₂O₃+SiO₂ System Prepared by Self-Reaction Quenching Technology." Key Engineering Materials 512-515 (June 2012): 621–25. http://dx.doi.org/10.4028/www.scientific.net/kem.512-515.621.

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This paper aims to study preparation and mechanism of hollow ceramic microspheres. With Al+Cr2O3+SiO2+sucrose+epoxy resin as reactive system, Al2O3-based hollow ceramic microspheres are synthesized and reaction mechanism of hollow ceramic microspheres is established. Results show that the quenching products consist of hollow spherical or irregularly spherical particles and irregularly powders. Spherical or irregularly spherical particles are hollow structure and constitutive of Al2O3-SiC diphase and a few Cr3Si、Cr7C3. The preparation of hollow ceramic microspheres includes igniting by heating, forming ceramic thawy droplets and fast cooling. The great deal of air produced by burning epoxy resin and sucrose is the key reason why hollow ceramic microspheres are formed.

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van Wijk, Judith, Tiaan Heunis, Elrika Harmzen, Leon M. T. Dicks, Jan Meuldijk, and Bert Klumperman. "Compartmentalization of bacteria in microcapsules." Chem. Commun. 50, no. 97 (2014): 15427–30. http://dx.doi.org/10.1039/c4cc04901b.

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Lactobacillus plantarum strain 423 was encapsulated in hollow poly(organosiloxane) microcapsules by templating water-in-oil Pickering emulsion droplets via the interfacial reaction of alkylchlorosilanes.

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Glahn, A., M. F. Blair, K. L. Allard, S. Busam, O. Scha¨fer, and S. Wittig. "Disintegration of Oil Films Emerging From Radial Holes in a Rotating Cylinder." Journal of Engineering for Gas Turbines and Power 125, no. 4 (October 1, 2003): 1011–20. http://dx.doi.org/10.1115/1.1586311.

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A fundamental study has been performed to examine the disintegration of oil films emerging from radial holes in a rotating hollow cylinder. The configuration investigated is an abstraction of one of the droplet generation sources in an aeroengine bearing compartment; similar configurations may also occur inside gearboxes. The paper aims to contribute to both the determination of directly applicable droplet characteristics and the establishment of a database that can be used for the development of droplet generation models. Similar to a prior paper on droplet generation processes at the rim of a rotating disk (Glahn, A. et al., 2000, “Droplet Generation by Disintegration of Oil Films at the Rim of a Rotating Disk,” ASME Paper No. 2000-GT-0279.) the near-term objectives of the study are (i) to determine droplet sizes under relevant aeroengine bearing compartment operating conditions, and (ii) to measure individual droplet diameter/velocity relationships. The long-term objective is to incorporate this information into advanced CFD-based design tools. Therefore, special emphasis has been directed towards a correlation of test results that enables determination of boundary conditions for a two-phase (oil droplets/air) simulation of lubrication system components. Based on the results of the present paper, droplet flow boundary conditions in terms of mean diameter, standard deviation of the diameter distribution, starting velocity, and flow angle are available for oil droplets generated by disintegration of oil films emerging from rotating radial holes and rotating disks.

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Liu, Jay G., and David L. Wilcox. "Factors influencing the formation of hollow ceramic microspheres by water extraction of colloidal droplets." Journal of Materials Research 10, no. 1 (January 1995): 84–94. http://dx.doi.org/10.1557/jmr.1995.0084.

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Hollow ceramic microspheres of Al2O3, SiO2, and mullite have been prepared by the combination of an emulsion technique with a water extraction sol-gel method. Concentration of sol, initial droplet size, and water extraction rate of the system are found to be the important process parameters controlling the size and wall thickness of the hollow microspheres, and their influences are shown. A model that correlates the morphology of microspheres to concentration and water extraction rate is proposed and is in good agreement with the experimental observations. The capability and limitation of this process for forming hollow microspheres are demonstrated. It was shown that hollow microspheres with sizes greater than 5 μm could be readily prepared, while a limitation was met for sizes less than 1 μm, in which case solid microspheres were normally formed.

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Liu, Xianbin, Hejun Du, Zhiyuan Zeng, and Xiao Wei Sun. "Controlled Synthesis of Hollow Hemispheric ZnO Shells/Cages on Graphite Fiber." ISRN Nanotechnology 2011 (June 8, 2011): 1–5. http://dx.doi.org/10.5402/2011/823216.

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Hollow hemispheric ZnO shells/cages are synthesized on graphite fiber via simple thermal evaporation process. The cage-like ZnO structures exhibit micron or submicron size and hollow hemispheric shape with polycrystalline shell made of the ZnO nanocrystals. Controlled time-sequenced growth experiment is conducted to interpret the growth process, which indicates that the growth mechanism of the hollow hemispheric ZnO shells/cages involves formation of Zn particles firstly, followed by oxidation of the outer surface of Zn droplets and meantime sublimation of the core Zn.

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Abraheem, Sajjad N., and Majid H. Alheidary. "Evaluation of Spray Droplets Characteristics Depending on the Configuration of Boomless Nozzle." IOP Conference Series: Earth and Environmental Science 1060, no. 1 (July 1, 2022): 012128. http://dx.doi.org/10.1088/1755-1315/1060/1/012128.

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Abstract Using hollow cone nozzles is a common in different spraying processes for controlling the pests. The aim of the study was to evaluate the spray droplet characteristics deposited on the eggplant plants at flowering vegetative growth stage. The study was performed in a Complete Block Random Design (CBRD) with a 3x4 factorial scheme, consisting of three working pressures 2, 3, and 5 bar, and four spray patterns of nozzles with three blocks. For obtaining micro details about spray droplets characteristics, white paper cards were used, which later had their images digitized and analyzed by the ImageJ software. The following values were measured in this study: volume median droplet diameter, spray coverage percentage, and droplet density per centimeter square. Then, the values found were subjected to analysis to show the significance between them. These values were compared by t test at 5% probability level. For each factor, separately, the coefficients of variation were analyzed and then the correlation between these factors was performed. The main results showed that the spray droplet characteristics were affected by both of operating pressure and spray pattern configuration. Higher operating pressure of 5bar produced the smallest median diameter and greatest number of droplets, and spray coverage percentage. Results also showed that the using of a combination spray pattern led to an increase in droplet density thereby coverage percentage into plant canopy in comparison to other pattern configurations.

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Jiang, Yan Qiu, Ye Tang Pan, Xiao Wei Li, Wen Jing Cheng, Jian Min Sun, Kai Feng Lin, and Zi Chen Wang. "Preparation and Characterization of Hollow Spheres with Cubic Mesoporous Shell." Advanced Materials Research 785-786 (September 2013): 382–85. http://dx.doi.org/10.4028/www.scientific.net/amr.785-786.382.

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This work demonstrated an approach of oil/water (O/W) microemulsion on preparation of hollow spheres with mesopores in the shell, in which a cationic surfactant was used as structural directing agent, alkane molecule as mesopore-swelling agent and oil droplets. The morphology and pore architecture of the obtained hollow spheres were characterized by SEM, XRD, TEM and N2adsorption/desorption isotherms. Cubic (Ia3d) mesopores are present in the shell and provide open channels for mass transport in between the hollow core and outer environment. The obtained hollow spheres with cubic mesoporous shell possess the potential of being used as nanoreactor and nanocontainer in the fields of catalysis and drug delivery.

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Liu, Yang, Xinlong Sun, Feng Zhao, Fei Zhan, Bo Zhang, Jun-Heng Fu, Lei Wang, and Jing Liu. "Controllable preparation of an ice cream-shaped hollow sphere array." RSC Advances 12, no. 15 (2022): 8936–39. http://dx.doi.org/10.1039/d2ra00236a.

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In a hydrothermal environment, EGaIn liquid droplets in hole arrays transfer from liquid state into solid hollow spheres. They hold much air between the solid and liquid interface, enhancing the thermal insulation and superhydrophobic performance.

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Kabil, Islam, Mansour Al Qubeissi, Jihad Badra, Walid Abdelghaffar, Yehia Eldrainy, Sergei S. Sazhin, Hong G. Im, and Ahmed Elwardany. "An Improved Prediction of Pre-Combustion Processes, Using the Discrete Multicomponent Model." Sustainability 13, no. 5 (March 8, 2021): 2937. http://dx.doi.org/10.3390/su13052937.

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An improved heating and evaporation model of fuel droplets is implemented into the commercial Computational Fluid Dynamics (CFD) software CONVERGE for the simulation of sprays. The analytical solutions to the heat conduction and species diffusion equations in the liquid phase for each time step are coded via user-defined functions (UDF) into the software. The customized version of CONVERGE is validated against measurements for a single droplet of n-heptane and n-decane mixture. It is shown that the new heating and evaporation model better agrees with the experimental data than those predicted by the built-in heating and evaporation model, which does not consider the effects of temperature gradient and assumes infinitely fast species diffusion inside droplets. The simulation of a hollow-cone spray of primary reference fuel (PRF65) is performed and validated against experimental data taken from the literature. Finally, the newly implemented model is tested by running full-cycle engine simulations, representing partially premixed compression ignition (PPCI) using PRF65 as the fuel. These simulations are successfully performed for two start of injection timings, 20 and 25 crank angle (CA) before top-dead-centre (BTDC). The results show good agreement with experimental data where the effect of heating and evaporation of droplets on combustion phasing is investigated. The results highlight the importance of the accurate modelling of physical processes during droplet heating and evaporation for the prediction of the PPCI engine performance.

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Qu, Ying Dong, Chong Jiang, Xiao Hong Li, Rui Ming Su, and Rong De Li. "Effect of Charge Action on the Annular Molten Metal of Spray Forming." Applied Mechanics and Materials 217-219 (November 2012): 1890–93. http://dx.doi.org/10.4028/www.scientific.net/amm.217-219.1890.

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This paper described the effect of hollow jet atomization technology, under charge action, according to the spray forming process, to improve the quality of atomization. In order to deeply study the charge action on the annular molten metal of spray forming process, this paper analyzed theoretically quantity of electric charge of the annular molten metal and the surface tension of atomization droplets. The results show that the quantity of electric charge increases with the increasing of charging voltage. Under the same conditions, the hollow annular metal liquid charge is always greater than the solid cylindrical molten metal charge, but the surface tension is less than the solid molten metal. As the quantity of electric charge reduce the surface tension of the droplet, the power of atomization increases relatively. It means that the atomization quality of annular molten metal will be better than the solid cylindrical molten metal. By comparison, the structure under charge action is fine and homogeneous after experiment.

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Jans, Alexander, Jonas Lölsberg, Abdolrahman Omidinia-Anarkoli, Robin Viermann, Martin Möller, Laura De Laporte, Matthias Wessling, and Alexander J. C. Kuehne. "High-Throughput Production of Micrometer Sized Double Emulsions and Microgel Capsules in Parallelized 3D Printed Microfluidic Devices." Polymers 11, no. 11 (November 15, 2019): 1887. http://dx.doi.org/10.3390/polym11111887.

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Double emulsions are useful geometries as templates for core-shell particles, hollow sphere capsules, and for the production of biomedical delivery vehicles. In microfluidics, two approaches are currently being pursued for the preparation of microfluidic double emulsion devices. The first approach utilizes soft lithography, where many identical double-flow-focusing channel geometries are produced in a hydrophobic silicone matrix. This technique requires selective surface modification of the respective channel sections to facilitate alternating wetting conditions of the channel walls to obtain monodisperse double emulsion droplets. The second technique relies on tapered glass capillaries, which are coaxially aligned, so that double emulsions are produced after flow focusing of two co-flowing streams. This technique does not require surface modification of the capillaries, as only the continuous phase is in contact with the emulsifying orifice; however, these devices cannot be fabricated in a reproducible manner, which results in polydisperse double emulsion droplets, if these capillary devices were to be parallelized. Here, we present 3D printing as a means to generate four identical and parallelized capillary device architectures, which produce monodisperse double emulsions with droplet diameters in the range of 500 µm. We demonstrate high throughput synthesis of W/O/W and O/W/O double emulsions, without the need for time-consuming surface treatment of the 3D printed microfluidic device architecture. Finally, we show that we can apply this device platform to generate hollow sphere microgels.

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Zhang, Yueheng, Yang Su, Yingqing Wang, Jibao He, Gary L. McPherson, and Vijay T. John. "Rapid fabrication of hollow and yolk–shell α-Fe2O3 particles with applications to enhanced photo-Fenton reactions." RSC Advances 7, no. 62 (2017): 39049–56. http://dx.doi.org/10.1039/c7ra06621j.

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Rutkevičius, Marius, Georg H. Mehl, Jordan T. Petkov, Simeon D. Stoyanov, and Vesselin N. Paunov. "Fabrication of salt–hydrogel marbles and hollow-shell microcapsules by an aerosol gelation technique." Journal of Materials Chemistry B 3, no. 1 (2015): 82–89. http://dx.doi.org/10.1039/c4tb01443j.

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We discovered a way to make hydrogel marbles with hydrophilic particles by rolling gelled aerosol droplets in a bed of salt microcrystals which after sieving and drying of the hydrogel cores yielded hollow-shell salt microcapsules.

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36

Hou, Yong-shen. "Effect of Heat Treatment on Preparation of Ferrite Magnetite Hollow Beads by Self-Propagating Method." Journal of Physics: Conference Series 2174, no. 1 (January 1, 2022): 012022. http://dx.doi.org/10.1088/1742-6596/2174/1/012022.

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Abstract The characterization results of hollow ceramic beads show that oxidant KClO3 had a great influence on the preparation of hollow ceramic beads. The morphology picture and XRD analysis showed that the surface of hollow beads without KClO3 was smooth, and the particle size analysis results show that the particle size was 10 ~ 50μm. Without KClO3, the average particle size is 28.08 μm; After adding KClO3, dense dendritic crystal structure was distributed on the surface of hollow beads, and the phase is mainly BaFe2O4, and the distribution range of hollow beads is 5 ~ 40 μm, and the average particle size is 16.02 μm° It could be inferred from the analysis that the quenching reaction is fully carried out after the addition of KClO3, resulting in a large amount of gas, reducing the volume of ceramic droplets and reducing the particle size of hollow beads.

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37

Liu, Shi Quan, Jian Cun Rao, Hai Xia Wang, and Hui Zhao. "A Simple Synthesis of Mesoporous Silica Hollow Microspheres by Fast Hydrolysis and Condensation of Tetraethyl Orthosilicate." Advanced Materials Research 189-193 (February 2011): 4335–38. http://dx.doi.org/10.4028/www.scientific.net/amr.189-193.4335.

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Mesoporous silica hollow microspheres were quickly synthesized with a simple reaction medium which only contains tetraethylorthosilicate (TEOS) as silica source, octylamine (OA) as template and water. It is proposed that a dispersion of TEOS-in-water is formed when water is added into the mixture of TOS and OA. Water becomes basic due to dissolution of OA. Fast hydrolysis and condensation of TEOS then occurs at the interface of droplets lead to the formation of silica shells. Hollows are formed due to the volume contraction caused by the large difference in the densities of condensed silica and liquid TEOS. In addition, OA assembles with silica, templating the nanopores in the silica shells.

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Kumar, Arvind, Sai Gu, Hani Tabbara, and Spyros Kamnis. "Study of impingement of hollow ZrO2 droplets onto a substrate." Surface and Coatings Technology 220 (April 2013): 164–69. http://dx.doi.org/10.1016/j.surfcoat.2012.08.061.

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Kumar, Arvind, and Sai Gu. "Modelling impingement of hollow metal droplets onto a flat surface." International Journal of Heat and Fluid Flow 37 (October 2012): 189–95. http://dx.doi.org/10.1016/j.ijheatfluidflow.2012.06.004.

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40

Li, Ling, Hong Liang Li, Ying Chun Zhu, Ai Ping Fu, Yong Wan, and Xiu Song Zhao. "Preparation of PS@SiO₂, PS@TiO₂，PS@TiO₂/SiO₂ Core-Shell Composites by a Spray Drying Process and Their Hollow Spheres after Removing PS Cores by Calcinations." Advanced Materials Research 194-196 (February 2011): 389–92. http://dx.doi.org/10.4028/www.scientific.net/amr.194-196.389.

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Polystyrene (PS) spheres encapsulated core-shell composites of SiO2or TiO2nanoparticles were prepared by the spray drying technique and hollow spheres of SiO2or TiO2nanoparticles were then derived by removing the PS cores with calcinations. The PS spheres were dispersed into the SiO2or TiO2colloids, forming a suspension and then the suspensions were sprayed to form micrometer-sized droplets, as the droplets rush through the drying chamber, the PS spheres were encapsulated into the core of SiO2or TiO2particles due to the high temperatures and the instant evaporation, obtaining PS@SiO2, PS@TiO2or PS@SiO2/TiO2core-shell composites. After removing the PS core by calcination at 550°C, SiO2or TiO2hollow spheres were then derived. The influence of drying temperature, the concentration of the SiO2or TiO2particles and the ratio of PS sphere to the particles on the structures and specific surface area of the hollow spheres were studied with scanning electron microscopy (SEM) and nitrogen adsorption-desorption measurements.

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Alshareedah, Ibraheem, Mahdi Muhammad Moosa, Muralikrishna Raju, Davit A. Potoyan, and Priya R. Banerjee. "Phase transition of RNA−protein complexes into ordered hollow condensates." Proceedings of the National Academy of Sciences 117, no. 27 (June 22, 2020): 15650–58. http://dx.doi.org/10.1073/pnas.1922365117.

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Liquid−liquid phase separation of multivalent intrinsically disordered protein−RNA complexes is ubiquitous in both natural and biomimetic systems. So far, isotropic liquid droplets are the most commonly observed topology of RNA−protein condensates in experiments and simulations. Here, by systematically studying the phase behavior of RNA−protein complexes across varied mixture compositions, we report a hollow vesicle-like condensate phase of nucleoprotein assemblies that is distinct from RNA−protein droplets. We show that these vesicular condensates are stable at specific mixture compositions and concentration regimes within the phase diagram and are formed through the phase separation of anisotropic protein−RNA complexes. Similar to membranes composed of amphiphilic lipids, these nucleoprotein−RNA vesicular membranes exhibit local ordering, size-dependent permeability, and selective encapsulation capacity without sacrificing their dynamic formation and dissolution in response to physicochemical stimuli. Our findings suggest that protein−RNA complexes can robustly create lipid-free vesicle-like enclosures by phase separation.

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Li, Da Shu, Xing Qi Qiu, and Zhi Wei Zheng. "A Numerical Study on Hollow Droplets Impact onto a Solid Substrate." Advanced Materials Research 852 (January 2014): 501–5. http://dx.doi.org/10.4028/www.scientific.net/amr.852.501.

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A numerical model using VOF method is developed to describe the phenomenon of a hollow droplet impact on a flat surface including spreading, retardation, recoil and first and secondary break up. The proposed model is verified by literature experiments. Some new hydrodynamic characteristics have been found. The mechanism of central counter jet is explored according to pressure distribution and velocity vectors inside droplet. The relationship between impact features of droplet and deposition parameters is highlighted. In order to investigate the heat transfer rate at the gas-liquid interface, air entrapment and gas cavity are discussed.

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Vysokomornaya, Olga, Nikita Shlegel, and Pavel Strizhak. "Experimentally determining the effects of water droplets collision when mixing aerosol with gas flow at different heating temperatures." Thermal Science 24, no. 3 Part B (2020): 2243–53. http://dx.doi.org/10.2298/tsci180917103v.

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The article presents the results of experimental studies of the collisions characteristics for water droplets in an aerosol at its entry into the air counter flow. The temperature of the latter ranged from 20?C to 500?C. Experiments were also carried out with the flow of combustion products having a temperature of 800- 850?C. The initial dimensions (radii) of the droplets in the aerosol were 50-1000 ?m. Visualization of the droplet motion in the counter flow of air and combustion products required the use of a hollow cylinder made of quartz glass with a height of 1 m and an internal diameter of 0.15 m, a cross-correlation complex and optical methods (particle image velocimetry, particle tracking velocimetry, interferometric particle imaging). The characteristics of the droplet interaction (size, velocity, total surface area of the liquid before and after) were controlled using a high-speed video camera and tracking algorithms in the TEMA AUTOMOTIVE software package. The main modes of drops interaction have been identified: bounce, coagulation, scatter, and breakup. The statistical information database has been obtained to describe the interaction modes using diagrams, taking into account the ratio of the sizes of colliding drops, velocities of their motion, and an angle between trajectories of motion. The influence of gas temperature on the probabilistic criteria of droplet collisions, as well as the integral criterion characterizing the change in the liquid surface area due to the intensification of droplet collisions in the gas medium has been established.

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Xu, Bao Cai, Rong Xia Duan, Jian Jiang Wang, Hong Fei Lou, and Long Zhang. "Ba–Ferrites Hollow Microspheres Prepared by Self–Reactive Flame Spraying Method." Key Engineering Materials 512-515 (June 2012): 249–52. http://dx.doi.org/10.4028/www.scientific.net/kem.512-515.249.

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Barium ferrites hollow microspheres were prepared by self-propagating high-temperature synthesis self-reactive flame spraying method. The droplets enter in the cooling medium and solidified rapidly so that the gas can not escape to remain holes inside the products. The powder samples were used for characterization. The microstructure and crystal structure were studied by SEM, EDS and XRD. The results show that the obtained particles are hollow microspheres. They are spherical or ellipsoidal shapes from nanometer dimension to several micrometers. The phase structure of composite powders is the mixtures of barium ferrite and Fe2O3.

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Skogerboe, R. K., and S. J. Freeland. "Effects of Solution Composition on the Physical Characteristics of Aerosols Produced by Nebulization." Applied Spectroscopy 39, no. 6 (November 1985): 925–30. http://dx.doi.org/10.1366/0003702854249637.

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It has been confirmed that the size distribution of the analyte contained in an aqueous aerosol is affected by the chemical composition of the solution nebulized. The present work has shown that the addition of sodium to copper solutions shifts the aerodynamic and physical size distributions for the copper upward, while the sodium size distributions remain relatively constant. Examination of solid aerosols produced by flash evaporation of aqueous droplets has indicated that the particles tend to be hollow spheres which may encapsulate smaller spheres, as has been observed for particles emitted from combustion sources. The possible significance of droplet evaporation during aerosol transport is examined and judged to be a plausible and at least partial cause of the effects observed.

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Knight, Reyna Madison, Xiaochuan Li, Jeb Stuart Hocter, Bo Zhang, Lingying Zhao, and Heping Zhu. "Optimization of Induction Charging of Water Droplets to Develop an Electrostatic Spray Scrubber Intended for Poultry Particulate Matter Mitigation." Journal of the ASABE 65, no. 4 (2022): 815–24. http://dx.doi.org/10.13031/ja.14913.

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HighlightsInduction charging of water droplets by an ESS showed greatest CMRs using an 80° tapered edge flat spray nozzleCMR of 0.578 mC kg-1 achieved with a water mass flow rate of 0.397 kg min-1 and an applied voltage of -11.6 kVChanges in water conductivity did not significantly affect measured droplet CMRsAbstract. Particulate matter (PM) is a prominent air pollutant in poultry facilities. One promising technology for PM mitigation in poultry facilities is the electrostatic spray scrubber (ESS). However, there is a significant lack of information on the charging characteristics of an ESS to promote efficient droplet charging and poultry PM collection. This study quantified the effects of applied voltage, water mass flow rate, water conductivity, and spray pattern on the charge-to-mass ratio (CMR) of droplets charged by a ring-shape electrode during induction. Voltages from -5 to -14 kV were applied to a 100 mm diameter, cylindrical copper electrode ring to charge droplets sprayed from different nozzles using 80° hollow cone, 80° tapered edge flat, and 110° tapered edge flat spray patterns. It was found that CMRs increased with greater negative voltages up to a point, after which greater negative voltages would decrease the CMR. A similar trend was observed for the effects of water mass flow rate on CMR. Water conductivity showed inconsistent effects on CMR across spray patterns and was deemed a statistically significant but practically insignificant factor. The 80° tapered edge flat spray pattern was found to produce the greatest CMRs. A linear regression model (R2 = 0.865) was developed and optimized to find the ESS configuration resulting in the greatest droplet CMR. The optimal CMR was 0.578 mC kg-1, produced using an 80° tapered edge flat spray nozzle at a water mass flow rate of 0.397 kg min-1, a conductivity of 0.05 S m-1, and an applied voltage of -11.6 kV. Keywords: Droplet charging, Electrostatic scrubber, Electrostatic sprayer, ESS, Induction charging, Spray charging, Spray nozzle.

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Wang, Xue, Linlin Chen, Guanqing Sun, and Ren Liu. "Hollow Microcapsules with Controlled Mechanical Properties Templated from Pickering Emulsion Droplets." Macromolecular Chemistry and Physics 220, no. 4 (January 2, 2019): 1800395. http://dx.doi.org/10.1002/macp.201800395.

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Ghafoor, Abdul, Fraz Ahmad Khan, Farzaneh Khorsandi, Muhammad Azam Khan, Hafiz Muhammad Nauman, and Muhammad Usman Farid. "Development and Evaluation of a Prototype Self-Propelled Crop Sprayer for Agricultural Sustainability in Small Farms." Sustainability 14, no. 15 (July 27, 2022): 9204. http://dx.doi.org/10.3390/su14159204.

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In most Asian countries, farmers have smallholdings ranging from one to two hectares. The tractor-mounted boom sprayers cannot practically be used in small size farms with divided plots and complex terrain. To cope with these issues, a prototype self-propelled crop sprayer was developed, including a 20-hp engine, 300 L liquid tank, and hydraulically-controlled spray boom with eight hollow cone nozzles. The spray symmetry of the hollow cone nozzle was evaluated under four pressures (2.5, 3, 3.5, and 4 bar) in the laboratory. The operating parameters of the sprayer, such as forward speed (4, 6, and 8 km h−1), spray height (40, 55, and 70 cm), and pressure (3, 5, and 7 bar) were optimized by measuring three spray characteristics including droplet density, coverage percentage, and Volume Median Diameter (VMD) in the cotton field. The results revealed that the nozzle spray was symmetrical at 2.5 and 3 bar pressure as the R2 value was higher than 0.96. The field test result showed that in all treatments, treatments T14 (6 km h−1, 55 cm, 5 bar) and T22 (8 km h−1, 55 cm, 3 bar) were suitable for spraying medium-to-low concentration solution (post-emergence herbicides and fungicides) and high concentration solution (insecticides and pre-emergence herbicides), respectively. The spray characteristics at treatments T14 and T22 were 64.7 droplets cm−2, 26.7%, 230 µm, and 39 droplets cm−2, 14.9%, and 219.8 µm respectively. The field efficiency of the sprayer was 61%. The spraying cost per unit area was 55–64% less compared to manual labor cost. In conclusion, a prototype self-propelled crop sprayer is an efficient and environment-friendly technology for small farms. Operating the sprayer at the optimal parameters also saves operational costs and time.

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Bchellaoui, Nizar, Qisheng Xu, Xuming Zhang, El-Eulmi Bendeif, Rachid Bennacer, and Abdel I. El Abed. "Role and Effect of Meso-Structuring Surfactants on Properties and Formation Mechanism of Microfluidic-Enabled Mesoporous Silica Microspheres." Micromachines 14, no. 5 (April 26, 2023): 936. http://dx.doi.org/10.3390/mi14050936.

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We have shown in a previous work that the combination of the emulsion solvent evaporation technique and droplet-based microfluidics allows for the synthesis of well-defined monodisperse mesoporous silica microcapsules (hollow microspheres), whose size, shape and composition may be finely and easily controlled. In this study, we focus on the crucial role played by the popular Pluronic® P123 surfactant, used for controlling the mesoporosity of synthesised silica microparticles. We show in particular, that although both types of initial precursor droplets, prepared with and without P123 meso-structuring agent, namely P123+ and P123− droplets, have a similar diameter (≃30 μm) and a similar TEOS silica precursor concentration (0.34 M), the resulting microparticles exhibit two noticeably different sizes and mass densities. Namely, 10 μm and 0.55 g/cm3 for P123+ microparticles, and 5.2 μm and 1.4 g/cm3 for P123− microparticles. To explain such differences, we used optical and scanning electron microscopies, small-angle X-ray diffraction and BET measurements to analyse structural properties of both types of microparticles and show that in the absence of Pluronic molecules, P123− microdroplets divide during their condensation process, on average, into three smaller droplets before condensing into silica solid microspheres with a smaller size and a higher mass density than those obtained in the presence of P123 surfactant molecules. Based on these results and on condensation kinetics analysis, we also propose an original mechanism for the formation of silica microspheres in the presence and in the absence of the meso-structuring and pore-forming P123 molecules.

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Han, Xiaotian, Hua Zhou, Yifei Zhu, Liangyu Wu, Feng Yao, and Cheng Yu. "Improvement of the Sphericity and the Thickness Uniformity of the Polystyrene (PS) Shell Microsphere during Curing Process." Coatings 9, no. 6 (June 14, 2019): 385. http://dx.doi.org/10.3390/coatings9060385.

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To improve the quality of dispersed polystyrene (PS) compound droplets, a new random rotating curing system is designed. In addition, the qualities of the curing products of the PS compound droplets of this new system are compared with those of the traditional curing system with a constant rotating speed, so as to verify the effectiveness of the new system on the quality improvement of the PS compound droplets. The effect of the liquid level, rotation rate and the density difference on the curing process is also analyzed to reveal the mechanism of the curing process in a rotating flow field. The results indicate that, in the new rotating curing system, the disturbance of the fluid increases the deformation recovery ability of the compound droplets. Furthermore, the vortex with different directions in the external flow fields, make the compound droplets spin in many directions, which improves the spheroidization and concentricity of the compound droplets. Compared with using the traditional rotating curing system, when utilizing the random rotating curing system, the sensitivity of the microspheres’ quality to the density mismatch between the phases is smaller, and the sphericity and the thickness uniformity of the polystyrene (PS) microsphere increase by 10.2% and 4.5%, respectively. In addition, there is an optimal rotation rate for the random rotating curing device, which can optimize the survival rate and quality of the hollow microspheres.

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Journal articles on the topic 'Hollow droplets'

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