Academic literature on the topic 'Hollow droplets'
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Journal articles on the topic "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.
Dissertations / Theses on the topic "Hollow droplets"
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Sunil, Sanadi Dilip. "Dynamics of Hollow Cone Spray in an Unconfined, Isothermal, Co-Annular Swirling Jet Environment." Thesis, 2015. http://etd.iisc.ernet.in/2005/3866.
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The complex multiphase flow physics of spray-swirl interaction in both reacting and non-reacting environment is of fundamental and applied significance for a wide variety of applications ranging from gas turbine combustors to pharmaceutical drug nebulizers. Understanding the intricate dynamics between this two phase flow field is pivotal for enhancing mixing characteristics, reducing pollutant emissions and increasing the combustion efficiency in next generation combustors. The present work experimentally investigates the near and far-field break-up, dispersion and coalescence characteristics of a hollow cone spray in an unconfined, co¬annular isothermal swirling air jet environment. The experiments were conducted using an axial-flow hollow cone spray nozzle having a 0.5 mm orifice. Nozzle injection pressure (PN = 1 bar) corresponding to a Reynolds number at nozzle exit ReN = 7900 used as the test setting. At this setting, the operating Reynolds number of the co-annular swirling air stream number (Res) was varied in four distinct steps, i.e. Res = 1600, 3200, 4800 and 5600. Swirl was imparted to the co¬axial flow using a guided vane swirler with blade angle of Ф=45° (corresponding geometric swirl number SG = 0.8). Two types of laser diagnostic techniques were utilized: Particle / Droplet imaging analysis (PDIA) and shadowgraph to study the underlying physical mechanisms involved in the primary breakup, dispersion and coalescence dynamics of the spray. Measurements were made in the spray in both axial and radial directions and they indicate that Sauter Mean Diameter (SMD) in radial direction is highly reliant on the intensity of swirl imparted to the spray. The spray is subdivided into two zones as function of swirl in axial and radial direction: (1) near field of the nozzle (ligament regime) where variation in SMD arises predominantly due to primary breakup of liquid films (2) far-field of the nozzle where dispersion and collision induced coalescence of droplets is dominant. Each regime has been analyzed meticulously, by computing probability of primary break-up, probability of coalescence and spatio-temporal distribution of droplets which gives probabilistic estimate of aforementioned governing phenomena. In addition to this, spray global length scale parameters such as spray cone angle, break-up length, wavelength of liquid film has been characterized by varying Res while maintaining constant ReN.
Book chapters on the topic "Hollow droplets"
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Chaitanya Reddy, C., Sarwasva Chowdhary, and S. Rajesh Reddy. "Impact of Droplet Collisions on Hollow Cone Spray in Crossflow." In Lecture Notes in Mechanical Engineering, 271–76. Singapore: Springer Nature Singapore, 2023. http://dx.doi.org/10.1007/978-981-19-7055-9_46.
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Muzychka, Yuri S., and M. Michael Yovanovich. "Further Applications of Spreading Resistance." In Thermal Spreading and Contact Resistance: Fundamentals and Applications, 231–74. ASME, 2023. http://dx.doi.org/10.1115/1.862tsc_ch9.
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In this chapter, we consider several special and unique applications where thermal spreading resistance theory plays a major role in transport phenomena; for example in sliding contacts of tribology applications, mass diffusion with and without chemical reaction, transport involving super-hydrophobic surfaces at low Peclet numbers, electronic microdevices where temperature-dependent thermal conductivity plays a major role, applications involving phase change such as freezing droplets on a surface, and finally thermal spreading in solid or hollow spheres for packed-bed applications. These are all applications where performance is controlled by thermal, mass, or viscous spreading principles. In Chapters 10–12, we will consider thermal contact resistance applications in great detail.
Conference papers on the topic "Hollow droplets"
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Solonenko, O. P., I. P. Gulyaev, and A. V. Smirnov. "Hollow Droplets Micro Explosive Thermal Spraying: Fundamentals." In ITSC2008, edited by B. R. Marple, M. M. Hyland, Y. C. Lau, C. J. Li, R. S. Lima, and G. Montavon. Verlag für Schweißen und verwandte Verfahren DVS-Verlag GmbH, 2008. http://dx.doi.org/10.31399/asm.cp.itsc2008p0229.
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Abstract The peculiarities of plasma treatment of agglomerated YSZ powders as well as mechanically pretreated metal and metal alloy powder with the aim of their spheroidization and subsequent thermal spraying of produced HOSP powders are analyzed. Formation of splats from hollow droplets deserves a special attention for thermal spraying. In this case, immediately prior to particle – substrate collision, we have a droplet that consists of a liquid shell enclosing a gas cavity heated to a temperature close to the particle surface temperature. The paper presented includes the results of computer simulation and model experiments carried out under full control of pre-impact key physical parameters (KPPs): temperature Tp0, velocity up0, external diameter of droplet Dp0, thickness of its shell Δp0 , temperature of substrate Tb0, and its surface state. It was shown that formation of splats from hollow droplets proceeds in a manner more stable compared to the case of “dense” molten particles obtained from fused and crushed compacts, and this provides for a more perfect splat-substrate, splat-splat and coating-substrate interface. Advantages of hollow metal, metal alloy and metal oxide powders over corresponding dense powders for thermal spraying by the example of thermal barrier coatings are discussed. Since the splat formation process involving hollow droplets proceeds, following their high-velocity impact deformation on the base/substrate, in an explosive manner, this type of spraying can be referred as HOSP micro explosive thermal spraying.
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Li, Chunguo, Xinjun Wang, Daijing Cheng, and Bi Sun. "Experimental Study on Effects of Slot Hot Blowing on Secondary Water Droplet Size and Water Film Thickness." In ASME 2008 Power Conference. ASMEDC, 2008. http://dx.doi.org/10.1115/power2008-60015.
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The effects of the slot hot blowing of the hollow stator blades on the size of secondary water droplets and the thickness of the water film were experimentally investigated in this paper. The experiment was carried out on the turbine blade cascades in a wet air tunnel with an inlet air wetness fraction of 7.9%, an outlet air velocity of 170m/s, a slot width of 1.0mm and a slot angle of 45° to blade surface. The Malvern Droplet and Particle Size Analyser was utilized to measure the secondary water droplet size and distribution downstream of the hollow stator blades in the experimental tests. The experimental results show that the maximum diameter and Sauter mean diameter of the secondary water droplets were reduced greatly and the water droplet size distribution became narrower. The larger blowing pressure difference resulted in the smaller secondary water droplets and the narrower water droplet size distributions. In addition, the efficiency of water separation from the hollow stator blade surfaces was higher for slot on the suction side than that of the pressure side case. Another simplified experimental test was also carried out on the flat plate to investigate the effect of slot hot blowing on the thickness of the water film downstream of the slot. The conductivity probes were used to measure the thickness of the water film downstream and upstream of the blowing slot. The results show that the slot hot blowing reduced the thickness of the water film downstream of the slot, which was affected by the blowing pressure difference and temperature difference between the hot blowing air and the main airflow. In conclusion, the slot hot blowing of the hollow stator blades has reduced the size of the secondary water droplets and secondarily has evaporated a little water film on the blade surfaces. Both effects are beneficial to reduce the erosion damage to the rotor blades.
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Takahashi, Minoru, Suizheng Qiu, and Shin-Ichi Kitagawa. "Droplets Behavior of Hollow-Cone Spray in a Non-Condensable Environment." In 10th International Conference on Nuclear Engineering. ASMEDC, 2002. http://dx.doi.org/10.1115/icone10-22171.
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The characteristics of droplets in a water hollow-cone spray from nozzles 1.1 mm and 3.6 mm in diameter in an air environment have been investigated experimentally. The dual phase Doppler anemometry (PDA) system was used to measure the size and two velocity components of individual spherical particles. The liquid spray geometry, including spray breakup length and spray angle were also obtained experimentally. The mechanism and the influence of these parameters on a hollow cone spray flow were described.
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Molino, Jay J., Hirofumi Daiguji, and Fumio Takemura. "Size Control of Hollow Polylactic Acid Microcapsules and Hollow Polyelectrolyte Microcapsules in Bubble Template Method." In ASME/JSME 2011 8th Thermal Engineering Joint Conference. ASMEDC, 2011. http://dx.doi.org/10.1115/ajtec2011-44556.
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Biodegradable hollow poly-lactic acid (PLA) microcapsules and hollow polyelectrolyte microcapsules made of poly-allylamine hydrochloride (PAH) were synthesized by directly adsorbing these polymers to N2 (air) and CO2 microbubbles respectively, using the bubble template method. To manufacture PLA microcapsules, droplets of a solution of PLA in methylene chloride (CH2Cl2) were emulsified in water. Then by solvent diffusion, N2 microbubbles nucleated inside the droplets and PLA adsorbed to the bubble surface to form microcapsules. Likewise, for PAH microcapsules, when an aqueous solution of Na2CO3 including PAH is titrated with HCl, within a specific range 7.5 < pH < 9.0, colloidal PAH particles are formed and then adsorbs to the nucleated CO2 microbubbles. This yields to hollow PAH microcapsules. If the solution pH is outside this range, colloidal particles can no longer exist, thus no microcapsules can be synthesized. This document mainly focuses on size control of these two types of microcapsules.
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Das, Mithun, Souvick Chatterjee, Swarnendu Sen, and Achintya Mukhopadhyay. "Experimental Investigation of a Hollow Cone Spray Using Laser Diagnostics." In ASME 2013 Gas Turbine India Conference. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/gtindia2013-3709.
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Atomization of fuel is a key integral part for efficient combustion in gas turbines. This demands a thorough investigation of the spray characteristics using innovative and useful spray diagnostics techniques. In this work, an experimental study is carried out on commercial hollow cone nozzle (Lechler) using laser diagnostics techniques. A hollow cone spray is useful in many applications because of its ability to produce fine droplets. But apart from the droplet diameter, the velocity field in the spray is also an important parameter to monitor and has been addressed in this work. Kerosene is used as the test fuel which is recycled using a plunger pump providing a variation in the injection pressure from 100psi to 300psi. An innovative diagnostic technique used in this study is through illumination of the spray with a continuous laser sheet and capturing the same with a high speed camera. A ray of laser beam is converted to a planer sheet using a lens combination which is used to illuminate a cross section of the hollow cone spray. This provides a continuous planar light source which allows capturing high speed images at 285 fps. The high speed images, thus obtained are processed to understand the non-linearity associated with disintegration of the spray into fine droplets. The images are shown to follow a fractal representation and the fractal dimension is found to increase with rise in injection pressure. Also, using PDPA, the droplet diameter distribution is calculated at different spatial and radial locations at wide range of pressure.
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Solonenko, O. P., A. A. Mikhalchenko, and E. V. Kartaev. "Splat Formation Under YSZ Hollow Droplet Impact Onto Substrate." In ITSC2005, edited by E. Lugscheider. Verlag für Schweißen und verwandte Verfahren DVS-Verlag GmbH, 2005. http://dx.doi.org/10.31399/asm.cp.itsc2005p1410.
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Abstract Formation of splats from hollow YSZ droplets deserves a special attention for thermal spraying. In this case, immediately prior to particle – substrate collision, we have a drop that consists of a liquid shell enclosing a gas cavity heated to a temperature close to the melt temperature. As the drop impinges onto the substrate, it suffers considerable deformation resulting in a rise of the gas pressure and in a decrease of gas temperature. The paper presented includes the results of the model experiments carried out under full control of the key physical parameters (KPPs) - temperature, velocity and size of droplet, and temperature of polished substrate, in which the starting powder was a specially prepared powder consisting exclusively of the hollow spherical YSZ particles. The main goal of the paper is to discuss and study the possible splat formation scenarios under above-mentioned conditions.
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Wei Lu, Min Chen, and Limin Wu. "Facile preparation method of nanocrystal CdS hollow spheres with miniemulsion droplets as templates." In 2008 2nd IEEE International Nanoelectronics Conference. IEEE, 2008. http://dx.doi.org/10.1109/inec.2008.4585430.
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Palmer, Johannes, Manuel Reddemann, Valeri Kirsch, and Reinhold Kneer. "Development steps of 2-color laser-induced fluorescence with MDR-enhanced energy transfer for instantaneous planar temperature measurement of micro-droplets and sprays." In ILASS2017 - 28th European Conference on Liquid Atomization and Spray Systems. Valencia: Universitat Politècnica València, 2017. http://dx.doi.org/10.4995/ilass2017.2017.4591.
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A new method for instantaneous measurement of temperature, size and velocity of micro-droplets has been developed.The method is based on the well-known 2-color laser-induced fluorescence (2cLIF) technique, but usesa pulsed laser for 2-dimensional imaging without motion blur and an adjusted dye mixture for suppression of LIFMDRsby utilizing the MDR-enhanced energy transfer effect. This work presents the development steps that arenecessary to verify feasibility of pulsed 2D-2cLIF-EET for micro droplet and hollow-cone spray applications.DOI: http://dx.doi.org/10.4995/ILASS2017.2017.4591
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Glahn, A., M. F. Blair, K. L. Allard, S. Busam, O. Schäfer, and S. Wittig. "Disintegration of Oil Films Emerging From Radial Holes in a Rotating Cylinder." In ASME Turbo Expo 2001: Power for Land, Sea, and Air. American Society of Mechanical Engineers, 2001. http://dx.doi.org/10.1115/2001-gt-0202.
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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 aero-engine 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 data-base 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 et al, 2000), the near-term objectives of the study are (i) to determine droplet sizes under relevant aero-engine 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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Molino, Jay J., Hirofumi Daiguji, and Fumio Takemura. "On the Kinetics of Formation of Hollow Poly(Lactic Acid) Microcapsules Fabricated From Microbubble Templates." In ASME 2012 10th International Conference on Nanochannels, Microchannels, and Minichannels collocated with the ASME 2012 Heat Transfer Summer Conference and the ASME 2012 Fluids Engineering Division Summer Meeting. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/icnmm2012-73257.
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Biodegradable hollow poly-lactic acid (PLA) microcapsules were synthesized by directly adsorbing the polymer to N2 (air) microbubbles using the bubble template method. In this method microbubbles nucleate inside droplets, made of a solution of PLA in dichloromethane, as a result of solvent diffusion into a continuous phase of either water or a PVA aqueous solution. Subsequently PLA adsorbs to the microbubble surface, covers it and then the microbubble covered with PLA is spontaneously released from the drople’s interior yielding to hollow PLA microcapsules. For special fabrication conditions, it was found that the final capsules were uniform in size. It was found that the high uniformity is directly correlated to the type of release. This was classified into either single or multiple bubble release. When the predominant type of release is single bubble release, the resultant microcapsules were uniform. In this study we also aim to elucidate the conditions required to attain single bubble release. It is believed that this type of release is attained when the energy barrier at the liquid-liquid interface is lowered, thus microcapsules can be smoothly released. From experiments, it was understood that the use of PVA, a low molecular weight PLA and an initially low PLA concentration is the requirement in order to attain single bubble release. Furthermore, based on rheological and the surface tension measurements at the liquid-liquid interface and inner flow circulation inside the droplet we proposed two plausible mechanisms for single bubble release: (a) mechanism based on the repulsive force between two adjacent microbubbles and (b) mechanism based on the imbalance of interfacial tensions around a bubble. SEM images revealed that microcapsules obtained from ‘multiple bubble’ type can display a non-spherical cores. In addition, these capsules can have briged shells or bridged cores (share cores). Microcapsule bridging can happen inside the droplet (when cores are shared) or outside (when only the shell is bridged). Increasing the initial concentration of PLA or using a PLA of high molecular weight yields to this phenomenon. The zeta potential of these capsules at pH = 7.0 was above 20mV, and thus the colloidal suspension of microcapsules in water was stable.