• Journal of ILASS-Korea
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• v.11 no.3
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• pp.131-139
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• 2006

An experimental study was performed to investigate the liquid breakup and atomization characteristics in electrohydrodynamic atomization according to the changing of experimental parameters such as nozzle size, fluid flow, and electrical intensity. An original electrohydrodynamic atomizer equipment was designed and manufactured for the analysis of spray visualization and the exploration of relationship between applied power and the behavior of liquid atomization. The image processing technique by using the back-illumination method was applied to visualize the distilled liquid breakup process and to examine the variation of the droplet size distribution. The results show that the spray modes of electrohydrodynamic atomization are closelyconnected by the strength of the electric stresses at the surface of the liquid film and the kinetic energy of the liquid jet leaving the needle tip.

• Polymer(Korea)
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• v.33 no.4
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• pp.353-357
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• 2009

Spray drying is an effective and stable process, which has been widely used to produce pharmaceutical powders. In the traditional spray drying process, it was not quite easy to control the aggregation and the size of particles. Particularly, the preparation of polymeric particles was relatively hard compared to the preparation of food and pharmaceutical ingredients, typically organic materials of small molecular weights. In this study, modification of a conventional spray dryer was tried to use electrical charge and co-axial nozzles to prepare polymeric particles. Poly(ethylene glycol) and poly (D,L-lactide-co-glycolide) were used as the inner polymeric materials, and lactose as the outer shell materials. The results showed that electrohydrodynamic spray-dried particles had a relatively uniform size and particle morphology, and the aggregation of particles could be suppressed compared to the conventional spray-dried particles. The electrohydrodynamic spray-dried powders consisted of spherical particles of $2{\sim}5{\mu}m$ diameters.

• Journal of the Korean Society of Visualization
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• v.16 no.3
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• pp.47-51
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• 2018

The stable deposition of impinging droplets on non-wetting substrates is of great importance for numerous industrial and scientific applications such as coating techniques, inkjet printing, spray cooling of heated surfaces. In this work, we systematically investigate impinging behaviors of non-Newtonian and viscous droplets ejected by electrohydrodynamic atomization.

• Journal of ILASS-Korea
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• v.14 no.2
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• pp.65-70
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• 2009

An experimental study was performed to explore the atomization characteristics as the drop formation and the liquid breakup of an ethanol fuel using an electrohydrodynamic atomizer. A developed electrohydrodynamic atomizer controlled by a high AC power, a variable frequency, and a liquid feeding was used for the experiments. The test had been considered a disperse atomization processing at $450{\sim}4200V$ applied power, $200{\sim}400\;Hz$ frequency, and $1{\sim}3\;ml/min$ ethanol feeding to achieve an uniformed droplet formation. The goal of the research was to investigate the possibility of the liquid breakup for an ethanol fuel in an electrohydrodynamic atomizer. The results showed that the mean droplet radius decreased as the applied voltage increased or as the applied AC frequency increased. The whipping motion had been grown at the specified voltages due to the applied frequency.

• Journal of ILASS-Korea
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• v.6 no.1
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• pp.44-51
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• 2001

The distributions of the SMD and behavior of 2% $NH_4H_2PO_4$ spray discharged from a fan-spray twin fluid type nozzle are measured and observed. The spray characteristics, according to the variation in the applied voltages, are demonstrated using the PMAS (particle Motion Analysis System) and the CCD camera, respectively. The preliminary experiments are executed to select an optimum condition for solidifying a galvanized coating layer in the uncharged condition before carrying out the main experiments. The liquid and air pressure of $0.07kgf/cm^2\;and\;0.15kgf/cm^2$ can be considered the optimum conditions to use in the main experiment. As the applied voltage increases, the frequent range of relatively large droplets diminishes. Thus, the distributions of drop diameter in the charged spray are more uniform than these in the uncharged condition. This is explained by recognizing that repulsive forces among droplets with the charges of the same sign cause them to be uniform.

• Journal of ILASS-Korea
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• v.8 no.2
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• pp.24-30
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• 2003

An experimental study was performed to investigate the influence factors of drop formation in electrohydrodynamic atomization. The mode of electrohydrodynamic atomization depended on the various factors such as the flow rate of the liquid, the inner diameter of the nozzle, the distance between the nozzle tip and the ground electrode, the shape of the ground electrode. and the applied high voltage. This work was performed to investigate the experimental analysis for the flow pattern visualization of droplets, and the relationship between voltage application and the behavior of liquid atomization. Uniform drops of different sizes can be obtained at the inception of the spindle mode by charging the flow rate and the electric field. The drop size also decreased when the flow rate was raised for the spindle mode. The whipping motion occurred beyond 7kV and before the corona started to take effect.

• Journal of ILASS-Korea
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• v.13 no.2
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• pp.73-78
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• 2008

An experimental study was performed to explore the drop formation and atomization characteristics in electrohydrodynarnic atomization with flow rate, power supply, voltage frequency, and nozzle size. A basic electrohydrodynarnic atomizer equipment was developed for the analysis of spray visualization and tested for the exploration of relationship between several experimental parameters. In results, the varicose wave had been taken place and the small droplets had been generated less than outer diameter of nozzle on the conditions of 25G of nozzle, flow rate of 2 mL/min, and applied frequency of 50kV at AC power over 5kV voltage. The whipping motion had been grown at applied frequency of 400kV and AC power around 2kV voltage

• Journal of ILASS-Korea
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• v.9 no.2
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• pp.41-49
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• 2004

Liquid breakup under the variation of AC frequency has been studied experimentally in the electrohydrodynamic atomization. The effect of parameters such as charging voltage, flow rate, nozzle tip inner diameter and power frequency have been considered. This work was performed to investigate the experimental analysis for the effect of AC frequency on breakup process, the mapping of occurrence of disintegration region, and the relationship between the applied power and the droplet radius. The experimental results show that the increase of applied voltage in a certain frequency band leads to a reduction in the droplet size within the limits from 50Hz to 400Hz. The transition phenomena from dripping mode to spindle mode were observed under the band of sudden fall of droplet radius changing ratio, and the synchronous region were produced within the range of applied voltage from 5kV to 6kV.

• Particle and aerosol research
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• v.8 no.2
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• pp.55-68
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• 2012

Particulate matters (PM) which are collected into a diesel particulate filter (DPF) system have to be periodically removed by thermal oxidation. In this report, we fabricated an electrohydrodynamic-assisted pressure-swirl nozzle to spray diesel droplets finer. Atomization performance of the nozzle was evaluated using both experimental and numerical methods. Two types of nozzle designs, the charge induction type and the charge injection type, were tested. While the former generated diesel droplets of $400\;{\mu}m$ at an applied electric potential over 10 kV, the latter presented the droplets smaller than $23\;{\mu}m$ at an applied electric potential of 8 kV. The numerical simulation results showed that the reduced size of droplets caused higher evaporation of droplets and therefore the increased temperature, which would eventually increase the regeneration performance of the DPF system.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.1322-1327
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• 2004

In the present work, a series of experiments have been performed on electro-hydrodynamic atomization of non-conducting liquid using a charge injection type nozzle. Effects of liquid flow rate, input voltage, and distance between the needle and the ground electrode (nozzle-embedded metal plate) have been examined. For fixed electrode distances, total and spray currents increase with increase of liquid flow rate and input voltage. When the distance between the needle and the ground electrode becomes closer, total, leakage and spray current increase, but the onset voltage for dielectric breakdown decreases. When the electric field strength of the liquid jet exceeds that for the air breakdown, a portion of the electric charges in the liquid jet is dissipated into the ambient air, and the charge density shows a limiting value. Atomization quality can be improved by increasing the flow rate because the higher charge density is achieved with the larger liquid velocity in addition to the enhanced aerodynamic effect.