• Transactions of the Korean Society of Mechanical Engineers
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• v.14 no.4
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• pp.899-906
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• 1990

본 연구에서는 자동차엔진에 대한 응용의 일환으로써 밀폐된 축대칭 연소실내 의 정지하고 있는 공기에 분사에 의해 형성된 분무액적들을 점화원을 이용하여 화염을 생성시키고 그에 따른 화염전파 및 낮은 마하수에서의 유동현상과 이상간의 물리적 관 계를 다차원 유한차분법에 의한 물리적인 지배방정식의 동시해법인 ALE(Arbitrary La- ngrangian Eulerian)방법으로 구성되어 있는 CONCHAS-code를 이용하여 해석하고, 연료 액적의 분사각도, 크기 및 연소실내 기체유동의 각속도의 변화에 의한 분무연소의 과 도적특성을 고찰하고자 한다.

• Korean Chemical Engineering Research
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• v.51 no.6
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• pp.760-765
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• 2013

Lysozyme crystallization was performed by using flow-focusing chip in droplet-based microfluidic system. Water-in-oil droplets were formed in the system and collected on petri-dish and cross type mold. Liquid-liquid reaction of lysozyme and sodium chloride occurred in the droplet and crystals were observed through microscope. Solution pH was varied as 4.8 and 7.2. Crystals of polyhedron and plate-like shape were obtained at pH 4.8, while needle structure crystals formed at pH 7.2. Lysozyme in single droplet for two pHs were crystallized with constant or decreased droplet size. However, crystals at pH 4.8 were only obtained in the droplet of which size was increased by the interaction between droplets. Droplet volume did not change at pH 7.2 and crystals formed in both droplets.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.48 no.9
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• pp.711-716
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• 2020

Injection visualization of heated mixed simulant droplets based on hydrocarbon fuel was performed under supercritical state environment. Mixed simulant consisted of Decane and Methylcyclohexane with different critical pressure and critical temperature. Flows injected into the supercritical state environment created droplet by Rayleigh breakup mechanism, and the Oh number and Re number were determined to confirm the breakup area. The temperature of the mixed simulant varied from Tr=0.49 to Tr=1.34. The flow rate was maintained at 0.7 to 0.8 g/s. Droplet became shorter in breakup length as heated and into a lumped form. Second droplet was formed and when Tr=1.34, the phase was not visible in the supercritical state with local unsteady flow.

• Korean Chemical Engineering Research
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• v.50 no.4
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• pp.733-737
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• 2012

This study reports the microfluidic preparation of monodisperse multiple emulsions using hydrodynamic control. To generate multiple emulsions, we fabricate a microfluidic capillary device based on co-flowing stream without any surface modification of microchannels. Based on the system, we can successfully generate multiple emulsions (W/O/W) using water containing 0.5 wt% Tween 20, n-hexadecane with 5 wt% Span 80, and 10 wt% poly (vinyl alcohol) (PVA) aqueous solution, respectively. Furthermore, we control the number of inner droplets by modulation of flow rate of inner fluid at fixed flow rate of middle and outer fluid. The multiple emulsions having precisely controlled inner droplets' size and number can be applicable for multiple chemical reactions as an isolated microreactor.

• Proceedings of the Korean Society of Laser Processing Conference
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• 2003.05a
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• pp.122-126
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• 2003

• Transactions of the Korean Society of Mechanical Engineers B
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• v.38 no.4
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• pp.329-335
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• 2014

This study aimed to understand the internal flow characteristics of a liquid droplet subject to periodic forced vibration. In order to predict the resonance frequency of a droplet, a high-speed camera and macro lens were used to capture internal flow characteristics of a droplet placed on a vibrating hydrophobic surface. Results showed that the droplet assumed a variety of shapes depending on the resonance mode of free droplet, particularly in modes 2, 4, 6, and 8. In addition, the induced internal vortex flow inside the droplet was also observed in each mode. Typically, the induced flow moved upwards along the axis of symmetry and downwards along the surface of the droplet, that is, from the apex to the contact line in modes 2 and 4, after which it broke into a smaller vortex. On the other hand, the large-scale vortex always remained steady in modes 6 and 8. The speed of the flow in mode 4 was always greater than that in mode 2, but those in modes 6 and 8 were similar.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.6
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• pp.1-7
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• 2017

The atomization of a liquid into multiple droplets has many important industrial applications, including the atomization of fuels in combustion processes and coating of surfaces and particles. Ultrasonic atomizing nozzle has a transducer that receives electrical input in the form of a high frequency signal from a power generator and converts that into mechanical energy at the same frequency. Liquid is atomized into a fine mist spray using high frequency sound vibrations. In coating applications, the unpressurized, low-velocity spray reduces the amount of overspray significantly because the droplets tend to settle on the substrate, rather than bouncing off it. The spray can be controlled and shaped precisely by entraining the slow-moving spray in an ancillary air stream using specialized types of spray-shaping equipment. The desired patterns of spray can be obtained using an air stream. To simulate the water mist behavior of an ultrasonic atomizing nozzle using an air stream, the Lagrangian dispersed phase model was employed using the commercial code FLUENT. The effects of the nozzle contraction shape, water droplet size and the pneumatic pressure drop on the spray characteristics were investigated to obtain the optimal condition for coating applications.

• Journal of ILASS-Korea
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• v.19 no.4
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• pp.211-215
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• 2014

The main purpose of this study is to provide basic information of droplet soot generation of decane fuel. To achieve this, this paper presents the experimental results on the decane droplet combustion conducted under various ambient pressure($P_{amb}$), and oxygen concentration($O_2$) conditions. At the same time, the experimental study was conducted in terms of soot volume fraction($f_v$) and its maximum value. Also, visualization of single fuel droplet was conducted by high resolution CCD camera and ambient pressure($P_{amb}$) and oxygen concentration($O_2$) was changed by control system. It was revealed that higher ambient pressure($P_{amb}$), and oxygen concentration($O_2$) enhanced the soot generation and improved the maximum soot volume fraction( $f_v$).

• 한국가시화정보학회:학술대회논문집
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• 2004.11a
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• pp.94-97
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• 2004

Study of a micro chemical plant consisted with droplet generation, digital sorting and separation was conducted. The droplet generation was quantitatively characterized. The digital sorting brought effective reaction by shortening the droplet size and the pitch of droplet generation simultaneously. To prevent the unfavorable higher order reaction, perfect separation of droplets was visualized.

• Journal of the Korean Society of Visualization
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• v.18 no.2
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• pp.46-50
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• 2020

On-demand droplet generation with tunable droplet volume is fundamental in many droplet microfluidic applications. In this work, we propose an acoustofluidic method to produce water-in-oil droplets with prescribed volume in an on-demand manner. Surface acoustic waves produced from a slanted interdigital transducer are coupled with parallel laminar streams of dispersed and continuous phase fluids. Acoustic radiation force acting on the fluid interface enable generation of droplets in a microfluidic chip. We expect that the proposed acoustofluidic droplet generation method will serve as a promising tool for on-demand droplet generation with on-chip droplet volume control.