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

• Proceedings of the KWS Conference
• /
• 2000.04a
• /
• pp.105-108
• /
• 2000

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

• Clean Technology
• /
• v.21 no.3
• /
• pp.191-199
• /
• 2015

The SO_x emission from the ship diesel engines will do a negative influence to the human health and the environment. To reduce the negative environmental effect of the SO_x emission caused by the high traffic of ship movements, the SECA (SO_x emission control area) has been set on several province around world to carry out the severe emissions control and to meet the emissions control standard. To cut down the SO_x emission from the ships, the wet type scrubber is being used widely. In this work, we prepared a numerical model to simulate the spray type scrubber to study the motion of liquid droplets in the flow of the scrubber. For the analysis, the CFD (computational fluid dynamics) method was adopted. As a special topic of the study, we designed the wave plate type of mist eliminator to check the carry over of the uncontrolled water droplet to the exhaust. Numerical analysis is divided into two stages. At the first stage, the analysis was done on the basic scrubber without the mist eliminator, and then the second stage of analysis was done on the scrubber with the mist eliminator on several condition to check and compare with the basic scrubber. On the condition of the basic scrubber, 42.0% of the distributed water droplets were carried over to the exhaust. But by adding the designed droplet eliminator at the exhaust of the scrubber, only 3.4% of the distributed water droplets supplied to the scrubber was emitted to the atmosphere.

• Journal of computational fluids engineering
• /
• v.21 no.4
• /
• pp.90-95
• /
• 2016

Leidenfrost drops with ellipsoidal shaping can control the bouncing height by adjusting the aspect ratio(AR) of the shape at the moment of impact. In this work, we focus on the effect of the AR and the impact Weber number(We) on the non-axisymmetrical spreading dynamics of the drop, which plays an important role in the control of bouncing. To understand the impact dynamics, the numerical simulation is conducted for the ellipsoidal drop impact upon the perfect non-wetting solid surface by using volume of fluid method, which shows the characteristics of the spreading behavior in each principal axis. As the AR increases, the drop has a high degree of the alignment into one principal axis, which leads to the consequent suppression of bouncing height with shape oscillation. As the We increases, the maximum spreading diameters in the principal axes both increase whereas the contact time on the solid surface rarely depends on the impact velocity at the same AR. The comprehensive understanding of the ellipsoidal drop impact upon non-wetting surface will provide the way to control of drop deposition in applications, such as surface cleaning and spray cooling.

• Journal of Advanced Marine Engineering and Technology
• /
• v.40 no.7
• /
• pp.605-612
• /
• 2016

A numerical analysis was performed on the effect of the design parameters of a bubble jet type microactuator on its liquid flow characteristics. The numerical models included the ink flow from the reservoir, bubble formation and growth, ejection through the nozzle, and dynamics of the refilling process. Because the bubble behavior is a very important parameter for the overall actuator performance, the bubble growth and collapse phenomena in an open pool were simulated in the present study. The drop ejection and refill process were numerically predicted for various geometries of the nozzle, chamber, and restrictor of the bubble jet microactuator. The numerical results from varying the design parameters can help with predicting the performance and optimizing the design of a microactuator.

• Fire Science and Engineering
• /
• v.23 no.1
• /
• pp.48-54
• /
• 2009

The present study has been performed to investigate the effect of statistical number of droplets on the simulation of the sprinkler spray using fire field model. In order to simulate the sprinkler spray characteristics, the present study uses NIST Fire Dynamics Simulator version 5.2. A group of Lagrangian particles with similar droplet characteristics, such as diameter, velocity, temperature and so on, is represented by parcel concept to decrease the total number of droplets tracked in the simulation. The present study introduces a new parameter to represent the ratio between real number of droplets and computational parcels. The dependency of the number of parcels on the fire suppression characteristics and spray patterns is quantitatively examined for different ratio between the real number of droplets and computational parcels.

• Proceedings of the KIEE Conference
• /
• 2007.07a
• /
• pp.1550-1551
• /
• 2007

노즐 직경 $30\;{\mu}$인 MEMS 압전 잉크젯 헤드를 이용하여 Ag 나노 잉크를 PDMS 처리된 PI(Polyimide) 기판 위에 토출하였다. 구동주파수 5 KHz에서 액적부피 1.5 pl, 속도가 약 4.5 m/s인 액적이 토출 되었다. 인쇄된 액적의 크기는 직경 약 $12\;{\mu}m$이었다. 메니스커스의 거동에 맞춘 구동파형의 입력에 의해 새틀라이트 없는 매우 작은 액적을 토출할 수 있었다.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.22 no.8
• /
• pp.1121-1131
• /
• 1998

The present study is numerically investigated for the high-pressure effects on the vaporization process in the convection-dominating flow field. Numerical results agree well with the available experimental data. The fuel droplet vaporization characterization is parametrically studied for the wide range of the operating conditions encountered with the high-pressure combustion process of turbocharged diesel engines.

• Journal of the Korean Society of Visualization
• /
• v.13 no.3
• /
• pp.20-23
• /
• 2015

In this experiment, a heterogeneous droplet consisted of de-ionized water and olive oil was made through two 31G injection needles. The injection flow rate was $50{\mu}{\ell}/min$ and the droplet size was 2 mm. The droplet was impinged onto a sapphire plate which was heated up to $300^{\circ}C$ by a heater. Two high speed cameras were used for visualization, and the frame rate was 20,000 fps. A 150W metal halite lamp was used for illumination. The dropping height was fixed to 20 mm and the corresponding Weber number was 10.6 based on water. Due to different boiling points of two liquids, partial boiling features of heterogeneous droplet was observed. At the Leidenfrost condition, micro explosion phenomenon has occurred.