• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.8
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• pp.4809-4814
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• 2014

The aim of the present study was to estimate the prediction performance of a FDS (Fire Dynamic Simulator) to simulate the fire behaviors and suppression characteristics by operating a water-mist. Rosin-Rammler/log-normal distribution function was used to determine the initial droplet distribution of water-mist and the effects of its model constant were considered. In addition, the simulation models were validated by a comparison of the predicted fire suppression characteristics with water-mist injection pressures to the previous experiments, and the thermal flow behaviors and gaseous concentration variations were analyzed. The results showed that water-mists with the same mean diameter were affected by the characteristics of the droplet size distribution, which have different size and velocity distributions at the downstream location. The fire simulations conducted in this study determine the initial droplet size distribution tuned to the base of the spray characteristics measured by previous experiments. The simulation results showed good agreement with the previous measurements for temperature variations and fire suppression characteristics. In addition, it was confirmed that the FDS simulation with a water-mist operation supplies useful details on estimations of the thermal flow fields and gaseous concentration under water mist operation conditions.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.31 no.5
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• pp.72-79
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• 2003

Spray characteristics were investigated by impinging F-O-O-F type injector with varying the impingement angle through 15, 20 and 30 degree and the mixture ratio(O/F ratio) from 1.5 to 3.0. Experimental results show that the correlation between dispersion and impingement angle is not influenced of the mixture ratio variation, but which has influence on number density, and there is a linear correlation between dispersion and impingement angle. Velocity distribution, standard deviation and SMD of droplets are decreased as the impingement angle increases. Also, it was confirmed that the distribution of droplet size are in accordance with Rosin-Rammler and Upper-limit distribution.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.40 no.10
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• pp.862-871
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• 2012

The numerical simulations on 500-N class rocket engine using 96% hydrogen peroxide and kerosene have been conducted, considering atomization, evaporation, mixing and combustion of its propellants. The grid containing 1/6 part of combustion chamber has been generated and it is assumed that 3 kinds of liquid-phase propellants (kerosene, hydrogen peroxide and water) were injected as hollow cone spray pattern, using Rosin-Rammler function for distribution of droplet diameter. For the calculation of combustion the eddy-dissipation model was applied. Owing to small size of combustion chamber and large specific heat / latent heat of hydrogen peroxide and water the propulsion characteristics were highly influenced by the size of droplet particles, and in this analysis the engine with droplet particles of 30 micron in average has shown the best propulsion performance.

• Applied Chemistry for Engineering
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• v.26 no.5
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• pp.549-556
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• 2015

Anti-insect repellent silica sol from mixture with silica and anti-insect repellent solution extracted from medicinal herbs was prepared. The micron size porous sphere powder with anti-insect repellent solution was prepared by the spray drying method. The characteristic of anti-insect repellent powder using spray drying method was analyzed by FE-SEM, PSA, TGA with the concentration of anti-insect repellent sol (anti-insect repellent solution and silica) and conditions of spray drier. The average particle size of 4, 7 wt% and 10 wt% of anti-insect repellent sol concentration were 8.3, $9.5{\mu}m$ and $11.7{\mu}m$, respectively. The particle size is increasing with high concentration of anti-insect repellent sol. Other hands, particle size as the temperature of inlet nozzle and velocity of sol injection were nearly same at high velocity of gas injection. Also, Anti-insect repellent impregnation in porous sphere powder were confirmed by TGA methode and its thermal property was stable up to $200^{\circ}C$. We expect that anti-insect repellent powder is applied for plastic compound and process of film manufacture.

• Journal of the Korean Society of Propulsion Engineers
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• v.12 no.1
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• pp.29-36
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• 2008

Spray characteristics for APU gas turbine engine are investigated. In the test, four flight conditions such as sea level idle, sea level max power, 20,000 feet idle, 20,000 feet max power are used as spray experimental conditions. Spray visualization was performed by using ND-YAG laser bean PDPA(Phase Doppler Particle Analyzer) was used for measuring the particle diameter and velocity from 20 mm to 100 mm from discharge orifice. From the test result, SMD is $90{\sim}95\;{\mu}m$ 맛 20,000 ft idle condition and SMD is $60{\sim}75\;{\mu}m$ at sea level idle condition. Also SMD is $55{\sim}65\;{\mu}m$ at 20,000 ft max power condition and SMD is $30{\sim}70\;{\mu}m$ at sea level max power condition. In the case of 20,000 ft idle condition, combustion instability could be occurred due to the higher drop diameter. Therefore it is necessary to decrease the droplet diameter in the high altitude condition.

• Journal of ILASS-Korea
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• v.11 no.1
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• pp.39-47
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• 2006

In-cylinder flows in a motored 3.5L four-valve SI engine were investigated quantitatively using three-component LDV system, to determine how engine configuration affects the flow field. The purpose of this work was to develop quantitative methods which correlate in-cylinder flows to engine performance. For this study, two distinct intake/piston arrangements were used to examine the flow characteristics. Quantification of the flow field was done by calculating two major parameters which are believed to characterize adequately in-cylinder motion. These quantities were turbulent kinetic energy(TKE) and tumble ratio in each plane at each crank angle. The results showed that in-cylinder flow pattern is dominated by the intake effects and two counter rotating vortices, developed during the intake stroke, produced relatively low tumble ratio. Therefore, the applicability of these quantities should be carefully considered when evaluating characteristics resulting from the complex in-cylinder flow motions.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.28 no.11
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• pp.1459-1466
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• 2004

The purpose of this study is to investigate the effect of swirler angle and the aspect ratio of swirl chamber of nozzle on the characteristics of single and twin spray. The characteristics of sprays have been investigated by measuring the spray angle, droplet size and velocity. Visualization of spray was conducted to obtain the spray angle and breakup process. The spray characteristics such as droplet size and velocity were measured by Phase Doppler Anemometry(PDA). It was found that the spray angle was increased with increasing the swirler angle. For both sprays, the axial velocity and SMD were decreased with increasing the swirler angle. It was also shown that the axial velocity and SMD were decreased with increasing the aspect ratio of swirl chamber, but for the twin spray, the axial velocity and SMD were not influenced significantly by the changing the aspect ratio of swirl chamber. The effect of swirler angle on the spray characteristics was greater than the aspect ratio of swirl chamber for single spray. The nozzle pitch was one of the important factors affecting the spray characteristics of twin spray.

• Transactions of the Korean Society of Automotive Engineers
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• v.15 no.5
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• pp.30-37
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• 2007

Dimethyl Ether(DME) is an alternative fuel for diesel engine, it is renewable and offers potential reductions in emissions. This work was conducted to figure out the macroscopic behavior and the atomization characteristics of DME using a common-rail injection system. The macroscopic behavior was visualized with the spray visualization system composed of a Nd;YAG laser and an ICCD camera. The atomization characteristics were investigated in terms of axial mean velocity, Sauter mean diameter(SMD) and droplet distributions obtained from a phase Doppler particle analyzer(PDPA) system. In this study, it was revealed that the macroscopic behavior and the atomization characteristics of DME are similar compared with commercial diesel fuel. However, DME fuel has a shorter spray tip penetration and a small SMD due to the effect of evaporation characteristics.

• Journal of the KSME
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• v.23 no.4
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• pp.288-294
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• 1983

고속기류에 의한 수표면의 유통은 호수나 강에서 흔히 볼 수 있는 물리적인 현상으로서 기류의 속도가 증가함에 따라서 수표면에서 액적이 발생하게 되는 이른바 액체미립화 현상(atomization )이 일어나게 된다. 이러한 액체의 미립화는 내연기관에서의 분무연소에서 부터 가정에서 습도를 유지하는 가습기 및 살충제분무기에 이르기까지 그 운용도가 매우 광범위하며 최근에 이르러 액체미립화가 유체역학의 한 부분을 차지하는 단계에까지 이르러 매년 각국에서 미립화에 대한 심포지움이 개최되고 있으며 연구실적면에서는 미국보다도 오히려 가까운 일본에서 미립화에 대한 연구가 더 활발히 진행되고 있는 반면 아직 우리나라에서는 이렇다할 연구가 없으며 미립 화에 관한 논문도 불과 한두 편에 이르는 실정이다. 이러한 중요한 물리적인 현상에 대해 좀더 자세한 이해를 위해서는 액체와 기체의 상호접촉면에서의 정량적인 특성에 대한 연구가 필요하며 이러한 정량적 인자에는 (1) 액막의 평균두께 (2) 액막내의 속도분포, (3) 액막표면의 파고, 파장의 파면구조, (4)기체중의 속도분포 등이 있다.

• Fire Science and Engineering
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• v.30 no.6
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• pp.111-117
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• 2016

The present study examined the free surface flow of a liquid sheet near a sprinkler head using a Computational Fluid Dynamics (CFD) model and considered the feasibility of the empirical model for predicting the initial spray characteristics of the sprinkler head through a comparison of the CFD results. The CFD calculation for a simplified sprinkler geometry considering the nozzle and deflector were performed using the commercially available CFD package, CFX 14.0 with the standard $k-{\varepsilon}$ turbulence model and theVolume of Fluid (VOF) method. The predicted velocity of the empirical model at the edge of deflector were in good agreement with that of the CFD model for the flat plate region but there was a certain discrepancy between the two models for the complex geometry region. The mean droplet diameter predicted by the empirical model differed significantly from the measured value of the real sprinkler head. On the other hand, the empirical model can be used to understand the mechanism of droplet formation near the sprinkler head and predict the initial spray characteristics for cases without experimental data.