• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 추계학술대회
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• pp.1629-1633
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• 2004

Liquid is commonly introduced as transversal jets in venturi scrubber which is one of the gas cleaning equipments. The jet dynamics such as penetration and breakup is of fundamental importance to the dust-collection efficiency. We have developed a model that can numerically simulate the breakup of the liquid jet in crossflow. This simulation consists of models on liquid column, jet surface breakup, column fracture and secondary droplet breakup. These models have been embedded in the KIVA3-V code. We have calculated such parameters as the jet penetration, jet trajectory, droplet size, velocity field and the volume flux distribution. The results are compared with the experimental data in this paper.

• 오토저널
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• 제9권4호
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• pp.41-49
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• 1987

It is an experimental study to improve the characteristics of combustion and exhaust emission gas in the gasoline engine. These characteristics are influenced by the fuel droplet size. To improve these characteristics, we make the ultrasonic atomization apparatus, and compare with the commercial carburetor. The results obtained are as follows: 1. Maximum atomization quantity is obtained by the vibrator of resonancy frequency 1.65MHz in the ultrasonic atomization apparatus. 2. With ultrasonic atomization apparatus, more than 99% of atomization rate can be obtained regardless of intake air temperature, velocity, and air-fuel ratio. 3. Atomization rate of the commercial carburetor increases with the air-fuel ratio and intake air temperature. 4. Difference of atomization rate between the ultrasonic atomization apparatus and the commercial carburetor increases with decreasing air-fuel ratio. 5. Droplet size is about 1-5.mu.m at the ultrasonic atomization apparatus, and 80-150.mu.m at the commercial carburetor, which indicates the ultrasonic atomization apparatus is excellent in atomization.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2009년도 제33회 추계학술대회논문집
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• pp.202-206
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• 2009

고속회전 연료분사시스템의 분무특성을 연구하였다. 분무특성에 영향을 주는 직렬식 분무오리피스의 직경을 각각 1mm, 2mm, 3mm, 4mm, 5mm와 분무오리피스 수를 3개, 6개, 12개로 변화시켜가며 분무특성 연구를 수행하였다. PDPA 측정 시스템을 이용하여 분무입자의 크기와 속도, 분무분포 등을 측정하였고, 고속카메라를 이용하여 분무가시화를 수행하였다. 실험결과, 분무오리피스로부터 분출된 단일 액주의 길이는 회전속도에 의해 제어되며, 분무입자의 크기(SMD)는 분무오리피스의 직경과 수가 증가함에 따라 작아지는 경향을 보였다. 결국 분무입자의 크기를 제어하는 기본 메커니즘은 분무 오리피스내의 액막의 두께에 의해 결정됨을 알 수 있었다.

• 한국가시화정보학회지
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• 제8권4호
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• pp.60-65
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• 2010

A focus is given to the breakup behavior of spray droplets issuing from a nonimpinging-type injector. The analysis has been carried out experimentally by means of the dual-mode phase Doppler anemometry (DPDA). Spray characteristic parameters in terms of axial velocity, mean diameter, velocity fluctuation, and span (width of the size distribution) of droplets are measured down the geometric axis of a nozzle orifice and on the plane normal to the spray stream with the injection pressure variations. As the injection pressure increases, the velocity and its fluctuation become higher, whereas the droplet sizes get smaller. It is also shown that the magnitudes of those parameters are smoothed out by dispersion when the droplets move downstream as well as outwardly. The atomization process is significantly influenced by the injection pressure rather than the traveling distance in the experimental condition presented.

• 한국자동차공학회논문집
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• 제13권6호
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• pp.7-12
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• 2005

In order to analyze the microscopic spray characteristics of free spray in ultra high pressure region, the droplets size and velocity of free spray injected under atmosphere condition were measured by PDPA. As injection pressure became ultra high pressure, the droplets size was decreased continuously due to the increase of mutual reaction between droplets and air. But the decreasing rate became moderate. The velocity was increased until 250 MPa, and then decreased over that of injection pressure. It was seemed that the droplet size was similar in range of $280\~350\;MPa$, but increased in 414 MPa, even though injection pressure was increased. The microscopic spray characteristics of free spray got worse in 414 MPa.

• 대한기계학회논문집B
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• 제35권4호
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• pp.353-360
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• 2011

액적 충돌은 물방울 형성 및 분무 유동 등의 현상을 예측하는데 있어 매우 중요하다. 이러한 액적 충돌은 액적 속도, 충돌 파라미터, 액적 크기비에 영향을 받아, 충돌 후 거동 특성이 결정된다. 충돌 후 액적은 반사, 합일, 스트레칭 분리, 리플렉시브 분리와 같은 거동 특성을 갖는다. 본 연구에서는 레벨셋 방법을 사용하여 충돌 후 액적 거동 특성에 대한 이상유동 해석을 수행하였다. 정면충돌 현상에 대한 2차원 축대칭 해석으로부터 합일 및 리플렉시브 분리 현상을, 비중심충돌 현상에 대한 3차원 해석으로부터 합일, 리플렉시브 분리, 스트레칭 분리 현상을 예측할 수 있었다. 이러한 해석 결과는 기존 실험 및 이론적 연구 결과와 일치하는 결과를 보였다. 또한, 초기 액적의 부피비에 대한 수송 방정식을 사용하여 충돌하는 두 액적의 성분을 추적하였다. 이로부터 크기가 다른 두 액적의 정면충돌에 대한 액적 성분 추적을 통해 액적 거동 및 액적 성분에 대해 분석하였다.

• 한국분무공학회지
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• 제25권3호
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• pp.103-110
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• 2020

In this study, the behavior of water droplet impacting on a thin horizontal wire was visualized by time-delay photography. The impact behavior modes, critical capture speed and trapped mass were analyzed by changing the droplet size, velocity, wire diameter and eccentricity ratio. As the Weber number increased, the hanging, merging, and splitting modes appeared sequentially for the case of central impact, and the hanging and non-splitting modes appeared for the case of off-center impact. The boundary We number of each mode was affected by the diameter ratio. The critical capture speed was affected much by the degree of eccentricity. For all diameter ratios, it was higher for the case of central impact than for off-center impact. The trapped mass was larger for the case of central impact than for off-center impact and it increased with the smaller We number and the larger diameter ratio.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2006년 제4회 한국유체공학학술대회 논문집
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• pp.505-508
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• 2006

An electrostatic ink jet head can be used for manufacturing processes of large display systems and printed circuit boards (PCB) as well as inkjet printers because an electrostatic field provides an external force which can be manipulated to control sizes of droplets. The existing printing methods such as thermal bubble and piezo inkjet heads have shown difficulties to control the ejection of the droplets for printing applications. Thus, the new inkjet head using the electrostatic force has been proposed in this study. In order to prove the theory of the developed electrostatic ink jet head, the applicable and basic theory has been studied using distilled water and water with sodium dodecyl surfate (SDS). Also, a numerical analysis has been performed to calculate the intensity of the electrostatic field using the Maxwell's equation. Furthermore, experiments have been carried out using a downward glass capillary with outside diameter of $500{\mu}m$. The gravity, surface tension, and electrostatic force have been analyzed with high voltages of 0 to 5kV. It has been observed that the droplet size decreases and the frequency of the droplet formation and the velocity of the droplet ejection increase with increasing the intensity of the electrostatic field. The results of the experiments have shown good agreement with those of numerical analysis.

• 한국분무공학회지
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• 제8권4호
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• pp.39-45
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• 2003

The Objective of this study is to investigate the effect of internal swiller angle and swirl chamber aspect ratio of nozzle on spray characteristics for application of spray system in micro fabrication process. The macro-spray characterictics such as the spray angle and breakup process were obtained by photographs illustrating atomization. The micro-spray characteristics such as droplet size and axial velocity were measured by using PDA with swirler angle and swirl chamber aspect ratio. The swiller angles were $13.5^{\circ},\;27^{\circ},\;and\;40.5^{\circ}$. The swirl chamber aspect ratios were 1.2, 1.6, and 2.0. It was found that the smaller swirl chamber aspect ratio was, the larger axial velocity and drop size were.

• 한국화재소방학회논문지
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• 제9권2호
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• pp.10-16
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• 1995

This study discribes characteristics of water spray for extinguishment of gasoline fire. Experiments are carried out for the gasoline pool fire nth the atomizing nozzles. Droplet size, spray pressure, amount of water which reaches the flame base and velocity of water spray are measured to find extinguishment conditions. Air entrainment due to the water spray and extinguishing process of gasoline fire by water spray are visualized. Boundary conditions of water spray for extinguishment of gasoline pool fire is quantitatively shown. As the result of experiments, it is found that the velocity of entrainment air and sprayed water are almost same and the water droplets size having small diameter under 40$\mu\textrm{m}$ can not extinguish the fire because too small droplets does not reach the fuel surface.