• 한국분무공학회지
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• 제22권1호
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• pp.13-21
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• 2017

The fog screen is a device projecting the media to the aerosol flow field. As major parameters to generate dense and steady fog screen, shear stress, optical blockage ratio and SMD were obtained result through experiment. The micro droplet was generated by the piezo oscillation element, and the aerosol flow mixed with an air flow was sprayed into the vertical direction from the top of the fog screen through the 280 mm slot. For produce a dense, uniform fog screen, the shear effect, optical blockage ratio and SMD between aerosol and air curtain were measured. The minimum and maximum shear stress conditions were selected and it was confirmed that the optical transmission deviation of the aerosol flow field was small when the aerosol and air curtain flow rates were changed. When the aerosol and air curtain flow power were 18 V (1.51 m/s) and 24 V (2.55 m/s), respectively, under the condition of the minimum shear stress and laminar flow, the optical blockage ratios with the spray length were small, and it produced a most stable and high density uniform fog screen by injecting a constant of $10{\mu}m$ or less.

• 한국추진공학회지
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• 제14권2호
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• pp.1-9
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• 2010

난류 유동장으로 분사되는 액체 제트의 액주 분열과 액적 미립화 현상에 관한 LES를 수행하였다. 기체상태의 공기 유동해석에 Eulerian 해법을 사용하고, 액적 추적을 위하여 Lagrangian 해법을 사용하여 기체-액체간 이상유동(two phase flow) 해석을 수행하였다. 액적 분열 과정 모사에 blob-KH 분열 모델을 적용하여 액주와 액적의 분열이 관찰되었다. 일정한 공기 유동 조건에서 액체 분사 속도 변화를 통한 액체-기체 운동량 플럭스 비의 변화에 따른 액체 제트의 침투깊이를 조사하였으며 실험결과와 유사함을 알 수 있었다. 분사 제트의 분열에 따라 유동장에 존재하는 액적의 분포를 Sauter 평균 입경(SMD)의 분석을 통해 수행하였다.

• 에너지공학
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• 제13권4호
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• pp.235-241
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• 2004

본 연구는 초음파 개질 바이오 디젤유의 점도와 표면장력에 대한 연료의 물리적 특성, 분무 미립화 특성에 관한 심층적이고 체계적인 연구에 중점을 두었다. 이를 규명하기 위하여 초음파 재질 연료와 개질 되지 않은 연료의 상대 비교 분석을 통한 연료특성과 연료분사펌프의 회전수 및 노즐선단 거리변화에 의한 입경측정의 상관성을 정립하였다.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2008년 영문 학술대회
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• pp.486-491
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• 2008

The spray characteristics and drop size measurements have been experimentally studied in liquid jets injected into subsonic crossflow. With water as fuel injection velocity, injection angle and atomizer internal flows were varied to provide of jet operation conditions. The injector internal flow was classified as three modes such as a non-cavitation flow, cavitation, and hydraulic flip flows. Pulsed Shadowgraph Photography measurement was used to determine the spatial distribution of the spray droplet diameter in a subsonic crossflow of air. And this study also obtains the SMD(Sauter Mean Diameters) distribution by using PLLIF(Planar Liquid Laser Induced Fluorescence) technique. The objectives of this research are getting a droplet distribution and drop size measurement of each condition and compare with the other flows effect. As the result, This research have been showed the droplet size were spatially dependent on air-stream velocity, fuel injection velocity, injection angle effects and normalized distance from the injector exit length.(x/d, y/d)There are also different droplet size characteristics between cavitation, hydraulic flip and the non-cavitation flows.

• 한국자동차공학회논문집
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• 제5권4호
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• pp.160-170
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• 1997

The objective of this study is to investigate the atomization characteristics and the performance characteristics of a C. I. engine by using the changes of the injection nozzle type and the ultrasonic-energy-added system. In order to evaluate the effect of ultrasonic energy and of change of injection nozzle type in the performance characte- ristics of a diesel engine, measurements of droplet size of diesel fuel were carried out by using Malvern system. In all types of injection nozzles, SMD of the ultrasonic- energy -added diesel fuel was smaller than that of the conventional diesel fuel and the more injection pressure increased, the more SMD decreased. There was a small increase in SMD with the distance from injection nozzle under all conditions of the injection nozzle types. The minimum SMD was found in the injection nozzle of B type. In the diesel engine test, there were three results about the engine performance. Compared with the injection nozzle of A type, B type had excellent effects in the engine performance. The most excellent effects about the engine performance were obtained in the case of ultrasonic-energy-added diesel fuel. In addition, the torque diagram in the case of ultrasonic-energy-added diesel fuel was more stable and periodical than others.

• 한국분무공학회지
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• 제9권2호
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• pp.24-33
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• 2004

The effect of the working fluid flow conditions and nozzle geometry on the spray performance of a twin-fluid nozzle used in Selective Catalytic Reduction is investigated experimentally. The liquid pressure is varied in the range of 0.3atm to 1.5atm and the air pressure is varied from the 0.5atm to 3.0atm. relative position between liquid nozzle(internal nozzle) and air nozzle(external nozzle) tip changes front 1mm inside the air nozzle to 1mm outside the air nozzle. The orifice diameter of the air nozzle is varied with 5mm. 6mm and 7mm. Spray visualization is realized with CCD-Camera. SMD(Sauter Mean Diameter) and mean particle velocities are measured by PDPA(Phase Doppler Particle Analyzer) under various experimental conditions. The measuring point is 300mm away from the nozzle tip in the downstream spray. The experimental results are that spray angle is depended air flow rate because nozzle diameter, air pressure and nozzle tip relative positions are related air flow rate. SMD is depended air flow rate and water flow rate. Also, SMD is increased when water flow rate is bigger. SMD is decreased when Air flow rate is bigger.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집D
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• pp.909-914
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• 2001

Fluid properties which are most commonly used to evaluate spray atomization characteristics, are important because they affect velocity and size distribution of droplets. The purpose of this study was to incorporate the significant characteristics in atomization process of industrial etching spray and how each of them affects the design of precise pressure-swirl nozzles. The experiment was carried out with different viscosity and density of fluid. The macro characteristics of liquid spray, such as the spray angle and shape were captured by PMAS and the micro characteristics of liquid spray, such as droplet size and velocity were obtained by PDA. The mean velocity and SMD of droplets were measured along axial and radial direction. It was found that the higher viscosity and density resulted in the larger SMD and the lower mean velocity of droplets.

• 한국자동차공학회논문집
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• 제18권4호
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• pp.62-67
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• 2010

The objective of this experimental study is to verify atomization characteristics of emulsified fuel. The emulsified fuel made of adding the ultrasonic energy is analyzed with atomization characteristics and chemicophysics. As water contents within emulsified fuel and needle angle increase, SMD, viscosity and surface tension were analyzed. By measuring the distribution percentage of hydrogen volume by $^1H$-NMR spectrum, the proportion of aromatics and paraffins is analyzed and compared each other. The results of study is as follows. First, as water contents within emulsified fuel and needle angle of nozzle increases, SMD increases. Second, for the distribution percentage of hydrogen volume, the distribution percentage of aromatics is about 10% and the rest portion is paraffins.

• 한국분무공학회지
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• 제3권1호
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• pp.1-9
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• 1998

Two measurement techniques of droplet sizing, an imaging technique(PMAS) and a phase-Doppler measurement technique (PDPA), have been compared using a water spray from a pressurized-type swirl nozzle. The result showed that SMD measured by PDPA was larger than that measured by PMAS by about 40 %. Such discrepancy of SMD could be explained by the fact that the light signal intensity used by PDPA can be biased towards larger particles. On the other hand there could be lower opportunity to capture the images of the large particles with PMAS, since the large particles could be out of sight due to their high speed.

• 한국자동차공학회논문집
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• 제12권6호
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• pp.23-29
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• 2004

This work was conducted to figure out the atomization characteristics of three types of bio-diesel fuels using a common-rail injection system. The process of spray development was visualized by using a spray visualization system composed of a Nd:YAG laser and an ICCD camera, The spray tip penetrations were analyzed based on the frozen images from the spray visualization system. On the other hand, the microscopic atomization characteristics such as the distributions of SMD and axial mean velocity were measured by using a phase Doppler particle analyzer system, It is revealed that the sprays of the bio-diesel fuels have larger SMD than that of diesel fuel mainly due to high viscosity of bio-diesel. Different characteristics of bio-diesel fuels were also measured in spray tip penetrations according to the fuels and mixing ration.