• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2008년도 제31회 추계학술대회논문집
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• pp.175-178
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• 2008

심플렉스 연료노즐의 분무시험을 수행하였다. 가스터빈의 주 연료인 등유를 이용한 연료노즐 분무시험의 경우 폭발의 위험과 유해성으로 인하여 물을 이용하여 시험을 수행하는 경우가 많이 있게 된다. 본 연구에서는 ND:Yag 레이저를 이용한 가시화 시험과 PDPA 시스템을 이용한 입자 크기 측정 시험을 등유와 같은 특성을 가지는 Calibration Fluid Type # 2와 물을 작동유체로 사용하여 수행하였다. 시험결과에서 물의 SMD는 Calibration Fluid Type # 2 보다 5$\sim$15 mm 정도 크게 나타났으며 이는 물의 표면장력이 3배 정도 크기 때문으로 판단된다. 반면에 분무각과 분무형태는 유사하게 나타났다.

• 한국분무공학회지
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• 제25권4호
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• pp.154-161
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• 2020

A single spray plume is the basic unit of the entire spray plume and is an important factor in understanding the spray characteristics. However, since the multi-hole GDI injector has a narrow spray angle, the superposition of the spray plumes occurs severely. Therefore, the spray uniformity and the spray atomization characteristics of a single spray plume were analyzed in this study using a single-hole GDI injector. Five single-hole GDI injectors with different nozzle hole diameters were used in the experiment. The uniformity of the spray was evaluated through the analysis of the spray pattern images. In addition, the atomization characteristics were compared using the diameter distribution of the spray droplets obtained using PDPA. As a result, the larger diameter of the nozzle hole, the less uniformity of the spray, and the injection pressure did not have a significant effect on the spray uniformity. It is judged that the surface roughness of the injector has a greater effect on spray uniformity than the diameter of the nozzle hole. Also, the size of the spray droplets increased sharply when the diameter of the nozzle hole was 230 ㎛.

• 한국분무공학회지
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• 제26권4호
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• pp.189-196
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• 2021

Spray drift of agricultural nozzles has become a big issue because it causes low precision targeting and environmental pollution. In order to reduce the spray drift, study spray characteristics of agricultural nozzles is virtually important. In this study, shadowgraph and Mie-scattering visualization techniques were used to study the macroscopic spray and atomization characteristics of an agricultural nozzle. PDPA was used to measure the atomization characteristics of spray. The injection pressure is set to 1 bar, 3 bar and 5 bar, which covers the working range of the nozzle. For the PDPA experiment, 75 points were measured in an area of 160 mm × 120 mm at 10 mm intervals directly below the nozzle to grasp the overall atomization characteristics of the spray. It was found that the spray width and sheet width showed a linear correlation. As the injection pressure increased, the sheet expansion in the 0-degree direction and the sheet swing in the 90-degree direction jointly promoted the breakup of the sheet. In addition, the area close to the central axis had a large droplet velocity, and since a large droplet velocity promoted atomization of spray, the area close to the central axis had a smaller spray droplet diameter than the left and right regions.

• 한국추진공학회지
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• 제8권3호
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• pp.37-43
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• 2004

증기발생기 슬러지 세정을 위한 고압분사 실험의 분류궤적에 대한 가시화 및 속도분포를 측정함으로써 최적의 노즐형상을 찾기 위하여 플랜져방식의 고압펌프(사용압력 : 200 kg/$\textrm{cm}^2$, 15HP, 11kW. 토출유량 Q : 301/min)를 이용하였다. 가시화를 통하여 정성적인 분포를 비교분석할 수 있었고, 분류의 속도분포등을 통하여 노즐 형상비에 따른 유동의 차이를 2차원 PDPA 광학 계측장비를 사용하여 분석하였다. 고압 분사시 형상비에 관계없이 모든 경우에 있어서 중심축을 따라 모든 궤적들은 거의 유사함을 보였으나, 분류 중심에서 벗어난 외곽영역에서는 많은 차이가 있음을 알 수 있었다 이는 형상 비에 따른 주변 공기와의 마찰 및 분류 유입현상 때문이라 여겨진다.

• 한국정밀공학회지
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• 제23권1호
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• pp.72-79
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• 2006

The objective of this work is to simulate the etching characteristics for the optimization on the etching process of Lead-Frame. The etching characteristics such as etching factor, etching uniformity were investigated under different the actual operating conditions. The correlation between the etching characteristics and the spray ones were analyzed to simulate the etching characteristics in the etching process. To improve the etching characteristics in the etching process, effects of the various operating conditions such as pressure, distance from nozzle tip, pipe pitch, and feed speed should be understood in detail. The spray characteristics obtained by experiment using PDA system were simulated by the Monte-Carlo simulation. The etching process model was coded by Java language. It was found that the spray characteristics were correlated with the etching ones and simulation results generally agreed well with the measured results of etching characteristics in the etching process of Lead-Frame. The optimal operating parameters were successfully found under variable conditions.

• 대한기계학회논문집B
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• 제24권10호
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• pp.1285-1293
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• 2000

In port fuel injection system of SI engines, injected fuel is impinged onto the surface of intake valves and port-wall, and then formed the wall flow under the cold start operation. Wall flows entrained into the cylinder result in the unsteady and nonuniform mixture formation. Therefore, the spray impingement to the wall is considered as having negative influences such as lowering combustion efficiency and causing unburned hydrocarbon emissions. This study investigates the spray characteristics of the wall impinging air-assist spray in suction air flow. A PDPA was used to analyze the flow characteristics under the different conditions such as impingement angle and supplied air. Experimental data concerning the impinging sprays has been obtained in the vicinity of the wall. Measured droplets divided into the pre-impinging droplets which denote as the positive normal velocities and post-impinging droplets that describe as the negative normal velocities for the suction flow. Their velocities, size distributions and SMD are comparatively analyzed before and after the impingement.

• 대한기계학회논문집B
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• 제24권10호
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• pp.1300-1308
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• 2000

The objectives of this study was to investigate the spray characteristics of single spray and twin spray in the overlap region such as mean axial velocity, mean radial velocity, mean droplet size and probability density function of droplet size. A phase doppler anemometer was used as the measurement system for droplet size and velocity. In case of single spray, injection pressure was varied from 0.2MPa to 0.7MPa. Mean axial velocity, mean radial velocity and droplet size were decreased as the distance below nozzle tip was increased. In case of twin spray, the spray characteristics were measured by varying the distance between two nozzles from 127mm to 155mm. In the overlap region, the boundary of the overlap region was determined by obtaining the distribution of mean axial and radial velocity. Droplet size was increased as the distance from nozzle tip was increased. It was found that the distribution of droplet size for twin spray in the overlap region was different to single spray.

• 대한기계학회논문집B
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• 제23권10호
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• pp.1310-1319
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• 1999

High-pressure swirl injectors have usually been employed in Gasoline direct injection engines due to their spray characteristics and the feasibility of their control. Thus the microscopic characteristics of high-pressure swirl spray were investigated by PDA. The correlation between axial and radial velocities and the correlation between droplet size and axial velocity were examined with different axial and radial positions. Two dimensional droplet velocity and its number distribution with size-classified droplets were illustrated. The mean droplet velocity and its SMD were also analyzed at the center of spray, the position having maximum mean axial velocity, and the spray periphery using time dividing method. Finally, the structure of high-pressure swirl spray was presented with the size distribution and velocity profile of droplets.

• 한국분무공학회지
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• 제19권4호
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• pp.216-220
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• 2014

This paper presents effect of nozzle hole number on atomization characteristic of DME fuel spray using three different type of injector having the hole number of 6, 7 and 8. For this study, PDPA(phase Doppler particle analyzer) experiment was performed in terms of $T_{ASOE}$ under various injection pressure. To compare general trend of atomization characteristic, the law data were ensemble averaged based on $T_{eng}$ of 0.2 ms. Results showed that the droplet diameter in terms of SMD(Sauter Mean Diameter) was reduced as increase in injection pressure. Increasing the number of hole lead to reduce in droplet diameter, but no significant reduction in diameter was observed between hole number of 7 and that of 8. In addition, increasing the number of hole resulted in decrease in droplet velocity which is considered as the effect of reduction in spray momentum due to decreasing of fuel quantity per each hole.

• 한국자동차공학회논문집
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• 제13권1호
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• pp.1-8
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• 2005

The spray prepared for direct fuel injection into cylinder is of great importance in a DISI(Direct Injection Spark Ignition) engine. The interaction between air flow and fuel spray was investigated in a steady flow system embodied in a wind tunnel to simulate the variety of in-cylinder flow conditions in the DISI engine. The Mie-scattering images presented the macroscopic view of the liquid spray fields interacting with cross-flow Particle sizes of fuel droplets were measured with phase Doppler anemometer(PDA) system. A faster cross-flow field made SMD larger and $D_10$ smaller. The atomization and evaporation processes with a DISI injector were observed and consequently utilized to construct the database on the spray and fuel-air mixing mechanism as a function of the flow characteristics.