• 한국분무공학회지
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• 제6권2호
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• pp.16-21
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• 2001

This paper describes the macroscopic behavior and atomization characteristics of the high-pressure gasoline swirl injector in direct-injection gasoline engine. The global spray behavior of fuel injector was visualized by shadowgraph technique. The atomization characteristics of gasoline spray such as mean diameter and mean velocity of droplets were measured by the phase Doppler particle analyzer system. The macroscopic visualization and experiment of particle measurement on the fuel spray were investigated at 7 and 10 MPa of injection pressure under different spray cone angle. The results of this work show that the geometry of injector was more dominant over the macroscopic characteristics of spray than the fuel injection pressure and injection duration. As for the atomization characteristics, the increase of injection pressure resulted in the decrease of fuel droplet diameter and the atomization characteristics differed as to the spray cone angle. The most droplets had under $25{\mu}m$ diameter and for the large droplets(upper $40{\mu}m$) as the spray grew the atomization presses were very slow. Comparison results between the measured droplet distribution and the droplet distribution functions revealed that the measured droplet distribution is very closed to the Normal distribution function and Nukiyama-Tanasawa's function.

• 해양환경안전학회지
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• 제6권1호
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• pp.47-55
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• 2000

A three-dimensional digital image processing technique is proposed to quantitatively predict the dispersion phenomena of oil droplet onto the surface of the water. This technique is able to get the dispersion rate of an oil droplet three-dimensionally just below the surface of the water over time. The obtained dispersion rate obtained through this technique is informative to the investigation into the relationship among the gravity, surface tensions between oil, water, and air. This technique is based upon the three-dimensional PIV(Particle Imaging Velocimetry) technique and its system mainly consists of a three CCD(Charge Coupled Device) cameras, an image grabber, and a host computer in which an image processing algorithm is adopted for the acquisition of dispersion rate oil an oil droplet.

• 한국가시화정보학회지
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• 제14권2호
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• pp.31-39
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• 2016

We investigate an internal flow pattern of an evaporating droplet where the contact line non-uniformly recedes. By using tomographic Particle Image Velocimetry, we observe a three-dimensional azimuthal vortex pair that is maintained until the droplet is completely dried. The non-uniformly receding contact line motion breaks the flow symmetry. Finally, a simplified scaling model presents that the mechanical stress along the contact line is proportional to the vorticity magnitude, which is validated by the experimental results.

• 대한기계학회논문집B
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• 제20권6호
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• pp.2036-2045
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• 1996

An experimental study has been performed to obtain the effect of relative velocity between droplet and environmental gas on the evaporation of a n-heptane free droplet of 180 $\mu$m in diameter flying in a hot and normal pressure air flow. Measurement of droplet diameter and velocity was conducted in a series of time by an electrically controlled optical system. From the experimental results, an empirical equation associated with the relation between evaporation rate constant and relative velocity was obtained.

• 대한기계학회논문집B
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• 제25권11호
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• pp.1552-1560
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• 2001

This paper presents the experimental results of a study undertaken to develop an electrostatic spray system for a combustion application. The characteristics of the liquid atomization and the droplet dispersion in the electrostatic spray of twin fluids were investigated by the optical measurement techniques. The processes associated with the break-up of charged jets were also observed using the laser sheet visualization. The diameter and velocity of droplets were simultaneously measured using the phase Doppler measurement technique. The electrostatic atomization of the liquid fuel depended primarily on the charging voltage and the flow rate, but the dispersion of droplets depended significantly on the aerodynamic flow. Aerodynamic influences on the liquid atomization decreased with an increase of the charging voltage. Consequently, the liquid atomization and the droplet dispersion could be independently controlled using the electrostatic and aerodynamic mechanisms.

• 한국분무공학회지
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• 제12권2호
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• pp.115-122
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• 2007

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 atomize. 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 Planar Liquid Laser Induced Fluorescence technique. The objectives of this research are get a droplet distributions and drop size measurements of each condition and compare with the other flow effects. As the result, This research has been showned that 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.

• 한국분무공학회지
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• 제16권2호
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• pp.104-109
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• 2011

The present study investigated experimentally the spreading characteristics of a single liquid impinging on the inclined micro-textured aluminum (Al 6061) surfaces manufactured by using a micro computerized numerical control (${\mu}$-CNC) milling machine. The textured surfaces were composed of patterned micro-holes (diameter of $125\;{\mu}m$ and depth of $125\;{\mu}m$). In our experiment, the de-ionized (DI) water droplet of $4.3\;{\mu}l$ was impinged normally on the non-textured and textured surfaces at two different Weber numbers, and the droplet impinged on the inclined surfaces with different angles. A high speed camera was used to capture sequential digital images for measurement of the maximum spreading distance. It was found that for the textured surface, the measured apparent equilibrium contact angle (ECA) increased up to $105.8^{\circ}$, higher than the measured ECA of $87.6^{\circ}$ for the non-textured (bare) surface. In addition, it is conjectured that the spreading distance decreased because of a liquid penetration during droplet spreading through the holes, the increase in hydrophobicity, and viscous dissipation during impact process.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2006년도 제27회 추계학술대회논문집
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• pp.59-63
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• 2006

횡단류 아음속유동장에서 연료의 수직 분사시 나타나는 액적영역의 액적들을 직접사진촬영으로 측정하고 PLLIF 실험을 통하여 얻은 강도 값으로 SMD분포를 측정하였다. 본 연구의 목적은 정상유동에서의 액적들의 크기 및 분포를 관찰하고, 캐비테이션 및 수력튀김 현상에 대한 액적들의 차이를 확인하는 것이다. 실험을 통하여 정상유동의 액적들은 분사차압, 공기의 유속, 침투거리, 인젝터 지름에 대한 하류방향 거리비(x/d)에 의하여 결정되며, 캐비테이션에 의한 난류강도, 유효지름에 따라 차이가 있음을 확인하였다.

• 한국분무공학회지
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• 제12권1호
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• pp.58-64
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• 2007

The spray characteristics of the oxidizer-rich preburner are investigated. This system is generally operated at an oxidizerfuel mixture ratio of 50. The spray quality and mixing performance are very important for safe combustion. To know the spray characteristics of the oxidizer-rich preburner, we have designed various swirl injectors and measured droplet velocity and size by the PDPA system. The flow discharge coefficient of the fuel orifice is $0.12{\sim}0.21$, oxidizer orifice discharge coefficient is $0.16{\sim}0.28$. From the spray visualization, fuel nozzle spray angle is $15^{\circ}{\sim}25^{\circ}$, oxidizer nozzle spray angle is $65^{\circ}{\sim}85^{\circ}$ and combined spray angle is reduced $2^{\circ}{\sim}5^{\circ}$ compared to the oxidizer nozzle only case. From the PDPA measurement, droplet SMD is $175\;{\mu}m$ at 50 mm and $190\;{\mu}m$ at 100 mm of variant 1 combined case. The number concentration measurement revealed the reason of the droplet diameter increasement with distance. That is due to drop coalescence results from collision of drops which is occurred in dense sprays at a long distance from nozzle orifice exit.

• 한국분무공학회지
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• 제7권4호
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• pp.23-31
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• 2002

In this study, the sizes and velocities of droplets in sprays were measured by image processing method from digital images of local region of sprays. The morphological method based on the Euclidean distance transform, Watershed separation, and perimeter image was adopted for the recognition and separation of overlapped particles. The match probability method was used for the particle tracking and pairing. The measurement results show that the present method may be reliable for the analysis of the motion and distribution of droplets produced by spray and atomization devices.