• 한국자동차공학회논문집
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• 제2권5호
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• pp.11-22
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• 1994

The pupose of this study is to measure droplet size and velocity simultaneously for a transient diesel fuel spray in a quiescent chamber at atmospheric temperature and pressure. Generally, diesel combustion phenomena is mainly governed by characteristics of injection system and fuel spray. Therefore we need to clarify these characteristics for developing more economical diesel systems. In this study, correlation between droplet size and velocity was measured at downstream distance from nozzle. Governing parameters are pump speed and fuel quantity for the detailed nature in this transient diesel fuel spray. It is observed effect to the droplet size and velocity distribution. Velocity(peak, mean, rms), number density and droplet size were investigated simulaneously using PDA in the spray. Various results are presented to illustrate the effects of operation factors and correlation between the droplet diameter and velocity.

• 한국재료학회지
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• 제16권10호
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• pp.633-638
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• 2006

Silica powders with spherical shape and narrow size distribution were prepared by large-scale ultrasonic spray pyrolysis applying the droplet classification apparatus. On the other hand, silica powders prepared by large-scale ultrasonic spray pyrolysis without droplet classification apparatus had broad size distribution. Droplet classification apparatus used in this paper applied the principles of cyclone and dispersion plate with small holes. The droplets formed from the ultrasonic spray generator applying the droplet classification apparatus had narrow size distribution. The droplets with fine and large sizes were eliminated by droplet classification apparatus. The optimum flow rate of the carrier gas and diameter of the hole of the dispersion plate were studied to reduce the size distribution of the silica powders prepared by large-scale ultrasonic spray pyrolysis. The size distribution of the silica powders prepared by large-scale ultrasonic spray pyrolysis at the optimum preparation conditions was 0.76.

• 융복합기술연구소 논문집
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• 제3권2호
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• pp.51-56
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• 2013

This paper describes the atomization characteristics, as well as the velocity and size distribution, of DME spray based on common-rail injection system. To analyze the possibility of using DME fuel as an alternative fuel of diesel, spray atomization characteristics were investigated. For this investigation, two-dimensional phase Doppler analyzer system was used to obtain droplet size and velocity distribution simultaneously. Velocity and droplet size measurements were performed at various injection pressures. Results showed that increasing pressure from 25MPa to 50MPa leads to higher spray droplet velocities and smaller droplet diameter but injection pressure above 40MPa, no signifiant reduction was observed. With the droplet velocity and SMD comparison between diesel and DME fuel, it can be observed that DME has smaller SMD and droplet velocity due to its low surface tension.

• 한국자동차공학회논문집
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• 제7권8호
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• pp.1-6
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• 1999

An experimental study was carried out to investigate the global spray behavior and spray characteristics of high-pressure fuel injector in the direct-injection goasoline enginet. The atomization characteristics of fuel spary such as mean droplet size, mean velocity , and velocity distribution were measured by the phase Doppler particle analyzer. The spray tip penetration and spray width were investigated by the result fo visualizaiton experiment. The quantitiative spary characteristics of injector spray were measured under various sparay conditions and ambient pressures. The results of experiment show that the increase in ambient pressure have influence on the spray tip penetration and spray development process. Also, the influence of injection pressure and measuring location on the mean velocity and droplet size distribution were discussed.

• 대한기계학회논문집
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• 제18권3호
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• pp.635-644
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• 1994

This study investigated mainly on the flow characteristics of a droplet in the cross region of twin spray. The velocities of the droplet were measured along the axial and radial direction, and the flow characteristics of the droplet were statistically analyzed. For the statistical analysis, the probability density of the turbulent components has been studied, and then the Reynolds shear stress, the skewness and the flatness factors were calculated, and compared with the Gaussian value. Two pressure swirl stomizers were used for the twin spray system and kerosene was employed as the working liquid. 2-D PDA(particle dynamic analyzer) was used for the purpose of the measurement of droplet size and velocities. As a result, it was found that (1) the droplets collision was taken place strongly in the cross region. So, a large momentum loss of droplets due to the loss of natural movement direction was occurred, and momentum loss of radial direction was greater than that of axial direction. (2) The axial direction skewness factor approached to zero like the Gaussian distribution in the cross region of twin spray. (3) In the cross region of twin spray, the fluctuation instability of droplet was increased because of the development of the turbulence characteristics due to the droplet collision.

• 한국분무공학회지
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• 제3권3호
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• pp.42-48
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• 1998

This study describes the spray structure of gasoline port injectors by using phase Doppler particle analyzer(PDPA) and particle motion analysis system(PMAS). The characteristics of fuel spray such as the spray penetration, spray angle and breakup processes were obtained by PMAS and the droplet size and mean velocity were measured by PDPA system. Pintle type and two-hole type injectors were used as gasoline port fuel injectors under various injection pressures. The effect of injection pressure on the droplet mean diameter and axial mean velocity of droplet were investigated under the various injection conditions. In addition the comparison of breakup processes for the two types of injectors was also conducted. It Is shown that pintle type injector has smaller droplet size than that of two-hole type injector.

• International Journal of Automotive Technology
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• 제6권2호
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• pp.87-93
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• 2005

Spray patterns were visualized using the shadowgraph method, and the droplet size and velocity were measured using PDPA for high-pressure injections up to 2,600 bars. The spray pattern and spray characteristics, such as penetration, spray width, spray angle, droplet size, injection duration, and droplet velocity, were investigated to determine the suitable injection pressure. Spray penetration, width, angle, and velocity increased continuously up to 2,600 bars with the injection pressure in a high-pressure region. The rate of improvement of the above spray characteristics, however, declined rapidly, when the injection pressure reached 2,000 bars. The injection duration and droplet size generally decreased with the increase in the injection pressure, while the rate of improvement decreased abruptly after 2,000 bars. Consequently, the improvement rate of the spray characteristics became blunt at over 2,000 bars. This means that the suitable injection pressure is around 2,000 bars.

• 한국분무공학회지
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• 제4권2호
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• pp.10-18
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• 1999

The droplet/wall impingement processes in the diesel-like environment are numerically modeled. In order to evaluate the predictive capability of the droplet/wall impingement model developed in this study, computations are carried out for two ambient temperature conditions. Numerical results indicate that the present droplet/wall impingement model reasonably well predicts the basic features of the impinging spray dynamics.

• 한국분무공학회지
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• 제16권1호
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• pp.27-36
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• 2011

The impact force on the single and overlap region of twin spray was experimentally evaluated using visualization method in full cone type swirl nozzle spray. Visualization of spray was conducted to obtain the spray angle and breakup process. The photography/imaging technique, based on Particle Image Velocimetry (PIV) using high-speed camera, was adopted for the direct observation of droplet motion and axial velocity measurement, respectively. Droplet size was measured by Particle Motion Analyze System (PMAS). The purpose of this study is to provide fundamental information of spray characteristics, such as impact force, for higher etching factor in the practical wet etching system. It was found that the spray angle, axial velocity and impact force were increased with increasing the nozzle pressure while droplet size decreased with increasing the nozzle pressure. Droplet size increased as the distance from nozzle tip was decreased. The impact force of twin spray in the overlap region was about 63.29, 67.02, 52.41% higher than that of single spray at 40, 50 and 60 mm of nozzle pitch, respectively. Also, the nozzle pitch was one of the important factors in the twin spray characteristics.

• Journal of Mechanical Science and Technology
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• 제17권4호
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• pp.617-625
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• 2003

Effects of Injector nozzle geometry and operating pressure conditions such as opening pressure, ambient pressure. and injection pressure on the transient fuel spray behavior have been examined by experiments. In order to clarify the effect of internal flow inside nozzle on the external spray, flow details Inside model nozzle and real nozzle were alto investigated both experimentally and numerically. for the effect of injection pressures, droplet sizes and velocities were obtained at maximum line pressure of 21 MPa and 105 MPa. Droplet sizes produced from the round inlet nozzle were larger than those from the sharp inlet nozzle and the spray angle of the round inlet nozzle was narrower than that from the sharp inlet nozzle. With the increase of opening pressure, spray tip penetration and spray angle were increased at both lower ambient pressure and higher ambient pressure. The velocity and size profiles maintained similarity despite of the substantial change in injection pressure, however, the increased injection pressure produced a higher percentage of droplet that are likely to breakup.