• Journal of ILASS-Korea
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• v.6 no.2
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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.

• Journal of the Korean Society of Safety
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• v.32 no.4
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• pp.16-21
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• 2017

The sprinkler system is a basic fire extinguishing system that uses water as an extinguishing agent. In order to evaluate the fire extinguishing performance of the sprinkler system, information such as the discharge angle, discharge speed, discharge pressure, flow rate, and water droplet size of the installed head are required. However, there is a lack of research on droplets size compared to other requirements. In this study, to evaluate the extinguishing characteristics of sprinkler system, the droplet size distribution was measured for various types of sprinkler heads actually used. The size of the droplet was measured using laser diffraction method. The 50% cumulative volume distribution ($D_{v50}$) according to discharge coefficient(K factor) was $540{\mu}m{\sim}695{\mu}m$ for K50, $542{\mu}m{\sim}1,192{\mu}m$ for K80, $980{\mu}m{\sim}1,223{\mu}m$ for K115 and $1,188{\mu}m{\sim}1,234{\mu}m$ for K202. Based on the measured results, the vaeiance of the droplet particle distribution and the distribution ($D_{v50}$) according to discharge coefficient(K factor) was $540{\mu}m{\sim}695{\mu}m$ for K50, $542{\mu}m{\sim}1,192{\mu}m$ for K80, $980{\mu}m{\sim}1,223{\mu}m$ for K115 and $1,188{\mu}m{\sim}1,234{\mu}m$ for K202. Based on the measured results, the vaeiance of the droplet particle distribution and the Rosin-Rammler index value are presented. As a result of the fire simulation with FDS, it was confirmed that the performance difference occurs according to the water droplet size distribution even when the same amount of water is used. Therefore, the extinguishing performance of the sprinkler system should be evaluated considering the droplet size distribution according to the sprinkler head type.

• International Journal of Automotive Technology
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• v.2 no.4
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• pp.165-170
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• 2001

This study is focussed on the investigation of spray characteristics from the high pressure gasoline injector for the application of gasoline direct injection engine. For the analysis of spray structure of high pressure gasoline injector; the laser scattering method with a Nd-Yag laser and the Phase Doppler particle analyzer system were applied to observe the spray development and the measurement of the droplet size and velocity of the spray, respectively. Also spatial velocity distribution of the spray droplet was measured by use of the particle image velocity system. Experimental results show that high pressure gasoline injector shapes the hollow-cone spray, and produce the upward ring shaped vortex on the spray surface region. This upward ring shaped vortex promotes the secondary atomization of fuel droplets and contributes to a uniform distribution of fuel droplets. Most of fuel droplets are distributed under 31$\mu m$ of the mean droplet size (SMD) and the frequency distribution of the droplet size under 25$\mu m$ is over 95% at 7 MPa of injection pressure. According to the experimental results of PIV system, the flow patterns of the droplets velocity distribution in spray region are in good agreement with the spray macroscopic behaviors obtained from the visualization investigation.

• Journal of the Korean Society of Visualization
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• v.19 no.2
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• pp.32-40
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• 2021

Vapor-driven solutal Marangoni flow is governed by the concentration distribution of solutes on a liquid-gas interface. Typically, the flow structure is investigated by particle image velocimetry (PIV). However, to develop a theoretical model or to explain the working mechanism, the concentration distribution of solutes at the interface should be known. However, it is difficult to achieve the concentration profile theoretically and experimentally. In this paper, to find the concentration distribution of solutes around 2D droplet, the reverse tracking method with an artificial neural network based on PIV data was performed. Using the method, the concentration distribution of solutes around a 2D droplet was estimated for actual flow data from PIV experiment.

• Transactions of the Korean Society of Mechanical Engineers
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• v.15 no.2
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• pp.618-629
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• 1991

The purpose of this experiment is to understand the distribution of coal particles inside CWM droplet which is believed to be a very important factor controlling the flame stability. CWM slurry is atomized by an air assisted twin fluid nozzle. An experimental rig is designed and fabricated. The mean size of coal particle distribution in CWM slurry, atomizing air pressure, coal particle loading in slurry and sampling position inside spray are main experimental variables. The atomized CWM droplets are sampled on the thin white layer of magnesium oxide by the emergency sampling shutter. The sampled coal particles on magnesium oxide layers are collected into test tubes and dispersed completely by Ultra-Sonicator. The size distribution of coal particles inside droplets are measured by Coulter Counter. The presence of coal particle inside the impressions of droplets on magnesium oxide layer are investigated by photo technique. There are quite many droplets which do not have any coal particles. Those are just water droplets, not CWM droplets. The population ratio of droplets without coal particles to toal number of droplets is strongly affected by the mean size of coal particle distribution in slurry and this ration becomes bigger number as the mean size of coal particles be larger. The size distribution of coal particles inside CWM droplets is not even and depends on the size of droplet. Experimental results show that the larger CWM droplets has droplets has bigger mean value of particle size distribution. This trend becomes more evident as the atomizing air pressure is raised and the mean size of coal particles in CWM slurry is bigger. That is, the distribution of coal particles inside CWM dropolets is very much affected by the atomizing air pressure and the mean size of pulverized coal particles in CWM slurry.

• Journal of Biosystems Engineering
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• v.20 no.3
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• pp.236-244
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• 1995

Droplet size is one of the important factors in the deposition and drift of agrichemical application. In this study, droplet size and its distribution of the three different sizes of ceramic hollow cone nozzles being used in the air carrier sprayer for apple production were investigated at the various nozzle pressures and the three air velocities. The Malvern particle size analyzer were used for the measurement of droplet size and its distribution. The important results emerged from th is study can be summarized as follows. 1. Discharged rate was increase with the increase of the nozzle diameter and pressure, amount of the difference was remarkable between the nozzle diameter of 1.0, 1.2 and 1.5 mm, but no difference were found between the diameter of 1.0 and 1.2 mm in the same nozzle pressure. 2. Mass median diameter were varied as 40~160 ${mu}m$ at the air velocity of 0 m/s, 70~140 ${mu}m$ of 15 m/s and 100~160 ${mu}m$ of 20 m/s 3. It appeared that the air velocity range of 15~20 m/s was desirable for both drift and deposition control in the given experimental conditions.

• Journal of the Korean Society of Visualization
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• v.2 no.1
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• pp.25-31
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• 2004

Droplet size is one of the most important parameter which controls the performance of the combustion system using liquid fuel or oxidizer. Droplet formation and its size are mainly affected by the injection velocity and ambient gas density. Recently, droplet size measurement was conducted by PDPA or Malvern particle analyzer using laser light. But at this paper image processing method was developed to measure droplet size. And its validation was investigated with reticle.

• Journal of Institute of Convergence Technology
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• v.3 no.2
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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.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.3
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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.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.4
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• pp.1039-1049
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• 1994

The intermitternt and transient fuel spray have been investigated from the simultaneous measurement of droplet sizes and velocities by using Phase/Doppler Particle Analyzer(PDPA). Measurement have been done on the spray axis and at the edge of the spray near nozzle at various gas-to-liquid density ratios(.rho./sub g//.rho./sub l/) that ranges from those found in free atmospheric jets to conditions typical of diesel engines. Probability density distributions of the droplet size and velocity were obtained from raw data and mathematical probability density functions which can fit the experimental distribations were extracted using the principle of maximum likelihood. In the near nozzle region on the spray axis, droplet sizes ranged from the lower limit of the measurement system to the order of nozzle diameter for all (.rho./sub g/ /.rho./sub l/) and droplet sizes tended to be small on the spray edge. At the edge of spray, average droplet velocity peaked during needle opening and needle closing. The rms intensity is greatly incresed as the radial distance from the nozzle is increased. The probability density function which can best fit the physical breakage process such as breakup of fuel drops is exponecially decreasing log-hypebolic function with 4 parameters.