• 한국연소학회:학술대회논문집
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• 2005.10a
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• pp.120-131
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• 2005

The evaporation characteristics of single and multicomponent droplets hanging at the tip of a quartz fiber are studied experimentally at the different environmental conditions under normal gravity. Heptane and Hexadecane are selected as two fuels with different evaporation rates and boiling temperatures. At the first step, the evaporation of single component droplet of both fuels has been examined separately. At the next step the evaporation of several blends of these two fuels, as a binary component droplet, has been studied. The temperature and pressure range is selected between 400 and 700 $^{\circ}C$, and 0.1 and 2.5 MPa, respectively. High temperature environment has been provided by a falling electrical furnace. The initial diameter of droplet was in range of 1.1 and 1.3 mm. The evaporation process was recorded by a high speed CCD camera. The results of binary droplet evaporation show the three staged evaporation. In the the first stage the more volatile component evaporates. The droplet temperature rises after an almost non evaporating period and in the third stage a quasi linear evaporation takes place. The evaporation of the binary droplet at low pressure is accompanied with bubble formation and droplet fragmentation and leads to incomplete microexplosion. The component concentration affects the evaporation behavior of the first two stages. The bubble formation and droplet distortion does not appear at high environment pressure. Nomenclature

• Journal of the Korean Society of Propulsion Engineers
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• v.3 no.3
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• pp.9-15
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• 1999

The Analysis of spray characteristics for combined spray group are necessary to develop large rocket engine. In this study, basic effects of interaction from spray fan formed by impinging jets were investigated with respect to mass distribution, droplet velocities and diameter. Patternater and PDPA are used for experimental apparatus. Water was used as a test fluid When momentum ratio is 1, effect of interaction from collision of spray fan on mass distribution are small. Also, effect of interaction from collision of spray fan on droplet velocities and diameter are small. But, droplet diameter is smaller near collision point due to second collision. Therefor, for the same momentum ratio from spray fan formed by impinging jets, we may neglect effect of interaction on mass distribution, droplet velocities and diameter.

• International Journal of Automotive Technology
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• v.6 no.6
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• pp.563-570
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• 2005

A numerical study of high pressure and temperature droplet vaporization and combustion is conducted by formulating one dimensional evaporation model and single-step chemical reaction in the mixture of hydrocarbon fuel and air. The ambient pressure ranged from atmospheric conditions to the supercritical conditions. In order to account for the real gas effect on fluid p-v-T properties in high pressure conditions, the modified Soave-Redlich-Kwong state equation is used in the evaluation of thermophysical properties. Some computational results are compared with Sato's experimental data for the validation of calculations in case of vaporization. The comparison between predictions and experiments showed quite a good agreement. Droplet surface temperature increased with increasing pressure. Ignition time increased with increasing initial droplet diameter. Temporal or spatial distribution of mass fraction, mass diffusivity, Lewis number, thermal conductivity, and specific heat were presented.

• Journal of the Korean Society of Safety
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• v.20 no.1 s.69
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• pp.68-74
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• 2005

The objective of the present work is to examine the evaporation shape of deposited droplet on the hot surface. this paper performed the experiments as following conditions: (a) the surface temperature is within the range between $80^{\circ}C$ and $95^{\circ}C$ in the conduction and radiation, (b) droplet diameter is 3.0mm. The results are as follows; while droplet evaporates, droplet's radius is kept changelessly to $70\%$ evaporation time and droplet's shape is kept changelessly after. In case use Constant radius model, about $10\%$ is appearing high than value that time-averaged heat flux applies Inverse heat conduction.

• Journal of ILASS-Korea
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• v.12 no.4
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• pp.198-203
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• 2007

In the present work, surface wetting effect on spread-splash regime and transition criterion of the water and ethanol droplets impacting an unheated dry wall has been experimentally investigated. The droplet was directed on a polished STS plate and a glass slide, and the impinging behavior was visualized and recorded using a CCD camera. Droplet diameter and velocity approaching the wall were measured as well. The critical Sommerfeld number representing the spread-splash boundary for the ethanol droplet impinging on the substrates turned out to be smaller compared to that for the water droplet impinging on the substrates with the surface roughness condition remained unchanged. The shift of the transition boundary is considered to be due to the effect of the surface wettability represented by static contact angle and surface tension of droplet.

• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.6
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• pp.1529-1538
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• 1995

In this study, a liquid sheet type co-axial nozzle has been used to investigate the turbulent atomization characteristics which could result in the experimental data to be used in designing a jet nozzle with high performance. Image processing technique and immersion sampling method were employed to measure droplet size. In atomizing characteristics, droplet size distributions and absolute droplet sizes, SMD(Sauter Mean Diameter) have been investigated in the wide ranges of flow field depending upon the air-water mass ratios. And the comparisons between the present data and the semi-empirical curves have been conducted semi-empirical correlation for SMD has been derived in the present analysis.

• Journal of Biosystems Engineering
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• v.35 no.3
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• pp.158-162
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• 2010

The effect of fuel injection characteristics on engine performance has been known for improving fuel economy and emission reduction. In this study, the spray characteristics of crude palm oil blended fuel with conventional diesel fuel was investigated. The experiments were performed to evaluate the effect of crude palm oil blending ratio and injection pressure on the spray behavior. The droplet size of injected fuel was analyzed through laser diffraction particle analyzer (LDPA). Also, spray atomization characteristics were investigated in terms of Sauter mean diameter (SMD) and droplet distribution at various injection conditions. Fuel containing crude palm oil has different spray pattern on account of the high viscosity. Through those experimental results, we found that the increase of blending ratio made droplet size larger, SMD of biodiesel 100% was increased 30.2% than that of diesel fuel 100% under injection pressure of 60 MPa.

• Journal of ILASS-Korea
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• v.9 no.3
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• pp.1-7
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• 2004

This experiment was undertaken to investigate the atomization characteristics of the low viscosity biodiesel blended fuel and ultrasonic energy added one. Test fuels were conventional diesel fuel and biodiesel fuel. We compared to the characteristics of viscosity and surface tension, SMD between low viscosity biodiesel blended fuel and ultrasonic energy added one. Sauter mean diameter was measured under the variation of the spray distance. Viscosity and surface tension was measured under the variation of the time trace. To measure the droplet size, we used the Malvern system 2600C. Droplet size distribution was analyzed from the result data of Malvern system. Through this experiment, we found that the condition of the ultrasonic energy added situation had smaller Sauter mean diameter of droplet, viscosity and surface tension than that of the conventional situation.

• Nuclear Engineering and Technology
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• v.50 no.3
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• pp.379-388
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• 2018

Models for the rate of atomization and deposition of droplets for stratified and annular flow in horizontal pipes are presented. The entrained fraction is the result of a balance between the rate of atomization of the liquid layer that is in contact with air and the rate of deposition of droplets. The rate of deposition is strongly affected by gravity in horizontal pipes. The gravitational settling of droplets is influenced by droplet size: heavier droplets deposit more rapidly. Model calculation and simulation results are compared with experimental data from various diameter pipes. Validation for the suggested models was performed by comparing the Safety and Performance Analysis Code for Nuclear Power Plants calculation results with the droplet experimental data obtained in various diameter horizontal pipes.

• Journal of the Korean Society of Visualization
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• v.19 no.3
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• pp.39-45
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• 2021

An experiment to visualize fine dust captured by FOG droplet is conducted. Coal dust with 23.56 MMD (Mean Median Diameter) and water with 17.02 MMD is used as fine dust and FOG droplet. Long distance microscope and high-speed camera are used to capture the images of micro-scale particles sprinkled by acrylic duct. After measuring and comparing the size of the coal dust and FOG droplet to MMD, process to seize the coal dust with FOG droplet is recorded in 2 conditions: Fixed and Floated coal dust in the floated FOG droplet flow. In both conditions, a coal dust particle is collided and captured by a FOG droplet particle. A FOG droplet particle attached at the surface of the coal dust particle does not break and remains spherical shape due to surface tension. Combined particles are rotated by momentum of the particle and fallen.