• 한국분무공학회지
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• 제2권3호
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• pp.25-31
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• 1997

This experiment was undertaken to investigate the spray characteristics of the conventional injection system and the ultrasonic energy added injection system. Test fuels include light oil and mixed light-BC oil. The mixed light-BC oil was injected at the normal temperature$(20^{\circ}C)$ and the high temperature$(95{\pm}2^{\circ}C)$ and injection pressure was $120kg/cm^2$. Sauter mean diameter was measured under the variation of the spray distance. To measure the droplet size, we used the Malvern system 2600C. Droplet size distribution was analyzed from the result data of Malvern system. It is also found that the condition of the ultrasonic energy added injection and high temperature injection generates the smaller droplets than that of the conventional injection.

• 한국분무공학회지
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• 제1권1호
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• pp.35-43
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• 1996

A vaporization model for single component fuel droplet has been developed for applying to sub- and supercritical conditions. This model can account for transient liquid heat ins and circulation effect inside the droplet, forced and natural convection, Stefan flow effect, real gas effect and ambient gas solubility into the liquid droplet in high-pressure conditions. Thermodynamic and transport properties are calculated as functions of temperature and pressure in both phases. Numerical calculations are carried out for several validation cases with the detailed experimental data. Numerical results confirm that this supercritical vaporization model is applicable to the high-pressure conditions encountered in the combustion processes of diesel engine.

• 오토저널
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• 제14권5호
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• pp.41-53
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• 1992

The main purpose of this study is to investigate the atomizing characteristics of a two phase spray by using a liquid column type coaxial nozzle. The experiments have been carried out to analyze the atomization behavior, the droplet size distributions, and the statistical properties of droplet size distributions. Immersion sampling method and the image processing technique were adapted for the measurements of particles, and the distributions of the droplet sizes were statistically analyzed. In the experiments, the mass ratio defined as Mr= $M_{\sigma}$/ $M_{1}$ has been changed from 1.0 to 3.4 and the measurements have been performed along the axis of the spray. As a result of this experimental study, the distributions of droplet size were satisfied with the Log-Normal distributions and arithmetic mean diameter and deviation of mass ratio. Droplet volume-surface mean diameter was denoted by a exponential function of mass-ratio and the exponent was denoted by linear relation according to the central axis from the nozzle. Dispersions, skewness factors and flatness factors had comparatively constant values regardless of mass ratio and location.

• 한국분무공학회지
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• 제20권3호
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• pp.175-180
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• 2015

A series of sprinkler discharging tests was conducted to measure the droplet size and its distribution of residential fire sprinkler heads. Droplet sizes in sprinkler spray were measured using a laser diffraction method for the flush, circular and pendent type sprinkler head. In this study, the $D_{v,50}$ of the flush type sprinkler heads were ranged between $530{\sim}1040{\mu}m$ and those of circular and pendent type were $988{\mu}m$ and $916{\mu}m$, respectively. The measured cumulative volume distributions were followed by a combination of the log-normal and Rosin-Rammler distribution which is widely used in the computational fire analysis and the parameters of distribution function were obtained from the best fit line through the measured data.

• 한국분무공학회지
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• 제9권3호
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• pp.42-49
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• 2004

The present article investigates the influence of droplet drag models on predictions of diesel spray behaviors under ultra-high injection pressure conditions. To consider drop deformation and shock disturbance, this study introduces a new hybrid model in predicting drag coefficient from the literature findings. Numerical simulations are first conducted on transient behaviors of single droplet to compare the hybrid model with earlier conventional model. Moreover, using two different models, extensive numerical calculations are made for diesel sprays under ultra-high pressure sprays. It is found that the droplet drag models play an important role in determining the transient behaviors of sprays such as spray tip velocity and penetration lengths. Numerical results indicate that this new hybrid model yields the much better conformity with measurements especially under the ultra-high injection pressure conditions.

• 한국분무공학회지
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• 제19권1호
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• pp.15-18
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• 2014

In the present study, experiment on the evaporation of pure water droplet on heated surface was conducted, and the evaporative heat transfer coefficients were calculated from experimental results. The pure water droplet of about $10{\mu}l$ was applied onto the heat transfer surface, then the shape of the droplet was analyzed during the evaporation. In addition, the effect of surface roughness on the evaporative heat transfer was also investigated. Experimental results showed that the evaporative heat transfer coefficients increased rapidly along with the increase of surface temperature and the heat transfer coefficients increased with the increase of surface roughness.

• Journal of Advanced Marine Engineering and Technology
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• 제26권1호
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• pp.132-137
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• 2002

Recently, impinging spray is used for atomization of diesel engine, but it bring on adhesion of fuel. Therefore, we studied about droplet behavior on high temperature plate changing the size of droplet, surface temperatures, and surface roughness of plate. In this study, We studied to confirm experimentally about mechanism of evaporation and ignition process of single fuel droplet. We observed evaporation time, evaporation appearance and ignition delay time by the photopraphs of 8mm video camera. Experimental results are summarized as follows: 1. The boiling point of fuel affect a evaporation and ignition process. 2. The surface roughness affect a evaporation time. 3. The ignition delay time relate to evaporation characteristic.

• 한국분무공학회지
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• 제21권1호
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• pp.53-57
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• 2016

The present study aims to experimentally investigate the evaporative heat transfer characteristics of Oxi-nitriding SPCC surface. Moreover, the heat transfer coefficient was examined with respect to surface temperature during droplet evaporation. In fact, the nitriding surface showed significant enhancement for anticorrosion performance compared to bare SPCC surface but the thermal resistance also increased due to the formation of compound layer. From the experimental results, the evaporative behavior of sessile droplet on nitriding surface showed similar tendency with the bare surface. Total evaporation time of sessile droplet on the nitriding surface was delayed less than 5%. The difference in heat transfer coefficient increased with the surface temperature, and the maximum difference was estimated to be around 11% at $80^{\circ}C$ surface. Thus, this nitriding surface treatment method could be useful for seawater heat exchanger industries.

• 한국분무공학회지
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• 제26권2호
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• pp.73-80
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• 2021

Evaporation characteristics of single butanol gel fuel were investigated in different mass ratios of gellant and ambient temperatures. Gel fuel was made by adding the pure water and hydroxypropylmethyl cellulose (HPMC) into the 1-butanol. Increase of viscosity was observed when the loading of HPMC increased. The evaporation process of gel droplet could be divided into three stages: droplet heating, micro-explosion and crust formation. Elevation of ambient temperature helped boost the evaporation in all experimental cases, but the effect was mitigated when the mass ratio of HPMC increased. Increase of HPMC weight ratio reduced the evaporation rate.

• 한국분무공학회지
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• 제26권3호
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• pp.120-126
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• 2021

Combustion characteristics of a 1-butanol gel fuel were studied in atmospheric pressure condition. The butanol gel fuel was manufactured by adding hydroxypropyl-methyl cellulose (HPMC) as a gellant and the effect of the gellant concentration was observed. The combustion process of a single butanol gel droplet was divided into 3 stages including droplet heating, microexplosion, and gellant combustion. The flame was distorted compared to butanol + water mixture because of micro-explosion during the combustion. Increase of gellant concentration delayed the droplet ignition, but the combustion rate was improved due to the mass ejection during the micro-explosion.