• 한국분무공학회지
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• 제8권2호
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• pp.7-15
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• 2003

The effects of fuel density and fuel viscosity on spray characteristics were investigated under two different gas turbine fuels and various fuel supply pressure conditions through measurement of SMD, number density and volume flux by using PDPA system in dual orifice injector for gas turbine engines. In this study, we found out that the droplet size and spray structure are strongly depend on fuel density for dual orifice injector. The spray characteristics of high density fuel in dual orifice injector are similar with the characteristics of low density fuel in single orifice injector. The shear region between primary main fuel stream and secondary main fuel stream is examined in low density fuel condition but not exist in high density fuel condition, then this shear region is very important in quality of gas turbine spray. There are worth consideration for the effect of fuel density on spray characteristics in frontal device design to improve combustion efficiency.

• Journal of Mechanical Science and Technology
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• 제19권12호
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• pp.2253-2262
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• 2005

The focus of this work is placed on the analysis of the mixture formation mechanism under the evaporative diesel spray of impinging and free conditions. As an experimental parameter, ambient gas density was selected. Effects of density variation of ambient gas on liquid and vapor-phase inside structure of evaporation diesel spray were investigated. Ambient gas density was changed between ${\rho}a=5.0\;kg/m^3$ and $12.3\;kg/m^3$. In the case of impinging spray, the spray spreading to the radial direction is larger due to the decrease of drag force of ambient gas in the case of the low density than that of the high density. On the other hand, in the case of free spray, in accordance with the increase in the ambient gas density, the liquid-phase length is getting short due to the increase in drag force of ambient gas. In order to examine the homogeneity of mixture consisted of vapor-phase fuel and ambient gas in the spray, image analysis was conducted with statistical thermodynamics based on the non-dimensional entropy (S) method. In the case of application of entropy analysis to diesel spray, the entropy value always increases. The entropy of higher ambient density is higher than that of lower ambient gas density during initial injection period.

• 한국분무공학회지
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• 제4권2호
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• pp.40-46
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• 1999

Experimental investigation of unsteady impinging diesel spray on the flat plate have been carried out using high speed camera and Malvern system. The density ratios of ambient gas to diesel fuel were varied using $N_2$ and Ar gas in the case of 14.9, 21.2, 28.4, 35.1, 40.4, and 50.1. With the increase of gas density ratio, the radial penetration is decreased due to the resistance of the ambient gas. With the increase of the gas density ratio and the distance between nozzle tip and flat plate, the height of spray is increased due to the entrance and circulation. With the increase of gas density ratio, SMD is decreased on the nearby position at the center of flat plate, but SMD is increased on the far position. As the distance between nozzle tip and flat plate is increased, SMD is always decreased.

• 대한기계학회논문집
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• 제18권4호
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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.

• 한국터널지하공간학회 논문집
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• 제13권1호
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• pp.1-8
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• 2011

장대 도로터널 및 위험도가 높은 도로터널에 설치되고 있는 물분무소화설비는 성능과 관계된 단위면적당 방수밀도에 대한 검증과정이 없이 사용되어 왔다. 본 연구는 도로터널에 물분무소화설비에 노즐을 설치하여 기준압력에서 방수시험을 실시하여 기준을 만족하는지 여부를 확인하였다. 결론적으로 모든 노즐이 기준을 만족하지 못하였다. 이런 결과는 도로터널용 물분무노즐을 검증하는 시험기준이 없고, 실제 시험을 통한 검증 과정이 존재하지 않았기 때문이라고 판단된다. 따라서 물분무노즐의 성능을 시험할 수 있는 기준의 마련과 설치된 시설을 검증하는 제도적인 보완이 필요하다.

• 한국자동차공학회논문집
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• 제10권3호
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• pp.36-43
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• 2002

The characteristics of spray has much effect on performance and emissions for automobile, diesel engine, gas turbine and combustion engines. So spray behavior after impinging the wall is very important for prediction the engine performance. This studies examined about impingement spray considering ambient density(18,24,30kg/ms), temperature(293,473K), impingement angle(0,30,45°). The images of impingement spray were obtained by the high speed video camera. After that we analyzed impingement spray characteristics to use this images. In this experiment, we found that 1) The spray width is reduced by increasing the ambient gas density and temperature,2) The growth of downstream is increased by increasing the impingement angle.

• 한국분무공학회지
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• 제5권1호
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• pp.30-40
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• 2000

The characteristics of liquefied butane spray are expected to be different from conventional diesel fuel spray, because a kind of flash boiling spray is expected when the back pressure is below the saturated vapor pressure of the butane(0.23MPa at 298K). The ambient pressure was held at a pressure above(0.37MPa) and below(0.15MPa) the fuel vapor pressure. The axial velocities, radial velocities, and size distributions in butane sprays were measured with PDPA(Phase Doppler Particle Analyzer) system. The PDPA measurement showed a smaller SMD at the 0.15MPa chamber pressure, compared to the 0.37MPa case. Log-hyperbolic density function for the droplets size distribution can be fitted to the experimental results of a liquefied butane spray.

• 대한기계학회논문집B
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• 제33권8호
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• pp.589-595
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• 2009

The instability wave formed near nozzle region grows to vortex with large scale in downstream region of spray. It plays an important role in the fuel-air mixing, combustion process and engine exhaust emissions in direct injection diesel engine. The objective of this study is to analyze effect of variant parameters (injection pressure, ambient gas density, etc.) and fuel properties on spray instability near nozzle region. Spray structure near nozzle region was investigated using a magnification photograph. A pulsed Nd-YAG laser was used as a light source, and image was taken by CCD camera. The following conclusions are drawn from this experimental analysis. In low ambient density, the effect of fuel properties on spray instability near nozzle region is dominant. In high ambient density, the effect of ambient gas on spray instability near nozzle region is dominant. High jet velocity has strong influence on spray instability.

• 한국자동차공학회논문집
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• 제17권2호
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• pp.82-89
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• 2009

In order to investigate the spray characteristics according to diesel and bioethanol blending with biodiesel fuel, macroscopic spray characteristics were analyzed from the comparison of the effect of the injection pressure, ambient pressure and density on the spray tip penetration and spray cone angle. In addition, spray atomization characteristics were studied with local and overall Sauter mean diameter (SMD) and the contour map of SMD distribution at various injection conditions. It was revealed that the spray tip penetration of biodiesel fuels blended with diesel and ethanol was shorter than that of an undiluted biodiesel fuel at low injection pressure. However, the difference of spray tip penetration among three test fuels reduces at a high injection pressure. Increase of the ambient gas density leads to the decrease of the spray tip penetration of three test fuels. When diesel and ethanol fuels add to an undiluted biodiesel fuel, spray cone angle increases due to the decrease of the fuel density at the same ambient pressure condition. On the other hand, the droplet mean diameter decreases due to the reduction of the kinematic viscosity and surface tension.

• 대한기계학회논문집
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• 제19권2호
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• pp.548-558
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• 1995

An experimental investigation has been conducted to study the spray and combustion characteristics using the air-assisted twin fluid atomizer. Axial mean and fluctuating velocity components as well as drop-size distributions in non-reaction spray were measured with a nonintrusive phase doppler technique. Droplet number density distributions were also visualized using high speed CCD camera. Locations of spray and flame boundaries are obtained by direct photographic method. It is confirmed that at the fixed fuel flow rate, the increase of the atomizing air flow causes improvements on both spray and combustion characteristics under stable flame conditions. Internal group combustion modes where flame is located inside the spray boundary are observed to exist in the upstream region of higher droplet number density.