• Journal of Mechanical Science and Technology
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• v.14 no.10
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• pp.1143-1150
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• 2000

The effects of ambient conditions on vaporizing sprays from a high-pressure swirl injector were investigated by an exciplex fluorescence method. Dopants used were 2% fluorobenzene and 9% DEMA (diethyl-methyl-amine) in 89% solution of hexane by volume. In order to examine the behavior of liquid and vapor phases inside of vaporizing sprays, ambient temperatures and pressures similar to engine atmospheres were set. It was found that the ambient pressure had a significant effect on the axial growth of spray, while ambient temperature had a great influence on the radial growth. The spatial distribution of vapor phase at temperatures above 473K became wider than that of liquid phase after half of injection duration. From the analysis of the area ratio for each phase, the middle part (region II) in the divided region was the region which liquid and vapor phases intersect. For liquid phase, fluorescence-intensity ratio was greatly changed at lms after the start of injection. However, the ratio of vapor phase was nearly uniform in each divided region throughout the injection.

• Journal of Mechanical Science and Technology
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• v.16 no.7
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• pp.999-1008
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• 2002

The spray structures and distribution characteristics of liquid and vapor phases in non-evaporating and evaporating Gasoline Direct Injection (GDI) fuel sprays were investigated using Laser Induced Exciplex Fluorescence (LIEF) technique. Dopants were 2% fluorobenzene and 9% DEMA (diethyl-methyl-amine) in 89% solution of hexane by volume. In order to study internal structure of the spray, droplet size and velocity under non-evaporating condition were measured by Phase Doppler Anemometry (PDA). Liquid and vapor phases were visualized at different moments after the start of injection. Experimental results showed that the spray could be divided into two regions by the fluorescence intensity of liquid phase: cone and mixing regions. Moreover, vortex flow of vapor phase was found in the mixing region. About 5㎛ diameter droplets were mostly distributed in the vortex flow region. Higher concentration of vapor phase due to vaporization of these droplets was distributed in this region. Particularly, higher concentration of vapor phase and lower one were balanced within the measurement area at 2ms after the start of injection.

• Nuclear Engineering and Technology
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• v.26 no.2
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• pp.257-264
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• 1994

Experimental studies hate been peformed to investigate vapor explosion phenomena which may threaten the containment integrity during severe accidents in nuclear power plants. In this study, experimental equipment is constructed for vapor explosion experiments, and the vapor explosion experiments were conducted using water/R22. During the experiments, water/R22 interaction phenomena were observed using the high speed camera, and the explosion pressure and released mechanical energy were measured with pressure transducer and pressure relief tube. And the effects of some important parameters-hot liquid temperature, hot liquid injection velocity, hot liquid injection velocity, hot liquid injection time, and cold liquid depth-were investigated on the vapor explosion. Also, the experiment with grid was conducted to study reactor -vessel-lower-structure effect on fuel/coolant interaction. Water/R22 explosion conversion ratios were measured between 0.5∼1.6%.

• Transactions of the Korean Society of Automotive Engineers
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• v.11 no.6
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• pp.7-13
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• 2003

The purpose of this study is to investigate the effect of the in-cylinder flows and different injection timings on fuel behavior in the cylinder of a GDI engine. Three different flows types induced by using masked port, unmasked port, and port deactivation were tumble, swirl&tumble, and high swirl respectively. LIEF technique was applied to investigate the mixture formation and fuel distribution at ignition time in the transparent engine with optical access through the piston top and upper part of cylinder liner. Injection timings of 180,90, and 60 degrees before TDC were examined. It was found that tumble flow was more effective on the homogeneous mixture formation than other flow and swirl flow transported more fuel vapor to the exhaust side at early injection mode, and swirl and swirl & tumble flow made fuel vapor concentrate around the cylinder center at late injection mode.

• Journal of Mechanical Science and Technology
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• v.18 no.12
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• pp.2310-2318
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• 2004

The effects of change in injection pressure on spray structure in high temperature and pressure field have been investigated. The analysis of liquid and vapor phases of injected fuel is important for emissions control of diesel engines. Therefore, this work examines the evaporating spray structure using a constant volume vessel. The injection pressure is selected as the experimental parameter, is changed from 400 bar to 800 bar by using a common rail injection system. Also, we conducted simulation study by modified KIVA-II code. The results of simulation study are compared with experimental results. The images of liquid and vapor phase for free spray were simultaneously taken by exciplex fluorescence method. As experimental results, the vapor concentration of injected fuel is leaner due to the increase of atomization in the case of the high injection pressure than in that of the low injection pressure. The calculated results obtained by modified KIVA-II code show good agreements with experimental results.

• Journal of ILASS-Korea
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• v.3 no.2
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• pp.24-33
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• 1998

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 saturation vapor pressure of the butane(0.23MPa at $25^{\circ}C$). An accumulator type pintle injector and its fuel delivery system has been simulated in ruder to give injection pressure, needle lift and rate of fuel injected. The governing equation were solved by finite difference metho. The injection duration was controlled by solenoid valve. Spray behaviors such as a transient spray tip penetration, spray angle and SMD were calculated based on the empirical correlations in case that the back pressure is both above the vapor pressure of the butane and below that of butane. When the back preassure is below the vapor pressure of the fuel, conventional correlation is modified to represent the effect of flash boiling.

• Journal of Mechanical Science and Technology
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• v.19 no.12
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• pp.2281-2288
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• 2005

Because an injected spray development process consists of impinging and free spray in the diesel engine, it is needed to analyze the impinging spray and free spray, simultaneously, in order to study the diesel spray behavior. To dominate combustion characteristics in diesel engine is interaction between injected fuel and ambient gas, that is, process of mixture formation. Also it is very important to analyze liquid and vapor phases of injected fuel on the investigation of mixing process, respectively and simultaneously. Therefore, in this study, the behavior characteristics of the liquid phase and the vapor phase of diesel spray was studied by using exciplex fluorescence method in high temperature and injection pressure field. Finally, it can be confirmed that the distribution of vapor concentration is more uniform in the case of the high injection than in that of the low injection pressure.

• Korean Journal of Food Science and Technology
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• v.17 no.5
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• pp.406-408
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• 1985

n-Hexanal in headspace over the cooked brown rice stored at $5^{\circ}C$ and $35^{\circ}C$ for 0. 4, 8 and 12 months was determined by a modified direct vapor injection gas chromatographic method. The retention time of n-hexanal was 3.5 min and n-hexanal could be rapidly separated from other compounds at the operational conditions of gas chromatography. n-Hexanal contents of cooked brown rice also showed a standard deviation of less than 10% of the average.

• Journal of computational fluids engineering
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• v.5 no.1
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• pp.8-13
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• 2000

In this study, the spray models incorporated into the GTT code were tested for sprays injected in quiescent swirling gases and for the sprays impinging on a flat wall, and the validity of the models has been confirmed by comparing the calculated results with the experimental data. Using this code, the gas flow, spray behavior and fuel vapor distributions in the combustion chamber of a D.I engine have been numerically analyzed with respect to the constant injection pressure and the injection pressure varying with injection time.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.29 no.3 s.234
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• pp.356-367
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• 2005

The spray characteristics of DISI injector have a great role in gasoline engine efficiency and emission. Thus, many researchers have studied to investigate the spray characteristics of swirl and slit injectors that are used in a DISI engine. In this study, we tried to provide spray parameters, which affect on the spray characteristics such as injection pressure, ambient pressure and ambient temperature. In addition, we calculated $t_{b}\;and\;t_{c}$ to investigate the break up mechanism of test injectors and obtained $C_{v}$ to evaluate the spray characteristics. As the ambient pressure increases in case of slit injector, $C_{v}$ decreases. The laser-induced exciplex fluorescence (LIEF) technique, which is based on spectrally resolved two-color fluorescent emissions, has applied to measure the liquid and vapor phases for on evaporating spray simultaneously. The TMPD/naphthalene proposed by Melton is used as a dophant to detect exciplex signal. The temporal and spatial distribution of liquid and vapor phases during the mixture formation process was measured by this technique. In the LIEF technique, the vapor phase is detected by the monomer fluorescence while the liquid phase is tracked by the exciplex fluorescence. From this experiment, we found that the spray area of the vapor phase is increased with elapsed time after injection and the area of liquid is decreased when the ambient pressure is 0.1MPa. However, the area tends to increase until the end of injection when the ambient pressure is 1.0MPa.