• Journal of Advanced Marine Engineering and Technology
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• v.37 no.1
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• pp.22-28
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• 2013

The heat transfer characteristics of LNG(Liquefied Natural Gas) vaporizer on the ship was performed by numerical simulation to get the optimum NG(Natural Gas) generating condition. The glycol-water was used for heating in LNG vaporizer, and the cooling water of main engine was used as heating souse for glycol-water. This cooling water temperature increases again after recirculating from the main engine, and then it can be used to heat the glycol-water. The numerical analysis results has good agreement with the experimental results by liquid nitrogen for validation. So CFD technique was used to simulate the heat transfer characteristics of LNG vaporizer on the ship. The numerical results show that the operation condition of LNG vaporizer shows NG temperature of $6^{\circ}C$ in the outlet of LNG vaporizer, and the mass flow rates of LNG and glycol-water were showed 0.111 kg/s and 1.805 kg/s, respectively.

• Journal of Aerospace System Engineering
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• v.18 no.3
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• pp.70-75
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• 2024

The insulation performance of a common bulkhead propellant tank for small launch vehicles with variations in insulation thickness was analyzed. The common bulkhead propellant tank composed of a single part allows for lightweight design, as it eliminates the need for tank connections. However, problems such as propellant loss and ignition delay due to heat transfer caused by temperature differences between oxidizer and fuel may arise. Therefore, it is essential to verify the insulation performance of the common bulkhead structure that separates the oxidizer tank and fuel tank. In this study, transient heat transfer analysis was conducted for propellant tanks with insulation thicknesses of (50, 55, 60, 65, and 70) mm to analyze the insulation performance using boil-off mass. Subsequently, the boil-off mass of the oxidizer generated during the first-stage flight time of the propellant tank was determined. The results confirmed that increasing the insulation thickness reduces the boil-off mass, thereby improving the insulation performance.

• Journal of Energy Engineering
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• v.11 no.2
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• pp.178-185
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• 2002

The object of this paper is to investigate the effects of early fuel evaporators on cold driveability of gasoline passenger cars. Experiment has been carried out for the assessment cold start performance and cold driveability. And fuel consumption rate, emission and cylinder pressure were measured. On the base of combustion pressure of cylinder, rate of heat release, cumulative heat release amount and burned mass fraction are evaluated. The results show that fuel consumption rate is increased by 17.7%, monoxide and hydrocarbon were reduced by 23% and by 45% respectively, fluctuations of indicated mean effective pressure and maximum combustion pressure were increased by 4∼6%, fuel consumption rate per power was improved by 0.2∼2.3%. These are caused by the fact maximum heat release period and main combustion period are getting short.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.39 no.3
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• pp.232-241
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• 2011

The hybrid rocket shows interesting characteristics of complicated mixing layer developed by the interaction between turbulent oxidizer flow and injected surface mass flow from fuel vaporization. In this study, the compressible LES was conducted to explore the physical phenomena of surface oscillatory flow induced by the flow interferences in a duct domain. From the numerical results, the wall injection generates the stronger streamwise vorticites and the negative components of axial velocity accompanied with the azimuthal vorticity near the surface. And the vortex shedding with a certain time scale was found to be developed by hydrodynamic instability in the mixing layer. The pressure fluctuations in this calculation exhibit a peculiar peak at a specific angular frequency($\omega$=8.8) representing intrinsic oscillation due to the injection.

• Fire Science and Engineering
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• v.33 no.6
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• pp.80-86
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• 2019

In Korea, a total of 556 chemical accidents occurred from 2012 to 2018 caused by adverse reactions of two or more chemicals, which required significant amounts of time to identify the causative chemicals. Rapid analysis is required for effective incident response and probing. In this study, a quantum transition time-of-flight mass spectrometer was used to identify the causative agents of chemical accidents caused by adverse reactions. The analyzer enabled fast real-time analysis without the need for sample collection and pretreatment. Quantitative and qualitative analysis of most volatile organic compounds with high hydrogen affinity was performed to investigate the cause of the chemical accidents. In fact, in the month of 201◯, methanol and toluene were detected as causative agents of the accident using a quantum transition time mass spectrometer, and were also the cause of the reported odor.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.5
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• pp.2005-2010
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• 2011

Since recently exhaust gas regulation for a non-road small engine as well as commercial vehicle engine has been enforced, a carburettor of a small engine should be replaced by an electronic fuel injection system. In this study, the spray characteristics of the 400cc gasoline small engine injector has been experimentally analyzed. Based on the experimental results, suitable injector for the small engine has been selected. Through the test rig measuring spray mass distribution, fuel distribution characteristics of 3 hole- and 6 hole-injector has been analyzed. Through the visualization equipment, injector spray angle, penetration length and spray width have been measured and analyzed. Considering spray characteristics and stability, 6 hole-injector is selected for the 400cc gasoline small engine.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.40 no.9
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• pp.745-751
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• 2012

Hybrid rocket shows interesting characteristics of complicated mixing layers developed by interactions between turbulent oxidizer flow and mass flow from surface due to fuel vaporization. In this study, compressible LES with a ring structure attached at the entrance of the combustor are performed. According to one recent report, adding a ring structure in the middle of the combustor helps increasing regression rate. From the numerical results, it is seen that vortex structures near the wall becomes stronger due to the interaction with surface mass injection, and the local heat flux increases due to the vortices. This phenomenon is obviously related to the generation of dimple structures which are seen in the number of experiments. Also, the ring structure at the entrance induces strong vortex flow which enhances heat transfer to the wall surface and mixing between fuel and oxidizer as well as reaction efficiency.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.9
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• pp.1736-1743
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• 1992

The combustion in the cylinder of spark ignition engine is completed after the delayed time that the liquid film fuel is vapourized as flowing into the combustion chamber. It is necessary to enhance the homogeneity of mixture and the combustion phenomenon in order to improve the heat efficiency and the emission characteristics of spark ignition engine. The main purpose of this paper is to manufacture a combustion analyzing system and examine closely the influence of non-uniformity due to the liquid film fuel flowing in the intake manifold on the combustion characteristics by using a 4 stroke multi- cylinder spark ignition engine. Moreover, with each cylinder, the interpretation of combustion characteristics by indicator diagram and the concentration of exhaust gas were investigated.

• Fire Science and Engineering
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• v.32 no.6
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• pp.84-90
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• 2018

Chemical accidents occur in various forms, such as explosions, leaks, spills, and fires. In particular, chemical accidents caused by fires seriously affect the surrounding air environment due to soot, causing anxiety to the residents. Therefore, it is important to identify the causative substances quickly and examine the influence of air quality in the surrounding area. In this paper, proton transfer reaction-time of flight mass spectrometry(PTR-ToFMS) was used to identify the causative material in a fire and monitor the air quality in real time. This analyzer is capable of real-time analysis with a rapid response time without sample collection and pretreatment. In addition, it is suitable for quantitative and qualitative analysis of most volatile organic compounds with high hydrogen affinity, to identify the cause of fire and examine the influence of ambient air. In April 2018, when a local fire occurred, methanol, acetone, and methyl ethyl ketone were the main causative agents in PTR-ToFMS.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.27 no.3
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• pp.144-157
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• 2022

Noble gases, which are chemically inert and behave conservatively in marine environments, have been used as tracers of physical processes such as air-sea gas exchange, mixing of water masses, and distribution of glacial meltwater in the ocean. For precise measurements of Ne, Ar, and Kr, we developed a mass spectrometric system consisting of a quadrupole mass spectrometer (QMS), a high vacuum preparation line, an activated charcoal cryogenic trap (ACC), and a set of isotope standard gases. The high vacuum line consists of three sections: (1) a sample extraction section that extracts the dissolved gases in the sample and mixes them with the standard gases, (2) a gas preparation section that removes reactive gases using getters and separates the noble gases according to their evaporation points with the ACC, and (3) a gas analysis section that measures concentrations of each noble gas. The ACC attached to the gas preparation section markedly lowered the partial pressures of Ar and CO₂ in the QMS, which resulted in a reduced uncertainty of Ne isotope analysis. The isotope standard gases were prepared by mixing ²²Ne, ³⁶Ar, and ⁸⁶Kr. The amounts of each element in the mixed standard gases were determined by the reverse isotope dilution method with repeated measurements of the atmosphere. The analytical system achieved precisions for Ne, Ar, and Kr concentrations of 0.7%, 0.7%, and 0.4%, respectively. The accuracies confirmed by the analyses of air-equilibrated water were 0.5%, 1.0%, and 1.7% for Ne, Ar, and Kr, respectively.