• 한국연소학회:학술대회논문집
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• 2005.10a
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• pp.305-313
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• 2005

Measurements of flame length, width and NOx emissions have been conducted to investigate the effect of an acoustic excitation on flame structure in turbulent hydrogen diffusion flames with coaxial air. The resonance frequency of oscillations was varied between 259 ,514 and 728 Hz with power rate of 0.405 and 2.88w. When these frequencies imposed to hydrogen flames, dramatic reduction of flame length and NOx emission was achieved. And acetone planar laser-induced fluorescence technique was used to measure a concentration of the near field of driven axisymmetric jet. The air-fuel stoichiometric line was plotted to investigate the mixing layer and development of air entrainment to fuel jet. Consequently, acoustic excitation on flame could enhance the air-fuel mixing resulting in abatement of NOx emission quantitatively.

• 한국연소학회:학술대회논문집
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• 2012.04a
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• pp.245-246
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• 2012

The possibility that self-ignition can be generated near an obstacle is high in practical applications such as a hydrogen car. In this paper, experimental investigations were suggested to understand the effects of a wall on self-ignition phenomena through high-speed images. The results showed that the existence of a wall could not change the ignition phenomena itself irrespective of wall height and burst pressure. However, when a strong flame was induced in the tube, a wall could promote the flame stabilization.

• Transactions of the Korean hydrogen and new energy society
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• v.30 no.3
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• pp.243-250
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• 2019

In this study, to ensure the safety of the packaged hydrogen refueling system, the improvement plan was derived by using 3-dimensional CFD program (FLACS). We also confirmed the effectiveness of risk reduction and the suitability of safety standard. By ventilation performance evaluation according to the position of the vent, it demonstrated that the vent should be installed at the ceiling to safely ventilate without stagnation of the leaked gas. In case of ventilation system according to KGS standard, risk situation could be resolved after about 5 minutes in the worst leaked condition. The result showed that jet fire and explosion inside the packaged system could affect the surrounding facilities. This proves that the standard for installing flame detectors, emergency shut down system and protection wall is appropriate.

• Journal of Korean Tunnelling and Underground Space Association
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• v.23 no.6
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• pp.535-547
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• 2021

A policy to expand the hydrogen economy has been established in Korea and the supply of FCEV is being expanded to realize a hydrogen society. Therefore, the supply of FCEV is expected to increase rapidly, and a solution to respond to accidents of FCEV is required. In this study, an experimental study was conducted to analyze the effect of the hydrogen jet flame generated by a FCEV on the inner wall of the tunnel and the characteristics of the internal radiant heat. For the experiment, the initial pressure of hydrogen tank was set to 700 bar, and the injection nozzle diameter was set to 1.8 mm in order to make the same as the conditions generated in the FCEV. In addition, a tunnel fire resistance test specimen having the same strength as the compressive strength of concrete applied to general tunnels of 40 MPa was manufactured and used in the experiment. The results were analyzed for the separation distance (2 m and 4 m) between the hydrogen release nozzle and the tunnel fire resistance test concrete. As the result, the maximum internal temperature of the test concrete was measured to 1,349.9℃ (2 m separation distance), and the radiant heat around the jet flame was up to 39.16 kW/m².

• Journal of the Korean Institute of Gas
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• v.16 no.6
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• pp.29-33
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• 2012

This paper is an attempt to give a concise overview of the state-of-the-art in the recent liquid hydrogen safety researches with unwanted event progress. The vessel of liquified hydrogen may fail and liquid hydrogen spilled. The hydrogen will immediately start to evaporate above a pool and make a hydrogen cloud. The cloud will disperse and can produce a vapor cloud explosion. The vessel containing the liquid hydrogen may not be able to cope with the boil-off due to heat influx, especially in case of a fire, and a BLEVE may occur. In equipment where it exists as compressed gas, a leak generates a jet of gas that can self-ignite immediately or after a short delay and produce a jet flame, or in case it ignites at a source a certain distance from the leak (delayed ignition), a flash fire occurs in the open and with confinement a deflagration or even detonation may develop. The up-to-date knowledge in these events, recent progress and future research are discussed in brief.

• Transactions of the Korean hydrogen and new energy society
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• v.25 no.6
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• pp.643-647
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• 2014

Two types of fuel supply method ar used in CNG vehicles. One is premixed ignition and the other is gas-jet ignition. In premixed ignition, the fuel is introduced with intake air so that homogeneous air-fuel mixture may form. The ignitability of this method depends on the global equivalence ratio. In gas-jet ignition, CNG is introduced directly into the engine combustion chamber. The overall mixture is stratified by retarded fuel injection. In this study, a visualization technique was employed to obtain fundamental properties regarding overall mixture formation of direct injected CNG fuel inside a constant volume chamber. Jet angles, penetrations and projected jet area with respect to ambient pressure are investigated. The penetration decreases apparently and the time reaching the CVC wall was delayed as the chamber pressure increases. This is caused by the higher inertia of the fluid elements that the injected fluid must accelerate and push aside. It is same to liquid fuel such as diesel and gasoline, but this phenomenon is far more prominent for the gaseous fuel.

• Journal of Korean Society for Atmospheric Environment
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• v.24 no.3
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• pp.329-335
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• 2008

Volatile organic compounds emitted to the atmosphere can cause adverse effects on human health and participate in photochemical smog formation reactions. The destruction of a series of VOCs has been carried out by non-thermal plasma in other researches. And the characteristic of non-thermal plasma was operated at atmospheric pressure and low temperature. A new type non-thermal plasma reactor was investigated combined Glidarc plasma with water jet in this research. Also, it was found that the water-jet had an significant effect on the toluene removal efficiency. But too much water content does not favor toluene decomposition by decreasing of reaction temperature. The input toluene concentration, gas flow rate, water flow rate and specific energy input were used as experiment variables. The toluene removal efficiency, energy efficiency and specific energy input were 75.3%, 146.6 g/kWh and $1.12kWh/m^3$ at a water flow rate of 100 mL/min.

• Journal of Korean Tunnelling and Underground Space Association
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• v.24 no.6
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• pp.659-677
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• 2022

Hydrogen is emerging as a next-generation energy source and development and supply of FCEV (hydrogen fuel cell electric vehicle) is expected to occur rapidly. Accordingly, measures to respond to hydrogen car accidents are required and researches on the safety of hydrogen cars are being actively conducted. In this study, In this study, we developed a hydrogen car accident scenarios suitable for domestic conditions for the safety evaluation of hydrogen car in road tunnels through analysis of existing experiments and research data and analyzed and presented the hazard distance according to the accident results of the hydrogen car accident scenarios. The accident results according to the hydrogen car accident scenario were classified into minor accidents, general fires, jet flames and explosions. The probability of occurrence of each accident results are predicted to be 93.06%, 1.83%, 2.25%, and 2.31%. In the case of applying the hydrogen tank specifications of FCEV developed in Korea, the hazard distance for explosion pressure (based on 16.5 kPa) is about 17.6 m, about 6 m for jet fire, up to 35 m for fireball in road tunnel with a standard cross section (72 m²).

• Journal of computational fluids engineering
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• v.15 no.2
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• pp.47-54
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• 2010

In the present study, a numerical simulation for the diffusion of hydrogen leakage of FCV(Fuel Cell Vehicle) in a tunnel was performed to aid the assessment of risk in case of leakage accident. The temporal and spatial distributions of the hydrogen concentration around FCV are predicted from the present numerical analyses. Flammable region of 4-74% and explosive region of 18-59% hydrogen by volume was identified from the present results. Factors influencing the diffusion of the hydrogen jet were examined to evaluate the effectiveness of tunnel ventilation system for relieving the accumulation of the leaked hydrogen gas. The distribution of the concentration of the leaked hydrogen for various cases can be used as a database in various applications for the hydrogen safety.

• Applied Chemistry for Engineering
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• v.19 no.1
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• pp.66-72
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• 2008

Manganese hydrogen phosphate hydrate, $MnHPO_4{\cdot}2.25H_2O$, is a major constituent of the pre-conditioning compositions for the manganese phosphate coating treatment over carbon steel substrate. This compound is conventionally produced by the synthesis in the aqueous solution process followed by the filtration and drying processes and a series of size reduction and classification processes in dry state. However, it is evident that the conventional process is neither environment-friendly nor cost-effective. In this work, a new process principle was examined based on the controlled double-jet precipitation technology to produce the manganese chemical product of fairly uniform particle size distribution in an aqueous solution media. The effects of stabilizing agents were comparatively studied by the scanning electron microscope analysis in a uniformity point of view of the resulting particle size. Polyvinylpyrrolidone and Gum Arabic were excellent in controlling the crystal growth step, resulting in fairly uniform size distributions of the particles from the controlled double-jet process.