• Journal of the Korea Safety Management & Science
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• v.24 no.4
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• pp.101-107
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• 2022

To test a flameproof enclosure for the safety certificate, a reference pressure of explosion needs to be determined. However, the explosion pressure may be changed according to relative humidity of explosive gases. Therefore, the guideline on relative humidity should be recommended for measuring the explosion pressure for accurate and reproducible testings. This study examined the relationship of explosion pressure with relative humidity of hydrogen (31 vol %)-air and acetylene (14 vol %)-air mixture gases. The explosion pressures were measured by increasing the relative humidity of the gases by 10 % from dry state to 80 % in a cylindrical explosion enclosure of 2.3 L. on ambient temperature and atmospheric pressure (1 atm). The maximum explosive pressures were remained almost constant until the relative humidity reached 10 % for the hydrogen-air mixture and 20 % for the acetylene-air mixture. However, the maximum explosive pressures linearly decreased as the relative humidity increased. Based on the results of the study, it would be recommended to use 10 % relative humidity for the hydrogen-air mixture and 20 % for the acetylene-air mixture as the critical value in testing a flameproof enclosure.

• Journal of Ship and Ocean Technology
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• v.9 no.1
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• pp.38-46
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• 2005

Survivability improvement method for naval ship design has been continually developed. In order to design naval ships considering survivability, it is demanded that designers should establish reasonable damage conditions by air explosion. Explosion may induce local damage as well as global collapse to the ship. Therefore possible damage conditions should be realistically estimated in the design stage. In this study the authors used ALE technique, one of the structure-fluid interaction techniques, to simulate air explosion and investigated survival capability of damaged naval ships. Lagrangian-Eulerian coupling algorithm, equation of the state for explosive and air, and simple calculation method for explosive loading were also reviewed. It is shown that air explosion analysis using ALE technique can evaluate structural damage after being attacked. This procedure can be applied to the real structural design quantitatively by calculating surviving time and probability.

• Journal of the Korea Safety Management & Science
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• v.25 no.1
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• pp.51-58
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• 2023

Determination of explosion reference pressure is important in designing and testing flameproof enclosures (Ex d). Although relative humidity affects to explosion pressure, its effect is not well investigated for the gas group IIB, IIA, and I. This study tested explosion pressure for Ethylene (8 vol.%), Propane (4.6 vol.%), and Methane (9.8 vol.%), which are the representative gas of the gas group IIB, IIA, and I, at ambient temperature and atmospheric pressure (1 atm) under different relative humidity (0% ~ 80%). Ethylene- and Propane-air mixed gases generally tended to decrease as the relative humidity increased; however, explosion pressure was largely dropped at 20% of relative humidity compared to 0% and 10% of relative humidity. On the other hand, Methane-air mixture gas showed similar pressures at 0% and 10% of relative humidity; but no explosion occurred at more than 20%. The results of this study can be used in setting a testing protocol of explosion reference pressure for designing and testing a flameproof enclosure.

• Proceedings of the Safety Management and Science Conference
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• 2001.05a
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• pp.301-310
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• 2001

A study for the dangerous properties measurment of dust explosion was attended by the various dust concentration on Anthraquinone, Sodiumbenzoic acid, Corn starch, soy sauce powder, and cheese powder. As the result, maximum explosion pressure, the maximum rate of pressure rise, autoigntion temperature, and the water content of dust on lower limit explosion concentration was obtained as follows 1. The lower limit explosion concentration on soy sauce powder with the humidity of 65 to 90% increased by increasing the con tent of moisture, and the effect of dry air and moisture air decreased better in make of dry air. 2. The effect of a various dust concentration on autoigntion temperatures is investigated, If the vessel of dust explosion is small size and the easiness of autoignition was controled by air within the vessel, because it was better decreased air with increasing of dust concentration 3. The maximum explosion pressures of Anthraguinone, sodiumbenzoic acid, com starch, soy sauce powder, and cheese powder were 1.0g/$\ell$, 1.0g/$\ell$, 1.5g/$\ell$, 1.5g/$\ell$, and 1.5g/$\ell$, respectively, and the maximum rate of pressure rise were 0.5g/$\ell$, 0.5g/$\ell$, 1.0g/$\ell$, 1.0g/$\ell$, and 1.0g/$\ell$, respectively.

• Journal of the Korean Society of Safety
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• v.7 no.3
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• pp.66-72
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• 1992

An experimental study was carried out to analyse the explosion characteristics of flammable gas-air mixtures. Used flammable gases were hydrogen, methane, acethylene, ethylene and pro-pane, explosion Pressure, explosoin pressure rising rate, and flame propagation velocity were measured experimentaly. The maximum explosion pressure and rising rate of flammmalbe gas air mixtures were appeared at the range of slightly higher concentration than the stoichiometric concentration. Initial pressure before explosion was controlled from 0.6 to 2.0kg/cm absolutly. Explosion pressure was increased with increment of the initial pressure, and the relationship between initial pressure and explosion pressure was Pe = KPi. The effect of vessel size on explosion characteristics was also analysed In this experiment. Explosion pressure was increased with in-creasing the vessel size, otherwise explosion pressure rising rate was decreased. When we locate a dummy material in vessel explosion pressure was decreased with increasing the dummy volume but exlosion pressure rising rate was increased.

• Journal of the Korean Society of Safety
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• v.8 no.4
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• pp.114-119
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• 1993

The explosion characteristics of nonhomogeneous LPG-Air mixtures was measured in a cylindrical vessel and a pipe. The maximum explosion pressure, the maximum rate of explosion pressure rise, and the flame propagation velocity were measured and compared with that of homogeneous explosion by changing the effective factors on the explosion of nonhomogeneous mixtures such as pressure difference, effusion time and delay time. Explosion was occured even in the lower concentration than the lean flammability limit of mixture. The maximum explosion pressure was increased with increase of LPG concentration, however, the maximum explosion pressure rise was not in the nonhomogeneous explosion. An d the flame propagation velocity was decreased with nonhomogeneity, however, the maximum explosion pressure was always above 0.7kg/$\textrm{cm}^2$.

• Journal of the Korean Society of Safety
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• v.8 no.4
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• pp.107-113
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• 1993

Small rectangular explosion chamber of its size 25cmX25cmX32cm with a circular bursting diaphram at the top was used to study the mechanism of gas explosion to fire transition phenomena, the process of ignition of solid combustibles during a gas explosion. To visulize the explosion to fire transition phenomena, transparent acryl window and high speed camera system were used. The test piece of solid combustible in this experiments was a 5cm$\times$5cm square sheet of newspaper which was placed in the explosion chamber filled with a LPG-air mixture. The mixture was ignited by an electric spark at the center of the chamber. Explosion to fire transition phenomena and the behavior of out flow and in flow of gas through the opening yielded by bursting the diaphram was visualized with shlieren system and without shlieren system. Diameter of a bursting dlaphram at the top of the explosion chamber was varied 5cm, 10cm, and 15cm, and the position of test piece were varied with 6 point. Explosion pressure was measured with strain type pressure transducer, and the weight difference of the test piece before and after each experimental run was measured. By comparing the weight difference of solid combustibles before and after the experiment and the behavior of out flow and inflow of gas after explosion, it was found that the possibility of ignition was depends on the LPG-air mixture concentration and the exposure period of test piece to the burnt gas. Test result of this experiments it was found that the main factor of this phenomena are that heat transfer to the test piece, and the pyrolysis reaction of test piece. Based on the results, the mechanism of the explosion to fire transition phenomena were inferred ; gas explosion- heat transfer to solid combustibiles ; pyrolysis reaction of solid combutibles : air inflow ; mixing of the pyroly gas with air ignition.

• Proceedings of the KSME Conference
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• 2002.08a
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• pp.397-400
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• 2002

Vapor explosion is one of the most important problems encountered in severe accident management of nuclear power plants. In spite of many efforts, a lot of questions still remain. So, KAERI launched a real experimental program called TROI using $UO_{2}$ and $ZrO_{2}$ to investigate the vapor explosion. Besides TROI tests, a small-scale experiment with molten-tin/water system was performed to quantify the characteristics of vapor explosion and to understand the phenomenology of vapor explosion. A vapor explosion was observed while the amount of air bubble and water temperature were systematically varied The mass and temperature of tin are $50\;g\;and\;150^{\circ}C$, respectively. Water temperature is set to $24^{\circ}C\;and\;50^{\circ}C$. The void fraction of air bubble ranges from $0\;to\;10\;{\%}$. The strength of vapor explosion was measured using dynamic pressure sensors attached in reactor tube wall. as a function of void fraction. In addition, a high speed video filming up to 1,000 flame/sec was taken in order to visually investigate the behavior of the vapor explosion .

• Journal of the Korea Safety Management & Science
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• v.12 no.2
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• pp.75-82
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• 2010

Gas turbines for power generating operate in a very high temperature condition and use natural gas for fuel. For this reason, many cases of damage happen at hot gas parts which are severely affected by high temperature gas and many cases of explosion occur by fuel gas. So a lot of efforts should be made to prevent hot gas parts damage and gas explosion accidents. Though there are many damage cases and explosion accidents, it is very difficult to find out the root causes of hot gas parts damage caused by gas explosion due to gas leakage in the heat exchanger for air cooling and gas heating. To prevent gas turbine from damage caused by gas explosion, removal of leakage gas from gas turbine is inevitably required before firing the gas turbine and installing alarm systems is also required for detecting gas leakage at stop valve to turbine while shut down.

• Explosives and Blasting
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• v.35 no.3
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• pp.21-30
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• 2017

When explosives explode in water, the effect of post-explosion gas after explosion should be considered, unlike explosion in the air. During explosion in water, the propagation velocity of the explosion pressure is faster than when the explosion occurs in the air. The generated gas is diffused and trapped in the form of bubbles by water before the energy is dissipated. At this time, the bubble expands and contracts, creating a shock wave. In order to investigate this series of phenomena, a cylinder type steel water tank capable of observing the interior was fabricated and explosion experiments were conducted. In this study, a small amount of shell-free pentolite was exploded in water. Experiments were performed to observe the behavior of the generated gas bubble as well as to measure the shock wave generated. We designed the experimental method of underwater explosion and examined the results.