• Journal of Advanced Marine Engineering and Technology
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• 제28권4호
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• pp.632-640
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• 2004

The purpose of this study is to clarify the influence of inert gas on the configuration characteristics of premixed turbulent propagating flames of hydrogen mixtures. Inert gas is changed to $N_2$, Ar, $CO_2$ and He keeping the laminar burning velocity of mixtures nearly the same value. A laser tomography technique was used to obtain the flame shape, and quantitative analyses were performed. The result shows that in the wrinkled laminar flame region, the surface area of turbulent flame is slightly dependent on the equivalence ratio and the kind of inert gas. It is also shown the region of convex part of flame toward the unburned gas is greater than that of toward the burned gas regardless of the kind of inert gas.

• 한국화재소방학회논문지
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• 제16권3호
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• pp.77-83
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• 2002

질소, 아르곤, 이산화탄소와 같은 불활성가스 및 이들의 혼합물을 소화약제로 하여 n-Heptane을 연료로한 cup-burner test 장치에서 불꽃소화농도와 연소시 배가스의 조성을 측정하였다. 이성분 불활성가스계 혼합소화약제의 소화농도는 혼합물의 구성비를 이용한 모델에 의해 잘 예측됨을 알 수 있었다. 불활성 가스계 혼합 소화약제에 의한 소화작용에 있어서 혼합가스의 평균비중이 클수록 소화 성능이 우수하였다. 또한 밀폐된 공간의 구조가 소화에 영향을 미칠 수 있음을 확인하였다. 연소시 배가스 중 이산화탄소 조성은 사용하는 소화약제의 양이 증가할수록 감소하였다. 일산화질소 발생은 소화약제의 질소 함량과는 상관이 없으며 공기유량을 크게 하여 불꽃을 크게 했을 때 검출되었다.

• 한국화재소방학회논문지
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• 제17권2호
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• pp.43-49
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• 2003

대체 소화제로 사용되는 불활성 기체 중 Ar, $N_2$, $CO_2$에 대한 혼합물에서의 물성(포화압력, 밀도, 점도)에 관한 실험식을 구하였다. Mixing rule에 의해 계산한 값을 이용하여 다항식 등의 회귀분석에 의해서 실험식을 얻었다. 포화압력은 온도에 대하여 1차 실험식으로 표시하였다. 압축인자와 포화압력을 이용하여 온도에 대한 밀도에 관한 실험식을 제시하였다. 점도는 온도에 대한 지수함수로 표시하였다. Ar, $N_2$, $CO_2$혼합물의 조성이 40/50/10(mol. %)에서 열역학적 실험식을 구하였다.

• 한국화재소방학회논문지
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• 제18권1호
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• pp.7-12
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• 2004

몬트리올 의정서에 의해서 규제 받는 CFCs와 Halon의 대체 물질인 HFC-23, HFC-125, HFC-227ea, HFC-236fa와 불활성 화합물 $Ar, N_2, CO_2$의 열역학적 물성인 포화압력, 밀도, 엔탈피, 점도를 비교하였다. 본 연구에서는 소화제의 물성을 문헌 값을 온도의 함수로서 표시하였다. HFC 화합물의 열역학적 물성은 Halon-1301과 비슷하게 나타내었다. 불활성 화합물은 주로 혼합물로 이용되지만, 불활성 화합물의 물성은 Halon-1301에 비하여 바람직하지 않았다.

• 한국안전학회지
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• 제23권6호
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• pp.76-83
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• 2008

In the course of increasing in human and material damage caused by fire, it is an important research field to develop clean extinguishing agent which does no harm to global environment as well as has a good extinguishing efficiency. This research is a basic step to develop a new clean extinguishing agent. In order to get a satisfactory result, we tested fire extinguishing ability using nitrogen and Novec mixtures gas which are inert gas and new clean extinguishing agent. We used Cup Burner Test made by international standard ISO-14520 regulations of gaseous extinguishing agent ability test, and the fuels used in the test are n-heptane, methanol, ethanol, iso-propanol and 1-butanol. The experimental results of flame extinguishing concentration are n-heptane 6.54%, methanol 8.47%, ethanol 6.98%, isopropanol 6.10% and butanol 6.54% by pure Novec agent. So the finding is that a new clean agent, Novec has an efficient extinguishing ability in a state of gas. Also, in a test as to mixtures gas of nitrogen and Novec, it has a good result for minimum oxygen concentration is under 16%.

• Macromolecular Research
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• 제15권4호
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• pp.343-347
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• 2007

Novel composite membranes, which delivered high separation performance for propylene/propane mixtures, were developed by coating inert poly(ethylene-co-propylene) rubber (EPR) onto a porous polyester substrate, followed by the physical distribution of $AgBF_4$. Scanning electron microscopy-wavelength dispersive spectrometer (SEM-WDS) revealed that silver salts were uniformly distributed in the EPR layer. The physical dispersion of the silver salts in the inert polymer matrix, without specific interaction, was characterized by FT-IR and FT-Raman spectroscopy. The high separation performance was presumed to stem from the in-situ dissolution of crystalline silver ionic aggregates into free silver ions, which acted as an active propylene carrier within a propylene environment, leading to facilitated propylene transport through the membranes. The membranes were functional at all silver loading levels, exhibiting an unusually low threshold carrier concentration (less than 0.06 of silver weight fraction). The separation properties of these membranes, i.e. the mixed gas selectivity of propylene/propane ${\sim}55$ and mixed gas permeance ${\sim}7$ GPU, were stable for several days.

• 한국분말재료학회지
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• 제9권6호
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• pp.416-421
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• 2002

Elemental powders are used in high energy milling processes for the synthesis of new compounds. The low temperature solid state reactions during milling in inert gas atmosphere may result in intermetallic phases, carbides, nitrides or silicides with a nanocrystalline structure. To obtain dense materials from the powders a pressure assisted densification is necessary. On the other side the defect-rich microstructure can be used for activated sintering of elemental powder mixtures to obtain dense bodies by pressureless sintering. Results are discussed for nanocrystalline cermet systems and for the sintering of aluminides and silicides.

• Journal of Advanced Marine Engineering and Technology
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• 제23권3호
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• pp.300-310
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• 1999

A constant-volume combustion chamber is developed to measure the burnt gas temperature over the wide ranges of equivalence ratio from 1.5 to 2.7 and pressure from 0.1 to 2.7 and pressure from 0.1 to 6 MPa by two-color method. The combustion temperature is also calculated by the conventional two-region model. The premixed fuel rich propane-oxygen-inert gas mixtures under high pressures are simultaneously ignited by eight spark plugs located on the circumference of combustion chamber with 45 degree intervals. The eight converging flames compress the end gases to high pressures. The transmissiv-ity in the chamber center during the final stage of combustion at the highest pressure is measured by in situ laser extinction method. Comparisons are made with the combustion temperatures between two-color method and two-region model. It is found that the burnt gas temperature mea-sured by two-color method is higher than that calculated by two-region model because of being the negative temperature gradient on the calculation and the temperature distribution of light path-length on the measurement and the burnt gas temperature for the turbulent combustion is higher than that of the laminar combustion under the same conditions because the heat loss for turbulent combustion is lower due to the shorter combustion period.

• 한국전기전자재료학회논문지
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• 제20권4호
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• pp.381-387
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• 2007

The excellent dielectric properties of $SF_6$(sulfur hexafluoride) have lead to its wide range of application in the field of high voltage insulation. Because there has been some recent concern regarding the environmental impacts of $SF_6$ binary gas mixtures, with $SF_6$ as the main component, have been the subject of active research. Scientists have long been interested in the possible use of gaseous fluorocarbons, including $CF_4$ (Carton Tetrafluoride), in high voltage applications due to their inert character and high dielectric strength. This paper presents experimental results concerning the AC breakdown characteristics lot various mixtures of $SF_6/CF_4$ in a test chamber and 25.8 kV GIS (Gas Insulation Switchgear) at practical pressures (0.1-04 MPa) and gap lengths (0.5 mm, 1 mm) in a test chamber. In the result, it was observed that an increase in the dielectric strength is attained through the addition of $SF_6$ to $CF_4$. It is possible to make an environment friendly gas insulation material while maintaining the dielectric strength by combing $SF_6$ and $CF_4$ which generates a lower level of the "global warming" effect.

• 한국안전학회지
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• 제37권6호
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• pp.18-24
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• 2022

Hydrogen is a clean fuel and is used in many applications in power systems such as fuel cells. It has unique properties such as wide flammability, high burning velocity, and difficulty to liquefy, which lead to critical safety issues. Fire and explosion are the most frequently occurring accidents and one of the major reasons is autoignition. In the ignition process, the chemistry of hydrogen combustion depends mainly on radical pools, and the temperature at which chain-branching and terminating rates are equal is called the crossover temperature. This study addresses the homogeneous autoignition of diluted hydrogen-air mixtures to investigate the effects of dilution on the crossover temperature to prevent explosions in the future. The new criterion for crossover temperature is introduced by only hydrogen radicals to adjust more simply. The detailed calculations indicate that the crossover temperatures are low at high dilutions of carbon dioxide and nitrogen because the concentrations of active radicals are reduced when an inert gas is added. This result is expected to contribute to hydrogen safety and realize a hydrogen society in the future.