• Title/Summary/Keyword: minimum extinguishing concentration

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Flame- Extinguishing Concentrations of Inert Gases in Jet Diffusion Flames (제트확산화염에서의 불활성기체 소화농도)

  • Ji, Jung-Hoon;Lee, Eui-Ju
    • Journal of the Korean Society of Safety
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    • v.24 no.1
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    • pp.21-25
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    • 2009
  • Extinguishing limits of laminar ethylene/oxygen flames in both normal and inverse co-flow jet burner have been determined experimentally and computationally. An inert gas($N_2$, Ar, $CO_2$) was added into the oxidizer to find the critical concentration and the effectiveness of the agents on flame extinction. The experimental results showed that the physical aspect of inert gases was main mechanism for flame blow-out as same as cup burner test, but the flow effect should be considered to determine the extinction concentration. The numerical prediction was performed with modified WSR model and the result was in good agreement with the measurements. The experimental and numerical methods could be used for the assessment of various flame suppression agents such as minimum extinguishing concentration.

Extinguishing Concentration of Inert Gases in Heptane Pool Fires (헵탄 풀화재에서 불활성기체 소화농도)

  • Jung, Tae-Hee;Lee, Eui-Ju
    • Journal of the Korean Society of Safety
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    • v.27 no.3
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    • pp.71-76
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    • 2012
  • The coflow velocity effect on the minimum extinguishing concentration(MEC) was investigated experimentally in heptane cup-burner flames. Various inert gases($N_2$, Ar, $CO_2$, He) were added into the oxidizer to find the critical concentration and the effectiveness of the agents on flame extinction. The experimental results showed that the MECs were increased with increasing coflow velocity for most inert gases except helium, but the higher coflow velocity induced the lower burning rates of heptane. This indicated that the increase of coflow velocity resulted in the decrease of fuel velocity evaporated from fuel surface, and hence the stain rate on the reaction zone was also decreased. In the case of helium as a additive, the extinguishing concentration was independent of the coflow velocity because the heat conductivity was ten times larger than the other inert gases and flow effect by a strain rate might be compensated for heat loss to the surroundings.

A Study on the Measurement of Flame Extinguishing Concentration of Halon Alternatives by New Test Equipment (할론대체물질의 새로운 불꽃소화농도 측정장치에 관한 연구)

  • 김재덕;임종성;이윤우;이윤용
    • Fire Science and Engineering
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    • v.8 no.1
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    • pp.3-8
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    • 1994
  • A new test system was established to measure the flame extinguishing concentration of Halon alternatives. The main characteristic of this system is to use the solid paraffin with a wick instead of liquid fuel, such as n-Heptane. Our results showed that the extinguishing concentration of compounds was lower than that of other existing data, but the trend was consistent with others. The flame extinguishing concentration of all tested compounds were not almost effected by gas flow velocity. The system produces good reliable data with a minimum error for measuring the flame extinguishing concentration. Therefore our new system can be utilized as a standard equipment to evaluate Halon alternatives.

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A Study on Clean Agent Fire Extinguishing Ability Using Nitrogen and Novec Mixtures Gas (질소와 노벡 혼합가스를 이용한 청정소화약제의 소화성능에 관한 연구)

  • Lim, Woo-Sub;Jung, Jong-Jin;Nam, Dong-gun;SaKong, Seong-Ho;Kim, Jong-Won;Choi, Kenu-Joo
    • Journal of the Korean Society of Safety
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    • v.23 no.6
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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%.

Unsteady Flow Effects on Extinguishing Concentrations in Jet Diffusion Flames (제트확산화염 소화농도의 비정상 유동효과)

  • Ji, Jung-Hoon;Oh, Chang-Bo;Lee, Eui-Ju
    • Journal of the Korean Society of Safety
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    • v.24 no.6
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    • pp.27-31
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    • 2009
  • An experimental study on the unsteady effect of the extinction limit was performed in ethene jet diffusion flames. To impose the unsteadiness on jet flames, the amplitude and frequency of a co-flow velocity was varied, and the two inert gases, $N_2$ and $CO_2$, were used to dilute the oxidizer for extinguishing concentration. The experimental results shows that large amplitude of velocity induces a low extinguishing concentration, which implies that flow variation affects the blow out mechanism. Also, the flow oscillation effects under high frequency attenuates the flame extinction. These results means that flow unsteadiness extends the extinction limit and finally minimum extinction concentration by inert gases. When the Stoke's 2nd Problem is introduced to explain the flow unsteadiness on extinction concentration, the solution predicts the effect of amplitude and frequency of velocity well, and hence it is concluded the effect of low frequency velocity excitation was attributed only to flow effect.