Unsteady Flow Effects on Extinguishing Concentrations in Jet Diffusion Flames

제트확산화염 소화농도의 비정상 유동효과

  • Ji, Jung-Hoon (Division of Safety Engineering, Pukyong National University) ;
  • Oh, Chang-Bo (Division of Safety Engineering, Pukyong National University) ;
  • Lee, Eui-Ju (Division of Safety Engineering, Pukyong National University)
  • 지정훈 (부경대학교 안전공학부) ;
  • 오창보 (부경대학교 안전공학부) ;
  • 이의주 (부경대학교 안전공학부)
  • Published : 2009.12.31

Abstract

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.

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