Effects of different kinds of fuel and fuel equivalence ratio on flame structure of triple flame

Hiroshi Yamashita, Nobuyuki Kawahara, Nag Jung Choi

Research output: Contribution to journalArticle

5 Citations (Scopus)

Abstract

In order to clarify the effects of different kinds of fuel and fuel equivalence ratio on flame structure, a numerical simulation of triple flame developed in a co-flowing methane-air or hydrogen-air mixture and air stream was made taking into account the elementary chemical reaction mechanism. The following conclusions were reached: (1)The relation between the apparent burning velocity of the triple flame and the fuel equivalence ratio shows a similar tendency to that of the one-dimensional premixed flame of the corresponding fuel. However, the fuel equivalence ratio at which the apparent burning velocity is the largest is a little larger than that of the one-dimensional premixed flame. The apparent burning velocities are two and three times higher than that of the one-dimensional premixed flame for the methane-air or hydrogen-air mixture. ( 2 )The flame thrusts out forward in the downstream of the boundary between mixture and air stream, and a part of the flow is bent and forks out in this protruding flame so that a triple flame is originated ; this triple flame is composed of fuel rich and lean premixed flame branches and a diffusion flame branch. The change in shape of the convex part, caused by the effect of the one-dimensional premixed flame, is further promoted by the effect of hydrodynamic instability originated in the expansion brought about by heat release. A considerably strong diffusion flame branch exists almost in the center of the two premixed flame branches for the methane-air mixture, while a considerably weak diffusion flame branch approaches the fuel lean premixed flame branch for the hydrogen-air mixture. ( 3 )Near the fuel equivalence ratio at which the burning velocity of the one-dimensional premixed flame is the largest, the effect of the one-dimensional premixed flame becomes large and the fuel rich premixed flame advances and becomes vertical to the flow direction. As a result, the effect of hydrodynamic instability is weakened. Thus, both of these effects demonstrate that the fuel equivalence ratio at which the apparent burning velocity is the largest is a little larger than that of the one-dimensional premixed flame.

Original languageEnglish
Pages (from-to)775-782
Number of pages8
JournalNihon Kikai Gakkai Ronbunshu, B Hen/Transactions of the Japan Society of Mechanical Engineers, Part B
Volume65
Issue number630
DOIs
Publication statusPublished - Jan 1 1999
Externally publishedYes

Keywords

  • Burning velocity
  • CH
  • Combustion phenomena
  • Flame structure
  • Fuel equivalence ratio
  • H
  • Kinetics
  • Numerical analysis
  • Triple flame

ASJC Scopus subject areas

  • Condensed Matter Physics
  • Mechanical Engineering

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