Counterflow diffusion flames: effects of thermal expansion and non-unity Lewis numbers

Sushilkumar P. Koundinyan, Moshe Matalon, D. Scott Stewart

Research output: Contribution to journalArticlepeer-review


In this work we re-examine the counterflow diffusion flame problem focusing in particular on the flame–flow interactions due to thermal expansion and its influence on various flame properties such as flame location, flame temperature, reactant leakage and extinction conditions. The analysis follows two different procedures: an asymptotic approximation for large activation energy chemical reactions, and a direct numerical approach. The asymptotic treatment follows the general theory of Cheatham and Matalon, which consists of a free-boundary problem with jump conditions across the surface representing the reaction sheet, and is well suited for variable-density flows and for mixtures with non-unity and distinct Lewis numbers for the fuel and oxidiser. Due to density variations, the species and energy transport equations are coupled to the Navier–Stokes equations and the problem does not possess an analytical solution. We thus propose and implement a methodology for solving the free-boundary problem numerically. Results based on the asymptotic approximation are then verified against those obtained from the ‘exact’ numerical integration of the governing equations, comparing predictions of the various flame properties.

Original languageEnglish (US)
Pages (from-to)585-612
Number of pages28
JournalCombustion Theory and Modelling
Issue number3
StatePublished - May 4 2018


  • counterflow diffusion flames
  • extinction
  • flow displacement
  • large activation energy asymptotics
  • thermal expansion

ASJC Scopus subject areas

  • General Chemistry
  • General Chemical Engineering
  • Modeling and Simulation
  • Fuel Technology
  • Energy Engineering and Power Technology
  • General Physics and Astronomy


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