TY - JOUR
T1 - Counterflow diffusion flames
T2 - effects of thermal expansion and non-unity Lewis numbers
AU - Koundinyan, Sushilkumar P.
AU - Matalon, Moshe
AU - Stewart, D. Scott
N1 - Funding Information:
This work has been supported by the Air Force Office of Scientific Research [Grant (AFOSR/RTA) FA9550-17-1-0223], and its predecessor [Grant FA9550-14-1-0091], Dr Mitat Birkan, Program Manager; SK was also supported by the Department of Defense SMART Scholarship program.
Publisher Copyright:
© 2018 Informa UK Limited, trading as Taylor & Francis Group.
PY - 2018/5/4
Y1 - 2018/5/4
N2 - 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.
AB - 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.
KW - counterflow diffusion flames
KW - extinction
KW - flow displacement
KW - large activation energy asymptotics
KW - thermal expansion
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U2 - 10.1080/13647830.2018.1441444
DO - 10.1080/13647830.2018.1441444
M3 - Article
AN - SCOPUS:85045116793
SN - 1364-7830
VL - 22
SP - 585
EP - 612
JO - Combustion Theory and Modelling
JF - Combustion Theory and Modelling
IS - 3
ER -