Large Activation Energy Analysis of Nonadiabatic Strained Premixed Laminar Flames with Nonunity Lewis Numbers Articles uri icon

publication date

  • March 2023

start page

  • 3707

end page

  • 3752

issue

  • 15

volume

  • 195

International Standard Serial Number (ISSN)

  • 0010-2202

Electronic International Standard Serial Number (EISSN)

  • 1563-521X

abstract

  • We present an asymptotic analysis of a strained premixed flame in the mixing layer between two counterflowing streams: one with fresh reactants at a temperature Tu and other with the burned gases at temperature Tb , which may be different from the adiabatic combustion temperature Te....Tu of the fresh gases. A one-step irreversible Arrhenius reaction model, of high activation energy, is used for the asymptotic analysis, together with the thermal-diffusive approximation of constant density and transport properties - easily generalized to variable density and transport properties with the use of a heat-conduction-weighted coordinate. The analysis for near unity Lewis numbers of the fuel by Libby, Liñán and Williams (1983) is extended here to arbitrary nonunity Lewis numbers, of relevance to a wide variety of applications, ranging from hydrogen-fueled combustors to heavy fuel systems. In analogy with Liñán's analysis of counterflow diffusion flames, three asymptotic distinguished regimes are identified for premixed flames for large activation energies and the appropriate Damköhler numbers - the ratio of the characteristic diffusion and reaction times. These regimes are the premixed flame regime, the partial burning regime and the nearly frozen ignition regime. The analytical expressions obtained for these regimes, of the dimensionless reaction rate as a function of the Damköhler number, are seen to describe with good accuracy the results obtained from the numerical integration of the full problem.

subjects

  • Industrial Engineering

keywords

  • activation energy asymptotics; counterflow premixed flames; nonadiabatic; nonunity lewis number; extinction and ignition; flamelet regimes