Asymptotic analysis of stationary adiabatic premixed flames in porous inert media

Journal Article · Sat Nov 15 00:00:00 EST 2008 · Combustion and Flame

DOI:https://doi.org/10.1016/J.COMBUSTFLAME.2008.08.003· OSTI ID:21116123

Pereira, Fernando M; Oliveira, Amir A.M. ^[1]; Fachini, Fernando F ^[2]

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1. Departamento de Engenharia Mecanica, Universidade Federal de Santa Catarina, 88040-900 Florianopolis, SC (Brazil)
2. Instituto Nacional de Pesquisas Espaciais, 12630-000 Cachoeira Paulista, SP (Brazil)

The structure of adiabatic premixed flames within porous inert media is investigated using the asymptotic expansion method. For this, the flame structure is divided into three characteristic length scales. The two innermost length scales, the gas-phase diffusion length scale and the reaction length scale, are the same scales defined in the classical premixed flame structure analysis. The outermost length scale, the solid-phase diffusion length scale, is related to the heat conduction in the porous matrix. The differences among these three characteristic length-scales result in large temperature differences between the phases and justify the application of asymptotic expansions to determine an approximate (analytical) solution. Since the main focus of this work is the examination of the processes in the outer and the first inner regions, the simplest kinetic mechanism of one global step is adopted to represent the fuel and oxygen consumption. Then, the description of the reaction zone is obtained using the large activation energy asymptotic method. The description of the problem of the order of the gas-phase length scale is obtained using the boundary layer expansion. This work evaluates the influence of the equivalence ratio, the ratio of the solid to the gas thermal conductivities, the porosity of the medium and the fuel Lewis number on such flames. A parameter that universalizes the flame properties is then identified and discussed. (author)

• OSTI ID: 21116123
• Journal Information: Combustion and Flame, Vol. 155, Issue 3; Other Information: Elsevier Ltd. All rights reserved; ISSN 0010-2180
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
DIFFUSION LENGTH
ASYMPTOTIC SOLUTIONS
POROUS MATERIALS
FLAMES
SERIES EXPANSION
THERMAL CONDUCTION
THERMAL CONDUCTIVITY
COMBUSTION
ACTIVATION ENERGY
ANALYTICAL SOLUTION
BOUNDARY LAYERS
LEWIS NUMBER
SOLIDS
GASES
POROSITY
ZONES
Superadiabatic temperature