Flame behavior in heated porous sand bed

Abstract This paper reports experimental and numerical investigations on the combustion characteristics of a lean methane–air mixture in a heated porous sand bed. The porous bed consisted of sand (SiO 2 ) particles with a mean particle diameter of 0.56 mm. The horizontally placed quartz tube was heated externally to initiate the combustion reaction in the porous bed combustor. The stabilized flame location curve as a function of averaged mixture velocity was obtained for various equivalence ratios. Contrary to the earlier finding of a C-shape flame stabilization behavior, a new S-shape behavior was observed in the present study. This can be divided into three regimes: high, moderate, and low velocity regimes. In the low velocity regime, flame with very weak luminosity was confirmed and the stabilized flame location moved downstream with the increase of the mixture velocity. For the moderate velocity regime, a stable flat flame was observed and the flame location moved upstream with the increase of the mixture velocity. An oscillatory flame behavior was observed in the high velocity regime. In this oscillatory mode, the flame front oscillated with a characteristic time period of the order on 1 h and increased with the increase of the mixture velocity. In order to further understand these experimental results, one-dimensional computational studies with detailed chemistry and heat transfer mechanisms were carried out. The computational results were in good agreement with experimental observations. The computations showed that solid-to-solid radiation played a significant role in the flame stabilized location. From the examination of the flame structure, it was found that the flame behavior in the low velocity regime was similar to that of the flameless combustion mode.

[1]  C. J. Butler,et al.  The production of nitric oxide during the combustion of methane and air in a fluidized bed , 2001 .

[2]  R. Peck,et al.  Flame Stabilization and Multimode Heat Transfer in Inert Porous Media: A Numerical Study , 1990 .

[3]  A. A. Korzhavin,et al.  Propagation of premixed gaseous explosion flames in porous media , 1991 .

[4]  Shigeru Tada,et al.  Experimental study on combustion in porous media with a reciprocating flow system , 1997 .

[5]  A. Barra,et al.  Heat recirculation and heat transfer in porous burners , 2004 .

[6]  Sejin Kwon,et al.  Effects of thermal and chemical surface–flame interaction on flame quenching , 2006 .

[7]  Yoshizawa Yoshio,et al.  Analytical study of the structure of radiation controlled flame , 1988 .

[8]  Jay P. Gore,et al.  A study of the structure of submerged reaction zone in porous ceramic radiant burners , 1997 .

[9]  J. S. Dennis,et al.  The ignition and combustion of propane/air mixtures in a fluidised bed , 1982 .

[10]  R. R. Baldwin,et al.  Oxidation of propionaldehyde in aged boric-acid-coated vessels. Part 1.—Kinetic results , 1969 .

[11]  T. Takeno,et al.  An excess enthalpy flame combustor for extended flow ranges , 1985 .

[12]  Paul D. Ronney,et al.  Gas-phase and catalytic combustion in heat-recirculating burners , 2004 .

[13]  Alexei V. Saveliev,et al.  Structures of multiple combustion waves formed under filtration of lean hydrogen-air mixtures in a packed bed , 1996 .

[14]  L. Kennedy,et al.  Superadiabatic combustion of methane air mixtures under filtration in a packed bed , 1995 .

[15]  M. Modest.  Radiative heat transfer , 1993 .

[16]  J. Ellzey,et al.  Modeling of filtration combustion in a packed bed , 1999 .

[17]  S. Minaev,et al.  Combustion wave instability in the filtration combustion of gases , 1994 .

[18]  Witold Żukowski,et al.  Combustion of hydrocarbon fuels in a bubbling fluidized bed , 2002 .

[19]  Mitchell D. Smooke,et al.  Solution of burner-stabilized premixed laminar flames by boundary value methods , 1982 .

[20]  Anthony G. Dixon,et al.  Theoretical prediction of effective heat transfer parameters in packed beds , 1979 .

[21]  K. Maruta,et al.  Reaction zone structure in flameless combustion , 2000 .

[22]  P. Agarwal,et al.  Combustion of isolated bubbles in an elevated-temperature fluidized bed , 2005 .

[23]  Takuya Kataoka,et al.  Characteristics of combustion in a narrow channel with a temperature gradient , 2005 .

[24]  N. V. Pavlyukevich,et al.  Modeling of premixed gas combustion in porous media composed of Coarse-Sized particles: 1-D description with discrete solid phase , 1996 .

[25]  A. Bejan,et al.  Convection in Porous Media , 1992 .

[26]  Tadao Takeno,et al.  An Excess Enthalpy Flame Theory , 1979 .