Investigation of soot formation and temperature field in laminar diffusion flames of LPG–air mixture

Abstract Soot formation and burnout were studied at atmospheric pressure in co-flowing, axisymmetric, buoyant laminar diffusion flames and double flames of liquefied petroleum gases (LPG)–air mixtures. In diffusion flames, two different fuel flow rates were examined. In double flames, three different primary air flow rates were examined. A soot sampling probe and a thermocouple were used to measure the local soot mass concentration and flame temperature, respectively. Flame residence time was predicted using a uniformly accelerated motion model as a function of axial distance of the flame. The increase of primary air flow rate was found to suppress the energy transfer from the annular region, at which the soot is produced, to the flame axis. The time required to initiate soot formation at the flame axis becomes longer as the primary air is increased. The trend rate of soot formation was found to be similar along the flame axis in all tested diffusion flames. The increase of primary air by 10% of the stoichiometric air requirement of the fuel results in a 70% reduction in maximum soot concentration. The final exhaust of soot, which is determined by the net effect of soot formation and burnout, is much lower in double flames than that in diffusion flames.

[1]  J. Lahaye,et al.  An experimental investigation into soot formation and distribution in polymer diffusion flames , 1980 .

[2]  J. Kent,et al.  The effect of alkali metals on a laminar ethylene diffusion flame , 1993 .

[3]  O. Nishida,et al.  Characteristics of soot formation and decomposition in turbulent diffusion flames , 1982 .

[4]  P. A. Bonczyk.  Measurement of particulate size by in situ laser-optical methods: A critical evaluation applied to fuel-pyrolyzed carbon , 1979 .

[5]  I. Glassman,et al.  Soot formation in diffusion flames of fuel/oxygen mixtures , 1989 .

[6]  Robert J. Santoro,et al.  The Transport and Growth of Soot Particles in Laminar Diffusion Flames , 1987 .

[7]  Ian M. Kennedy,et al.  Models of soot formation and oxidation , 1997 .

[8]  P. A. Bonczyk,et al.  Optical and Probe Measurements of Soot in a Burning Fuel Droplet Stream , 1984 .

[9]  H. Hiroyasu,et al.  Soot formation by combustion of a fuel droplet in high pressure gaseous environments , 1977 .

[10]  F. G. Roper.  The prediction of laminar jet diffusion flame sizes: Part I. Theoretical model , 1977 .

[11]  C. Smith,et al.  The prediction of laminar jet diffusion flame sizes: Part II. Experimental verification , 1977 .

[12]  R. H. Oppermann.  Mechanics for engineers , 1985 .

[13]  J. Howard,et al.  Soot and hydrocarbon formation in a turbulent diffusion flame , 1977 .

[14]  S. Harris,et al.  Soot Particle Growth in Premixed Toluene/Ethylene Flames , 1984 .

[15]  R. P. Benedict,et al.  Fundamentals of temperature, pressure, and flow measurements , 1977 .

[16]  T. M. Dyer,et al.  A Phenomenological Description of Particulate Formation during Constant Volume Combustion , 1981 .

[17]  S. Harris,et al.  Soot particle inception kinetics in a premixed ethylene flame , 1986 .

[18]  Reginald E. Mitchell,et al.  Experimental and numerical investigation of confined laminar diffusion flames , 1980 .

[19]  Robert J. Santoro,et al.  Soot particle measurements in diffusion flames , 1983 .