Laminar smoke points of nonbuoyant jet diffusion flames☆

Effects of Gravity on Soot Formation in a Coflow Laminar Methane/Air Diffusion Flame

“…Therefore, the residence time of soot in non-buoyant flame is longer than that in buoyant flame mainly due to the much lower axial velocities in reduced gravity environment. This is in agreement with the analysis in Sunderland et al (1994). The predicted peak soot volume fraction in normal gravity is 0.612 ppm, which is reasonably good agreement with the measured maximum of 0.56 ppm for a steady but somewhat larger methane-air coflow diffusion flame (Kaplan et al 1996b).…”

“…Thus soot research has received considerable attention in both normal gravity and microgravity (Haynes and Wagner 1981;Glassman 1988;K ue ta l .1995;Haggard and Cochran 1972;Greenberg and Ku 1997a, b;Megaridis et al 1996;Sunderland et al 1994;Urban et al 2000;Konsur and Megaridis 1999;Lin et al 1999;Aalburg et al 2005;Walsh et al 2000;Kaplan et al 1996a). In microgravity, the elimination of buoyancyinduced flows increases the residence time and decreases the fresh air supply.…”

“…Most studies have focused on experimental investigations on the soot field structures at microgravity (Greenberg and Ku 1997a, b;Megaridis et al 1996;Sunderland et al 1994;Urban et al 2000;Konsur and Megaridis 1999;Lin et al 1999;Aalburg et al 2005) to elucidate the effects of buoyancy on soot formation. However, it is difficult to investigate all the aspects that influence soot formation because of the cost and the limited number of experiments that can be conducted in microgravity.…”

Smoke-point properties of non-buoyant round laminar jet diffusion flames

“…Because changes may be made before formal publication, this is made available with the understanding that it will not be cited or reproduced without the permission of the author. The potential differencesbetweenthe laminar smoke propertiesof buoyant and nonbuoyant flamescanbeattributedmainlyto thedifferenthydrodynamicpropertiesof these flames [24][25][26][27]. In particular,sootparticlesaretoo largeto diffuse like gasmoleculessothat they areconvectedby gasvelocitiesasidefrom minor effectsof thermophoresis [24].…”

“…The potential differencesbetweenthe laminar smoke propertiesof buoyant and nonbuoyant flamescanbeattributedmainlyto thedifferenthydrodynamicpropertiesof these flames [24][25][26][27]. In particular,sootparticlesaretoo largeto diffuse like gasmoleculessothat they areconvectedby gasvelocitiesasidefrom minor effectsof thermophoresis [24]. Thesedifferencesgenerallyhavebeenattributedto the different soot pathsin buoyantand nonbuoyant flames that were just discussedas well as increasedeffects of radiative quenching in nonbuoyant flames due to their increasedcharacteristic residencetimes comparedto buoyantflames.…”