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Enhanced Soot Formation in Flickering CH4/Air Diffusion Flames.

pdf icon Enhanced Soot Formation in Flickering CH4/Air Diffusion Flames. (527 K)
Shaddix, C. R.; Harrington, J. E.; Smyth, K. C.

American Chemical Society (ACS). Reprints of the Fuel Chemistry Division, 1-8 pp, 1994.


soot formation; laminar flames; diffusion flames; extinction; methane; soot


Optical methods are used to examine soot production in a co-flowing, axisymmetric CH4/air diffusion flame in which the fuel flow rate is acoustically forced to create a time-varying flowfield. For a particular forcing condition in which tip clipping occurs (0.75 V loudspeaker excitation), elastic scattering of vertically polarized light from the soot particles increases by nearly an order of magnitude with respect to the observed for a steady flame with the same mean fuel flow rate. Peak soot volume fractions, as measured by time-resolved laser extinction/tomography at 632.8 and 454.4 nm and calibrated laser-induced incandescence (LII), show a factor of 4-5 enhancement in this flickering flame. A Mie analysis suggests that most of the enhanced soot production results from the formation of larger particles in the time-varying flowfield.