Enhanced Soot Formation in Flickering CH4/Air Diffusion Flames.
Enhanced Soot Formation in Flickering CH4/Air Diffusion
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.