The smoke point measurements yielded estimates
of soot-forming conditions and flame dimensions.
Flames of propylene and propylene mixtures were
generally more luminous than the others,
attributed to increased soot volume fractions.
Periodic flame motion was observed in some
flames, especially those with high air velocity, large
burners, and long flames, and is attributed to
unsteady co-flow air stream causing slight increase
in the uncertainties in smoke points under these
conditions. Smoke points for propane and ethylene
were generally identified by the onset of gradual
dimming, reddening, and rounding of the luminous
flame tip. The brightest flames, generally for
propylene and propylene mixtures, normally did not display significant dimming and reddening
near their tips except when much longer than their smoke points. Smoke points for these
flames were identified by the rapid transition to open-tipped flames. Open-tipped flames are
common in both normal gravity and microgravity when smoke points are far exceeded and are
generally associated with local flame extinguishment along the centerline and soot emission in
an annular shell. For conditions sufficiently above the smoke points, a glowing stream of
particles could be seen leaving the flame. Smoke-point lengths in co-flow generally increase
with decreasing burner diameter and increasing co-flow velocity in agreement with normal-
gravity results. This is expected because a decrease in burner—or an increase in co-flow
velocity—decreases the residence time (the time a fuel molecule takes to pass through the
entire flame) available for soot formation. It also decreases the radiative heat loss fraction,
making the flame shorter and narrower.
Microgravity smoke points are of interest to spacecraft fire safety. Microgravity allows
improved control over residence time and provides better understanding of the different
mechanisms responsible for smoke points in normal gravity and microgravity (Dotson 2011).
PUBLICATION(S)
Dotson KT, Sunderland PB, Yuan Z, Urban DL. Laminar smoke points of co-flowing flames in
microgravity. Fire Safety Journal. November 2011; 46(8):550-555. doi:
10.1016/j.firesaf.2011.08.002.
Dotson KT, Sunderland PB, Yuan Z, Urban DL. Laminar smoke points in co-flow measured
aboard the International Space Station. 48th Aerospace Sciences Meeting and Exhibit, Orlando,
FL; 2010.
Dotson KT. Smoke points of microgravity and normal gravity co-flow diffusion flames. Master's
Thesis, University of Maryland, College Park, MD; 2009.
This investigation is complete and all results are published.
ISS018E030371 – View of the flame ignited in the
SPICE (Smoke Point In Co-flow Experiment)
payload performed in the MSG and controlled by its
A31p with SPICE microdrives. Photo was taken by
Expedition 18 crew.