Flaming fuel on water creates ‘blue whirl’ that burns clean

Method may have practical use in fuel spill cleanup

blue whirls

BLUE WHIRL  A swirling flame called a blue whirl is produced in the lab by igniting fuel floating on top of water (left). The flame first transitions into a 60-centimeter-tall fire tornado (center) before settling down into a quietly spinning blue flame (right) just 6 centimeters in height.

H. Xio, M.J. Gollner, E.S. Oran/PNAS 2016

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Blue whirl
Bloo werl n.

A swirling flame that appears in fuel floating on the surface of water and glows blue.

An unfortunate mix of electricity and bourbon has led to a new discovery. After lightning hit a Jim Beam warehouse in 2003, a nearby lake was set ablaze when the distilled spirit spilled into the water and ignited. Spiraling tornadoes of fire leapt from the surface. In a laboratory experiment inspired by the conflagration, a team of researchers produced a new, efficiently burning fire tornado, which they named a blue whirl.

To re-create the bourbon-fire conditions, the researchers, led by Elaine Oran of the University of Maryland in College Park, ignited liquid fuel floating on a bath of water. They surrounded the blaze with a cylindrical structure that funneled air into the flame to create a vortex with a height of about 60 centimeters. Eventually, the chaotic fire whirl calmed into a blue, cone-shaped flame just a few centimeters tall, the scientists report online August 4 in Proceedings of the National Academy of Sciences.

“Firenadoes” are known to appear in wildfires, when swirling winds and flames combine to form a hellacious, rotating inferno. They burn more efficiently than typical fires, as the whipping winds mix in extra oxygen, which feeds the fire. But the blue whirl is even more efficient; its azure glow indicates complete combustion, which releases little soot, or uncombusted carbon, to the air.

The soot-free blue whirls could be a way of burning off oil spills on water without adding much pollution to the air, the researchers say, if they can find a way to control them in the wild.

SWIRLING FLAME Fuel burning on top of water produces a flaming tornado that transitions into a calmly spinning blue whirl.H. Xio, M.J. Gollner, E.S. Oran/Univ. of Maryland

Physics writer Emily Conover has a Ph.D. in physics from the University of Chicago. She is a two-time winner of the D.C. Science Writers’ Association Newsbrief award.

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