Aug 14, 2020 - Science

Scientists discover blue whirl fire is made from three flames

Blue whirl caused by tornadoes
Blue whirl. Photo: Sriram Bharath Hariharan/University of Maryland

A fire phenomenon known as the blue whirl can emerge from fire tornadoes. This week scientists reported new details of the structure of the mysterious clean-burning flame.

Why it matters: Researchers hope to one day harness the blue whirl as a source of energy and to clean up fuel spills. To do that, they need to understand the flame's form — and how it might be controlled.

Background: A team at the University of Maryland discovered the blue whirl in 2016 when testing the idea of using fire whirls, products of intense heat and wind, to clean up oil spilled on water.

  • Fire whirls generate soot (though not as much as typical fires) — small particles of carbon produced when fuel isn't completely burned and that give a flame its yellow color.
  • In a lab, the whirls can transition to become blue whirls, in which the fuel is completely combusted and no soot is produced.

What they did: Joseph Chung, Xiao Zhang and their colleagues at the University of Maryland created a computer simulation of the blue whirl and compared it with video of the flame forming in the lab.

  • They found the whirl is made up of "a diffusion flame and premixed rich and lean flames — all of which meet in a fourth structure, a triple flame that appears as a whirling blue ring," they write in Science Advances.
  • Blue whirls haven't been seen in nature. Why and under what conditions they may occur in nature are still open questions, says Chung.

What's next: "This is a first step to applying the blue whirl to a more practical application," says Zhang. There are more questions, she adds, for example: whether a larger blue whirl can be created so it can burn more effectively (it is currently just a few inches in size) and whether it can burn faster.

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