69th Annual Meeting of the APS Division of Fluid Dynamics (November 20, 2016 — November 22, 2016)

V0047: The Blue Whirl: A Soot-Free Reacting Vortex Phenomenon

Authors

• Michael Gollner, University of Maryland, College Park
• Sriram Bharath Hariharan, University of Maryland, College Park
• Huahua Xiao, University of Maryland, College Park
• Elaine Oran, University of Maryland, College Park

DOI: https://doi.org/10.1103/APS.DFD.2016.GFM.V0047

Fire whirls are powerful, spinning disasters for people and surroundings when they occur in large urban and wildland fires. Whereas fire whirls have been studied for fire-safety applications, previous research has yet to harness their potential burning efficiency for enhanced combustion. Here, we show the transition from a pool fire, to a fire whirl, and then to a previously unobserved state, a “blue whirl.” A blue whirl is smaller, very stable, and burns completely blue as a hydrocarbon flame, indicating soot-free burning. The combination of fast mixing, intense swirl, and the water–surface boundary creates the conditions leading to nearly soot-free combustion. With the worldwide need to reduce emissions from both wanted and unwanted combustion, discovery of this state points to possible new pathways for reduced-emission combustion and fuel-spill cleanup. Because current methods to generate a stable vortex are dificult, we also propose that the blue whirl may serve as a research platform for fundamental studies of vortices and vortex breakdown in fluid mechanics.

Video from the article: www.pnas.org/cgi/doi/10.1073/pnas.1605860113