From fire whirls to blue whirls and combustion without pollution

TL;DR

This study discovers a new, stable, soot-free blue whirl state in laboratory fire experiments on water surfaces, offering insights into efficient, low-emission combustion and potential applications in pollution cleanup.

Contribution

The paper introduces the blue whirl, a previously unobserved stable vortex state with complete blue-violet combustion, expanding understanding of fire vortex phenomena and combustion efficiency.

Findings

Identification of the blue whirl as a stable, soot-free combustion state

Demonstration of transition from fire whirl to blue whirl

Potential applications in low-emission energy and pollution cleanup

Abstract

Fire whirls are powerful, spinning disasters for people and surroundings when they occur in large urban and wildland fires. While fire whirls have long been studied for fire safety applications, previous research has yet to harness their potential burning efficiency for enhanced combustion. This paper presents laboratory studies of fire whirls initiated as pool fires, but where the fuel sits on a water surface, seeding an idea of exploiting the high-efficiency of fire whirls for oil-spill remediation. 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-violet in a hydrocarbon flame, indicating soot-free burning. The combination of fast mixing 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 new state points to new pathways for highly efficient and low-emission energy production and fuel-spill cleanup. Because current methods to generate a stable vortex are difficult, we also propose that the blue whirl may serve as a research platform for fundamental studies of vortices in fluid mechanics.