August 2020
Vol 6, Issue 33

About The Cover

Cover image expansion

ONLINE COVER Scientists recently discovered the formation of a soot-free flame called a blue whirl—which consumes all fuel it encounters—while experimenting with fire whirls produced by burning liquid hydrocarbon fuels on a water base. But while further investigations have since produced temperature maps of blue whirls and informed how they can be stabilized, their flame structure and dynamics—especially how they form from a fire whirl—have remained mysterious. To simulate how blue whirls emerge, Chung et al. coupled 3D, time-dependent equations that describe the motion of viscous fluid substances to a model for fuel conversion and chemical energy release. The researchers started by simulating experimental conditions, then tweaked physical parameters such as fuel and air size and velocity in their calculations until a blue whirl materialized. The researchers found that the ethereal flame is composed of three different flames: a diffusion flame, in which the fuel and oxidizer are separated before burning, and premixed rich (with excess fuel) and lean (with excess air) flames. By revealing the blue whirl's structure, the findings may inform potential applications of the flame for efficient, low-emission combustion. [CREDIT: DR. SRIRAM BHARATH HARIHARAN]