Our research program on flames is focused on developing alternative methodologies for the suppression and control of fires (1, 2). We are currently focused on several promising approaches to control flames: one, based on electric fields; the other, on powerful acoustic perturbations.
The first approach relies on the fact that hydrocarbon flames are actually chemically driven, non-equilibrium plasmas. As such, they contain large concentrations of charged species (typically, ~1011 charges per cubic centimeter) that respond collectively to externally applied electric fields. Importantly, the movement of ions and electrons in the field can transfer momentum to the surrounding gas though frequent collisions with neutral species. For sufficiently large fields, this process can result in macroscopic gas flows – so-called ionic or electric wind – with speeds of up to ten meters per second. When placed in the proximity of a flame, the resulting gas flows act in a highly directional manner to rapidly displace the combustion zone from the fuel source.
The second approach provides oscillatory perturbations to the flame with acoustic waves. We are exploring the required acoustic conditions necessary for extinction. Our goal is to understand the fundamental physics and potential applications of using sound to manipulate combustive processes.
We are currently working to elucidate the mechanistic details underlying electric and acoustic fire suppression, and to scale these approaches to address larger fires of practical interest. In addition we are exploring a wealth of novel ways to affect and control flames (e.g. focusing the heat of flames).
1. Drews AM, Cademartiri L, Whitesides GM, Bishop KJM (2013) "Electric winds driven by time oscillating corona discharges", J Appl Phys 114(14).
2. Fox J, Whitesides G (2015) "Warning signals for eruptive events in spreading fires", Proc Natl Acad Sci 112(8):2378.