ac electric fields drive steady flows in flames

Aaron M. Drews, Ludovico Cademartiri, Michael L. Chemama, Michael P. Brenner, George M. Whitesides, Kyle J. M. Bishop
2012 Physical Review E  
We show that time-oscillating electric fields applied to plasmas present in flames create steady flows of gas. Ions generated within the flame move in the field and migrate a distance  before recombining; the net flow of ions away from the flame creates a time-averaged force that drives the steady flows observed experimentally. A quantitative model describes the response of the flame and reveals how  decreases as the frequency of the applied field increases. Interestingly, above a critical
more » ... above a critical frequency, AC fields can be used to manipulate flames at a distance without the need for proximal electrodes. The most familiar description of a flame is "a local region of high temperature generated by rapid, exothermic chemical reactions". A flame is, however, also a plasma. In particular, the combustion of hydrocarbon fuels generates sufficient densities of charged species that even small flames (the flame of a humble candle) can be considered as chemically driven, nonequilibrium plasmas [1]. As such, flames interact with external electric fields, which can be used to monitor [2], manipulate [3, 4] , and enhance [5, 6] the processes that make up "combustion" through a variety of physical and chemical mechanisms. Sufficiently strong electric fields (>10 6 V/m at atmospheric pressure) influence the chemistry of combustion by accelerating electrons to energies capable of exciting, dissociating, or ionizing neutral species upon impact [6] . Even fields that are too weak to influence combustion directly can cause
doi:10.1103/physreve.86.036314 pmid:23031020 fatcat:mipaaqaonneo7afqgia6oiedne