A Study on the Structure of Premixed Turbulent Propagating Flames : An Investigation and Application of the Flame Plasma Potential Signal

Abstract

A method using a passive electrostatic probe to detect a flame by its plasma potential signal has been developed. The spatial resolution of the probe in this method is shown to be significantly improved over that of the conventional electrostatic probe. The plasma potential signals obtained by this method from premixed turbulent propagating flames show one to six spikes in each signal ; each spike is considered to be a flamelet in the flame zone. On the basis of this consideration, the propagating speed, the thickness of the flame zone, the number of flamelets in the zone, the separation distance between two adjacent flamelets, etc., of the flame, were obtained. The results of this experiment suggest the existence of "reactant islands" in the turbulent flame zone, and show that the number of flamelets in the zone increases with an increase in the turbulence intensity for the same mixture and/or a decrease in the Damkohler number for mixtures with the same turbulence intensity.