Point-to-plane pulsed discharge initiated flame structure modification in propane–air flame

Abstract

The effect of a point-to-plane pulsed discharge on a propane/air flame has been investigated by phase-locked simultaneous measurements of the change in gas temperature and OH planar laser-induced-fluorescence (PLIF). Phase-locked simultaneous measurement of gas temperature through spontaneous Raman scattering and OH PLIF with the variation of pulsed plasma energy and plasma generation location with respect to the flame holder and flame reaction zone have been performed. A fast rise time (15 ns) and a slower rise time (150 ns) high voltage pulsers are used to produce OH radical densities 50% greater than the ambient flame produced OH radicals in both lean and rich premixed flames. The excess OH radical densities were found to decay to the 50% level with time constants greater than 100 µs in the burnt gas regions with gas temperatures greater than 1000 K. The flame perturbation was dependent on the pulse repetition rates as well as on the pulse rise time for similar energy deposition per pulse. A laser photo-deflection measurement of acoustic pressure pulse generation by the pulsed discharge suggests that flame perturbation by the downstream plasma is caused mostly by flow perturbation.