Journal of the Korean Society of Combustion ISSN:1226-0959(Print) 2466-2089(Online) 한국연소학회지

An experimental study has been conducted to elucidate the effect of AC electric field on behaviors of laminar lifted flame in nitrogen-diluted methane coflow-jets. Our concerns are focued on the regime to show a decrease in liftoff height, HL with increasing nozzle exit velocity, UO (hereafter, decreasing-HL). The HL with UO near flame extinction were measured by varying the applied AC voltage, VAC and frequency, fAC in a single electrode configuration. The behavior of HL with a functional dependency of VAC and fAC was categorized into two regime : (I) HL decreased for nozzle diameter, D = 1.0 mm, and (II) HL increased in the increase of fAC for a fixed VAC in a D = 4.0, 8.4 mm. The lifted flames in decreasing-HL region was unstable in high voltage regimes while the HL showed a decreasing tendency with UO except them. Such behaviors in HL were also characterized by functional dependencies of related physical parameters such as VAC, fAC, UO, fuel mole fraction (XF.O) and D.