Observations on the leading edge in lifted flame stabilization

The objective of this paper is to report some of the first experimental evi dence for the "leading edge" flame as the stabilization mechanism in lifted jet diffusion flames [1-5]. CH fluorescence has been used to indicate the flame front location (i.e., region of chemical reaction) and thereby charac terize features of the stabilization region [5, 6]. The "leading edge" flam e phenomenon reported within refers to the outward-extending branch of CH f luorescence at the base of the streamwise CH zones. Whether the "leading ed ge" flame is a special case of the more general triple flame is a question which remains unanswered. It is evident from previous computational studies [7, 8] that the triple flame, when interacting with a vortex or pair of vo rtices, can take on characteristics of the "leading edge" flames introduced in the present study. Veynante ct al. [8] illustrate the contortion of the premixed branches of the triple flame by the flowfield where the premixed branches are swept into the trailing diffusion flame. These simulated tripl e flame/vortex interactions are consistent with the results of this study w hich show a trailing diffusion flame and the leading edge reaction zone str ucture. (C) 1999 by The Combustion Institute.