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Title: Hydroxyl time series and recirculation in turbulent nonpremixed swirling flames

Journal Article · · Combustion and Flame
; ; ; ;  [1];  [2]
  1. School of Mechanical Engineering, Purdue University, West Lafayette, IN 47907-1288 (United States)
  2. Department of Mechanical Engineering, University of Connecticut, Storrs, CT 06269-3139 (United States)

Time-series measurements of OH, as related to accompanying flow structures, are reported using picosecond time-resolved laser-induced fluorescence (PITLIF) and particle-imaging velocimetry (PIV) for turbulent, swirling, nonpremixed methane-air flames. The [OH] data portray a primary reaction zone surrounding the internal recirculation zone, with residual OH in the recirculation zone approaching chemical equilibrium. Modeling of the OH electronic quenching environment, when compared to fluorescence lifetime measurements, offers additional evidence that the reaction zone burns as a partially premixed flame. A time-series analysis affirms the presence of thin flamelet-like regions based on the relation between swirl-induced turbulence and fluctuations of [OH] in the reaction and recirculation zones. The OH integral time-scales are found to correspond qualitatively to local mean velocities. Furthermore, quantitative dependencies can be established with respect to axial position, Reynolds number, and global equivalence ratio. Given these relationships, the OH time-scales, and thus the primary reaction zone, appear to be dominated by convection-driven fluctuations. Surprisingly, the OH time-scales for these nominally swirling flames demonstrate significant similarities to previous PITLIF results in nonpremixed jet flames. (author)

OSTI ID:
20824156
Journal Information:
Combustion and Flame, Vol. 147, Issue 1-2; Other Information: Elsevier Ltd. All rights reserved; ISSN 0010-2180
Country of Publication:
United States
Language:
English