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Journal of Flow Visualization and Image Processing
SJR: 0.161 SNIP: 0.312 CiteScore™: 0.1

ISSN Imprimer: 1065-3090
ISSN En ligne: 1940-4336

Journal of Flow Visualization and Image Processing

DOI: 10.1615/JFlowVisImageProc.v5.i3.50
pages 239-247

SINGLE-PULSE LASER-INDUCED PREDISSOCIATIVE FLUORESCENCE IMAGING OF OH IN SWIRLING METHANE JET FLAMES

T. S. Cheng
Department of Mechanical Engineering, Chung Hua University, Hsinchu, Taiwan, 300, R.O.C.
Y.-C. Chao
Institute of Aeronautics and Astronautics, National Cheng Kung University, Tainan, Taiwan, 701, R.O.C.
D.-C. Wu
Institute of Aeronautics and Astronautics, National Cheng Kung University, Tainan, Taiwan, 701, R.O.C.
Tony Yuan
Department of Aeronautics and Astronautics, National Cheng Kung University, Tainan, Taiwan, ROC
C.-C. Lu
Institute of Aeronautics and Astronautics, National Cheng Kung University, Tainan, Taiwan, 701, R.O.C.
C.-K. Cheng
Institute of Aeronautics and Astronautics, National Cheng Kung University, Tainan, Taiwan, 701, R.O.C.
J.-M. Chang
Institute of Aeronautics and Astronautics, National Cheng Kung University, Tainan, Taiwan, 701, R.O.C.

RÉSUMÉ

Two-dimensional (2D) single-pulse laser-induced predissociative fluorescence (LIPF) imaging of OH coupled with thermocouple temperature measurement is used to study the flame structure and identify the NOx formation mechanism in swirling methane jet flames operated with three different fuel-air momentum flux ratios. In the upstream of the swirling flame, three major reaction zones are observed from the measured OH images. In addition, two characteristic combustion modes, the fuel jet-dominated flame and the strongly recirculating flame, are also identified from the OH visualization. The measured high OH intensity (superequilibrium OH) and low temperature (less than 1100 K) are identified to be the major sources of prompt NO formation in swirling methane jet flames.