TY - JOUR
T1 - Flame structure of lean premixed and diffusion combined flames near extinction limit
AU - Kawanami, Takayuki
AU - Yahagi, Yuji
N1 - Copyright:
Copyright 2012 Elsevier B.V., All rights reserved.
PY - 2012
Y1 - 2012
N2 - Extinction and flame structure of lean premixed and diffusion combined flames formed in a counter flow are investigated experimentally and numerically. The extinction limits can be divided into two regions. One is a diffusion flame dominant extinction region (DF-DE) in which equivalence ratio of LPF side (φ L) at extinction limit is decreasing linearly with increasing fuel concentration of DF side (χ U). The other is a lean premixed flame dominant extinction region (LPF-DE) in which effect of χ U on extinction φ L is increasing with increasing χ U. In these two regions, the flame structures and its φ L dependence are different greatly. In the DF-DE, the temperature has symmetrical profile regardless of φ L and the temperature peak is located near DF. Since DF has higher temperature than LPF, LPF is thermally supported than DF. Temperature gradients between two reaction zones are decreasing with increasing φ L, while laminar burning velocity (S L) and burnt gas width (W B) are constant regardless of φ L. On the other hand, in the LPF-DE, the temperature has asymmetrical profile and the temperature peak leans to the LPF side. That is, the temperature gradient of LPF side is very steep compared with the DF side. Since LPF has higher temperature than DF, DF is thermally supported than LPF. Temperature gradients between two reaction zones are constant regardless of φ L, while S L and W B are increasing with increasing φ L.
AB - Extinction and flame structure of lean premixed and diffusion combined flames formed in a counter flow are investigated experimentally and numerically. The extinction limits can be divided into two regions. One is a diffusion flame dominant extinction region (DF-DE) in which equivalence ratio of LPF side (φ L) at extinction limit is decreasing linearly with increasing fuel concentration of DF side (χ U). The other is a lean premixed flame dominant extinction region (LPF-DE) in which effect of χ U on extinction φ L is increasing with increasing χ U. In these two regions, the flame structures and its φ L dependence are different greatly. In the DF-DE, the temperature has symmetrical profile regardless of φ L and the temperature peak is located near DF. Since DF has higher temperature than LPF, LPF is thermally supported than DF. Temperature gradients between two reaction zones are decreasing with increasing φ L, while laminar burning velocity (S L) and burnt gas width (W B) are constant regardless of φ L. On the other hand, in the LPF-DE, the temperature has asymmetrical profile and the temperature peak leans to the LPF side. That is, the temperature gradient of LPF side is very steep compared with the DF side. Since LPF has higher temperature than DF, DF is thermally supported than LPF. Temperature gradients between two reaction zones are constant regardless of φ L, while S L and W B are increasing with increasing φ L.
KW - Combustion phenomena
KW - Counterflow
KW - Diffusion combustion
KW - Extinction
KW - Flame structure
KW - Flame to flame interaction
KW - Premixed combustion
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U2 - 10.1299/kikaib.78.1118
DO - 10.1299/kikaib.78.1118
M3 - Article
AN - SCOPUS:84862150924
SN - 0387-5016
VL - 78
SP - 1118
EP - 1126
JO - Nihon Kikai Gakkai Ronbunshu, B Hen/Transactions of the Japan Society of Mechanical Engineers, Part B
JF - Nihon Kikai Gakkai Ronbunshu, B Hen/Transactions of the Japan Society of Mechanical Engineers, Part B
IS - 789
ER -