TY - JOUR
T1 - Ultra-lean combustion through the backflow of burned gas in rotating counterflow twin premixed flames
AU - Nishioka, Makihito
AU - Shen, Zhenyu
AU - Uemichi, Akane
PY - 2011/11
Y1 - 2011/11
N2 - Rotating counterflow twin premixed flames of methane-air were numerically simulated with detailed chemistry based on a similarity solution to explore the leanest extinction limit without preheating and to elucidate the mechanism of " ultra-lean" combustion. We focused on high rotation rate cases in which unrealistic backflow from infinity is allowed to occur since ultra-lean combustion was found to be realized in such a situation. It was found that the reaction zone is in the backflow zone, where the flame's apparent burning velocity is negative, and that the flame zone width is much smaller than that of a 1-D planar premixed flame due to an inversion of the convexity directions of the profiles of temperature and main species concentrations. The decrease of the flame width seems to make the flame less extinguishable. The equivalence ratio of the leanest flame obtained neglecting radiative heat loss is 0.32, while that obtained with an optically thin radiation model is 0.42, which is still much leaner than the ratio of 0.49 for a 1-D planar premixed flame generated using the same radiation model.
AB - Rotating counterflow twin premixed flames of methane-air were numerically simulated with detailed chemistry based on a similarity solution to explore the leanest extinction limit without preheating and to elucidate the mechanism of " ultra-lean" combustion. We focused on high rotation rate cases in which unrealistic backflow from infinity is allowed to occur since ultra-lean combustion was found to be realized in such a situation. It was found that the reaction zone is in the backflow zone, where the flame's apparent burning velocity is negative, and that the flame zone width is much smaller than that of a 1-D planar premixed flame due to an inversion of the convexity directions of the profiles of temperature and main species concentrations. The decrease of the flame width seems to make the flame less extinguishable. The equivalence ratio of the leanest flame obtained neglecting radiative heat loss is 0.32, while that obtained with an optically thin radiation model is 0.42, which is still much leaner than the ratio of 0.49 for a 1-D planar premixed flame generated using the same radiation model.
KW - Burned gas backflow
KW - Extinction limit
KW - Negative burning velocity
KW - Rotating counterflow twin flame
KW - Ultra-lean combustion
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U2 - 10.1016/j.combustflame.2011.04.002
DO - 10.1016/j.combustflame.2011.04.002
M3 - Article
AN - SCOPUS:80052934372
VL - 158
SP - 2188
EP - 2198
JO - Combustion and Flame
JF - Combustion and Flame
SN - 0010-2180
IS - 11
ER -