TY - JOUR
T1 - Bifurcations and negative propagation speeds of methane/air premixed flames with repetitive extinction and ignition in a heated microchannel
AU - Nakamura, Hisashi
AU - Fan, Aiwu
AU - Minaev, Sergey
AU - Sereshchenko, Evgeniy
AU - Fursenko, Roman
AU - Tsuboi, Yosuke
AU - Maruta, Kaoru
N1 - Funding Information:
The authors would like to thank Prof. Yiguang Ju of Princeton University for his stimulating discussion on transient modeling of FREI. This work was partially supported by Grant-in-Aid for Scientific Research (B) of Japan (No. 18360097). Collaborative research with Prof. Sergey Minaev of RAS was supported by the Collaborative Research Project of the Institute of Fluid Science, Tohoku University and that with Dr. Aiwu Fan of HUST was supported by the Natural Science Foundation of China (No. 51076054).
PY - 2012/4
Y1 - 2012/4
N2 - Detailed behaviors of ignition kernel(s) in a uniform stoichiometric methane/air mixture under the temperature gradient were investigated numerically by using a fundamental system of microcombustion. Bifurcation of the heat release rate peak in an ignition phase at the high wall temperature side, which has been observed in previous experimental and theoretical studies, was successfully reproduced by the present computation. The bifurcated heat release rate peak exhibited negative propagation speed relative to the local flow velocity by consuming a separated methane/air mixture in the downstream side of the boundary zone between an incoming fresh mixture and burned gas. CH 4 was completely consumed at the main peak, whereas CO remained unreacted in the wide region behind the main peak. In a weak reaction phase at the low wall temperature side, two bifurcations of heat release rate peak were newly captured. By the two bifurcations, three heat release rate peaks, namely, a main and two bifurcated peaks appeared. The two bifurcations were caused by remaining intermediates such as CH 3, CO, H, and OH in the downstream side of the boundary zone. The main and one bifurcated peak disappeared, whereas the other bifurcated peak remained and flowed downstream. The main and two bifurcated peaks exhibited negative propagation speeds relative to local flow velocity by consuming the remaining intermediates. CO which formed in the middle of the boundary zone in the weak reaction phase remained unreacted and kept on flowing downstream, but did not flow out since the next cycle of the ignition phase was initiated there.
AB - Detailed behaviors of ignition kernel(s) in a uniform stoichiometric methane/air mixture under the temperature gradient were investigated numerically by using a fundamental system of microcombustion. Bifurcation of the heat release rate peak in an ignition phase at the high wall temperature side, which has been observed in previous experimental and theoretical studies, was successfully reproduced by the present computation. The bifurcated heat release rate peak exhibited negative propagation speed relative to the local flow velocity by consuming a separated methane/air mixture in the downstream side of the boundary zone between an incoming fresh mixture and burned gas. CH 4 was completely consumed at the main peak, whereas CO remained unreacted in the wide region behind the main peak. In a weak reaction phase at the low wall temperature side, two bifurcations of heat release rate peak were newly captured. By the two bifurcations, three heat release rate peaks, namely, a main and two bifurcated peaks appeared. The two bifurcations were caused by remaining intermediates such as CH 3, CO, H, and OH in the downstream side of the boundary zone. The main and one bifurcated peak disappeared, whereas the other bifurcated peak remained and flowed downstream. The main and two bifurcated peaks exhibited negative propagation speeds relative to local flow velocity by consuming the remaining intermediates. CO which formed in the middle of the boundary zone in the weak reaction phase remained unreacted and kept on flowing downstream, but did not flow out since the next cycle of the ignition phase was initiated there.
KW - Bifurcation
KW - Flames with repetitive extinction and ignition (FREI)
KW - Homogeneous charge compression ignition (HCCI)
KW - Microcombustion
KW - Negative flame speed
KW - Splitting flame
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U2 - 10.1016/j.combustflame.2011.11.004
DO - 10.1016/j.combustflame.2011.11.004
M3 - Article
AN - SCOPUS:84857371910
VL - 159
SP - 1631
EP - 1643
JO - Combustion and Flame
JF - Combustion and Flame
SN - 0010-2180
IS - 4
ER -