TY - JOUR
T1 - Extinction and flame bifurcations of stretched dimethyl ether premixed flames
AU - Ju, Yiguang
AU - Xue, Yuan
N1 - Funding Information:
This work is partially supported by the American Chemistry Society research grant PRF#39162-AC9 and the NASA microgravity research grant (NNC04GA59G). Partial support for this research has also been provided by the Carbon Mitigation Initiative, a Princeton University Research Program supported by BP and Ford.
PY - 2005
Y1 - 2005
N2 - Extinction limits and flame bifurcation of lean premixed dimethyl ether-air flames are numerically investigated using the counterflow flame with a reduced chemistry. Emphasis is paid to the combined effect of radiation and flame stretch on the extinction and flammability limits. A method based on the reaction front is presented to predict the Markstein length. The predicted positive Markstein length agrees well with the experimental data. The results show that flow stretch significantly reduces the flame speed and narrows the flammability limit of the stretched dimethyl ether-air flame. It is found that the combined effect of radiation and flow stretch results in a new flame bifurcation and multiple flame regimes. At an equivalence ratio slightly higher than the flammability limit of the planar flame, the distant flame regime appears at low stretch rates. With an increase in the equivalence ratio, in addition to the distant flame, a weak flame isola emerges at moderate stretch rates. With a further increase in the equivalence ratio, the distant flame and the weak flame branches merge together, resulting in the splitting of the weak flame branch into two weak flame branches, one at low stretch and the other at high stretch. Flame stability analysis demonstrates that the high stretch weak flame is also stable. Furthermore, a K-shaped flammability limit diagram showing various flame regimes and their extinction limits is obtained.
AB - Extinction limits and flame bifurcation of lean premixed dimethyl ether-air flames are numerically investigated using the counterflow flame with a reduced chemistry. Emphasis is paid to the combined effect of radiation and flame stretch on the extinction and flammability limits. A method based on the reaction front is presented to predict the Markstein length. The predicted positive Markstein length agrees well with the experimental data. The results show that flow stretch significantly reduces the flame speed and narrows the flammability limit of the stretched dimethyl ether-air flame. It is found that the combined effect of radiation and flow stretch results in a new flame bifurcation and multiple flame regimes. At an equivalence ratio slightly higher than the flammability limit of the planar flame, the distant flame regime appears at low stretch rates. With an increase in the equivalence ratio, in addition to the distant flame, a weak flame isola emerges at moderate stretch rates. With a further increase in the equivalence ratio, the distant flame and the weak flame branches merge together, resulting in the splitting of the weak flame branch into two weak flame branches, one at low stretch and the other at high stretch. Flame stability analysis demonstrates that the high stretch weak flame is also stable. Furthermore, a K-shaped flammability limit diagram showing various flame regimes and their extinction limits is obtained.
KW - Bifurcation
KW - Dimethyl ether
KW - Extinction limit
KW - Radiation
KW - Stretch
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U2 - 10.1016/j.proci.2004.08.258
DO - 10.1016/j.proci.2004.08.258
M3 - Conference article
AN - SCOPUS:84964253322
SN - 1540-7489
VL - 30
SP - 295
EP - 301
JO - Proceedings of the Combustion Institute
JF - Proceedings of the Combustion Institute
IS - 1
T2 - 30th International Symposium on Combustion
Y2 - 25 July 2004 through 30 July 2004
ER -