TY - JOUR
T1 - Experimental and theoretical study of secondary acoustic instability of downward propagating flames
T2 - Higher modes and growth rates
AU - Dubey, Ajit K.
AU - Koyama, Yoichiro
AU - Hashimoto, Nozomu
AU - Fujita, Osamu
N1 - Funding Information:
This study is carried out under the collaboration of Hokkaido University and Mitsubishi Heavy Industries. The analytical part of this study was carried out under support of a Grant-in-Aid for Scientific Researches (KIBAN (B) #26289042 and KIBAN(A)#18H03755) from MEXT Japan.
Publisher Copyright:
© 2019 The Combustion Institute
PY - 2019/7
Y1 - 2019/7
N2 - Flames propagating in tubes open at the ignition end typically show two different kinds of thermo-acoustic instability namely, primary and secondary. Secondary acoustic instability is accompanied by parametric instability of flame front during which, cellular structures on the flame surface oscillate with half the acoustic frequency of excitation. The growth rates associated with secondary acoustic instability of flame structure are higher compared to primary instability of flames leading to very high peak pressures. In this work, we present experimental and theoretical study on parametric instability of downward propagating C2H4/O2/CO2 flames at two different Le of 1.0 and 0.8. Lower Le mixtures are found to be more unstable. Parametric instability of higher acoustic modes is reported for the first time for gaseous fuels. Higher modes of parametric instability transitioned successively to lower modes as the flame propagated downward. Growth rate of parametric instability is measured in experiments. Theoretical prediction of growth rate is done based on velocity coupling mechanism. Theoretical calculations provide good approximation of growth rates and its variation with frequency.
AB - Flames propagating in tubes open at the ignition end typically show two different kinds of thermo-acoustic instability namely, primary and secondary. Secondary acoustic instability is accompanied by parametric instability of flame front during which, cellular structures on the flame surface oscillate with half the acoustic frequency of excitation. The growth rates associated with secondary acoustic instability of flame structure are higher compared to primary instability of flames leading to very high peak pressures. In this work, we present experimental and theoretical study on parametric instability of downward propagating C2H4/O2/CO2 flames at two different Le of 1.0 and 0.8. Lower Le mixtures are found to be more unstable. Parametric instability of higher acoustic modes is reported for the first time for gaseous fuels. Higher modes of parametric instability transitioned successively to lower modes as the flame propagated downward. Growth rate of parametric instability is measured in experiments. Theoretical prediction of growth rate is done based on velocity coupling mechanism. Theoretical calculations provide good approximation of growth rates and its variation with frequency.
KW - Combustion tube
KW - Downward propagating flames
KW - Higher modes
KW - Lewis number
KW - Parametric instability
KW - Secondary instability
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U2 - 10.1016/j.combustflame.2019.04.010
DO - 10.1016/j.combustflame.2019.04.010
M3 - Article
AN - SCOPUS:85064610730
VL - 205
SP - 316
EP - 326
JO - Combustion and Flame
JF - Combustion and Flame
SN - 0010-2180
ER -