TY - JOUR
T1 - Generation of low frequency flame oscillations for the development of passive acoustic flame arresters
AU - Aravind, B.
AU - Sankar, Vigneshwaran
AU - Lacoste, Deanna A.
N1 - Funding Information:
This work was funded by the King Abdullah University of Science and Technology , through the baseline fund BAS/1/1396-01-01 .
Publisher Copyright:
© 2022
PY - 2023/1
Y1 - 2023/1
N2 - The development of acoustic-based flame arresters needs a profound understanding of low frequency flame fluctuations. The present study attempts the synthesis and analysis of such low frequency flame oscillations in a Rijke tube combustor subjected to external acoustic forcing. A high frequency (fn = 437±3 Hz) self-excited laminar premixed conical flame is considered. This flame is forced (ff)around its natural frequency (fn) to generate beating (fb=|ff−fn|). The results show that the system falls into lock-in synchronization for a range of forcing frequencies (0.97≤ff/fn≤1.03) at a forcing amplitude (εf) of 10% wherein quenching of natural mode is achieved. A strong flame beating is observed on either side of this synchronization region. The flame transfer function (FTF) at fb is then estimated to delineate the strength of the beating. The FTF gain at fb shows different behavior on either side of the synchronization region. For ff >fn, the gain exhibits a local peak at low beating frequencies (∼20 Hz) which is consistent with the response of a stable laminar conical flame subjected to acoustic forcing at these frequencies. However, for ffn, negligible FTF gain is obtained at low beating frequencies, followed by a continuous increase as the beating frequency increases. This asymmetric behavior is further analyzed using proper orthogonal decomposition technique (POD). For ff>fn, the POD results at low fbshow that the flame base undergoes a strong flapping-like oscillation at the beating frequency. However for ff n, the flame base oscillates only at the natural mode of the combustor. This different beating behavior of the system can be attributed to the strong and weak thermoacoustic coupling, after and before the synchronization region, respectively.
AB - The development of acoustic-based flame arresters needs a profound understanding of low frequency flame fluctuations. The present study attempts the synthesis and analysis of such low frequency flame oscillations in a Rijke tube combustor subjected to external acoustic forcing. A high frequency (fn = 437±3 Hz) self-excited laminar premixed conical flame is considered. This flame is forced (ff)around its natural frequency (fn) to generate beating (fb=|ff−fn|). The results show that the system falls into lock-in synchronization for a range of forcing frequencies (0.97≤ff/fn≤1.03) at a forcing amplitude (εf) of 10% wherein quenching of natural mode is achieved. A strong flame beating is observed on either side of this synchronization region. The flame transfer function (FTF) at fb is then estimated to delineate the strength of the beating. The FTF gain at fb shows different behavior on either side of the synchronization region. For ff >fn, the gain exhibits a local peak at low beating frequencies (∼20 Hz) which is consistent with the response of a stable laminar conical flame subjected to acoustic forcing at these frequencies. However, for ffn, negligible FTF gain is obtained at low beating frequencies, followed by a continuous increase as the beating frequency increases. This asymmetric behavior is further analyzed using proper orthogonal decomposition technique (POD). For ff>fn, the POD results at low fbshow that the flame base undergoes a strong flapping-like oscillation at the beating frequency. However for ff n, the flame base oscillates only at the natural mode of the combustor. This different beating behavior of the system can be attributed to the strong and weak thermoacoustic coupling, after and before the synchronization region, respectively.
KW - Beating
KW - Extinction
KW - Flame transfer function
KW - Thermoacoustic instability
UR - http://www.scopus.com/inward/record.url?scp=85139223460&partnerID=8YFLogxK
U2 - 10.1016/j.proci.2022.07.192
DO - 10.1016/j.proci.2022.07.192
M3 - Article
AN - SCOPUS:85139223460
SN - 1540-7489
VL - 39
SP - 3833
EP - 3842
JO - Proceedings of the Combustion Institute
JF - Proceedings of the Combustion Institute
IS - 3
ER -