Exploring a critical diameter for thermo-acoustic instability of downward propagating flames in tubes

Dubey, Ajit Kumar; Koyama, Yoichiro; Hashimoto, Nozomu; Fujita, Osamu

Exploring a critical diameter for thermo-acoustic instability of downward propagating flames in tubes

Dubey, Ajit Kumar; Koyama, Yoichiro; Hashimoto, Nozomu et al.

Proceedings of The Combustion Institute, 2021, 38(2), 1945-1954

Permalink : https://hdl.handle.net/2115/86312

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アクセス権	open access
URI	https://hdl.handle.net/2115/86312
タイトル	Exploring a critical diameter for thermo-acoustic instability of downward propagating flames in tubes
著者	Dubey, Ajit Kumar ; Koyama, Yoichiro ; Hashimoto, Nozomu ; Fujita, Osamu
著者名 Dubey, Ajit Kumar
著者名 Koyama, Yoichiro
e-Rad_Researcher 70392751 著者名 Hashimoto, Nozomu
e-Rad_Researcher 10183930 著者名 Fujita, Osamu
言語	英語
キーワード	Lewis number
	Acoustic parametric instability
	Primary acoustic instability
	Effect of geometrical parameters
	Growth rates
発行日	2021
出版者	Elsevier
収録物名	Proceedings of The Combustion Institute
巻(号)	38(2)
ページ	1945-1954
抄録	Thermo-acoustic oscillations are observed when a flame ignited at open end of a tube propagates towards the closed end due to interaction between unsteady heat release rate fluctuations from flame and acoustic fluctuations. In our past work, it was found that thermo-acoustic instability increases with decreasing diameter from 7.0 cm to 3.0 cm. A recent study in flame propagation in Hele & ndash;Shaw cells showed that thermo-acoustic instability is not observed for plate separation less than or equal to 0.4 cm. Thermoacoustic instabilities cannot be observed in very narrow tubes due to excessive damping from the wall. This opens up the possibility of a critical diameter where thermo-acoustic instability would be maximum. In this work we perform flame propagation experiments with diameter of combustion tube in the range 0.5 cm to 3 cm for a fixed length of 70.2 cm. It was found that thermo-acoustic parametric instability begins at lowest laminar burning velocity when the diameter is around 1.0 cm. This diameter is termed as critical diameter. Critical diameter is found to be independent of Lewis number of mixtures. Existence of a critical diameter is thus proved experimentally. Growth rates of primary instability increase with decreasing diameter and show a maximum around the critical diameter and decrease with further decrease in tube diameter. But, growth rates of secondary instability as well as maximum pressure fluctuation amplitude decreases continuously with decreasing diameter. Mechanisms responsible for these observations and existence of a critical diameter are clarified.
資源タイプ	学術雑誌論文
出版タイプ	Accepted Manuscript
権利情報	Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International
権利情報	© <2021>. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/
PISSN	1540-7489
関連情報 (isVersionOf)	出版社版DOI https://doi.org/10.1016/j.proci.2020.06.018