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Exploring a critical diameter for thermo-acoustic instability of downward propagating flames in tubes
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| Title: | Exploring a critical diameter for thermo-acoustic instability of downward propagating flames in tubes |
| Authors: | Dubey, Ajit Kumar Browse this author | | Koyama, Yoichiro Browse this author | | Hashimoto, Nozomu Browse this author →KAKEN DB | | Fujita, Osamu Browse this author →KAKEN DB |
| Keywords: | Lewis number | | Acoustic parametric instability | | Primary acoustic instability | | Effect of geometrical parameters | | Growth rates |
| Issue Date: | 2021 |
| Publisher: | Elsevier |
| Journal Title: | Proceedings of The Combustion Institute |
| Volume: | 38 |
| Issue: | 2 |
| Start Page: | 1945 |
| End Page: | 1954 |
| Publisher DOI: | 10.1016/j.proci.2020.06.018 |
| Abstract: | 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. |
| Rights: | © <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/ | | http://creativecommons.org/licenses/by-nc-nd/4.0/ |
| Type: | article (author version) |
| URI: | http://hdl.handle.net/2115/86312 |
| Appears in Collections: | 工学院・工学研究院 (Graduate School of Engineering / Faculty of Engineering) > 雑誌発表論文等 (Peer-reviewed Journal Articles, etc)
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Submitter: 藤田 修
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