レーザー照射法による管内下方伝播火炎の変形が燃焼不安定性におよぼす影響

• 資料種別: 博士論文
• タイトル: レーザー照射法による管内下方伝播火炎の変形が燃焼不安定性におよぼす影響
• 著者・編者: Nguyen Truong Gia, Tri
• 著者標目: Nguyen Truong Gia, Tri
• 出版事項: Hokkaido University
• 出版年月日等: 2021-03-25
• 出版年（W3CDTF）: 2021-03-25
• 並列タイトル等: Effect of Flame Deformation of Downward Propagating Flames Induced by Laser Irradiation Method on its Combustion Instability
• 寄与者: 藤田, 修; 永田, 晴紀; 大島, 伸行; 橋本, 望
• 授与機関名: 北海道大学
• 授与年月日: 2021-03-25
• 授与年月日（W3CDTF）: 2021-03-25
• 報告番号: 甲第14433号
• 学位: 博士(工学)
• 博論授与番号: 甲第14433号
• 本文の言語コード: eng
• 件名標目: Parametric instability; Single laser irradiation; Double laser irradiation method; Flame structures; Diffusive-thermal instability
• NDC: 500
• 対象利用者: 一般
• 一般注記: (主査) 教授 藤田 修, 教授 永田 晴紀, 教授 大島 伸行, 准教授 橋本 望; 工学院（機械宇宙工学専攻）
• DOI: 10.14943/doctoral.k14433; https://doi.org/10.14943/doctoral.k14433
• 国立国会図書館永続的識別子: info:ndljp/pid/12219060; https://dl.ndl.go.jp/pid/12219060
• コレクション（共通）: 障害者向け資料
• コレクション（障害者向け資料：レベル1）: テキストデータ
• コレクション（個別）: 国立国会図書館デジタルコレクション > デジタル化資料 > 博士論文; https://dl.ndl.go.jp/collections/A00014
• 収集根拠: 博士論文（自動収集）
• 受理日（W3CDTF）: 2022-04-04T15:10:33+09:00
• 記録形式（IMT）: PDF
• オンライン閲覧公開範囲: 国立国会図書館内限定公開
• デジタル化資料送信: 図書館・個人送信対象外
• 遠隔複写可否（NDL）: 可
• 掲載誌（URI）: https://doi.org/10.14943/doctoral.k14433; http://hdl.handle.net/2115/84470
• 参照（URI）: http://hdl.handle.net/2115/81325
• 連携機関・データベース: 国立国会図書館 : 国立国会図書館デジタルコレクション; https://dl.ndl.go.jp

• 要約等: Thermo-acoustic instabilities result from complex dynamic interactions between heat release fluctuation from flame and acoustic oscillation filed. Thermo-acoustic instabilities are often destructive to the operation of combustion systems and are major challenge in the development of lean premixed combustors with ultra-low emissions. Therefore, Numerous researches have been conducted to understand the mechanisms of the thermo-acoustic instabilities. Of these, a simple experiment to generate and study thermo-acoustic instabilities is a downward-propagating flame in an open-closed tube. Flames propagating in tubes with specific structure can spontaneously produce acoustic oscillations. A parametric instability represented by corrugated flame is transitioned from a vibrating flat flame which is subjected to a primary acoustic instability. According to a theoretical velocity coupling, the variation of flame surface area during propagation in tubes is theoretically studied to show a proportional effect to the growth rate of thermo-acoustic instabilities. This effect can be studied more precisely if flame structure is actively controlled. In previous studies, a single CO2 laser irradiation (SLI) method was extensively used to artificially control the flame shape. In this thesis, a double laser irradiation (DLI) method is developed based on the SLI setup. A single or a double cellular structure is formed when a flat flame is exposed to the SLI or DLI, respectively. As a spatially sinusoidal shape is formed, the cellular structure is characterized by the amplitude of the cell (𝑎) and wavenumber (𝑘) as a function of wavelength, 𝑘=2𝜋/𝜆. Consequently, at a given laminar burning velocity and using the same total laser power, different coupling parameter 𝑎 and 𝑘 of the cellular structures propagating under SLI and DLI would generate different thermo-acoustic responses. These responses can be comparatively examined to develop a more comprehensive criterion for the transition from primary acoustic instability to parametric instability. Hence, the structure of the laser-induced flames and their effect on the growth of acoustic pressure fluctuations are discussed to clarify the criteria of the transition from primary acoustic instability to parametric instability. In Chapter 1, the nature and the physics of thermo-acoustic instability were briefly reviewed. In addition, the flame acoustic coupling in combustion tube were presented. Then, the objective and the scope of this study were introduced. In Chapter 2, the experimental setup of the SLI and DLI how the laser beams are directed into the combustion tube were described. The properties and compositions of gasmixtures were specified. Then the experimental procedure to obtain the flame propagation induce by laser irradiation and acoustic pressure fluctuation was revealed. In Chapter 3, effect of flame surface area (as a function of 𝑎 and 𝑘) of downward propagating flames induced by SLI and DLI on transition from primary acoustic instability to parametric instability was clarified. The effect was revealed through an experimental comparison on the criteria of transition to parametric instability of flame when it is exposed to SLI and DLI. The distance between two beams in the DLI setup is fixed at 18 mm. The results showed that the growth rate of primary acoustic instability during the propagation of the deformed flame is important to enhance the pressure fluctuation amplitude that further reaches the critical value for the transition to parametric instability. Furthermore, a linear relationship was found between the area of the deformed structure (irrespective of its dimension) and the corresponding growth rate of acoustic pressure fluctuation during the propagation of the deformed flame. Using the DLI method, the actual flame area, rather than (𝑎𝑘)2 as mentioned in the velocity coupling, was found to be the factor that determines the growth rate under nonhomogeneous cell distribution. In Chapter 4, the effect of geometric deformed structures induced by DLI on the growth rate thermo-acoustic instability was presented. The experiments were conducted at a given laser power and laminar burning velocity while the distance between the beams is varied from 12 mm to 21 mm with interval of 3 mm. When the beam separated distance was smaller than 18 mm, individual cell was merged together, the laser-induced structures were no longer in the form of sinusoidal shape as an overlapping region was emerged between two superimposed cells. This resulted a difference effect on growth rate of acoustic pressure with non-sinusoidal and sinusoidal structure. In fact, the appearance of curvature at overlapping region gave an effect that contributed to the growth rate of thermo-acoustic instability during the propagation of deformed flame. Therefore, relationship between the flame area and the growth rate acoustic pressure fluctuation was not linear as found in the experiments discussed in the chapter 3 where all the geometric structures of deformed flame are the sinusoidal shape. Based on that, the contribution of curvature effect is determined. The result found that curvature effect of overlapping region had limited contribution to the total growth rate of acoustic pressure. And the flame surface area of laser-induced flame is confirmed to be the factor control the growth rate of thermo-acoustic instability. In Chapter 5, a summary of finding in the present study and conclusion were given.
• DOI: 10.14943/doctoral.k14433; https://doi.org/10.14943/doctoral.k14433
• 記録形式（IMT）: application/pdf
• 一次資料へのリンクURL: Nguyen_Truong_Gia_Tri.pdf （fulltext）; https://eprints.lib.hokudai.ac.jp/repo/huscap/all/84470/Nguyen_Truong_Gia_Tri.pdf
• オンライン閲覧公開範囲: インターネット公開
• 参照（URI）: HDL; https://hdl.handle.net/2115/81325
• 連携機関・データベース: 国立情報学研究所 : 学術機関リポジトリデータベース（IRDB）（機関リポジトリ）; https://irdb.nii.ac.jp
• 提供元機関・データベース: 北海道大学 : 北海道大学学術成果コレクション