2023 Fiscal Year Final Research Report
Fundamental research on combustion characteristics of premixed flames focusing on spatial-temporal fluctuaion scale of fuel concentration
| Project/Area Number |
21K03910
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Multi-year Fund |
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| Section | 一般 |
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| Review Section |
Basic Section 19020:Thermal engineering-related
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| Research Institution | Iwate University |
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Principal Investigator |
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| Project Period (FY) |
2021-04-01 – 2024-03-31
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| Keywords | 燃焼 / 予混合火炎 / 成層濃度場 / 火炎伝播 / 消炎 / ルイス数効果 / 選択拡散効果 / バックサポート効果 |
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| Outline of Final Research Achievements |
The influence of Lewis number and selective diffusion on the combustion characteristics of lean methane/air and propane/air flames to sinusoidal oscillation of equivalence ratio was investigated. The oscillation frequency of the equivalence ratio was from 5 to 50 Hz. At 5 Hz, both flames exhibit quasi-static behavior. At 20 Hz, differences appeared in the response characteristics of CH radical emission (∝ heat generation rate) of flame depending on the type of fuel (Lewis number of the mixture). At 20 Hz, local extinction and re-ignition were observed at the center of the propane flame when the equivalence ratio oscillation amplitude φa was amplified. For both flames, a lag time τ appeared before the flame was completely extinguished. At 40 Hz, even if the amplification factor of φa was increased, the τ of the methane and propane flames did not change due to the back support effect, and these lean flammability limit expanded.
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| Free Research Field |
燃焼工学
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| Academic Significance and Societal Importance of the Research Achievements |
本研究における当量比の変動周波数は，5～50Hzであり，エンジン内の濃度変動をミクロ的な視点でとらえた場合，低い周波数域である．この周波数域において，濃度変動火炎に特有のルイス数効果と選択拡散効果が反応速度と比例関係にあるCHラジカル発光強度の応答に出現したことは発見である．また，プロパン火炎では火炎の中央に穴が開く局所消炎と再着火が観察されたのに対し，メタン火炎ではこのような局所消炎は見られなかった点は，濃度変動に対する壁面よどみ流や対向流予混合火炎の数値研究において捉えることができていない特筆すべき事項であり，燃焼学界における学術的意義は大きい．
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