| Project/Area Number |
21K03858
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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 19010:Fluid engineering-related
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| Research Institution | Hiroshima University |
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Principal Investigator |
Ogata YOICHI 広島大学, 先進理工系科学研究科(工), 准教授 (10323792)
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| Co-Investigator(Kenkyū-buntansha) |
西田 恵哉 広島大学, 先進理工系科学研究科(工), 名誉教授 (90156076)
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| Project Period (FY) |
2021-04-01 – 2024-03-31
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| Project Status |
Completed (Fiscal Year 2023)
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| Budget Amount *help |
¥3,900,000 (Direct Cost: ¥3,000,000、Indirect Cost: ¥900,000)
Fiscal Year 2023: ¥780,000 (Direct Cost: ¥600,000、Indirect Cost: ¥180,000)
Fiscal Year 2022: ¥1,040,000 (Direct Cost: ¥800,000、Indirect Cost: ¥240,000)
Fiscal Year 2021: ¥2,080,000 (Direct Cost: ¥1,600,000、Indirect Cost: ¥480,000)
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| Keywords | 脈動流 / 気液界面 / 数値シミュレーション / 液滴 / 気液二相流 / 流体不安定性 / 微粒化 / モデリング / エンジン |
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| Outline of Research at the Start |
自動車エンジン内の吸排気系や原子炉等の管内を流れる，液膜と気流との相互作用で生じる飛散液滴群は液滴のサイズ・質量分布の範囲が幅広く，計算格子サイズより小さい微小粒径群を統計的な評価に基づいて適切にモデル化した液相・気相の相互解析が必要となる．
本研究では基本形状の直管・曲り管における気液界面挙動を，多数の実験結果から時間・空間変動を考慮した評価を行い，時間変動・形状もより複雑な実機エンジンの実用的・高精度シミュレーションの実現を目指した数値モデル構築を行う．
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| Outline of Final Research Achievements |
Experimental measurements and evaluations were made to construct numerical models for multiple droplets generated in airflow fields in straight and curved pipes. Large amplitude waves are generated in the local gas-phase acceleration region at the curved inlet, and breakup with large droplet size and short breakup time occurs even at gas velocities where no breakup occurs in straight pipes. However, no breakup occurred in the separation where the air decelerates in the bend, indicating that the splitting conditions in the straight pipe can be applied locally in the bend.
Under pulsating flow, breakup occurs during the time when the air velocity is faster than the splitting onset velocity of the steady flow. It is found that the pulsation period and hydrodynamic breakup time, and gas velocity during pulsation acceleration and the flow velocity at the onset of splitting, and the time-averaged gas velocity affect droplet size distribution and splitting morphology.
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| Academic Significance and Societal Importance of the Research Achievements |
これまでの直管での気液界面飛散分裂研究と併せて，本研究で得られた直管・曲管での気流・液膜における飛散分裂の発生機構，液膜分裂時間などの統計評価データ，および脈動流条件での気相速度振幅・時間平均流速・脈動周期・管形状が液滴群の飛散分裂挙動に及ぼす影響のメカニズムは，今後実機での吸排気系における高温気流中の蒸発の影響，近年研究が発展しているCFDへのデータ同化にも応用が期待出来る．
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