| Project/Area Number |
09450093
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Thermal engineering
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| Research Institution | Osaka University |
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Principal Investigator |
TAKAGI Toshimi Osaka University, Graduate School of Engineering, Professor, 大学院・工学研究科, 教授 (40029096)
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| Co-Investigator(Kenkyū-buntansha) |
KINOSHITA Shinichi Osaka University, Graduate School of Engineering, Research Associate, 大学院・工学研究科, 助手 (70263209)
KOMIYAMA Masaharu Osaka University, Graduate School of Engineering, Assistant Professor, 大学院・工学研究科, 講師 (40178372)
OKAMOTO Tatsuyuki Osaka University, Graduate School of Engineering, Associate Professor, 大学院・工学研究科, 助教授 (40127204)
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| Project Period (FY) |
1997 – 1998
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| Project Status |
Completed (Fiscal Year 1998)
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| Budget Amount *help |
¥12,300,000 (Direct Cost: ¥12,300,000)
Fiscal Year 1998: ¥2,600,000 (Direct Cost: ¥2,600,000)
Fiscal Year 1997: ¥9,700,000 (Direct Cost: ¥9,700,000)
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| Keywords | Turbulent Diffusion Flames / Extinction / Preferential Diffusion / Flame Curvature / Flame Temperature / Numerical Analysis / Laser-Rayleigh Scattering Method / 再着火 |
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| Research Abstract |
The turbulent diffusion flame is supposed to be an ensemble of the laminar flamelets which should strained unsteadily and have positive or negative curvature, and be affected by preferential diffusion. In this study, transient laminar counterflow diffusion flames strained by unsteadily impinging micro air or fuel jet from air or fuel side were investigated. Two-dimensional time-dependent temperature measurements by laser Rayleigh scattering method showed the local flame extinction and reignition process. Time-dependent numerical computations taking into account detailed chemical kinetics and multicomponent diffusion predicted well the characteristics of the experimental evidence and revealed the processes dominating the transient behavior of the flame with respect to the flame curvature and preferential diffusion.
(1) Transient local flame extinction is observed where the micro jet impinges. During the process of the extinction, the transient flame can survive instantaneously under the quite high stretch rate where the steady flame cannot exist.
(2) Reignition is observed after the local extinction by the micro air jet impingement. The temperature after reignition becomes significantly higher than that of the original flame. This high temperature is induced by the H^2 concentration due to the preferential diffusion in relation to the concave curvature.
(3) The reignition is induced after the formation of combustible premixed gas mixture of high level of unreactedness and the consequent flame propagation.
(4) The reignition is hardly observed after the extinction by micro fuel jet impingement. This is due to the H^2 dilution due to the preferential diffusion in relation to the convex curvature.
(5) Flame structure with stretch/compression and periodic fluctuation was revealed.
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