1996 Fiscal Year Final Research Report Summary
Investigation of Microscopic Structures of Turbulent Diffusion Flames and Establishment of Analyzing Methods Taking Account of Elementary Kinetics
| Project/Area Number |
07455098
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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, Mechanical Engineering, Professor, 工学部, 教授 (40029096)
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| Co-Investigator(Kenkyū-buntansha) |
KINOSHITA Shinichi Osaka University, Mechanical Engineering, Research Associate, 工学部, 助手 (70263209)
KOMIYAMA Masaharu Osaka University, Mechanical Engineering, Assistant Professor, 工学部, 講師 (40178372)
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| Project Period (FY) |
1995 – 1996
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| Keywords | Turbulent Diffusion Flames / Extinction / Preferential Diffusion / Flame Curvature / Flame Temperature / Numerical Analysis / Laser-Rayleigh Scattering Method |
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| Research Abstract |
The purpose of this project is to make the models of turbulent combustion based on quantitative imaging by experimental observation of dynamic behavior of microscopic structures of disturbed diffusion flames by laser optical equipment and direct numerical simulation of unsteady flames. The result obtained through this project are as follows
(1) Instantaneous planar temperature profiles in turbulent diffusion flames with various Reynolds number at the exit nozzle were obtained by the laser Rayleigh scattering method using CCD camera with the image intensifier which has 512*512 pixels and the ND : YAG laser.
(2) The instantaneous maximum temperature tends to decrease when the average fuel velocity at nozzle exit increases. The temperature fluctuation appears at the inner region of the flame at low fuel velocity and the temperature fluctuation grows both of inner and outer region of the flame with increase of fuel velocity.
(3) In H_2/N_2-air laminar counter diffusion flames strained by stea
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dily impinging micro fuel from fuel side, Direct numerical simulation and two-dimensional temperature measurements by laser Rayleigh scattering method show that the flame strained by the micro fuel jet from the fuel side is easily quenched locally, but on the contrary, the flame strained from the air side hardly extinguishes and the flame temperature tends to increase.
(4) Numerical simulation taking into account detailed chemical kinetics and multicomponent diffusion attributes the phenomena described at (3) to dilution or concentration of H_2 of the fuel component due to the preferential diffusion-among species in relation to the flame curvature.
(5) In quasi-steady flame, the effect of preferential diffusion in relation to flame curvature is outstanding and this is mainly attributed to flame extinction, but as unsteadiness increases, the effect of preferential diffusion in relation to flame curvature becomes small.
(6) In unsteady flame, the flame sustain high temperature instantaneously in spite of extremely high stretch rate regime in which the steady flat flames cannot exist. The maximum flame temperature cannot be rationalized by the local stretch rate and changes widely depending on the unsteadiness effect. Less
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