1992 Fiscal Year Final Research Report Summary
A Study of the Thermo Fluid Dynamic Instability Focussing on the Formation and Dissipation of Turbulence in Diffusion Flames
| Project/Area Number |
03452130
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| Research Category |
Grant-in-Aid for General Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Research Field |
Thermal engineering
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| Research Institution | KYOTO UNIVERSITY |
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Principal Investigator |
IKEGAMI Makoto Kyoto University, Mech.Engr., Professor, 工学部, 教授 (70025914)
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| Co-Investigator(Kenkyū-buntansha) |
YAMANE Koji Kyoto University, Mech.Engr., Instructor, 工学部, 助手 (10210501)
SHIOJI Masahiro Kyoto University, Mech.Engr., Associate Professor, 工学部, 助教授 (80135524)
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| Project Period (FY) |
1991 – 1992
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| Keywords | Turbulent Diffusion Flame / Turbulent Eddy Structure / Laser Sheet Method / Vorticity Generation / Baroclinic Effect / Flame Boundary Deformation / Particle Image Velocimetry / Velocity Vector |
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| Research Abstract |
Formation and development of turbulent eddies in jet diffusion flames were investigated theoretically and experimentally. The main points of the present study consist of three parts as follows: (1) Visualization of the turbulent eddies in free jets and jet diffusion flames by a laser-light sheet method. (2) Numerical calculations for predicting formation and deformation of turbulent eddies from the standpoint of the thermo fluid dynamic instability. (3) Tests of the picture processing to analyze the turbulent flows. The obtained results are summarized as follows.
(1) The scale of eddies in the flame increases with the kinematic viscosity, and the eddies in the plane perpendicular to the jet axis have greater influence on air entrainment and fuel-air mixing than those of the shear layer in the axial direction. In the transient region, a hot and viscous soot layer are formed in the outer laminar region of the jet flame, in the inside of which a fuel flow is bent and is enlarged along the stream due to instability to produce the air-entrainment eddy.
(2) A less viscous jet core contains turbulent eddies which may produce vorticity near the laminar hot mantle due to interaction between density and pressure gradients, so called the baroclinic effect. This results in instability of the interfacial layer. Deformation and stretching of the flame boundary take place once the vorticity growth rate becomes stronger than that of dissipation due to viscosity.
(3) Particle image velocimetry is useful to determine the spatial distribution of instantaneous velocity vectors in the turbulent flowfield, and the obtained velocity vectors give the detailed information on turbulence in jet flows, such as profiles of vorticity, shear strain rate, and scale of turbulence.
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Research Products
(10 results)
