| Summary: | 碩士 === 逢甲大學 === 材料與製造工程所 === 91 === In this study, the computational fluid dynamics program, PHOENICS, were used to simulate the mixing flow field of a cylindrical afterburner with sudden-expansion ratio 2:1 and twin side jets. The various configurations of jets and the change of momentum flux ratio between the mainstream and jets on the effects of the mixing rate were considered. The standard κ-εtwo-equation turbulence model associated with wall function are used to describe the turbulent structure. The control-volume integration formula for finite difference and SIMPLE-C algorithm are employed to simulate the flow field.
For the sudden-expansion cylindrical confined flow field, the entrainment effect near the walls and the jet impingement make the mixing rate increasing.Basically, the structure of a transverse jet is dominated by a pair of counter-rotating vortices; however, for jets with high momentum, the interactions among the vortices and confined wall are make the counter-rotating vortices more strong, and make it becomes a large vortices either mixing the jets and cross flow. When the jets is staggered in the opposed direction, the best mixing rate occurred on J=2. The mixing rate of opposite jets is better then the staggered opposed jets.
From the results of this simulation, we obtained the better configuration of jets and the momentum flux ratio for better mixing rate to avoid the waste of energy. By investigate the results of velocity and temperature distributions of the flow field, we could redesign the afterburner to reducing the size
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