TED-AJ03-600 NUMERICAL STUDY OF THE DYNAMIC STRUCTURE OF A BUOYANT TWO-DIMENSIONAL BLUFF-BODY JET DIFFUSION FLAME
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概要
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Non-premixed flame stabilized by a bluff-body combustor, such as occurs when a central fuel jet issues a surrounding annular air flow, is often used industrially. Such bluff-body combustors provide good flame stabilization as well as easy control of combustion. For non-premixed combustion in bluff-body burners, stabilization mechanism is mainly controlled by the interaction among combustible mixtures, air flow and hot combustion products. Exchange of species, momentum and energy becomes more intensive due to the existence of unsteady vortical structures behind the bluff-body surface. Therefore, a completed understanding of flow field in this region is very important for the study of flame stabilization. In the present study, we perform numerically the dynamic structure of a buoyant two-dimensional bluff-body jet diffusion CH_4-air flame in the transitional flow regime in a system as shown in Fig. A-1. The analysis is made by adopting the flame sheet model with infinite chemical reaction rate and [figure]unit Lewis number. Time-dependent compressible 2-dimensional Navier-Stokes equations are solved with the equation for coupling function by using a finite difference method. The Reynolds number of the air flow is varied from 0 to 600 for a fixed fuel Reynolds number of 230 under the fuel penetration regime. The recirculation zone depends on the air flow and also the flame position on the bluff-body surface markedly changes. That is, the flame position shifts from the inner edge of the bluff-body surface to the outer edge as the air flow increases. Under the present flow conditions, there are shear-driven vortices in the fuel flow inside the flame. The vortex frequency strongly depends on the air flow, but buoyancy effect is small. On the other hand, the frequency of buoyancy-induced vortices outside the flame has a little effect on the air flow, indicating that the buoyancy effect is dominant and responsible for the flame flicker as shown in Fig. A-2. Thus it is revealed that the presence of air flow modifies the nature of fuel flow through the flame.[figure]
- 一般社団法人日本機械学会の論文
著者
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NISHIMURA Tatsuo
Department of Mechanical Engineering,Yamaguchi University
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Kawahara Hideo
Department Of Mechanical Engineering Yamaguchi University
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Nishimura Tatsuo
Department Of Mechanical Engineering Yamaguchi University
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