Influences of heat release, blockage ratio and swirl on the recirculation zone behind a bluff body
Influences of heat release, blockage ratio and swirl on the recirculation zone behind a bluff body
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DOI：
10.1080/00102202.2022.2041616
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发表时间：
2022-02
影响因子：
1.9
通讯作者：
D. P. Kallifronas;P. Ahmed;J. Massey;M. Talibi;A. Ducci;R. Balachandran;N. Swaminathan;K. Bray
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文献类型：
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作者：
D. P. Kallifronas;P. Ahmed;J. Massey;M. Talibi;A. Ducci;R. Balachandran;N. Swaminathan;K. Bray
摘要：通过旋流中的涡流破坏机制产生的再循环区对于实际燃烧系统中湍流火焰的空气动力学稳定起着至关重要的作用。该区域与上游钝体的中央再循环区域 (CRZ) 相互作用，从而导致复杂的流动行为，该流动行为取决于堵塞比和旋流数。先前观察到涡流破裂气泡（VBB）在大旋流数或阻塞比时与 CRZ 合并。本研究通过一系列涡流钝体稳定预混火焰的大涡模拟和实验，探讨了放热对这种流动结构的影响及其物理机制。模拟结果与测量结果的比较很好。据观察，在等温流中，随着旋流数或阻塞比的增加，涡流破裂气泡向上游移动，其平均结构发生变化。由于膨胀，涡流破裂气泡被推向下游，热释放的影响导致流动特性的显着差异。在相同堵塞率的反应流中，观察到 VBB 和 CRZ 合并的临界涡流数更高。
ABSTRACT The recirculation zone created through vortex breakdown mechanisms in swirling flows plays a vital role for aerodynamic stabilization of turbulent flames in practical combustion systems. This zone interacts with the central recirculation zone (CRZ) of an upstream bluff body and this leads to a complex flow behavior that depends on the blockage ratio and swirl number. It has been previously observed that the vortex breakdown bubble (VBB) merges with the CRZ at large swirl number or blockage ratio. In this study, the influences of heat release on this flow structure and their physical mechanisms are explored through a series of large eddy simulations and experiments of bluff body stabilized premixed flames with swirling flows. Comparisons of simulation results with measurements are good. It is observed that in isothermal flows, as the swirl number or blockage ratio is increased, the vortex breakdown bubble moves upstream and its mean structure changes. The effect of heat release leads to considerable differences in the flow characteristics as the vortex breakdown bubble is pushed downstream due to dilatation. The critical swirl number, at which the VBB and CRZ merge, is observed to be higher in reacting flows for the same blockage ratio.