Large-Eddy Simulation of Interactions Between a Reacting Jet and Evaporating Droplets
Large-Eddy Simulation of Interactions Between a Reacting Jet and Evaporating Droplets
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DOI：
10.1007/s10494-007-9084-4
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发表时间：
2008
期刊：
影响因子：
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通讯作者：
J. Xia;K. Luo;Suresh Kumar
中科院分区：
文献类型：
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作者：
J. Xia;K. Luo;Suresh Kumar
采用大涡模拟方法对有、无蒸发液滴的反应射流进行了数值模拟，研究了湍流、燃烧、传热和蒸发之间的相互作用。混合欧拉-拉格朗日方法用于气液流动系统。该化学反应采用Arkenius型有限速率化学。为了捕获高度本地化的相互作用，动态程序被用于所有的subgrid-scale模型，除了过滤的反应速率模拟的规模相似性模型。模拟了具有不同初始液滴尺寸（St 0）和质量负载比（MLR）的各种代表性情况，沿着没有液滴的情况。发现与较大的、响应慢的液滴（St 0 = 16）相比，较小的液滴（St 0 = 1）由于其在反应区中的优先集中而在抑制燃烧方面更有效。温度波动的峰值温度和强度被发现在所有的液滴的情况下，在不同程度上取决于液滴的属性降低。详细分析了网格尺度动能输运方程中各项的贡献，结果表明：液滴蒸发对网格尺度动能输运方程的影响很小，而液滴动量效应依赖于St 0.当MLR足够高时，较大的液滴（St 0 = 16）可以对GSKE产生深远的影响，从而对大尺度流动结构的形成和演变产生影响。另一方面，湍流水平被发现是较低的液滴的情况下比在纯火焰的情况下，由于耗散液滴动力学效应。
Large-eddy simulation of a turbulent reactive jet with and without evaporating droplets is performed to investigate the interactions among turbulence, combustion, heat transfer and evaporation. A hybrid Eulerian–Lagrangian approach is used for the gas–liquid flow system. Arrhenius-type finite-rate chemistry is employed for the chemical reaction. To capture the highly local interactions, dynamic procedures are used for all the subgrid-scale models, except that the filtered reaction rate is modelled by a scale similarity model. Various representative cases with different initial droplet sizes (St0) and mass loading ratios (MLR) have been simulated, along with a case without droplets. It is found that compared with the bigger, slow responding droplets (St0= 16), smaller droplets (St0= 1) are more efficient in suppressing combustion due to their preferential concentration in the reaction zones. The peak temperature and intensity of temperature fluctuations are found to be reduced in all the droplet cases, to a varying extent depending on the droplet properties. Detailed analysis on the contributions of respective terms in a transport equation for grid-scale kinetic energy (GSKE) shows that the droplet evaporation effect on GSKE is small, while the droplet momentum effect depends onSt0. When theMLRis sufficiently high, the bigger (St0= 16) droplets can have profound influence on GSKE, and consequently on the formation and evolution of large-scale flow structures. On the other hand, the turbulence level is found to be lower in the droplet cases than in the pure flame case, due to the dissipative droplet dynamic effect.