钝体驻定燃烧器冷态和燃烧场的LES研究

LES of the Nonreaction and Reaction Fields of the Bluff-Body Burner

本文采用LES结合FPV湍流燃烧模型数值模拟了钝体驻定火焰的冷态场和燃烧场,与实验数据进行比较,研究了火焰结构和流场特性,并分析了燃烧对流场的影响。结果表明,速度、温度和主要组分浓度的一阶和二阶统计值,均与实验值符合得较好。燃烧发生在当量混合物分数等值线处,先是沿回流区外边缘分布,然后逐渐向中心靠拢,最后在下游处类似于射流火焰。回流区前部当量混合面处的低标量耗散率和高温分布在钝体驻定火焰中起到了关键的作用。燃烧使气体发生膨胀,回流区变长,轴向平均速度和湍动能沿流向衰减速度降低,湍动能在内剪切层处的峰值降低。

Large eddy simulations combined with Flamelet/progress variable combustion model are performed to the nonreaction and reaction fields of bluff-body stabilized burner.The numerical results are compared with experimental data and applied to analyze the flame structures,flow characteristics and influences combustion having on the flow field.Numerical results of velocities,temperature and mass fractions of main species agree well with experimental ones.Flames happen around the stoichimetric mixture fraction,then move toward the centerline and become similar to the jet flame downstream.The high temperature and low scalar dissipation rate in the front of the recirculation region play important roles in the stabilization of flames.When combustion happens,gas expands at the high temperature and the recirculation zone becomes longer.The decay rates of velocities along the stream are smaller and the peak value of turbulent kinetic energy in the inner shear layer is also smaller.