湍流非预混射流火焰倾斜冲击壁面的直接数值模拟研究

Study of Turbulent Non-Premixed Slot-Jet Flame Obliquely Impinging at Flat Wall Using Direct Numerical Simulation

采用直接数值模拟方法,选取17组分、73步简化的甲烷化学反应机理,对三维湍流平面甲烷射流火焰倾斜冲击壁面进行了研究.分析了相同湍流强度、不同Damköhler数的两个算例.两个算例出现了不同程度的熄火,算例B的熄火现象比算例A更明显.同时,观察到当量混合分数等值面的凸起结构与火焰熄火现象存在一定关联.定量分析了火焰面平均曲率与熄火的相关性,发现在剪切流动中熄火区域的平均曲率大于燃烧区域的平均曲率;在壁面附近的熄火区域曲率的大小与壁面熄火模式相关.

In this paper,the three-dimensional turbulent planar methane slot-jet flame obliquely impinging at a wall was simulated using direct numerical simulation(DNS),in which a 17-species 73-step reduced mechanism for methane chemical reaction was selected.Two cases(A and B)with the same turbulence intensity but different Damköhler numbers were analyzed.It was observed that the extinction of different degrees occurred in both cases,and the extinction event in Case B was more significant than that in Case A.Meanwhile,the flame extinction event was correlated to the bulge structure on the stoichiometric mixture fraction iso-surface.The correlation between the mean curvature of the flame surface and the extinction event was quantitatively analyzed,and it was found that in the shear layers,the value of mean curvature in the extinction regions was larger than that in the burning regions.In addition,this value in the near-wall extinction region was correlated to the extinction mode.