湍流扩散火焰的非稳态火焰面模拟

采用稳态的和非稳态的火焰面模型同时对一个湍流甲烷射流扩散火焰进行了数值模拟,比较了两者对湍流平均火焰结构、活性自由基和污染物(氮氧化物)排放的模拟效果。速度场采用κ-ε模型计算,守恒标量混合物分数的分布通过其概率密度函数(PDF)输运方程的求解得到。稳态的火焰面结构由查询火焰面数据库得到,而非稳态的火焰面结构由火焰面方程和流场方程耦合求解来计算。采用详细的GRI—Mech 3.0机理描述甲烷的氧化和氮氧化物的形成。数值模拟结果和实验数据作了广泛的对比,验证了火焰面模型对湍流扩散燃烧的定量模拟能力。

UNSTEADY FLAMELET MODELLING OF TURBULENT NON-PREMIXED FLAME

A turbulent methane jet diffusion flame is numerically simulated by using both steady and unsteady flamelet models. The modeling ability of the two models to represent the mean turbulent flame structures, active radicals and pollutant (nitric oxides) emissions is compared. The velocity field is calculated by using k ?e turbulence model and the conserved scalar mixture fraction is computed from its PDF transport equation. The steady flamelets are interpolated from the flamelet library, while the unsteady flamelets are obtained by solving the flamelet equations and flow field equations interactively. The detailed mechanism GRI-Mech 3.0 is incorporated to describe the methane oxidation and nitric oxides formation. The numerical results are compared with the experimental data extensively, and demonstrate the ability of flamelet models to predict the turbulent non-premixed combustion quantitatively.