湍流贫燃预混射流火焰的大涡模拟

Large Eddy Simulation of Turbulent Lean Premixed Jet Flame

关键词:  值班预混射流火焰  大涡模拟  自点火模型  假定概率密度函数模型

Key words:  Piloted premixed jet flame  Large eddy simulation  Autoignition model  Presumed probability density function model

摘要:

为了研究高Karlovitz([Ka])数下湍流预混火焰的驻定机制和火焰结构，采用化学热力学建表方法结合假定概率密度函数(PDF)模型，对值班预混射流火焰(PPJB)进行大涡模拟(LES)研究。选取自点火模型作为建表模型，使用假定PDF模型考虑湍流和化学反应之间的相互作用，其中假定双混合物分数的概率密度分布为Dirichlet分布，反应进度变量的概率密度分布为[β]分布。模拟结果表明，能较好预测PPJB火焰的温度和主要组分的分布。使用中间组分([CO]和[OH])的质量分数来定性描述PPJB火焰结构，结果表明高[Ka]数下火焰结构受到湍流涡旋的显著影响。

Abstract:

Chemistry tabulation combined with presumed probability density function (PDF) was applied to investigate the stabilization mechanism and flame structure of piloted premixed jet burner (PPJB) with high Karlovitz ([Ka]) number using large eddy simulation (LES). Thermo-chemistry states were tabulated using the autoignition model. Presumed PDF was used to involve the interaction of turbulence and chemistry. Dirichlet distribution was applied for the joint PDF of the two mixture fractions，and beta PDF was used to model the reaction progress variable distribution. The LES results show that distribution of temperature and mass fractions of major species are in good agreement with the experimental data. The mass fractions of intermediate compositions ([CO] and [OH]) were applied to describe the flame structures qualitatively，and it is found that the turbulence eddies can affect the inner flame structures with high [Ka] number.