湍流预混火焰LES/FDF模拟中标量混合时间尺度建模  

An Investigation of Scalar Mixing Timescale Modelling in LES/FDF Simulations of Turbulent Premixed Flames

作　　者：杨天威 尹钰 周华[2] 任祝寅[2] YANG Tian-Wei;YIN Yu;ZHOU Hua;REN Zhu-Yin(School of Aerospace Engineering,Tsinghua University,Beijing 100084,China;Institute for Aero Engine,Tsinghua University,Beijing 100084,China)

机构地区：[1]清华大学航天航空学院,北京100084 [2]清华大学航空发动机研究院,北京100084

出　　处：《工程热物理学报》2021年第10期2749-2755,共7页Journal of Engineering Thermophysics

基　　金：国家自然科学基金资助项目(No.91841302)。

摘　　要：在实际应用中,精确模拟高湍流度预混火焰十分关键但极具挑战性。本文将被动标量混合时间尺度动态封闭方法与hybrid混合时间尺度模型结合,在湍流预混火焰LES/FDF模拟中提出一种新的标量混合时间尺度建模方法。该方法不需要人为选取混合模型参数CM,且动态地考虑了由湍流和火焰结构分别引起的亚网格标量混合。对悉尼值班预混射流燃烧器高湍流度PM1-150火焰进行了LES/FDF模拟。结果表明,新模型显著改善了对整体燃烧进程的预测结果,正确地预测了局部熄火/再燃现象。进一步的结果显示,模型参数CM明显大于在RANS框架下量级为1的常用取值,这表明该参数在不同框架下具有不同的物理内涵。Predictive simulations of highly turbulent premixed flames are crucial though challenging for practical applications.In this study,a new closure of the scalar mixing timescale is formulated to enhance the predictability of large eddy simulation(LES)/filtered density function(FDF)simulations for turbulent premixed flames.Specifically,the new model integrates a dynamic subgrid closure for turbulence-induced micro-mixing with a hybrid mixing timescale model.It requires no tuning for the mixing model parameter C_(M) and can dynamically consider contributions to subgrid mixing from turbulence and reaction respectively.Model evaluation is performed in LES/FDF simulations of the highly turbulent Sydney piloted premixed jet burner(PPJB)PM1-150 flame.It shows that the new model notably improves the predictions for the overall combustion progress and correctly predict the local extinction/re-ignition trend.Results further show that the mixing model parameter is significantly larger than the typical value(order of unity)used in Reynolds-averaged framework,highlighting the difference of the physical interpolation for this parameter.

关 键 词：湍流预混火焰 输运概率密度函数方法 反应标量混合 小尺度混合模型 混合时间尺度 

分 类 号：TK16[动力工程及工程热物理—热能工程]