两种亚网格燃烧模型的旋流扩散燃烧大涡模拟

Large-eddy simulation of swirling diffusion combustion using two SGS combustion models

关键词:  湍流燃烧  二阶矩燃烧模型+  大涡模拟+  旋流燃烧

Key words:  Turbulent combustion  Second-order moment combustion model~+  Large-eddy simulation~+  Swirl combustion

摘要:

用二阶矩亚网格(SOM-SGS)燃烧模型和文献中的涡旋破碎亚网格(EBU-SGS)燃烧模型,对甲烷-空气旋流扩散燃烧进行了大涡模拟,将二者得到的LES统计平均温度分布和实验结果以及用二阶矩燃烧模型的统观模拟(RANS-SOM)结果比较,表明LES-SOM和RANS-SOM的模拟结果都和实验符合较好,而LES-EBU的模拟结果和实验不符合,在不同区域内高估或者低估了燃烧温度。其原因是由于EBU模型不能有效地考虑有限反应动力学的作用。LES-SOM模拟的瞬态结果显示了旋流扩散火焰的湍流大涡结构不同于射流火焰的特点。

Abstract:

The methane-air swirling diffusion combustion was studied by large-eddy simulation(LES) using a Smagorinsky-Lilly sub-grid-scale(SGS) turbulence model,a second-order moment(SOM) sub-grid-scale(SGS) combustion model,proposed by the present authors,and an eddy-break-up(EBU) combustion model used by some investigators.The LES statistical results are compared with the experimental results and the Reynolds-averaged Navier-stokes(RANS) modeling results using the Reynolds stress equation model and the secondorder moment(SOM) combustion model.Both SOM-SGS combustion model and RANS-SOM model give the results in good agreement with the experimental results,but the LES-EBU modeling results are not in agreement with the experimental results.In different regions the LES-EBU model over-predicts or under-predicts the temperature.The reason is that the effect of chemical kinetics is not taken into account in the LES-EBU modeling.The LES instantaneous results show that the size and range of large vortex structures in swirling combustion are different from those of the jet combustion.