摘要
在径向浓淡旋流煤粉燃烧器单相冷态试验的基础上 ,充分考虑旋转对湍流流场的影响 ,采用 k-ε双方程及其修正模型和二阶矩雷诺应力模型 (DSM) ,对旋流煤粉燃烧器出口强旋流场进行了数值模拟。数值计算结果表明 :k-ε双方程模型定性上可以预报出强旋流场的主要特点 ,但回流区的预报区域偏大 ,轴向速度的预报结果与试验值有一定差距 ,预报的回流速度偏低 ,速度衰减过快 ,这是由于 k-ε湍流模型采用了较多的简化和未考虑旋转对湍流的影响。采用基于旋转体系使湍流脉动加强和削弱两种作用的修正方法对 k-ε双方程的湍流耗散率方程进行修正。计算结果表明 :从旋转体系可使湍流能量加强出发的 Bardina涡量修正方法 ,预报回流区范围较标准 k-ε湍流模型缩小 ,更加接近于试验值。其计算结果优于使湍流脉动削弱的 Richardson修正。DSM模型对轴向回流速度和切向速度后期分布预报结果较上述模型有较大改善 ,可体现出湍流雷诺应力非均匀各向异性的特点 ,虽然此模型仍有收敛速度慢、计算时间长的缺点 ,但对预报强旋流动是一个精度较高、极具潜力的方法。图 9参 1
Based on the experimental studies on isothermal jet, standard k ε turbulent model, its modified equations, and second order DSM model are used to predict the strong swirling single phase aerodynamic field of the Radial Bias Combustion burner. Numerical simulation results show that standard k ε model can correctly predict the flow field in quality. However, there are quantitative differences in Internal Recirculation Zone (IRZ) size and reversed flow velocity owing to the oversimplified model and overlook of effects of swirl. According to effects of destabilization and stabilization of rotating system, two modifications are proposed to correct ε equation of standard k ε model. One is Bardina vorticity modification, and the other is Richardson modification. Prediction results show that Bardina method has a superior capacity to Richardson modification. It reflects the strong mixing effects and predicts the size of IRZ more precisely. Since DSM model has improved predictive results of the reversed velocity and tangential velocity, it is a potential method to predict strong swirling nonisotropic turbulent flow instead of the longer convergence time. Fings 9 and refs 11.
出处
《动力工程》
CSCD
北大核心
2002年第3期1750-1758,共9页
Power Engineering
