燃气涡轮带肋冷却通道流动与换热的大涡模拟

为研究涡轮内部扰流肋结构的流动和传热机理,分别采用雷诺平均(RANS)方法和大涡模拟(LES)方法对肋通道周期性计算域和全尺寸计算域进行数值研究;结合实验数据,对比分析雷诺平均方法和大涡模拟在流动和换热方面的准确性.结果表明:大涡模拟捕捉到了肋顶扁平涡结构的产生与脱落过程,该旋涡在近似肋顶面的高度和下游空间内发展并掺混,强度逐渐衰减,该过程与湍流强度的分布规律一致;获得了肋前分离流动中向侧壁面偏转的横向二次流等更加详细的流场结构,更加真实地反映了流场的特性;在流动预测方面,大涡模拟更加准确地预测到了平均速度分布和脉动量湍动能的分布规律;在换热方面,大涡模拟方法对换热增强系数的预测误差比雷诺平均方法要小.

Numerical research of flow and heat transfer in a ribbed channel based on les approach

To analyze a problem of typical blade internal cooling, the periodic case and full spatial case were computed using RANS and large eddy simulation(LES) approaches. The precision of two types of numerical method in predicting flow and heat transfer was compared based on the experimental data published. Numerical research shows that the process of initiation and shedding of the small flattened vortex, which is on the top surface of the rib, was detected by using LES approach, and the phenomenon, that the shedding vortex mixes with other coherent structure when moving along the trace at the height of the top surface of the rib, is accordant with the trend of turbulence intensity variation. The detailed flow structures reflect the true characteristic of the flow and show that not only the parameters of flow condition, including the mean velocity distribution and the turbulent intensity, but also the distribution of enhance factor predicted by LES approach are accordant with experimental data. The prediction error of enhance factor of heat transfer by RANS approach is smaller than that by LES approach.