Abstract: Large eddy simulation was used to investigate the influence of rotation on film cooling. Film cooling over flat plate with 30^o streamwise inclined cylinder hole which had experimental data for comparison was chosen to represent the suction side of turbine rotor blade. The Reynolds number at the jet exit was 1300, and the blowing ratio was 0.5. The flow field and heat transfer without rotation and with rotating number of 0.2 were calculated. The effect of rotation was comprehensively observed by showing the variation of mean flow field, voriticity, coherent structures and wall temperature, which provided explanation for experimental observation. Numerical results showed that rotation distorted the symmetry of counter rotating vortex pair downstream of the hole. Coriolis force induced by rotation drove the inherent hairpin structure towards high radius side, resulting in the variation of vorticity. Rotation destroyed the continuity of hairpin structures, reducing the entrainment of mainflow and heat transfer from mainflow to coolant. Thus film cooling effectiveness in the core region was enhanced, consistent with experiment.

Key words: Film cooling; Large eddy simulation; Rotation; Coriolis force; Turbulence structure

摘要： 采用大涡模拟,考察了旋转影响气膜冷却的物理机制。参考实验模型,用带有30°倾斜圆柱孔的平板模拟涡轮转子叶片的吸力面,冷气出口雷诺数为1300,冷气和主流的吹风比为0.5,计算了静止和旋转数为0.2两种条件下的流动和换热,全面展示了旋转对平均流场、涡量、湍流结构和壁面温度分布的影响,并由此对实验现象进行了解释。结果表明,旋转使气膜孔下游的对转涡对产生不对称性；旋转引发的哥氏力使气膜冷却流场中的发夹型漩涡结构向高半径方向偏移,引起涡量分布的改变；旋转破坏了发夹涡的连续性,减少了对主流的卷吸和主流传递给冷气的热量,从而提高了冷却核心区的冷却效率,与实验中观察到的现象一致。

关键词: 气膜冷却;大涡模拟;旋转;哥氏力;湍流结构