Abstract

Film cooling using coolant jets is effective for increasing the cooling effectiveness of turbines. In the present study, large eddy simulation was employed for predicting small-scale vortices in the film-cooling process with different blowing ratios (BRs). The counter-rotating vortex pair (CRVP) was compared with the hairpin vortex, and results indicated the CRVP was the cross section of hairpin vortex. The results of a spectral analysis indicated a high correlation between the shedding period of the CRVP and the film-cooling effectiveness, and the dominant frequencies of the temperature and vorticity spectra were both identical to the shedding frequency of the CRVP when BR is less than 0.75. Furthermore, a higher shedding frequency of CRVP will suck the hot cross-flow into the core region more frequently, which will lead to a worse film-cooling effectiveness.

摘要

使用冷却剂射流的薄膜冷却对于提高涡轮机的冷却效率是有效的。在本研究中，采用大涡模拟来预测不同吹塑比 (BR) 薄膜冷却过程中的小尺度涡流。将反向旋转涡对（CRVP）与发夹涡进行比较，结果表明 CRVP 是发夹涡的横截面。谱分析结果表明，CRVP的脱落周期与膜冷却效率之间存在高度相关性，当BR小于0.75时，温度谱和涡度谱的主频均与CRVP的脱落频率相同. 此外，较高的 CRVP 脱落频率会更频繁地将热横流吸入核心区域，