沟槽表面双排孔顺逆组合对气膜冷却的影响

Effects of Forward and Backward Combinations with Two Rows of Holes on Film Cooling of Grooved Surface

关键词:  涡轮  气膜冷却  沟槽表面  双排孔  数值模拟

Key words:  Turbine  Film cooling  Grooved surface  Dual-row holes  Numerical simulation

摘要:

为发挥气膜冷却中各结构优势，数值模拟研究了双排气膜孔顺逆组合形式对沟槽表面气膜冷却效率影响，孔间距与气膜孔直径之比为5，孔排间距与气膜孔直径之比为12，吹风比为0.3，0.8和1.4。结果表明，在吹风比较小时，沟槽对气膜有显著的导向作用，冷气在相邻的沟槽内部流动。当吹风比增大时，冷气喷到沟槽顶部，导向作用减弱。顺向射流的气膜贴近冷却表面，在低吹风比下气膜冷却效率较高。在高吹风比下，逆向射流覆盖更宽，气膜孔排间叠加效应明显。吹风比为0.3时，顺-顺组合的气膜冷却效率最高，面平均气膜冷却效率为0.13。当吹风比为0.8时，顺-顺、逆-顺、顺-逆组合的面平均气膜冷却效率相近，约为0.11，其中顺-逆组合气膜冷却效率分布更均匀。吹风比为1.4时，逆-逆组合的面平均气膜冷却效率最高，为0.13。

Abstract:

To make full use of each structure in film cooling， numerical simulations were conducted to study the effects of forward and backward combination with two rows of holes on film cooling effectiveness of the grooved surface. The ratio of the hole spacing to the diameter was 5， the ratio of the spacing between the hole rows to the diameter was 12. The blow ratios were 0.3， 0.8 and 1.4， respectively. The results show that when the blow ratio is relatively small， the grooves have a significant guiding effect on the film， and the coolant flows in the adjacent grooves. When the blow ratio increases， the coolant is sprayed to the top of the grooves， and the guiding effect is weakened. The film of the forward jet is close to the surface， and the film cooling effectiveness is higher at the low blow ratio. The reverse jet coverage is wider， and the superposition effect between the film holes is obvious， which is suitable at the higher blow ratio. The forward-forward combination has the highest film cooling effectiveness at the blow ratio of 0.3， and the area averaged film cooling effectiveness is 0.13. The area averaged film cooling effectiveness of the forward-forward， backward-forward， and forward-backward combination are similar at the blow ratio of 0.8， about 0.11， which is 27% higher than that of the backward-backward combination， of which the forward-backward combination film cooling effectiveness distribution is more uniform. The backward-backward combination has the highest area averaged film cooling effectiveness at the blow ratio of 1.4， which is 0.13.