利用W型槽提高气膜冷却效率机理

Mechanism on Increasing Film Cooling Effectiveness

关键词:  涡轮叶片  薄膜冷却  冷却效率  涡对  W型槽

Key words:  Turbine blades  Film cooling  Cooling effectiveness  Vortex pair  W-shape slot

摘要:

为了探讨圆柱孔出口开有W型槽结构的气膜冷却机理，数值模拟研究了W型槽与横向槽下游流场、温度场及气膜冷却效率。分析了W型槽深度对气膜冷却效率的影响。结果表明:相比于横向槽，W型槽结构展向平均气膜冷却效率提高70%～130%。随着W型槽深度增加，气膜孔出口下游的对漩涡减弱，两侧的附加漩涡增强，最终形成一对反向对漩涡。小吹风比0.5时，三种W型槽深结构的展向平均气膜冷却效率差别小于8%；大吹风比1.5时，槽深0.5D(D为气膜孔孔径)结构展向平均气膜冷却效率高于槽深0.25D结构的展向平均气膜冷却效率75%～150%。槽深0.5D和0.75D结构的展向平均气膜冷却效率基本相同，差别小于3%。

Abstract:

In order to explore the film cooling performance of cylindrical holes attached with W shape slots，the flow field，the temperature field and the film cooling effectiveness distribution on the downstream wall of W shape slots and transverse slots were studied by numerical simulation. Influences of the depths of the W shape slot on the film cooling effectiveness were analyzed. The results show that the spanwise averaged film cooling effectiveness of the W shape slot model increased by 70%～130% compared with that of the transverse slot. With the increase of W shape slot depths，the rotating vortices are weakened in the downstream of the film cooling hole exit，and the additional vortices are strengthened in the downstream of both sides of the hole，eventually forming a pair of reverse counter-rotating vortices. At the low blowing ratio of 0.5，the difference of the spanwise averaged film cooling effectiveness is less than 8% among the three depths of W-shape slots. At the high blowing ratio of 1.5，the spanwise averaged film cooling effectiveness of the slot depth 0.5D (D means film hole diameter)case is much higher than that of 0.25D by 75%～150%. However，the spanwise averaged film cooling effectiveness of the slot depth of 0.5D case is close to 0.75D case，in which the difference is less than 3%.