圆孔-半椭圆槽组合结构气膜冷却机理

Mechanism of Film Cooling for Combined Cylindrical Holes and Semi-Elliptical Slots

关键词:  气膜冷却  半椭圆槽  涡轮叶片  冷却效率  对漩涡

Key words:  Film cooling  Semi-elliptical slot  Turbine blade  Cooling effectiveness  Vortex pair

摘要:

为了探讨半椭圆槽改善圆孔射流气膜冷却机理，数值模拟研究了圆孔-半椭圆型槽组合结构下游流场、温度场及气膜冷却效率。分析了不同吹风比下半椭圆槽深度对气膜冷却特性的影响。结果表明:吹风比0.5和1.5时，和锯齿槽相比，半椭圆槽更容易形成反向对漩涡，展向平均气膜冷却效率提高5%～119%。随着半椭圆槽深度的增加，孔间区域的气膜冷却效率提高，展向气膜冷却效率分布更均匀。吹风比0.5时，槽深度对半椭圆槽展向平均气膜冷却效率的影响很小，三种槽深的差距在15%以内。吹风比1.5时，半椭圆槽深度为0.5倍孔径的展向平均气膜冷却效率最佳，分别比槽深度为0.25倍和0.75倍孔径的半椭圆槽高55%～107%和2%～16%。

Abstract:

Numerical simulation was carried out to study the flow field， temperature field and film cooling effectiveness downstream of cylindrical holes with semi-elliptical shape slots to reveal the mechanism of film cooling combined cylindrical holes and semi-elliptical slots. Influences of the depths of the semi-elliptical shape slots on film cooling were analyzed at different blowing ratios. The results show that the semi-elliptical slots are more easily to form counter-rotating vortices and the spanwise averaged film cooling effectiveness of the semi-elliptical slot model increased 5%～119% compared with that of the saw tooth slot when the blowing ratio is 0.5 and 1.5. The distribution of spanwise film cooling effectiveness is more uniform and film cooling effectiveness is improved in the span regions between the cylindrical holes as the increase of the depths of semi-elliptical slot. At the blowing ratio of 0.5， the influence of the depths of the semi-elliptical shape slots on spanwise averaged film cooling is less than 15%. At the blowing ratio of 1.5， the spanwise averaged film cooling effectiveness of the semi-elliptical slot depths of 0.5 times of film hole diameter case is higher than that of 0.25 and 0.75 times of film hole diameter by 55%～107% and 2%～16%， respectively.