倾角孔对叶片前缘冷却效率影响的数值研究

Numerical Study of Influence of Inclined Hole on Film-Cooling Effectiveness at Leading Edge of a Turbine Blade

关键词:  气膜冷却  叶片  前缘  孔形  冷却效率  数值模拟

Key words:  Film cooling  Turbine blade  Leading edge  Shaped hole  Cooling effectiveness  Numerical simulation

摘要:

为进一步改善燃气轮机叶片前缘区域气膜冷却效果，在全尺寸燃气轮机透平级上对“直角孔”和“倾角孔”两种孔结构的流动和传热进行了数值模拟研究。结果显示“倾角孔”结构能够有效地提高前缘区域的冷却效率，在特定的结构参数下，其冷却效率最高可达直角孔的2.42倍。通过流场的分析对其提高冷却效率的机理进行了说明:倾角孔形成的气膜可以有效覆盖孔间和孔排间的冷却盲区，从而提高了冷却效率。此外还研究了吹风比、孔径和孔距对“倾角孔”冷却效率的影响。结果表明:倾角孔的冷却效率同时受到交错流有效度和和二次流与主流掺混度的影响，在这两个因素共同作用下，冷却效率存在着一个峰值；孔径的增大和孔距的减小可以提高冷却效率，但是由于孔排间二次流的干涉作用，孔距过小会导致冷却效率分布不均匀。

Abstract:

For the purpose of improving the film cooling effect on leading edge region of gas-turbine blade，numerical simulation was carried out on full-sized gas turbine stage to investigate the flow and heat transfer for two types of hole，namely，orthogonal hole and inclined hole. It is found that inclined hole can increase the effectiveness of film-cooling by maximum of 1.42 times comparing to the orthogonal hole under the specific structural parameters. The physics was revealed by the analysis of the flow filed and results show that the film formed by inclined hole can cover the shadow area between holes and hole-rows and consequently increase the effectiveness. The influence of blowing rate，hole diameter and hole pitch on cooling effectiveness was studied and the results show that the cooling effectiveness of inclined hole is dominated by cross-flow effectiveness and the mixing between main stream and secondary stream simultaneously. There is a peak effectiveness under these two factors. The increase of hole diameter and decrease of hole pitch can raise the cooling effectiveness，but small hole pitch can lead to the nonuniform of cooling effectiveness due to interference between the secondary streams of two hole rows.