Effects of Surface Geometry on Film Cooling Performance at Airfoil Trailing Edge
Effects of Surface Geometry on Film Cooling Performance at Airfoil Trailing Edge
复制标题
表面几何形状对翼型后缘气膜冷却性能的影响
DOI：
10.1115/1.4004828
复制
发表时间：
2012
影响因子：
1.7
通讯作者：
C. Nakamata
中科院分区：
文献类型：
--
作者：
A. Murata;Satomi Nishida;H. Saito;K. Iwamoto;Y. Okita;C. Nakamata
燃气轮机翼型后缘冷却是最困难的问题之一，因为其外形薄，两面热负荷大，窄通道的几何形状难以冷却，同时对结构强度要求很高。本文采用红外热像仪对压边缩口表面的换热系数和气膜冷却效率进行了测量。研究了四种不同的缩进几何形状：两个等宽且收敛的光滑缩进表面(底部和扩散器情况)和两个带有横向肋条和球形凹陷的粗糙缩进表面。由平均速度和两倍通道高度定义的主流雷诺数为20000，吹风比在0.5、1.0、1.5和2.0之间变化。实验结果清楚地显示了缩口和平台顶面的换热系数和气膜冷却效率的空间变化。压缩表面的结果清楚地表明，由于肋骨和韧窝的周期性表面几何形状，周期性地强化了换热。总体而言，吹风比的增大既提高了换热系数，又提高了气膜冷却效率。在本实验范围内，凹陷表面是一种良好的缩进表面几何形状，因为它在不降低高气膜冷却效率的情况下提供了强化换热。
Cooling at the trailing edge of a gas turbine airfoil is one of the most difficult problems because of its thin shape, high thermal load from both surfaces, hard-to-cool geometry of narrow passages, and at the same time demand for structural strength. In this study, the heat transfer coefficient and film cooling effectiveness on the pressure-side cutback surface was measured by a transient infrared thermography method. Four different cutback geometries were examined: two smooth cutback surfaces with constant-width and converging lands (base and diffuser cases) and two roughened cutback surfaces with transverse ribs and spherical dimples. The Reynolds number of the main flow defined by the mean velocity and two times the channel height was 20,000, and the blowing ratio was varied among 0.5, 1.0, 1.5, and 2.0. The experimental results clearly showed spatial variation of the heat transfer coefficient and the film cooling effectiveness on the cutback and land top surfaces. The cutback surface results clearly showed periodically enhanced heat transfer due to the periodical surface geometry of ribs and dimples. Generally, the increase of the blowing ratio increased both the heat transfer coefficient and the film cooling effectiveness. Within the present experimental range, the dimple surface was a favorable cutback-surface geometry because it gave the enhanced heat transfer without deterioration of the high film cooling effectiveness.