叶片前缘气膜冷却离散孔下游湍流特性试验研究

Turbulence Characteristics in the Downstream of Discrete Film Cooling Holes on Turbine Blade Leading Edges

以NASA发布的燃气轮机叶片为研究对象,风速设定为10 m/s;以热膜风速仪为测量工具,在气膜冷却叶片压力面和吸力面下游指定位置沿不同叶高湍流度进行测量。实验结果表明:随着射流比的增大,压力面和吸力面主射流掺混中心有上移的趋势且掺混中心扰动强弱受当地吹风比影响较大;在压力面叶片型面曲率梯度较大处,沿壁面流动的风速增大导致回流、扰动加强及混合流体的贴壁性变差;吸力面流体近尾流区域在大吹风比下扰动反而减弱;叶片表面的湍流度受到射流比、壁面曲率梯度大小及方向等多方面因素的影响。

The gas turbine blade is studied as released by NASA, under the condition that the mainstream velocity to be 10 m/s, the Hot-film anemometer is used to measure the film cooling blade pressure surface and different high turbulence along designated postion downstream the suction surface. The result shows when the blowing ratio on the suction side and the pressure surface increasing, the mainstream and the jet injection mixing center is on the trend of raising. However, the local blowing ratio affects the disturbance strength of mixing center at a large extent. The pressure surface in the relatively large curvature gradient of the blade surface along the wall surface increases the flow rate that causes the back flow phenomenon. When disturbance strengthens, mixed fluid adherent of wall becomes poor. The suction surface fluid at the near wake flow area exist in the high blowing ratio condition, the disturbance becomes weak. Turbulence of the blade surface is influenced by various factors such as jet fluid ratio, as well as the size and the direction of surface curvature gradient.