低雷诺数涡轮叶片边界层转捩及分离特性测量

Measurement of the Transition and Separation for Turbine Blade Boundary Layer with Low-Reynolds Number

低雷诺数工作条件下涡轮流场特征及其控制设计,是航空发动机低压涡轮部件设计的难点和重点。针对低雷诺数涡轮叶栅流场开展了实验研究工作,利用油流显示、表面静压、边界层压力探针等测量手段研究了涡轮叶片边界层的分离和转捩。结果表明雷诺数降低导致了流动损失的增大,且存在一个临界雷诺数。当雷诺数小于临界雷诺数时,发生在吸力面的流动分离是开式的层流分离泡,不会再附与叶片;当雷诺数大于临界雷诺数时,分离流会在尾缘前重新附着于叶片吸力面,形成闭式分离泡。随着雷诺数的减小,出口尾迹变宽,出口流动损失、出口速度亏损和出口气流角偏离增大,尾迹中心向吸力面方向移动。

The flow field characteristics and its control under Low-Reynolds numbers work condition are essential for the Aero-Engine Low Pressure Turbine design. An experimental investigation was conducted on the turbine cascade flow field with the low - Reynolds numbers. The separation and transition of the boundary layer on the suction side of turbine blade were in- vestigated with the special oil flow display, surface static pressure holes, and boundary layer pressure probe. The detailed measurement results for the turbine cascade outflow field and blade surface boundary layer were presented. The results show that the flow losses increase with the decrease of Reynolds number, and a critical Reynolds number is in existence. When the Reynolds number is less than this critical value, the flow separation occurs on the suction surface with an open laminar separa- tion bubble, and flow can not reattach. When the Reynolds number is larger than the critical value, the separated flow reat- taches before the blade trailing and a closed separation bubble is formed. As the Reynolds number decreases, the exit wake is broadened, while exit flow loss and exit velocity deficit, as well as exit flow angle departure increase. Meanwhile the center of the wake shifts away from the suction surface.