旋转状态下涡轮叶片压力面气膜冷却特性

通过1.5级涡轮叶片旋转气膜冷却实验,揭示了整级涡轮叶片在旋转状态下的气膜冷却规律.实验中,主流雷诺数为8×104,旋转数分别为2.092,2.324和2.448,吹风比从0.3到3.0变化,冷却工质分别采用空气和二氧化碳,对应射流主流密度比分别为1.03和1.57.叶片表面喷有宽幅液晶,通过高精度CCD相机得到表面温度场.结果表明:压力面上,气膜冷却效率随吹风比的增大而升高,随旋转数的增大而降低;气膜轨迹向高半径方向偏转,偏转程度随旋转数的增大而加剧;提高射流主流密度比,有利于提高冷却效率.

Film cooling characteristics on pressure side of rotating turbine blade

Experimental investigations were carried on to indicate the rotating film cooling characteristics in a 1.5 turbine stage. The length of the tested blade in chordwise and spanwise was 124.3mm and 99mm respectively with a 4mm film hole in the middle span oriented 28° to the tangential of the pressure side in streamwise. The mainflow Reynolds number Re_g was 8×10⁴. The blowing ratio varied from 0.3 to 3.0. Three rotating number (Rt) of 2.092, 2.324 and 2.448 were focused on. Air and CO₂ worked as coolant to achieve the coolant to mainflow density ratio of 1.03 and 1.57 respectively. Thermo liquid crystal was employed to show the temperature distribution on pressure side surface which was captured by CCD. Results show that the film cooling effectiveness is increased with the blowing ratio rising while it is decreased with the Rt rising. Meanwhile, increasing Rt could lead the film trajectory to deflect more centrifugally. But it deflect less centrifugally with the blowing ratio rising under the same Rt. High density ratio could improve the film cooling effectiveness dramatically.