非定常尾迹及其对动叶气膜冷却影响的数值研究

Numerical Simulation of Unsteady Wakes and the Influence on Film-cooling Effectiveness

针对前缘设有3排气膜孔的动叶,采用数值模拟方法对其静叶尾迹的非定常特性进行了研究,分析了静叶尾迹对动叶气膜冷却的影响.通过模拟吹风比分别为0.5、1和2时的工况,结合对应工况下的等熵图,对动叶升力系数和阻力系数进行了频谱分析,得到动叶表面的静压分布和传热系数分布.结果表明:随着吹风比的增大,下游叶栅通道的熵值有所减小,尾迹涡脱落频率没有明显变化;动叶压力面静压随着吹风比的增加而降低,压力梯度减小,传热系数则增大,换热增强,冷却效果较好;吸力面静压随着吹风比的增大而逐渐升高,形成了以吸力面最大曲率处为中心的负压区,传热系数增大,但靠近吸力面尾缘部分的换热效果优于前缘部分.

Numerical simulation has been performed to investigate the characteristics of unsteady wakes of stator vane when there are three rows of film-cooling holes arranged at the leading edge of rotor,while influence of the unsteady wakes on the film-cooling effectiveness analyzed.Under different working conditions with respective blowing ratio of 0.5,1 and 2,and based on isentropic chart of corresponding conditions,a spectral analysis on the lift and drag coefficient of rotor blade has been carried out,during which distribution of both the static pressure and the heat-transfer coefficient on rotor surface is obtained.Results show that with the rise of blowing ratio,the entropy reduces gradually in the downstream cascade channel;the vortex shedding frequency basically keeps unchanged;on the pressure side of rotor,the static pressure and pressure gradient reduces,resulting in increased heat-transfer coefficient and enhanced cooling effect;whereas,on the suction side of rotor,the static pressure increases gradually,forming a negative pressure area,centering around the point with maximum curvature,and therefore resulting in increased heat-transfer coefficient.However,the heat-transfer effect at trailing edge is better than that at leading edge on the suction side.