燃气透平叶片尾缘开缝结构冷却性能的数值研究

Numerical Investigations on the Cooling Performance of Trailing Edge Cutback in Gas Turbine Blade

采用包含流体域和固体域的耦合传热数值求解方法,研究了压力侧开缝结构对典型燃气透平叶片尾缘冷却性能的影响,并利用已有的实验数据考核了数值方法的有效性和精度。通过计算获得了不同冷气量、开缝唇厚条件下尾缘部位的冷却性能。结果表明:在所考核的3种涡黏湍流模型中,标准k-ω湍流模型可以较好地模拟叶片尾缘的冷却性能;采用流固耦合传热计算方法可以较好地模拟尾缘开缝出口区域冷却气体的温度分布;增大吹风比可以有效加强内部冷却通道内的对流换热,并增大尾缘开缝出口区域的气膜冷却系数;开缝的高度固定时,唇厚越大,狭缝出口台阶处形成的旋涡尺度增大,减轻了主流流体对狭缝出口壁面的直接冲击,导致狭缝出口区域的总体冷却效果稍微提高,但整体流动损失增大。

A conjugate heat transfer method, which takes both the fluid and solid domains into consideration, was utilized to investigate the effect of pressure side cutback geometry on the cooling performance in a typical gas turbine blade. In order to validate the present numerical methods, the computed film cooling coefficient and pressure were compared with the experimental data. After the reliability and accuracy of the numerical method have been demonstrated, the influence of blowing ratio and lip thickness on the cooling performance was studied in detail. It shows that, among the selected three standard κ-ε turbulence model, κ-ω turbulence model and SST κ-ω turbulence model, the κ-ω turbulence model has superior accuracy in predicting the cooling performance of the blade trailing edge cutback. The conjugate heat transfer method considering both fluid domain and solid domain could properly resolve the temperature distributions near the cutback lip. As the blowing ratio increases, the convection heat transfer in the blade cutback channel is enhanced, and the corresponding film cooling coefficients are increased at the cutback outlet. If the height of the ejection slot is fixed, the scale of the vortices at the slot exit is increased with the increase of lip thickness. Such flow pattern reduces the impact effect of mainstream to the trailing edge cutback, which leads to a slight improvement of the overall cooling effectiveness at the cutback outlet region. However, the loss coefficient of the whole flow region is inevitably increased.