Local Heat Transfer Measurement in an Internal Cooling Passage of a Gas Turbine Blade and its Direct Numerical Simulation

为了弄清旋转系统中控制换热的湍流结构，进行了光滑和肋状粗糙通道的实验和数值分析。在实验中，使用了两种不同的实验装置。一种是直管实验，另一种是蛇形管道实验。用204个热电偶对直方管内的换热系数进行了测量，结果表明换热系数在流向和圆周方向上都有变化。在90度肋骨布置的情况下，两个连续肋骨之间的局部换热最大。当肋骨倾斜60度时，由该倾斜引起的二次流导致换热增强。在矩形蛇形管道的情况下，用458热电偶测量了倾斜角度从45度改变到90度时的肋骨倾斜效应。在数值分析中，采用有限差分法对旋转方形光滑通道壳体进行了数值模拟。用半边长和摩擦速度定义的雷诺数为350，旋转数在0到1.0之间变化。由于计算资源的限制，引入了Smagorinsky模型。数值结果表明，科里奥利力对吸力面附近换热的周向变化和层化有一定的影响。当考虑扩展到更复杂的管道结构时，引入并行计算技术和通用的亚网格尺度模型将是下一步必不可少的。

In order to clarify the structure of turbulent flow governing the heat transfer in a rotating system, the experiments of smooth and rib-roughened ducts and the numerical analysis were performed. In the experiments, two different experimental setups were used. One is for straight-duct experiment and the other is for serpentine-duct experiment. The square-straight-duct results measured by using 204 thermocouples showed the variation of heat transfer coefficient in both streamwise and peripheral directions. The case of 90 degrees rib arrangement showed the locally maximum heat transfer between the two consecutive ribs. When the ribs were inclined to 60 degrees, the secondary flow induced by this inclination caused the augmentation in heat transfer. In the rectangular serpentine duct case, the rib inclination effect was examined changing the inclination angle from 45 to 90 degrees by using 458 thermocouples. The maximum heat transfer was obtained around the angle of 45-60 degrees.In the numerical analysis, the rotating square smooth duct case was simulated by using the finite difference method. The Reynolds number defined by using the half side length and the friction velocity was 350 and the rotation number was varied from 0 to 1.0. Because of the computational resource limitation, the Smagorinsky model was introduced. The numerical results showed the effect of the Coriolis force on the peripheral variation of heat transfer and the laminarization near the suction side. When the extension to the more complicated duct configuration is considered, the introduction of the parallel computing technique and the universal sub-grid scale model will be essential as a next step.