Measurements of Local Wall Heat Transfer Coefficient in Sharp 180 Degree Turns in Multipass Rib-roughened Channels

本文研究了高温燃气轮机翼型中多通道肋形粗糙冷却通道急转弯内的湍流换热特性。冷却通道将被建模为一系列矩形通道，带有肋骨粗糙的墙壁，通过两个180度转弯连接。用萘升华传质技术和传统的箔片加热器-热电偶法确定了局部换热系数在转弯内和附近的分布。实验结果将获得不同的通道长宽比、转弯间隙、转角曲率、肋骨几何形状和流动雷诺数等典型的涡轮发动机应用。相应的油烟流动可视化实验是对强迫对流实验的补充。有效的叶片冷却延长了先进燃气轮机的使用寿命。本文的研究结果将有助于了解多通道肋粗糙通道的换热和流动特性，这对涡轮发动机的设计具有重要意义。

The heat transfer characteristics of turbulent air flow in the sharp turns in multipass rib-roughened cooling channels in high temperature gas turbine airfoils are to be studied. The cooling channels will be modeled as a series of rectangular channels, with rib-roughened walls, connected with two 180 degree turns. The local heat transfer coefficient distribution in and near the turns will be determined with both the naphthalene sublimation mass transfer technique and conventional foil heaters-thermocouples method. Experimental results will be obtained for various channel aspect ratios, turn clearance gaps, curvatures of the turn corners, rib geometries, and flow Reynolds numbers typical of turbine engine applications. Corresponding flow visualization experiments with the oil-lampblack technique will supplement the forced convection experiments. Effective blade cooling prolongs the life of advanced gas turbines. The results of this research will contribute to the understanding of the heat transfer and flow characteristics of multipass rib-roughened channels, which is important in the design of turbine engines.