Preliminary Results of a Study of the Relationship Between Free Stream Turbulence and Stagnation Region Heat Transfer
Preliminary Results of a Study of the Relationship Between Free Stream Turbulence and Stagnation Region Heat Transfer
复制标题
自由流湍流与停滞区传热关系研究的初步结果
DOI：
10.1115/85-gt-84
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发表时间：
1985
期刊：
影响因子：
--
通讯作者：
R. Simoneau
中科院分区：
文献类型：
--
作者：
G. J. Vanfossen;R. Simoneau
美国航天局刘易斯研究中心正在进行一项研究，以调查在涡轮机导叶和叶片的滞止区中引起自由流湍流以增加传热的机理。这项工作是在大气条件下的风洞中进行的，以便于测量湍流和传热。模型尺寸按比例放大，以模拟涡轮机叶片前缘上预期的雷诺数（基于前缘直径）。实验雷诺数为13000 ~ 177000，测量了“粗糙”和光滑表面驻点区在高湍流度和低湍流度下的展向平均换热。这些测量结果表明，即使在所测试的雷诺数下存在自由流湍流，边界层仍保持层流特性。如果增加粗糙度的边界层成为过渡的热传递的增加证明了从stationline.Hot线测量附近的滞流区下游的一个阵列的平行线表明，涡的平均速度梯度的形式被放大作为流动接近滞流区。热线探针在圆柱表面附近的周向移动显示了速度变化的波动分量，其特征取决于自由流湍流度和雷诺数。最后，烟丝流动显示和液晶表面传热显示相结合，表明在平行丝阵列的尾流中，在速度波动分量（局部湍流）最高的金属丝尾流中，热传递最小。发现诱导速度朝向圆柱表面的涡对之间的热传递最高。版权所有© 1985 by ASME
A study is being conducted at the NASA Lewis Research Center to investigate the mechanism that causes free stream turbulence to increase heat transfer in the stagnation region of turbine vanes and blades. The work is being conducted in a wind tunnel at atmospheric conditions to facilitate measurements of turbulence and heat transfer. The model size is scaled up to simulate Reynolds numbers (based on leading edge diameter) that are to be expected on a turbine blade leading edge. Reynolds numbers from 13 000 to 177 000 were run in the present tests.Spanwise averaged heat transfer measurements with high and low turbulence have been made with “rough” and smooth surface stagnation regions. Results of these measurements show that the boundary layer remains laminar in character even in the presence of free stream turbulence at the Reynolds numbers tested. If roughness is added the boundary layer becomes transitional as evidenced by the heat transfer increase with increasing distance from the stagnation line.Hot wire measurements near the stagnation region downstream of an array of parallel wires has shown that vorticity in the form of mean velocity gradients is amplified as flow approaches the stagnation region. Circumferential traverses of a hot wire probe very near the surface of the cylinder have shown the fluctuating component of velocity changes in character depending on free stream turbulence and Reynolds number.Finally smoke wire flow visualization and liquid crystal surface heat transfer visualization have been combined to show that, in the wake of an array of parallel wires, heat transfer is a minimum in the wire wakes where the fluctuating component of velocity (local turbulence) was the highest. Heat transfer was found to be the highest between pairs of vortices where the induced velocity is toward the cylinder surface.Copyright © 1985 by ASME