劈缝射流尾迹特征的实验研究

Experimental Study on the Wake Characteristics of the Cutback Ejection

本文以简化透平叶片模型为对象,采用热线风速仪和粒子图像测速技术研究了尾缘劈缝射流尾迹结构,结合本征正交分解方法分析了不同射流速度比对尾迹时均特性、脉动特性以及旋涡运动特性的影响规律。结果表明:低动量射流时下板上表面流体分离,该侧剪切层在尾迹中振荡,影响旋涡配对和输运机制,模态中出现特殊带状结构;随射流速比增大,最大尺度旋涡强度增大,促进射流与主流剪切掺混,尾迹速度亏损更快被弥补,高阶频率脉动结构减少,动能损失小,因此在劈缝射流中应避免采用低动量射流。

An experimental study was conducted to analyze the detailed wake structure of the trailing edge cutback ejection of a model turbine blade with particle image velocimetry （PIV） and hot wire anemometer. Combined with the fast Fourier transform（FFT） and proper orthogonal decomposition （POD） methods, the effects of the various jet velocity ratios on the vortex spatial characteristics, time averaged and fluctuating wake field were analyzed. The results show that the jet flow separates from the lower plate surface of cutback edge under the condition of weak momentum ejection. The special banded structure appears in the wake probably results from the shear layer oscillation. The intensity of the large scale coherent structure increases with the increase of the ejection velocity ratios, promoting the mixing between the jet and the main flow. As the jet velocity ratio increases, the velocity deficit recoveries faster, and the fluctuating vortex structure of high frequency decreases and the aerodynamic loss decreases. Therefore, low momentum ejection should be avoided in the trailing edge cutback coolant ejection.