Experimental study of swirling flow characteristics in a semi cylinder vortex cooling configuration
Experimental study of swirling flow characteristics in a semi cylinder vortex cooling configuration
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DOI：
10.1016/j.expthermflusci.2019.110036
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发表时间：
2020-05
影响因子：
3.2
通讯作者：
Xiaojun Fan;Chuangxin He;L. Gan;Liangxing Li;Changhe Du
中科院分区：
文献类型：
--
作者：
Xiaojun Fan;Chuangxin He;L. Gan;Liangxing Li;Changhe Du
本文利用平面粒子图像测速仪(PIV)研究了具有两个喷口的半圆柱约束内的流动特性。水基实验研究旨在了解燃气轮机前缘涡流冷却结构中的基本流动行为。在3个不同的进口雷诺数下，采集了3个横截面和1个纵截面的时间平均和脉动流场。采用基于快照的本征正交分解(POD)方法提取相干流特征。结果表明，涡流由燃烧室内的大尺度涡流和小的回流角涡流组成。核心涡类似于朗肯涡，具有近固体旋涡，周围环绕着沿燃烧室壁面的喷流涡层和边界层。以周向速度成比例下降为特征的喷流涡层不同于典型朗肯涡势层。高速射流涡流是造成涡流冷却换热速率较高的主要原因。在θ≈为170°时，发现了一个分离周向速度行为的转折区，这为涡流冷却时沿壁面的换热强度提供了一个流动动力学解释。固体旋涡与喷流涡交界处的速度量级相对较低，但剪切较强，速度脉动强度较大。纵向截面的平均速度较低(约为横截面平均速度的10%)，表明涡流是强旋转而弱螺旋的。然而，脉动速度强度与横截面有相当的水平。POD分析表明，前4阶振型包含了约23.2%的脉动速度能量。在喷管截面上，近壁面附近的拟序涡控制着脉动能，并对强化换热起作用。在喷嘴之间的截面上，粘性流动结构在核心内表现为一对涡，在角涡中表现出较小的涡量。
This study utilised planar Particle Image Velocimetry (PIV) to investigate the flow characteristics in a semi cylindrical confinement with 2 jet inlets. The water based experimental study aims to understand the basic flow behaviour in a gas turbine leading edge vortex cooling configuration. The time averaged and fluctuating flow fields were collected at 3 cross sections and 1 longitudinal section at 3 different inlet Reynolds numbers. The snapshot based Proper Orthogonal Decomposition (POD) was applied to extract the coherent flow characteristics. Results showed that the vortex flow consists a large-scale vortex in the chamber with a small recirculating corner vortex. The core vortex is similar to the Rankine vortex with a near solid body rotating vortex, surrounded by a jetting vortex layer and a boundary layer along the chamber wall. The jetting vortex layer featuring a proportional decline of circumferential velocity is different to the potential layer in a typical Rankine vortex. The jetting vortex at a high velocity level is mainly responsible for the high heat transfer rate for vortex cooling. A turning region at θ≈ 170° separating the circumferential velocity behaviour was noticed, which provides a flow dynamic explanation to the heat transfer intensity along the surface wall for vortex cooling. The region at the interface between the solid body rotating vortex and the jetting vortex features with relatively low velocity magnitude but strong shear and large fluctuating velocity intensity. The longitudinal section has a low average velocity (approximately 10% of that in the cross sections in magnitude), indicating the vortex flow is strongly rotational but weakly helical. However, the fluctuating velocity intensity has a comparative level to cross sections. POD analysis reveals that the first 4 modes contain about 23.2% of the fluctuating velocity energy. In nozzle cross sections, the coherent vortex near the surface wall dominates the fluctuation energy and is responsible for the heat transfer enhancement. In the cross section between nozzles, the coherent flow structure displays a vortex pair in the core and a minor corner vortex.