Volumetric Velocimetry Measurements of Purge-Mainstream Interaction in a One-Stage Turbine
Volumetric Velocimetry Measurements of Purge-Mainstream Interaction in a One-Stage Turbine
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单级涡轮机中净化与主流相互作用的体积测速测量
DOI：
10.1115/1.4050072
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发表时间：
2021
期刊：
影响因子：
--
通讯作者：
Carvalho Figueiredo A
中科院分区：
文献类型：
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作者：
Carvalho Figueiredo A
风冷式燃气轮机利用来自压缩机的引气来冷却涡轮机中的易损部件。冷却流（通常称为吹扫空气）以小半径引入，然后通过涡轮盘周边的边缘密封件排出。吹扫流与主流气路相互作用，形成不稳定且复杂的流场。设计者特别感兴趣的是吹扫对叶片通道内二次流结构的影响，其程度直接影响级中的气动损失。本文提出了一种实验和计算流体动力学 (CFD) 相结合的方法，研究吹扫流对光学可访问的单级涡轮机叶片通道中二次流的影响。实验活动使用体积测速（VV）测量来评估三维叶片间速度场；补充 CFD 活动是使用非稳态雷诺平均纳维-斯托克斯 (URANS) 计算进行的。在旋转环境中实施 VV 是世界首创，并且提供了无与伦比的实验细节水平。在没有吹扫流的情况下，基线流场展示了经典的二次流场：马蹄形涡流的卷起，随后压力侧和吸力侧腿的下游对流，前者过渡到通道涡流。以主流流量的 1.7% 引入吹扫，可以通过增强通道涡流的强度和跨度运移来改变二次流场。计算预测与实验揭示的增强效果一致。
Air-cooled gas turbines employ bleed air from the compressor to cool vulnerable components in the turbine. The cooling flow, commonly known as purge air, is introduced at low radius, before exiting through the rim-seal at the periphery of the turbine discs. The purge flow interacts with the mainstream gas path, creating an unsteady and complex flowfield. Of particular interest to the designer is the effect of purge on the secondary-flow structures within the blade passage, the extent of which directly affects the aerodynamic loss in the stage. This paper presents a combined experimental and computational fluid dynamics (CFD) investigation into the effect of purge flow on the secondary flows in the blade passage of an optically accessible one-stage turbine rig. The experimental campaign was conducted using volumetric velocimetry (VV) measurements to assess the three-dimensional inter-blade velocity field; the complementary CFD campaign was carried out using unsteady Reynolds-averaged Navier–Stokes (URANS) computations. The implementation of VV within a rotating environment is a world first and offers an unparalleled level of experimental detail. The baseline flow-field, in the absence of purge flow, demonstrated a classical secondary flow-field: the rollup of a horseshoe vortex, with subsequent downstream convection of a pressure-side and suction-side leg, the former transitioning in to the passage vortex. The introduction of purge, at 1.7% of the mainstream flowrate, was shown to modify the secondary flow-field by enhancing the passage vortex, in both strength and span-wise migration. The computational predictions were in agreement with the enhancement revealed by the experiments.