倾斜椭球凹陷阵列湍流强化传热实验与数值分析

Experiments and numerical analysis of turbulent heat transfer enhancement over oval-dimple arrays

关键词:  涡轮叶片冷却  斜椭球凹陷  传热  瞬态液晶热像实验  流动结构

Key words:  Turbine blade cooling  Oval dimple  Heat transfer  Transient TLC experiment  Flow structure

摘要:

为了提高涡轮叶片内部通道对流传热性能，本文基于瞬态液晶热像技术分别针对矩形通道表面排布的球形凹陷和斜椭球凹陷阵列的传热和压力损失特性进行了实验研究。在雷诺数为1×10⁴~6×10⁴内，与基准球形凹陷相比，平行排布和V形排布的斜椭球凹陷总体传热分别增强了23.8%~33.8%和104%~121%，V形排布的斜椭球凹陷综合传热性能显著提高了25%~68.3%。通过数值模拟发现，平行排布的斜椭球凹陷虽然可以诱发更强烈的二次流，但是平行的排布方式使下游凹陷受到来自上游凹陷升温后的流体冲刷，因此限制了传热的进一步增强。V形排布的斜椭球凹陷通过诱发大尺度的纵向涡对将来自主流的冷流体输运至壁面，冷流体直接冲击壁面并与近壁流体剪切，极大地增强了对流传热。

Abstract:

In order to improve the convective heat transfer performance of the internal channel of the turbine blade，the heat transfer and pressure loss characteristic of rectangular channel roughened with spherical dimple arrays and oval dimple arrays has been studied based on the transient TLC technology. The heat transfer of parallel oval dimple and the V-shaped oval dimple is 23.8%~33.8% and 104%~121% higher than that of the baseline spherical dimple， respectively， within Re being 1×10⁴~6×10⁴. The overall thermal performance factor of V-shaped oval dimple is improved by 25%~68.3% compared to the baseline spherical dimple. The heat transfer mechanism has been analyzed with the help of numerical simulation. The parallel oval dimple can induce more intense secondary flow， but the flow delivered into the dimple downstream has been heated due to its arrangement， which is the limitation of further heat transfer enhancement. The V-shaped oval dimple can induce the large-scale longitudinal vortex pair delivering the cold flow from the mainstream to the dimpled surface. The cold flow impinges the wall and shears with the near-wall fluid. In this way， the convective heat transfer can be strengthened greatly.