微尘沉积形貌对冲击气膜冷却结构换热特性影响的数值研究

Numerical Study on Effects of Dust Deposition Morphology to Heat Transfer Characteristics of Impingement and Film Cooling Channel

关键词:  涡轮叶片  冲击气膜  微尘沉积  对流换热  数值模拟

Key words:  Turbine blades  Impingement and film  Dust deposition  Heat transfer  Numerical simulation

摘要:

带有微尘的空气进入航空发动机，极易在涡轮叶片内冷通道发生沉积。为探究微尘沉积形貌对涡轮叶片内冷通道换热特性的影响，选取冲击气膜冷却结构，基于微尘沉积实验结果，构造微尘沉积形貌，由锥状突起和环状突起组成，通过数值模拟获得不同射流雷诺数下冲击靶面局部努塞尔数Nu。研究结果表明，冲击靶面微尘沉积层的出现，将大幅降低浸润面积平均努塞尔数Nuˉw，而对映射面积平均努塞尔数Nuˉa影响较小；冲击驻点周围的高换热区范围减少；相邻冲击孔中点附近的高换热区局部努塞尔数增大；此外，射流雷诺数的增大整体上提高了冲击靶面的换热强度。由于锥状突起和环状突起的扰动作用， 壁面附近回流涡增多， 使得冲击靶面大部分区域温度边界层厚度增加，因此换热性能降低。

Abstract:

When air containing the dust enters the aero-engine， the dust is easy to deposit on the internal wall of the turbine blade. In order to explore effects on heat transfer characteristics of internal wall with the dust deposition， the impingement and film cooling channel were chosen. Depending on the result of the dust deposition experiment， the dust deposition morphology consisting of conical-shaped convex and the ring-shaped convex was built. Nusselt number on the impingement target surface under different jets Reynolds number is achieved by numerical simulation. The result shows that the average Nusselt number of wetted area weakens dramatically when the dust deposits on the impingement target surface， but average Nusselt number of mapped area is affected slightly. The high heat transfer area around the impingement stagnation point decreases. Nusselt number of the high heat transfer area near the middle point of adjacent jet holes is improved. In addition， the heat transfer intensity of the impingement target surface is improved with the increasing jets Reynolds number. The backflow vortices near the wall increase due to the disturbing effect of the conical-shaped convex and the ring-shaped convex， which cause the increasing thickness of the temperature boundary layer in most areas of the impact target surface. Therefore， the heat transfer performance decreases.