涡轮叶片内部微小V肋-凹陷涡复合冷却流动与传热数值模拟

Numerical Study of Flow and Heat Transfer on Miniature V Rib-Dimple Composite Structure in Turbine Blade Internal Cooling

关键词:  涡轮  叶片  冷却  传热  流场结构  数值模拟

Key words:  Turbine  Blade  Cooling  Heat transfer  Flow field structure  Numerical simulation

摘要:

为强化航空发动机涡轮叶片内冷通道传热性能，针对带有微小V肋-凹陷涡高效复合冷却结构矩形通道，采用Abe Kondoh Nagano （AKN） k-ε湍流模型数值模拟研究了肋高与凹陷深度组合对流动传热特性的影响机理。结果表明，当凹陷深度一定，复合结构的强化换热效果随肋高增加而增加，3mm肋高复合结构的传热相比纯凹陷提高了87.1%；当肋高一定，传热随凹陷深度增加先增强后基本保持不变，6mm深凹陷复合结构相比纯V肋提高了52.8%。通过在凹陷上游布置V肋，增强了越过V肋冲入凹陷内流体的湍动能，从而使凹陷前部回流区减小；同时来自微小V肋的涡流与凹陷内部的涡流相互作用，增强了整个流场的动量和热量输运，使通道换热均匀，并相较纯凹陷或纯V肋结构均有显著提升。

Abstract:

To enhance the heat transfer performance of the internal cooling channel in turbine blades， miniature V rib-dimple composite structures were arranged on one side of the rectangular channel in which the effects of various rib heights and dimple depths were investigated on heat transfer characteristics and flow structures. Abe Kondoh Nagano（AKN） k-ε turbulence model was utilized for the numerical simulation. Results show that when dimple depth remains constant， the heat transfer augmentation increases as rib height increases. When rib height remains constant， the heat transfer first increases significantly and then less obviously as dimple depth increases. And the optimum structure， whose average Nusselt number is separately 87.1% and 52.8% higher than that of the pure dimple or V-rib structure， is obtained when the rib height is 3 mm and the dimple depth is 6 mm. It is evident that by arranging a miniature V rib in upstream of every dimple， the turbulent kinetic energy of the fluid passing over the V rib and rushing down into the dimple is enhanced， thereby reducing the recirculation zone at the front of the dimples. Simultaneously， the interaction between the vortices from V rib and inside the dimple enhances the overall momentum and heat transport of the flow field， which contributes to not only a uniform heat transfer distribution in the channel but also significantly higher heat transfer than that of the pure dimple or V rib structure.