Composite cooling is a critical strategy for managing high temperatures in aero engine turbines. With the trend toward flying at unprecedented altitudes, the operational Reynolds number (Re) for turbines decreases significantly compared to conventional aircraft. This shift raises questions about the impact of low Re on the overall cooling effectiveness of composite cooling structures. The primary objective of this study is to evaluate the cooling performance of a composite cooling structure at low Re and to quantify the individual component contributions of the external film coolant coverage cooling, the impingement cooling, and the in-hole convective cooling. A systematic evaluation of different numerical decoupling methods is done, among which the “ideal” decoupling model is identified as the optimal approach to isolate the effects of each cooling component. Subsequently, the influence of low Re on the overall cooling effectiveness, the external film coolant coverage cooling, the impingement cooling, and the in-hole convective cooling contributions is quantified with the help of computational fluid dynamics (CFD) and the “ideal” decoupling model. The Re range is from 2e4 to 4e5. The study assumes steady-state conditions and employs simplified geometries to focus on the core cooling mechanisms. The dominance of the impingement cooling, and the decreasing of the impingement cooling contribution (up to 0.03 in overall cooling performance) with Re decreases is underscored, emphasizing the need for improvements in inner cooling mechanisms. A notable decrease in the proportion of in-hole convective heat transfer (up to 0.06 in overall cooling performance) is observed as the Re decreases. These findings highlight the importance of optimizing impingement and in-hole convective heat transfer at low Re conditions.

中文翻译：

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低雷诺数复合冷却结构的共轭传热分析


复合冷却是管理航空发动机涡轮高温的关键策略。随着空前高度飞行的趋势，涡轮机的运行雷诺数 (Re) 与传统飞机相比显着下降。这种转变引发了关于低 Re 对复合材料冷却结构整体冷却效率影响的问题。本研究的主要目的是评估复合材料冷却结构在低 Re 条件下的冷却性能，并量化外部薄膜冷却剂覆盖冷却、冲击冷却和孔内对流冷却的各个组件的贡献。对不同的数值解耦方法进行了系统评估，其中“理想”解耦模型被确定为隔离每个冷却组件影响的最佳方法。随后，借助计算流体动力学 (CFD) 和“理想”解耦，量化了低 Re 对整体冷却效率、外部薄膜冷却剂覆盖冷却、冲击冷却和孔内对流冷却贡献的影响模型。 Re 范围为 2e4 至 4e5。该研究假设稳态条件并采用简化的几何形状来重点研究核心冷却机制。强调了冲击冷却的主导地位，以及冲击冷却贡献随着 Re 的降低而降低（总体冷却性能高达 0.03），强调了改进内部冷却机制的必要性。随着 Re 的降低，孔内对流传热的比例显着降低（总体冷却性能高达 0.06）。 这些发现强调了在低 Re 条件下优化冲击和孔内对流换热的重要性。