Case Studies in Thermal Engineering (Sep 2024)
Conjugate heat transfer analysis on composite cooling structure with low Reynolds number using the decoupling method
Abstract
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.
