Numerical investigation and optimization of flat plate transpiration-film combined cooling structure

To improve the limited overall cooling effectiveness of laminated structure with the increase of coolant under larger Bi-number, a new optimized structure named transpiration-film combined cooling structure is proposed for the thermal protection of aero-engine combustion chamber. By replacing the lower impingement plate of the laminated structure with a porous layer, a desirable outside film coverage are achieved and the internal heat transfer is enhanced owing to the blocking effect and the large specific surface area of the porous layer. Accurate mathematical modeling and fully-coupled numerical approach are adopted to investigate and compare the cooling effectiveness, cooling uniformity, and the effect of skin friction reduction of the combined cooling structure and the laminated cooling structure under practical combustor conditions with larger Bi-number. The results show that the combined structure brings about a 30% increment in overall cooling effectiveness and a considerable improvement in temperature uniformity of the whole structure, and moreover, the frictional resistance on the structure surface is greatly reduced. Furthermore, an automatic single-objective optimized method is adopted to obtain optimal schemes of the combined cooling structure under a practical combustion chamber working condition, powerfully promoting the cooling effectiveness by 8.5%-8.7%. This work aims to provide the designers of aero-engine with a valuable reference for searching the thermal management approach with high efficiency and low frictional resistance.