Improving cooling performance and robustness of NGV endwall film cooling design using micro-scale ribs considering incidence effects

Abstract

Modern lean-burn combustors generate aggressive swirling flow at the entrance of high-pressure turbine nozzle guide vane (NGV), and lead to cooling performance deterioration of the NGV film cooling system. Improving the cooling performance of NGV becomes a delicate task for the designers. In this study, micro-scale ribs with novel arrangement method were applied to improve the cooling effectiveness and robustness of NGV endwall cooling system at varying incidence conditions. Numerical simulations were employed to perform comprehensive studies on film cooling performance of smooth and ribbed endwall with double-row staggered film holes. Three incidence angles −30°, 0° and 30° were specified. Endwall adiabatic film cooling efficiency, heat transfer coefficient, net heat flux reduction (NHFR) and flow field structures were analyzed. The results indicated that the designed ribs weaken the intensity of the horse shoe vortex and passage vortex effectively. Coupled with the suppression of cross migration of coolant and weakening of heat transfer intensity, endwall cooling performance is thoroughly improved. Area-averaged film cooling efficiency and NHFR are increased by 46.33% and 108.43%, respectively, in the 30° incidence condition. In addition, the discrepancies of film cooling performance at different incidence conditions are attenuated, and the robustness of endwall cooling design is improved.