LARGE EDDY SIMULATION OF COMPOUND ANGLE EFFECTS OF TRENCHED SHAPED HOLES ON COOLING EFFECTIVENESS

Abstract

In advanced gas turbines, thermal barrier coatings (TBCs) are commonly employed to improve the cooling performance of the holes. The application of a TBC often leads to the embedding of cooling holes within a two-dimensional trench cavity, which alters both the aerodynamic and thermal characteristics of the coolant flow. In this study, large eddy simulations (LES) were performed to investigate the influences of compound angle (CA) on film-cooling effectiveness and flow structures for a laidback fan-shaped hole embedded within a two-dimensional trench on a flat plate. The trench configuration was adopted from the authors' previous optimization work. Five different cooling hole orientations (CA0, CA15, CA30, CA45, and CA60) were analyzed using an LES framework. The results reveal that the cooling performance and turbulent flow dynamics are strongly dependent on the cooling hole orientation. Interestingly, the effect of compound angle on the coolant jet trajectory in the trenched holes exhibits an opposite trend compared with that reported for conventional non-trenched geometries in previous studies. Although the presence of a compound angle enhanced the cooling effectiveness on the cavity bottom surface in all investigated cases, the area-averaged cooling effectiveness on the downstream flat plate decreased with increasing compound angle. The CA60 case exhibited the lowest cooling performance, showing an approximately 7% reduction in cooling performance on the flat plate relative to the baseline configuration. The time-resolved analysis of the velocity field revealed that increasing the CA intensifies flow fluctuations near the trench exit.