Investigation of Heat Transfer and Vortex Dynamics in Relation to Film Cooling Effectiveness of Cratered Injection

A thorough numerical analysis of of cratered injection holes which are frequently seen in turbine blades with thermal barrier coatings (TBCs)-is presented in the current research.During the TBC application process, injection holes are typically masked, resulting in a characteristic cratered geometry where the hole is surrounded by a raised layer of coating.This alteration in surface topology is expected to influence the flow behavior and cooling effectiveness compared to standard cylindrical holes.The objective of this research is to evaluate the influence of such cratered geometries on film cooling effectiveness and associated vortex dynamics.Threedimensional simulations are performed using the k- to resolve the flow field and thermal characteristics.The study is conducted at a fixed mainstream Reynolds number, based on the freestream velocity and hole diameter.Film cooling effectiveness is evaluated for both cylindrical and off-centered forward cratered (OCFC) holes across three blowing ratios (BR): 0.6, 1.0, and 1.4.Air is used as the coolant, maintaining a density ratio of 1.14.The results indicate that cratered holes consistently yield higher area-averaged film cooling effectiveness in comparison to cylindrical holes.The enhancement is attributed to the altered vortex structures and improved lateral spreading of the coolant film induced by the crater geometry.The most significant performance gain is observed at BR = 1.0 with lower vorticity, where cratered holes exhibit up to a 48% improvement in cooling effectiveness.