Large eddy simulation of film cooling flow from shaped holes with different geometrical parameters

Film-cooling approach is widely used in advanced gas turbines to protect the turbine components from the hot mainstream flow. The geometry of the cooling holes plays an important role in film cooling performance. In the current study, a large eddy simulation (LES) approach was performed to investigate the effects of various geometrical parameters of shaped cooling holes on the film-cooling effectiveness and turbulent flow characteristics. The reference cooling hole was located on a flat plate with a 35-degree injection angle at a constant density ratio of 1.5. The film-cooling effectiveness calculated by the LES approach was validated compared to that of the experimental data measured by PSP technique at different blowing ratios of M= 1.0, 1.5, and 2.0. Four important geometrical parameters, injection angle, metering length, forward expansion angle, and lateral expansion angle, were considered as design variables, and six different cases were designed and compared with the reference cooling hole. The computational data revealed that the cooling hole geometrical parameters significantly influence film-cooling performance. The designed shaped cooling hole showed an improvement in cooling performance of about 32% for the best case, compared to the reference case. In addition, the time/space analysis of the flow-field inside the cooling hole showed greater velocity fluctuations and more flow unsteadiness for the cooling holes with larger area ratios.