Краткое описание

Blades and vanes for advanced gas turbines are cooled externally by film cooling. In order to attain higher film cooling effectiveness, it is important to understand the mixing phenomena of film-cooling air with mainstream hot gas. Today, shaped film-cooling holes are used as film-cooling holes, but the shaped film-cooling holes have many geometric parameters and the effects of shaped film-cooling holes have not been studied entirely. In addition, the instantaneous flow field of film cooling is extremely complicated because it is accompanied by many vortices generated by strong shear at the interface between the mainstream and the coolant jet. In this paper, using the optimized shaped film-cooling holes, as given by CFD, and a conventional circular hole, the detailed mixing mechanism of film-cooling air with mainstream was examined by LIF and PIV using a low-speed wind tunnel. By these methods, instantaneous fields of film cooling effectiveness were successfully obtained with high resolution, which clarified the fine structure of the temperature field at the shear layer. In addition, unsteady numerical simulations have been performed to examine the detailed mechanism of the mixing process, using the Detached Eddy Simulation as a LES/RANS hybrid model.