IMPACT ON ADIABATIC FILM COOLING EFFECTIVENESS USING INTERNAL CYCLONE COOLING

The internal heat transfer of turbine blades can be augmented using cyclone cooling, but the consequential impact on the external film cooling may be significant. To determine these effects, the distribution of adiabatic film cooling effectiveness was measured on the surface of a symmetrical blade model containing a cylindrical leading-edge channel. This channel feeds one row, respectively two opposite rows, of eight cooling holes each. Inside this channel two different types and directions of swirl are generated. The resulting adiabatic effectiveness distributions, which are measured using the calibrated ammonia diazo technique, are compared to those measured with a channel flow without swirl (datum configuration). The operating points are defined by blowing ratio (0.6-1.0) and film cooling discharge coefficient (20%-50%). A high full-range resolution over the adiabatic effectiveness is achieved using a weighting average method with multiple experiments per operating point. The lateral-averaged adiabatic effectiveness is presented up to 30 diameters downstream of the cooling holes. These effectiveness values show a high dependency on the configurations and reach values of about 0.3 to 2 times the reference configuration values. This is due to the strong variation of the flow structure inside the cooling holes. PIV-measurements and basic numerical simulations of the channel flow structure and dynamic pressure measurements at the cooling hole exits are carried out to support the results of film cooling effectiveness.