Experimental investigation of the influence of film cooling hole diameter on the total cooling effectiveness for cyclone-cooled turbine blades

Cyclone cooling is a promising method for a more effective internal cooling of turbine rotor blades with simplified internal channels including a swirling flow to enhance internal heat transfer. Previous studies have led to the conclusion that improving the cooling performance requires an adapted film cooling design, tailored to the cyclone cooling application. In this paper, a turbine rotor blade with realistic, complex features including the cyclone cooling design is investigated experimentally using infrared thermography to capture surface temperature. The objective is to analyze the influence of increased film cooling hole diameter on a cyclone-cooled blade’s surface temperature. For this purpose, the diameter of the holes at the blade’s leading edge, which are fed by the cyclone channel, is increased. The tests are performed for different coolant mass flow rates and swirl numbers. Additionally, CFD simulations are performed to analyze the aerodynamics of the cooling air. The test results show that the surface temperature at the leading edge can be decreased by increasing the diameter of the film cooling holes, however, adversely affecting the remaining blade surface. This can be explained by a redistribution of the supplied coolant. The increase of cooling effectiveness at the leading edge is at the highest when a low swirl is generated.