Micro Cooling Performance of Effusion and Transpiration Air Cooling Using C3x Turbine Blades

A great number of studies have been conducted on a film cooling for turbine blade, which is to prevent thermal damage on gas turbine blades originated from high turbine inlet temperature. However, film cooling with several rows of cooling-holes results in lift-off of cooled film and limited cooling effect on specific area at which flow reattachment occurs. In this study, effusion and transpiration cooling methods were applied to the well-known C3X turbine blade. A multiple cooling hole-array for an effusion cooling was fabricated on the surface of C3X blade by the electric discharging machining (EDM), and a porous structure for transpiration cooling was manufactured by the metal 3D printing, which is recently spotlighted as an additive manufacturing. Micro cooling experiment using effusion and transpiration cooling method was measured in the high-temperature subsonic wind tunnel, which has freestream temperature of 100^oC and velocity of 20 m/s. The surface temperature of the air-cooled C3X blade was measured using IR thermometry with a specially designed protocol for accurate measurement that eliminates background radiation errors from high-temperature surroundings. The surface cooling temperature and cooling effectiveness distribution were quantitatively analyzed on the pressure side, the suction side and the leading edge of the C3X blade. Transpiration cooling is expected to achieve high cooling effectiveness with less amount of coolant than effusion cooling. The measurement result showed that the cooling effectiveness of 0.46 for effusion cooling was achieved at a coolant flow rate of 400 LPM, whereas transpiration cooling exhibited the cooling effectiveness of 0.44 at 200 LPM (similar cooling effectiveness with only half of the coolant flow) and that of 0.57 at 400 LPM.