Trailing Edge Cooling of Gas Turbine Airfoil Using Blockages With Straight and Inclined Holes

This paper describes the detailed experimental studies of heat transfer enhancement and pressure loss characteristics internal cooling passages using single, double and triple blockages equipped with straight and inclined holes. The blockage consist of 7 holes with the diameter, D = 6.35mm, which is 0.5 of the height of the channel. Three different hole inclination angles ranging from 0°, 15° and 30° from the horizontal plane are explored. The case with straight holes (0°) is considered as baseline case, while the cases with inclined holes are introduced to enhance heat transfer performance. The transient liquid crystal technique is employed to deduce the heat transfer coefficient on the internal cooling channel, while the pressure loss of the entire channel is measured using pressure taps connected to the digital manometer. Numerical analysis is later performed using ANSYS CFX, based on the shear stress turbulence (SST) model to provide detailed insights about the flow field in the channel, which explains the heat transfer phenomena caused by varying the hole inclination angle. The heat transfer performance of the blockages is higher than conventional configuration using vortex generators, i.e., pin-fins by approximately two folds, while accompanied by much higher pressure loss. The proposed inclined holes array exhibits more effective impingement effects resulted in a substantial cooling performance compared to the baseline case by approximately 50%. This design can be applicable to the trailing edge of gas turbine airfoils, which can provide high heat transfer rate and pressure loss from repeated significant area contractions.