Aerothermal performance of double-jet film cooling in multidirectional crossflow

Advanced gas turbines employ combined internal and external cooling structures to protect their blades from heat generated during their operation. However, the impact of internal crossflow on aerodynamic heat transfer performance during double-jet film cooling, a promising external cooling technology, has received limited research attention. To address this gap, this study examines a configuration in which double-jet film cooling holes are located in different coolant chambers or stages of serpentine or U-shaped passages. A simplified flat-plate model was used to evaluate four crossflow cases, incorporating two crossflow Reynolds numbers (Re = 125,000 and 250,000) and four blowing ratios (M = 0.5–2.0) through numerical simulations. This study compares film-cooling effectiveness, discharge coefficient, and aerodynamic loss across the cases, summarizes how they vary with respect to blowing ratio and crossflow Re, and analyzes the underlying mechanisms based on the flow field and vortex structures. Results indicated that the crossflow supply direction substantially affected film cooling performance at low blowing ratios. Optimal film cooling occurred at M = 1.0 under both crossflow Re conditions. A 6% difference in area-averaged film-cooling effectiveness was observed between Cases 2 and 4 at an Re of 250,000. Crossflow Re also strongly influenced film cooling performance, with Case 2 showing a 31.5% variation in area-averaged film-cooling effectiveness between the crossflow Re conditions at an M of 0.5. In addition, Case 3 exhibited the highest mixing entropy generation, whereas Case 2 exhibited the lowest. These findings provide guidance for designing air-cooled turbines.