Effects of Slot Width and Injection Angle of the Inclined Slot on the Film Cooling Effectiveness of a Flat Plate

The present study was carried out to examine the effects of slot width and injection angle of an inclined slot on the film cooling effectiveness. Three levels of variation were adopted for each design parameter (the wall thickness-to-slot width ratio H/S=5.0, 7.0, and 15.0, and injection angle α =30 °, 45 °, and 60 °). Film cooling effectiveness was measured using the pressure sensitive paint technique in a flat plate test rig under 30 m/s of mainstream velocity condition. Four blowing ratios (M=0.25, 0.5, 0.75, and 1.0) defined as the mass flux ratio between the coolant and the mainstream were considered. Carbon dioxide gas was used as the coolant, resulting in a coolant-to-mainstream density ratio of approximately 1.5. The results showed that higher film cooling cooling effectiveness was observed for a wider slot at a constant blowing ratio condition because more amount of coolant was injected through the wider injection area. In contrast, a narrower slot had a benefit for film cooling effectiveness at a constant mass flow ratio condition. Results also indicated that a steeper injection angle caused lower film cooling effectiveness due to stronger mixing between the coolant and the mainstream.