Flat plate film cooling with linear and curved round-to-diffusion shaped slots using PSP measurement technique

This paper experimentally examines the effect of hole shape and coolant trajectory on film cooling effectiveness by using PSP measurement technique. Three different density ratios DR = 1, DR = 1.5, and DR = 2 were tested with five blowing ratios ranging from M = 0.5–1.5 with an increment of 0.25. Three different hole geometries (round to slot, round to annulus, and round to annulus2) were used with linear and projectile trajectories. Results obtained agreed with the general trend of shaped holes. In terms of hole shape, the slot-shaped hole resulted in better performance as compared to annulus shaped holes. Particularly, the slot-shaped hole with projectile trajectory results in 30–35% increase in effectiveness as compared to its linear trajectory slot-shaped counterpart. This design is found to have lowest discharge coefficient, but it works best at DR = 2. A correlation was also developed for single row different exit shaped holes helping the designers to calculate the spanwise effectiveness at different conditions.