Effects of upstream ramp on the performance of film cooling

Described in this paper is an experimental study on a concept for enhancing the film cooling performance by placing an upstream ramp in front of a row of film cooling holes. Parameters studied include upstream ramp angle (8.5°, 15°, and 24°) and blowing ratio M (0.3, 0.4, 0.6, 0.9, and 1.4). Detailed local film cooling effectiveness and heat transfer coefficient are measured using the infrared imaging technique. The results indicate that film cooling characteristics in the region downstream of the film cooling holes are sensitive to the combination of ramp angle (height) and blowing ratio. In general, a large ramp angle with a high blowing ratio leads to more effective film protection. Transport phenomena in the region link closely to the interaction between the coolant injection and the separated flow behind the ramp.