Three types of expanded shape film-cooling holes were designed to study the change of the film cooling efficiency

heat transfer coefficient at the wall and flow discharge coefficient with the blow ratio.The result shows that: the film cooling efficiency and heat transfer coefficient of the expanded film cooling holes are higher than the typical round film cooling holes

but the flow discharge coefficient is lower.The effect of the streamwise expanded angle on the film cooling effectiveness and heat transfer coefficient is more remarkable than the laterally angle

which expands the area of the low pressure near the edge of the holes

leading to lower flow discharge coefficient.