Effects of film cooling hole shape on heat transfer

The effects of hole shapes, secondary injection Reynolds numbers, and blowing ratios on the heat transfer downstream of film cooling holes have been investigated by using a large-scale low-speed loop wind tunnel. The test model consists of five film cooling holes. Experiments on dustpan-shaped holes, fan-shaped holes, and round holes have been conducted with injection Reynolds number ranging from 10,000 to 25,000 and blowing ratio ranging from 0.3 to 2.0. Measurements are taken under 26 conditions. Results show that the critical blowing ratio is 1.3 for the dustpan- and fan-shaped holes, 0.7 for the round holes. The turbulence generated by air injection through round holes is stronger than those through dustpan- and fan-shaped holes.