A comprehensive investigation of the effect of hole diameter and number on film cooling performance of rotating blade leading edge

The combined effect of film hole number and diameter on the film cooling were investigated on the rotating blade leading edge by using experimental and numerical methods. The film cooling performance was obtained by pressure sensitive paint technique under rotational condition. To better understand the experimental results, the flow fields obtained from numerical simulation were also analyzed. The effects of hole length-to-diameter ratio (L/d = 2.5/5/7.5), hole number (N = 7/9/10/11/13), hole diameter(d = 0.64∼1.26 mm), Hole to hole pitch, (P/d = 6.3∼9.2) and hole exit area (A_hole/A_LE=4 %-14 %) on the film cooling performance are investigated. Five blowing ratios are also employed (M = 0.5 to 2.0). The results indicate that the hole length-to-diameter ratios (L/d = 2.5∼7.5) have a negligible influence on the film cooling effectiveness. Both the film hole number (N = 10/13) and the hole diameter (d = 0.64/0.75 mm) monotonically affect the film cooling performance under each blowing ratios. However, a comprehensive study indicates that there is a significant quadratic correlation between the area-averaged cooling effectiveness and the total film hole exit area for different combinations of hole number and diameter. Meanwhile, there is an optimal film hole exit area on the leading edge and it increases as the blowing ratio or mass flow rate increases.