The distribution of film cooling effectiveness for staggered double-row discrete holes has been measured extensively over the whole area of convex surface. It has been found that whether or not the blowing ratio of first row is equal tothat of the second one

higher blowing ratio causes stronger separation of the film jet

the cooling effect is thus reduced remarkably

and the optimized value of the blowing ratio for better film cooling effectiveness is M≤0.5.Experimental results show that for convex surface the blowing ratio of first row should be smaller than that of second row in order to get better cooling results

for example Mf=0.3. The distance between cooling holes as well as the blowing ratio M should be both smaller on the convex surface.