Experimental study of combined influences of wall curvature and compound angle on film cooling effectiveness of a fan-shaped film-hole

Abstract

Deep discussions of the combined influences of compound angle (CA), wall curvature and cooling air flowrate on the film effectiveness of a typical fan-shaped-hole as well as the cooling unsteadiness level were conducted, to acquire the proper cooling schemes in different regions of turbine blade. Typical CAs of 0°, 30° and 60° were designed at convex, concave, and flat walls. Blowing ratio (BR) of coolant-to-mainstream varied from 0.5 to 3.0. Both the turbulent dissipation and vorticity of secondary vortices determine the CA effect on film effectiveness. The 30°-jet can achieve the highest film effectiveness, and such trend is non-sensitive to the BR and wall curvature. The CA-induced largest increment can reach about 50%. The wall curvature effects on film effectiveness can be obviously changed by the CA. Relative to the flat wall, the angled jet at convex wall can generate the largest increments of 26%. In general, the fan-shaped-hole with CA = 30° is strongly proposed at the convex wall, due to the highest film effectiveness and the lowest cooling unsteadiness level. However, the angled-holes at the concave wall can produce a negative influence on the durability, due to the increment in unsteadiness-level above 20% relative to the other walls.