Measured Film Cooling Effectiveness of Three Multihole Patterns

As an advanced cooling scheme to meet increasingly stringent combustor cooling requirements, multihole film cooling has received considerable attention. Experimental data of this cooling scheme are limited in the open literature in terms of different hole patterns and blowing ratios. The heat-mass transfer analogy method was employed to measure adiabatic film cooling effectiveness of three multihole patterns. Three hole patterns differed in streamwise row spacing $(S)$⁠, spanwise hole pitch $(P)$⁠, and hole inclination angle $(α)$⁠, with the first pattern $S∕P=2$ and $α=30°$⁠, the second $S∕P=1$ and $α=30°$⁠, and the third $S∕P=2$ and $α=150°$⁠. Measurements were performed at different blow ratios $(M=1-4)$⁠. Streamwise coolant injection offers high cooling protection for downstream rows. Reverse coolant injection provides superior cooling protection for initial rows. The effect of blowing ratio on cooling effectiveness is small for streamwise injection but significant for reversion injection.