Experimental and numerical investigation on the film cooling performance of the novel B-shaped and C-shaped holes

The shape of film holes is a key factor determining cooling characteristics. This study introduces two novel curved expansion configurations: B-shaped and C-shaped holes, which are developed through modification of widely used laidback fan-shaped and fan-shaped holes. Experimental and numerical investigations were conducted to analyze their cooling performance and flow structures. Adiabatic film cooling effectiveness measurements employed pressure-sensitive paint technology, while numerical simulations utilized the Realizable k-ε model to solve RANS equations. Tests were conducted on a flat plate model with a hole diameter-based Reynolds number of 10000, a density ratio of 1.5, and five blowing ratios from 0.5 to 2.5. Film holes were set at a 45° injection angle with no compound angle. Outlet spanwise widths of B-shaped, C-shaped, and baseline holes were all 2.7D. Results demonstrate maximum cooling effectiveness improvements of 43% for B-shaped holes and 20% for C-shaped holes compared to baseline shaped holes with equivalent outlet spanwise width, confirming their enhanced cooling potential. Performance enhancements originate from successful anti-counter-rotating vortex pair generation. The B-shaped configuration produces shorter yet wider and more uniformly distributed coolant coverage, while the C-shaped hole shows comprehensive improvements over the baseline. Both configurations exhibit maximum sensitivity to outlet spanwise width, with larger widths consistently improving cooling performance.