Film-cooling hole-geometry research needs a better understanding in the mechanism of film cooling effectiveness, which was recently shown to depend rather strongly on the counter-rotating vortex pair (CRVP); in this work, a mechanism of the film-cooling heat transfer is proposed. Its mainstream entrainment was aimed to be eliminated by developing a new scheme named comb scheme, which was intended to move CRVP away from mainstream-coolant interface, rather than suppressing CRVP itself. It is investigated experimentally and numerically in this work. The transient thermochromic liquid crystal technique was used in the experimental work, while the Reynolds-averaged Navier-Stokes equations coupled with a realizable kappa-epsilon turbulence model was used to simulate the flow numerically. The results were assessed against open published results hence demonstrating the so called 'ideal' performance (film cooling effectiveness = 1) of the new scheme, but with practical structural integrity. The geometric parameter analysis showed that the visualized strong CRVP, where intensity is more than 20, is trapped in the blind slot, hence its impact on mainstream-coolant interface is dropped to approximately 3, and mainstream entrainment is eliminated. It confirms the success of the comb scheme in achieving the high performance of the film-cooling heat transfer mechanism.
展开▼
