Compensating cooling on the suction surface of the blade by the jets of the film holes on the endwall

The coolant ejected from the film holes on the gill region of the blade deflects to the blade tip in the action of the cascade passage vortices, resulting in the local film cooling failure on the suction surface near the endwall. This paper introduces an improved strategy for compensating the film cooling on the suction surface near the endwall by using the passage vortices to entrain coolant inject from endwall jet. The film effectiveness of two rows of film holes on the gill region was measured by pressure-sensitive paint (PSP) technique to be as the baseline. Film hole layouts on the endwall were examined, including 3 single-hole cases, 3 double-hole cases, and 1 three-hole case, totaling 7 film hole layouts. The compensating improvement of film cooling on the suction surface was examined at the blowing ratios ranging from 0.50 to 1.75. The mechanism of compensating cooling was analyzed by numerical simulation. The correction equation of compensating cooling was established based on the experimental data. The results show that the compensating film effectiveness of single-hole B or hole C is higher than that of single-hole A in the film failure region at all blowing ratios. Single-hole C exhibits a significant improvement in film effectiveness by 0.032 at the high blowing ratio of 1.75. The film effectiveness of the combination of hole B and hole C is higher than those of the other combinations, with the largest improvement of film effectiveness by 0.028 at the blowing ratio of 1.75.