抄録
The cooling effectiveness of gas turbine blades by film cooling was examined. Air at 420 K flowed in the rectangular test flow channel of 60 mm wide, 60 mm high and 350 mm long. Air at room temperature for the film cooling flowed into the test flow channel through a hole at the bottom. The effect of the shape of the effluent hole for the cooling flow on the cooling effectiveness was examined. The shapes examined were circular and oblong-circular. The effect of mist introduction into the cooling flow was also examined. Experimental results were analyzed with the STAR-CD code. Since the film cooling flows from the oblong-circular holes spread wider than from the circular hole, better cooling effectivenesses were maintained in the wider area in the cases of the oblong-circular holes than the case of the circular hole. In the case of the circular hole, the flow separation occurred near the effluent flow hole, which resulted in the lower cooling effectiveness than in the cases of the oblong-circular holes. The deterioration of the cooling effectiveness occurred in the larger effluent flow in the case of the circular hole. Results of the STAR-CD analyses proved that the vortex that existed at the edge of the cooing film flow and rolled the main flow into the cooling film was kept farther away from the center of the cooling film and made weaker in the oblong-circular hole case than in the circular hole case. These might result in the better cooling effectivenesses in the cases of the oblong-circular holes. The introduction of mists into the film cooling flow produced the remarkable improvement of the cooling effectiveness. It might be caused by a decrease in the temperature of the cooling film and an increase in the velocity of the cooling film flow due to the evaporation of the mists.
