Experimental investigation on the effect of hole diameter on the leading edge region film cooling of a twist turbine blade under rotation conditions

Film cooling performance on the twist turbine blade leading edge (LE) model has been experimentally investigated employing the thermochromic liquid crystal (TLC) technology under rotation conditions. The novelty of this paper is the earlier study on the effect of film hole diameter (d = 0.4 mm and 0.5 mm) on the LE region of a rotating twist blade. The effects of blowing ratio (M) and density ratio (DR) were also considered. M ranged from 0.5 to 2.0 when DR = 1.56 and M ranged from 0.5 to 1.25 when DR = 1.04. The whole experiment was conducted at the rotating speed of 574 r/min with the Reynolds number of 63,400. Results show that the film hole diameter of leading edge has a significant effect on the spanwise average film cooling effectiveness. The spanwise effectiveness provided by the larger DR (1.56) increases with increasing hole diameter in the whole range of −4.3d to 3.75d at M = 0.5, 1.0 and 1.5. When DR = 1.56, the spanwise effectiveness increases monotonically with increasing blowing ratio in the whole range of −4.3d to 3.75d under the condition of d = 0.4 mm case, and it increases first and then descends with increasing blowing ratio in the whole range except −3.3d to −0.5d with the best M = 1.5 under the condition of d = 0.5 mm case. The area average film cooling effectiveness provided by the larger DR (1.56) is higher than that provided by the smaller DR (1.04) when M = 0.5 and 1.0 for the d = 0.5 mm case. More results on the influence of hole diameter, blowing ratio and density ratio are shown in this paper.