Experimental study of the overall cooling effectiveness of f-type impinging-film cooling configurations

Impinging film cooling as an efficient design of the cooling structure can be used in the combustor of high-performance aero-engines. In this work, experiments were implemented to investigate the overall cooling effectiveness of the F-type impinging-film structure concerning various geometric parameters and flowing factors. Effects of blowing ratio M, jet-hole diameter d, jet-to plate pitch z, and jet holes spacing y on the overall cooling effectiveness are investigated. Nine configurations with different non-dimensional impinging height Z(n) (1.5 <= Z(n)<= 3.2), non-dimensional jet hole spacing Y-n (1.96 <= Y-n <= 3.5), and jet hole diameter d (d = 1, 1.2, 1.6mm) are studied. Experiment results show that the overall cooling effectiveness eta increases with the increase of blowing ratios M, and this tendency becomes weaker as the blowing ratio M exceeds 1.31. The non-dimensional impinging height Z(n)=1.5 makes a high cooling performance at all blowing ratios M. The area-averaged cooling effectiveness of Z(n)= 1.5 is 2.1% higher than that of Z(n)=2.4 and is 3.2% higher than that of Z(n)=3.2 at M=1.31. The cooling effectiveness of Y-n =1.96 increases by 2% to 5% when compared to Y-n = 2.56 and Y-n =3.5. When the blowing ratio increases, the cooling effects of Y-n=1.96 and Y-n=2.56 are almost identical. At the same open percentage and cold air flow rate, the cooling effectiveness of d = 1.2mm is 0.8% similar to 2.5% higher than that of d = 1mm and is 2.3% similar to 6% higher than that of d = 1.6mm. Finally, using the experimental data, empirical correlations were proposed to fit the overall cooling effectiveness based on the flow and geometrical parameters.