Experimental investigation on effects of cross-flow Reynolds number and blowing ratios to film cooling performance of the Y-shaped hole

Abstract

This paper presents an experimental investigation on effects of cross-flow Reynolds number and blowing ratios to film cooling performance of the Y-shaped hole. Flow resistance measurements were carried out to obtain the discharge coefficient. The film cooling effectiveness and heat transfer coefficient were measured by the transient liquid crystal measurement technique under three blowing ratios of 0.5, 1.0 and 2.0, respectively. The cross-flow Reynolds numbers of was fixed as 50,000 and 100,000, respectively. Numerical simulations with realizable k-ε turbulence model and enhanced wall treatment were performed to analyze the flow mechanism. Results demonstrate that the Y-shaped hole produces the higher film cooling performance than the cylindrical hole. For the Y-shaped hole, a reduction in the discharge coefficient with the increasing cross-flow Reynolds number is displayed. Meanwhile, the discharge coefficient increases with the increasing blowing ratio. It can be attributed to the enhancement of suction effect as well as the weakness of the blockage. The large blowing ratio results in better film coverage effect and higher film cooling effectiveness. The cross-flow Reynolds number has a significant effect on the film cooling effectiveness at the large blowing ratio. The heat transfer coefficient ratio increases with the increasing cross flow Reynolds number and the increasing blowing ratio. At all blowing ratio, the laterally averaged NHFR is valued between 0 and 0.6 in the hole downstream region, which means a positive effect of the film cooling performance. Under two different cross-flow Reynolds numbers, NHFR shows the trend of increasing firstly and then decreasing with the increasing blowing ratio. In the range of blowing ratio M< 1.4, the NHFR decreases with the increasing cross-flow Reynolds. In the range of blowing ratio M> 1.4, the NHFR increases with the increasing cross-flow Reynolds number. Compared with the cylindrical hole, under the same conditions, the Y-shaped hole have higher film cooling effectiveness, lower heat transfer coefficient, and higher discharge coefficient.