عنوان مقاله [English]
In this study, numerical analysis has been employed to investigate of upstream ramp effects on the flow and thermal field of incompressible, steady, turbulence three dimensional film cooling through a single row of inclined cylindrical and fan-shaped hole. The computational methodology includes the use of a structured, non-uniform hexahedral grid consisting of the main flow channel, the coolant delivery tube and the feeding plenum. The Low Re K- model is adopted as the turbulence model. In the present study, computations are performed for the flowing range of film cooling parameters: streamwise injection angle 35 deg; film-hole length-to-diameter ratio of 1.75; blowing ratio of 0.5, 1, 1.5 and 2 and density ratio of 1.6. The results show that at lowest blowing ratio (M=0.5) the presence of the upstream ramp for cylindrical hole is in useful. The fan-shaped hole creates better film cooling performance in all blowing ratio compared with the cylindrical hole. As well as in both cases, the fan-shaped and cylindrical hole, the upstream ramp improves the film cooling effectiveness by incrementing blowing ratio. Last but not least, an optimum film cooling geometry for studied cases is occurred on flat plate model by fan-shaped hole at blowing ratio of 0.5.