Numerical Investigation of the Effect of Coolant Injection Angle on the Pulsed Film Cooling Effectiveness of Square Wave Flow on Flat Plate

In this paper, effect of the angle of injection on the film cooling effectiveness with square wave pulsation is investigated at various frequencies. Four angles of injection are selected at 20, 25, 30 and 35 degrees. Film cooling is used to cool turbine blades and extend life of blade. The pulsed flow is investigated at three frequencies of 2, 50 and 500 Hz. Finite volume method was used to solve governing flow equations. The SST k-ω model was used for modeling turbulence. results showed that injection angle between 20 and 25 degrees in three frequencies studied had the most film cooling effectiveness of the central and lateral line, especially in the areas far from the edge of the hole. Higher frequencies increase the effectiveness of film cooling at the lower initial distances of the hole. At far distances, the lower frequency is the most effectiveness. The largest difference in centerline effectiveness was achieved at frequency of 500 Hz , and between angles of 20 and 35 degrees, and this value was 64.3%. This value was 98.9% for laterally effectiveness . As the frequency increases, interruptions of flow-off and flow-on are reduced, and as a result, the instantaneous effectiveness also has a slower variation than the lower frequencies. The blowing ratio of 0.5 had the most value in comparison with blowing ratio of 0.75 and 1 in all angles and frequencies. The maximum difference in effectiveness, at blowing ratio of 0.5 , in comparison with other two blowing ratios, was 187.4%.