Effect of unsteady wake on linear cascade film cooling efficiency

The effect of unsteady wake on film cooling effectiveness was experimentally determined. A squirrel cage type wake generator produced the unsteady wake. Experiments were performed in a low-speed wind tunnel at the Reynolds number of 5.04×10~4,1.08×10~4,and at the wake Strouhal number of 0.04～0.18. Results show that an increase in the wake Strouhal number causes a decrease in film effectiveness at the Reynolds number of 5.04×10~4, but at the Reynolds number of 1.08×10~5, the wake of wake generator with 6mm rod causes an increase in film effectiveness. Unsteady wake affects film cooling effectiveness by two ways.One is to disturb the film cooling layer, the other is to change the local blowing ratio.