Enhanced film cooling and flow disturbance of an AGTB turbine cascade with plasma aerodynamic actuation at film-holes outlets

A kind of plasma actuators is introduced at holes outlet on the pressure and suction sides of an AGTB cascade. Plasma aerodynamic actuation on film cooling enhancement and flow characteristics around film holes is investigated by numerical simulations. Results show that when plasma actuators are opened, the backflow region behind the film hole decreases, and the intensity and scale of two-pairs vortices decrease. With the increment of applied voltage, flow attachment location of the coolant air advances, and the normal height from the wall of the coolant air decreases at the same position. Due to the energy injection effect of plasma, peak turbulent kinetic energy near the wall increases sharply and becomes 5.4% higher than that without plasma. The plasma has minimal effect on the suction side film cooling performance subject to an adverse pressure gradient. Thinner thermal boundary layer on the pressure side tremendously strengthens the heat transfer capacity between the coolant air and blade wall. The averaged spanwise film cooling effectiveness increases by 20.6%-92.4%, and the maximum film cooling effectiveness with opened plasma increases by 64.2%-139.6% at 6 kV-36 kV of applied voltages. Pressure-side film cooling performance reaches the optimum at 24 kV while is reduced once applying excessive voltages. The sensitivity of the applied voltage to film cooling performance decreases gradually as the blowing ratio is increased.

Automated summary

Numerical simulations were conducted to investigate the effects of plasma actuators on film cooling enhancement and flow characteristics around film holes. The results showed that opening the plasma actuators reduced the backflow region and the intensity and scale of vortices. The applied voltage affected the flow attachment location and the height of the coolant air, and the plasma injection increased the turbulent kinetic energy near the wall. The film cooling effectiveness increased significantly on the pressure side and had minimal effect on the suction side. The sensitivity of the applied voltage decreased with increasing blowing ratio.