Large eddy simulation of film cooling effectiveness on a turbine vane pressure side with a saw-tooth plasma actuator

Abstract

The effects of a saw-tooth plasma actuator (STPA) on the pressure side film cooling in a turbine vane have been studied by using large eddy simulation. The phenomenological plasma model was adopted to solve the electrohydrodynamic (EHD) force vector generated by the STPA, which was placed downstream of the cooling hole. The time-averaged flow fields without and with the STPA are comparatively analyzed, and results show that the jet flow reattaches to the pressure surface earlier owing to the EHD force vector. Furthermore, the momentum injection effects of the STPA reduce the jet lift-off caused by the counter rotating vortex pair (CRVP) and help the wall vortex pair entraining more coolant to the pressure surface. Then the spatial-temporal evolutions of coherent structures are presented in conjunction with the variations of the centerline temperature, which show that the elongated CRVPs are the dominated flow patterns of the film cooling, and they reduce in the structure size and extend farther downstream distance due to the STPA aerodynamic actuation. Consequently, the intermittent coherent structures are shed from the tail end of the CRVPs later. Moreover, the coherent structures are reduced in the structure size and intermittency because of the STPA aerodynamic actuation, and the centerline temperature is varied with their developments while approaching downstream. Finally, the iso-surfaces of the transient temperature qualitatively and quantitatively indicate that the STPA aerodynamic actuation enlarges the wall-coverage of the coolant. Overall, the STPA aerodynamic actuation greatly improves the film cooling effectiveness by regulating the evolutions of the large scale coherent structures, especially in the range of 40% to 60% blade axial chord.