Large eddy simulation of film cooling on turbine vane

Abstract

Large eddy simulations were performed for film cooling on scaled-up C3X turbine vane at the nominal blowing ratio of M=0.5~1.5, and the Reynolds number, Re=3000, based on the mainstream inlet velocity and hole diameter. On the pressure surface, large-scale coherent structures including hairpin vortexes and horseshoe vortexes are generated in film-cooling flow fields. Hairpin vortexes promote the mixture between hot mainstream and coolant jet and degrade cooling performance. The anti-entrainment of horseshoe vortexes improves the lateral-covering capability of coolant jet in the near-field region and results in the formation of a pair of low-temperature strips wrapped around the hole at high blowing ratio. On the suction surface, the transition of the boundary layer takes place in the downstream of cascade throat but in the upstream of the discharged hole, plenty of broken vortexes dominate film-cooling flow fields. The distribution of turbulent kinetic energy also indicates that the coolant jet from the suction surface generates higher turbulent intensity than that from the pressure surface. For pressure signals for film cooling on the suction surface, small-scale and random fluctuation takes the dominant role. For pressure signals for film cooling on the pressure surface, a dominant frequency corresponding to Strouhal number St≈2.1 both exists at low and high blowing ratios. The film-cooling system on the suction surface exhibits a higher random degree than that on the pressure surface.

Keywords

• film cooling
• gas turbine
• boundary layer
• large eddy simulation
• coherent structures