Transient film outflow performances of laminated cooling configurations in leading edges of turbine vane

Abstract

In this work, time-resolved quantitative light sheet technique is used to capture the transient outflow performances of the laminated cooling in turbine vane leading edges. A series of numerical simulations are performed to deeply understand the intrinsic flow and heat transfer mechanisms. Two laminated structures are compared, one is a traditional design with uniform hole-diameter (UD), and the other contains non-uniform hole-diameters (NUD) with locally-enlarged film and impingement holes on pressure side. Time-averaged results show that NUD can obtain a higher film effectiveness and a better film coverage due to the decreased momentum of cooling air-jet, and the relative improvement from UD can achieve 58.7%. The unsteadiness analysis of transient film is conducted by quantifying the standard deviation of instantaneous data, and it shows that the fluctuation of cooling air-jet mainly originates from Kelvin-Helmholtz instability at mainstream/coolant interfaces and separation vortex. The new design of NUD can also obtain a low near-wall unsteadiness level, because the separation vortex disappears on target surface, which implies a lower risk of thermal damage. Moreover, the mass flow rate of cooling air is an important factor on transient film performance, which can aggravate the separation of cooling air-jet and cause a higher unsteadiness level.