Mach Number and Freestream Turbulence Effects on Turbine Vane Aerodynamic Losses

Abstract

The aerodynamic performance of a smooth. cambered turbine vane (which replicates one used in an operating gas turbine engine) is investigated in this paper. Three different Mach-number distributions are employed, which result in one transonic flow and two subsonic flows. All of these distributions match flow conditions in different industrial applications. A fine mesh grid and cross bars are used to augment the magnitudes of longitudinal turbulence intensity at the inlet of the test section. Wake-profile data are presented for two different locations downstream of the vane trailing edge (one axial chord length and 0.25 axial chord length). The contributions of varying Mach number and varying freestream turbulence intensity to aerodynamic losses, normalized kinetic energy profiles, normalized Mach-number profiles, integrated aerodynamies losses, and area-averaged loss coefficients are quantified. Results show that wake profiles are more sensitive to turbulence intensity variations at lower subsonic flow conditions than when transonic flow is present. Wake profiles are also broadened either as the exit Mach number increases or as the freestream turbulence intensity level increases. Higher losses in the freestream flow are present as the inlet turbulence intensity level increases. Also described are effects of increased turbulent diffusion, streamwise development, and profile asymmetry. Corresponding integrated aerodynamic losses and area-averaged loss coefficient Y A magnitudes increase with increasing Mach number or with increasing turbulence intensity level. Results additionally show larger loss magnitudes with flow turning and cambered airfoils, relative to symmetric airfoils, when compared at the same exit Mach number.