Numerical evaluation of showerhead film cooling aerothermal performance on a first-stage vane

A wide set of experimental data has been used to validate numerical simulations of leading edge film cooling in a high-pressure turbine vane, according with steady-state RANS and delayed detached-eddy simulation (DDES) modelling. A typical showerhead configuration was adopted, namely 4 staggered rows of cylindrical holes. Boundary conditions were fully based on the wind tunnel tests: low speed flow (exit isentropic Mach number of Ma2is = 0.2), low inlet turbulence intensity of Tu1 = 1.6% and low density ratio of DR ∼ 1 were dictated by constraints relating to Particle Image Velocimetry (PIV) setup. One only blowing ratio of BR = 3.0 was taken into account since it is representative of effective thermal protection, while offering a challenging scenario of jet separation and reattachment on a curved surface. Predicted off-the-wall aerodynamic features of the flow in the leading edge region were compared against PIV data and flow visualizations. Moreover, contours of adiabatic effectiveness, measured with the pressure sensitive paint (PSP) technique by injecting nitrogen as coolant (DR ∼ 1), were computed by means of the species transport model (i.e. mass transfer (MT)), in addition to the conventional thermal method (i.e. heat transfer (HT)). The MT approach yielded more accurate predictions of adiabatic effectiveness (η) than the alternative HT method. Therefore it can be considered particularly suited to the validation of the PSP experimental results. DDES was indispensable to capture the highly unsteady, anisotropic mixing of the cooling jets with the mainstream, despite overestimation of the jet vertical penetration, and hence slight underprediction of η outside the showerhead region.