Computational Predictions of Improved Upstream Film Cooling Hole Configuration For Converging Transonic Nozzle Guide Vane Endwall

Abstract

The following study uses computational fluid dynamics simulations to investigate the cooling performance of an improved upstream film cooling hole configuration for a transonic nozzle guide vane with an engine-representative contoured outer endwall. The simulations employed the Reynolds-Averaged Navier-Stokes equations and the Shear Stress Transport k-ω coupled with the transitional γ-Reθ turbulence closure model to resolve the flow field. Detailed analyses of the computational results are performed. Three different doublet staggered row hole configurations were analyzed with the coolant mass flow rate scaled accordingly: a baseline 46-hole uniform arrangement representative of in-engine designs, a 56-hole uniform arrangement, and a 56-hole non-uniform arrangement with close laterally spaced holes near the pressure side leading edge. The adiabatic endwall film cooling effectiveness was employed as the cooling performance metric. Comparisons of the film effectiveness distribution indicate that the pressure side (PS) throat endwall was inadequately covered for both the engine-representative baseline and 56-hole uniformly spaced configurations due to coolant migration from secondary flows. The 56-hole, non-uniform arrangement exhibited an 82% averaged improvement in effectiveness along the pressure side endwall relative to the engine-representative baseline because it increased coolant availability in the secondary flow dominant region and developed a more coherent coolant film that reduces mixing with the mainstream flow. Overall, the results demonstrate that non-uniform film cooling hole arrangements, with close lateral spacing near the PS, can greatly enhance PS endwall coolant coverage, and should be considered in future upstream film cooling hole designs.