A Novel Transition-Sensitive Conjugate Methodology Applied to Turbine Vane Heat Transfer

Abstract

A documented numerical methodology for conjugate heat transfer was employed to predict the metal temperature of an internally-cooled gas turbine vane at realistic operating conditions. The conjugate heat transfer approach involves the simultaneous solution of the flow field (convection) and the conduction within the metal vane, allowing a solution of the complete heat transfer problem in a single simulation. This technique means better accuracy and faster turn-around time than the typical industry practice of multiple, decoupled solutions. In the present simulations, the solid and fluid zones were coupled by energy conservation at the interfaces. In the fluid zones, the Reynoldsaveraged Navier-Stokes equations were closed with a three-equation, eddy-viscosity model, developed in-house and previously documented, with the capability to predict laminar-to-turbulent boundary-layer transition. The single-point model is fully-predictive for transition and requires no problem-dependent user inputs. For comparison, a simulation was also run with a commercially available Realizable k-ε turbulence model. A high-quality, unstructured gird was employed in both cases. Numerical predictions for midspan temperature on the airfoil surface are compared to data from an open-literature experiment with the same geometry and operating conditions. The new model captured transition of the initially laminar boundary layer to a turbulent boundary layer on the suction surface. The results with the new model show excellent agreement with measured data for surface temperature over the majority of the airfoil surface. The new model showed a marked improvement over the Realizable k-ε model in all regions where laminar boundary layers exist, highlighting the importance of accurately modeling transition in turbomachinery heat transfer simulations.