Three-Dimensional Conjugate Heat Transfer Simulation of an Internally-Cooled Gas Turbine Vane

Abstract

A conjugate numerical methodology was employed to predict the metal temperature of a three-dimensional gas turbine vane at two different engine-realistic operating conditions. The vane was cooled internally by air flowing through ten round, radially-oriented channels. The conjugate heat transfer approach allows the simultaneous solution of the external flow, internal convection, and conduction within the metal vane, eliminating the need for multiple, decoupled solutions, which are time-consuming and inherently less accurate when combined. Boundary conditions were specified only for the inlet and exit of the vane passage and the coolant channels, while the solid and fluid zones were coupled by energy conservation at the interfaces, a condition that was maintained throughout the iterative solution process. Validation of the methodology was accomplished through the comparison of the predicted aerodynamic loading curves and the midspan temperature distribution on the vane external surface with data from a linear cascade experiment in the literature. The superblock, unstructured numerical grid consisted of nearly seven million finite-volumes to allow accurate resolution of flowfield features and temperature gradients within the metal. Two models for turbulence closure were used for comparison: the standard k-ε model and a realizable version of the k-ε model. The predictions with the realizable k-ε model exhibited the best agreement with the experimental data, with maximum differences in normalized temperature of less than ten percent in each case. The present study shows that the conjugate heat transfer simulation is a viable tool in gas turbine design, and it serves as a platform on which to base future work with more complex geometries and cooling schemes.