Conjugate Heat Transfer Effects on a Realistic Film-Cooled Turbine Vane

Abstract

A conjugate heat transfer solver has been developed and applied to a realistic film-cooled turbine vane for a variety of blade materials. The solver used for the fluid convection part of the problem is the Glenn-HT general multiblock heat transfer code. The solid conduction module is based on the Boundary Element Method (BEM), and is coupled directly to the flow solver. A chief advantage of the BEM method is that no volumetric grid is required inside the solid — only the surface grid is needed. Since a surface grid is readily available from the fluid side of the problem, no additional gridding is required. This eliminates one of the most time consuming elements of the computation for complex geometries. Two conjugate solution examples are presented — a high thermal conductivity Inconel nickel-based alloy vane case and a low thermal conductivity silicon nitride ceramic vane case. The solutions from the conjugate analyses are compared with an adiabatic wall convection solution. It is found that the conjugate heat transfer cases generally have a lower outer wall temperature due to thermal conduction from the outer wall to the plenum. However, some locations of increased temperature are seen in the higher thermal conductivity Inconel vane case. This is a result of the fact that film cooling is a two-temperature problem, which causes the direction of heat flux at the wall to change over the outer surface. Three-dimensional heat conduction in the solid allows for conduction heat transfer along the vane wall in addition to conduction from outer to inner wall. These effects indicate that the conjugate heat transfer in a complicated geometry such as a film-cooled vane is not governed by simple one-dimensional conduction from the vane surface to the plenum surface, especially when the effects of coolant injection are included.