PREDICTION OF BOUNDARY-LAYER TRANSITION EFFECTS ON TURBINE AIRFOIL PROFILE LOSSES

摘要

A previous paper by these authors demonstrated the ability of CFD simulations to accurately resolve profile losses -- both with and without film cooling -- for a test case in which the airfoil boundary layers were turbulent over the entire airfoil surface. The same paper highlighted the inability of currently available methods to properly resolve losses for cases in which the airfoil boundary layer undergoes transition. This paper presents new CFD results for the identical test case of flow through a linear turbine airfoil cascade. This test case matches an experimental study documented in the open literature, and the measured data is used for validation of the computational results. The Reynolds-averaged Navier-Stokes simulations were performed using a new three-equation eddy-viscosity turbulence model previously developed and documented by the authors. The new model has been developed specifically to provide accurate resolution of boundary-layer transition, without any need for empirical correlations or problem-dependent user input. Results obtained with the new model on the uncooled airfoil show a significant improvement in loss prediction over currently available models that cannot resolve boundary-layer transition. Results for the film-cooled cases show improvement over more traditional models, but highlight the need to incorporate the physics of separated shear-layer transition in addition to attached boundary-layer transition.