Numerical Investigation of the Effect of Trailing Edge Thickness of Simulated CMC Blades on Loss Profiles

Abstract Ceramic Matrix Composite (CMC) is an enabling material allowing higher turbine inlet temperatures and possibly resulting in better thermal efficiency of gas turbine engines. This is because CMC layers with environmental barrier coating (EBC) have significantly higher thermal limits (∼1755K) compared with the more conventional alloyed metallic blades. CMCs possess a complex fabrication process resulting in different geometrical characteristics than metallic blades (e.g., larger trailing edge thickness, large leading-edge curvature, etc.). It is therefore desirable to assess the aerodynamic performance of the CMC blades using experimental and numerical simulations. To investigate, three different CMC blades with varying trailing edge thicknesses were numerically simulated. Both Large Eddy simulation (LES) with the dynamic subgrid closure as well a recently implemented Reynolds averaged Navier-Stokes (RANS) coupled with an intermittency function-based transition model were utilized. Two sets of experimental test points with different Reynolds numbers at a given high-free stream turbulence range (Tu=∼10-13%) were considered. The LES was previously validated by comparing with experimental data. The RANS transition model was validated against the experimental data of the Stripf's for a turbine blade. The predicted pressure loading profiles, total loss distributions, and integrated loss of the three different CMC blades were computed and comparisons against the experimental data are presented herein. The mixing and boundary layer loss was evaluated by both the RANS and LES and was found that the mixing loss forms a larger proportion of the overall loss as the trailing edge thickness increases.