Influence of Ceramic Matrix Composite Weave Topology on Turbine Vane Heat Transfer and Aerodynamic Losses

The adoption of ceramic matrix composite (CMC) materials in gas turbines is gradually becoming more commonplace as designers seek to improve cycle efficiencies. The increased allowable temperature enables higher efficiencies through higher firing temperatures and reduced cooling requirements. While these advantages make CMCs an appealing option, the surface morphology of the material can provoke negative impacts on turbine heat transfer and aerodynamic losses. This study investigates the effect of a CMC weave pattern on the surface heat transfer augmentation and aerodynamic losses of a first stage turbine vane in a low speed, large-scale linear cascade over a range of Reynolds numbers. Infrared measurements are used to assess surface heat transfer, while downstream wake pressure measurements are used to quantify aerodynamic losses. Results from the CMC vane are compared with that of a smooth vane to determine the impact of the CMC weave topology on turbine vane heat transfer and aerodynamic losses. The effects on boundary layer behavior were found to be similar to that of random rough surfaces. Across all Reynolds numbers tested, the CMC surface introduced laminar to turbulent transition on the suction side which was absent in the smooth vane. As the Reynolds number increased, the transition spot moved closer to the stagnation point, resulting in greater augmentations of surface Nusselt numbers compared to that of the smooth surface. Due to a thicker boundary layer, laminar-turbulent transition, and increased mixing in the boundary layer, an increase of up to 100% in distance weighted average of wake loss was observed.