Experimental simulations of effects of surface roughness level of TBC on overall effectiveness of film cooling under typical vane environment.

Pu, Jian; Zhang, Tiao; Shuai, Xu; Wang, Jian-hua; Chen, Yun; Wu, Wei-long

The principle of selection of surface roughness level of thermal barrier coatings (TBCs) at turbine film-cooled vanes is unclear. In this work, the universal turbine vane flow environment was characterized by the proper combinations of different wall curvatures and streamwise pressure gradients. To achieve the direct measurements of overall effectiveness, a conjugate film cooling model with simulated TBCs was established by matching the hot-side Biot numbers of actual materials. The surface roughness levels were set in a range for TBC design stage. The measurements displayed the detailed trends in overall effectiveness of metal and TBC with the surface roughness level, wall curvature, streamwise pressure gradient, and cooling air flowrate. The roughness effect on overall effectiveness was complicated by the wall curvature, due to generating different jet mechanisms. When the engine Ra changes from 0.2 to 14 μm, the variations of metal overall effectiveness can be controlled below 15% at different walls. Overall, to improve the protection ability to metal, the smoother TBC is suggested to spray at the flat wall, while, at the convex and concave walls, the proper roughness of TBC can be considered in the near-hole region under the acceptable stress level.

SURFACE roughness; THERMAL barrier coatings; METAL coating; METALLIC surfaces

Journal of Thermal Analysis & Calorimetry, 2023, Vol 148, Issue 19, p10251

1388-6150

Academic Journal

10.1007/s10973-023-12409-5