Abstract
The aim of this paper is to numerically investigate cooling performances of a non-film-cooled turbine vane coated with a thermal barrier coating (TBC) at two turbulence intensities (Tu = 8.3% and 16.6%). Computational fluid dynamics (CFD) with conjugate heat transfer (CHT) analysis is used to predict the surface heat transfer coefficient, overall and TBC effectiveness, as well as internal and average temperatures under a condition of a NASA report provided by Hylton et al. [NASA CR-168015]. The following interesting phenomena are observed: (1) At each Tu, the TBC slightly dampens the heat transfer coefficient in general, and results in the quantitative increment of overall cooling effectiveness about 16–20%, but about 8% at the trailing edge (TE). (2) The protective ability of the TBC increases with Tu in many regions, that is, the leading edge (LE) and its neighborhoods on the suction side (SS), as well as the region from the LE to the front of the TE on the pressure side (PS), because the TBC causes the lower enhancement of the heat transfer coefficient in general at the higher Tu. (3) Considering the internal and average temperatures of the vane coated with two different TBCs, although the vane with the lower thermal conductivity protects more effectively, its role in the TE region reduces more significantly. (4) For both TBCs, the increment of Tu has a relatively small effect on the reduction of the average temperature of the vane.
Highlights
The performance of a gas turbine engine is evaluated by two thermomechanical quantities, that is, thermal efficiency and output power
These phenomena suggest that the thermal barrier coating (TBC) is effective in protecting the metal surface, the role of the TBC in the trailing edge (TE) is small because the TTBC is a little lower than T in such regions
This phenomenon may be explained by the fact that the TE is the smallest and thinnest part of the vane, so it is coated with the smallest amount of TBC
Summary
The performance of a gas turbine engine is evaluated by two thermomechanical quantities, that is, thermal efficiency and output power. Several factors may influence the protective ability of TBC, that is, thermal conductivity, thickness, porosity, phase stability, surface roughness of the TBC, temperature of the hot gas, matching of thermal expansion coefficients with the metal surface coated with TBC, and coating method. Maikell et al [2] experimentally investigated the TBC effect on overall effectiveness of a leading-edge model based on cylindrical geometry. Boyle [3] studied the effects of TBC on improving the thermal efficiency of an engine; he concluded that TBC had an impact on vane sensitivity to the external heat transfer coefficient. Boyle and Senyitko [4] indicated that the presence of TBC added the skin roughness, which was a physical factor of TBC, and had significant results on the heat transfer rate on the turbine vane surface
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