Design and computational analysis of highly reflective multiple layered thermal barrier coating structure

Three related multiple layered thermal barrier coating (TBC) structures were designed and analyzed in this study. The designs were selected to theoretically assess the relative balance between conductive and radiative heat transport mechanisms in a TBC, and hence to provide guidance on how to optimize the physical and geometric design of a TBC. The primary design purpose was to achieve high reflectance to radiation within a wavelength range of 0.3 ∼ 6 μm, which is typical of a gas turbine combustion environment. These structures, with overall thickness of 250 μm, consist of several sets of highly reflective multiple layered stacks and a single layer ceramic material with low thermal conductivity. Within the multiple layered stacks, each stack was specifically designed to reflect a targeted range of wavelength. A broadband reflection within the required wavelength range was achieved by using 12 stacks each containing 12 individual layers. Computational analysis indicated that the substrate metal temperature could be further reduced by as much as 45 °C if a multiple layered coating was used in place of a monolayer of ceramic coating of the same thickness. The effect of scattering in the multiple layered thermal barrier coating system was also evaluated and is discussed in this study.