Abstract
With the world coming to terms with the consequences of climate change, the aviation sector has continued pushing towards increased efficiency to lower emissions. Other than the use of eco-friendly fuels, it is a fact that to achieve higher efficiency and thrust, it is essential to raise the turbine entry temperature in the engine. Increased temperatures in the turbine section intensifies the thermo-mechanical stresses on the hot-end components reducing their life exponentially. Higher temperatures also lead to an increased fraction of heat transfer via the mode of radiation, which has been largely neglected in turbine design until recently. Hence, the heat transfer to the substrate needs to be minimized by reflecting or radiating the heat. The goal of this study has been to model the propagation of thermal radiation through a novel thermal barrier coating topcoat focused on reducing radiative heat transport to the super-alloy substrate. The radiation has been modeled with a finite-difference-time-domain approach to gather a broadband response across the target wavelength range. A range of topcoat morphologies were studied numerically, amounting to ≈ 8500 core hours, in search of an ideal structure that minimizes the radiation throughput to the substrate. The study found a strong angle dependency of reflectance with varying pore morphologies. The analysis done in this first of its kind study on the morphology dependence of reflectance in plasma-sprayed alumina coatings is expected to lay the foundation for future research, leading to a more accurate understanding of the mixed modes of heat transfer phenomenon in the turbine environment and higher turbine inlet temperatures.
