Thermal analysis of thermal barrier coating systems under transient and time harmonic thermal loads

Abstract

In this study, the temperature fields in a thermal barrier coating system (TBC) under various types of thermal loadings, including steady and transient thermal loads, is investigated. TBCs are exposed to a variety of harsh thermal loadings, including thermal shock and periodic thermal loads. Therefore, the need to achieve the temperature distribution in different positions of the TBCs, especially in the protective coating is very crucial. Non-uniform Thermal boundary conditions are considered for both external temperature and heat flux distributions. The coating and substrate are not stationary at the onset of transient thermal load. Using the solution of steady-state problem as initial condition, the transient temperature fields within the coating-substrate system is obtained. The dual-phase lag (DPL) heat conduction is utilized to scrutinize the transient response of the TBC system. Fourier and Laplace integral transforms have been used to solve the temperature field equations. The effect of concentrated thermal shock and steady harmonic thermal load on the temperature fields of coating and substrate is investigated. The results demonstrate that the steady state and transient temperature fields strongly depend on the type of thermal load, the thickness and thermal properties of the coating, and the loading parameters. The results indicate that the effect of concentrated thermal shock is felt after at least 8.33 s at distance 1.2 cm far from the top surface of ceramic coating. The effect of concentrated thermal shock is eminent adjacent to point (x=0,y=0) of the free boundary of coating, but after a longitudinal distance of 2 cm drastically reduced. The ceramic coating is able to relieve the amplitude of temperature oscillations up to 1280C at a vertical distance of 3mm from the free boundary of coating.