Numerical Study Of The Thermal Insulation And Thermal Shock Performance Of 8YSZ Thermal Barrier Coatings

Natural gas power generation systems with gas turbine as the core engine can effectively solve the energy and environment problems generated in the process of economic and social development in China, meanwhile the ships and aircraft with gas turbine as the core power equipment play an important role in promoting the development of defense aviation industry. The thermal barrier coatings(TBCs) applied to gas turbine can effectively protect the hot parts of gas turbine, it has contribution to increasing the inlet temperature of gas turbine, can improve its cycle thermal efficiency and prolong its service life, thus TBCs will has important value in enhancing the comprehensive performance of gas turbine. With further development towards the direction of high inlet temperature of gas turbine, TBCs of good performance have become an important component part in the research and development of gas turbine.Thermal insulation performance and service life are two key assessment criteria of the TBCs, and because of that thermal shock performance of TBCs has a huge impact on its service life, so this paper has conducted an intensive research of the thermal insulation and thermal shock performance of TBCs. Simplified physical models have been established to study of the heat transfer process and thermal insulation performance of the coating. Firstly, the coating models had different inner microstructure were constructed by a numerical method. Secondly, the software for analyzing thermal insulation performance was developed based on the finite difference method. Based on this software, the impact of the pore thickness, size, direction and the different inner microstructure of the coating on its equivalent thermal conductivity has been calculated. The results showed that: the elongated pores of layered structure coating can significantly reduce its equivalent thermal conductivity, and its thermal insulation performance will be enhanced, but the elongated pores have the opposite effect to columnar structure coating; the rules of equivalent thermal conductivity of different structure coatings varies with pore size were also different, but as the pore size decreasing, the regional equivalent thermal conductivity and stable temperature field distribution inside of coatings will be more uniform and the structure will be more stable; as the horizontal angle of pores increasing, the equivalent thermal conductivity of the coating exhibits a sinusoidal variation.Meanwhile, based on a typical double layer structure model, this paper has used ANSYS to simulate the thermal stress distribution inside the coating when thermal shock occurred, then analyzed the mechanics mechanism of thermal shock fatigue damage of the coating. Also this paper has studied the change of thermal stress inside the coating with the substrate material and ceramic layer thickness changed. It can provide some suggestions to reduce the thermal shock stress inside the coating and improve its thermal shock performance.