Numerical Study Of The Heat Insulation Performance Of The YSZ Thermal Barrier Coatings

Energy issues have become top discussion of our country to maintainthe sustainable development of the economic and social. The power systemwith gas turbine as the core engine has the characters of high efficiency,clean, low emissions; it has shown great advantages of solving the energyand environment problem. Thermal barrier coatings (TBCs) have showngreat value in thermal protection of the high temperature region of the gasturbine, it can help to increase the inlet temperature of the turbine which isbeneficial for improving the cycle efficiency and the output power,decreasing the gas consumption of unit power, prolonging its service lifeand is of great importance in improving the comprehensive performance ofthe turbine. TBCs have shown application value in maintaining the turbineworking safely, efficiently, reliably; it can help to improve the energytransfer efficiency of the gas turbine and optimize the current energystructure of our country, it’s necessary to have further study of it. Theequivalent thermal conductivity of TBCs is highly related with two factors:the internal porosity and the inner structure of the coating, this paper willconduct an intensive research of the above focuses.We have established a simplified physical model to have an in-depthstudy of the thermal insulation ability and the heat transfer process of thecoating. Firstly, the coating models had different inner structure wereconstructed with a numerical method. Secondly, the thermal latticeBoltzmann method and the finite difference method were used to programthe simulation software. We verified the effectiveness of the software bycomparing the simulation results with theory solutions of a simplified case. The influence of the porosity, the pore diameter and the different innerstructure to the effective thermal conductivity of the coatings werecalculated by our software. The results also show: the influence of the porediameter to the thermal conductivity is not obvious; the inner micro-structures make a great difference to the thermal conductivity; the effectivethermal conductivity of the coatings decreases with the increase of theporosity obviously. The layered coatings with low porosity show excellentthermal insulation ability. This paper also analyzes the influence ofdifferent factors in the heat transfer process to the specified insulationtemperature.We also established a heat transfer research model which was based onthe real scanning electron microscopy picture of the coatings, the heattransfer in the different structure was studied. The coatings were producedby the APS technology while the inner structure is the uniform one, andthey were sintered at high temperature of1150℃for different time. Bywriting a program which was used to simulate the temperature field ofthose models, we can easily get the changing relationship of thermalconductivity with the sintered time. These studies provide a new way tohave the numerical research of effective thermal conductivity of the TBCs,it also provide reference for the optimization of the coatings structure.