Thermodynamics Analysis Of Coating System For Gas Turbine Blade

With the advantages of the high-efficiency,clean,and less pollution,gas turbine has become one of important directions of the development of electric power in China.Increasing the gas turbine inlet temperature will improve the heat engine cycle performance,and also will significantly increase the thermal efficiency of gas turbine and therefore reduce fuel consumption.However,higher temperature of the gas turbine inlet will lead to more severe service conditions of metal parts,especially for gas turbine blade.Hence it is important to analyze the mechanics of blade coating system under real working conditions.Based on thermal barrier coating materials and the accumulation of scientific research in nondestructive testing,a numerical simulation model of micro crack defects thermal barrier coating based on the nonlinear finite element method and fracture mechanics was established.By quantitative analysis of the peeling of coating failure,the relationship between the residual stress and crack extension was revealed;also,the nature of the plasma sprayed thermal barrier coating fall off was clarified.Therefore,the research on the development of new efficient multilayer structure composite materials and new nondestructive testing technology in the application of multi-layer material is of great theoretical and practical significance.This thsis includes the following aspect:Firstly,a two dimensional four layers of blade coating system model has been established.Four layers were built including substrate,bond coat(BC),thermally-grown oxide(TGO)and thermal barrier coating(TBC).The relationship between stress distribution and convective heat transfer coefficient.Secondly,the instantaneous thermal stress of the multilayer structure was achieved by the thermal-mechanical coupling finite element method.After comparing of the different micro models by discussing the different interface shape(amplitude and wavelength),the influence of each layer thickness was investigated.Thirdly,in order to solve the problem of the interface failure mechanism,ac cording to the model of interface failure which is built by nonlinear finite eleme nt,the different fracture parameters(J integral?energy release rate and stress inte nsity factor)about corresponding different crack lengths.was calculated.Moreover the probable directions about the extending of this kind of fracture was simulated.It revealed the influence of micro structure characteristics on macro mechanical p roperties.It provides theoretical basis for the design of thermal barrier coatings w hich has great significance of the research and development of coatings products.The research of this thesis analyses the process of damaging about interface of TBCs systematically.Moreover it provides the theoretical basis and the analysis method for the design of structure,the performance optimization and selection of suitable materials.