| Thermal barrier coatings(TBCs)have been widely utilized as a thermal insulator in the gas flow fluid of engines because of its low conductivity,thereby increasing the operating temperature of turbine blade and improving the thermal efficiency of the engines.The thermal mismatch stress has been identified as the key factor of failure of TBCs,which is inevitable due to the huge differences in the physical,thermal and mechanical properties developed in TBCs.The operating temperature is increasing because of the application of gas film cooling holes.However,the high thermal stress generates around the gas film cooling holes and result in the spallation of TBCs.This is a severe limitation in the application of TBCs.Therefore,it is essential to study the stress variation around the gas film cooling holes as a matter of urgency.In this paper,the finite model of TBCs with gas film cooling holes will be presented to investigate both the distribution of thermal stress and its variation around gas film cooling holes,which based on the fluid-structure interaction.The main contents in this thesis are listed as follows:Firstly,the calculation model for solid and fluid of TBCs with gas film cooling holes are established in this thesis.The mesh of the turbine blade,the setting of step,boundary,loading and material parameters are introduced detailed.Fluid field is calculated using the finite volume method solution of fluid dynamic equations,while,the turbine blade solution solid thermal stress equation using finite element method.The joint simulation of fluid domain and solid domain are calculated through a third party software MPCCI.Secondly,the result of the temperature field and stress field,which consider single cooling of thermal barrier coating turbine blade near film cooling holes is discussed detailed in this part.Fluid-structure interaction simulation to calculate the single cooling of thermal barrier coating turbine blade near film cooling holes is the steady temperature field in high temperature.The results indicated that thermal barrier coating have good heat-insulating capability,heat insulation reached an average of100 k or so.The thermal insulations of TBCs located on pressure side and suction side is superior to the TBCs located on leading edge and trailing edge.Cooling gas film covering area due to the effect of the gas film cooling and thermal barrier coating is one of the best heat insulation effect.And the cooling effect of cooling gas film occupy a leading role in the thermal insulation coating compared with other area is not obvious.What is more,the thermal barrier coating residual stress after cooling toroom temperature is calculated based on the conjugate temperature field.The results show that the right coating surface of the gas film holes is the danger area which appears spalling damage due to the level of residual stress.While,at the interface between the coatings at the left with holes is the area where has the highest probably to appear interface crack due to the residual stress out-plane.Thirdly,the contrastive analysis of the temperature field and stress field of turbine blade with and without single film cooling holes is discussed detailed in this part.For excluding cooling blade model of the gas film hole,the thermal insulations of TBCs located on leading edge and trailing edge and exposed to a higher temperature is superior to low pressure side and suction side exposed to a relative lower temperature.Thermal stress of ceramic coating is higher than the bond coating.The thermal stress in the ceramic coating and bond coating attain its maximum at the leading edge and trailing edge on both sides of the blade root a maximum.Thermal barrier coating spalling failure occurred in these locations.However,the peeling off easily occur in the beginning in the ceramic layer/oxide layer interface.For the blade model of the gas film cooling hole,the thermal insulations of TBCs located on the pressure side and suction side is superior to that at the leading edge and trailing edge.The thermal stress of ceramic coating is high than that of the bond coating.But stress concentration appears in the area around gas film hole.Thermal stress in the ceramic coating and bond coating reach it's the maximum near the gas film hole,so the thermal barrier coating spalling failure is easy to appear near the film hole.In summary,this study realize the finite element simulation of actual thermal barrier coating turbine blade with gas film cooling hole high temperature steady temperature field and residual stress based on the fluid-structure interaction analysis method.The effect of cooling holes on the temperature field and stress field of the thermal barrier coating are analyzed.These can provide a guidance to the failure prediction of TBCs coated on actual blade. |
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