Effect of Blowing Ratio on CMAS Penetration Behavior and Thermal Insu-lation Performance of Thermal Barrier Coating-Air Film Cooling System
Aiming at the challenges posed by CaO-MgO-SiO2-Al2O3(CMAS)penetration,which leaded to thermal insulation performance degradation in thermal barrier coatings(TBCs)within air film cooling systems,this study explored the behavior of non-uniform CMAS penetration under various blowing ratios and its impact on thermal insu-lation performance.Utilizing Fluent for simulation,a conjugate heat transfer model was developed.This model,which accounted for heat conduction,convection and radiation(with radiation modeled using a discrete longitudinal radiation approach),enabled the analysis of temperature distribution across the TBC-air film cooling system at blow-ing ratios of 1.5,1.0,and 0.5.Furthermore,a three-dimensional phase field model(PFM)was constructed within ABAQUS to simulate the non-uniform CMAS penetration behaviors.This model facilitated an in-depth examination of how CMAS penetration affected the temperature distribution of the TBC-air film cooling system at different blow-ing ratios.The temperature distribution in the TBCs-air film cooling system after 300 h-penetration was compared.The study meticulously analyzed the effects of non-uniform CMAS penetration on the thermal insulation performance of TBCs across the in-thickness path of four positions:near the main stream inlet,at the leading and trailing edges of the cooling hole,and at the mainstream outlet.This quantitative analysis was conducted across different blowing ra-tios.Findings showed that the TBC-air film cooling system had a three-dimensional temperature gradient under opera-tional conditions.Notably,there were high temperature gradients both along the main flow direction and through the thickness of the TBCs,alongside a high degree of inhomogeneity in temperature distribution near the cooling holes.The CMAS concentration distribution within the top coating(TC)layer was found to be significantly uneven,with penetration rates increasing in higher-temperature regions.A decrease in blowing ratio was observed to increase the temperature of the TC layer while simultaneously decreasing temperature inhomogeneity,leading to an increase in the degree of CMAS penetration and a reduction in its inhomogeneity.CMAS penetration resulted in a degradation in the thermal insulation performance of TBCs.Specifically,at blowing ratios of 1.5,1.0,and 0.5,the greatest deg-radation in thermal insulation performance occurred near the mainstream inlet,with declines of 16.47%,17.13%,and 17.55%,respectively.The effect of CMAS penetration on the thermal insulation performance at the trailing edge of the cooling hole outlet was minimal,with the thermal resistance of TBCs showing little change under the influence of CMAS penetration.
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