热障涂层隔热机理分析及有效性判据

Thermal insulation mechanism analysis and effectiveness criterion of thermal barrier coating

建立了一维对流-导热模型,经理论推导、分析验证得到了热障涂层隔热有效性判据:当涂层热阻大于无涂层时高温燃气侧换热热阻时,涂层总能使叶片金属基体外表面温度降低,起到隔热效果;反之,则喷涂热障涂层(TBC)后外部燃气侧表面传热系数存在临界值,只有该表面传热系数小于临界值,热障涂层才能起到隔热效果,否则涂层起不到隔热效果,甚至会恶化叶片换热。热障涂层自身温降与有无涂层前后叶片金属基体外表面温降成比例关系,建立了以叶片金属基体外表面温度为基础的新的涂层隔热效果评价机制。

A one-dimensional convection-thermal conductivity model was established, and the thermal insulation effectiveness criterion of the thermal barrier coating was obtained through theoretical deduction and analysis. When the thermal resistance of the coating was greater than the heat transfer resistance of the high-temperature gas side without coating, the coating could generate a positive thermal insulation effect. On the contrary, the heat transfer coefficient for the external gas side after spraying the thermal barrier coating(TBC) had a maximum critical value. At this time, only when the external gas side heat transfer coefficient was smaller than this critical value after the TBC was sprayed, the TBC could have a thermal insulation effect, otherwise the thermal barrier coating couldn’t work, even worsen the heat transfer of the blades. The temperature-drop of the TBC itself was proportional to the temperature-drop of the outer surface of metal blade with or without TBC. And a new evaluation standard of the thermal insulation effect of the coating based on the outer surface temperature of the blade metal substrate was proposed.