燃气轮机起动过程热障涂层的应力数值分析

Numerical Analysis of Thermal Stress on Thermal Barrier Coatings in Start-up Stage for Gas Turbines

考虑了热障涂层在服役过程中发生的陶瓷层烧结和氧化层增厚作用,对燃气轮机起动过程中涂层热应力进行了数值研究。通过瞬态传热模拟获得起动过程温度场,运用顺序热应力耦合求解起动过程热应力。其中起动初始的陶瓷层烧结和氧化层增厚状态,通过预先模拟高温烧结和氧化层增厚过程来获得,并通过ABAQUS子程序分别实现。结果表明,起动过程中涂层瞬态温度场的变化主要受燃气温度的变化规律所影响。起动过程未见热应力激增现象,陶瓷层烧结和氧化层增厚主要对起动初期,尤其是起动过程的初始残余应力有重要影响,对起动过程中后期的影响可忽略。烧结对陶瓷层和粘结层的热应力均有较大影响,而氧化层增厚对陶瓷层热应力的影响很小,但其对粘结层热应力的影响比烧结更大。

The thermal stress of thermal barrier coatings （TBCs） in the start-up stage of gas turbines was studied, considering the sintering of ceramic and the thickening of thermally growth oxidation （TGO）. The temperature field of the coatings was obtained by a transient heat transfer modeling. Thermal stresses were then solved by sequential thermal stress coupling. The states of TBC resulted from ceramic sintering and TGO growing were achieved by modeling the processes of sintering and TGO growing with ABAQUS subroutine, respectively. These states were then used as the initiations of the start-up process. The heat transfer results show that the transient temperature field of the coatings is mainly dominated by the change of hot gas temperature. The thermal stress result shows that there is no steep growing of thermal stresses in the start-up stage. Thermal stresses of TBCs were affected by ceramic sintering and TGO growing mainly in the early of the start-up, especially at the initiations of the start-up process. However, there were neglectable effects on thermal stresses after a half of start-up time. Additionally, the thermal stress of ceramic and bonding coatings can both be affected by sintering, However, the thermal stress of BC can be affected more significantly than that in the ceramic layer resulted by TGO growing.