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超超临界汽轮机汽缸的多轴蠕变分析与高温强度设计对机组安全高效运行至关重要。对于在超超临界参数下中压内缸,它的主要破坏来自于高温和复杂应力共同作用下的蠕变损伤。随着蒸汽参数(温度T,压力P)的不断提升,原汽缸承受的蠕变损伤越发严重,因此有必要进行局部结构改进。应用基于受约束孔洞长大机制的Cocks-Ashby多轴蠕变模型对新老汽缸进行了对比分析,并采用了有限元计算方法得到了汽缸多轴蠕变等效应变的分布。结果表明:基于孔洞长大蠕变理论能较好地预测汽缸危险点的多轴蠕变;新汽缸比老汽缸在抗蠕变性能方面有一定改善。
Multi-axial creep analysis and high temperature strength design of the ultra-supercritical steam turbine cylinder are very important to the safe and efficient operation of the unit. For the medium-pressure cylinder under ultra-supercritical parameters, its main failure comes from the creep damage caused by the combination of high temperature and complex stress. With the continuous improvement of the steam parameters (temperature T, pressure P), the creep damage suffered by the original cylinder is more and more serious, so it is necessary to make partial structural improvements. The Cocks-Ashby multi-axis creep model based on constrained hole growth mechanism was used to analyze the new and old cylinders. The distribution of multiaxial creep equivalent strain was obtained by the finite element method. The results show that the multi-axial creep of the dangerous point of the cylinder can be predicted well based on the creep theory of the hole growth. The new cylinder has a certain improvement in creep resistance compared with the old cylinder.