【作者】 梁木子；

【导师】 程先华；

【作者基本信息】 上海交通大学 ， 机械设计及理论， 2007， 硕士

【摘要】 发电站蒸汽管道的支管连接部位以及与之相连接的支管接管座处出现的热疲劳裂纹,严重影响了发电机组的安全运行。本论文进行模拟实验并有限元方法,获得蒸汽管道支管及接管座管壁温度场和热应力的分布规律,阐明热疲劳裂纹产生的原因;从优化管道结构、改进管道布置和调整运行方式等角度提出防止热疲劳裂纹产生的措施,提高管道的安全性、可靠性,具有巨大的经济价值。根据电站实际工况建立小型实验台,测得接管座处管壁温度随蒸汽温度和流量变化的趋势,以此确定管壁温度产生波动的原因以及管内冷凝水回流的区域,测出应力集中区域。依据传热学理论,确定了一种适合于工程实际应用的边界条件,运用具有强大工程计算能力的通用编译平台Matlab,进行工程计算编程,实现了电站蒸汽管道换热系数的算法。编程的计算结果与传统的拟合法经验公式的计算结果一致,验证了工程编程算法正确性,同时,工程编程算法较传统算法具有简便、快速的优点。采用有限元分析程序工具ANSYS模拟实验平台管道的温度场分布状况,所获得的结果与实测相吻合。依据ANSYS的研究结果,建立了电站蒸汽管道的有限元计算模型,结合在电站实测的相关初始数据进行计算求解,求解出电站机组启动阶段和并网使用阶段的蒸汽管道管壁的温度场、温度梯度和热应力的分布状况,预测出电站在启动后6小时时,蒸汽管主管与支管交界的接管座处将短时出现243MPa最大热应力值,超过管材12Cr1MoV的许用应力159.6MPa,并接近于材料的屈服极限值254.8MPa。蒸汽管的接管座处长期出现这一现象,导致蒸汽管壁材料产生蠕变,萌生出热裂纹。更多还原

【Abstract】 The steam pipe and correlative branch pipe of power plant are detected to appear thermal diffuse crack, which influence the normal run of the generator severely. To study the reason of appearance of the thermal diffuse crack, Temperature and thermal stress analysis of the steam pipe and correlative branch pipe was performed with finite element analysis method.The distribution of Temperature and thermal stress field were confirmed and a proposal was tabled which applied for prevent the appearance of thermal diffuse crack.A test platform was designed and built according to the structure parameters of steam pipe in power plant. Flow controller, temperature controller and pressure regulator were used for regulating the operating mode. Onsite pipes’temperature was measured by thermocouples and plotted into variation graphs. From analysis of these graphs some preliminary conclusions and basis were determined for computation in the next steps.Study the heat transfer theory and water&steam’s portfolio formula, and then a computational method of boundary condition parameters which is suitable for engineering application was determined. This algorithm, which is powerful in engineering calculation, was realized. The result of programming calculation and experience formula calculation was compared, verified the accuracy of the programming calculation, and confirmed the boundary condition parameters which will be used in Finite Element Analysis.Temperature field of the steam pipe and correlative branch pipe were analyzed in test and the result was compared with test data, the reliability of calculation was verified. The finite element model of the steam pipe in power plant was built, and the solution with the data measured in power plant was verified in ANSYS. The No.120, 180, 240, 300, 360, 420, 480 minutes’pipes’temperature field, thermal gradient field and thermal tress field were calculated. The reason of thermal cracks, the stress concentration region and the time and location of the maximum tress were determined which is useful for life prediction.The average life expectancy formula of 12Cr1MoV was gained by derivation calculating which based on rupture strength formula of metal material. The forecast result更多还原