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高温高压主蒸汽管和导汽管弯头部位是锅炉管系中最薄弱环节,在电站运行中常发生破裂。本文内对管道弯头损坏原因作了分析,指出用持久强度来作为弯头断裂寿命衡量的不适用性,并用试验证明:在管道制造过程中由冷弯或热弯所引起的预损对弯头断裂寿命降低有明显影响,弯管后+正火和回火或单独回火,能改善抗蠕变裂纹开裂和扩展能力,但已不能恢复到未弯前的性能。 相似文献
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一、管道热伸长补偿概述为了防止供热管道因受热伸长而发生变形和减少(或消除)因受热伸长而产生的应力,采取了分段设置固定支座并在两个固定支座之间设置管道补偿器(也称伸缩器)的技术措施。补偿方式很多,除利用管道走向及坡度的改变而形成的L形、Z形管段对热伸长作自然补偿外,专门采用的补偿器有方形、套筒式、波形、球形补偿器四种。方形补偿器是过去应用最广泛的补偿器。其优点是:可以在施工现场弯制、制造方便。运行中无泄漏,不需要维护。可应用 相似文献
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本文利用ANSYS有限元分析软件,结合工程示范,对复杂应力状态下的高温集箱进行温度场和应力场的有限元分析计算,得出冷态启动、热态启动和甩负荷等危险工况下集箱热应力和内压应力的数值计算结果,并对热应力和内压应力进行了应力耦合,得到了集箱筒体三向主应力的实际分布状况和数值计算结果。本文研究成果为高温集箱安全状态评估和寿命预测提供了应力分析基础,为电站锅炉长周期运行安全保障关键技术及工程示范提供了强有力的技术支持。 相似文献
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为保证涡轮叶片的安全性,需要对叶片进行强度分析及寿命预测。以某定向结晶涡轮冷却叶片为例,首先采用三维流热固耦合方法获得叶片温度场分布,然后基于Hill屈服准则,对叶片进行热弹塑性应力应变分析,最后采用带平均应力修正的Morrow公式得到叶片低循环疲劳寿命,并基于计算结果,对局部区域进行结构优化结果表明:叶身与平台转接圆角吸力面前段(区域1)和吸力面尾缘段(区域2)温度高且应力大,将其作为考核点,两处区域低循环寿命分别为15 669和2 349。根据工程设计经验,对区域2提出了两种优化方案,其中大圆角设计(R=10)使该点等效应力降低9.9%,低循环疲劳寿命增加157.5%。 相似文献
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以传统的设计方法为基础,提出了大容量电站锅炉受热面管子的振动和强度可靠性设计方法以及寿命的评定方法。在振动可靠性设计方面,把卡门漩涡频率和声学驻波频率处理为随机变量,使用概率设计法确定锅炉尾部受热面振动设计的可靠度。在强度可靠性设计方面,把锅炉受热面管子的外径、壁厚、管内压力、材料强度等设计量根据实际处理为随机变量,使用可靠性分析技术确定锅炉受热面管子强度设计的可靠度。在寿命评定方面,对锅炉受热面管子的寿命数据进行统计分析,确定锅炉受热面管子的平均寿命。通过对锅炉受热面管子壁厚的监测和跟踪,确定锅炉受热面管子的剩余寿命。给出了水冷壁、过热器、再热器和省煤器管子强度可靠性设计的实例、管式空气预热器管束振动的可靠性设计实例和锅炉过热器管子寿命评定的实例。表1参9 相似文献
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超临界机组高温合金管氧化膜剥落问题是困扰机组安全与经济运行的难题,严重制约了机组蒸汽参数和效率的提高。特别是,在超临界机组采用给水加氧处理方式(OT)后,奥氏体不锈钢管内壁氧化膜大面积剥落事故屡见不鲜,尤以TP347H合金管为甚。本文总结了近年来国内外针对超临界机组合金管氧化膜研究的进展及相关成果,首先介绍了超临界蒸汽环境中合金管氧化机理和原子迁移机制,综述了铁素体和奥氏体合金表面氧化膜的形貌特征,分析了蒸汽溶氧对氧化膜生长速率、形貌和缺陷的影响。氧化膜完整性是决定合金抗腐蚀性能的重要因素,但在机组运行过程中氧化膜应力破坏了氧化膜完整性。进一步总结了国内外氧化膜应力和剥落研究的数值分析及实验研究情况,为我国超临界机组氧化膜剥落故障诊断研究提供参考。 相似文献
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电厂中由于锅炉的壁温及使用寿命监测手段比较落后,锅炉四管爆裂问题经常发生,尤其是锅炉过热器和再热器,而过热器和再热器超温爆管直接影响到机组的安全运行和经济性,因此电厂中对锅炉过热器再热器壁温和寿命损耗率的计算显得很重要。对苏制TII-82型锅炉过热器再热器的寿命损耗率的计算进行了研究,根据文中提出的锅炉过热器再热器寿命损耗率计算的模型,以某电厂的1号炉为例,最后计算出寿命损耗率=0.22141,为以后能够开发一套能准确计算锅炉过热器再热器壁温及寿命预测的在线监测与故障诊断系统提供了基础。 相似文献
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M. Manuela Prieto González F. Javier Fernández García Inés Suárez Ramón Hilario Sánchez Roces 《Energy》2006
The process conditions of power plant components subjected to high pressures and temperatures are essential to determine their remaining life, availability and efficiency. It is, therefore, expedient to pay special attention to critical components, such as superheater and reheater heat exchangers, headers, and main and reheated steam lines. In this paper, on-line and off-line variables of a power plant reheater that has presented problems of thickness losses and repetitive tube fissures are studied. The fissures are associated with the effect of a thermal–mechanical mechanism. Off-line measurements were taken of the following variables: pressure, temperature, velocity and composition of the gases. On-line instrumentation was completed by the installation of specific thermocouples to ascertain the temperatures in the tubes outlet. Various angles for the fuel inlet of the burners and variations in the number and location of the working burners were also assayed. As a consequence of this analysis, it can be deduced that there are important differences in the outlet temperature of the reheater tubes that decrease for lower powers. Finally, it is pointed that a non-uniform distribution of the steam flow in the reheater might be the cause of the problem. 相似文献
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ABSTRACTSuperheaters are high-temperature cross-flow heat exchangers. Steam flows inside the tubes, and the flue gas outside in a direction perpendicular to the axes of the tubes. However, they differ very substantially from the other heat exchangers operating at low temperatures. Superheaters are characterized by complex flow system and high tube walls temperature. Superheaters are among the most exposed to damaging pressure elements of steam boilers. Damage to the superheater causes about 40% of emergency shutdowns of boilers. The paper presents the boiler superheater model with distributed parameters, which is used to determine on-line the degree of superheater fouling by ash. 相似文献
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The general principles of mathematical modeling of heat transfer in cross-flow tube heat exchangers with complex flow arrangements that allow the simulation of multipass heat exchangers with many tube rows are presented. The finite-volume method is used to solve the system of differential equations for temperature of the both fluids and the tube wall with appropriate boundary conditions. A numerical model of a multipass steam superheater with 12 passes is presented. The convection and radiation heat transfer on the flue gas side are accounted for. In addition, the deposit layer is assumed to cover the outer surface of the tubes. Comparing the computed and measured steam temperature increase over the entire superheater allows for determining the thermal resistance of the deposits layer on the outer surface of the superheater. The developed modeling technique can especially be used for modeling tube heat exchangers when detailed information on the tube wall temperature distribution is needed. 相似文献
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K. Zarrabi R.A. Platfoot H. Zhang A. Sheth I. Rose 《International Journal of Pressure Vessels and Piping》1996,69(3):239-246
Boiler tubes in a fossil-fuelled power station are subjected to erosion and corrosion that caused the tubes to become locally thinned or scarred. To avoid unscheduled tube failures and hence prevent large financial loss due to boiler shut-down and tube repairs, it is important to estimate boiler tube lives. Boiler tube lives are very sensitive to tube temperature. This paper describes the development of a non-dimensional parameter termed T*. It is shown that T* can be used to estimate the tube temperature variation in the scarred tube section. Also a method has been described for volume estimation and characterisation of a tube scar. This is important for more accurate tube life assessments. 相似文献