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首页> 外文期刊>Thermal engineering >An Analysis of the Effect of Protective Films on the Inside Surface of Headers and Steam Pipelines in Combined-Cycle Power Plants on Their Thermally Stressed State
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An Analysis of the Effect of Protective Films on the Inside Surface of Headers and Steam Pipelines in Combined-Cycle Power Plants on Their Thermally Stressed State

机译：联合循环电厂联管箱和蒸汽管道内表面热应力状态下保护膜的影响分析

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摘要

The outlet header of the high-pressure superheater is among the critical components affecting the service life of heat recovery steam generators (HRSG) of combined-cycle power plants (CCPP). Headers, heat-transfer tubes, and steam pipelines are protected against corrosion by running proper water chemistry to form thin protective films on the surfaces. These films formed on the inside surface of heat-transfer tubes protect against corrosion and also reduce thermal stresses in the tube walls during transients. They are formed on the inside of tube systems of HRSGs in CCPPs at temperatures above 230°С and with good deaeration. Results are presented of a numerical analysis of the influence of thin protective films on the state of thermal stresses in headers and steam pipelines of HRSGs used in CCPPs during various transients induced, for example, by startups from different initial thermal state or thermal shocks. Predictions were obtained for different film thicknesses assuming that the film thermal conductivity was less than thermal conductivity of the pipeline metal. The numerical results enabled the determination of the heating-up modes for headers and steam pipelines under which the effect of protective films is the greatest. It is demonstrated that the protective films have a considerable effect on stresses and damage accumulation in the pipeline wall induced basically by large temperature disturbances, such as thermal shocks. The effect of protective films on the thermally stressed state of unheated pipes was assessed by reducing the resourse consumption and accumulation of equivalent operating hours during transients. It is demonstrated that a 50 μm thick protective film alone can increase the service life of an HP steam superheater’s outlet header with a standard size of 426 × 34 mm by 6%.
机译：高压过热器的出口集管是影响联合循环发电厂（CCPP）的热回收蒸汽发生器（HRSG）使用寿命的关键组件之一。通过运行适当的水化学作用以在表面上形成薄保护膜，可以保护联管箱，传热管和蒸汽管道免受腐蚀。在传热管内表面上形成的这些膜可防止腐蚀，并在瞬态过程中减少管壁中的热应力。它们形成在CCPP中HRSG的管道系统内部，温度超过230°С，并且具有良好的脱气性。给出了对保护膜的数值分析结果的数值分析，该保护膜对CCPP中HRSG的集管和蒸汽管道中热应力状态的影响在各种瞬变期间（例如，由不同的初始热态或热冲击引起的启动）。假设膜的热导率小于管道金属的热导率，则可以得出不同膜厚的预测结果。数值结果可以确定集管和蒸汽管道的加热方式，在这些方式下保护膜的作用最大。已经证明，保护膜对基本上由诸如热冲击之类的大的温度扰动引起的应力和在管道壁中的损伤累积具有相当大的影响。通过减少瞬态过程中的资源消耗和等效工作时间的积累，可以评估保护膜对未加热管的热应力状态的影响。事实证明，仅50μm厚的保护膜就可以将标准尺寸为426×34 mm的HP蒸汽过热器出口集管的使用寿命延长6％。

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