【作者】 郑凯；

【导师】 蔡桂喜； 张博；

【作者基本信息】 中国科学技术大学 ， 材料加工工程， 2021， 硕士

【摘要】 火力发电作为我国工业与居民用电的主要供应方式,一直以来备受关注。随着我国环境形势恶化以及不可再生资源的日益枯竭,火力发电站机组向着更高效率、更低能耗的方向发展,超临界和超超临界发电机组已经成为我国火力发电的主力军。但是,高效的同时带来的高温高压使得锅炉过热器与再热器管道的高温氧化问题日益严重,由此引发的氧化皮堵塞爆管事故也日渐突出。为了维护锅炉正常运行,研究可用于锅炉管氧化皮堵塞问题的检测方法至关重要。文献调研结果显示,针对锅炉管常用的弱磁性奥氏体耐热钢材料,已有磁性检测法、涡流检测法等无损检测方法被报道,而对于T91等铁磁性耐热钢管中的氧化皮堵塞检测尚未见报道。本文为解决铁磁性锅炉管道内氧化皮堵塞检测难题,提出一种名为磁力扰动法的无损检测新方法,主要研究工作如下:(1)应用有限元仿真软件,计算了磁力扰动法的轴向和径向磁轭在T91管道中形成的磁场以及管内氧化皮的受力情况,并根据计算结果画出了氧化皮吸引区域。仿真结果表明,磁力扰动法轴向与径向磁轭产生的磁感应线在管壁内相互排挤,使得管内空气中形成了可吸引氧化皮运动的倾斜磁场;从而阐明了通过改变交叉磁场使氧化皮运动即可进行氧化皮堵塞检测的原理;(2)搭建了氧化皮吸引区域测定以及声发射检测的实验平台。氧化皮吸引区域测定实验验证了磁感应强度以及磁感应线分布仿真结果的正确性;声发射实验结果分析表明,以幅值绝对值为权重的加权平均时间可以作为氧化皮堵塞面积定量检测的依据,证明了磁力扰动法的可行性;(3)分析了影响磁力扰动法测量结果的因素。随着径向磁轭电流的增加,测量结果呈现先增大后趋于稳定的趋势;而轴向磁轭与径向磁轭相对位置的改变,会使磁力扰动法氧化皮吸引区域的大小发生变化。其分析结论可用于指导磁力扰动法检测装置的设计和检测。磁力扰动法的提出,为铁磁性锅炉管道内氧化皮堵塞难题的解决提供了新思路。更多还原

【Abstract】 As the main industrial and residential electricity supply method in China,thermal power generation has always attracted public attention.With the deterioration of our country’s environmental situation and the increasing depletion of non-renewable resources,thermal power generation units are developing towards higher efficiency and lower energy consumption.Supercritical and ultra-supercritical generating units have become the main force in our country’s thermal power generation.However,with higher efficiency,higher temperature and pressure have made the problem of high temperature oxidation of boiler superheater and reheater pipes become more and more serious,and the tube burst accidents because of the blockage of oxide scales have become increasingly prominent.In order to maintain the normal operation of the boiler,it is important to study a method that can be used to detect the blockage of oxide scales.The literature survey results show that for the austenitic heat-resistant steel materials commonly used in boiler tubes,non-destructive testing methods such as magnetic inspection methods and eddy current testing methods have been reported.However,there are few studies on the detection of ferromagnetic heat-resistant steels such as T91.In order to solve the problem of detecting the blockage of oxide scales in ferromagnetic boiler pipes,this paper proposed a new non-destructive testing method called magnetic-disturbing method.The main research work was as follows:(1)The finite element simulation software was used to calculate the magnetic field formed in the T91 tube by the orthogonal magnetic yoke and the force of the oxide scales in the tube under the action of the magnetic-disturbing method,and draw the oxide scales attraction area on the basis of the calculation results.The simulation results show that the magnetic induction lines generated by the orthogonal magnetic yoke of the magnetic-disturbing method squeeze each other in the tube wall,so that an oblique magnetic field that can attract oxide scales is formed in the air in the tube.The division of oxide scales attraction area further clarifies the cause of the movement of oxide scales;(2)The experimental platform of measurement of oxide scales attraction area and acoustic emission was built.The experiment of measuring the attraction area of the oxide scales verifies the correctness of the magnetic induction intensity and the distribution of magnetic induction lines obtained by the simulation calculation;acoustic emission experiment results show that the weighted average time weighted by the absolute value of the amplitude can be used for quantitative detection of the ratio of oxide scales blockage area,which proves the feasibility of the magnetic-disturbing method;(3)Some factors that could affect the measurement results of the magnetic-disturbing method were analyzed.With the increase of the current of radial yoke,the measurement results show a trend of increasing first and then becoming stable;the change of the relative position of the axial yoke and the radial yoke will change the size of the oxide scales attraction area.The magnetic-disturbing method has two highlights:one is to visually demonstrate the interaction of the magnetic field between the orthogonal yokes in the ferromagnetic tube through simulation calculation,and the other is to provide new ideas for solving the problem of oxide scales blockage detection in ferromagnetic boiler tubes.更多还原