【作者】 高倩霞；

【导师】 李录平；

【作者基本信息】 长沙理工大学 ， 动力机械及工程， 2011， 硕士

【摘要】 阀门是电站系统中不可缺少的流体控制设备,电站重要阀门泄漏故障将大大降低火力发电机组的效率,甚至直接威胁工作人员和机组的运行安全性。目前,电站阀门内部泄漏故障的常用检测方法都具有一定的局限性,难以及时准确地诊断到阀门工作故障。因此,开展电站阀门的在线状态监测和泄漏故障定量诊断研究具有重要意义和广泛的应用前景。本文采用理论和实验研究相结合的方法,对基于声发射技术的阀门泄漏故障检测方法进行了研究分析,并开发出阀门泄漏故障检测系统。首先,在前人研究的基础上,探讨了阀门内部泄漏故障产生声发射信号机理、泄漏声发射信号特征及泄漏声发射信号检测方法,找到了一种新的基于声发射信号特征——RMS值的阀门泄漏率计算方法,为阀门泄漏故障的定量诊断奠定了重要的理论依据。然后,设计搭建了阀门内部泄漏故障模拟实验台以及泄漏声发射信号检测系统;通过实验方法研究了不同泄漏工况下,阀门泄漏状态与泄漏声发射信号特征之间的定量关系。利用广义最小二乘法对实验数据进行分析处理,得到泄漏声发射信号的振铃计数、能量、幅值、RMS值和中心频率随阀门类型、阀门尺寸、阀前压力和漏孔尺寸的变化规律,找到了表征阀门泄漏状态的最佳声发射信号特征参数——振铃计数、能量及RMS值,建立了基于声发射信号特征的阀门泄漏故障诊断规则;同时,研究阀门泄漏率和泄漏声发射信号特征——RMS值之间定量关系,获得了实验室中三个被检测阀门的泄漏率计算公式,从而将阀门泄漏故障定量诊断理论实用化。最后,本文在理论和实验研究的基础上,基于LabVIEW软件平台开发出了一套阀门泄漏故障检测系统。该系统依据阀门泄漏声发射信号特点设置了特定的特征检测指标,具有自适应滤波功能,可实现泄漏率的定量诊断和分级报警。实验室及火力发电厂的现场验证及应用表明:所开发出的阀门泄漏故障检测系统的定量检测性能是良好的,检测精度(误差≤±16%)及反应灵敏度高。与PCI-2声发射检测系统相比,本文所开发的阀门泄漏检测系统具有操作简单方便、监测结果显示直观形象、针对性强的优点。更多还原

【Abstract】 Valve is a sort of indispensable equipment used for controlling fluid flow in power plant. The efficiency of thermal power units would be greatly reduced, or even there is a direct threat to the safety operation of staff and units, as soon as an important valve leaks. At present, all the leakage detection methods of power plant valve have certain limitations in on-time and accurate diagnose of valve operation fault. And thus, there is an important significance and broad application prospect to research the real-time quantitative detection and diagnosis of the power plant’s valve leakage fault.The detection method of valve leakage fault based on acoustic emission technology is mainly studied by combining theoretical analysis and experimental research in this paper, and then a type detection system of valve leakage fault is designed and developed.First, the mechanism, characteristics, and detection method of acoustic emission signals generated from valve leakage are discussed on the basis of previous studies. And a new calculation method of the valve leakage rate based on the features of acoustic emission signals is obtained, which provides the important theoretical foundation for quantitative diagnosis of valve leakage faults.Secondly, a simulation experiment platform of valve leakage fault and a detection system used to detect acoustic emission signals generated from valve leakage are set-up, and then the quantitative relationship between acoustic emission characteristic parameters and internal valve leakage rate is studied under different operating conditions with experiment method. The change of AE parameters, counts, RMS, energy, amplitude and dominant frequent component, with the variation of valve sizes, valve types, inlet pressure levels and size of leak, are obtained after the experimental data analysis and process based on Generalized Least squares method. Thus, the best AE parameters, counts, RMS and energy, which can characterize the internal fluid leakage through valve are found and the rules for valve leakage failure diagnosis based on acoustic emission detection are built. Simultaneously, the quantitative relationship between valve leakage rate and the characteristics of acoustic emission signal, RMS, is researched, and the calculation formulas of valve leakage rate of the three types of valve tested in lab are obtained, which put the quantitative diagnostic theory of valve leakage fault into practice.Finally, in this thesis, on the base of theoretical and experiment research, a type detection system of valve leakage fault is designed and developed using LabVIEW as developing platform. The specific testing index of AE characteristics are set up in the system according to the acoustic emission signal trait of valve leakage fault, with which the noise can be filtered out adaptively and the quantitative diagnosis of valve leakage rate and grades alarm are realized. It is proved that the quantitative detection performance of the detection system of valve leakage fault is quite well, with sensitive reaction and less than±16% detection error, by applying the system in lab and power plants. Compared to the PCI-2 AE testing system, the system developed by author of this thesis is more simple, visual and targeted.更多还原