基于声发射和小波分析的活塞环-缸套系统的摩擦润滑状态研究

利用声发射(AE)技术对摩擦润滑状态进行在线监测。采用小波多分辨率分析技术抑制由阀门开关和燃烧震荡引起的大幅值声发射AE信号,并采用阈值降噪的方法提取出由粘滞摩擦力引起的声发射信号。然后运用小波包络分析计算冲程中部的声发射信号幅值的平均值作为评价活塞环-缸套系统润滑状态的指标。试验结果显示:冲程中部的声发射信号能够有效地表征活塞环-缸套的摩擦润滑状态,并能够通过声发射指示标准区分不同类型的油品对系统润滑状态的影响。其中,声发射信号的幅值随着载荷的增大而小幅增大,且随着转速的增大而明显增大。研究结果充分证明了声发射监测技术在活塞环-缸套摩擦润滑状态在线监测的有效性。     

基于LabVIEW的声发射信号小波降噪方法研究

针对电厂汽轮机的滑动轴承碰摩故障,提出了一种有效的故障诊断方法.该方法首先采用声发射传感器来采集轴承的声发射信号,然后通过小波降噪的方法对所提取的信号进行去噪处理,再对处理后的声发射信号进行频谱分析,从而判断轴承的碰摩情况.通过在300MW汽轮机转子模拟试验台上实施碰摩试验并进行分析研究,结果表明：运用上述方法能够准确地预测汽轮机的转子碰摩故障,了解碰摩的严重程度,实现对汽轮机的在线监测,大大提高了机组安全性.     

声发射检测大型桥门式起重机的可行性分析与试验

起重机是工业生产中的重要设备，统计表明起重机事故约占我国全部工业企业伤害事故的20％左右，且近几年仍层出不穷，基于此，本丈对将声发射在线监测方法引入到大型桥门式起重机检测的可行性进行了分析并对一台起重机进行了在线检测．结果表明：声发射应用于大型桥门式起重机的检测是可行的，能有效识别存在的危险缺陷的信号；桥门式起重机两端部的圆弧过渡处角焊缝属于应力集中区，是声发射检测时的重点监测部位。     

火力发电厂阀门泄漏故障声发射检测系统研究

阀门是火力发电厂重要的辅助设备之一,针对目前火力发电厂无法实现阀门内部泄漏故障有效检测的问题,结合LabVIEW软件编程特点和阀门泄漏故障检测要求,开发设计了阀门泄漏故障声发射在线监测系统。该系统由硬件和软件两部分组成,硬件系统采用了工业便携式计算机设计方案,使整套检测系统携带方便、拆卸简单灵活;软件系统则针对阀门泄漏声发射信号特点,设置了特定的状态检测指标,可实现阀门泄漏率的定量诊断和分等级报警。本研究检测试验表明:阀门泄漏故障声发射在线监测系统可以迅速捕捉到阀门泄漏故障,并可实现阀门泄漏率的定量诊断。     

基于数字信号处理的锅炉"四管"漏泄监测系统

自适应数字滤波器可以很好地去噪,将漏泄信号从广谱噪声中准确地提取出来,为准确、及时、可靠地预报锅炉"四管"漏泄提供了有效的手段.介绍自适应数字滤波的结构和噪声对消算法,并通过实践检验了它的正确性和实用性,为减少漏泄事故扩大造成的损失,发挥了重要的作用.     

汽轮发电机组轴承运行状态声发射监测研究

通过分析汽轮发电机组径向轴承在过载或碰磨时表现出的声发射特性，提出了用声发射技术在线监测轴承过载及碰磨的方法。实践证明，该方法具有快速，准确性和早期发现故障的特点，非常适合于设备状态监故障预测。     

形态滤波在滑动轴承声发射信号降噪中的应用

针对滑动轴承状态监测时声发射信号的噪声干扰严重、突发性强和信号处理量大的特点,采用形态滤波对声发射信号进行降噪处理.对形态滤波器进行了优化设计,针对某310MW汽轮发电机组滑动轴承现场试验获得的声发射信号进行了实时形态滤波,在此基础上实时计算了4号滑动轴承升速过程中声发射信号的时域特征参数(均方根值VRMS、峰值Vc、峭度因子Fk),并与小波滤波法的计算值进行了对比.结果表明:经优选合适的结构元素设计的形态滤波器能更好地滤除滑动轴承声发射信号的噪声、保留原始信号特征,滤波效果优于小波滤波方法;经形态滤波后的实时特征参数能快速准确地诊断滑动轴承润滑故障,在滑动轴承声发射状态监测中具有很好的工程应用价值.     

H-ADCP回波强度分析算法研究与应用

平原河道普遍存在行船、淤积等问题，对换能器发射的声束产生遮挡，从而导致测流精度受到影响。因此，在对太湖流域47个水平声学多普勒流速剖面仪(H-ADCP)在线测流站点声束遮挡情况分析的基础上，提出了一套H-ADCP回波强度分析算法，实现对H-ADCP在线自动测流的状态监测，自动剔除遮挡测次、发现断面淤积等声束遮挡问题，以辅助测站运行维护工作开展，保障在线测流数据有效性。     

常压金属储罐底板声发射检测及应用

阐述储罐的现状、储罐停机常规检测方法、声发射在线检测方法。结合实际工程检测过程中的实例,通过声发射在线检测综合分析储罐底板腐蚀,通过处理分析所采集数据,对无效数据进行处理,采用参数滤波、时差滤波、双层传感器布置,通过滤除环境噪声、机械噪音的干扰。根据标准对有效数据进行综合评级,对储罐进行监测,给予厂家维修建议,降低用户检测成本,对储罐的安全状态进行重点管理。     

发动机漏泄在线智能检测技术及其设备的研究

介绍了发动机漏泄在线检测的原理和发动机在线智能检测设备的组成、控制系统的软、硬件设计及抗干扰设计，并就漏泄检测技术进行了探讨。     

The use of acoustic emission methods as aids to the structural integrity assessment of nuclear power plants

Since it is an integral method permitting continuous monitoring and remote defect location, acoustic emission offers promising benefits for the nuclear industry. Particular potential applications relating to the integrity of the primary pressure boundary of nuclear reactors that are considered in this report are the detection of flaws during pre-service and requalification hydrotests, and continuous monitoring for crack growth and leakage.The correlations between fracture mechanics and acoustic emission are discussed on the basis of certain fundamentals of material emission behaviour. The influence of instrumentation and of aspects related to wave propagation on the detectability and evaluation of acoustic emission signals is considered.The conclusion reached is that at the present time acoustic emission can be used predominantly during hydrotests as a search method for cracks. Although some degree of characterization and sizing of defects may be obtained on the basis of empirical data, a quantitative evaluation of defect severity based on fracture mechanics cannot yet be made satisfactorily. It is expected that a considerable improvement in this respect may be achieved by applying a transfer correction that takes into account the depth position and directivity pattern of the source.The technique of leak detection by acoustic emission shows promising results permitting the location and quantification of leaks. Practical experience and future research work are expected to enhance the accuracy and detection sensitivity.     

大型火电站高压加热器可靠性增长模型验证及预测

文中提出了大型火电站高压加热器可靠性增长模型,详细讨论了该模型的参数估计和拟合检验。根据电力可靠性管理中心统计数据,说明了该模型完全符合被统计的高压加热器可靠性增长变化趋势。分析结果也说明了通过改正,产品设计和制造中的缺陷,提高运行人员的素质和操作水平,改善设施及运行状况,产品的可靠性将得到逐步提高。     

Monitoring crack growth in pressure vessel steels by the acoustic emission technique and the method of potential difference

The work was performed on pressure vessel steels and has shown that the correlation between acoustic emission (AE) techniques, the method of potential difference and microfractographic observation reveals the different stages of the crack propagation. Based on these correlations, it may be possible to predict the remaining service life of a vessel from the results of short-term acoustic emission monitoring of crack propagation.     

电厂阀门内漏在线监测研究

减少阀门内漏量是电厂重要的节能减耗手段.对阀门内漏在线监测及其经济性分析研究,采用基于传热学原理的方法计算阀门内漏量,等效焓降法计算内漏量对于机组经济性影响.对某一电厂300 MW机组阀门的内漏量进行监测,结果表明:该系统能定量计算阀门内漏量和对电厂煤耗的影响,具有非接触、在线、实时测量等优势,可以为电厂运行人员提供阀门检修、检漏的依据和参考.     

Time-dependent leak behavior of flawed Alloy 600 tube specimens at constant pressure

Leak rate testing has been performed using Alloy 600 tube specimens with throughwall flaws. Some specimens have shown time-dependent leak behavior at constant pressure conditions. Fractographic characterization was performed to identify the time-dependent crack growth mechanism. The fracture surface of the specimens showed the typical features of ductile fracture, as well as the distinct crystallographic facets, typical of fatigue crack growth at low ΔK level. Structural vibration appears to have been caused by the oscillation of pressure, induced by a high-pressure pump used in a test facility, and by the water jet/tube structure interaction. Analyses of the leak behaviors and crack growth indicated that both the high-pressure pump and the water jet could significantly contribute to fatigue crack growth. To determine whether the fatigue crack growth during the leak testing can occur solely by the water jet effect, leak rate tests at constant pressure without the high-pressure pump need to be performed.     

提高热电厂效率的几项措施

从热经济性角度提出提高热电厂效率的几项技术和措施:通过凝汽器补充软化水,将外供蒸汽过热度降低;使用喷射式混合加热器回收热力除氧器排汽,作为生水加热器;利用压力匹配器代替减压减温器;用两相流加热器代替面式高压加热器等。     

热水器污垢实时监测及其节能潜力估算

热水器的实测结果表明了热水器的污垢不可忽视.水质和垢样分析结果则指出了垢的成因,为了消除垢的不良影响,建立了热水器污垢(热阻)实时监测模型用以监测污垢的积聚状态,并进而据以估算热水器污垢对策的潜在节能价值.     

基于模式识别的燃气管网泄漏检测技术

管道泄漏检测是确保燃气管道安全运行的重要技术手段,然而由于城市燃气管网是错综复杂的环状管网,目前尚没有一种方法能较好的对城市管网进行安全监控和泄漏检测。模式识别技术是燃气管网泄漏检测技术发展的方向,针对环状管网应用模式识别技术中存在特征向量维度大的问题,提出了管网分区检测的思想,并阐述了其在管网泄漏检测中的具体步骤。最后通过一实例验证了模式识别法用于城市环状燃气管网泄漏检测的可行性。     

A computational fluid dynamics evaluation of unconfined hydrogen explosions in high pressure applications

Over the last few decades, the demand for hydrogen has significantly grown. Its high-energy content and relatively small environmental effect make it an ideal energy source and chemical feedstock. However, the perceived high risk of hydrogen in the eyes of society is a key challenge that has to be addressed before any future widespread utilization of hydrogen can be achieved. In this study, the consequences of unconfined hydrogen releases are evaluated using a computational fluid dynamics simulation software, FLACS, to determine the potential to explode. In addition, the study includes the analysis of parameters that can promote hydrogen vapor cloud explosion, e.g., initial pressure, time to ignition, and leak height position.The results conclude that high-pressure hydrogen has the potential to build up a large vapor cloud and may explode even without confinement when the leak source is close to the ground. The highest overpressure produced in the simulation was 0.71 barg, which resulted from igniting a hydrogen gas cloud from a 207 bar hydrogen source leaking at 1 m height. The high overpressure suggests that hazard studies for hydrogen leaks near the ground should not assume a free flow jet release. This study also gives a recommended distance from a high-pressure hydrogen processing unit to nearby occupied buildings to use in conjunction with industrial spacing tables for fire hazards.