非泄漏固定声源干扰下的管网泄漏定位技术研究

实际管网泄漏检测环境中,管内外非泄漏固定噪声(如施工、管道阀门噪声等)叠加在管道泄漏声信号中,传感观测信号间的互相关函数中有多个相关峰值,若不能正确识别峰值来自泄漏还是非泄漏声源,将导致漏点定位错误。以两传感观测信号的自相关函数构建非泄漏和泄漏信号特征提取函数,通过特征提取函数识别出管道传播媒质对两类信号的衰减特征信息,该衰减特征结合互相关函数的相关峰值时延信息,识别出峰值来自泄漏还是非泄漏声源。实际定位应用表明,在管内外非泄漏固定噪声干扰下,漏点定位误差在1 m以内,突破了传统基于时延估计的泄漏定位技术及仪器需要在夜间,或人为关闭某些管道阀门、支路等安静环境下,通过回避干扰噪声才能进行定位的限制。     

基于盲系统辨识的供水管网泄漏定位系统研究

管道长度作为已知参量是传统时延估计泄漏定位方法应用的前提,针对实际应用中长度较难测量或不能获得的情况,采用盲系统辨识方法估计泄漏信号传播信道响应函数,并从中提取源信号从漏点传播到采集点的时间信息,从而不依赖管道长度定位漏点.盲辨识中,采用overlap-save和相关函数配准原理构建代价函数,解决高阶信道估计和信道间的病态问题;采用遗传算法对多目标函数进行全局最优化,避免梯度算法收敛陷入局部最小点.基于虚拟仪器技术构建了整个定位系统,实现信号采集、存储、处理及检测信息显示等功能.应用表明,系统解决了管道长度未知情况下的漏点定位问题.     

管道泄漏检测中的噪声自适应抑制

在供水管道泄漏检测中,干扰和环境噪声直接影响到泄漏检测的有效性和漏点定位的精度,因此有必要对检测信号进行噪声抑制,增强检测信号的信噪比,以保证可靠检测和准确定位.提出一种根据不同带宽信号与噪声自相关长度的差异,利用线性增强器和预测器分别自适应抑制检测信号中的窄带噪声和宽带噪声的方法.该方法不需要任何先验知识就可以自适应抑制与有用信号带宽不同的噪声,处理后数据的信噪比较处理前平均提高4 dB以上,对实际的泄漏检测信号处理后,使得定位误差平均减小0.3m以上,并且降低了误检率.     

采用EMD的管道泄漏声信号增强

在管道泄漏检测中,采集信号中的噪声会影响泄漏检测的准确性和泄漏定位误差。已有的管道泄漏去噪方法依赖经验参数的设置,去噪效果受管道条件和环境影响大。本文提出使用不依赖经验参数的EMD用于管道泄漏声信号增强。现有的EMD去噪方法需要知道有用信号或者噪声的特征,不适用于特征随管道工程条件及环境变化较大的泄漏信号的去噪增强。提出改进的EMD信号增强方法,该方法不需要知道泄漏信号和噪声特征就可以提取与泄漏信号相关的IMF。在改进的EMD信号增强方法的效果分析中,信噪比提高可达16 d B。在大量实际工程管道泄漏信号处理中,使用改进的EMD信号增强方法之后得到的时延峰值更明显,漏点定位精度更高。     

虚拟仪器在氧化锌避雷器泄漏电流在线检测中的应用

传统的仪器结构由于有限的数据处理能力，难以完成复杂的信号处理任务，从而使测量准确度难以进一步提高。这里采用虚拟仪器实现氧化锌避雷器泄漏电流的在线检测，不仅极大增强了仪器的智能化程度，同时为复杂、有效的信号处理手段的应用提供了广阔的空间。在信号处理方面，采用小波技术对现场信号进行消噪处理。对消噪后的信号，利用信号的相关分析推算出阴性基波泄漏电流。采用这样的分析方法，测量准确度得到显著提高，从而增强了设备故障诊断的可靠性。     

基于小波变换的管道泄漏声发射检测信号处理

针对管道泄漏声发射检测信号中含有大量噪声导致定位精度低这一实际,研究了基于小波变换的声发射检测信号降噪技术,利用小波函数阀值降噪法对泄漏系统所采集的信号进行滤波处理,以保证采集到的瞬态信号有效性,并采用互相关分析法对泄漏点定位.10种工况下实验结果表明,采用小波变换对声发射检测信号处理处理后,管道的定位精度在5％之内,满足工程实际需要.     

基于DSP和LabVIEW的飞机气密性检测系统

利用超声换能器阵列采集泄漏超声信号,采用TMS320f2812芯片作为仪器的信号处理芯片和LabVIEW图形化开发语言,研制了手持式检测仪和泄漏分析软件结合的气体泄漏检测系统.该检测系统检测精度较高,对气体泄漏可以实现实时检测与趋势预测,将该系统在某型军用飞机上进行实验验证,验证该仪器的检测精度.     

基于以太网的管线泄漏实验台技术改造

在分析了原有管线泄漏实验台存在的不足后,对其进行了技术改造.通过采集管线压力,流量等参数并综合运用多种数据处理方法来检测和定位泄漏点.基于OPC技术来实现远程监控.系统改造后取得了良好的效果.     

基于LabVIEW的管道泄漏检测SPRT算法实现研究

利用序贯概率比检验法检测油气管道泄漏是一种较新的方法。针对原始压力信号噪声的非高斯性,采用卡尔曼滤波器进行预处理,提高了序贯法判断泄漏的准确性。分析了传统压力梯度法的不足,借鉴负压波定位中的时间差法定位泄漏点,提高了定位的精度。并且本文结合LabVIEW平台开发了相应的卡尔曼滤波程序和SPRT算法程序。实验结果表明,本文设计的程序有效可靠,这种管道泄漏检测方法值得推广。     

泄漏管道波速预测理论及其应用

基于泄漏管道声振特性的互相关检测和定位方法,根据管道声振基本理论并结合管道泄漏的实际情况,提出了泄漏管道中波速预测理论,并对不同PVC塑料管道进行了泄漏检测和定位试验.试验结果表明,波速预测理论是正确可行的,且有效提高了互相关检测法的定位精度,将漏点定位的相对误差减小到5％以下.     

Adaptive noise cancellation based on EMD in water-supply pipeline leak detection

In water-supply pipeline leak detection and location, both the leak signals and blurred noises are closely related to the pipeline states and surroundings and most of the conventional noise-cancellation methods have to depend on the empirical parameters of either signals or noises. EMD (Empirical Mode Decomposition) is an adaptive signal decomposition method and is exclusive of base functions. A signal is decomposed into several IMFs (Intrinsic Mode Functions) in EMD, then the noise in a signal can be cancelled through removing uncorrelated IMFs. The existing EMD noise cancellation methods need to know the characteristics of either the wanted signal or the noise for rebuilding the noise-removed signal. However the characteristics of leak signals and noises are not fixed in various pipeline conditions, so the existing EMD noise cancellation methods can’t be directly applied in water-supply pipeline leak detection. This paper proposes an adaptive noise cancellation method based on EMD, in which the IMFs that don’t or less contain the components related to the leak can be removed through the cross-correlation between the IMFs and another signal collected at the either side of a suspect leak. In simulation analysis, the adaptive noise cancellation method can increase the SNRs (Signal to Noise Ratios) of leak signals as high as 16 dB. In processing practical pipeline vibro-acoustic signals, with the proposed method the peak of adaptive time delay estimate of leak signals, which determines the location of a leakage, becomes more distinguished, and thus the error of leakage location is improved.     

采用余弦调制滤波器组泄漏检信号处理研究

供水管道泄漏检测定位中,定位的不确定度由检测信号的信噪比决定,抑制噪声干扰,提高信噪比,是提高泄漏检测定位精度的关键。在充分分析泄漏信号特征的基础上,提出将改进的余弦调制滤波器组用于泄漏检测信号的噪声抑制。该方法利用分析滤波器组将信号分解为若干个带宽相同的子带信号,然后选择有效子带,再通过综合滤波器组将有效子带信号合成。该方法是一种不需要泄漏信号和噪声先验知识的自适应信号处理方法,能够有效抑制噪声,由于余弦调制滤波器分解的特性,即使泄漏信号处于不同频率段时,噪声抑制效果基本相同,处理后信噪比较处理前平均提高8 d B左右。实际工程应用验证表明,该方法去噪处理后的定位结果优于现有各种噪声抑制/信号增强方法的结果。     

Leak detection monitoring system of long distance oil pipeline based on dynamic pressure transmitter

A dynamic pressure transmitter (DPT) is designed in this paper for long distance oil and gas pipeline, of which the design principle and main performance indices are introduced. A novel leak detection monitoring system (LDMS) of long distance oil pipeline based on DPT is designed, and the detection principle and system composition are specified. Dynamic pressure signals along the pipeline can be obtained by the DPT, and then the pipeline leak can be detected by extracting the wavelet packet entropy (WPE) of the signals. The WPE signal feature extraction method for judgment of pipeline leak is explored and developed. In addition, the influence of the wavelet basis and calculating window width on the identification performance of the WPE are further discussed. The application examples show that the DPT has higher detection sensitivity and leak resolution than the traditional pressure transmitter. The system can identify the pipeline leak correctly and reduce false alarm rate effectively. It can also improve detection sensitivity and localization accuracy. The system can correctly detect leaks with a rate of 96.7% and the greatest localization error is 101 m.     

Leak rate metrology for the society and industry

Leak detection is a non-destructive test performed to verify materials and components in agreement with the prescribed specifications, by using techniques, which do not damage their characteristics or performances. The leak check of fluids dates back in time; it started to be applied at the end of the 19th century when the electron was discovered and early in 20th century when the first mass spectrometer was realized. Today, for environmental and personal safety more effective leak detection and location capabilities on various artifacts are necessary. Leak detection techniques are widely applied in many branches of industry. In the paper leak test requirements in general and the differences between the test methods are shortly reviewed. The choice of proper leak detection technique is related to the sensitivity and leak thresholds. Whatever method is chosen, a traceability chain must be guaranteed starting from the NMIs that have developed primary standards.     

直压式气体泄漏检测技术的研究

主要介绍了直压式气体泄漏检测方法的检测原理、泄漏率的计算与确定、直压式气体泄漏检测的过程与方法、影响检测精度的主要因素以及基于单片机的直压式气体泄漏检测仪的设计过程。     

管道传感器测漏方法综述

本文介绍了几种常用的管道测漏传感器检测方法的原理,并对各种方法的优缺点进行了比较。提出了一种管道机器人的发展方向——利用多传感器技术的管道外测漏机器人的设计。     

抗交串自适应噪声对消系统在管道相关检漏技术的应用

管道相关检漏技术通过对泄漏引发的振动信号的处理来完成检漏工作 ,系统原理和结构都非常简单。但在实际应用中 ,它有应用的局限性。在强噪声环境下 ,传感器接收到的包含独立噪声和公共噪声的信号 ,会导致相关曲线中出现虚假的峰值。为提高该类仪器的抗干扰性能 ,本文引入了一种新型的自适应滤波器结构——抗交串自适应噪声对消系统 (CTRANC)。在 Windows95平台上 ,我们编制了一个相关检漏软件 ,其中加入了 CTRANC模块。仿真的结果是令人满意的。     

Leak detection in pipe using transient flow and genetic algorithm

An inverse transient method with genetic algorithm (GA) was applied to leak detection in pipeline. Transient flow caused by valve operation was calculated using the characteristics method. The location and discharge of leak were determined so that the difference of the calculated pressure may be minimized from the reference pressure calculated under a given leak condition. Calculations were done for the leak at one and two locations in pipeline. Furthermore, the effect of noise in pressure data was discussed, and the leak locations and leak discharges can be predicted precisely even in the case of noisy data. This paper was presented at the 9^th Asian International Conference on Fluid Machinery (AICFM9), Jeju Korea, October 16–19, 2007.     

A complete procedure for leak detection and diagnosis in a complex heat exchanger using data-driven fuzzy models

In this paper, an efficient fuzzy model-based leak detection algorithm is designed for a pilot heat exchanger. A dynamic fuzzy model of the physical plant is first derived from input–output measurements using a fuzzy clustering technique. This model is run in parallel to the process for symptom generation. The leak detection mechanism has been tested and validated on the real co-current heat exchanger, and has proven to be efficient in detecting leaks of different magnitudes in the water circulation pipe.     

基于Lyapunov稳定性理论的气体管道泄漏检测技术研究

管道泄漏检测技术已经在长输气体管道安全运行中起到很重要的作用.本文讨论了基于李雅普诺夫稳定性理论的天然气管道泄漏检测技术,建立了气体管道泄漏动态模型,根据李雅普诺夫意义下对非线性系统的稳定性定义,通过对特征值的分析判断泄漏.实验仿真证明该方法具有一定的可行性.