Small Amplitude Sharp Pressure Waves to Diagnose Pipe Systems

In this paper the possibility of using transient tests, generated by the Portable Pressure Wave Maker (PPWM) device, as a powerful tool in the management of pipe systems, is demonstrated. Specifically, tests carried out in different experimental set-ups at the Water Engineering Laboratory of the University of Perugia, Italy show that small amplitude sharp pressure waves produced by the PPWM allow to locate and evaluate the entity of anomalies, such as leaks, illegal branches, partial blockages, and negligently partially closed in-line valves. To improve the precision of localization of anomalies, arrival times of pressure waves are detected by means of wavelet analysis. Simple relations based on the water hammer theory are proposed to evaluate the entity of the anomalies.     

淮水北调临涣工业园输水工程空气阀的合理配置

淮水北调临涣输水管道工程线路长,线路平坦,考虑充水要求,设计在153个位置安装复合式空气阀,同时希望利用这些空气阀防止瞬变液柱分离。本文通过对1个典型水泵事故断电瞬变工况的数字仿真,研究空气阀参数的影响,包括不同微量排气孔径、高速进排气孔径及高速排气容许压差等。研究表明适当减小空气阀高速进排气孔径对于控制邻近线段的瞬态最小水压是有利的,并且通过大量计算研究,给出全系统空气阀的合理配置。     

Impedance Method for Abnormality Detection of a Branched Pipeline System

In this paper, an integrated detection scheme is developed to simultaneously address a leakage, a partial blockage and unknown branched pipeline elements. Expressions for the pressure head and discharge for a branched pipeline system having both a leakage and a blockage are derived in frequency domain. Boundary conditions for a reservoir and a branched dead-end allow the development of impedance formulations. The condition for a pipeline junction can be addressed using either a common condition for the pressure head combined with a continuity condition of discharge or a connectivity condition for impedance. In order to consider the unsteady friction’s impact, the impedance development process studied both the impact resulting from velocity profiles with two-dimensional distributions and the impact resulting from local and convective accelerations. Impedance expressions are derived for two distinct branched pipeline systems at different abnormality conditions. Based on drived formulations describing these systems, response functions were derived in the frequency domain and their corresponding time domain representations were integrated into a meta-heuristic calibration scheme for inverse transient analysis. Using an objective function for minimization of root-mean-square-errors between the observed and computed pressures, the calibration based one impulse response can simultaneously predict locations and magnitudes of abnormalities as well as parameters for a branched pipeline. The strength of the impedance-based approach for inverse transient analysis arises mainly from its feasibility to address different conservation conditions for pressure and discharge and for combining these conditions into a unified impedance connectivity condition.     

Adaptive Metaheuristic Scheme for Generalized Multiple Abnormality Detection in a Reservoir Pipeline Valve System

This paper presents mathematical and algorithmic developments related to general abnormality (multiple leakages and multiple partial blockages) detection in a simple pipeline system. Formulations for leakages and blockages were combined and reformulated to address general abnormalities efficiently in the frequency domain. Unsteady friction effects on laminar and turbulent flow conditions were considered during formulation development using 2D frequency-dependent and 1D acceleration-based models, respectively. The developed formula was tested in terms of model parsimony, computational accuracy, and flexibility for superposition in abnormality representation. Based on the proposed formulation, a novel multiple abnormality detection algorithm, called the adaptive metaheuristic scheme (AMS), was developed by integrating a stepwise genetic algorithm. The application of the developed method to a hypothetical pipeline system demonstrated the potential of the AMS for predicting general features of abnormality, even without access to prior information regarding the number and distribution of abnormalities. The developed method demonstrated robustness for the prediction of abnormality distributions and reliability, even in noise-contaminated signals. The adaptive predictability of the AMS can be characterized by not only its robustness for unknown multiple abnormality features but also its self-diagnostic capabilities during the calibration procedure.

     

Valve Maneuver Prediction in Simple and Complicated Pipeline Systems

The pressure and flow variations in pipeline systems are extremely sensitive to dynamic operations of the valves. Valve control and propagation of pressure waves along pipelines and their interactions with different pipeline elements introduce pressure transients in pipeline systems. The time series of the pressure head at any designated position depends on boundary conditions such as valve maneuver as well as geometrical and material characteristics of the pipeline system. An innovative method is proposed to calibrate the valve trajectory using pressure head records. The impedance method and particle swarm optimization were integrated with decomposition of convolution between the pressure response function and time series of the valve maneuver. To validate the applicability of this study, the developed method was tested in three hypothetical pipeline systems: a simple reservoir pipeline valve, multiple reservoir pipeline valves, and a complicated pipe network. Decomposition of the transfer function in the time domain and its convolution contributed toward improving the efficiency of the developed method. The successful calibrations of valve actions demonstrate the potential of the proposed scheme as an alternative to conventional flow meters for high-resolution flow rate evaluation.

     

南水北调北京段输水系统水力瞬变的控制

根据北京段输水系统工程布置的特点，研究了事故断电条件下水力瞬变引起的液柱分离现象及其防止措施。提出了求解空气阀瞬变过程的新模型。计算研究表明，可以采用沿线布置空气阀和单向调压井防止瞬变液柱分离破坏。通过对沿管线间隔500-1000m布置空气阀的水力瞬变计算研究发现，过大或者过小的空气阀孔径都是不利的，存在一个抑制液柱分离冲击压力或者高度真空的最优的空气阀孔径。对采用单向调压井防止液柱分离的研究表明，南水北调北京段沿线需要布置5座，并提出了合理的设置位置和经济参数。     

南水北调北京段输水系统水力瞬变的控制

根据北京段输水系统工程布置的特点,研究了事故断电条件下水力瞬变引起的液柱分离现象及其防止措施,提出了求解空气阀瞬变过程的新模型.研究表明,可以沿线布置空气阀和单向调压井防止瞬变液柱分离破坏.对沿管线间隔500 m～1 000 m布置空气阀的水力瞬变计算研究发现,过大或者过小的空气阀孔径都是不利的,存在一个抑制液柱分离冲击压力或者高度真空的最优的空气阀孔径.对采用单向调压井防止液柱分离的研究表明,沿线需要布置5座,并提出了合理的设置位置和经济参数.     

上游并联双调压室水电站瞬变流特性分析

由于长引水式水电站受地质地形条件、工程施工条件和系统运行稳定性等因素限制,为保证其安全运行,设置并联双调压室。通过建立调压室上游侧各支路阀门瞬变流水力特性的分析模型,以及考虑并联调压室水力特性的稳定性分析模型,深入分析了系统特殊的爆管瞬变流过程和水力振动特性。结果表明:在对应不同的爆管口直径同一爆管点位置,蝶阀至调压室之间管段最大瞬时流量为额定流量的1.14~2.21倍。随着爆管口直径的加大,不同特征管段的最大瞬时流量增大。考虑同一爆管口直径对应不同的爆管点位置,蝶阀至调压室之间管段最大瞬时流量为额定流量的1.25~1.67倍。随着爆管点和调压室距离增大,不同特征管段的最大瞬时流量增大。在任一支路爆管等不利情况下,通过相应支路阀门的控制可以降低复杂的瞬变流过程对另一正常运行支路的影响。研究所得水力—机械系统特征值分析成果对揭示引水系统水力振动特性具有参考价值。     

长距离有压输水工程泵站水锤的数值分析

综合考虑了长距离有压输水系统中的泵、泵后阀门、空气阀、调压井、异性串联管、下游水库等各种内、外边界条件,采用特征-差分方法,针对实际工程的泵站水锤问题,通过数值方法对事故停泵后重新启泵的时间间隔、输水系统管线糙率等要素进行了敏感性分析。结果表明,合理的启泵时间间隔有助于改善有压输水系统及其部件在水力过渡过程中的水动力特性,并缩减调压井尺寸及相应工程造价;管线糙率对水头损失和水锤波衰减存在影响,对全系统在水力过渡过程中的水动力特性影响较小。     

空气阀水力瞬变数学模型

空气阀是输水管道系统常用的防止水击破坏的智能化安全设备。针对目前空气阀水力瞬变数学模型假设气温T为常数及忽略空气阀高度影响的问题,首先基于等熵流动的气动力学理论,提出了新的空气阀进排气基本方程,然后,把空气阀、配套检修阀和连接管用一个具有自动进排气功能的调压室等效,提出了新的空气阀水力瞬变数学模型及其求解算法。与现有空气阀水力瞬变数学模型相比,在不考虑空气阀高度的条件下,新模型计算的最大水压更大,而负压也更低,这意味着以现有模型计算结果作为设计依据存在安全风险。考虑空气阀高度后,计算的输水管最大水压减小,但是负压也更加严重,因为等效调压室内水体对进排气有阻止延缓作用。此外,以空气阀气体为绝热流动所得计算结果作为设计依据是合理的,偏于安全的,因为在这种情况下计算的最大水压较大而最小水压较小。     

泵站管路系统水力过渡过程及二次防护措施研究

为选择合适的停泵水锤二次防护措施,针对泵站管路系统的特点,运用水锤特征方程组,确定了管道瞬变流的求解方法;同时,采用Bentley Haestad Hammer软件,对重庆市松既长江提水工程子项目——金子山高位水池至上游水库提水工程的水力暂态过程进行了模拟,并对停泵水锤、被动型后保护与主动型水击预防模式引起的管道内水压变化情况进行了计算。计算结果表明:(1)在3种工况条件下,水压的峰值分别为252.80,191.80 m及174.01 m,升压比分别为1.50,1.44及1.05;(2)水泵停机时间分别为3.74,3.77 s及4.60 s,水泵均未出现反转情况;(3)被动型后保护瞬态最高水头曲线呈弓形,而主动型水击预防瞬态的最高水头曲线接近正常水头线;(4)3种工况下的阀门出口处压力波动范围分别为71.4~254.8,70.7~181.0 m及46.0~174.0 m,而且主动型的水击预防模式水泵出口的波动最为缓和。主动型水击预防可以最大幅度地降低水锤的升压峰值,是更完善的二次防护措施。     

安装有空气阀的输水管路系统空管充水过程瞬态分析

在输水管路系统中,空气阀在预防水柱分离及再弥合水锤方面发挥着关键作用。现有空气阀的应用研究多集中于满管流状态,但对于空管充水阶段空气阀的水锤防护研究较少。为此,本文建立了空管充水过程中空气阀的数学模型,提出了一种基于改进牛顿迭代法和直接求解法相结合的求解空气阀模型的计算方法,分析了进气阀、普通进排气阀和进气微排阀3种类型的空气阀在曲折管线空管充水过程中的水锤防护效果。定量分析表明,为预防空管充水过程中出现的水柱分离及再弥合高压水锤,选择大口径进气,微量排气的空气阀最为合适。该研究对安装有空气阀的输水管路系统的空管充水瞬态分析具有一定的参考价值。     

Local head loss monitoring using acoustic instrumentation in partially full sewer pipes

After an increase in capital investment in UK sewers to reduce hydraulic capacity problems, the proportion of sewer flooding incidents now linked to blockages has increased. It is clear that if sewer operators are to continue to reduce flooding incidents, then better blockage management is now required. Sewer blockage formation is poorly understood; blockages are intermittent and occur in a number of circumstances. This paper reports on the development of low-cost acoustic instrumentation that can identify the location of a pipe blockage and then estimate the local head loss as a result of the presence of a blockage. A set of experiments were carried out in two full-scale laboratory pipes. The pipes' condition was altered by inserting blockages of different sizes. Acoustic data were recorded and presented in terms of the acoustic energy reflected from the partially blocked pipe. The results of this study show that the total reflected acoustic energy correlates with the measured head loss. A new empirical relation between the reflected acoustic energy and head loss due to a blockage is derived. This knowledge can then be used to estimate the reduction in flow capacity resulting from a blockage based on a single remote measurement.     

北京市南水北调供水环路水力过渡过程分析研究

北京市南水北调环线工程是一项规模宏大、结构复杂、涉及面广的系统工程，工程运行工况复杂。基于管道瞬变流的特征线解法，研究输水系统水力过渡过程特性对南水北调供水环路水锤防护的影响，以及系统运行的安全问题，为工程设计及调度运行管理提供科学依据。     

空气阀口径和型式对压力管线水锤防护的影响

通过ＫＹＰｉｐｅ２０１０水锤分析软件,对空气阀口径和型式的变化进行了分析研究。结果表明:变化剧烈的凸点驼峰位置组合式空气阀的口径调整对整个管线的压力影响非常大,随着空气阀的孔径减小（ＤＮ２００变为ＤＮ１００）,进气量会随之减小,且最大瞬变正压随之减小,但在高点驼峰处的负压有所增大,减小负压的效果一般;在同等口径下（ＤＮ２００）,将组合式空气阀调整为三阶段缓闭型防水锤空气阀,全线的最大瞬时正压水头大幅度降低,水锤防护效果大幅度改进,且全线最小瞬变压力水头为０ｍ,消除了负压;不同空气阀型式消除负压的作用是不同的。     

娘子关供水工程压力管路安全运行方式研究

本文分析计算了山西省阳泉市娘子关二期供水工程运行过程中突然停泵时的水力过渡过程,发现管道存在超过规范要求的负压,针对二级站压力管路的负压问题提出四种改善措施:降低管线高程,增加蝶阀,改善机组转动惯量,增加进排气阀。通过VB编程建立水锤计算模型,分别对四种措施进行比较分析模拟计算,并结合工程实际提出满足规范要求的合理防护方案,以期实现娘子关二级站的安全运行。     

乌鲁木齐市大西沟管道引水工程水锤防护设计

为了解决乌鲁木齐市大西沟引水工程因管线长、落差大而发生水锤破坏的问题,通过不同防护设备性能比较,结合水力瞬变计算和水锤方案比选最后得到合理的水锤防护方案。结果表明,通过在管线上布置空气阀、三级缓排空气阀、集气罐、超压泄压阀(安全阀)及管道末端调流消能阀关闭时间的控制,可有效地保证管道运行安全。     

空气阀排气性能分析

空气阀已成为长距离输水系统中必不可少的设备,担负着管道充水排气,事故、正常停机进气及排气,水锤防护等多项任务.其选型合理与否对工程安全运行影响较大.为此,分析了空气阀排气性能实测资料与公式计算结果的差异,由于空气阀的排气面积与流量系数的乘积不是常量,因此提出在进行压力输水系统水力过渡过程分析时应采用空气阀的实测资料.     

管道泄漏检测的水力瞬变全频域数学模型

输水管道泄漏孔的存在及其位置直接影响着系统压力波形的畸变和衰减特性,通过分析有、无泄漏时任意位置处的压头频域特性可使泄漏检测成为可能.在考虑非恒定摩阻影响的基础上,提出基于水力瞬变全频域数学模型的泄漏检测反问题分析方法.用拉氏频域变换处理边界条件和实测数据,并将遗传算法用于频域反问题模型的求解,在寻优速度上比传统的瞬变时域分析的方法有了较大的改善.算例表明基于水力瞬变全频域数学模型分析的管道泄漏检测是一种有效的新方法.     

长输水管道充水的气液两相流数值模拟

基于缓慢充水过程中管道内气液两相流的流态及其特性,在一系列合理假定的基础上,推导建立了描述充水过程的气液两相流控制方程,给出模型的求解方法和计算流程。采用南水北调工程北京西四环暗涵充水试验数据对模型进行验证,结果表明,数值模型可用于模拟"V"形复杂管道系统缓慢充水过程中管内水流和通气孔气流的两相变化过程。研究成果对长距离输水工程中通气孔、排气阀等调压设施的设计、选型,及后期管道的安全运行、维护管理等具有重要意义。