Robust optimization of valve management to improve water quality in WDNs under demand uncertainty

ABSTRACT

Water quality deterioration in water distribution networks can be associated with high water residence time in the network. To this end, some previous studies have proposed optimization procedures for valve management. However, these studies generally come up with operational configurations assuming deterministic user demand patterns that may never occur in reality. In consequence, the proposed solutions may not be effective for improving water quality or do not comply with pressure constraints if different demand patterns are observed. This study proposes a methodology to determine robust configurations of the valves to keep water residence time at acceptable levels regardless of the variability in demand patterns. The methodology is tested on four different distribution systems of varying topology and size. Results show the importance of executing robust – instead of deterministic, optimization to find valve configurations that guarantee the performance of the networks in terms of hydraulics and water quality.     

Testing behavior and effects of PRVs and RTC valves during hydrant activation scenarios

This paper provides an insight into behavior and effects of pressure reducing valves (PRVs) and of valves controlled in real time (RTC) during hydrant activation scenarios, which determine high-flow conditions in water distribution networks (WDNs). The analysis is carried out through the pressure-driven unsteady flow modeling of an Italian WDN, in which a pressure control device is assumed to be installed in the pipe outgoing from the source. Scenarios are constructed considering alternatively a PRV or an RTC valve, as pressure control device, and two different sites for hydrant activation. The results highlight that, thanks to its capability of controlling the service pressure at the critical node, the RTC valve performs better than the PRV, which is regulated based on its outlet pressure. In fact, the adoption of the RTC valve attenuates pressure deficits in the network, above all when the control time step is suitably small to attenuate pressure head oscillations at the controlled node. An additional benefit of RTC lies in increased outflows from the hydrant. The benefits of the RTC valve are smaller when the hydrant is activated in more redundant parts of the network, where pipe water discharge variations put the system to a less severe test.     

事故状态下供水管网的拓扑分析

当供水管网发生类似于爆管或水质污染等事故时,通过拓扑分析快速找到并关闭相应阀门以孤立事故源进而开展事故抢修是非常必要的。结合事故发生时管网的拓扑结构特点,以图论的理论和方法为基础,提出了一种可用于事故状态下供水管网拓扑分析的方法。该方法首先利用深度优先搜索算法找到距离事故源最近的阀门,然后通过剔除冗余阀门而确定最优关阀方案及关阀后的事故影响区域,最后调整管网水力模型以适应关阀后管网需水量和拓扑结构的变化。该方法不仅可用于供水管网事故时的关阀调度,还可用于供水系统污染控制分析以及供水管网的性能评价。     

给水管网阀门的技术管理探析

随着城市的扩张,给水管网不断地延伸,而给水管网中的节点都离不开阀门。笔者根据给水管网阀门的特点和种类,阐述了管网中阀门的选型,并进一步说明了阀门的技术管理,以提高阀门维护的能力,保证给水管网的运行。     

Fast network multi-objective design algorithm combined with an a posteriori procedure for reliability evaluation under various operational scenarios

This paper presents a methodology for the optimal design of water supply networks. It features a multi-objective optimisation (aimed at minimising costs and maximising resilience) and a subsequent ‘retrospective’ evaluation of network reliability under various operational scenarios. The multi-objective optimisation is based on an algorithm specifically developed for the design of real networks which feature a very high number of nodes and pipes. The ‘retrospective’ evaluation of network reliability is assessed considering resilience contrasted with several other indexes adopted to describe the operational performance of the network under critical scenarios such as segment isolation or hydrant activation, and different water demand conditions. In the applications two case studies, made up of a simple benchmark network and a real network respectively, are considered for the multi-objective optimisation; the ‘retrospective’ evaluation of reliability is performed only on the real network. The latter example clearly highlights that the procedure proposed allows reliability and performance to be offset against cost, consenting informed choice of the optimal network configuration.     

基于遗传算法的单向调压塔尺寸优化研究

介绍了单向调压塔水锤防护的工作原理及计算模型,对单向调压塔水锤防护效果的主要影响因素进行了分析。采用反问题分析方法,以单向调压塔直径、有效水深、补水管直径及水泵出口阀的关闭参数作为决策变量,以单向调压塔的容积最小作为目标函数,建立了单向调压塔尺寸和水泵出口阀关闭程序同时优化的数学模型,并采用改进遗传算法对优化模型进行求解。该优化模型和优化方法在实际工程中的应用表明,数值模拟结果较准确,由此确定的防护措施可靠。     

给水管网球阀局部阻力系数计算研究

为确定给水管网阀门的局部阻力系数,提出了一种基于几何计算和现场试验的局部阻力系数公式的构建方法。先通过几何计算建立球阀通流面积与阀芯旋转角度的关系,并以某转角下和全开时的通流面积之比作为球阀的面积开度,指出了传统的以阀芯旋转角度与全行程所需旋转角度之比作为球阀开度定义的缺陷。然后以DN20球阀作为试验对象,通过现场试验,采集各开度下的压差和流量值并计算出相应的局部阻力系数,经曲线拟合,建立了面积开度与球阀局部阻力系数之间的关系。另一组面积开度和球阀局部阻力系数的试验数据表明,该计算公式能有效地应用于球阀局部阻力系数计算。     

阀门调节技术在郑州市供水管网调度中的应用

以郑州市供水管网调度为例,结合实际分析了阀门在管网流量调节、压力调节中的作用,提出了通过调控管网关键阀门达到调节各水厂供水区域、保证管网压力均衡的思路和方法.     

高层建筑室内消火栓给水管道设计探讨

阐述了高层建筑室内消火栓给水管道和阀门市置成环状管网的设计特点。并结合室内消火栓系统用水量,分析了三种环网的适用条件,指出对于设计中的具体问题应根据规范,灵活解决。     

A multi-objective approach for detecting and responding to accidental and intentional contamination events in water distribution systems

The protection against contamination events in water distribution systems involves two distinct phases: detection of the presence of a contaminant and implementation of actions to isolate and/or expel it rapidly. The problem of detection is confronted by installing a series of monitoring stations, strategically placed across the distribution system and consisting of sensors to detect the presence of contaminants. The actions to be implemented may include operations on distribution system devices (valves and hydrants) or injection of reagents to eliminate the contaminant, or simply alert users. The procedure proposed here attempts to address the problems related to the two phases by means of two consecutive optimisation processes, both of them performed off-line and assuming a specific 24-hour water demand sequence in each network node, whereas the accidental/intentional injection of contaminant can occur in any node and at any hour of the day. With reference to this vast range of possible injection scenarios, the first multi-objective optimisation process defines the position of a pre-selected number n_s of sensors across the distribution system in order to minimise the expected percentage of undetected contamination events and the expected volume of contaminated water consumed up to the beginning of the response operations following detection. A single configuration of stations is then selected from the Pareto front produced by this optimisation process (‘knee point’ of the Pareto front). At the end of this first optimisation process and with reference to the selected set of sensors, a potentially contaminated area in the network is associated to each sensor for each sub-period of the day. The second multi-objective optimisation process is then aimed to identify, with reference to each station and sub-period, and thus inside the corresponding potentially contaminated area, the hydrant-opening and valve-closing operations to be carried out in order to minimise both the number of operations and the expected volume of contaminated water consumed between the beginning of the response operations and the disappearance of the contaminant, assuming the availability of an unlimited number of response teams. Once these devices have been identified (‘knee point’ of the Pareto front relevant to the second optimisation process), an a posteriori analysis is performed to determine the sequence in which they should be activated based on the number of response teams actually available. In these optimisation processes, a hydraulic and quality simulator (EPANET) is linked to a multi-objective genetic algorithm (NSGA-II) in order to compute the value of the objective functions of the problem across different contamination scenarios. The results obtained applying the procedure to a real and complex water distribution system have shown it to be a robust and effective method for reducing the impact on the population.     

基于GIS的城市供水管网爆管预测预警信息系统

城市供水管网爆管预测预警信息系统以地理信息系统(GIS)为基本框架,加载管网基本属性及供水系统运行数据,采用生存分析和贝叶斯定理建立爆管模糊预测模型;将GIS空间分析功能引入爆管规律分析与研究,建立了爆管的缓冲区分析模型和关闸搜索分析模型,对爆管在空间的分布规律进行分类和综合评价;将预警理论应用于爆管预防日常管理,提出爆管预警指标,结合不同爆管环境、条件,制定合理警限,划分警级,进行爆管状态预警。该系统可为管网管理者提供爆管查询统计、空间分析和预测预警等快速、多层次和直观的信息,以保证管网供水安全。     

梯级泵站串联加压长距离输水的水锤特点及防护措施

远距离输水中的串联加压梯级泵站水锤特性与传统的单级泵站相比有所不同,为此分析了串联加压梯级泵站水锤的各种成因及其过程,提出采取设置带止回装置的旁通管的方式消除因泵站事故引起的高压水锤,采取在管线上间隔0.8 km左右设置一个排气阀的方式消除因事故引起的低压水锤.     

城市天然气输配系统阀门的选用

介绍了城市天然气输配系统阀门的要求和阀门壳体材质的选用。分析了各种天然气阀门的适用范围以及选用的注意事项。     

Steady-State Analysis of Water Distribution Networks Including Pressure-Reducing Valves

Hydraulic networks that contain controlling elements such as pressure-reducing valves (PRVs) are difficult to simulate. Limited literature exists on the explicit modeling of PRVs in a general solution procedure for steady-state analysis of water distribution systems. It is also known that inclusion of PRVs may lead to numerical difficulties. The objective of this article is to develop and present in sufficient detail the modeling of PRVs in combination with the linear theory method for steady-state analysis of water distribution networks. The presentation is explicit enough and leads to a robust algorithm that can be directly implemented in a computer program. The general methodology for simulating water distribution networks that embodies graph theoretic concepts, hydraulic theory, and numerical algorithms is reviewed.     

基于WebGIS的供水管网爆管事故关阀分析研究

利用WebGIS技术建立了爆管事故关阀分析系统,深入研究了管网要素之间的网络拓扑关系,分析了基于邻接表存储结构的爆管事故关阀分析流程,得出了爆管事故状态下的最优关阀方案和受影响管段.以某供水管网为例,实现了爆管事故时的关阀分析.该系统的建立大大降低了爆管事故造成的经济损失,提高了供水企业的现代化管理水平.     

KR500X泄压阀在长输管道中的应用

泄压阀是水力控制阀的一种,能有效防止水击。详细介绍了泄压阀的结构、工作原理、特点、安装和日常维护注意事项。泄压阀通径的选用还没有成熟的理论依据,扬州第五水厂选用泄压阀的方法是一次探索。水厂投产两年来,输水管道运行平稳,确保了城市供水安全。     

谱聚类在给水管网分区优化中的应用

利用图划分技术和图论算法实现给水管网分区。根据给水管网分析,确定分区数量,建立权重邻接矩阵并计算图拉普拉斯矩阵及其特征向量,通过多路图划分对隐藏在特征向量中的聚类信息进行数据挖掘,采用遗传算法和K均值方法实现最佳节点聚类。利用PageRank和最短路径算法确定水表和阀门位置,最终实现给水管网优化分区。实际给水管网模型分区实例表明所提方法在给水管网分区的有效性。     

基于模糊数学的供水管网水质安全性评价方法探讨

供水管网水质安全性评价对于提高供水调度与管理水平十分重要。提出了利用模糊数学解决复杂的水质安全性评价问题的方法。详细分析了余氯指标的评价标准,并以某城市供水管网为例研究了余氯的模糊评价方法。评价结果与实际水质状况相符,说明该模糊评判方法可用于管网水质的评价。     

空调水系统中定压差控制水力平衡措施相关问题探讨(一)——自力式压差平衡阀的选型

为了更好地研究定压差控制对电动调节阀实际流量特性的改善程度,提出了自力式压差平衡阀选型的三要素:阀门公称压力、控制压差和流量系数。分析了四类典型空调水系统中各末端自力式压差平衡阀的计算工况,并按某算例对各系统的末端自力式压差平衡阀进行了实际选型。     

Design strategy to maximize recovery energy towards smart water grids: case study

Water distribution networks (WDNs) appear as a new opportunity to generate clean energy using pumps working as turbines (PATs) instead of pressure reduction valves (PRVs). This research presents a strategy for maximizing the recovered energy, and the development of a deep feasibility analysis, enabling the selection of the best scenario and operation mode. A design for a strategy to create an acceptable PAT working in a water distribution network and maximizing energy production, without affecting the water distribution service, is presented. The characteristic parameters of the system are described, evaluating efficiency, capabilities, reliability and sustainability. In addition, an economic analysis of the project was made to evaluate the viability of PAT implementation. The total energy production in this case study was 485 MW?h/year; and the feasibility indexes, internal rate of return, benefit/cost ratio and payback period were 0.79, 8.2 and 2 years, respectively.