基于模糊PID的城市供水恒压控制研究

鉴于城市供水恒压控制系统水压因季节性和时段性不同而波动大的问题,采用传统的PID控制不能满足动态控制要求,本文提出了基于模糊PID的恒压控制方法,根据供水压力系统反馈管网供水不利点压力的变化情况,调整控制系统相应PID控制参数,满足快速动态响应的要求。仿真对比实验证明基于模糊PID的恒压供水控制超调量小、响应速度快,解决了城市供水时变系统智能控制问题。     

变压力设定值供水控制系统设计

目前供水系统依靠变频调速实现恒压供水,通过闭环控制,用水量的变化使水泵自动调节转速从而改变水泵供水量,最终使供水管某处的压力恒定不变。此控制方式存在一定的弊端。提出一种随着用水量的变化自动改变供水管网压力的变压力控制方法,并以三台供水泵组成的供水系统为例,给出相应的电气主电路及其控制电路,选择变频器,给出变频器相关控制端的接线图,并对供水压力设定值的调节方法作了说明。     

给水管网水力模型的建立及应用

某市供水管网水力模型以管网地理信息系统、客户营销系统、数据采集与监控系统为基础,整合三大系统的数据,采用计算机模拟的方式来表现供水管网各管段及泵站的流量、压力、流速、流向、水力坡度变化,分析和评价管网布设的合理程度及运行规律,优化管网设计,完善供水调度方案．该模型的建立及应用能够为决策者提供参考依据,使供水企业逐渐告别粗放型的管网运行管理模式,令供水管网处于良性运行状态．     

建筑给水设计中节能节水技术探讨

本文对建筑给水设计中节能节水的特点及技术措施的应用等方面进行探讨.给水系统应充分利用市政供水管网压力直接供水或叠压供水,采用加压的供水系统应进行合理的分区及选择供水设备,控制用户用水点的水压,生活热水系统中热源的选择,是在建筑给水设计中应注意的问题.     

埋地给水用UPVC管的应用

给水管网的基建投资大约占给水工程总投资的三分之二。因此，正确地选用管道材料，对确保满足管网工况(工作压力、流量、流速等)的要求，保证供水水质，同时降低工程造价便于管道施工，都具有十分重要的意义。     

PLC控制变频调速恒压供水系统

介绍了自行设计的恒压供水系统,采用可编程序控制器进行逻辑控制,采用变频器进行压力调节。变频器、可编程序控制器作为系统控制的核心部件,时刻跟踪管网压力与给定压力的偏差变化,经变频器内部PID运算,通过可编程序控制器控制变频与工频切换,自动控制水泵投入的台数和电机转速,实现闭环自动调节恒压变量供水,在保持恒压下达到控制流量的目的。     

关于供水管网漏水的维护

在现实的生产和生活中,供水管网的漏水已成为一个普遍问题。管网漏水会导致供水压力的下降、供水不足,而且还容易造成地下的污水浸入给水管内从而污染水质,影响生产和产品质量,危害人民的身体健康。同时还会使漏水周围土质松软,对地下埋设物、道路交通及附近建筑物的安全构成潜在的威胁。     

基于AutoCAD的供水管网管理系统的开发及应用

通过AutoCAD的超链接功能和数据库连接功能，建立了简单实用的“供水管网管理系统”，实现了对许昌市区供水管网竣工资料的计算机动态管理，并对该系统的基本功能、实现方法和需要注意的问题进行了详细阐述．经使用认为：许昌市区“供水管网管理系统”操作简单、维护方便、实用性强．     

供水管网节点流量不确定性对漏损定位的影响

供水管网中的节点流量具有不确定性,为了研究节点流量不确定性对供水管网漏损定位能力的影响,建立供水管网节点流量分布在不同条件下的需求分布水力模型。一种是供水管网中各节点平均分配流入量的均匀模型,另一种是在供水管网各节点按需分配流入量的分配模型,比较两种需求分布模型的漏损定位性能。利用加权最小二乘算法完成供水管网水力模型的漏损定位,加权最小二乘算法具有模型精度高和计算效率高的优点,该方法通过计算供水管网中监测值与水力模型模拟值的差异,判断是否发生漏损,并能准确定位漏损节点。最后通过实例证明供水管网节点流量的不确定性对供水管网漏损定位性能有突出影响。     

铜陵市供水管网地理信息系统建立及应用

近年来随着铜陵市的迅速发展和供水管网规模的不断扩大,供水管网的更新改建频繁,现有的管理手段已无法满足"合理规划、科学管理、安全用水、优质服务"的要求。铜陵首创水务有限责任公司采用先进的计算机网络技术、通信技术和地理信息技术,建立了铜陵首创供水管网地理信息系统。系统建立后全面存储管网图形和属性信息,并可随时动态更新维护。应用结果表明:铜陵市供水管网地理信息系统的建立大大提高了供水管网管理和运营水平。     

商业建筑空调水系统中环路阻力分布模拟分析

本文在管网水力计算模型的基础上,建立回路优化的数学模型,可以对管网进行优化调节,以使所有用户的水流量达到设计流量.根据一个商业建筑空调实例,分析了空调水系统中的环路阻力分布状况.结果表明,对应建筑不同使用功能的空调系统分区,其水系统各支路之间设计压力损失相差较大.为了实施有效合理的初调节,有必要进行管网的模拟初调节,掌握所有水系统用户的初始水量分配,且能找出管网中真正的最不利环路.     

新型给水管材水力工况对比分析

通过对各种新型给水管材之间水力工况的比较和分析，推得各种管径的新型给水管材与相应公称直径的镀锌钢管单位长度水头损失的比值K，由于管材间水力工况的不同，在工程设计、旅工中更换管材时，不能简单地用相同或相近管径的管材互相替代，而应重新对系统进行水力计算。     

Partial least squares regression model to predict water quality in urban water distribution systems

The water distribution system of one residential district in Tianjin is taken as an example to analyze the changes of water quality. Partial least squares (PLS) regression model, in which the turbidity and Fe are regarded as con-trol objectives, is used to establish the statistical model. The experimental results indicate that the PLS regression model has good predicted results of water quality compared with the monitored data. The percentages of absolute relative error (below 15%, 20%, 30%) are 44.4%, 66.7%, 100% (turbidity) and 33.3%, 44.4%, 77.8% (Fe) on the 4th sampling point; 77.8%, 88.9%, 88.9% (turbidity) and 44.4%, 55.6%, 66.7% (Fe) on the 5th sampling point.     

Simulation investigation on fluid characteristics of jet pipe water hydraulic servo valve based on CFD

Simulation investigation on fluid characteristics of the water hydraulic jet pipe servo valve (WHJPSV) is conducted through a commercial computational fluid dynamics (CFD) software package FLUENT. In particular, the factors to fluid characteristics of WHJPSV are addressed, which include diameter combination of jet pipe and receiver pipe, jet pipe nozzle clearance, angle between two jet receiver pipes and deflection angle of the jet pipe. It is concluded from the results that: (i) Structural parameters have ...     

Elastoplastic pipe-soil interaction analyses of partially-supported jointed water mains

Water distribution networks are essential components of water supply systems. The combination of pipe structural deterioration and mechanics leads to the failure of pipelines. A physical model for estimating the pipe failure must include both the pipe deterioration model and mechanics model. Winkler pipe-soil interaction （WPSI）, an analytical mechanics model developed by Rajani and Tesfamariam （2004）, takes external and internal loads, temperature changes, loss of bedding support, and the elastoplastic effect of soil into consideration. Based on the WPSI model, a method to evaluate the elastic and plastic areas was proposed in the present study. An FEM model based on pipe-soil interaction （PSI） element was used to verify the analytical model. Sensitivity analyses indicate that the soft soil, long pipe and high temperature induced the axial plastic deformation more likely, which, however, may not occur in normal scenarios. The soft soil, pipes in small diameters, long unsupported bedding are prone to form flexural plastic area. The results show that the pipes subjected to the same loads have smaller stresses in the elastoplastic analysis than elastic analysis. The difference, however, is slight.     

水冲助沉预应力管桩的工艺控制及其效果

通过工程实例，论证静压管桩可根据压桩力有选择地进行水冲助沉穿越密实砂层，并通过静载试验对比证明其效果。     

衡水湖微生物菌群分布的研究

研究了衡水湖水体4个水平采样点(深水区、芦苇区、香蒲区、荷花区)的主要理化指标与微生物菌群的丰度及分布,研究结果表明,深水区的水质量最好,其次是芦苇区、香蒲区和荷花区.同时讨论了水体微生物与TN和TP等生态因子之间的关系,以及水体污染物的来源及其保护治理的措施.     

Seismic reliability and rehabilitation decision of water distribution system

in order to evaluate the seismic reliability of water distribution system and make rehabilitation decisions correspondingly, it is necessary to assess pipelines damage states and conduct functional analysis based on pipe leak- age model. When an earthquake occurred, the water distribution system kept serving with leakage. By adding a virtual node at the centre of the pipeline with leakage, an efficient approach to pressure-driven analysis was developed for simulating a variety of low relative scenarios, and a hydraulic leakage model was also built to perform hydraulic analy- sis of the water supply network with seismic damage. Then the mean-first-order-second-moment method was used to analyse the seismic serviceability of the water distribution system. According to the assessment analysis, pipes that were destroyed or in heavy leakage were isolated and repaired emergently, which improved the water supply capability of the network and would constitute the basis for enhancing seismic reliability of the system. The proposed approach to seismic reliability and rehabilitation decision analysis on water distribution system is demonstrated effective through a case study.     

An assessment model of water pipe condition using Bayesian inference

An accurate understanding of the condition of a pipe is important for maintaining acceptable levels of service and providing appropriate strategies for maintenance and rehabilitation in water supply systems. Many factors contribute to pipe deterioration. To consolidate information on these factors to assess the condition of water pipes, this study employed a new approach based on Bayesian configuration against pipe condition to generate factor weights. Ten pipe factors from three pipe materials （cast iron, ductile cast iron and steel） were used in this study. The factors included size, age, inner coating, outer coating, soil condition, bedding condition, trench depth, electrical recharge, the number of road lanes, material, and operational pressure. To address identification problems that arise when switching from pipe factor information to actual pipe condition, informative prior factor weight distribution based on the literature and previous knowledge of water pipe assessment was used. The influence of each factor on the results of pipe assessment was estimated. Results suggested that factors that with smaller weight values or with weights having relative stable posterior means and narrow uncertainty bounds, would have less influence on pipe conditions. The model was the most sensitive to variations of pipe age. Using numerical experiments of different factor combinations, a simplified model, excluding factors such as trench depth, electrical recharge, and the number of road lanes, is provided. The proposed Bayesian inference approach provides a more reliable assessment of pipe deterioration.     

城市自来水管道腐蚀对水质和管道的影响

本文通过对发生泄漏的自来水管道取样分析,找出了管道腐蚀和水质劣化的影响因素,指出了管道腐蚀机理,对腐蚀管道的安全性进行了评估。