Effect of continuous negative pressure water supply on the growth, development and physiological mechanism of Capsicum annuum L.

Effects of continuous negative pressure water supply on water consumption, growth and development, as well as physiological mechanism and quality of Capsicum annuum L. were investigated in this paper. Meanwhile, the optimal negative pressure water supply conditions for growth of C. annuum L. were screened out to achieve the goals of water conservation, high yield and high quality, thus providing theoretical foundation for its field production. The pot experiment within the greenhouse was utilized; the continuous negative pressure water supply was adopted; the four treatments, artificial watering（CK）, –5 k Pa（T1）, –10 k Pa（T2）, and –15 k Pa（T3） were set; and the daily water consumption, yield, as well as the biomass, nitrate reductase, root activity, vitamin C, capsaicin, and nutrient uptakes of nitrogen（N）, phosphorus（P） and potassium（K） during various stages of its growth were determined. Compared with CK, when the water supply pressure was controlled at –5 to –15 k Pa in the experiment, the total water consumption of C. annuum L. reduced by 53.42 to 67.75%, the total water consumption intensity reduced by 54.29 to 67.14%, and the water use efficiency increased by 12.66 to 124.67%. The N accumulation in a single strain of C. annuum L. from the color turning stage to the red ripe stage increased by 15.99 to 100.55%, respectively, compared with that of CK; the P accumulation increased by 20.47 to 154.00% relative to that of CK, and the K accumulation increased by 64.92 to 144.9% compared with that of CK. Compared with CK, C. annuum L. yield was remarkably improved by 13.79% at T1, and contents of vitamin C, capsaicin as well as carotenoids at all growth stages were enhanced by 13.42–147.01%, 11.54–71.01%, and 41.1–568.06%, respectively. Nitrate reductase activity, root activity and chlorophyll（a＋b） were markedly increased by 335.78–500%, 79.6–140.68% and 114.95–676.19%, respectively, from immature stage to full ripe stage. Adopting the continuous negative pressure water supply for C. annuum L. has a significant water-saving effect, and the water supply pressure being stable at –5 k Pa contributes to its growth and development, improves yield, enhances root activity, promotes nutrient uptake, and improves its quality, thus achieving the effects of water conservation, high yield, high quality and high efficiency.

Serviceability evaluation of water supply networks under seismic loads utilizing their operational physical mechanism

The serviceability of water supply networks(WSNs)under seismic loads has significant importance for estimating the probable losses and the impact of diminished functionality on affected communities.The innovation presented in this paper is suggesting a new strategy to evaluate the seismic serviceability of WSNs,utilizing their operational physical mechanism.On one hand,this method can obtain the seismic serviceability of each node as well as entire WSNs.On the other hand,this method can dynamically reflect the propagation of randomness from ground motions to WSNs.First,a finite element model is established to capture the seismic response of buried pipe networks,and a leakage model is suggested to obtain the leakage area of WSNs.Second,the transient flow analysis of WSNs with or without leakage is derived to obtain dynamic water flow and pressure.Third,the seismic serviceability of WSNs is analyzed based on the probability density evolution method(PDEM).Finally,the seismic serviceability of a real WSN in Mianzhu city is assessed to illustrate the method.The case study shows that randomness from the ground motions can obviously affect the leakage state and the probability density of the nodal head during earthquakes.

Evaluation of “C” Values to Head Loss and Water Pressure Due to Pipe Aging: Case Study of Uni-Central Sarawak

Samarahan has transformed from a small village into education hub for the past 2 decades. Rapid development and population growth had led to speedy growth in water demand. The situation is getting worse as the pipes are deteriorating due to pipe aging. Therefore, there is a need to study the adequacy of water supply and relationships among roughness coefficient (C) values in Hazen Williams’ Equation with head loss and water pressure due to pipe aging at Uni-Central, a residential area located at Samarahan Sarawak. Investigations were carried out with Ductile Iron, Abestos Cement and Cast Iron pipes at age categories of 0 - 10 years, 10 - 30 years, 30 - 50 years, 50 - 70 years and >70 years. Six critical nodes named as A, B, C, D, E and F were identified to study the water pressure and head loss. Model was developed with InfoWorks Water Supply (WS) Pro software. The impact of pipe aging and materials to water pressure and head loss was not significant at Nodes A, B, C and F. However, max water pressure at Nodes D and F were only reaching 6.30 m and 7.30 m, respectively for all investigations. Therefore, some improvement works are required. Results also show that Asbestos Cement pipe has the least impact on the head loss and water pressure, followed by Ductile Iron pipe and lastly Cast Iron pipe. Simulation results also revealed that older pipes have higher roughness coefficients, indicated with lower “C” values, thus increase the head loss and reduce the water pressure. In contrast, as “C” values increased, head loss will be reduced and water pressure will be increased.

Functionality analysis of an urban water supply network after strong earthquakes

An urban water supply network(WSN)is a crucial lifeline system that helps to maintain the normal functioning of modern society.However,the hydraulic analysis of a significantly damaged WSN that suffers from pipe breaks or leaks remains challenging.In this paper,a probability-based framework is proposed to assess the functionality of WSNs in the aftermath of powerful earthquakes.The serviceability of the WSN is quantified by using a comprehensive index that considers nodal water flow and nodal pressure.This index includes a coefficient that reflects the relative importance of these two parameters.The demand reduction(DR)method,which reduces the water flow of nodes while preventing the negative pressure of nodes,is proposed.The difference between the negative pressure elimination(NPE)method and the DR method is discussed by using the example of a WSN in a medium-sized city in China.The functionality values of the WSN are 0.76 and 0.99 when nodal pressure and nodal demands are used respectively as the index of system serviceability at an intensity level that would pertain to an earthquake considered to occur at a maximum level.When the intensity of ground motion is as high as 0.4 g,the DR method requires fewer samples than the NPE method to obtain accurate results.The NPE method eliminates most of the pipes,which may be unrealistic.

室外消防临时高压给水系统的供水方式分析

针对室外消防临时高压给水系统的供水方式和要求,叙述了室外消防临时高压给水系统的增压方式。分析室外消防临时高压给水系统车载设施增压方式和固定设施增压方式的特点及实用性,并提出采取车载设施增压方式应具备的条件;在列举若干消防规范中对临时高压给水系统压力的相关要求的基础上,依据消防供水压力的配置要求和作用,提出了高层建筑消防临时高压给水系统的压力配置建议思路和要求。

基于PLC与变频器的恒压供水系统设计

采用PLC和变频器相结合设计恒压供水系统,采集管网的水压力,经A/D转换后送入PLC,经PLC的PID运算后输出信号来控制变频器的输出电压和频率,改变电动机的转速来改变供水量,最终使管网水压力值稳定在恒定值。实践证明,该系统稳定可靠,同时还具有良好的节能效果。

基于FCM-GA灌溉供水管网减压阀布设优化

为探究灌溉供水管网中存在的漏损过高以及局部压力过大的问题,提出了一种基于FCM-GA的供水管网减压阀布设优化方法,该方法借助MATLAB、EPANET、MATLAB-EPANET-Toolkit以及PlatEMO平台等工具,对西班牙的BIN管网进行分区布置减压阀并优化阀后压力,以不同分区方案的成本与降漏效果为控制指标,筛选出最优方案。结果显示:最优方案(分5个区)将整个管网的漏损率降低至7.45%,相较初始管网降低了20.04%,降低的漏损费用可达114€/d,在减压阀服务年限内可收回成本并达到盈利,并实现对整个管网系统的压力管理,提高了管网的稳定性和可靠性,有利于减少管网事故发生。因此,基于FCM-GA的灌溉供水管网减压阀布设优化是一种安全、低成本和高效益的降漏与控压方法,在有效降低灌溉用水费用的同时,可更好地实现节水灌溉。

厂区级冷却供水系统智能控制设计实现

某厂区冷却供水系统只能以手动模式运行,无法实现自动恒压供水,能耗高、设备损耗大,对管网流量波动适应性差;通过重新设计系统PLC程序,进行加减泵逻辑控制和管网压力设置,实现了基于变频器的管网恒压控制;通过水泵轮巡逻辑控制和冗余配置,实现了水泵的自动轮换运行;通过水泵使能功能和管网压力手动设置功能,提高了系统控制的灵活性;通过优化水泵加载条件和触摸屏功能,消除了设备故障对系统自动运行的干扰;经过10个月运行验证,系统一直稳定工作,水泵运行数量减少三分之一,管网运行压力降低12.8%,可设置参数由3个增加到15个,冷却供水泵组节能23%以上。

二次供水叠压设备准入判据及管网压力变幅分区方法

为了明确叠压供水方式的准入标准,提出了用于叠压供水设备选取及城市给水管网压力变幅分区的判据,并对其重要参数——叠压最小允许压力H_(dmin)、叠压最大压力波动ΔH_(dmax)进行原理分析,据此判据将城市给水管网划分为压力稳健区、压力波动区、压力脆弱区,并以在西部A市自来水公司GIS、SCADA系统采集的2022年西部A市主城区年最大用水日时全部供水节点的日最大水压、最小水压为可信数据,作出西部A市主城区给水管网的压力变幅分区图,以此作为西部A市主城区叠压供水设备选取的参考依据。

一种新型组合式喷雾降尘装置流场及雾化特性试验研究

喷雾降尘是工业粉尘治理的常规技术手段,传统喷雾降尘技术存在降尘效率低、耗水量大及无法实现远距离降尘等缺陷。通过提出一种新型组合式喷雾降尘装置,并基于自行设计的气水喷雾试验平台,对该新型装置气流场分布规律、雾化粒度的空间分布规律以及相关影响因素开展试验研究。结果显示:组合式喷雾降尘装置能够将喷雾吹送至较远的降尘区域,实现远距离降尘,且装置尾部可抽吸周围含尘气体,与雾滴一并喷出,达到二次降尘效果;随着供气压力的增加,组合式喷雾降尘装置的喷雾速度呈幂函数形式增大,随着与喷口处距离的增加,装置喷雾速度自出口沿下游呈指数函数形式衰减;负压随着供气压力的增大而增大,装置尾部产生的吸气量随供气压力的增加而不断增大;随着供气压力的增加,装置的射程不断增大,增大供水压力对装置射程的提升较小;雾滴粒径随着供气压力的增加呈先增大后减小的趋势,且沿轴线方向上的不同位置的雾滴粒径呈相同的变化规律;当供气压力一定时,装置的雾滴粒径随供水压力的增加而减小。综合考虑,组合式喷雾降尘装置在现场应用时,供气压力和供水压力分别为0.4 MPa和2.0 MPa时较为合理。

叠压供水系统对市政管网的影响分析

叠压供水充分利用管网余压进行变频恒压供水,具有节能、供水水质稳定等优点。然而叠压供水系统直接与市政管网相连,启动时会引起接入点及管网上下游的流量和压力波动,对市政管网输送水量变化和压力变化带来影响。以江苏省JT城区的市政管网为研究对象,采用EPANET软件执行延时模拟、HAMMER软件执行瞬时模拟,分析叠压供水系统对市政管网的影响程度和规律,并确定了两个评价指标:最低市政供水压力要求和系统接入点运行压降要求。结果表明,叠压供水系统对市政管网的影响与小区入住率、用水时段、叠压数量等因素有关;小区附近叠压供水系统数量越少、分布越稀疏,多叠压供水系统运行时接入点压降就越小。当实际应用中影响超出安全范围时,建议通过优化控制方式和供水方式缓解影响,保障供水安全。

多水源地长距离供水工程恒定流水力仿真研究

本文基于压力管道水力学基本理论,针对长距离多泵站、多水源地供水联合运行问题,建立供水工程管网系统恒定流水力仿真模型,分别求解日常运行、常规检修与应急抢险等不同工况下管网系统中各点的压力与流量变化情况,从而检验系统的运行情况。结果表明,各工况下该供水系统压力极值都符合管道的承压标准,具备安全过流条件,可为类似供水工程的运行提供一定的参考作用。

PLC自控系统在北河口水厂二期工程中的应用

结合北河口水厂二期工程实例,介绍了PLC自动控制系统在自来水厂中的应用情况,对自来水厂的建设有着重要参考价值。

多若特阀门在减压模式下的故障分析与处理

岩滩水电站一期工程技术供水系统中所使用的多若特阀门在经过可调减压升级改造后,相关的减压导阀、控制电磁阀、水力继动器等模块相继出现异常和故障,导致多若特阀门频繁失控。笔者统计了多若特阀门在减压模式下出现的异常和故障,并进行原因分析,提出相应的处理措施。结果表明:故障主要表现为密封件损坏漏水、PLC程序故障、管接头裂纹渗水以及减压导阀、电磁阀、水力继动器失灵等;通过采取替换易损配件和易堵阀门、更换适合的过滤器等措施,最终消除多若特阀门在可调减压模式下失控的安全隐患。该研究成果可为类似水电站技术供水系统阀门故障处理提供借鉴。

基于热混合润滑的钢/橡胶接触表面水润滑增强调控

目的增强钢/橡胶摩擦副的润滑性能,为提高混合润滑状态下水润滑轴承的性能提供参考。方法建立水润滑条件下钢/橡胶摩擦副的热混合润滑模型,讨论热效应对润滑性能的影响,并在此基础上进一步研究表面粗糙度、水基润滑剂黏度和供水压力对水润滑增强调控的作用。结果与等温解相比,热效应使Stribeck曲线发生了右移,摩擦因数和载荷比增大,膜厚比降低。最高水膜温度随着转速的增加而升高,热效应对混合润滑性能的影响显著。减小摩擦副表面粗糙度,Stribeck曲线向左移动。在相同转速下,载荷比随着表面粗糙度的减小而降低,膜厚比反之。表面粗糙度越大,水膜温度越高,最高温度位于出口区,且钢的表面温度低于水膜和橡胶的表面温度。当水基润滑剂的黏度增大时,膜厚比增大,载荷比和最高水膜温度降低,Stribeck曲线发生左移。增加供水压力可以改善水膜压力分布,使水膜承载区增大、压力减小,粗糙峰接触压力和承载区减小,导致载荷比减小、膜厚比增加,Stribeck曲线向左偏移,水膜最高温度降低。当接触区由边界润滑向混合润滑过渡时,水膜最高温度出现拐点,且水膜最高温度拐点随着供水压力的增加而左移。结论热效应会降低摩擦副的混合润滑性能,因此在混合润滑中不能忽略。考虑热效应时,通过减小表面粗糙度,或增加水基润滑剂黏度和供水压力,均有利于增强钢/橡胶接触表面水润滑的混合润滑性能。

基于压力相关的城市供水管网漏失预警研究

近年来极端天气频发,加之我国大部分城市长期存在严重的缺水问题,因此为节约有限的淡水资源,及时发现城市供水管网漏失事故十分必要。首先通过某市供水管网历史压力数据分析了正常运行工况下的压力数据特征;然后探讨了当供水管网发生漏失事故时影响漏失点压力变化的因素,并利用FLUENT流体模拟软件进行仿真模拟验证;最后在各种工况压力变化规律的基础上建立了供水管网压力波动阈,当监测压力值超出压力波动阈,综合考虑压力监测点单一时刻的压力波动程度及一个时间周期内的压力变化趋势等多方面的因素,来预警供水管网是否发生漏失事故,并以某市供水管网为例,验证了所提漏失预警方法有效、可行。

轨道交通工程中消火栓系统设计关键技术探讨

为设计出更加安全可靠、经济合理的轨道交通工程,介绍南京—马鞍山城际铁路(简称宁马线)消火栓系统设计中的一些关键技术及其相对于常规传统设计的优点。首先,在对规范解读及工程经验分析的基础上,首次提出“轨道交通工程中,为了保证消防安全,消防泵房保护距离尽量控制在2000 m以内”的原则。为了将此理念落实到具体设计中,在本工程中提出一种新的消防供水方案,即“消防供水多方案组合模式”,具体内容为:1)优先选用一站带左右各半个相邻区间的方案;2)当区间长度小于2000 m时,也可以采用一站带一相邻区间方案;3)当区间长度大于4000 m时,在一站带左右各半个相邻区间方案的基础上,在区间风井处设置独立的消防泵房,以保证所有消防泵房的保护距离控制在2000 m以内;4)将各消防泵房的供水单元完全独立。其次,在车站给水水压制式方面,提出2种单路水源高架站的消防供水方案及其适用范围,即:1)室外低压、室内临时高压系统,适用范围为“高架站布置在市政道路一侧,并且车站离市区较近、消防基础设施条件较好,能保证足量消防车及时赶到火灾现场”或“条件特别困难的既有高架车站改造”;2)室内外共用临时高压消防系统,适用范围为“高架站布置在市政道路中央”或“车站离市区较远、消防基础设施条件比较不利,不能保证足量消防车及时赶到火灾现场”。最后,在消防设施布置方面,提出“高架车站室外消防水池、扑救类室外消火栓”的布置原则,其中最重要的2条为:1)室外低压、室内临时高压系统中,当高架站超出消防水池150 m保护半径时,应增设相应的消防水池取水井;2)车站扑救面上布置室外消火栓时,应优先布置在每个高架站出入口附近。

山地城市给水管网压力分区策略研究与应用

山地丘陵地区的城市供水管网,在满足用户用水需求的同时,可能面临局部区域压力过高的问题,而高压会导致供水管网的漏损量增加。依托某山地城市供水管网水力模型,提出“界限清晰、压力均衡、水头递减、局部加压”的分区分压策略,对供水管网进行压力分区划分,配合基于时间的阀后压力控制方式进行分区控压,相比于传统的阀后压力控制方式,能够更好地减少管网漏失水量,均衡管网压力,为山地城市供水系统的运行提供了重要参考。

黄土的连续加荷固结试验的有限元分析

应用常应变率模型对重塑黄土进行有限元分析。通过不同的应变率模型试验,结果表明试样中竖向有效应力的增长速度随着应变率的增大而增大。应变率越大,加载后期最终的有效应力值也越大;孔压的上升速度越快,达到相同压缩量孔压所产生的幅值也越大,常应变率试验中孔压缓慢上升中途并未出现水压力消散的现象。常应变率试验在加载初期试样不同深度的水平面有效应力分布均匀,克服了常规固结试验中加荷瞬时,有效应力分布不均造成的试样压缩的不均匀这个缺点。与室内固结试验结果进行了比较分析,结果表明所采用的数值分析方法能较好地模拟黄土的固结试验过程,对揭示土体固结变形有一定的实际意义。

170m以下超高层建筑(群)消防给水设计探讨

对“一泵到顶”供水方式的极限应用高度进行探讨,研究“临时高压重力消防给水系统”的可行性,并针对170m以下超高层建筑或建筑群,探讨一种相对经济合理的消防给水系统设计方案。“临时高压重力消防给水系统”取消低区独立的消防加压泵组,低区消防系统由高位水箱重力供给,简化了系统形式,提高了系统的经济性,对于此类建筑的消防给水系统优化具有积极意义。