Study on the Technology of Supplying Water Safely by Long-Distance Pipeline

The extensively built long-distance water transmission pipelines have become the main water sources for urban areas. To ensure the reliability and safety of the water supply, from the viewpoint of overall management, it would be necessary to establish a system of information management for the pipeline. The monitoring, calculating and analyzing functions of the system serve to give controlling instructions and safe operating rules to the automatic equipment and technician, making sure the resistance coefficient distribution along the pipeline is reasonable; the hydraulic state transition is smooth when operating conditions change or water supply accidents occur, avoiding the damage of water hammer. This paper covered the composition structures of the information management system of long-distance water transmission pipelines and the functions of the subsystems, and finally elaborated on the approaches and steps of building a mathematics model for the analysis of dynamic hydraulic status.

Improvement of heat-tolerance by training I. Evaluation of effects of long-distance running and march training on heat-tolerance

in order to verify the heat-tolerance effect, two trainings, 90 min marching with load (WBGT 24. 6～35.6℃) and 10 km running (WBGT 25.0～31.1℃) were performed in laboratory and field under hot climate.Ten to twelve times (days) of training were carried out

Prediction Analysis on the Transport Distance of Supply Air in Warm Air Heating Room with Impinging Jet Ventilation Systems

To overcome the disadvantages of displacement ventilation( DV) and traditional mixing ventilation( MV) system,a new ventilation system known as impinging jet ventilation system( IJVS)has been developing. The warm air can be supplied with impinging jet ventilation( IJV), while the DV is only used for cooling.However,the flow and temperature field of IJV under heating scenario has had few references. The paper is mainly focused on computational fluid dynamics( CFD) and developing an adequate correlation between the distance L that warm air can reach and different parameters in the warm IJVS by using response surface methodology( RSM). The results indicate that L decreases as the supply velocity υ decreases but increases as the supply temperature difference ΔT or the discharge height h decreases. In the variable air volume( VAV) system, it is necessary to determine supply parameters both under the maximum-heat-load condition and the small-heat-load condition. Unlike the VAV system,the constant air volume( CAV) system has no need to study the small-heat-load condition. Draught discomfort near the nozzle becomes the issue of concern in IJVS, thus the suitable discharge height is of great importance in design and can be calculated based on the predictive model.

Scheme of long distance power supply for electrified railway traction network based on traction cable

Purpose–The traction cable is paralleled with the existing traction network of electrified railway through transverse connecting line to form the scheme of long distance power supply for the traction network.This paper aims to study the scheme composition and power supply distance(PSD)of the scheme.Design/methodology/approach–Based on the structure of parallel traction network(referred to as“cable traction network(CTN)”),the power supply modes(PSMs)are divided into cableþdirect PSM and cableþautotransformer(AT)PSM(including Japanese mode,French mode and new mode).Taking cableþJapanese AT PSM as an example,the scheme of long distance power supply for CTN under the PSMs of co-phase and out-of-phase power supply are designed.On the basis of establishing the equivalent circuit model and the chain circuit model of CTN,taking the train working voltage as the constraint condition,and based on the power flow calculation of multiple train loads,the calculation formula and process for determining the PSD of CTN are given.The impedance and PSD of CTN under the cableþAT PSM are simulated and analyzed,and a certain line is taken as an example to compare the scheme design.Findings–Results show that the equivalent impedance of CTN under the cableþAT PSM is smaller,and the PSD is about 2.5 times of that under the AT PSM,which can effectively increase the PSD and the flexibility of external power supply location.Originality/value–The research content can effectively improve the PSD of traction power supply system and has important reference value for the engineering application of the scheme.

Experimental Investigation on Thermal Characteristics of Long Distance Loop Heat Pipes

Loop heat pipes(LHPs)are attractive two-phase thermal control devices for satellites,electronics and many other applications.They are capable of transporting heat efficiently for long distances up to several meters at any orientation.This paper investigated the heat transfer characteristics of loop heat pipes with long distances and small diameter transport lines.Small stainless steel tubes of 2 mm and 3 mm in inner diameters were chosen as liquid lines and vapor lines of the LHPs.The local thermal resistances in the evaporator of the 6 m-LHP were researched and analyzed,which indicated that the thermal resistance between the aluminum block and the vapor in the vapor channel accounted for a major proportion of the total thermal resistance.The effect of heat sink temperatures on the performance of the 6 m-LHP were compared with 10°C,15°C,20°C and 25°C cooling water temperatures.Moreover,the thermal characteristics of LHPs with transport distances of 2 m and 16 m were also experimentally investigated.The 16 m-LHP could achieve a heat transfer capacity of 100 W and the 2 m-LHP could reach more than 339 W,on the premise of the evaporator temperature below 100°C.The thermal resistance of the 2 m-LHP could achieve 0.125°C/W.

Stomatal movement in response to long distance-communicated signals initiated by heat shock in partial roots of Commelina communis L.

The systematic or long-distance signal transmission plays crucial roles inanimal lives. Compared with animals, however, much less is known about the roles of long-distancesignal communication in plant lives. Using the model plant Commelina communisL, we have probed theroot to shoot communication mediated by heat-shock signals. The results showed that a heat shock of5 min at 40°C in partial roots, i.e. half or even 1/4 root system, could lead to a significantdecrease in stomatal conductance. The regulation capability depends on both heat shock temperatureand the amount of root system, i.e. with higher temperature and more roots stressed, the leafconductance would decrease more significantly. Interestingly, the stomatal regulation by heat shocksignal is in a manner of oscillation: when stomata conductance decreased to the lowest level withinabout 30 min, it would increase rapidly and sometimes even exceed the initial level, and afterseveral cycles the stomata conductance would be finallystabilized at a lower level. Feeding xylemsap collected from heat-shocked plants could lead to a decrease in stomata conductance, suggestingthat the heat shock-initiated signal is basically a positive signal. Further studies showed thatheat shock wasnot able to affect ABA content in xylem sap, and also, not able to lead to a decreasein leaf water status, which suggested that the stomatal regulation was neither mediated by ABA norby a hydraulic signal. Heat shock could lead to an increase in xylemsap H_2O_2 content, andmoreover, the removal of H_2O_2 by catalase could partially recover the stomatal inhibition by xylemsap collected from heat-shocked plants, suggesting that H_2O_2 might be able to act as one of theroot signals to control the stomatal movement. Due to the fact that heat-shock and drought areusually two concomitant stresses, the stomatal regulation by heat-shock signal should be ofsignificance for plant response to stresses. The observation for the stomatal regulation in anoscillation manner by presently identified new signals should contribute to further understanding ofthe mystery for the pant systematic signaling in response to stresses.

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。

地下空间长距离送风中转站通风设计

针对送风系统存在众多分支导致的阻力不均、风量减小等问题,提出了设置中转站的送风方式。本文以长方体送风中转站为例,采用模拟和实验相结合的方法,研究了送风中转站的空气分布特性与设计参数。结果表明:送风中转站可以将系统最不利出口的流量偏差由124.01%降低至33.14%;送风中转站的出口数量对其阻力与流量均匀性的影响较大。在此基础上,给出了送风中转站的设计方法。

深地空间长距离空气输送系统方案比较及优化研究

以某深地空间长距离送风系统为例,采用Ventsim软件计算了4种风量调节方案的系统风机风压与管道阻力的变化,提出了增加干管风机数量和改变进风竖井位置2种优化方法,分析了送风系统管网阻抗与等积孔面积的变化。结果表明,优化后送风系统的管网阻抗和等积孔面积分别最大降低0.102 kg/m^(7)和0.030 m^(2),科学的送风方案既能满足风量需求,又能降低长距离送风系统的阻力,具有较好的节能与经济效益。

局部制冷降温技术在井下长距离掘进中的应用

为解决玲珑金矿深部长距离掘进巷道的高温问题,结合井下低温涌水条件,通过对输冷方式和换热方式进行分析,制定了以水源热泵技术为基础的局部制冷降温技术方案,采用理论计算和模拟仿真方法,模拟不同供风温度和供风量条件下巷道的温度场变化情况,分析得出了最佳制冷参数,并开展了制冷系统的设备选型和现场应用。结果表明:-750 m中段长距离掘进工作面的制冷最佳温度为10℃,供风量为5.0 m3/s;根据制冷方案和制冷参数分析结果对局部制冷降温技术进行了应用,有效解决了系统供水不足和供风沿途冷损大等难题,掘进工作面温度由37.0℃降至26.2℃,降幅达10.8℃,距工作面50 m范围内运输巷道温度平均降幅分别为8.9℃和2.9℃,掘进巷高温环境得到明显改善。该局部制冷通风降温技术的应用对类似矿山的深部热害治理具有技术参考价值。

基于ARM和CC-Link的恒压供水加压站设计

文中提出了一种基于ARM和CC-Link的恒压供水加压站设计方法,进行了硬件的设计、驱动程序以及应用程序的开发。使用ARM9微处理器和CC-Link远程设备站芯片MFP3作为系统的硬件平台,Linux作为操作系统,应用程序使用Qt/Embedded编写。通过实际运行表明,系统运行稳定,可以灵活地组建不同需求的恒压供水系统,存储和显示远程设备站工作运行情况,实现了系统设计的功能要求。

市政给排水施工中的长距离顶管施工技术研究

以某工程为例,针对传统顶管施工出现的质量问题,分析顶管施工地面变形情况,通过工作井施工、穿墙施工、管道顶进施工、管线纠偏、土压平衡控制,有效控制长距离顶管施工工艺,以此提高施工效率与质量,提出新型施工技术。由实例可知,新施工技术在使用时,能够平衡控制土体压力,防止地面出现变形。

长输供热管道经济比摩阻的影响因素分析

为推动大面积清洁供暖,分布式燃煤、燃气锅炉房逐步被热电联产所取代。与热电联产配套的长输供热管道成为常见的一种供热设备。长输供热管道比摩阻的选取,在项目建设运行经济性上起到重要的作用。以呼和浩特市某一长输供热管道工程项目为例,采用单因素分析法,探究了不同工程参数对经济比摩阻的影响。计算结果显示该工程的实际最佳经济比摩阻为22.8 Pa/m。以实际工程为例,详细分析了经济比摩阻的优化过程,同时分析了各因素对经济比摩阻的影响程度,供热温差对经济比摩阻的影响最大,供热负荷次之,供热年限最小。因此在设计经济比摩阻时,应着重考虑工程项目的供热温差。

长输直埋供热管道材质和壁厚的选取

以宁夏华电灵武公司向银川市长距离大温差集中供热项目为例,为了保证长输供热管道的安全性,以长输供热工程对供热管道的要求为出发点,选取长输供热工程中直埋供热管道的材质和壁厚。结果显示:工作管管径小于DN800时,管道材质选用Q235B;工作管管径大于等于DN800时,管道材质选用Q355B材质的工作管。研究表明,该方案能够满足工程管网运行的安全性且成本较低。

顶管技术在市政给排水工程中的应用研究

近年来,顶管施工技术的顶进距离不断增加,在埋深较大的工程中顶管技术也被广泛应用,需要顶管施工克服复杂地质条件限制,满足工程建设质量需求,确保工程施工效率。文章介绍了某给排水工程应用顶管技术进行长距离顶管施工的情况,分析了施工关键流程、施工操作要点,并对施工中的技术控制和问题处理措施进行了研究,旨在帮助技术人员了解顶管施工技术的要点,提升在市政给排水工程中顶管技术的应用水平,满足城市建设需求。

长输供热管网压力平衡波纹补偿器比选

为解决长输供热管网工程中补偿器的选型难题,以内外压旁通直管、全外压旁通直管、内压直管、外压直管这4种压力平衡波纹补偿器作为研究对象,利用START应力软件及局部阻力模拟进行仿真计算,分析其性能结构、应力荷载及局部阻力,对应用案例进行经济性分析,并结合国内成功案例,分析可得内压直管压力平衡型波纹补偿器架空敷设,安全性高、承压能力强、稳定性好;压损仅有0.001 MPa;初投资低、运行费用低。故推荐内压直管压力平衡型波纹补偿器。

基于直流远供技术的市域快线LTE远端设备供电方案研究

[目的]针对市域快线长大区间设备供电需求,传统城市轨道交通区间的WLAN(无线局域网络)、TD-LTE(分时长期演进)远端设备的点对点、交叉冗余供电方式,存在线缆浪费、电力资源损耗、冗余度低等问题。[方法]尝试提出运用直流远供技术解决电力资源远距离输送,进而优化长大区间远端设备供电方案。[结果及结论]直流远供技术可以满足市域快线长大区间供电需求,单点故障不会造成无线通信中断,可进一步提升供电系统冗余度、可靠性。设备配备的监控子系统,可同步纳入信号微机监测系统,以实现供电系统闭环管理。

长距离泵站水锤分析及管线布置对水锤的影响

针对长距离供水工程中泵站事故停泵后管线后段负压成常态的问题,以甘肃某水库临库取水泵站为背景,建立了水锤基本方程、液控止回偏心半球阀和空气罐等数学模型.采用特征线法分析了泵后工作阀关闭规律以及增设空气罐和改变管线布置形式对水锤的影响.实例分析表明:泵后工作阀的关闭规律对管线负压的影响较小;管线出现“瞬时负压”在一些情况下可以忽略其对管道的危害;空气罐能够较好地解决长距离供水工程中泵站后段管线在设置一定数量的空气阀后依然无法消除“瞬时负压”的缺陷;改变管线布置形式对管线负压极值的影响较小,呈直线形式的水锤最大压力明显大于高低起伏形式的管线,采用先缓后陡的管线布置形式能够缩短负压发生的区域.研究结果可为长距离供水工程水锤防护设计提供一定参考.

煤矿井下变频器电缆长距离供电引起问题的分析研究与对策

煤矿井下受现场空间安装尺寸或通风散热条件影响,变频器和电动机之间一般距离比较远,通常采用长距离供电电缆进行连接,但是由于电缆长距离供电会给变频调速系统带来一系列负面影响,导致变频器和电动机之间连接的电缆分布寄生电容太大,同时电机绕组之间也会产生大量的寄生电容,二者之间的共同作用产生过电压现象,严重影响整个系统的运行性能。提出了使用无功补偿器、更换变频器和两电平逆变电路的可行性等方法。结果表明,本次研究能够很好地解决煤矿井下变频器电缆长距离供电引起的问题,抑制共模电压,提高了井下现场运行的可靠性。

D1219 mm管道山地自动焊系统研制及应用

针对长输管道山地自动焊施工技术难题,研制了D1219 mm柔性内焊机、热煨弯管坡口机、吊管机、焊接工程车等山地系统焊接施工装备;同时试制加长型热煨弯管,满足了热煨弯管与直管自动焊和AUT检测要求。在水平0°和斜30°位置,钢级L555M,D1219 mm×18.4 mm直管与D1219 mm×22 mm加长型热煨弯管组对后,采用山地柔性内焊机、双焊炬自动焊机进行了自动焊工艺试验,无损检测、力学性能试验结果均合格。山地柔性内焊机在川气出川二线山区段进行了工业化应用,实现了从山底到山顶、通过加长型热煨弯管、再从山顶到山底的不留断点连续自动焊的施工。