大流量高精度超声波流量计应用

在大流量计量方面,除大流量高精度超声波流量计外,还有流速仪测量法、量水堰测量法和电磁流量计。在使用中,它们各自有优点又都有局限性。而大流量高精度超声波流量计有着上述计量方法所无法取代的优越性,它尤其适用于明渠计量。北京市城市河湖管理处经过12年的使用,取得了一些经验和体会,同时也有一些问题需要在今后的使用中加以解决。     

乡镇供水计量监控方案

近年，电池供电电磁流量计（流量压力测量远传终端）在实际应用中日臻成熟，MAG-AX电池供电电磁流量计和AX8000水计量及区域漏控系统已在广东及江浙等东南沿海经济发达地区城乡供水一体化进程中逐步推广应用，深圳市拓安信自动化仪表有限公司开发的电池供电电磁流量计及AX8000水计量及区域漏控系统，已应用在农业灌溉用水、乡村生活用水、乡镇企业用水等领域。     

淹没柔性植被明渠恒定水流水力特性研究

采用三维多普勒超声测速仪(ADV)对淹没柔性植被明渠恒定水流的水力特性进行了实验研究。采用羽毛来模拟天然河道的柔性植被,对不同的植被密度、不同淹没度和不同流量条件下柔性植被明渠恒定水流流速场进行了测量,得到了淹没植被情况下纵向流速和雷诺应力沿垂向的分布。分析表明,植被上层区域与植被区域水流表现出不同的水力特性,植被上层区域的雷诺应力近似为直线分布,纵向流速呈经典的对数律分布;而植被区域,纵向流速则呈“S”型分布。在分析植被上层水流雷诺应力与纵向流速的关系的基础上,利用普朗特混合长度理论推导了植被上层水流流速的理论表达式,理论公式所得结果与实测数据符合良好。     

淹没柔性植被明渠恒定水流水力特性的试验研究

采用三维多普勒超声测速仪(ADV)对淹没柔性植被明渠恒定水流的水力特性进行了试验研究。采用羽毛来模拟天然河道的柔性植被,对不同的植被密度、不同淹没度和不同流量条件下柔性植被明渠恒定水流流速场进行了测量,得到了淹没植被情况下纵向流速和雷诺应力沿垂向的分布。结果表明,植被上层区域与植被区域水流表现出不同的水力特性,植被上层区域的雷诺应力近似为直线分布,纵向流速呈经典的对数律分布;而植被区域,纵向流速则呈“S”型分布。在分析植被上层水流雷诺应力与纵向流速的关系的基础上,利用普朗特混合长度理论推导了植被上层水流流速的理论表达式,该公式的计算结果与实测数据符合良好。     

插入式流速仪装置述评

0 前言 插入式流速仪通常归为这样一类装置,根据管内临界点位置的单个流速测量,推导出总体流速值。插入式流速仪由流速传感器、支撑架、安装配件和压力密封装置组成。与全管径测量仪不同,这种流速仪装置通过管壁的开孔插入流体内。插入式流速仪为用户提供了低价的仪器及重复的流量测量。进行全管测量流速的技术——涡流、涡轮、压差、电磁、声波等也可作为插入式流速仪来测量流     

南水北调工程陶岔站时差法流量计推流技术研究

陶岔水文站为南水北调中线工程源头陶岔渠首水量计量断面,为提高陶岔站超声波时差法流量计的流量测验精度,对时差法流量计算原理及推流方法进行了研究,提出了基于多元回归的多声路时差法断面平均流速计算方法,并以实测流量为率定样本,验证了该方法的适用性。同时,基于走航式ADCP测验资料,分析了陶岔站垂线流速分布规律及最优幂指数,以及幂指数对ADCP流量测验精度的影响。结果表明：基于多元回归的多声路时差法断面平均流速计算方法能进一步提高陶岔站流量监测的精度;陶岔站垂线流速分布符合幂函数分布,最优幂指数为0.120 8,在用走航式ADCP进行流量测验时,建议采用该系数,可减小单次流量测验误差1%～2%。研究成果可为流量在线监测推流方法的选择及推流精度的提高提供参考。     

不同流量计在污水流量测量中的性能比较分析

由于污水来源不同,所含污染物质也多种多样,总体来说都比较脏、含有大量杂物、甚至还有腐蚀性。一般污水测量中选择明渠堰槽流量计、超声波流量计和电磁流量计的比较普遍。文中将Endress+Hauser电磁流量计(以下简称E+H电磁流量计)与常用的超声波流量计和明渠流量计在污水测量中的性能进行了对比,从分析,结果表明,Endress+Hauser电磁流量计更适合污水流量的测量,能对污水测流起到实时准确的监控。     

电磁流量计在供水企业中的应用

电磁流量计是根据法拉第电磁感应定律来测量体积流量的仪表,只适用于导电液体流量测量,输出电流与瞬时流量呈线性关系,并不受流体物理性质(温度、压力、密度和粘度)的影响,累计流量则由脉冲信号输出.电磁流量计测量范围宽,同一台电磁流量计可达1:100,其口径也可以从1cm到2 m以上.     

浑水条件下水头及流量测量方法探讨

从浑水水头的定义入手,提出了以一个压力场和两个速度场为前提的浑水水头表达方式,并在对欧拉数、压力系数、流量系数等相似参数进行细致分析的基础上,进一步确认了两相流条件下浑水水头的相似表达。其次,本文还探讨了泥沙等固体颗粒进入压力测量管路给测量结果带来的不确定性和巨大影响,介绍了浑水水头的正确测量方法,推导了避免泥沙颗粒进入测压管路的浑水水头测量计算公式,提出了通过测量泥沙流量浓度和体积浓度的方式间接测量计算泥沙流速和清水流速的方法。关于固液两相流的流量测量,主要介绍了电磁流量计不受固体颗粒影响并可高精度测量浑水流量的原理,论述了固体颗粒对文透里流量计测试浑水流量的影响,介绍了水轮机蜗壳压差流量计在浑水条件下高低压两侧泥沙浓度的巨大差异,分析了其产生的原因及对流量测试的影响,提出了初步的解决办法。     

基于GSM/GPRS网络的无压损管网检漏系统的研究及应用

基于GSM/GPRS网络,采用电磁漩涡流量计对管网进行实时监测。在不造成管网压损的条件下,可根据监测的数据判断是否存在偷水、漏水情况,不但能为供水企业提供所需要的管网流量、温度、压力数据,还能对供水管网流量、温度、压力变化状况进行监测。研究了某钢厂动力分厂配备电磁漩涡流量计的运行情况,预计试用4台电磁漩涡流量计10年间累计取得经济效益517 255.48元。进而得出若逐步在全厂推广,则经济效益将更加可观,同时解决了水厂与用户之间的计量纠纷问题。     

STEADY ENTRANCE FLOW IN A STRAIGHT CIRCULAR PIPE WITH SLOWLY VARYING CROSS SECTION

1.INTRODUCTIONItiswellknownthatmanyvasculardiseasesarecloselyrelatedtothebloodflowinves-sels[1-3j.Thebloodflowthroughthearterieswithvaryingcrosssectionhasheldthein-terestsofmanyinvestigatorsforalongtimeL4-6j.Inthepreviousstudies,thebloodf1owinarterieswas,however,assumedtobefullydeveloped.Sincestenosesfrequentlydevelopatsitesneartheoriginofbranches[2-3j,whichareintheentranceregion,itisimportanttostudytheentranceflowinaconverging-divergingpipe,whichisamodelofentrancestenosis-Manyinvestigat…     

EXPERIMENTAL STUDY OF VELOCITY DISTRIBUTIONS IN THE TRANSITION REGION OF PIPES

The accuracy of an ultrasonic flowmeter meaurement depends on the profile-linear average velocity.But this velocity in the transition region is not available at the present.In this article,the velocity in the transition region in pipes is studied by experimental methods.The Particle Image Velocimetry (PIV) is used to measure the flow field in the transition region in pipes,and the measured results from PIV are in good agreement with the Westerwell’s experimental data.Based on the experimental data of PIV,the curves of the profile-linear average velocity in the transition region against the Reynolds number in the range from 2 000 to 20 000 are obtained,and it is shown that the coefficient k is constant when the Reynolds number is in the range of 2 000-2 400 and 6 000-20 000,and the coefficient k is increasing when the Reynolds number is in the range of 2 400-6 000.The results of this article can be used to improve the measurement accuracy of the ultrasonic flowmeters and as a theoretical basis for the research on the transition flow.     

声学多普勒测流原理及应用研究

声学多普勒测流（ADCP）利用声学多普勒原理测量水流剖面的流速,是一种高精度流体测流方法。多普勒测流与传统测流方法相比,具有测验分辨率高、精确度好、信息量大、资料完整等优点,尤其适用于复杂环境下的流体流速、流量的测量。文章透过多普勒测流与传统测流的对比,详细地阐述了多普勒测流的原理及方法。     

分布随从力作用的双参数地基上悬臂管稳定性研究

为了对分布随从力作用时双参数地基上悬臂管稳定性进行分析,利用Euler-Bernoulli梁模型创立输流管道的运动微分方程,然后运用传递矩阵法进行求解。通过分析悬臂输流管的无量纲复频率和失稳时临界流速间的关系,在地基刚度取4种不同值情况下研究悬臂管道受分布随从力和流体流速作用时的振动情况。结果表明①地基刚度取值一定时,悬臂管道受分布随从力和流体流速影响时的振动特点大不一样;②无量纲分布随从力与流体流速取值一定时,管道系统的振动状况随着地基刚度增加而更加稳定,相比线性刚度的影响剪切刚度的作用尤为突出。     

THE FLOW IN ROTATING CURVED CIRCULAR PIPE

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圆管螺旋流输沙特性试验研究

螺旋流的流速分布有着与普通平直流不同的特点 ;运用圆管螺旋流的特性可以在管道中实现高浓度 ,远距离的泥沙输送。本文在试验的基础上对螺旋管流中的流速分布、泥沙的起动、起旋以及输沙等特性进行了研究 ,同时进行了理论分析 ,探讨了螺旋流高浓度输沙的可能性。     

Air flow inside a vertical pipe induced by a free-falling water jet

The air flow induced by a water jet freely falling inside a vertical pipe with its top and bottom both open to the atmosphere was investigated experimentally and numerically. In the experiments, the radial air velocity distribution and the air pressure variation along the vertical pipe were measured. The air drag of the falling water jet was related to the jet surface disturbance and analyzed by introducing the equivalent friction factor. A predictive model was developed for the air flow inside a 3-m-high pipe based on the momentum equation and its results compared well with the experimental measurements. Numerical simulations were also conducted by approximating the free-falling water jet as a continuous moving solid with diameter and velocity varying in the direction of motion. The effects of pipe size on the air velocity profile and the induced air flow rate were examined. The simulation results showed that the streamwise air velocity profiles inside pipes of different sizes approached the same after a certain traveling distance. The maximum induced air flow rate was found at the pipe diameter of about 20 times of initial water jet diameter.     

管道高浓度泥浆阻力系数的试验研究

选择典型堤防淤筑工程与典型管道泥浆输送施工设备，采用现场观测对泥浆管道阻力系数进行了试验研究。作者利用实测管道压力、流量、含沙量等数据对高含沙水流阻力特性进行分析，取得了在管道粗糙过渡区泥浆沿程阻力系数受Re数、含沙量影响的基本认识，进一步给出了常规条件下沿程阻力系数与综合泥浆因子间相关关系及计算方法。同时还对典型管道泥浆局部阻力也进行了分析研究，提出了在考虑水流强度、泥沙因子的条件下泥浆局部阻力系数的确定方法。研究成果可供泥浆管道水力设计与泥浆管道施工定额编制时参考使用。     

EXPERIMENTAL AND NUMERICAL ANALYSIS OF LAMINAR AND LOW TURBULENT FLOW DISTRIBUTIONS IN INLET DIVIDING HEADER OF SHELL AND TUBE HEAT EXCHANGER

Flow distribution headers play a major role in heat exchangers. The selection of header diameter, branch pipe diameter, branch pipe spacing etc. is based on the designer's experience and general guide lines. The proper selection of the header dimensions will yield uniform flow distribution in heat exchangers, which in turn will enhance the heat exchanger efficiency. In this work, the flow distribution in branch pipes and the pressure variation across the branch pipes in laminar and low turbulence region is studied with two models of the inlet dividing headers. When the numerical analysis has been applied, its inability to predict the no flow condition through the branch pipes is revealed. The results are presented in the form of flow rate ratio through branch pipes and nondimensional coefficients across branch pipes which are useful to apply the existing mathematical models for the present experimental setup.     

Numerical investigation of the concentric annulus flow around a cylindrical body with contrasted effecting factors

This paper studies the wall-bounded flow around a cylindrical at a high Reynolds numbers body in a determined computational domain, with simulations of the 3-D, turbulent concentric annulus flow in a straight pipe. Numerical results show that a reversing zone, appearing as a tongue zone with nested velocities higher than the surrounding area, exists behind the cylindrical body. The annulus space is a region of high velocity and low pressure. The zero velocity, of combined the X- velocity and the Y- velocity, exists in the cross sections and no vortex shedding is formed behind the attaching cylinders. Among all investigated effecting factors, the diameters of the attaching and the main cylinders affect the wake feature behind the cylindrical body while the main cylinder length does not affect the distribution tendency of the flow field. The diameters of the main cylinder and the pipe affect the pressure values and the distribution tendencies on the main cylinder surface. Obviously, the increase of the pipe diameter reduces the drag coefficient of the cylindrical body and the increase of the diameter of the main cylinder increases the drag coefficient greatly. The numerical investigation of the concentric annulus flow provides foundations for further improvements of the intricate flow studies.