速差法超声波气体流量计的原理和校准

本简要地介绍一种利用超声脉冲沿顺、逆流方向上传播速度之差来测定气体流速及流量的新的微机化超声波气体流量的工作原理，以及它在内径为７００ｍｍ，流速在３－１３ｍ／ｓ范围内的校准结果，实验结果表明该微机化超声气体流量计的测速精度优于±２％。     

超声波测流量

一、超声波测流量的优点 利用超声波测量液体和气体的流速、流量,很早就有人研究,由于技术水平所限,一直没有很大发展．最近几十年由于电子技术的进步,超声波流量计获得实际应用,而且日益完善,与经典的流量计相比,超声波流量计具有下述优点： １．超声波流量计能作成非接触式,可对不易接触和观察的流体进行测量． ２．超声波流量计不受流体物理性质和化学性质的影响,诸如流体的粘性、导电性、混浊性及腐蚀性等均不防碍超声波流量计的应用． ３．超声波流量计的指示读数与所测流体流量成线性函数,便于流量的直接读数、记录和流量累…     

超声波气体流量计的标定

本文简要介绍了超声波速差气体流量计的性能,及利用调温调湿风沿和煤气厂储气柜对直径为φ７００ｍｍ的大口径超声气体流量计进行喷嘴法的体积法要示定的原理,过程及测量结果。     

自调式J-T制冷器流量测量的流量计选用

针对自调式J-T制冷器的流量测量,介绍了几种常用的气体流量计,结合制冷器的实际需求对其进行了分析,认为从进气端测量科里奥利质量流量计较为合适,而在排气端测量选用湿式气体流量计较为合适。     

超声雾化和气体发生进样微波诱导等离子体原子发射光谱法测定痕量碘

本文用Ａｒ和ＨｅＭＩＰＡＥＳ测定水溶液中的碘。样品经超声雾化和气体发生后引入等离子体。考查了Ａｒ和ＨｅＭＩＰ中碘的发射光谱特性和一些实验参数对碘发射强度的影响。当用超声雾化引入样品时，用Ａｒ和Ｈｅ作工作气体，检出限分别为０．１２和０．０６μｇ／ｍｌ，当用气体发生引入样品时，用Ａｒ作工作气体，检出限为０．０６４μｇ／ｍｌ，相对标准偏差小于５％。     

基于超声波多普勒法的流通截面分区流速测量的研究

传统的超声波多普勒流量计测量的结果是大面积区域内具有统计意义的平均流速，不能反映流速在流通截面上的分布，当雷诺数变化很大时，测量误差很大。基于超声波多普勒效应，本文首次提出了通过对测量信息窗区域的控制，来实现在管流内部进行流速分区测量，进而测量出流速在流通截面上的分布。研制出发射传感器和接收传感器，分别能够产生细长的发射声束和接收声束，使得信息窗区域面积得以控制在很小的范围内，约 ２．１× ４．８ ｍｍ２，位置也被控制在设计值处，满足分区测量要求；在自行设计的模拟管道流动装置中，成功地进行了控制信息窗区域面积和位置的实验，测量值与设计值吻合很好。实现了管道流通截面上的流速分区测量。     

超声波气体流量计的时差法检测与数值分析

使用2组超声换能器制作了基于时差法的超声波流量计,并将其应用于圆形管道中流场的测试.依据实验中所使用的圆形管道测试系统,理论上使用有限元方法构建了圆形管道中稳恒流场的流速分析模型.数值分析结果表明:实验中获取的管道内流速为测试位置截面处流体的平均流速,该测试值与理论值相差5.2%.考虑到实际测试环境与理想流体测试环境间的差异,实验结果与理论分析结果基本一致.     

快速焓探针

传统焓探针测量系统采用质量流量计测量样品气体的流量，这种方法的缺点是强烈依赖于等离子体工作气体的组分以及在测量时必须等待在焓探头内样品气体流动达到稳定状态，因此测量时间较长.本文介绍的快速焓探针测量系统中，用一个已知体积的储气罐获得被抽样品气体的摩尔量，从而克服了传统焓探针的缺点，实现了在几秒之内完成对一点的焓值测量.本文从四个方面的实验验证了快速焓探针测量结果的准确性.     

粘性流体对涡轮流量计仪表系数影响的实验研究

流体的粘性对涡轮流量计的仪表系数有很大影响．本文使用活塞式液体标准体积管在不同粘度下对涡轮流量计进行了实验研究，得出了仪表系数与流量、流体的粘度之间关系曲线．     

声学消息

北京大学声学教研室与北京自来水公司共同研制的CJL-1型超声流量计,于1981年3月23日至27日在北京召开了鉴定会。与会代表40余人,来自全国有关的28个单位。 超声流量计具有管外安装的许多优点,工业先进国家已用于测量管道内各种液体的流量。CJL-1型超声流量计于1978年制成样机,经改进后循环频率稳定能自动修正错误并自动报警。自1980年2月正式投入生产运行以来,大量实测数据证明该机性能稳定可靠,可以投产推广应用。     

超声波流量计测量流体声速的实验方法

为获取液体介质的声速值,设计了一种测定流体声速的实验方法,该方法利用时差式超声波流量计和标准流量校验设备同时对封闭管道中的液体进行流速测量,分别得到流速的测量值和真实值,从而计算出超声波流量计的仪表系数,并以此导出了一定条件下液体介质的声速值随仪表系数的变化关系式.利用该方法测量给出了0.17 MPa下四氧化二氮(N₂O₄)在7.6-19.4 ℃、偏二甲肼((CH₃)₂NNH₂)在6.5-25.2 ℃范围内的流体声速值,并为其他液体介质的声速测量提供了借鉴. 关键词： 超声波流量计 声速 仪表系数 温度     

Resonant oscillations of a gas in an open tube in the shock-free wave mode

Nonlinear gas oscillations excited in an open tube by a flat piston at one of the tube ends are studied. The sinusoidal piston oscillations in the shock-free wave mode are created by a vibration exciter near the first eigenfrequency. Expressions for gas pressure oscillations are obtained for a tube with a nonrounded end without a flange and secondary flow velocity components. The influence of the piston displacement amplitude on the pressure range and secondary flow velocity of gas is studied. The theoretical calculations of the gas pressure are compared with experimental data. An estimate for the velocity of particle motion along the tube axis is presented with calculated values of the secondary flow velocity.     

Supersonic velocimetry in a shock tube using laser enhanced ionisation and planar laser induced fluorescence

 A novel flow-tagging technique is presented which was employed to measure gas velocities in the free stream of a shock tube. This method is based on the laser spectroscopic techniques of Laser-Enhanced Ionisation (LEI) and Laser-Induced Fluorescence (LIF). The flow in the shock tube is seeded with small amounts of sodium, and LEI is used to produce a substantial depletion of neutral sodium atom concentration in a well-defined region of the flow, by using two wavelength-resonance excitation and subsequent collisional ionisation. At a specific time delay, single-laser-pulse planar LIF is utilised to produce a two-dimensional (2-D) inverse image of the depleted tagged region downstream of the flow. By measuring the displacement of the tagged region, free stream velocities in a shock tube were determined. Large variations in the concentration of sodium seeded into the flow were observed and even in the presence of these large variations accurate free-stream velocity measurements were obtained. The experimentally determined value for velocity compares very well with the predicted velocity. Received: 25 March 1996/Revised version: 8 July 1996     

螺旋管内气液固三相流颗粒相分布规律

为了深入认识螺旋管多相流相分离现象,并为新型螺旋管除砂器设计提供指导,本文应用马尔文粒度仪,测量了螺旋管气水砂三相流底部水平段液膜中的颗粒浓度和粒度分布。研究表明:在泡状流和分层流条件下,螺旋管底部水平段可形成稳定的连续液膜流动;在宽广的气速范围内,液膜中的颗粒浓度分布规律均为内弯侧较低、外弯侧较高,说明螺旋管除砂器对于实际生产中流动工况的变化具有良好的适应性;泡状流中提高气速有利于分离;分层流中在中等气速条件下外弯侧颗粒浓度最大,中等气速是相分离的最佳操作工况。     

超声波流量计在飞机燃油流量测试中的应用研究

燃油系统输油流量测试是飞机燃油系统地面模拟试验的一项重要内容;由于试验油箱内部的各管路与真实飞机油箱管路的布置是一致的,不适合在油箱内的狭小空间安装涡轮流量计,并且会破坏管路流阻特性;由于使用传统油箱油量标定的方法进行输油流量测量耗时耗力,所以需要采用一种新的技术或测量方法来完成油箱输油流量的测量;超声波流量计体积小,不会破坏输油管路流阻特性,防爆等级也符合试验要求;对超声波流量计在浸油状态下测试进行可行性分析,将超声波流量计在飞机燃油系统试验中实现创新性应用;通过试验证明了超声波流量计在飞机燃油流量测试中发挥了重要作用,并且首次将超声波流量计应用到飞机试验油箱内部输油管路的流量测试中,这对飞机其他系统的流量测试和飞机机上排故试验起到了重要作用。     

Analysis on the feasibility of optical tomography in measuring gas jet flow velocity

Enlightened by the wide application of optical computerized tomography (OCT) in various flow fields’ visualization and parameter measurement, the potential feasibility of it on measuring gas jet flow velocity is discussed in this paper. The dependence of flow velocity on flow field's refractive index and dynamic pressure is deduced initially. An argon gas jet flow is chosen as an example for experiment, and the refractive index measurement is achieved by moiré tomography, while the dynamic pressure is obtained by a pressure sensor. In a word, both the theoretical and experimental results prove that OCT could be feasible to obtain the flow velocity of gas jet flows.     

Ultrasonic measurement of gas flow using electrostatic transducers

Ultrasonic gas flowmeters typically use narrowband piezoelectric transducer arrangements for interrogating the flow of gas in a pipe. In this work, the suitability of broadband electrostatic transducers operating at frequencies of up to 1 MHz for ultrasonic measurement of gas flow has been investigated. The transit time method of ultrasonic gas flow measurement was adopted and experiments were carried out using a laboratory test rig capable of producing a range of gas flowrates up to 17.5 m/s. The test rig also allowed easy interchange of different prototype flowmetering sections. Times of flight of ultrasonic waves interrogating the gas flow were measured using separate send/receive electrostatic transducer arrangements. Two flowmeter configurations were considered. The first interrogated the flow at 45 degrees in contra-propagating upstream and downstream directions. The second consisted of an up-stream interrogation at 45 degrees to the gas flow and an interrogation made normal to the flow direction. k factors correlating the fluid velocity along the ultrasonic path with the mean fluid velocity in the pipe were calculated using experimental ultrasonic data and anemometer measurements. All transducer configurations were numerically modelled using the computational fluid dynamics software package FLOTRAN (ANSYS Inc.). Theoretical gas flow velocities for both transducer arrangements were subsequently compared with experimental values and found to be in excellent agreement. A flow-dependent frequency shift of the received ultrasonic signals was also observed simultaneously with the transit time measurement.     

Theoretical analysis of stack gas emission velocity measurement by optical scintillation

Theoretical analysis for an online measurement of the stack gas flow velocity based on the optical scintillation method with a structure of two parallel optical paths is performed. The causes of optical scintillation in a stack are first introduced. Then, the principle of flow velocity measurement and its mathematical expression based on cross correlation of the optical scintillation are presented. The field test results show that the flow velocity measured by the proposed technique in this article is consistent with the value tested by the Pitot tube. It verifies the effectiveness of this method. Finally, by use of the structure function of logarithmic light intensity fluctuations, the theoretical explanation of optical scintillation spec- tral characteristic in low frequency is given. The analysis of the optical scintillation spectrum provides the basis for the measurement of the stack gas flow velocity and particle concentration simultaneously.