速差法超声波气体流量计的原理和校准

本文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计的工作原理，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％．     

用吸收光谱法测量COIL的水汽含量

 分析了利用吸收光谱法测量氧碘化学激光器的水汽含量的原理，在氯气流量为0.1 mol/s的N₂-COIL上进行了测试实验。实验结果显示，在常规工作条件下，由于BHP温度变化所引起的水汽百分含量变化仅为0.1%，可以忽略；水汽含量随稀释气体流量增大而增加，气体流速是引起水汽含量变化的主要原因，实验中应把氯气和氧气的比例控制在4∶1之内。     

气流和外加磁场对负电晕放电特性的影响

利用线-筒电晕放电装置,研究了气体流动和外加磁场对负电晕放电的影响。当电压固定时,电晕放电电流随气体流量的增加先快速增大,并到达一个高点后迅速下降,随着流量的进一步上升,放电电流又开始缓慢增加。外加磁场能增加电晕放电的电流,但在高的气体流速下,磁场将降低电晕放电的电流,同时外加磁场增加臭氧的产生,直到温度上升导致它的快速降解。     

气泡在横流中的生长与脱离特性实验研究

为了系统研究气泡在横流中的运动学特性,利用水循环回路形成横流,采用高速数码摄像技术和图像处理方法对横流中气泡的演化过程进行描述。通过调节横流的平均流速和气体流量,获得了6种横流中的气泡形态,即单气泡、颈状泡、条带泡、泡囊、离散泡和雾状泡;解释了各类气泡形态的特征,对气泡尺寸及分布进行了统计,对气泡在横流中的发展过程进行了描述,发现气泡形态及气泡尺寸与横流速度密切相关,并受气体流量的影响,其中颈状泡和条带泡对横流流速的变化最为敏感。     

超声波流速测量的多普勒频移提取方法研究

为了提高超声波多普勒法测量复杂流体流量的精度,针对流体的超声回波频率的复杂性,本文研究多普勒流速测量中的频偏提取方法。以傅里叶分析为理论基础,设计了硬件电路并获得代表回波平均频率的信号,然后以该信号作为输入,以数字鉴频法获得回波多普勒频移。基于该方法设计了一种超声多普勒流量测量系统,实验结果显示:油水混合流体流量的测量误差在3%以内,从而证实了此频偏提取方法的有效性。     

氮稀释气体氧碘化学激光3维喷管流动模拟

 应用改进的3维化学反应流程序，对基于RADICL装置、以氮气为稀释气体的化学氧碘激光喷管流动做了数值模拟。给出了达到合适副气流穿深的主副气流匹配条件，考虑了提高水汽流量、改变主副气流总温对增益系数的影响，比较了与以氦气为稀释气体的不同特点。结果发现：氮气作为稀释气体条件下，混合气体的流速低，静压大，在亚声速区驻留时间长，碘分子离解快，使得增益系数峰值增大，且下降快。模拟结果提示：改变喷管结构，将副气流喷孔下移，增益分布得到了改善。     

气体的粘滞流动──研究泊肃叶定律的一个简单实验

本文介绍一个简单的实验装置，用来研究气体粘度及通过管子的气体流量．对流量与管子长度和半径的依赖性分别作了检验。     

液体流动条件下毛细管管口气泡动力特性实验

通过对液体流动条件下毛细管管口气泡生长及脱离过程进行可视化实验.分析了毛细管管壁浸润性,液体流速以及气体流量对气泡生长脱离过程的影响.实验结果表明:随着液体流速的增大,液体对气泡的横向剪切力增大,气泡的脱离周期减小,气泡的脱离直径也随着减小.同时,实验还发现随着气体流量的增大,使气泡生长动力增大,气泡的脱离周期减小;另外,实验还揭示出毛细管管壁浸润性的改变,将导致气泡生长过程中气固液三相接触线发生径向迁移.     

氢箱置换过程中气体流量控制技术试验研究

针对发射场氢箱低压置换过程搭建了缩比试验装置,通过试验考察了不同气体流量控制方法的可行性及流量调节特征。试验结果表明,采用气体调节阀进行气体流量控制的方法响应时间短,流量调节结果平稳可控,是较优的控制方法,试验结果为发射场置换流程中的气体流量控制提供了依据。     

激光器件 化学激光器

TH248.52006010140用吸收光谱法测量COIL的水汽含量=Measurement ofwater vapor content in COIL by absorption spectroscopy at1392nm[刊,中]/赵伟力(中科院大连化物所.辽宁,大连(116023)),王增强…∥强激光与粒子束.—2005,17(7).—1000-1002分析了利用吸收光谱法测量氧磺化学激光器的水汽含量的原理,在氯气流量为0.1mol/s的N2-COIL上进行了测试实验。实验结果显示,在常规工作条件下,由于BHP温度变化所引起的水汽百分含量变化仅为0.1%,可以忽略;水汽含量随稀释气体流量增大而增加,气体流速是引起水汽含量变化的主要原因,实验中应…     

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。     

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.