Ultrasonic flowmeters: temperature gradients and transducer geometry effects

Ultrasonic flowmeter performance is addressed for the case of cylindrically shaped flowmeters employing two reciprocal ultrasonic transducers A and B so as to measure time-of-flight differences between signals transmitted from transducer A towards B followed by an equivalent signal transmitted from transducer B towards A. In the case where a liquid flows through the flowmeter's measuring section ("spoolpiece"), the arrival times of the two signals differ by an amount related to the flow passing between the two transducers. Firstly, a detailed study of flow measurement errors with mean flow in the laminar flow regime is carried out as a function of the mode index and the transducer diameter/cylinder diameter ratio in the case where no temperature gradients are present in the flowmeter sensor. It is shown that all modes except the fundamental mode overestimate the mean flow by a factor of 33.33% while excitation of the fundamental mode solely give error-free measurements. The immediate consequences are that the flowmeter error decreases as the transducer diameter/cylinder diameter ratio approaches 1 from 0 reflecting the fact that the excitation level of the fundamental mode increases from almost 0 to 1 as this ratio approaches 1 from 0. Secondly, the effect on flowmeter performance due to flow-induced temperature gradients is examined. It is shown that the presence of temperature gradients leads to flowmeter errors at the higher-flow values even in the case where the fundamental mode is the only mode excited. It is also deduced that flowmeter errors in general depend on the distance between transducers A and B whether temperature gradients exist or not. This conclusion is not reflected in the usual definition of flowmeter errors given by the so-called mode-dependent deviation of measurement introduced in earlier works.     

电磁流量计磁场仿真研究

一种集流型电磁流量计广泛的应用于井下流量测量等特殊场合,运用有限元软件ansys对这种集流型电磁流量计建立的磁场仿真模型,并建立了这种集流型电磁流量计中流体中含有导磁率高的颗粒状物体时的磁场仿真模型.     

HL－1装置几种锯齿崩溃机制的层析摄影研究

本文采用二维层析摄影技术研究了ＨＬ－１装置几种锯齿崩溃的机制。在高密度欧姆放电中，观测到在类锯齿崩溃时，对流泡对中心热心的挤压。在纯欧姆放电中，观测到长达４４ｍｓ的大锯齿，在崩溃时出现了强的对流和冷泡对等离子体柱的扰动，并可能发生与其它磁流体不稳定模式的耦合作用。在微波反锯齿振荡和相对应的软Ｘ射线反锯齿振荡的研究中，观察到了软Ｘ射线辐射截面从一个圆变成一个椭圆的现象     

Realization of a multipath ultrasonic gas flowmeter based on transit-time technique

A microcomputer-based ultrasonic gas flowmeter with transit-time method is presented. Modules of the flowmeter are designed systematically, including the acoustic path arrangement, ultrasound emission and reception module, transit-time measurement module, the software and so on. Four 200 kHz transducers forming two acoustic paths are used to send and receive ultrasound simultaneously. The synchronization of the transducers can eliminate the influence caused by the inherent switch time in simple chord flowmeter. The distribution of the acoustic paths on the mechanical apparatus follows the Tailored integration, which could reduce the inherent error by 2–3% compared with the Gaussian integration commonly used in the ultrasonic flowmeter now. This work also develops timing modules to determine the flight time of the acoustic signal. The timing mechanism is different from the traditional method. The timing circuit here adopts high capability chip TDC-GP2, with the typical resolution of 50 ps. The software of Labview is used to receive data from the circuit and calculate the gas flow value. Finally, the two paths flowmeter has been calibrated and validated on the test facilities for air flow in Shaanxi Institute of Measurement & Testing.     

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。     

Viscometric characterization of cobalt nanoparticle-based magnetorheological fluids using genetic algorithms

The rheological flow curves (shear stress vs. shear rate) of a nanoparticle cobalt-based magnetorheological fluid can be modeled using Bingham-plastic and Herschel–Bulkley constitutive models. Steady-state rheological flow curves were measured using a parallel disk rheometer for constant shear rates as a function of applied magnetic field. Genetic algorithms were used to identify constitutive model parameters from the flow curve data.     

Solids flow measurement by correlation methods

The flow velocity of the solids content in pneumatic conveyors is determined from the transit time between two fixed points. Transducers located at these points generate random signals due to the naturally occurring random flow patterns. A special correlator is used for cross-correlating the transducer output signals and for automatically tracking the transit time. The correlating device is simple enough so that a rugged, reliable and yet precise field instrument can be built. Using optical or capacitive transducers, the average velocity of the solid content is measured without obstructing the flow profile. Under certain restrictions, the mean loading and thus the volume flow can be determined from the same sensor signals also. The effect of sensor geometry on bandwidth and the choice of optimal sensor distance is discussed. Optical and capacitive sensors are compared. Illustrative experimental results are given.     

MHD flow study of viscous fluid through a complex wavy curved surface due to biomimetic propulsion under porosity and second-order slip effects

The steady laminar flow of viscous fluid from a curved porous domain under a radial magnetic field is considered. The fluid flow by a curved domain is due to peristaltic waves present at the boundary walls. The whole analysis is based on porosity(Darcy number) effects. Moreover, the effects of second-order slip on the rheology analysis are also discussed. Due to the complex nature of the flow regime, we have governed the rheological equations by using curvilinear coordinates in the fixed frame. The physical influence of magnetic(Hartmann number) and porosity(Darcy number)parameters on the rheological features of peristaltic transportation are argued in detailed(in the wave frame). Additionally, in the current study, the complex wavy pattern on both boundary walls of the channel is used. The whole rheological study is based on ancient, but medically valid,assumptions of creeping phenomena and long wavelength assumptions. Analytical solutions of the governing equations are obtained by using the simple integration technique in Mathematica software 11.0. The core motivation of the present analysis is to perceive the physical influence of embedded parameters, such as the dimensionless radius of the curvature parameter, magnetic parameter, porosity parameter, different amplitude ratios of complex peristaltic waves, first-and second-order slip parameters, on the axial velocity, pressure gradient, local wall shear stress,tangential component of the extra-stress tensor, pumping and trapping phenomena.     

Scanning acoustic Doppler microscopy and scanning acoustic correlation microscopy

Acoustic microscopy with vector contrast at 100 MHz in a fluid with immersed particles is used to detect the flow profile in front of a microscopic orifice. The velocity profile concerning the component in axial direction of the focused beam is derived from the phase contrast. Possibilities to resolve the flow profile also for the components in normal direction with respect to the axis are demonstrated. The methods concerning measurement techniques and data evaluation for scanning acoustic Doppler microscopy are presented. For scanning acoustic correlation microscopy the time dependent phase and amplitude signals resulting from sound waves scattered by the immersed particles (aluminium flakes with a typical diameter of 10 microm) have been analysed by correlation procedures. From the obtained autocorrelation functions the velocity distribution can be derived. Both methods can be applied simultaneously. Data analysis is based on the information contained in the originally obtained images in vector contrast derived from temporal and spatial resolved analogue and digital processing of the acoustic signals.     

Negative differential viscosity in magnetic suspensions

Recent experiments have shown that the dependence of the macroscopic viscous stress on the mean velocity gradient during the Couette flow of concentrated magnetic suspensions in an external magnetic field is N-shaped. As the field strength is decreased, the amplitude of the N-shaped curve decreases and in the absence of the field, the stress monotonically increases with the shear velocity. A model is proposed to explain the shape of the rheological curve. The model assumes that the magnetic field initiates the formation of dense aggregates in a suspension, which connect the opposite walls of a measurement cell. In the Couette flow, the friction of aggregates on the cell walls causes their deviation from the applied magnetic field through an angle determined by the velocity of the relative motion of the walls. For large enough velocities, the aggregates are detached from the wall and are destroyed by viscous forces. It is shown that the friction of aggregates on cell walls results in the initial increasing and decreasing part of the N-shaped rheogram, while the flow after the detachment of aggregates corresponds to its right increasing part.     

Shear Stress in a Couette Flow of Liquid-Particle Suspensions

The mechanisms of momentum transfer and shear stress of liquid-particle suspensions in two-dimensional Couette flow are studied using direct numerical simulation by lattice-Boltzmann techniques. The results obtained display complex flow phenomena that arise from the two-phase nature of the fluid including a nonlinear velocity profile, layering of particles, and apparent slip near the solid walls. The general rheological behaviour of the suspension is dilatant. A detailed study of the various momentum transfer mechanisms that contribute to the total shear stress indicates that the observed shear thickening is related to enhanced relative solid phase stress for increasing shear rates.     

由电磁测量信号估算平衡磁面

在Tokamak等离子体实验结果分析中实际的平衡磁面是极需要的。本文试探从电磁测量信号推得平衡磁面。 一、自由边界平衡程序 借助于自由边界平衡程序计算中等托卡马克装置HT-6M的平衡量。从MHD平衡方程出发,     

多道干涉仪测量托卡马克等离子体电子密度

一、引 言 在目前托卡马克等离子体诊断中,采用垂直多道干涉仪测量等离子体电子密度时,由于等离子体水平位移的影响,使得测量信号在沿大环半径方向的分布是非对称的。这就要求采用非对称的Abel变换来给出等离子体电子密度的空间分布。一种常用的非对称Abel变换是分离变量法,它的基本思想是把测量信号分成对称元和非对称的权函数,对称部分采用标准的Abel变换,变换的结果乘上非对称的权函数。这种方法实际上是假定了等离子体电子密度弦积分值的不对称性与局部的不对称性是相同的;而且对称部分采用标准的Abel变换,如Barr的方法,Bockasten方法等。这些方法是把等离子体看成一个个同心圆,没有考虑到等离子体水平位移引起的弦长变化。本文采用一种新的变换方法,这种方法的特点是考虑到等离子体位移的实际情况。     

Negative viscosity due to magnetic properties of a non-dilute suspension composed of ferromagnetic rod-like particles with magnetic moment normal to the particle axis

The negative viscosity of a colloidal dispersion composed of ferromagnetic rod-like particles, which have a magnetic moment normal to the particle axis, have been investigated. A simple shear flow problem has been treated to clarify the particle orientational distribution and rheological properties of such a semi-dense dispersion, under circumstances of an external magnetic field applied in the direction normal to the shear plane of a simple shear flow. The results obtained here are summarized as follows. For the cases of a very strong magnetic field and magnetic interactions between particles, the magnetic moment of the rod-like particles is significantly restricted in the magnetic field direction, so that the particle approximately aligns in the shear flow direction. Also, the particle can easily rotate around the axis of the cluster almost freely even in a simple shear flow. Characteristic orientational properties of the particle cause negative viscosity, as in the previous study for a dilute dispersion. However, magnetic particle-particle interactions have a function to make such negative viscosity decrease.     

Existence of a Hartmann layer in the peristalsis of Sisko fluid

Analytical solutions for the peristaltic flow of a magneto hydrodynamic(MHD) Sisko fluid in a channel, under the effects of strong and weak magnetic fields, are presented. The governing nonlinear problem, for the strong magnetic field,is solved using the matched asymptotic expansion. The solution for the weak magnetic field is obtained using a regular perturbation method. The main observation is the existence of a Hartman boundary layer for the strong magnetic field at the location of the two plates of the channel. The thickness of the Hartmann boundary layer is determined analytically. The effects of a strong magnetic field and the shear thinning parameter of the Sisko fluid on the velocity profile are presented graphically.     

基于湍流振动的光纤干涉仪流量计的研究

针对石油测井中流量是确定石油生产和传输特性极其重要的参数,提出一种非浸入式光纤干涉仪流量测量方法。在油管外壁紧密缠绕传感光纤,当流体流过管壁时可由湍流产生振动,引起管壁的动态压力变化,导致传感光纤内的传输光相位发生变化, 通过检测光相位的变化就可以获得相应的流量。在实验中找出管壁的振动频率特性,在此频率特性范围内确定出由湍流诱发的管壁振动加速度脉动值的标准方差与平均流量的量化关系,实现了5 m3/h~50 m3/h流量实时在线测量。     

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     

A Numerical Investigation of Nanocomposite of Copper and Titanium Dioxide in Water Based Fluid Influenced by Instigated Magnetic Region

Presence of external electrical field plays a vital role in heat transfer and fluid flow phenomena. Keeping this in view present article is a numerical investigation of stagnation point flow of water based nanoparticles suspended fluid under the influence of induced magnetic field. A detailed comparative analysis has been performed by considering Copper and Titanium dioxide nanoparticles. Utilization of similarity analysis leads to a simplified system of coupled nonlinear differential equations, which has been tackled numerically by means of shooting technique followed by Runge-Kutta of order 5. The solutions are computed correct up to 6 decimal places. Influence of pertinent parameters is examined for fluid flow, induced magnetic field, and temperature profile. One of the key findings includes that magnetic parameter plays a vital role in directing fluid flow and lowering temperature profile. Moreover, it is concluded that Cu-water based nanofluid high thermal conductivity contributes in enhancing heat transfer efficiently.     

A Numerical Investigation of Nanocomposite of Copper and Titanium Dioxide in Water Based Fluid Influenced by Instigated Magnetic Region

Presence of external electrical field plays a vital role in heat transfer and fluid flow phenomena. Keeping this in view present article is a numerical investigation of stagnation point flow of water based nanoparticles suspended fluid under the influence of induced magnetic field. A detailed comparative analysis has been performed by considering Copper and Titanium dioxide nanoparticles. Utilization of similarity analysis leads to a simplified system of coupled nonlinear differential equations, which has been tackled numerically by means of shooting technique followed by Runge-Kutta of order 5. The solutions are computed correct up to 6 decimal places. Influence of pertinent parameters is examined for fluid flow, induced magnetic field, and temperature profile. One of the key findings includes that magnetic parameter plays a vital role in directing fluid flow and lowering temperature profile. Moreover, it is concluded that Cu-water based nanofluid high thermal conductivity contributes in enhancing heat transfer efficiently.