The turbine meter applied to void fraction determination in two-phase flow

A new approach to analysing the pulse output information from a standard turbine meter in two-phase liquid/gas flows is presented. After suitable calibration, the meter will register the presence of gas, with an accurate indication of void fraction up to 20%, and provide a measure of the liquid flowrate. The single-phase performance of the meter remains unaffected.     

A two-phase flow meter for determining water and solids volumetric flow rates in stratified,inclined solids-in-water flows

This paper describes the design and implementation of a two-phase flow meter which can be used in solids-in-water two phase pipe flows to measure the in-situ volume fraction distributions of both phases, the velocity profiles of both phases and the volumetric flow rates for both phases. The system contains an Impedance Cross Correlation (ICC) device which is used in conjunction with an Electromagnetic Velocity Profiler (EVP). Experimental results were obtained for the water and solids velocity and volume fraction profiles in upward inclined flow at 30° to the vertical, in which highly non-uniform velocity and volume fraction profiles occur.     

A new method of two-phase flow measurement by orifice plate differential pressure noise

The mechanism of differential pressure noise of orifices in two-phase flow has been investigated and a theoretical model has been developed for measurement of the double parameters, i.e. mass flow rate as well as phase fraction (steam quality). The model has been proved in a set of orifice experiments in a two-phase flow system at a pressure range of 5.8–12.1 MPa and steam quality of 0.05–0.95, and a practical model has been fitted. The r.m.s. errors of mass flow rate and steam quality estimated by the model are 9.0 and 6.5%, respectively. The results of the studies create a method to measure double parameters of two-phase flow at once using only a single orifice.     

纵向多极阵列电导式两相流测量系统研究

针对优化后的纵向多极阵列电导式传感器,本文构建了基于DSP技术的两相流测量系统.整个测量系统包括激励信号发生电路、信号调理电路和基于DSP技术的数据采集卡及上位机软件,其中两相流流速测量采用基于DSP技术的频域直接相关方法来实现,数据采集卡由MSP430F149单片机和DSP5402构成,由单片机负责数据采集,DSP负责频域内相关运算,采用双口RAM实现两种处理器间数据通信与共享,单片机通过串口与上位PC机通信以实现数据的传输和采集系统设置.该测量系统在气水两相流流动环中取得了满意的动态试验效果.     

层析成像在冰水两相流参数测量中的应用

提出将电阻层析成像(ERT)技术应用于冰水两相流相含率、相分布等特征参数的测量,并设计了ERT测量系统,研究了基于图像的相含率计算方法.阐述了ERT系统的工作原理,提出了16电极ERT系统的设计方案.介绍了线性反投影图像重构算法(LBP);并结合数字图像处理技术,提出了截面相含率的计算方法.最后,通过一组实验验证了电阻层析成像技术应用于冰水两相流检测的可行性.实验结果表明:通过ERT系统可以获得管道内冰柱在水中的位置以及实时运动结果,直观反映冰水两相介质的相分布;另外,通过ERT系统可以近似地真实反映冰柱的相对大小,两次截面相含率测量误差分别为6％与2.8％.研究表明,ERT技术可以实现冰水两相流的实时在线监测,而且具有良好的测量准确度.     

Gas/liquid two-phase flow regime identification by ultrasonic tomography

A gas/liquid two-phase flow is considered as a strongly inhomogeneous medium with respect to high contrast in acoustic impedance distribution. Based upon a binary logic operation and a method of “time-of-propagation along straight path”, an ultrasonic facility for tomographic imaging of gas/liquid two-phase flow was developed. In this paper the principle and construction of this facility are briefly introduced. Emphasis is placed on the evaluation of its performance in flow regime identification and cross-sectional void fraction measurement. Several flow pattern models were used and the corresponding monitoring results given. Finally, limitations and possible future improvements of the system are discussed.     

Micro wire-mesh sensor for two-phase flow measurement in a rectangular narrow channel

A micro wire-mesh sensor (μWMS) based on an electrical conductivity measurement between electrodes installed on the walls has been developed for gas–liquid two-phase flow measurements in a narrow rectangular channel. This measuring method applies a principle of conventional wire-mesh tomography, which can measure the instantaneous void fraction distributions in the cross-section of the relatively large flow channel. In two-phase flow measurement using μWMS the void fraction distributions in the narrow channel were obtained by the measured conductivities between electrodes arranged on each wall. Therefore, the gas phase structures and the bubble behaviors can be investigated in the flow channel with narrow gap. In the present paper, a μWMS for the air–water flow between parallel flat plates with a gap of 3 mm was developed and simultaneous measurements with a high speed video camera were conducted to compare the measured results in bubbly flow.     

相关法测两相流的研究

本文探讨一种以单片机为核心的两相流测量用软件相关仪中自动跟踪峰值,以确定流体渡越时间的新方法。将该方法与快速相关计算法相结合,可进行实时相关估计,同时可以保证峰值位置确定的可靠性。     

气液两相流中上升气泡体积的计算方法

通过高速摄像机拍摄气液两相流中上升气泡的运动过程,分别记录不同直径的气孔所产生的单个气泡上升过程的连续图像,结合数字图像处理技术,提取了气泡的面积、当量直径、几何中心、速度、加速度等特征参数.并在此基础上,应用两种计算气泡体积的方法:几何方法和受力分析法,实现了气泡体积的初步计算.几何方法计算气泡体积是根据图像中气泡的形状构造一个与气泡体积相当的椭球体,进而计算椭球体的体积;而受力分析的方法则是通过分析气泡在垂直方向上的受力情况,根据牛顿第二定律推导出气泡体积的计算公式.并对两种方法计算出的气泡体积值进行分析对比,阐明了这两种方法适用情况,计算出单个气泡上升情况下的气相体积含气率.     

油水两相流中2种含水率计算模型比较

油水两相流广泛存在于石油开采、储运、化工、能源等工业领域。含水率是油水两相流系统的重要参数之一,含水率的准确测量不仅与采用的测量方法有关,而且还与计算模型有很大关系。结合电导式测量方法建立了电阻-电容并联网络含水率计算模型,并在3种流型下与Maxwell含水率模型进行了仿真和实验对比。结果表明,建立的并联电阻-电容网络含水率模型,在泡状流下与Maxwell含水率计算模型的误差基本相同,而在环状流、分层流下,测试误差均小于Maxwell含水率计算模型的误差,具有更高的测试精度,可适用于环状流、分层流、泡状流等流型。     

Calculation and measurement of the magnetic field in a large diameter electromagnetic flow meter

An idealized magnet model previously used in a simple coil configuration is applied to a more complicated engineering design problem, where an electromagnetic flow meter in diameter of 500 mm is used with five pairs of coils. The numerical results are compared with measurement data. The difference between theory and experiment and the possible causes of errors are discussed. It is shown that the idealized magnet model is practical for the design and the analysis of the flow meter. The work also shows that the traditional uniform field design based on two dimensional (2D) analysis is not suitable for this kind of flow meter. Thus nonuniform field and 3D analysis is needed.     

Simple installation for measurement of two-phase gas–liquid flow by means of conventional single-phase flowmeters

The paper describes a method of measuring the flow rate of the components of a two-phase gas–liquid mixture. The proposed method ensures the separation of two phases using a rather simple modification of pipeline configuration than using separating vessels to achieve this aim. The two components can then be measured using conventional single-phase flowmeters. The errors of the separating and metering installation are about ±(3–4)% in the flow rate range 3:1.     

Remote measurement of liquid flow using turbine and fiber optic techniques

This paper deals with the development of a low cost, intelligent liquid flow measuring system, based on fiber optic technology. Fiber optic sensing as well as communication is used to measure flow, at a distance, using basic turbine flow meter. The blades of the turbine meter are used to modulate the light falling on it. The frequency of the pulses generated depends on the number of blades and is measured by the microcontroller and displayed on the hyper terminal. With proper calibration, relationship between output frequency and flow rate is appreciably linear and accuracy is ±0.4%.     

电容式气固两相流浓度测量系统

本文介绍一种电容式气固两相流浓度测量系统,给出了具体的测量电极和测量电路。并采用所设计的电容式浓度测量系统在自行搭建的气力输粉系统上以面粉为媒质、在水平管道上对稀相气固两相流浓度进行了在线测量,获得了5×10^-5%体积百分比的面粉浓度分辨率。应用该系统对锅炉气力输粉管道中的气固两相流浓度进行实时在线检测与控制,对确保燃烧过程稳定,节能降耗和减少污染排放具有重大意义。     

差压式流量传感器测量一般气体流量时的温度压力补偿方法

简要介绍使用差压式流量传感器进行一般气体流量测量时的温压补偿方法;指出了差压方式流量传感器测量一般气体的通用流量温压补偿公式,并写出了公式的推导过程;与线性流量传感器温压补偿方法进行对比,强调指出了采用差压式流量传感器时进行温压补偿的注意要点.对公用工程中的一般气体的流量计量工作有一定的指导作用.     

气固两相流固相浓度电容式传感器优化设计

本文建立了一种螺旋式电容传感器的数学模型,并基于该模型对传感器结构进行了优化设计。优化后的结构可以产生较均匀的灵敏场分布,实测结果表明,优化后的传感器电容值与固相浓度具有良好的线性关系,测量点的线性相对偏差小于0.8%,适用于气固两相流固相浓度的测量。     

新型正弦行星齿轮流量计的三维实现及流量脉动分析

根据正弦函数曲线类比推导出了正弦齿轮的直角坐标方程,利用CAXA电子图板2007的公式曲线功能和Pro/E软件建立了正弦齿轮和流量计的三维模型。为了探究正弦行星齿轮流量计的测量精确性,进行了流量脉动分析,分析结果表明:该流量计比渐开线齿轮流量计具有更小的流量脉动率。     

核反应堆堆芯冷却剂流量测量用涡轮流量计的研制及应用

为适应核反应堆堆芯冷却剂流量测量的需要,开发研制了新型低速涡轮流量变送器,按流量信号输出不同,分别为磁感应模拟信号输出和数字开关量输出低速涡轮流量变送器。实际标定和应用表明,低速涡轮流量变送器的精度和重复性是好的,相对误差的均方根为1．0％,使用寿命长,阻力小,线性范围宽。     

Branching of two-phase flow from a vertical header to horizontal parallel channels

The objective of the present experimental work is to investigate the two-phase flow distribution from a vertical main to parallel horizontal branches. Both the main and the branches have rectangular cross-sections simulating the header and the channels of the compact heat exchangers for air-conditioning systems. The cross section of the main is 8 mm × 8 mm while that of the parallel branches is 8 mm × 1 mm. Here, the second (downstream) junction was taken as the reference. The effect of the distance between the branches was mainly examined by changing it from 9 mm to 49 mm for the given flow conditions at the inlet of the downstream junction. Air and water were used as the test fluids. The superficial velocity ranges of air and water at the test section inlet were 13.2–21.4 m/s and 0.08–0.28 m/s, respectively. When the branch spacing becomes smaller, the fraction of liquid separation through the downstream branch decreases. The trend remains the same over the entire range of the present experiment, i.e., for different values of quality and the mass flow rate at the inlet of the downstream junction. Based on the correlation for single T-junctions, a modified correlation was proposed to take into account the effect of the branch distance in predicting the fraction of liquid separation. The correlation represents the experimental results within the accuracy of ±15 %. This paper was recommended for publication in revised form by Associate Editor Kyung-Soo Yang Jun Kyoung Lee received his B.S. degree in Mechanical Engineering from Busan National University in 1999. He then received his M.S. and Ph.D. degrees from KAIST in 2001 and 2005, respectively. Dr. Lee is currently a Professor at the School of Mechanical Engineering and Automation at Kyungnam University in Masan, Korea. Dr. Lee’s research interests are in the area of two-phase flow and heat transfer, micro-fluidics, cryogenic devices for superconductivity, thermal management systems for automobiles.     

新型脉冲式热流计分析研究

现有热流计都需要流量计来计量流量.流量计很容易损坏并产生计量误差.为了解决这一问题,依据能量守恒提出了一种新型热量计,并对该装置的测量原理进行了理论分析和数值模拟,从而实现了只测量温差的情况下测出用户消耗的热量,摆脱了流量对测量结果的影响,从模拟和理论分析证明本方法能够较准确的计量热量值.