科氏流量计应用于气液两相流测量的实验研究

以空气-水为介质,对科氏流量计应用于气液两相流双参数测量进行了实验研究.实验过程中保持液相流量一定,通过加入不同体积分数的空气来分析含气率对科氏流量计测量精度的影响,采用Weisman垂直上升管气液两相流流型图与实验数据进行了比较.结合实验结果,初步归纳出含气量、流型和科氏流量计测量精度之间的关系,总结出液相中含气影响科氏流量计测量精度的主要因素及其影响规律,为进一步研究科氏流量计气液两相流测量误差修正提供了一种技术方法.     

垂直管道中气液两相流参数的图像检测方法

介绍了一种利用数字图像处理技术检测垂直管道中泡状流参数的新方法，其中利用差影算法来消除背景噪声，利用迭代法对图像进行最佳阈值分割。实验结果表明，该方法可以在线测量气液两相流中的气泡尺寸及截面含气率。     

气液两相流泵的研究进展

介绍了气液两相流动的主要计算模型,总结了现有两相流泵的特点,对有关两相流泵的流场分析,性能预测,试验研究及水力设计等方面的现有成果分别进行了综述,对应进一步深入研究的问题及研究中应遵循的一些原则进行了初步探讨。     

基于气液两相流模型的电解加工多场耦合仿真

针对电解加工产生的气泡影响加工精度的问题,引入Euler Euler双流体模型对电解加工中气液两相流场进行描述,并耦合电场和温度场相关模型,分析了工具阴极、工件阳极表面气泡率、温度、电导率和电流密度的分布规律;通过调整加工电压、入口压力和出口压力,对工件阳极表面气泡率和电流密度分布进行仿真优化。仿真结果表明：在流速相同的条件下,减小加工电压、增加出口压力能够改善电导率分布,使阳极表面电流密度分布更加均匀。实验结果表明：仿真得到的阳极表面电流密度分布与工件轮廓高度误差分布吻合;采用优化后参数加工出的工件轮廓精度得到提高。     

低压管路内气液两相流数值模拟及试验分析

以低压管路内气泡的运动状态为研究对象,建立了气泡在管路内运动的模型。对气泡分别在45°倾斜向下、水平、垂直向上3种管路中匀速运动进行分析。通过理论分析及模型仿真发现,在45°倾斜向下的管路中,气泡在匀速运动时只能聚集于靠近管壁的环状空间上方;在水平管道中,气泡存在于管道上部,在垂直向上的管路中,气泡只沿管道中心向上运动。搭建可视化试验台,观察气泡在不同管路中的运动状态,发现仿真结果与试验观察现象吻合。同时,通过分析当管道含气率在1.18%时,气泡在管路中的聚集和变形情况,发现管道内的压力波动与油液流速和管道的曲率半径相关。     

离心式气液两相流泵的试验研究

通过对QYS100－20型离心式气液两相流泵的试验，分析和研究了泵的性能，获得了研制高含气量的气液两相流泵的宝贵经验。     

基于同轴相位传感器气液两相流截面含气率测量方法

利用电磁波技术,设计了基于电磁波原理的同轴线相位传感器,提出了含气率测量的相移原理,给出了含气率与相位差的函数关系,并在内径50.0 mm的不锈钢测量管段进行了48个实验点的垂直管气液两相流截面含气率测量实验。实验结果表明：通过对3种现有模型的测量结果进行分析比较,Lockhart-Martinelli模型的测量结果与预测结果的平均绝对误差为18.32%,相较于其他2种模型更适用于弹状流的流型,该测量方法和测量模型具有一定的有效性和准确性。     

气液两相流系统的小波软测量技术

提出了一种基于小波分析技术的气液两相流流型判别软测量模型.气液两相流中简单、易测而且可靠的差压波动信号作为软测量模型中的辅助变量,气液两相流的流型作为模型中的主导变量,利用小波分析技术建立了主导变量和辅助变量之间的数学关系,进而通过测量差压波动信号可以对气液两相流的流型进行判别.实验证明所建立的软测量模型是有效的.     

光纤传感技术测量气液两流持气率研究

文中提出了一种新气液两相流体参数测试方法。传感机理为弯典光纤的传输光功率随外界介质折射率而变化,在分析光纤弯曲波导传光能损耗与弯曲半径,等因素关系的基础上,提出了一种 光纤传感器系统,并将其应用于气液两相流体持气率测试中,进行了初步研究和探讨。     

气液两相流液相体积含量的精确测量

两相流多变的流型导致电容传感器测量组分体积含量时精度较低。仿真试验结果显示,管道气—油两相流含油率的测量误差高达１５％ 以上。利用层析成象电容传感器阵列获取的管道内部两相流分布情况的投影值,可确定对组分体积含量的修正方法,使误差显著降低。本文分析了流型对测量的影响,导出了修正公式,介绍两种修正方法及仿真修正结果。     

气液混输漩涡泵内部气相分布与性能预测研究

为研究漩涡泵的气液混输性能,采用Fluent计算软件对泵内部气液两相流场进行了数值模拟。模拟结果初步揭示了该泵内气液两相流动特征,由此可知泵流道内的气泡主要集中在叶片压力面根部,气泡聚集程度随含气率的增加而增加。泵性能预测曲线与试验曲线较为吻合,说明了所采用的计算模型是基本可行的。     

A study on gas-liquid two-phase flow metering: Identification of flow dynamics that influence the performance of CMFs

Metering on gas-liquid two-phase flow is challenging even though the Coriolis Mass Flowmeters (CMFs) outperform most of other flow measurement technologies owing to their ability to directly measure the fluid mass flowrates. This is due to complexity of the dynamics of the gas-liquid two-phase flow. Thus, Coriolis Mass Flowmeters have been undergoing modifications to improve their accuracy on measuring complex flows but still the variation of error due to bubble entrainment and the mechanisms responsible of these errors remain less understood. Hence there is a strong need to conduct further characterization on the performance of CMFs on measurement on gas-liquid two-phase flow.This study aims to analyse the performance of a U-shape CMF on metering gas-liquid two-phase flow via both CFD simulation and experimental measurements. For simulation, a two-way coupling of Fluid-Structure Interaction was used to minimize the inaccuracy in simulation results. It has the ability to count on influences of fluid forces on the tube deformation and the reaction of the oscillating-fluid conveying tube to the overall dynamics of the system.The results show that at low nominal flowrates (NFRs), the flow/phases separation occurs and dominates the previously identified factors of errors such as bubble theory effect/friction damping effect and cause positive errors. The error associated with bubble theory effect or friction damping is negative i.e. the CMFs under-estimate the mass flowrates of the mixture. Our study, however, found negative errors only at high nominal mass flowrates. In addition, it is to be noted also that even though the theoretically predicted error due to mixture compressibility in some literatures could be positive, it is important to carry out further experimental and computational studies for analysis. In this study, it is observed that the oscillations of separated fluid phases amplify the amplitude of tube oscillation and hence leading to distortion of the displacements of the CMF tube. This could lead to up to 14.9% of positive error in CMFs’ measurements at the low nominal mass flowrates.It is believed that these results can serve as baselines for future studies on corrections and compensations of CMFs’ errors on measurement on gas entraining fluid flow encountered in fuel bunkering and LNG metering processes.     

Mass flow rate measurement of gas-liquid two-phase flow using acoustic-optical-Venturi mutisensors

The measurement of multiphase flow parameters is essential for the online monitoring of industrial production and energy metering. In this paper, a multi-sensor experimental measurement device is designed based on NIR, acoustic emission sensors, and throated Venturi. The measurement information is decomposed using modal decomposition, and the characteristic variables of the gas volume fraction are extracted by flow noise decoupling and light attenuation analysis. A new gas volume fraction model is proposed based on Gradient Boosting Decision Tree (GBDT) through feature-level fusion, and the Mean Absolute Percentage Error (MAPE) of the gas volume fraction prediction models is within 4% for the three flow patterns. A new flow rate model is established based on the Homogeneous and Collins models. Laboratory results indicate that the MAPE of the flow rate model is 1.56%, and 98.61% relative deviations are within ±20% error band. The study provides a new method for online measurement of multiphase fluid motion and a theoretical basis for sensing mechanism and measurement of multiphase flow.     

液固两相流压降规律及超声法压降测量

液固两相流广泛存在于能源动力、石油化工等工业过程,两相流压降作为重要的流动参数,有助于流动建模及流态分析。建立液固两相压降测量模型,提出了一种结合超声多普勒及超声透射衰减的液固两相超声压降测量方法。搭建液固两相流动实验平台,对两相压降规律进行研究。两相混合流速和固相体积分数升高时,液固两相压降均逐渐增加。在固相体积分数为0.28%～1.37%,两相混合流速为0.9～1.65 m/s时,根据液固两相压降测量模型及Churchill模型的超声法得到的两相压降与差压传感器测量的压降平均相对误差为4.93%和5.10%,验证了测量模型的准确性。针对非均匀分布的两相流态进行压降测量,进一步拓展了压降测量模型的应用范围。本研究工作为非侵入超声法测量液固两相压降提供了方法基础。     

Development of a turbine meter for two-phase flow measurement in vertical pipes

The performance of a turbine meter in two-phase (water/air) flow in a vertical pipe is assessed. If the single phase (water) meter factor is used in two-phase flow, the total (water and air) flowrate is found to be underpredicted. The error can be as much as 12.5% at a void fraction of 25%. A technique for using measurements of the fluctuations in the turbine meter rotor velocity to determine void fraction (= air flowrate/total flowrate) is described. A single meter is then used to measure, using this technique, both the water flowrate to an accuracy of ± 2% and void fraction to an accuracy of ±0.02.     

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.     

基于压差波动法的气液两相涡街功率谱特性分析

气液两相流体横向绕过圆柱体流动时，在圆柱体后部会产生漩涡交替脱落现象，导致圆柱体两侧压差波动，测量该压差波动信号并通过DFT变换可以得到功率谱。采用此方法对矩形通道内垂直上升气液两相绕流的涡街特性进行实验研究，实验中雷诺数范围为1．1×10^4-2．8×10^4，截面含气率范围为0～0．15。实验结果表明：在实验条件范围内，含气率d〈0．1时差压波动信号的功率谱图存在峰值，并且随着含气率的增加峰值降低，当含气率α≥0．1时，功率谱图上已经没有明显的峰值，表现为随机脉动；雷诺数对功率谱特性影响小。     

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.     

Extracting reference voltages from measurement voltages for oil-water two-phase flow measurement of electrical impedance tomography

To apply electrical impedance tomography (EIT) for heterogeneous two-phase flow measurement, reference voltages have to be measured, which requires the entire pipeline filled with a homogeneous medium. Such process is often time-consuming, costly and infeasible in some cases. Reference voltages acquired initially could not be used later, because of electrical conductivity change of two-phase flow caused by temperature change or chemical reaction. It will be ideal if reference voltages could be extracted from measurement voltages. In this paper, a novel multiple measurements (MMs) method is proposed by data fitting and empirical formula to establish the mapping model from measurement voltages to reference voltages, and the effectiveness of the method is proved by the oil-water two-phase flow experiment. Compared with the measurement-scale feature (MSF) and best homogeneous (BH) methods, the proposed MMs method achieves 6.38% average relative error (RE) and 4.96% average volume fraction relative error (VFRE) in the test set. The work enables the accurate estimation of the reference voltage and thus the accurate measurement of the volume fraction of oil-water two-phase flows, which will broaden the application of EIT in the field of two-phase flow measurement.     

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.