IMEKO Event Proceedings Search

Page 17 of 912 Results 161 - 170 of 9113

Huimin Ma, Ying Xu, Chao Yuan, Tao Li, Cenwei Sun, Yumeng Zhang, Nianrong Wang
A Void Fraction Measurement Method of Gas-water Flow Based on Microwave Method

In the natural gas industry, measuring void fraction with high accuracy is challenging, because the flow pattern of gas-flow is complicated and changeable. This research presents a microwave sensor to measure void fraction of gas-water flow based on the microwave transmission line method. The sensor contains horizontal and vertical electrodes resulting in a spatial orthogonal transmission line combination structure, so that the gas-water flow regime can be detected and its influence on the measurement can be accounted for. The electromagnetic fields inside the sensor for stratified and annular distribution structure are simulated and analyzed using COMSOL software. Furthermore, the variation characteristics of the horizontal and vertical electrode phase outputs of the stratified distribution structure are investigated by static experiments. Finally, flow experiments covering stratified, wavy, slug, annular gas-water flow regimes, indicates that the void fraction are positive correlated to the sensor outputs and can be predict by the sensor.

Cenwei Sun, Ying Xu, Chao yuan, Tao Li, Huimin Ma, Yumeng Zhang, Xili Ba
Experimental Investigation on Measurement Characteristics of WMS for Gas-Liquid Slug Flow

With the development of the gas-liquid two phase flow dynamics theory and the continuous improvement of two phase flowrate measurement requirements, the importance of slug flow research has become increasingly prominent. The wire mesh sensor (WMS), which consists of the perpendicular "cross-point" between the transmitting wires and receiving wires, forms a particular "hard field" measurement mode. This paper aims toinvestigate the measurement characteristics and accuracy of a 16×16-electrode conductivity WMS with a spatial resolution of 3.125 mm for gas-liquid two phase slug flow by means of flow experiments. Experimentswere performed in a 50 mm horizontal pipe with air and water as the working medium at atmospheric conditions, meanwhile, the time series data were collected by WMS. Comparing the cross sectional, a good correspondence can be found in the cross sectional direction between axial reconstructed images of fluid distribution and averaged void fraction time series. The WMS can realize the quantitative measurement of local void fraction and the qualitative spatial phase reconstruction of fluid distribution. Furthermore, distribution characteristics of the cross sectional averaged void fraction time series of gas-liquid two phase slug flow were analyzed. We found when superficial gas velocity is less than 3 m/s, the gas phase mainly exists in the form of elongate gas slug. When superficial gas velocity is around 5 m/s, it appears as typical bullet-shape gas slug. As superficial gas velocity increases to 10 m/s, the liquid slug becomes blurred and the gas phase almost penetrates through the liquid slug structures. In addition, a Probability Density Function (PDF) is generated from the instantaneous cross sectional averaged void fraction data for different flow regime conditions. The results show that the PDFs for lower superficial gas velocity case (3 m/s), two peaks in the void fraction signal are observed. Nevertheless, with an increase in superficial gas velocity, it is seen that the peak in the low void fraction region, which corresponds to the liquid slug structures, becomes much smaller even disappears.

Weijie Chen, Haohao Xu, Chengxu Tu, Xianfeng Li, Wenkun Gao, Jianli Zhang, Xiang Li, Fubing Bao
Optimization of electrode and contraction section of 90° bent electromagnetic flowmeter using CFD simulation

Currently, electromagnetic flowmeters must typically be inserted into a straight pipe, which usually requires a larger installation space. To improve installation adaptability, a novel 90° bent electromagnetic flowmeter is proposed. As the measurement signal of the electromagnetic flowmeter is closely related to the flow state of its internal fluid, a large-eddy simulation (LES) was used to study the influence of the shape of the electrode and the contraction section of the flowmeter on the flow characteristics inside the flowmeter to reveal the relationship between them along with the measurement accuracy. A comparison between the numerical results and the experimental results was also performed. The velocity fluctuations of the monitoring points around the cone and flat electrodes were compared, and it was found that the overall measurement error of the cone electrodes was smaller than that of the flat electrodes. The experimental results showed that the pulsation of the voltage signal measured from the cone electrode is smaller than that of the flat electrode. In addition, the absolute value of the error in the small flowrate is much smaller than that of the flat electrode. Consequently, the measurement performance of the cone electrode is better. In addition, the largest velocity fluctuation occurred between the electrode wall and tube wall, indicating that installing the coil should avoid exciting strong magnetic fields here.

S. Knotek, J. Geršl
Modelling of uncertainties of an emission concentration measurement in stacks

This contribution describes a research of measurement uncertainty of industrial emissions flowing through vertical stacks and its dependence on different geometrical configurations and physical conditions. Since the legislative requirements for emission limits from industrial processes are decreasing, the higher measurement accuracy is becoming more important and new uncertainty standards needs to be implemented. Thiscontribution is a part of the research project 18NRM04 Heroes under European Metrology Program for Innovation and Research (EMPIR). CFD modelling is used to analyse particle distributions in stacks with three different geometries of a supply pipe, different size of the particles and several concentrations. Vertical stack with a circular cross section of a diameter of 0.75 m is considered with the supply pipe containing none, one or two bends. The number of particles entering the stack defines the initial volumetric concentration from 0.1 to 10 mg/m³ with the particle size from 10 to 50 µm.Concentration fields in several cross-sections were compared and the particle distributions were analysed as functions of the physical conditions and the chosen geometry of the stack. The results show not very high sensitivity of the concentration profiles on the initial concentrations. On the other hand, significant changes of the concentration fields are observed when the stack geometry or the particle diameter is changed. This should be taken into account in the iso-kinetic sampling practise where the overall concentrations are calculated from measurements in several points.

Zhao Zhiyue, Wang Longlong, Li Xiaoting, Wang Jing, Guo Liqiang
Void fraction measurement based on electromagnetic wave sensor

Gas-liquid two-phase flow is an unavoidable energy flow phenomenon in industries, and void fraction measurement is a crucial challenge in the two-phase flow. In the study, the coaxial line phase sensor is designed base on electromagnetic wave transmission principle, by which void fraction of the slug and stratified flow was acquired. The void fraction measured by new coaxial has a well time-domain and Probability Density Functions (PDF) distribution characteristics, four typical models with different physical backgrounds were selected to evaluate the measured values of the sensors. The mean absolute errors (MAPE) were 7.85 %, 24.41 %, 7.22 %, and 15.44 % for slug flow, and 12.31 %, 6.46 %, 12.68 %, and 2.95 % for stratified flow. The results indicated that the coaxial line phase sensor has well measurement accuracy and not limited by the flow regime.

Ning Zhao, Tian Zhang, Xianle Zang, Long Xu, Jing Wang
Effect of System Pressure on Liquid Film Behavior in Horizontal Annular Flow

The measurement of liquid film parameters is of great significance in the momentum transfer and heat transfer characteristics of gas-liquid two phase in annular flow. The liquid film at the bottom of the horizontal annular flow is the thickest and produces the greatest influence on the nature of the annular flow. In large diameter horizontal pipes, the effect of pressure on liquid film behavior lacks systematic discussion. Therefore, a dynamic measurement system for annular flow liquid film was designed based on near-infrared(NIR) sensing technology to complete the measurement of annular flow liquid film thickness data under five pressures. The average liquid film thickness at the bottom is obtained by variational modal decomposition(VMD) of the time series signal, and the wave velocity parameter is obtained by mutual correlation velocimetry. The article initially discusses the effect of pressure on the average thickness of the bottom liquid film as well as the interfacial wave velocity.

Yumin ZHAO, Xu WANG, Liang PENG, Tianyu WANG
Research on the traceability verification technology of quantity value of standard water flow facility based on mobile comparison method

Standard water flow facility (hereinafter referred to as the standard facility) is used for the calibration of cold and hot water flow meters. According to JJF1001-2011 “General Metrology Terms and Definitions” the standard facility needs to be verified that the quantity value stays in the original status in order to ensure the quantity value can meet the requirements during operation. And the verification will help to identify the inaccuracy, to shorten the traceability time after that, and to minimize the test costs and quality risk as far as possible.This project studies a technical method for verifying the traceability of quantity value of standard water flow facility based on mobile comparison method. According to JJG 164-2000 "Standard facilities for Liquid Flowrate”, the total uncertainty of the standard facility for cold and hot water flowrate is determined by calibrating the timer, commutator, scale, calibrated measuring volumetric tank, etc. and the traceability of the quantity value of the facility is completed. The core of this study is how to verify the overall impact of the facility in use due to piping system, hydraulic stability, gas tightness, flow fluctuations, etc. on its reproducible quantity values.

WANG Kexu, CHEN Xiyu
Numerical simulation-based experimental study on theeffect of different disturbed flow components on ultrasonic flowmeter metering performance

Ultrasonic flowmeter is a velocity flowmeter, and its measurement accuracy is greatly affected by the flowfield in the pipeline. In the actual use process, due to the installation conditions are not ideal, the formation ofvortex flow, pulsating flow, asymmetric flow and other non-ideal flow field in the pipe, which in turn affects the accuracy of ultrasonic flowmeter. This study is based on CFD numerical simulation technology, 90° elbow, reducer, upstream and downstream flange diameter difference of one level and other typical disturbanceelements on the impact of the flow field in the pipe, simulate the flow field of the gas in the closed pipe after the disturbance elements, and calculate the resulting error, found that the impact of each disturbance element on the ultrasonic flowmeter measurement error increases with the increase in operating flow. For 90° elbow, the upstream and downstream flange diameter differ by one level, we use these two installation conditions to carry out real flow test, through the test data and simulation results for comparison and analysis, the results are consistent. At the same time, the use of experimental data on the simulation model correction, can guide the construction and transformation of ultrasonic flowmeter metering process, improve the accuracy of the measurement results, and effectively maintain the fairness of the trade handover.

PEI Quanbin, Xu Ming, QING Qing, YAN Haiming, WANG Kexu
Discussion on measurement and evaluation method ofnatural gas flow computer

As an important measuring instrument and basis for the handover of natural gas measurement trade, it is necessary to formulate requirements and test standards for evaluating its structure, performance, safety and consistency. The computer evaluation and detection software of natural gas flow is developed, which realizes the functions of data acquisition and evaluation, flow calculation and verification, physical parameter evaluation and environmental impact factor evaluation. The design, software and hardware configuration of natural gas flow computer evaluation and detection system are completed, and the flow is established.Thecomputer evaluation and detection standard device forms a natural gas flow computer evaluation anddetection system, realizes the evaluation of the accuracy of the flow computer and its supporting sensors, and carries out laboratory and field application test experiments on the evaluation and detection system.

HOU Yang, CHEN Zhengwen
Study on the effect of pressure on gas ultrasonic flowmeter

With the ultrasonic flowmeter (Ultrasonic Flowmeter) in the natural gas metering is widely used, ultrasonic flowmeter accuracy is increasingly concerned. however, by the limitations of the calibration operation conditions, there aredifferences between the calibration operation conditions and actual operation conditions , and operation conditions on theimpact of ultrasonic flowmeter metering lack of systematic research, Wuhan branch station established a mobile natural gas metering standard device can be carried out in different pressure conditions of the gas transmission station calibration services.In this paper, we study the calibration tests carried out by the mobile natural gas metering standard device at different pressures, and through analyzing and integrating data, we derive the metering deviation caused by ultrasonic flowmeter under different working conditions, establish the mathematical model of Reynolds number error correction toguide the use of ultrasonic flowmeter, and eliminate the deviation introduced by the different operation conditions of calibration and use, improve the accuracy of trade measurement, while the research results can be the technical support for the revision of relevant standards and norms.

Page 17 of 912 Results 161 - 170 of 9113