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Page 16 of 912 Results 151 - 160 of 9113

Zheng Zhang, Miao Miao, Wenjia Li
Study on the influence of installation angle on pitot tube in wind tunnel

Pitot tube is a standard instrument commonly used in wind speed measurement, which generally needs to be used in conjunction with wind tunnel. On the premise that the pitot tube coefficient is determined and the performance of other related supporting equipment (digital pressure gauge, temperature and humidity sensor) is stable, it is found that the horizontal installation angle of pitot tube in the wind tunnel will have a significant impact on the measurement of wind speed. This paper designs an experimental method for this kind of phenomenon, summarizes the experimental data, and analyzes the possible impact of this kind of phenomenon on wind speed traceability, in order to improve the accuracy and effectiveness of pitot tube wind speed measurement.

A. Iwai, T. Funaki
Uncertainty Evaluation of Fluid Density at High Air Speed Standard in NMIJ

The National Metrology Institute of Japan (NMIJ) maintains high air speed standard and its calibration facility is capable of a relative expanded uncertainty (k = 2) of 0.63 % in the air speed range 40 m/s to 90 m/s. The model equation for measurement uncertainty in the high air speed calibration wind tunnel, which is the working standard, employs a method that cancels out the density term of the fluid. This is due to the fact that the density on the wind tunnel and DUT side is considered to be the same, i.e., the air speed values on the wind tunnel and DUT side are based on the same Bernoulli's principle. Therefore, the calibration environment of this standard is registered in the KCDB (CIPM MRA database) as ambient, which is independent of temperature and pressure changes throughout the year. However, there is a need to develop a calibration method for anemometers which are not based on Bernoulli's principle, as calibration targets. In this presentation, the reproducibility of air speed values in the wind tunnel is experimentally discussed, especially in the calibration environment, as the density of air changes throughout the year. In addition, the relative uncertainty of the density due to the difference of air density derivation formulas will be compared. Finally, the measurement uncertainty with the corrective coefficient of the anemometer under calibration due to the density change of air will be discussed.

Yang You-Tao, Chen Hai-Lin, Liu Kai
Research on Flow sensor of Ultrasonic Gas Meter

By reviewing the development of gas meter, the application prospect of ultrasonic gas meter is forecasted, the key technology and research and development difficulties of ultrasonic flow sensor, as well as the key application technology problems to be solved are discussed.The paper focuses on the design and selection of timing scheme of flow sensor, design of flow field characteristics of flow channel of flow sensor, electro-acoustic performance of flow sensor, linearity and repeatability of gas flow sensor. Through the exchange of theoretical research and practical application experience, the promotion of ultrasonic sensing technology, so as to promote the batch production and application of ultrasonic gas meters.

Nguyen Ngoc Hai, Nguyen Xuan Thai, Phan Lac Tuan, Duong Hong Son
Evaluation results of the new standard gas flow system at VMI: Piston prover system

Currently many National Metrology Institute (NMIs) as well as advanced calibration laboratories are using piston gas flow standards with mercury sealing method for gas flow calibration in the low pressure range. The flow in the small range is about cc/min. In this work, the low pressure gas flow calibration system at VMI is presented, designed and manufactured by the Taiwan National Metrology Institute, CMS/ITRI. The flow range is within (0.002 - 24) L/min. The uncertainty of the reference system is assessed against the ISO/IEC Guide 98-3:2008 document, Uncertainty is evaluated from individual influence sources such as category A and B assessments. The standard uncertainty/relative standard uncertainty and degrees of freedom of the sources can be evaluated individually and then combined to produce a composite standard uncertainty/combined relative standard uncertainty and an effective degree of freedom. Finally, the relative expanded uncertainty is obtained by multiplying the relative standard uncertainty associated with a coverage factor at the 95 % confidence level of the measurement result.

W. Kang, S. Im, N. D. Trang, J. Shin, Y-M Choi
Smokestack Gas Velocity Measurements using 3-D Pitot tubes in a Coal-Fired Power Plant

The fossil carbon dioxide (CO2) emissions from the combustion of fossil fuels and energy generators prevail over total greenhouse gas (GHG) emissions. Therefore, accurately estimating GHG emissions from stationary sources such as coal-fired power plants is also one of the efforts to mitigate the global rise in emissions. The GHG volumetric flow rates in stacks are measured mostly with the S-type Pitot tubes in Korea. But the S-type Pitot tube introduces error when it is operated under the presence of non-axial flows in stacks. In contrast, the three-dimensional (3D) Pitot tubes, which can determine all three-directional velocity components of the flow, are expected to surmount the restriction of the S-type Pitot tube. In this research, the flue gas velocity in the smokestack is measured with the 3D Pitot tubes to investigate the three-dimensional velocity profile and patterns inside the smokestack. The axial and off-axial velocity components of the flue gas in the smokestack are measured with two kinds of 3D Pitot tubes which are prism and spherical 3D Pitot tubes. They are compared with the TMS velocity which is measured with the S-type Pitot tube. The axial velocity components measured by the 3D Pitot tubes are well agreed with the TMS velocities by the S-type Pitot tube, and the velocity distribution and flow patterns inside the smokestack are investigated.

Ping Chen, Mei Chen, Miyue Zhao
Research of large diameter gas flow rate measurement method

To solve the hard problem of large diameter Pitot Pipe flow meter source tracing and parameter obtaining, we propose the similarity principle, which means making one (set) model that has same geometric structure but scaling down of the actual applied flow meter (prototype for short). We calibrate the model with gas flow standard facility, determine the mathematical formula and characteristic parameters of flow calculation, then applied on prototype. Base on DN4000 pipe air flow rate measurement project, we design a differential pressure flow meter based on the principle of Pitot static tubes for prototype. Models of DN1200, DN800 and DN400 are made at the same time. In order to verify the correctness and feasibility of the solution, this project is carried on in two steps. In first step, we make the models of DN600, DN300 and DN150, then test them with gas low standard facility, figure out the relationship of parameter of different diameter. In second step, we test the models of the flow meter actually in used. Base on the two groups of test results, we can find out the parameter of the flow meter actually in used. This essay is a phase summary of step one. The result shows that the Pitot tube flow meter with same geometric structure and similarity ratio is 2, their flow coefficient difference would not be larger than 5 %.

J. Geršl, J. Sluše
Insertion Depth Effect for Vane Anemometers

In this paper we show that velocity indication of a vane anemometer in a wind tunnel can significantly and non-trivially depend on length of the part of the anemometer’s mounting rod which is exposed to flow – the so-called insertion depth. The insertion depth dependencies for four vane anemometers with various dimensions are presented. For a small size vane anemometer with a propeller diameter of 22 mm, for example, a change of the insertion depth by 10 cm can cause a reading variation by up to 5 % - a value which is an order of magnitude larger than a typical expanded uncertainty of calibration in wind speed laboratories of national metrology institutes. Therefore, this effect has important consequences for selection of transfer standards for interlaboratory comparisons, since each participant can have a different insertion depth value, and also for the calibration practice where possible differences between the insertion depth of the user and the calibration laboratory should be taken into account.

S. Dixon, D. Greenshields, Z. Li, R. Burton, T. Burton, L. D. Smith
clamp-on AND transit time difference AND smart meter

A new, miniature design of a clamp-on ultrasonic transit-time difference flow meter for use in liquids is presented, with particular application to small diameter, thin walled metal pipes, opening up new areas of application, including smart water metering. The particular embodiment of the hardware is low cost and can be installed by unskilled users, and uses a type of guided wave mode that is significantly different to previous examples of clamp-on flowmeters that have used a leaky guided wave in the pipe to generate compression waves in the liquid. In the example presented in this paper, the entire liquid-pipe system acts as a wave guide, providing large amplitude ultrasonic signals with outstanding signal to noise, even from a drive voltage of just a few volts. The flowmeter is capable of measuring flow rates down to a few millilitres per second, with an accuracy better than 0.5 millilitres per second. The results presented mainly focus on 15 mm diameter copper pipes of wall thickness 0.7 mm, but the same approach works well on pipes with larger diameters and slightly thicker walls, up to around 30mm diameter in the current embodiment, In many instances, in previous work, the presence of the guided wave modes has prevented clear interpretation of the ultrasonic signals that are detected.

Yumeng Zhang, Ying Xu, Chao Yuan, Tao Li, Huimin Ma, Cenwei Sun, Yunhao Wen
The research on discharge coefficient of a non-standard Venturi meter with a swirler

Flow measurement plays an important role in the modern engineering field. And flow rate is one of the mostimportant parameter in this process. One traditional method of deriving flow rate is measuring the pressure difference (DP) along the pipe while the concerned fluid flowing through a DP instrument, such as Venturi meter. This DP instrument is among the most widely used flow measurement instruments, available inplumbing, energy transport pipeline, petroleum chemical industries, etc.In this research, a non-standard Venturi structure is proposed to satisfy the measurement demand of the inlet multi-phase flow with complex flow pattern. Compared to the standard Venturi meter,the angles of the divergent and the convergent of the proposed device are changed to obtain a shorter pipeline. Besides, a swirler is also placed into the convergent, which would force the flow to swirl with tangential velocity and adjust the inlet gas-liquid two phase flow to annular flow. The focus of the study is directed toward the pressure profile and the discharge coefficient Cd of the proposed structure. Computational simulation of single phase flow is carried out to measure the pressure drop along x- axis via FLUENT. According to the simulation results, the addition of swirler brings an extra pressure drop in advance. At the end of the throat, there is a sudden drop of pressure, decreasing to the lowest point, which is caused by the characteristics of the precession vortex. Then the final static pressure value is obviously lower than the initial static pressure value.

Rongji Zuo, Ying Xu, Chao Yuan, Tao Li, Chuanshun Wei, Linfei Cao, Ye Liu
Water holdup measurement of oil–water two-phase flow using dual-mode microwave method

Water cut is one of the key parameters in the process of oil and gas production. In the present study, wepropose a microwave resonant cavity sensor(MRCS) which can work in both TM010 and TM110 modes, andestablished a water cut measurement of vertical upward oil–water two-phase flow in the range of 0-100 %. The response characteristics of the two resonant modes to water cut are analyzed by the coupling simulation offlow field and electromagnetic field using COMSOL finite element simulation software. A flow experimentisconducted with the designed MRCS measurement system. The sensitivity of the two modes resonantfrequency in different water holdup range is compared. The results show that 95 % of the experimental points’ relative errors is less than ± 5 %.It is indicated that the model can predict water hold with high accuracy, which may provide a solution for wellhead water cut measurement of oil field.

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