移动式标准表法气体流量标准装置的抗震研究

移动式标准表法气体流量标准装置,可将标准表法气体流量标准装置通过车载的方式运至流量计使用现场进行流量计检定校准工作,但由于标准装置运输过程中和流量计使用现场的路况及动力设备的高度集成等因素的存在,使得抗震设计及其方法研究成为保证移动式标准表法气体流量标准装置在运行过程中稳定可靠的首要问题。该文对一套移动式标准表法气体流量标准装置通过加装弹簧减震杆及气囊减震系统的方法进行抗震优化,并通过一年的实际实验验证,验证了该抗震设计在保证此标准装置及其标准表性能稳定可靠方面的有效性。     

高精度标准气体流量测控仪设计

研究了利用涡街流量计测量标准气体流量的原理,介绍了以8098单片机为核心的高精度标准气体流量测控仪的硬件组成和软件功能。测控仪实际运行效果良好。     

示踪法测量气体流量的试验研究

以空气作为被测流体,以CO作为示踪气体,在直径为0.300m的90°弯曲管道内对示踪法测量气体流量进行了试验研究。结果表明,多点释放/多点取样比单点释放/单点取样时,取样点处示踪气体的浓度测量偏差小。释放点位于弯头上游7D～13D(D为管道直径)、取样点位于弯头下游10D～14D处,流量计算值(示踪法)与测量值(涡轮流量计)的相对误差在-2.15%～1.69%的范围内,释放点与取样点的位置越远,示踪法测量流量的相对误差越小。示踪气体的释放量需要与管道输送气体流量相匹配。对于含有脏污介质的大口径管道工业气体输送过程中的流量计,采用示踪法进行在线校准,是一种简单有效的校准方法。     

PVTt法气体流量标准装置参数的选择与确定

本文基于PVTt法气体流量标准装置的流量基本方程及装置的基本特征,详细分析与论证了装置主要参数,如标准容器容积V、充气初态Pi与终态压力Pf、质量流量qm或体积流量qv的选择与确定,特别对于该装置在整体上为非定常流中要保持流经流量计为定常流的基本特征、措施与气动设计方法作了全面、系统而深入的分析,涉及确定充气终态压力Pf的流动阻力系数的概念是首次由作者明确地引入的。     

音速喷嘴法气体流量标准装置比对分析

本文主要介绍了华北大区五个省级计量实验室的音速喷嘴法气体流量标准装置间的比对,通过比对统一了音速喷嘴法气体流量标准装置的测量方法及不确定度分析,提高了计量实验室的气体流量标准装置的计量水平。     

标准涡街流量传感器组合比较法气体流量装置的研究和探讨

本文介绍了用标准涡街流量传感器组合比较法的流量标准装置、检测原理和数据处理方法，解决了大口径气体流量仪表的标定问题。     

气体流量标准装置的恒温恒压控制系统

本文介绍了一种在正压式气体流量标准装置上使用的恒温恒压控制系统。详细介绍了该系统的技术方案和技术原理,以及在装置上的使用效果。     

钟罩式气体流量标准装置检定中的思考

本文介绍了钟罩式气体流量标准装置的原理和检定方法,并结合实际工作对检定过程中需要注意的问题进行了较为详细的阐述。     

改进取压方式提升音速喷嘴气体流量标准装置的准确度

音速喷嘴气体流量标准装置因其结构简单、性能稳定、准确度较高、无可动部件、维护方便等特点,成为气体流量计量检测的主流标准装置。被检表以及标准器处的气体取压方式有两种:绝压、绝压+差压。通过对装置不确定度评定,测差压的差压变送器量程范围小,降低了最大允许误差;测被检表与标准器处气体的绝压共用同一个绝压变送器,灵敏系数的降低,提高了准确度。同样采用0.2级压力变送器测压的标准装置,前者因压力引起的相对标准不确定度为0.177%,而后者为0.016 6%,仅为前者的1/10,装置的扩展标准不确定度U_r=0.24%,k=2,完全满足准确度等级为1.0级气体流量计的检定要求。采用绝压+差压取压方式,在不提高压力变送器准确度等级的情况下,有效提升装置的准确度。该方法简单可行,适用范围广,可应用于其他气体流量标准装置。     

Measurement of gas flow rate from helium standard leaks

Helium standard leaks are widely used to check and calibrate mass spectrometer leak detectors. Precisely known gas flows are required for measurement of quantities of standard leak rates. A fundamental task of the constructed and presented calibration apparatus is precise measurement of gas leak rate. Thus a primary standard for calibration helium standard leaks in the range from 10⁻¹⁰ to 10⁻⁵ Pa m³/s has been completed at the Laboratory of Vacuum Measurements in Tele & Radio Research Institute.     

In situ calibration of Coriolis flowmeters for high-pressure gas flow calorimetry

An in situ calibration method for small Coriolis meters used for high-pressure gas flow calorimetry is presented. The method has an accuracy better than 0.02%, at level one standard deviation. Two meters, both with a totalizer function, have been evaluated, and the total long-term accuracy of the best meter is ±0.11% at level one standard deviation.     

Coriolis mass flow measurement of gas under normal conditions

This paper presents a new method of directly measuring the mass flow of gas using the well-known Coriolis principle, which has proved successful for mass flow measurement of liquids. The prototype consists of two U-shaped tubes, forming a device resembling very much a tuning fork, which is stimulated by electromagnetic actuators to perform autonomous bending oscillations. By this means the fluid is subjected to a radial velocity that, in combination with the axial velocity of the flow, induces harmonic Coriolis forces of the same frequency. This causes the U-shaped tube to perform torsional oscillations that superimpose on the bending oscillations. Both oscillations can be detected via electromagnetic transducers.

The amplitude of the torsional oscillation induced by the Coriolis forces is very small as the density of gas is very low. It can be amplified by tuning the eigenfrequencies of torsion and bending in a control loop. This results in an amplification of the torsional amplitude by a factor of 10², allowing the mass flow of gas to be measured under normal conditions.     

温度补偿法在流量控制和标准气稀释中的研究及应用

分析了质量流量控制器中温度变化所引起的流量变化理论值与实际值之间的关系,提出一种实用的梯度温度补偿方法,即将环境温度划分为若干梯度,针对每一梯度配置不同修正系数,有效消除环境温度变化对标准气配气仪精度的影响。实验结果表明,该方法解决了环境温度的干扰问题,保证了流量控制及标准气稀释的精度,为其它温度敏感设备提供了参考。     

Liquid hydrocarbon flow meters calibration with high flow and viscosity: Conceptual design of a new facility

The oil and natural gas production market is heavily regulated with specifications that are almost always defined and valid for each producing country. In all the focus is to ensure accurate and complete results in volumes produced but with specificities of each location. In Brazil this regulation was created in the year 2000 (Joint Ordinance No. 001 between the National Petroleum Agency - ANP and the National Institute of Metrology, Quality and Technology - INMETRO) and in the 2013 review it was specified that liquid hydrocarbon flow meters should be calibrated with fluid under the conditions closest to those found in the operation considering density, viscosity, flow, pressure and temperature. However, the type of oil produced in Brazilian fields typically has high viscosity and there is an additional aspect due to the use of FPSO (Floating Production Storage and Offloading) type production platforms: flow to tankers occurs at high flow rates. There are several restrictions in laboratories worldwide to meet these conditions (high viscosity with high flow) and so the purpose of this paper is to present a proposal that technically meets the conditions imposed by Brazilian regulations and that will serve as a reference for operations in other similar fields. The project considers the laboratory should be able to perform calibrations up to 3200 m^3/h, oil densities above 0.88, with flexibility for changing calibration fluid, pressure and temperature control and viscosities up to 700 cP. To this end, a broad evaluation was carried out with solution providers and a research group within the university to technical support     

正压法气体流量标定系统的设计与实现

随着非标准流量仪表种类和数量的日益增加,为了保证仪表的测量精度。非标流量仪表的标定要求显得日益迫切。系统采用了国际标准文丘利作为标准表。应用标准流量计“比较法”原理,配合计算机程序控制,建立气体流量标定系统。进行流量计的检定和测试。依据有关的国家检定规程。该装置可对多孔孔板、V锥、楔形、巴类等差压式仪表以及涡轮、涡街、旋进旋涡等流量计进行检定、工业现场流量模拟实验以及风洞实验。通过运行实践证明,该系统测量精度高,稳定性好,标定流量范围宽。     

基于 MEMS 的量热式传感器气体流量测量的模型研究

气体流量测量广泛应用于呼吸监测、管道运输等领域。本研究细致分析了MEMS量热式传感器温度一维分布模型中的热边界层参数,进行了相应的经验修正。并且在温度一维分布模型的基础上,针对具有两对上下游测温电阻芯片结构的MEMS量热式传感器,提出了一种新的传感器输出电压关于气体流量的半修正理论模型。该理论模型能够适用于不同类型的单介质气体。同时,开展了N₂、CO₂流量测量实验,与理论模型进行对比,证明所提出的理论模型可以正确预测不同气体介质的流量,其中针对CO₂测量介质的均方根误差为0.15%。此外,结合理论分析,提出了一种高精度,拟合形式简单、针对确定气体适用性更好的测量模型,其中针对CO₂测量介质的均方根误差为0.05%。     

A new approach to gas flow calibration

Primary gas flow standards create calculable flow rates using two different techniques. Displacement systems rely upon the accurate determination of the first order change in position of an object being displaced by gas flowing at a constant pressure. Pressure, volume, temperature and time (PVTt) systems provide a nearly constant mass flow of gas to an accumulation tank of known volume over a fixed time interval. Measurements of pressure, temperature and time are used to calculate flow rate.     

Wet gas measurements of long-throat Venturi Tube based on forced annular flow

A wet gas dual-parameter measuring device composed of a cyclone and a long-throated Venturi tube is proposed to overcome the difficulty of measuring the liquid content of wet gases and reduce the error caused by the wet gas flow pattern. The flow pattern is transformed into an annular flow by a cyclone. In this study, the proposed device was compared with a traditional non-cyclone long-throat Venturi tube; furthermore, the pressure difference ratio W between the contraction and expansion sections of the long-throat Venturi tube was introduced as a parameter. Through numerical simulations, the relationship between W, the gas Froude number, over-reading, and liquid-gas mass flow ratio was analyzed, and a new wet gas flow measurement model was established. The reliability of the measurement model was verified through indoor experiments. The experimental results showed that the traditional wet gas measurement device had gas phase and liquid phase errors of ±4.5% and ±10%, respectively; on the other hand, the cyclone-based wet gas measurement device had gas phase and liquid phase errors of ±3% and ±8%, respectively. Thus, the performance of the wet gas measurement device with the cyclone was higher than that of the traditional wet gas measurement device.