The consistency of pressure effects between three identical Coriolis flow meters

Coriolis flow meters are one of the most popular flow measurement technologies in the world today for high accuracy measurement of single-phase liquids, gases and even slurries. They are capable of measuring both mass and density directly and can also infer the volume flow. They can be installed in challenging process environments and have been successfully deployed with non-Newtonian fluids, high viscosity fluids, pulsating flows and even at extreme temperatures and pressures.However, it is known that operating most Coriolis flow meters at a pressure which differs from the original calibration pressure requires compensation else significant measurement errors will occur. Pressure compensation coefficients appear to vary by manufacturer, meter geometry and sensor material. Furthermore, the manufacturer published pressure compensation coefficients are not fully traceable. To date, there has not been sufficient research exploring the consistency of the pressure compensation for identical Coriolis flow meters.This paper presents the findings of a research conducted at the TÜV SÜD National Engineering Laboratory (NEL) Elevated Pressure and Temperature (EPAT) oil flow facility to investigate the pressure effect uniformity for matching Coriolis devices. The first stage of the experimental programme calibrated three identical DN80 Coriolis flow meters at a range of pressures with no pressure compensation applied. A pressure compensation coefficient was then derived from the data and the Coriolis meters were then calibrated at two alternative pressures to ascertain the robustness of the coefficients and whether the compensation could be extrapolated successfully.From the experimental results, it can be concluded that the pressure effect for the three DN80 Coriolis flow meters was extremely repeatable and consistent with a discrepancy of less than 0.025% between the devices at 80 bar. Whilst the mass flow was significantly affected by fluid pressure, the fluid density did not appear to be influenced. The pressure corrected results were also well within the manufacturer specification of ±0.1%.     

双直管科氏质量流量计传感器设计理论研究

本文针对科里奥利力质量流量计传感器的机械设计理论进行了深入广泛研究，给出了传感器相关参数计算式，并按本文给出的设计方法进行了试验考证，取得了满意结果。     

Effect of fluid pressure on Coriolis mass flowmeter''s performance

This paper presents some tests which have been carried out on a commercial model of Coriolis mass flowmeter under medium-pressure conditions (p > 15 bar), utilizing a primary standard flow calibration facility. The experimental results show that the fluid pressure affects the accuracy of the tested meter, which provides underestimated readings (i.e. negative errors). Finally, some diagrams which allow to correct the output signal (or the reading) provided by the tested meter (according to the operating fluid pressure) are also presented.     

Calibration of hydrogen Coriolis flow meters using nitrogen and air and investigation of the influence of temperature on measurement accuracy

The performance of four Coriolis flow meters designed for use in hydrogen refuelling stations was evaluated with air and nitrogen by three members of the MetroHyVe JRP consortium; NEL, METAS and CESAME EXADEBIT.A wide range of conditions were tested overall, with gas flow rates ranging from (0.05–2) kg/min and pressures ranging from (20–86) bar. The majority of tests were conducted at nominal pressures of either 20 bar or 40 bar, in order to match the density of hydrogen at 350 bar and 20 °C or 700 bar and −40 °C. For the conditions tested, pressure did not have a noticeable influence on meter performance.When the flow meters were operated at ambient temperatures and within the manufacturer's recommended flow rate ranges, errors were generally within ±1%. Errors within ±0.5% were achievable for the medium to high flow rates.The influence of temperature on meter performance was also studied, with testing under both stable and transient conditions and temperatures as low as −40 °C.When the tested flow meters were allowed sufficient time to reach thermal equilibrium with the incoming gas, temperature effects were limited. The magnitude and spread of errors increased, but errors within ±2% were achievable at moderate to high flow rates. Conversely, errors as high as 15% were observed in tests where logging began before temperatures stabilised and there was a large difference in temperature between the flow meter and the incoming gas.One of the flow meters tested with nitrogen was later installed in a hydrogen refuelling station and tested against the METAS Hydrogen Field Test Standard (HFTS). Under these conditions, errors ranged from 0.47% to 0.91%. Testing with nitrogen at the same flow rates yielded errors of −0.61% to −0.82%.     

密度对质量流量计测量原油含水率的影响

针对利用质量流量计测量原油含水率的过程中油水密度的问题，对其原理及影响测量精度的密度因素进行理论分析，并根据含水率监测误差发生的原因进行分析，总结质量流量计在原油含水监测中出现的误差的调整措施，为该型仪表在原油计量方面的应用做了进一步的探索。     

U型科氏质量流量计的灵敏度特性与结构参数关系分析

建立了U型科氏质量流量计的力学模型，研究了其灵敏度系数的计算方法并导出了灵敏度系数计算公式，为U型科氏质量流量计提供了设计依据。     

Flow measurement based on the combination of swirler and differential pressure under slug flow

The alternating appearance of elongated bubbles and liquid slugs of slug flow in the pipe causes severe pressure fluctuation. As a result, measuring the flow rate of the slug flow with the throttling unit based differential pressure method is difficult. This paper investigates a new swirler-based flow measurement method in slug flow. The swirler converts the slug flow into a swirling annular flow, and the differential pressure method is used to measure the flow rate. The influences of gas and liquid flow rates on the differential pressure ΔP_X across the swirler as well as its downstream axial differential pressure ΔP_Z are investigated. ΔP_X^0.5 increases linearly as the liquid mass flow rate increases, and the slope of the curve increases as the gas mass flow rate increases. The influence of gas mass flow rate on ΔP_X^0.5 is comparable to that of liquid mass flow rate on ΔP_X^0.5. ΔP_Z^0.5 increases linearly with increasing gas/liquid mass flow rate, and the slope of the curve of ΔP_Z^0.5 with m_l differs slightly from the slope of the curve in single-phase water conditions. Based on the research presented above, new empirical correlations of mass flow rate based on ΔP_X and ΔP_Z are established respectively. The superficial liquid velocity ranges from 0.6 to 2 m per second, while the superficial gas velocity ranges from 2 to 6 m per second. If the gas mass flow rate and ΔP_X are known, the relative error of liquid mass flow is less than 3%. The relative error of the gas mass flow rate is less than 10% if the liquid mass flow rate and ΔP_X are given. The calculation accuracy of the flow measurement model using ΔP_X is better than the calculation accuracy of the flow measurement model using ΔP_Z.     

高速透气阀压力阀流场分析及启闭特性研究

建立了高速透气阀压力阀的出流流场模型,对其压力场及速度场的分布情况进行了分析。通过对比阀门在半开和全开状态下的流场分布,得知:压力阀阀门在全开状态时阀内压力更小,气体出流速度更高,为比较好的工作状态。讨论了压力阀开启和关闭的具体过程,对于只有重力控制和重力与磁力联合控制两种情况下压力阀的启闭特性分别进行了研究,分析了磁力对于透气阀的稳定开启和消除颤振所起的作用及阀门控制力的设定原则。分析结果可为高速透气阀的优化设计和应用研究提供借鉴。