差压式流量传感器测量一般气体流量时的温度压力补偿方法

简要介绍使用差压式流量传感器进行一般气体流量测量时的温压补偿方法;指出了差压方式流量传感器测量一般气体的通用流量温压补偿公式,并写出了公式的推导过程;与线性流量传感器温压补偿方法进行对比,强调指出了采用差压式流量传感器时进行温压补偿的注意要点.对公用工程中的一般气体的流量计量工作有一定的指导作用.     

温压补偿在MED装置蒸汽流量测量中的应用

为解决低温多效蒸馏（MED）淡化过程中蒸汽温度、压力波动引起的蒸汽流量测量不准确的问题,依托30t/d MED淡化中试装置,本文分析了进料蒸汽的温度、压力变化特点,研究选择适用于MED工艺的补偿公式和数学模型,并通过PLC控制实现补偿。结果表明：通过温度、压力补偿提高了MED蒸汽流量测量的准确度,增强了MED淡化系统的运行稳定性和经济性。     

核能海水淡化源蒸汽质量流量的测量与新的密度补偿式

本采用汽液两相流均相流动的模型,分析了涡街流量计在核能海水淡化源汽的捏流量测量中的适用性,并结合低压和蒸汽的热物理性质,论述了涡街流量计测量低压饱和蒸汽质量流量的误差一蒸汽干度之间关系。给出了一个用于低压饱和蒸汽质量流量测量的变系数密度补偿式和该补偿式的特色。     

深海压力适应型水下机器人压力补偿技术

针对深海水下机器人在高达60MPa的外界环境压力下工作效率低下、可靠性较差等问题,研究了一种弹簧活塞式压力补偿器的结构,可以使得工作在深海的电液控制系统与环境压力自动平衡。在此基础上,对该补偿器进行了相应的静态特性和动态特性的仿真分析。结果表明,在保证储存的补偿流量足够的前提下,该补偿器具有较快的动态频响,并能始终保证系统内部补偿压力略高于外界环境压力,大幅度提高了电液控制系统在深海作业的总体效率及对不同工作水深的适应性,确保了系统的可靠抗压密封。     

Enhanced pulverized coal mass flow measurement

Two methods of coal flow measurement are described in this article for a pulverized coal injection (PCI) process into blast furnaces. The original coal flow design is based on vessel weight variation along the time, a moving average and an ordinary PID controller. Enhanced coal flow devices of mass solid correlation with an auto-calibration unit were specially designed and installed in the main conveying pipeline of three coal injection stations. Therefore, the PCI plant now takes advantage of each measurement and chooses the best for safety interlocks and control.     

一种温度补偿式光纤氢气检测技术

基于非本征法布里-珀罗光纤传感检测技术,分析研究了氢敏薄膜特性,实现了氢气传感单元设计及制作,简要介绍了传感器结构、制作方法、镀膜工艺及设备.通过分析氢气浓度与法布里-珀罗腔长变化间的关系,建立了光纤法布里-珀罗氢气传感理论模型.为增强系统工程实用性,着重研究了传感器温度与氢气浓度交叉敏感问题,并利用温度补偿技术消除环境温度干扰.介绍了温度补偿原理并构建实验设备,最后通过氢气浓度响应实验及温度特性实验,证明理论公式推导结果与实验数据吻合较好,且氢气传感器温度敏感性降低.此设计具有一定工程实用价值.     

Coriolis mass flow measurement at cryogenic temperatures

With the growing interest in liquefied natural gas (LNG) in the energy market, Coriolis mass flowmeters have been applied to many applications in the distribution of LNG. Since Coriolis flowmeters are normally calibrated at around room temperatures, measurements for LNG at cryogenic temperatures present a challenging condition. Firstly, a theoretical analysis for Coriolis mass flow sensors is provided considering the major changes of material properties (Young’s modulus and thermal expansion) at cryogenic temperatures. Then, a practical approach which can be used to correct the flow calibration factor obtained at a reference condition is presented. Finally, flow test results obtained from NIST’s cryogenic calibration facility are provided. Based on the results, it can be concluded that if a Coriolis flowmeter is calibrated at a reference condition and the flow calibration factor is corrected considering the non-linearity of Young’s modulus and thermal expansion change with temperature, it can still provide very accurate mass flow measurement even at cryogenic temperatures.     

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。     

Automatic compensation for grinding wheel wear by pressure based in-process measurement in wet grinding

This paper deals with an application to automatic compensation of grinding wheel wear by a pressure based in-process measurement method in wet grinding. A pressure sensor is set beside a grinding wheel with a small gap. When grinding fluid is dragged into the gap by the rotation, hydrodynamic pressure, which corresponds to the gap length and the topography, can be measured. No electromagnetic properties of the workpiece and grinding wheel affect measured results. This method is applied to a CNC surface grinding machine. The pressure distribution and the relationship between the pressure and the gap length are measured. The pressure is decreased with the increase of the gap length. Its dispersion is around 1% for 0.5 μm-wear of a grinding wheel with 250 μm grit size. The dimensional error of a workpiece using the feedback of the wear is less than the feeding step, for the compensation, of 1 μm.     

An examination of suitability of multi-hole pressure probe technique for skin friction measurement in turbulent flow

The problems of misalignment to flow direction and the need to drill a tapping hole on a measurement surface to obtain total and static pressures make the use of Preston probe in skin friction measurement in a turbulent flow a cumbersome task. The suitability of a multi-hole pressure probe in a non-nulling mode to overcome these problems was, therefore, investigated. The near-wall effect on multi-hole pressure probe readings was examined both experimentally and theoretically. The results indicate that the presence of the wall had negligible overall effect. Experiments were carried out in a pipe, on a flat plate and on a swept forward facing step to simulate one-, two-, and three-dimensional turbulent flows. The skin friction coefficient determined using the multi-hole pressure probe was found to have good agreement with published data. Since the technique is based on similarity principle with probe diameter as a characteristic parameter, it is expected that the method would be effective with probe geometries of different sizes provided that they are small enough to be submerged in the boundary layer and that their calibration coefficients are accurately determined.     

Fibre-optic sensors for temperature,pressure and flow measurement

In this paper, the use of fibre-optic techniques for measurement of the important parameters, temperature, pressure and fluid flow, especially blood flow, is reviewed. The characteristics of these devices are described and their applicability discussed.     

智能扩散硅差压变送器的数字补偿技术

本文首先讨论了用特殊函数法对扩散硅差压变送器进行数字补偿的技术,并详细介绍了利用线性插值法进行传感器信号处理的原理和方法。     

Experimental study on dynamic performance of coriolis mass flow meter and compensation technology

The Coriolis mass flow meter, for its features of directly measuring mass flow and high precision, is widely utilized in the flow measuring fields like batch filling and commercial trade. However, the unsatisfactory dynamic performance is one major constraint to Coriolis mass flow meter from being even more widely used in batch filling industry. To solve the problem, an experimental system which generates refined flow step stimulus signals for Coriolis mass flow meter was designed and based on which experimental and theoretical study on dynamic performances of typical Coriolis mass flow meter was carried out. On top of this, a time-domain recursive digital filter was designed to provide dynamic compensation and the experiments showed this filter can reduce the step response time of Coriolis mass flow meter by about 50%.     

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.     

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.     

The primary dynamic gravimetric system for gas mass flow measurement

High accuracy mass flow measurement is an enabling technology at the base of many industries. HORIBA STEC Co., Ltd. developed its own primary gas mass flow measurement system. We employed the dynamic gravimetric method in a vacuum chamber, and we use only mass and time information for mass flow rate calculation, with no correction for temperature, pressure and humidity. The system achieved 0.036% uncertainty as lowest of results with satisfactory performance of proficiency testing with NIST (National Institute of Standards and Technology). Then the laboratory has been granted ISO/IEC 17025 accreditation since 2017. This paper describes the system details and uncertainty analysis.     

Detection and measurement of the inverse axial flow by means of the flying hot wire technique

In the reviewed literature about swirling flows through ducts of circular cross section, there are contradictions regarding the detection and measurement of the inverse axial flow generated in the center of a swirling flow. The main motivation for this investigation was to determine the existence of the inverse flow and the feasibility of measuring it by the flying hot wire technique using unidimensional and bidimensional hot wires driven with an intermittent linear servomotor with a maximum velocity of 2 m/s and with a distance trip of 0.595 m. The inverse flow was detected with both sensors but it was not constant during the maximum speed trip. The maximum speed and the duration of the inverse flow was obtained with the unidimensional sensor up to a radial position of 3 cm, although the axial position in which the inverse flow is detected, it is not the same in every radial position. Therefore, it is not possible to make a radial distribution of the axial velocity using only one sensor. Finally, in the center of the swirling flow there is an intermittent inverse flow similar to the recirculating flow that is generated in the wake of a body in relative motion to the fluid mass.     

Ancillary device for flow rate measurement using dye tracer technique

Dye tracer technique is a successful tool for measuring liquid flow in closed conduits and open channels. The technique is based on the continuous injection of a tracer into the flow and on the measurement of the dilution ratio. As one of the requirements, the tracer injection rate must be known and well controlled. A device was designed to obtain this control. Such device implements a volumetric flow measurement technique and provides accurate digital display readout. Experimental results indicate that the apparatus can be used to measure the injection flow rate in a range from 235 to 2000 ml min⁻¹ with a relative error smaller than 1.5% of the reading. Even with these low injection flow, the dilution method can be applied to determine the much higher flow rates typically found in domestic or industrial outfalls as well as in artificial or natural channels. This paper also presents an application of the dilution method to flow rate measurement of an industrial outfall and the uncertainty analysis associated with the obtained values. The results indicate that the main errors of discharge estimation can arise from non-steady state flow conditions, incomplete tracer mixing, uncertainty of tracer concentration and tracer injection rate measurements.