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.     

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.     

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.     

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.     

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.     

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.     

High precision Coriolis mass flow measurement applied to small volume proving

This paper discusses Small Volume Provers (SVPs), used in the oil and gas industry to validate the performance of custody transfer meters. Recently Coriolis mass flow meters have been introduced for custody transfer; while these offer reduced maintenance requirements over traditional PD and turbine meters, proving Coriolis flow meters using SVP is challenging. This paper presents SVP results for a Coriolis meter which matches or exceeds the most stringent requirements for custody transfer. This is achieved in part by using a novel signal processing technique which reduces the dominant component of the measurement noise, associated with so-called Coriolis mode vibration, with negligible loss of dynamic response.     

高压涡轮导向器前支撑质量流量测量研究

试验测量总是伴随有误差的产生,这里对音速喷管在航空发动机高压涡轮内部导向器流量测量系统进行分析,主要介绍误差来源、误差分配理论分析方法及其在实际仪器选择上的应用.以高压涡轮内部导向器前支撑流量测量为例,在给定测量系统总误差条件下,提出一种可行的误差分配方案.该方案满足精度要求,成本低.     

一种多通道微流控芯片压力检测方法研究

针对微流控芯片中的流路压力,特别是多通道的压力测量问题,提出了一种利用微尺度层流结合显微图像处理进行多通道压力(流速)测量的方法,并以双路通道情况为例,设计并制作了一种基于层流的多通道压力检测芯片.主要研究内容包括微尺度层流条件下压力(流速)测量方法的建立、多通道压力测压芯片的设计和制作、对该芯片模型的仿真分析和利用显微图像处理获得实验数据几个方面.最终,通过设计验证实验得到的数据与仿真结果的对比,验证了方法的可行性.     

影响待测物面测量误差的因素及补偿

分析被测物面对激光三角法测量技术的影响,从原理、位移传感器的非线性补偿、被测表面倾角、被测表面特征(颜色、粗糙度、光泽)几方面分析误差产生的原因。探讨各因素的误差补偿方法,对传感器进行非线性误差标定,测量出其非线性误差曲线图;使用标注件标定激光头本身倾角误差,对绘制倾角误差测量结果做曲线拟合;对被测件表面的颜色处理;在非特定条件下,可以忽略表面光泽度和粗糙度;最后综合上述过程,得出测量结果。该方法提高了测量精度。对于小型机电,电子产品外形反求测量,提高其生产过程中的测量精度,具有一定指导作用。