基于层流流量计的多组分气体流量测量与补偿算法研究

本文选取气体层流流量计用于多组分气体的流量测量研究,在分析组分变化对层流流量计输出信号影响的基础上提出了组分补偿算法。实验结果表明该方法能有效补偿混合气体组分变化对流量计输出信号的影响。     

四声道超声波气体流量计自动增益控制电路设计

随着国民经济的迅速发展,冶金、化工等各部门对气体大流量的准确测量要求日益迫切。为了满足气体流量测量准确度不断提高的要求,超声波气体流量计被广泛应用于气体流量的检测与标定中。在超声波气体流量计的测量方法中应用最广泛的是时差法．时差法超声波气体流量计是通过测量超声波信号在流体中顺流和逆流传播时间之差来计算气体流速的,它具有准确度高、非接触测量、宽量程、无压力损失、安装使用简单等特点,     

气体涡轮流量计流场仿真及计量误差分析

利用控制体积法的SIMPLEC算法对气体涡轮流量计的内流场进行了数值模拟,给出了内流场信息,分析了内部几何结构对压力和速度分布的影响,及其与流量系数的关系.结果表明在湍流状态时的仪表系数K为常数,累计流量和瞬时流量的误差较小;而在层流以及转捩状态时,仪表系数总是在变化,累计流量和瞬时流量的误差较大.建议通过结构优化,促使层流向湍流状态的快速转捩,并保证叶轮动平衡,从而加大涡轮流量计的量程范围.该研究结果对涡轮流量计的结构优化设计具有一定的指导意义.     

用皂膜流量计标定气体小流量

一、前言测定瞬时流量的转子(浮子)式、量热式等气体流量计,需用气体实流来标定流量并校验其准确度。常用的方法是使保持一定压力的气流流过被测仪表,并测定一定时间内流过的气体体积,再经过计算得出流量率。我厂过去采用钟罩法和水排气法来进行这一标定工作,前者设备比较复     

皂膜流量计标准容积标定方法的探讨

皂膜流量计标准容积的示值误差决定了皂膜气体流量标准装置的准确度等级。为了准确标定皂膜流量计的标准容积，采用三种不同的方法分别对25mL的皂膜流量计进行标定，得出采用密封的轻质塑料杯作为称量容器得到的标准容积示值误差和重复性均最小，分别为-0．19％和0．08％，满足皂膜气体流量标准装置的准确度要求，采用玻璃烧杯和矿泉水瓶得到的标定结果均不合格。实验表明，蒸馏水温度变化和蒸发量、环境温度、容器自身重量等因素都会对标定结果产生重要影响，采用密封的、轻质的、壁厚的称量容积能够有效减少上述因素的影响，降低示值误差，提高重复性，从而准确标定皂膜流量计的标准容积，提高皂膜气体流量标准装置的准确度。     

热式流量计混合气体组分补偿策略

混合气体的组分变化将对热式流量计的输出造成一定影响,这是该类流量计在工程应用中的难题.本文从定温热式气体流量计的基本公式出发,结合电路结构,推导了热式流量计在不同气体组分条件下使用时输出信号之间的关联方程,定义了补偿系数.并提出利用补偿系数在流量计标定数据的基础上,进行组分补偿的方法和过程.将该补偿策略分别应用于SIERRA热式流量计以及自行设计的热式气体流量计样机,给出了其在现场煤气流量测量中的实验结果,验证了该补偿策略的有效性和实用性.     

气体腰轮流量计测量结果的不确定度分析

气体腰轮流量计属于气体容积式流量计的一种,根据其示值误差计算方法可分为A类气体腰轮流量计和B类气体腰轮流量计,使用仪表K系数计算示值误差的为A类,使用累积流量计算示值误差的为B类。针对这两类气体腰轮流量计的测量结果分别有不同的不确定度分析方法。     

便携式气体微小流量校准装置研制

文章介绍了一种便携式气体微小流量校准装置,该装置为现场气体流量校准设计,在保证准确度的同时注重便携性,以层流流量计为标准表,采用质量流量控制器来自动调节流量点,双重减压阀和稳压阀来保证气源压力稳定。     

系统压力变化和取压位置对罗茨气体流量计标定结果的影响

使用气体流量标准装置标定罗茨气体流量计,并分析系统状态参数变化对检测结果的影响。系统的管道压力损失是影响带温、压补偿罗茨气体流量计准确度的因素之一。一台DN50罗茨气体流量计的实测结果表明,当流量大于2/3量程时,管道内压力损失对被检表误差的影响最大可达1%。在实验管段上流量计前10D、表体、后1D、3D、5D和10D位置处分别取压,选择20 m~3/h、50 m~3/h和70 m~3/h流量点标定罗茨气体流量计的仪表系数,结果显示,取压位置不会对罗茨气体流量计本身的准确度等级产生较大影响。在检校过程中,如果受到拆装难度、标准装置、检测条件等因素限制,采用表前取压方式能够准确反映流量计的计量性能。     

湿度对皂膜流量计计量特性的影响研究

皂膜流量计是开展环境监测工作的重要计量器具。为满足环境监测用流量装置低压试验微小气体流量的有效溯源,减小气体湿度对皂膜流量计流量精确测量的影响,提升微小气体流量量值传递的可靠性,分析了皂膜流量计的工作特性,给出了皂膜流量计的微小气体流量湿度修正计算方法。基于中国计量科学研究院的微小气体流量标准装置进行了实验验证,结果表明该湿度修正计算方法可以有效降低湿度对皂膜流量计计量特性的影响。     

Secondary flow in non-isothermal viscoelastic parallel-plate flow

The non-isothermal, parallel-plate flow of a viscoelastic fluid is investigated. Using the singular perturbation method the problem for the stream function is reduced to a non-homogeneous boundary-value problem for the biharmonic operator in an infinite strip. An exact solution is then obtained using Fourier integral transforms. Our analysis shows the existence of thermally induced recirculating eddies, even when inertia is neglected.     

Decorrelation-based blood flow velocity estimation: effect of spread of flow velocity,linear flow velocity gradients,and parabolic flow

In recent years, a new method to measure transverse blood flow, based on the decorrelation of the radio frequency (RF) signals has been developed. In this paper, we investigated the influence of nonuniform flow on the velocity estimation. The decorrelation characteristics of transverse blood flow using an intravascular ultrasound (IVUS) array catheter are studied by means of computer modeling. Blood was simulated as a collection of randomly located point scatterers; moving this scattering medium transversally across the acoustical beam represented flow. First-order statistics were evaluated, and the signal-to-noise ratio from the signals were measured. The correlation coefficient method was used to present the results. Three velocity profiles were simulated: random spread of blood-flow velocity, linear blood-flow velocity gradient, and parabolic blood-flow. Radio frequency and envelope signals were used to calculate the decorrelation pattern. The results were compared to the mean decorrelation pattern for plug blood-flow. The RF signals decorrelation patterns were in good agreement with those obtained for plug blood flow. Envelope decorrelation patterns show a close agreement with the one for plug blood flow. For axial blood flow, there is a discrepancy between decorrelation patterns. The results presented here suggest that the decorrelation properties of an IVUS array catheter for measuring quantitative transverse blood flow probably will not be affected by different transverse blood-flow conditions     

流式细胞仪样品流速及聚焦流测量方法研究

为提高流式细胞仪的探测分辨率和数据检测的稳定性,需要精确控制样品流速,并分析样品流速和鞘液流速对样品聚焦流的影响,可通过样品聚焦流直径和样品聚焦流在流动室流道中的相对位置来评价样品的聚焦状况。利用蠕动泵运动特点,设计了一种平均流量称重法测量样品流速的方法,并与微流量传感器测量结果作比较;采用最小二乘法线性拟合蠕动泵的控制电压和样品流速之间的函数关系,并采用显微成像法直接测量和分析样品流速和鞘液流速对样品聚焦流直径、偏离流动室流道中心线的距离的影响。实验结果显示,采用平均流量称重法与微流量传感器测得的样品流速的线性相关系数高达0.982 8;蠕动泵的样品流速与其控制电压的线性相关系数高于0.99,说明利用该线性关系可以实现样品流速的精确控制;采用的显微成像法能快速方便地测得样品聚焦流的直径及位置,为流式细胞仪样品流速、鞘液流速的调控以及液流器件组装精度的测试提供了指导方法。     

流量测量临界流文丘里喷嘴的进展

简介颁布国际标准ISO9300《临界流文丘里喷嘴测量气体流量》(1990年)，十余年来国际上对该流量计的研究情况。主要在以下几方面有显著的进展：雷诺数使用范围的拓宽；流量方程中系数的研究；小型音速喷嘴的开发应用；小型音速喷嘴组合方法的研究；绝对测量法的探索等。国际标准化组织正在为修订ISO9300进行准备工作。     

流量控制电磁阀的小流量特性分析

介绍可调无级输出流量控制电磁阀在小流量输出区域的输出原理与特性。通过改变小流量区域的流道几何结构,改变电磁阀小流量区域的流量性能。     

Nonsteady flow of a vapor-drop flow in a heated channel

Flow of a vapor-drop mixture in a heated channel is studied under steady and non-steady conditions using a model which considers direct thermal interaction of drops with the heating surface.Translated from Inzhen-erno-Fizicheskii Zhurnal, Vol. 61, No. 6, pp. 939–946, December, 1991.     

An improved stochastic separated flow model for turbulent two-phase flow

 An improved stochastic separated flow model is proposed to obtain reasonable statistical characteristics of a two-phase flow. Effects of the history of a particle and its current trajectory position on the mean-square fluctuating velocity of the dispersed phase are continuously considered in this model. Comparing with the conventional model, results using the improved model are more reasonable and can also be obtained more easily. Furthermore, the improved model requires less computational particles for simulating dispersed-phase turbulence at the beginning of the stochastic trajectory. In this paper, an application in turbulent two-phase flow of planar mixing layer is carried out. Numerical results including velocity, mean-square fluctuating velocity, particle number density and pdf of fluctuation velocity of dispersed phase are shown to compare well with experimental data.     

Capillary plug flow distributor for stagnation point flow APCVD reactor

A novel flow distributor formed by cementing together uniform thin walled capillaries, termed a “capillary plug”, is employed as a gas distributor in a stagnation point flow APCVD reactor (AP=anisotropic porous). Its simplicity and high permeability allow reproducible film deposition over 9 cm² area with ± 2% thickness uniformity. Its design parameters, flow characteristics and advantages over conventional flow distributors are analyzed.     

Measurement of flow in supercritical flow regime using cutthroat flumes

Cutthroat flume is commonly used for measurement of subcritical flow in open channel because of its simplicity and ease of construction. No experimental data is available in literature for measurement of flow in supercritical regime using cutthroat flume. The present paper finds the feasibility of cutthroat flume as a measurement device for flow in supercritical regime. Experimental data are generated to develop the relation between discharge and observed head at a specified location on upstream of throat section. Regression analysis for discharge and head indicated a good correlation. Based on all the experimental data generated, a relationship between discharge and head is proposed.