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.     

Pulsatile blood flows through a bileaflet mechanical heart valve with different approach methods of numerical analysis; pulsatile flows with fixed leaflets and interacted with moving leaflets

Many researchers have investigated the blood flow characteristics through bileaflet mechanical heart valves using computational fluid dynamics (CFD) models. Their numerical approach methods can be classified into three types; steady flow analysis, pulsatile flow analysis with fixed leaflets, and pulsatile flow analysis with moving leaflets. The first and second methods have been generally employed for two-dimensional and three-dimensional calculations. The pulsatile flow analysis interacted with moving leaflets has been recently introduced and tried only in two-dimensional analysis because this approach method has difficulty in considering simultaneously two physics of blood flow and leaflet behavior interacted with blood flow. In this publication, numerical calculation for pulsatile flow with moving leaflets using a fluid-structure interaction method has been performed in a three-dimensional geometry. Also, pulsatile flow with fixed leaflets has been analyzed for comparison with the case with moving leaflets. The calculated results using the fluid-structure interaction model have shown good agreements with results visualized by previous experiments. In peak systole, calculations with the two approach methods have predicted similar flow fields. However, the model with fixed leaflets has not been able to predict the flow fields during opening and closing phases. Therefore, the model with moving leaflets is rigorously required for advanced analysis of flow fields.     

Critical flow venturi with a step-wall diffuser

The study investigates the critical flow venturi (CVN) with step-wall diffusers for constant volume gas flow rate in critical flow mode. An analytical method for the estimation of the pressure ratio required for the onset of critical flow from these CVN is given. Numerical simulation and experiments have both been employed to compare the onset of critical flow in two types of CVN: ISO 9300 [1] CVN and a CVN with a geometrically similar inlet and a step-wall diffuser with 4 cylindrical sections replacing the conical diffuser. Good agreement between the analytical, numerical and experimental data has been obtained. The CVN with step-wall diffusers have been demonstrated to provide stable flow rate in the critical flow operation mode, however somewhat higher pressure ratio is required to ensure the critical flow in this case.     

Effect of wall roughness changes on ultrasonic gas flowmeters

A theoretical flow model has been developed to describe accurately a fully developed velocity profile of a gas flow in pipe lines with wall roughness as parameter. The model applies the Colebrook and White skin friction correlation which has been adjusted based on experimental data from Princeton SuperPipe facilities. This has resulted in a flow profile model in line with the latest views. The model has shown a significant flow profile variation for wall roughness changes. An ultrasonic ray propagation model of a single path meter has been developed to study the influence of the mentioned flow profile variations on ultrasonic meters. The model has been applied for various cases with different Reynolds number and wall roughness. The results of the study confirm field data that ultrasonic meters are affected by wall roughness changes. To quantify the effect for multipath ultrasonic meters the flow meter algorithm and path position is required.     

Flow measurement structures

Weirs, flumes and gates have been used for centuries to determine discharges in open channels. In this paper the distinct flow types, modular flow and non-modular flow, are described and applied to derive the head-discharge relations of weirs with a horizontal crest. The flow measurement structures are classified according to international rules. For a number of decades, the ability of flow measurement structures to allow fish migration has also been judged. On the other hand, some well-known fishways have been considered to act as an alternative flow measurement structure. The presentation of the Venturi gate, which combines the functions of flow measurement structure and fishway, concludes the paper.     

叶片通用扭曲规律的拓展及抛物线流型的控制

分析了叶片一般通用扭曲规律,在此基础上拓展了一般通用扭曲规律。提出了叶片抛物线流型,适当增加了叶片均径附近的能量头,减小了叶尖与叶根附近的能量头。利用通用扭曲规律的拓展形式,通过选择不同的控制系数,能够获得传统常用流型以及不同能量头分布的抛物线流型。对比了抛物线流型与等环量、等反动度流型,结果表明,抛物线流型改善了反动度、入口相对速度马赫数、气流出口角、气流折转角的分布,克服了传统流型叶根易出现负反动度、叶尖入口相对速度马赫数过大等缺点,缓解了叶根气流出口角和气流折转角过大等问题。     

锥形流量计下游支撑及取压位置的试验研究

锥形流量计应用广泛,其国际标准正在起草中。锥形流量计发展过程遇到两个问题：安全性和制造一致性差,具有双支撑结构的锥形流量计可解决此问题。为保证增加的双支撑结构不会影响锥形流量计的测量性能和较短的表体长度,需要研究下游支撑和下游取压位置。根据锥形流量计尾流流场的速度分布和压力分布的状况设计相关的改进试验,选择合适的下游支撑和下游取压位置。试验使用的锥形流量计经过特殊设计：锥体、下游支撑位置、下游取压位置都可以按照要求变换位置。试验得到适用于不同直径管道的下游取压位置和支撑位置的选取规律。不同管径和等效直径比下的锥形流量计试验数据显示：改进后的双支撑形式的锥形流量计样机比悬臂梁锥形流量计具有更好的流出系数不确定度。     

Response of a slotted orifice flow meter to an air/water mixture

The ability of a flow meter to respond predictably to the presence of liquid and gas is important to the natural gas industry and to users of steam. In both cases, the gas can become saturated and some liquids can condense in the line. The response of orifice flow meters to the presence of liquids is erratic and produces considerable uncertainty. Turbine flow meters can sustain severe damage when subjected to two phase flow. The slotted orifice flow meter has been developed to address the problem of upstream flow conditioning. This device has been shown to be insensitive to the upstream velocity profile. To further evaluate the flow meter for use by the natural gas industry, the effects of adding liquid to a gas flow upon the meter performance has been investigated by subjecting a slotted orifice flow meter with an equivalent β ratio of 0.50 to a two phase flow consisting of air and water.     

A novel technique of using a thyristor driven pump as the final control element and flow indicator of a flow control loop

In the present paper, design of a flow control loop using a thyristor driven pump as final control element has been described. In this technique, the load current of a thyristor driven pump motor has been utilized as a mass flow sensing parameter of a fluid passing through a pipeline. This thyristor driven pump has been utilized as a final control element of a flow control loop and the speed of the pump has been selected as the manipulated variable. The non-linearity between the thyristor input signal and pump output has been eliminated by using a modified PID control technique with inverse derivative control action. Thus without using any conventional flow meter and control valve only the thyristor driven pump has been utilized both as the final control element and flow indicating device by using the proposed technique. The whole system has been designed, fabricated and tested by using tap water as the flowing liquid through a pipe line. The experimental results along with the theoretical analysis are compared and reported in the paper.     

Flow structure in critical flow Venturi nozzle and its effect on the flow rate

The flow fields in toroidal Venturi-nozzles, shaped according to the ISO-9300 Standard, have been investigated using numerical flow simulation. The present study was aimed at clarifying some of the phenomena associated with unchoking the flow in the throat. To this end, the shock structure has been studied for different Reynolds numbers and exit pressure ratios. The flow simulations were carried out in two and three dimensions. The flow fields were always unsteady, displaying a complex shock–boundary layer interaction.     

Thermophoretic transport and deposition of particles in vertical tube flow with variable wall temperature and thermal radiation

A particulate two phase flow with variable wall temperature has been studied for examining the deposition of particles in the thermal radiation and mixed convection flow associated with the manufacture of optical fiber preforms. The two-dimensional governing equations of continuity, momentum and energy have been solved numerically including the effects of thermal radiation and buoyancy (upward or downward flow) in the vertical tube flow. A particle trajectory model has been adopted to predict the particle transport, and P-1 approximation has been used to evaluate the radiation heat transfer. In the upward flow case, a high deposition efficiency is obtained and the deposition zone of the downward flow is broader than that of the upward flow. Thermal radiation makes the deposition zone broader and the deposition efficiency smaller.     

离心压缩机圆形截面蜗壳内部三维流场的实验研究

利用五孔探针对离心压缩机蜗壳内部的三维流动进行了详细的测量,在此基础之上,着重对圆形截面偏心蜗壳内部三维流场的流动过程进行研究与分析,旨在为把握其三维流动的生成演化细节和积累流动图谱等基础性资料,为今后蜗壳设计与改良提供可靠数据并打下良好基础。     

车用催化器流场的数值模拟与结构优化设计

为了改善载体内速度分布,同时减小催化器内的压力损失,建立了基于一种新型导流装置的催化器内部流动的数学模型,并对其流场进行了二维稳态数值模拟。根据仿真结果,分析影响载体内流动特性的主要因素,为导流装置的改进确定方案。具体研究了导流装置结构参数d1:d2的改变对流动特性的影响,分析了速度分布和压力损失的变化规律,得出了一种较优的结构。加装导流装置后,流动在进入扩张管时提前分流,从而使载体前端流速分布更均匀,提高了载体的通过能力,减小了排气背压。     

Experimental investigation of a cavitating Venturi and its application to flow metering

An experimental investigation has been carried out to evaluate the performance of a cavitating Venturi flow. For that purpose, a closed loop circuit with a centrifugal pump and a transparent asymmetric converging-diverging test section has been built which allows to set the pressure level and the flow rate. The system is instrumented with several pressure sensors and temperature probes that are continuously monitored during the tests. The experiments have consisted in generating non-cavitating and cavitating flows inside the Venturi under controlled conditions. The obtained results, which have been characterized as a function of the Venturi's discharge coefficient, pressure ratio and pressure loss coefficient, are in good agreement with previous studies carried out with standard Venturi geometries, specially under non-cavitating flows. The Venturi's performance under cavitation flows has been found to be dependent on the Venturi's inlet pressure and similar to a chocked flow condition with constant volumetric flow rate. On the basis of these observations and the analogous behaviour with compressible gas nozzles, a new flow coefficient has been derived which remains constant at any cavitating regime. Thus, this coefficient permits to use a Venturi as a flow meter on cavitation conditions.     

电控喷油器流量特性试验台的开发与试验分析

分析了电控喷油器的喷油过程和驱动电路形式对其流量特性的影响,详细介绍了所设计的喷油器流量试验台及其控制单元的组成及原理。以高阻型喷油器为例,在整个流量范围内对其进行测试并对测试数据加以分析总结,得出了该喷油器流量特性的一些重要参数。比较了电压和油压对流量特性的影响,并提出了相应的补偿措施。测试系统为喷油器的开发提供了一个良好的测试平台。     

A mountain stream flowmeter

A new method of continuously gauging the flow in steep mountain torrents has been investigated. Seismic vibrations in the bedrock, resulting from the tumbling water flowing in a mountain stream, have been recorded from a site in north Wales and have been compared to direct current meter flow measurements over a wide range of flow conditions. A relationship has been established whereby the flow may be inferred from the seismic vibrations.     

一种新型的电容式油气两相流相份额传感器

本文介绍了一个高精度的电容式两相流相份额传感器。该传感器是非插入式,传感部件与测量电路集成一体,排除了寄生电容和杂散电容的影响,使测量精度和稳定性大大提高;输出是直流电压信号,便于计算机自动采集数据;动态反应快,适于实时在线测量。可用于管内油气两相流相份额测量、流型识别、两相流量测量和流动状态监测     

输水管网爆管切断阀的研制与应用

针对传统爆管切断阀超声波流速检测机构易损坏、寿命短、维护保养不便等问题,研制出一种新型的爆管切断阀。该阀门流速检测机构采用机械式测速仪,通过流速检测板摆动角度大小检测管道流速,从而避免了超声波流速检测机构易损坏以及性能不稳定的问题。该阀门具有结构紧凑、反应迅速、流阻系数小、安装维护简便等特点,在工程中已经成功应用。     

PC-based gas-solids two-phase mass flowmeter for pneumatically conveying systems

The development and performance of a PC-based instrumentation system for measuring the mass flow rate of gas-solid flow in a pneumatically conveying system have been discussed in this paper. A laboratory scale pneumatic conveyor incorporating facilities for calibration has been fabricated for this purpose. The test section is a vertical plexiglass tube of diameter 12.7 mm with an upward flow direction and sand has been used as the solid phase. The principle of measurement is based on inferential technique. Instantaneous velocity and concentration of the bulk solids are measured using a pair of electrodynamic sensors and a capacitance sensor, respectively. Several modifications of the existing technique of measurement have been suggested.     

多品种小批量生产环境下基于约束管理的混流制造运行控制技术研究

在多品种小批量生产环境中,现有的、以适应大批量重复型生产过程为主的混流制造技术难以得到推广,为实现此类生产环境下的精益化改造,出现了基于混流路径的混流制造新模式.在研究该模式总体架构的基础上,提出多品种小批量生产环境下基于约束管理的混流制造运行控制机制,并就混流路径规划、资源瓶颈识别与动态瓶颈管理等关键技术进行探讨,为进一步的研究应用提供基础.