Modelling and optimization of a wellhead gas flowmeter using concentric pipes

A novel configuration of a landfill wellhead was analysed to measure the flow rate of gas extracted from sanitary landfills. The device provides access points for pressure measurement integral to flow rate computation similarly to orifice and Venturi meters, and has the advantage of eliminating the problem of water condensation often impairing the accuracy thereof. It is proved that the proposed configuration entails comparable computational complexity and negligible sensitivity to geometric parameters. Calibration for the new device was attained using a custom optimization procedure, operating on a quadri-dimensional parameter surface evincing discontinuity and non-smoothness.     

Pitometry as a validation tool for water flow measurement in large diameter pipelines

Accurate measurement of water flow rates in large diameter pipelines is a challenge for water companies that need to produce, transport and distribute increasing quantities of water. To a large extent, this challenge results from the impossibility of recalibration of the flow meters within the periodicity established in the metrological regulations since the removal of a large size flow meter from its site of operation in the field and its transport to a calibration laboratory is in most cases technically and economically impracticable. Because of this scenario, this paper presents the pitometry technique as an interesting alternative to solve problems related to the validation of water flow measurements performed by flow measurement systems installed in large diameter conduits. The technique is based on the determination of the water flow rate by mapping the velocity profile of the water flow inside the pipe by means of Cole type Pitot tubes. The water flow rate is determined in a cross section of the pipe located near and in series to the flowmeter to be evaluated. Based on the results obtained in a great number of water flow measurements already performed by applying the pitometry technique in large diameter pipelines in the field, it is possible to conclude that this methodology is perfectly applicable in the validation of the performance of flow meters installed in these conduits solving satisfactorily the issues related to its operation.     

Experimental investigation of an oscillating circular piston positive displacement flowmeter: II – Leakage flows and wear tests

Experimental data from an oscillating circular piston positive displacement flowmeter are described which focused on leakage flows and wear. This is the second part of a two part paper on the experimental tests, the first part concerned piston movement and pressure loss. In this paper the leakage across the meter is reported for key parameters including: flow rate, liquid density and viscosity, mass of circular piston, surface coating and length of connection pipes. In addition to the average leakage over a period of time, the leakage past a stationary circular piston was measured during a simulated oscillation. Wear tests were run for both stainless steel and carbon pistons to identify the affected areas of piston and chamber.     

基于单片机的散体流量计的设计与开发

散状固体在加工、运输和配料时,常需要自动化的动态计量,和气、液或多相流比较,散体的种类繁多、物理特性差别较大,进行实时精确计量十分困难。目前对散体的动态计量所采用的冲板流量计、核子秤和电子皮带秤等方式,存在稳定性差、准确度低等问题。论文利用科里奥利原理和机械设计理论,从计量装置的硬件设计开始,到信号接收与显示、应用程序开发,最后进行系统的测试与标定,完成了一种基于单片机的散体流量计的整体设计。此流量计结构简单、检修工作量小,动态测量精度高、过载能力强,在进一步控制电机转速的情况下,还能调整其测量量程,可以适用于工业生产中不同的计量需要。     

不同截流程度下涡街流量计的流动特性研究

对于涡街流量计的旋涡发生体的仿真研究主要集中在形状和尺寸上,但在现场复杂工况环境的情况下,发生体的位置并不是固定不变的,会存在安装偏差。为了很好的分析发生体安装偏差带来的信号强度发生变化的问题,确定不影响信号强度的最大偏差角度,采用三角柱型发生体,在Ansys＋Workbench＋FLUENT 数值仿真软件平台环境下,根据涡街流量计的实际物理结构尺寸建立仿真模型,并对其进行网格划分、求解,将仿真得到的升、阻力频率相比较,得出阻力频率正好是升力频率的2倍,表明可以利用FLUENT软件对涡街流量计进行三维流场数值仿真。最后利用FL U EN T软件,通过改变管截面与截流面的夹角,在低、中、高速流速下,对其进行取压,将得到的信号强度和频谱分布进行比较分析,得出夹角与信号强度的关系：夹角在1°～7°范围,对信号强度的影响不大,超过7°以后影响变大。     

晶圆减薄过程TTV调整技术研究

晶圆背面减薄是集成电路后封装关键工艺,通过金刚石磨轮的磨削作用,对芯片背面的基体材料-硅材料去除一定的厚度,从而降低芯片厚度,改善芯片的散热效果,有利于后期的封装工艺。主要介绍了在晶圆减薄过程中的关键指标TTV 的影响因素,通过设备自动控制,进行工艺角度调整,能够减小晶圆TTV 值,从而提高晶圆磨削质量。     

油田工业多相流量计技术适用性分析

以油田工业为背景,讨论多相流量计常用的流量、组分测量技术、互相关技术和部分分离技术在油田工业中的适用性和应用中所涉及的关键问题,指出了多相流量计技术适用性评估的6个方面(测量不确定度、两相图分析、流体工况适用性、安全和环保、油藏管理效果和现场安装条件)。     

浅谈数控车床主轴轴承的检测与定向装配

主轴系统是数控车床机械部分中的关键部位,其装配精度直接影响到机床的加工精度,而主轴轴承的选型、测量、装配方法至关重要。介绍一种数控车床主轴轴承的检测与定向装配方法,装配后主轴精度高,轴承使用寿命长,性能稳定。     

顶磨式轧辊磨床头架主轴分析及拓扑优化

主轴是轧辊磨床头架系统中最关键的部件,需承载巨大的工件而要求较高的强度和刚度。针对主轴刚度对轧辊磨削精度影响较大这一问题,借助ABAQUS软件,运用有限元多体分析法对某型号的轧辊磨床主轴进行了线性静力分析,得到了主轴的应力及位移分布情况,分析表明主轴后段强度大有富余。在静力分析基础上对主轴进行了拓扑优化设计,结果表明:该优化方案正确合理地完成了减重25%的轻量化结构设计,可为主轴的二次设计及类似轴类零件设计起到指导作用。