A CFD study of low pressure wet gas metering using slotted orifice meters

Wet gas metering is becoming an increasingly important problem to many industries, in particular the oil and gas industry. Extensive studies have been done in the past on Venturi and standard orifice differential pressure (DP) flow meters to tackle wet gas flow problems. However in recent years, the slotted orifice flow meter has been developed in the attempt to improve the performance of the standard orifice meter. The novel flow meter is shown to be insensitive to the upstream flow profile with lower head loss and faster pressure recovery. This paper describes the numerical studies to establish the effect of different geometrical perforations on the performance of the slotted orifice. Three sets of slotted orifices with varying aspect ratios (1.5≤l/w≤3.0), of rectangular perforations and one slotted orifice with a circular perforation and a β ratio of 0.40 are simulated in a 1.6 m horizontal pipe using the k-ε turbulence model over a range of parameters, i.e. gas volume fraction (GVF) and gas mass flow rate. The commercial CFD code, FLUENT 6.3 was used to model the wet gas flow. Simulation results revealed that the shape of the perforation has no effect on the differential pressure, However, a marginally better pressure recovery was observed with rectangular perforations of l/w=3.0. The relatively higher over-reading values obtained in this work are consistent with the results of Geng et al. (2006) [1] that for a slotted orifice, a low β ratio is more sensitive to the liquid presence in the stream and hence is preferable for wet gas metering. Mass flow prediction by wet gas correlations showed that the homogeneous model, Steven’s and De Leeuw’s correlations had the best performance, with a calculated mean error of 4%-5%.     

全像素双核成像技术及应用研究综述

全像素双核(dual-pixel, DP)自动对焦(dual-pixel CMOS auto focus, DP CMOS AF)采用混合检测自动对焦,其在每个像素配备两个光电二极管,使每个像素既参与对焦又参与成像,克服了传统相位检测自动对焦和反差检测自动对焦技术的缺点。根据离焦视差估计图像合焦镜头所需移动的距离,DP自动对焦具有更快的对焦速度和更高的对焦精度,因此广泛应用在手持设备中(如手机相机、单反相机等)。由于全像素双核传感器将每个像素分成两半,该传感器一次拍摄即可得到两幅图像。这两幅图像(全像素双核图像对)可以看做一个具有相同曝光时间和严格校正的小基线立体图像对。该图像对的视差与图像模糊程度相对应,只在离焦区域存在视差。全像素双核传感器不仅用于自动对焦,而且可以用于深度估计、散焦去模糊和反射去除等方面。本文系统地综述了全像素双核传感器的自动对焦、成像原理及研究现状,并进一步展望其未来发展。1)对自动对焦技术进行介绍,对比了传统对焦与全像素双核对焦;2)详细分析了全像素双核传感器的成像原理、成像模型及特点;3)系统地介绍了全像素双核在计算机视觉领域应用的最新进展,从深度估计、反射去除和离焦模糊去除等方面进行全面阐述及分析; 4)适当的数据集是基于深度学习方法的基础,对目前的全像素双核数据集进行了介绍;5)分析了全像素双核在计算机视觉领域面临的挑战与机遇,对未来的全像素双核应用方向进行了讨论与展望。     

Characteristics of Welding Crack Defects and Failure Mode in Resistance Spot Welding of DP780 Steel

The mechanical properties of welded joints in resistance spot welding of DP780 steel were tested,and three dif-ferent types of welding cracks in welded joints were investigated by optical microscopy,scanning electron microscopy and electron back-scattered diffraction.Finally,the failure mode of the welded joints in shear tensile test was dis-cussed.It is found the shear tensile strength of welded joints can be greatly improved by adding preheating current or tempering current.The surface crack in welded joint is intergranular fracture,while the inner crack in welded joint is transgranular fracture,and the surface crack on the edge of the electrode imprint can be improved by adding prehea-ting current or tempering current.The traditional failure mode criterion advised by American Welding Society is no longer suitable for DP780 spot welds and the critical nugget size suggested by Pouranvari is overestimated.     

基于S7-300系列PLC电梯系统的设计

对于现代化电梯控制系统,设计控制核心器件是基于西门子300系列PLC。通过PLC程序组成的控制系统其运行可靠性高,使用维修方便,抗干扰性强,设计和调试周期较短等优点。通过Wincc Flexible监控仿真结果表明,电梯的运行以及可触摸屏式的控制面板功能,为电梯控制的人性化、智能化发展提供新的思路。     

轧管机自动换顶头精确定位自动控制系统

轧管机自动换顶头精确定位自动控制系统采用西门子S5-155U PLC,同时采用IP246I智能模板完成精确定位,通过模拟量下达速度设定值到SIMOREG K 6RA24,同时采用IM308B通讯模板通过PROFIBUS DP总线完成SIMOREG K 6RA24控制字、状态字的读写.     

基于Profibus-DP的变频器控制系统

在分析了现有变频器群控系统布线复杂和维护困难的基础上,提出了变频器Profibus-DP现场总线控制系统。总结了该系统在现场应用时的特点。结合西门子6SE70系列变频器,给出了系统的网络结构及计算机与变频器之间的通讯协议。最后描述了变频器的Profibus-DP现场总线控制系统的功能码设置步骤和编程过程。该系统接线简单、维护方便、工作可靠。     

芳香族聚磷酸酯的聚合度与阻燃性质的研究

分别采用氧指数,差示扫描量热分析,热失重分析,ＩＲ光谱分析等方法研究了聚合度分布在２０－１２０区间的芳香聚磷酸酯对环氧树脂固化物阻燃作用的变化规律。结果表明,ＤＰ为４３－５５之间的ＰＰＰ阻燃作用最佳。     

柠檬酸的棉布无甲醛耐久压烫整理

本文对CA、SHP、柔软剂浓度以及焙烘温度和时间进行单因素分析和多元线性回归分析,确定了柠檬酸的棉布无甲醛耐久压烫整理的最佳工艺。结果表明：该技术有一定的优势和可行性。     

退火温度对冷轧DP980钢力学性能的影响

利用连续退火模拟机对DP980试验钢进行了连续退火试验,并通过扫描电镜、电子背散射衍射、透射电镜等研究了不同退火温度下(775、800、825和850 ℃),试验钢显微组织的演变规律和力学性能的变化趋势。结果表明:试验钢的屈服强度随着退火温度的升高而不断增大(从705 MPa增大到850 MPa),抗拉强度和断后伸长率则随着退火温度的升高而不断减小(抗拉强度从1150 MPa减小到1030 MPa;伸长率从8.9%减小到5.3%),这与试验钢的显微组织构成和形态分布密切相关。此外,不同退火温度下,试验钢的加工硬化率曲线均呈现单调下降的趋势。     

DP780高强钢U形弯曲回弹影响因素及优化

目的 研究DP780高强钢不同参数对其U形弯曲回弹的影响。方法 在室温下对DP780钢板材进行拉伸试验,获得其应力应变曲线。采用U形弯曲模具模型,利用ABAQUS有限元仿真软件对U形弯曲回弹进行分析,研究摩擦因数、压边力、冲压速度和凹凸模间隙对U形弯曲回弹的影响规律,并在此基础上设计正交试验以优化影响参数。结果 在较小的摩擦因数下,回弹是有微小波动的,继续增大摩擦因数,回弹呈现减小的趋势;回弹随着压边力的增大先增大后减小;冲压速度的改变对回弹的影响不是很大;随着凹凸模间隙的增加,回弹逐渐增大。结论 通过正交试验得到4个参数对回弹程度的影响,最佳参数组合为A5B5C3D1,以此参数组合得出的侧壁角θ1和法兰角θ2最接近90°,回弹效果最好。