柔性机构振动控制的研究进展及存在的若干问题

闭链及开链柔性机构的振动控制问题已引起了许多研究者的关注,正逐渐成为机构动力学的一个新的研究热点。本文从被动控制、主动控制及主被动一体化控制等方面论述了柔性机构振动控制领域的研究现状、主要研究方法及存在的问题。提出了当前研究中应着重注意的几个方面和需要解决的关键问题。     

FMS系统的伸缩换向机械手的PLC控制

该文介绍了PLC在FMS系统中的伸缩换向机械手的应用,阐述了伸缩换向机械手的组成及控制流程。从PLC的控制原理角度,设计了伸缩换向机械手控制流程图、控制状态表、PLC的I/O接口设计及它们的地址分配,经实验验证,达到了预期效果。     

浅析起重机械焊接质量的控制策略

起重机械在焊接过程中,从焊工资格及控制、焊接工艺评定、焊接工艺控制、产品施焊控制、焊接材料及控制、焊接设备及控制、施焊环境及控制等方面,对起重机械焊接质量的控制策略几方面加强焊接质量控制,从而保证起重机械产品的焊接质量。     

焊接过程自动控制的研究状况及发展前景

本文简要介绍了目前应用于焊接领域的几种控制方法及它们的应用状况,分析了这几种控制方法的优缺点及应用价值,并指出PID控制、模糊控制、神经网络控制的结合在焊接控制中具有广阔的前景;多变量自动控制系统将成为焊接领域控制系统发展的趋势。     

FMS系统的液压换向机械手的PLC控制

首先介绍了PLC在FMS系统中液压换向机械手的应用,其次阐述了液压换向机械手的组成及控制流程。从PLC的控制原理角度,设计了液压换向机械手控制流程图、控制状态表、PLC的I/O接口及其地址分配。经试验验证,达到了预期效果。     

厚箔剪切机的电控系统设计

在厚箔剪切机的工作原理及设计数据介绍的基础上,对系统的电气配置方案、控制方案、控制系统的实现等进行了详细的设计。此电控系统经过了科学的数学计算及参数的配合,符合实际控制的需要,取得了良好的控制效果。     

FMS系统中立体仓库升降梯机械手的PLC控制

介绍了PLC在FMS系统升降梯机械手中的应用,阐述了立体仓库升降梯机械手的组成及控制流程。从PLC的控制原理角度设计了升降梯机械手控制流程图、电源系统图、PLC的I/O接口及其地址分配,经实验验证,达到了预期效果。     

一种定量注油器的结构及控制系统设计

以改变传统注油器控制不够灵活为目标,在完成新注油器结构设计与分析的基础上,该文阐述了新注油器的控制要点及控制思路。以FX2N系列PLC为控制核心进行了I/O分配及程序设计,并通过系统仿真验证了控制程序的可行性。该研究通过PLC对步进电机方向、速度的有效控制实现注油器的定量注油,为多个注油器的联合使用及一体化控制创造了条件,降低了技术人员的工作强度,增强了注油器的适用性。     

泰钢1700mm六辊可逆冷轧机板形控制技术的应用

介绍了泰钢冷轧厂1700 mm六辊可逆式冷轧机在板形控制方面的经验。通过张力控制、压下量控制、液压弯辊控制、轧辊轴向横移控制及工艺润滑系统控制,有效地改善了板形,提高了轧制产品质量。     

日立传动系统在梅钢冷轧厂的应用

介绍了梅钢冷轧厂酸轧机组日立小容量传动系统的硬件组成、控制功能及原理等,总结了日立传动系统的主要控制功能及优缺点。     

旋转管式膜分离器流型的研究

采用三相异步电动机的输入电磁转速与三相异步电动机的实际转速之差的变化来表征两旋转圆筒间流场特性的参数。主要研究了清水介质时无轴向流和有轴向流条件下流型的划分,并将无轴向流时的流型分成了6种：Couette层流,层流泰勒涡,层流波涡,层流调制波涡、湍流泰勒涡和湍流;有轴向流时的流型分成了4种：Couene层流、层流泰勒涡、湍流泰勒涡和完全湍流。并且验证了流型转变的滞后特性。     

基于经验模态分解和BP神经网络的油气两相流流型辨识

基于经验模态分解（empidcal mode decomposition，EMD）BP神经网络，提出了油气两相流流型辨识的新方法。应用EMD将差压信号分解成不同频率尺度上的单组分之和，并提取组分的归一化能量作为流型辨识特征量。BP神经网络以这些能量特征量为输入对油气两相流不同流型（包括泡状流、塞状流、层状流、弹状流和环状流）进行分类。实验结果表明，本文提出的流型辨识方法是有效的，其中泡状流、塞状流、层状流、弹状流和环状流的辨识精度分别为100％、89．4％,93．3％、96.3％和96.9％。     

Pressure data for various flow channels in proton exchange membrane (PEM) fuel cell

Micro flow channels in flow plates of fuel cells have become much narrower and longer to improve reactant flow distribution leading to increase of pumping power. Therefore it is very important to minimize the pressure drops in the flow channel because increased pumping power reduces overall efficiency. We investigated pressure drops in a micro flow channel at the anode and cathode compared to pressure losses for cold flow in straight, bended and serpentine channels. The results show that friction factors for cold flow channels could be used for parallel and bended flow channel designs for fuel cells. Pressure drop in the serpentine flow channel is the lowest among all flow channels due to bypass flow across the gas diffusion layer under reactive flow condition, although its pressure drop is highest for a cold flow condition. So the effect of bypass flow for serpentine flow channels should be considered when designing flow channels     

大口径高温高压Y形截止阀的设计

介绍了Y形截止阀的结构特点和阀门流道的结构设计,计算了介质通过截止阀时的流阻及压降,分析了流道形式和流通面积等对压降的影响,论证了流体在阀门流道中的速度变化形态以及阀门设计的合理性.     

水平管气液衰减螺旋流的流型及压降发展

气液衰减螺旋流在工业中应用广泛,但是对其中的关键问题,衰减影响下的螺旋流发展运动规律认识不清。通过室内试验研究空气-水两相流在内径25 mm、长4 m的水平管中流型和压降沿流向的变化规律。通过可视化试验获得叶片式起旋器下游不同位置处的螺旋流流型,测量下游沿流向不同区间的压降波动信号。试验发现,在离心力作用下,螺旋流中气液相界面发生重构,形成螺旋流中特有流型。但是由于离心力的衰减,导致螺旋流流型不断变化,逐渐转变成非旋流流型。流动压降沿流向逐渐降低,最终趋于非旋流压降;不同螺旋流流型的维持距离不同,同时也受来流气液相雷诺数的影响。基于流型及压降分析,获得起旋器下游不同位置处的螺旋流流型图。     

螺旋流发生装置的对比分析研究

螺旋流是一种具有旋转流场的流动形式,在工业方面的应用范围极广。同时,螺旋流也进入了人们日常生活领域。目前影响螺旋流更广泛地工业化应用的关键在于高效的螺旋流发生装置。本文主要介绍并分析了各种螺旋流发生器的结构形式及性能特点。另外,对其优缺点进行研究分析,指出了发明并设计出一种高效使用的螺旋流发生器的重要性。最后,分析了螺旋流发生器的发展方向,为进一步研究螺旋流产生装置以及螺旋流提供参考。     

介质流向对偏心旋转阀冲蚀的影响

针对某石化公司DN50-ANSI600偏心旋转阀在恶劣工况下的冲蚀问题,采用Fluent软件对其流开和流闭两类模型的流量特性以及实际工况流场特性进行了仿真分析,研究了介质流向对阀门冲蚀的影响。结果表明:两种流向的流量特性曲线趋势相同,但流闭更有利于流体流动;两种流向的有效流量调节开度均在0~70°;开度越小,流体流动越紊乱;流闭模型腔内旋涡远少于流开模型,流动稳定性更好,更有利于防止阀门的冲蚀破坏。在某些工况,若流开的阀门冲蚀、振动和噪声严重,可以考虑采用流闭流向。     

Flow noise characterization of gas–liquid two-phase flow based on acoustic emission

Flow noise of gas–liquid two-phase flow in horizontal pipeline was detected by using the acoustic emission technique (AE); signals were processed by wavelet transform and chaotic analysis. Conclusions were drawn that stratified flow, annular flow and their transition can be divided clearly through multi-scale energy distribution of flow noise, and that dynamic characteristic of flow pattern transition from stratified flow to annular flow, which is described via correlation dimension, acts in accordance with that of annular flow. The dynamic characteristic of the transition condition has already been consistent with that of the annular flow, but due to the low gas flow rate, the energy of the hydrodynamic noise was not enough to reach the complete annular flow pattern. Results were in accordance with experimental facts. Flow noise reflects the complexity of gas–liquid two-phase flow by means of multi-scale energy distribution and chaotic features. Consequently, flow noise based on acoustic emission is a novel and promising point for researching gas–liquid two-phase flow.     

Effect of the convergence flow conditioner on rectifying eccentric jet flow induced by a ball valve

Installing a flow conditioner is an important method for rectifying irregular and unstable flow to stable flow state within a short flow distance in fluid transportation and control industrial applications. However, classical flow conditioners (such as Laws and Zanker flow conditioners in ISO 5167) with parallel pipeline axial orifices ineffectively rectify the distinct eccentric jet flow caused by valve regulation. The convergence flow conditioner with convergent orifices was innovatively designed for rectifying the eccentric jet flow caused by a ball valve in this study. Three convergent orifice angles (8°, 10°, and 12°) defined as angles between orifice and pipeline axes were considered to compare their effect on eccentric jet flow rectification as well as with the classical Laws flow conditioner (characterized by the convergent orifice angle of 0°) under different valve openings with an experimental setup for monitoring downstream pressures that develop along the pipeline and corresponding numerical simulation used. Pressure loss and throttling effect of installing convergence flow conditioners downstream the ball valve was assessed. Analysis of distributions of the pressure, velocity, and streamline for convergent flow conditioners showed that the flow conditioner with a large convergent orifice angle can effectively improve violent eccentric jet flows, especially under a small valve opening. The axial velocity on various downstream cross sections was extracted to evaluate the velocity uniformity. A dimensionless parameter of velocity eccentric ratio was used to quantify the rectification effect of eccentric jet flow evolving in the downstream pipeline. Results showed that a short pipeline length is needed to obtain additional symmetry and uniform flow field downstream of the flow conditioner with a high convergent orifice angle, that is, the convergence flow conditioner with a high convergent orifice angle demonstrated a strong effect of flow rectification on the valve-induced eccentric jet flow. This work can help understand characteristics of flow rectification on valve-induced eccentric jet flow in scientific research, and provide guidance for the flow conditioner design in fluid engineering.