离心引风机旋转失速的故障诊断及现场处理方法

针对锅炉离心引风机机壳及进出口管道振动剧烈的问题,使用 CSI2130振动分析仪进行了频谱分析.频谱显示0.7倍转频的幅值较大,基本符合风机旋转失速的故障特征.依据引起旋转失速故障的机理,将风机进口管道的人孔盖打开后,彻底解决了此问题.     

风机叶片振动原因分析

本文通过对离心风机叶片振动的研究分析,阐述了振动干扰力对风机叶片振动的影响,说明了振动干扰力对于离心风机的重要性,是离心风机保持平衡性的重要因素。分析了风机振动超标的几个原因,讨论在何种情况下能够实现离心风机的平衡性。     

锅炉烟道系统振动分析及改造研究

通过对电厂锅炉烟道系统振动进行分析及测试,结合机组烟道结构及实际运行情况,分析得到烟道系统振动原因是系统内部结构造成风机旋转脱流、系统本身刚度太差、气流分布不均以及气流在支柱产生涡流的因素。通过对烟道系统进行研究改造研究,加装导向片以及风机内弧形板和烟道系统进行加固等措施,让锅炉烟道振动降低。     

离心风机振动干扰力的分析

通过对离心风机振动干扰力的分析,阐述了振动干扰力在稳定的状态下和离心风机系统处于弹性形变的范围之内,是离心风机进行动平衡的前提条件.启发对现场离心风机的不同振动情况进行分析,从而实现有效动平衡.     

变频运行离心引风机轴向共振问题诊断及治理研究

在广泛调研的基础上,系统研究了风机转子及支撑系统的共振问题。以某电厂7号机组离心式引风机为例,通过现场振动测试、数值模拟及理论分析等方面对离心风机在变频调速情况下振动突然增大的现象进行了分析,发现对于变频调速离心引风机而言,在某个或几个转速发生振动突然增大的现象时,轴承座轴向支撑刚度及转子轴向共振频率(轴向摇摆disc-wobble)是影响轴向振动的关键参数。通过实践治理发现,对于这类风机转子共振现象,通过提高轴承座刚度,缩短转轴长度以及加固叶轮与转轴连接刚度等方法,能够有效地降低风机在特定转速下的轴向振动,消除共振现象,该研究结果及治理经验对于电站风机设备的转子及支撑系统共振治理有着广泛的推广意义。     

离心风机故障分析及维修总结

随着工业化的发展,我国的工业生产对机械设备的依赖逐步增强。离心风机是很多工业生产普遍使用的设备,其在应用中常常受到各种因素的影响而出现运行故障。在离心风机故障中,振动故障最常见。振动现象的出现使得离心风机的相关零部件受其影响出现损坏等,严重影响了离心风机的稳定运行。基于此,分析离心风机振动故障出现的原因,提出了相应的解决对策,有利于保持离心风机良好的运行状态。     

基于小波变换的离心风机故障诊断方法

异常振动是离心风机故障的主要表现形式,严重时影响生产运行。引起风机振动的原因很多,本文运用小波变换对离心风机振动故障进行分析,总结出引起离心风机振动超标的主要原因,对故障点进行检修。     

离心风机吸力侧旋转失速和进口涡流特征诊断

针对离心式风机进口涡流和吸力侧旋转失速的低频耦合问题，采用谐波小波变换方法，对4-73No8D型风机吸力侧旋转失速和进口涡流的脉动信号进行了时频分析和特征诊断。结果表明．二者均出现在10～50Hz范围内．吸力侧旋转失速的流量一频率关系是一条平坦的曲线．而进口涡流频率与流量成一定斜率的线性关系，且二者在耦合发展过程中存在时频信号分离现象。该方法能够有效诊断离心风机的非稳态流问题。     

纵轴流风筛式清选装置多因素试验研究

为了改善纵轴流水稻收获机清选装置的清选性能,在自行研制了纵轴流风筛式清选装置试验台的基础上进行正交旋转试验研究,分析了清选装置的曲柄转速、离心风机转速、离心风机倾角三个参数对功耗、含杂率、损失率的影响.利用各性能指标的回归方程,采用主目标函数法,用MATLAB进行优化求解,综合评定后得到优化参数为:曲柄转速为235r/min,离心风机转速为764r/min,风机倾角为28°,通过验证试验后,所得到的性能指标均满足要求.通过研究,可为清选装置的设计、制造和使用提供可借鉴的依据.     

低噪声高压头离心风机叶轮三元流设计计算研究

研究了叶轮内短叶片处于不同位置时对离心风机噪声、压头及效率的影响，提出了低噪声、高压头及高效率离心风机叶轮的三元流设计计算方法，并应用于水泥炉窑用风机，获得了良好的效果。     

Decrease in the operating gas pressure in an ion source

The results of use of a cold hollow cathode with a multipole magnetic field in a duoplasmatron-type ion source are described. The operating parameters of a duoplasmatron with the developed cathode and a duoplasmatron with a cold hollow two-cylinder cathode are compared. It is shown that the use of a cathode with a multipole magnetic field offers additional possibilities of reducing the operating gas pressure in an ion source and contributes to an increase in both the current and the phase density of the ion-beam current at the output of a charged-particle source and to a decrease in the phase volume of this beam.     

Determination of the velocity and size of bubbles in two-phase flows by using a laser doppler anemometer

Natural oscillations of a spherical interface between a gas and a liquid in a bubble are registered. A possibility of measuring the geometric parameters of stationary and moving particles of the disperse phase by a laser Doppler anemometer is demonstrated. A method for simultaneous determination of the size and velocity of a bubble or a droplet in a two-phase flow is developed. The mean sizes of a group of bubbles settled on a ruler are compared: the results are obtained by two independent methods, i.e., by analyzing the image and by processing the Doppler signal containing information about the natural oscillations of the spherical interface between the media. A possibility of using a laser Doppler anemometer for simultaneous measurements of the velocity and size of bubbles or droplets in a two-phase flow is confirmed.     

Automated fixture configuration using projective geometry approach

The geometric and topological specification of a workpiece boundary is usually represented in a specific data format in a CAD database. To retrieve a set of workpiece data, to analyse its shape in addition to the machining requirements, and to determine the proper fixture configuration accordingly, are not trivial tasks when a part has a complicated shape. The real challenge is to recognise and synthesise the shape of a workpiece from its data representation. Consequently, the decision for fixturing can be made when the shape of a workpiece and the relationship of the shape and the fixturing configuration can be derived by a systematic methodology. In this paper, a projective spatial occupancy enumeration (PSOE) approach is applied as a representational and manipulating scheme for developing algorithms in automatic fixture configuration. The workpiece is projected onto the working plane of the fixture baseplate. A 2D projection is defined as a matrix of cells which can represent a workpiece with an arbitrary shape. Using a discrete search based upon the matrix of cells, the fixture types and their locations are generated according to a set of heuristic algorithms. This work is a generalisation and extension of previous works for prismatic parts. The same methodology is equally applicable in general robot grasping.     

A re-configurable cross-sectional imaging system for reverse engineering based on a CNC milling machine

This paper presents a novel reverse engineering digitizing system for full part geometry, which is based on a cross-sectional imaging device built in a NC milling machine. The system successively captures a picture for each planar cross-section contour of the part by end-milling and CCD imaging, and builds the geometry for both external and internal surfaces of the complex 3D part based on a set of the vectored cross-sectional contours. The system mainly consists of three components: a NC milling machine, a cross-sectional imaging device and a computer control unit. Some issues involving the principle and process flow of the system, encasing materials, cross-sectional imaging and NC code generation, etc. are described in detail. Built on an existing NC milling machine, a portable device for capturing the cross-sectional images is designed, which includes an isolated light source, a digital camera, a protective case, a rigid arm and a robust tripod. The device, connected to a computer control unit, serves as a highly flexible accessory for the NC milling machine, constructing the cross-sectional imaging system for reverse engineering. Furthermore, the error analysis and accuracy assessment of the system are also addressed. A typical case is discussed in detail to illustrate the applications of the system. Such a re-configurable digitizing system for reverse engineering offers a number of advantages, such as the functional extension of an existing NC milling machine, low costs, and rapid construction. As a result, this system provides a feasible and useful scheme for many enterprises to construct their own reverse measuring system based on existing equipment to aid in rapid product development and extend the function of existing equipment.     

智能气体识别仪的研究

智能气体识别仪用以识别气体种类,它具有学习识别多种气体的功能。本文介绍了仪器的工作原理、特点及仪器的硬件和软件构成。     

套式钻模的应用研究

在各种长度和直径的圆柱体或空心圆柱体的外圆柱面上沿横截面圆周方向钻削,有较高的位置精度要求且呈多层均匀分布或多层非均匀分布或螺旋均匀分布或螺旋非均匀分布的孔和螺纹孔的方法进行了研究,重点介绍了长度与外径比＆gt;5的圆柱体或空心圆柱体。研究发现,目前常见的固定式钻模、回转分度式钻模、移动式钻模、翻转式钻模和盖板式钻模都不是最佳选择,因为它们的钻模板均为长方体,与圆柱面不能完全配合,导致夹紧元件和定位元件的结构复杂,形式单一且制造周期长,成本高,夹紧钻模的方式单一。套式钻模的钻模板为空心圆柱体,空心圆柱体的独特之处是使套式钻模可与圆柱面完美配合,夹紧元件和定位元件的结构简单,形式灵活且制造周期短,成本低,夹紧钻模的方式灵活,从而使其成为在各种长度和直径的圆柱体或空心圆柱体的外圆柱面上钻削各种排列组合方式的孔和螺纹孔的最佳选择。     

计算机辅助设计凸轮及其数控加工

介绍了如何利用计算机对于形状复杂和高精度的凸轮进行辅助设计,以及将设计结果直接在数控机床上加工的方法,分析了图解法设计的局限性和计算机辅助设计的优越性,指出了利用计算机辅助解析法设计是实现数控加工的基础,也是未来机械设计的发展方向。     

Wire electrochemical machining using reciprocated traveling wire

Wire electrochemical machining (WECM) is a cutting process in which the workpiece acts as an anode and the wire as a cathode. WECM is typically used to cut plates and exhibits a great advantage over wire electro-discharge machining, namely, the absence of a heat-affected zone around the cutting area. The enhancement of WECM accuracy is a research topic of great interest. In WECM, the homogeneity of the machined slit has a decisive influence on the machining accuracy. This is the first study in which the integration of pulse electrochemical machining (ECM) and a reciprocated traveling wire electrode was used to improve the homogeneity of this slit. The experimental results show that the combination of pulse ECM and a reciprocated traveling wire electrode could enhance the accuracy of WECM and that generally a low applied voltage, pulse duty cycle, and electrolyte concentration; an appropriate traveling wire velocity; and a high pulse frequency and feeding rate enhance the accuracy and stability of WECM. Finally, a microstructure with a slit width of 177 μm, with a standard deviation of 1.5 μm, and with an aspect ratio of 113 was fabricated on a stainless steel substrate measuring 20 mm in thickness.     

Calculation of the induction of a constant magnetic field created in a ferromagnet by an attachable electromagnet

On the grounds of the numerical calculation of the induction of a magnetic field excited in a ferromagnet by scanners in the form of Π-shaped and solenoidal electromagnets, it is established that the Π-shaped type provides a deeper penetration of a magnetic field into a ferromagnet and its better localization in a specified volume. The induction of a magnetic field appearing under the action of a Π-shaped scanner in a ferromagnet decreased with an increase in both the thicknesses of the ferromagnet and the gap between the magnetic conductor of a scanner and the surface of a material and also depended slightly on changes in its width; a maximal scanner winding current exists, above which the induction of a magnetic field in a material changes slightly.     

Microwave atomic force microscopy imaging for nanometer-scale electrical property characterization

We introduce a new type of microscopy which is capable of investigating surface topography and electrical property of conductive and dielectric materials simultaneously on a nanometer scale. The microwave atomic force microscopy is a combination of the principles of the scanning probe microscope and the microwave-measurement technique. As a result, under the noncontact AFM working conditions, we successfully generated a microwave image of a 200-nm Au film coating on a glass wafer substrate with a spatial resolution of 120 nm and a measured voltage difference of 19.2 mV between the two materials.