汽轮发电机组振动故障分析及处理

C25-8.83/0.981是一台抽汽供热式汽轮发电机组.该机组在启动调试过程中,发现其存在四号轴承轴向振动超标故障、发电机转子热不平衡故障和汽轮机动静碰磨故障等问题.本文通过启动运行过程中对机组参数监控及轴系振动的监测,经过对现象及相关数据的分析,并在停机过程中多次进行调整.最终确定四号轴承轴向振动超标的主要原因是由于该轴承球面与球面座定位销错位,引起定位销卡涩,从而使激振力投影点与轴承几何中心不重合,致使四号轴承轴向振动过大.而发电机转子热不平衡和汽轮机动静碰磨的故障现象是在机组并网带负荷运行过程中四号轴承和二号轴承相继振动过大.经分析判断,主要是由于发电机转子在运行过程中发生了热弯曲,从而造成发电子转子热不平衡,产生较大的轴向振动,进而影响到汽轮机转子并致使动静碰磨造成二号轴承振动过大.最终通过现场动平衡,加配重,才使这一问题得到较好的解决.     

A disc-type magneto-rheologtic fluid damper

A disc-type magneto-rheological fluid damper operating in shear mode is proposed in this paper, which is based on the special characteristics of the magneto-rheological (MR) fluid with rapid, reversible and dramatic change in its rheological properties by the application of an external magnetic field. The magnetic field of the disc-type MR fluid damper is analysed by the finite element method; the controllability of the disc-type MR fluid damper on the dynamic behaviour of a rotor system; and the effectiveness of the disc-type MR fluid damper in controlling the vibration of a rotor system, are studied in a flexible rotor system with an overhung disc. it is shown that the magnetic flux density of the disc-type MR fluid damper in the working areas can significantly change with the applied current in the coil; and that the dynamic behavior of the disc-type MR fluid damper can be varied by the application of an external magnetic field produced by a low voltage electromagnetic coil. The disc-type MR fluid damper can significantly change the dynamic characteristics of a rotor system, provided that the location of the disk-type MR fluid damper is carefully chosen. The disc-type MR fluid damper is a new actuator with good dynamic characteristics for rotating machinery. Project supported partially by the EC BRITE/EURAM program under BRPR-CT97-0544 IMPACT project and State Key Laboratory of Vibration, Shock and Noise, Shanghai Jiatong University     

一种固态聚合物损耗因子测试方法实验研究

宽频带随机振动冲击噪声会激发结构许多谐振峰,利用粘弹阻尼技术隔振、减振和降噪是一项新的技术措施,尤其是对于宽带随机振动和噪声控制具有特殊效果。在实际减振、降噪工程设计中往往需要知道所选用材料的损耗因子,复模量E*的温度谱的测量已经有专门的论述和成熟的方法。根据一个具体的实验研究探讨频率域复模量的测量进而计算材料的损耗因子。     

轨道交通振动中的人工边界问题研究

随着城市化的发展,轨道交通系统导致的振动对环境的影响已日愈引起人们的关注。采用粘性边界条件对振动波在土体中传播问题进行了研究。利用ANSYS软件建立轨道结构和轨下土体的计算模型,将计算得到的轨道结构基础反力的数据输入土体模型,计算土体的动力响应,得到振动波在土体中的传播规律。     

弹簧和振动物体质量对弹簧振动周期的影响

从理论上分析了柱形弹簧振动系统的振动情况，并给出了柱形、锥形弹簧振动系统振动周期相对于弹簧质量、振动物体质量的实验结果。     

Influence of surface treatments on fatigue life of a two-stroke free piston linear engine component using random loading

INTRODUCTION Fatigue durability has long been important issues in the design of a two-stroke free piston linear engine structure (Torres and Voorwald, 2002; Rahman et al., 2005a; 2005b). Durability assessment is traditionally done in the later part of the product development stage when prototypes are available, and heavily re- lied on in confirming ground durability tests. This process is very time consuming and often results in over-design with weight penalties, which is the major obsta…     

Parametrically excited oscillation of stay cable and its control in cable-stayed bridges

This paper presents a nonlinear dynamic model for simulation and analysis of a kind of parametrically excited vibration of stay cable caused by support motion in cable-stayed bridges. The sag, inclination angle of the stay cable are considered in the model, based on which, the oscillation mechanism and dynamic response characteristics of this kind of vibration are analyzed through numerical, calculation. It is noted that parametrically excited oscillation of a stay cable with certain, sag, inclination angle and initial static tension force may occur in cable-stayed bridges due to deck vibration under the condition that the natural frequency of a cable approaches to about half of the, first model frequency of the bridge deck system. A new vibration control system installed on the cable anchorage is proposed as a possible damping system to suppress, the cable parametric oscillation. The numerical calculation results showed that with the use of this damping system, the cable oscillation due to the vibration of the deck and/or towers will be considerably reduced. Project supported by National Natural Science Foundation of China (No. 59978044)     

振膜阻尼式料位器的原理及应用

本文所述的料位器是利用振动阻尼的原理研制的。其外形为圆柱形,它是由振动膜(用金属薄板制作)、驱动器(也是换能器)、电子电路等组成。其特点是:感应面(振动膜)是一个与外壳镶为一体的金属平面。安装使用时即可探入设备内部,也可与设备内壁成一平面,不受湿度、粉尘、污物的影响。经特殊加工可应用于特殊环境,检测不同物料的定点位置。通过在大连第一和第三粮库的烘干塔上使用表明,用振动阻尼的原理制作的料位器,在复杂恶劣的环境中检测粉粒物制的定点位置,性能稳定可非。是现已采用的料位器所不能比拟的。     

Track-position and vibration control simulation for strut of the Stewart platform

Vibrations inherently generated by on-board disturbance sources degrade the performance of the instruments in an on-orbit spacecraft, which have stringent accuracy requirements. The Stewart platform enables both track-positioning and vibration control. The strut of the Stewart platform is designed as a piezoelectric (PZT) element in series with a voice coil motor (VCM) element and a viscoelastic element. The track-positioning system uses a VCM as the main positioning control driver and a PZT as the positioning compensator. The vibration control system uses the characteristics of struts including active and passive control elements to attenuate the vibration. Simulation results indicate that the Stewart platform with the designed struts has good performance in tracking and vibration attenuation with different interference waves.     

Fused empirical mode decomposition and wavelets for locating combined damage in a truss-type structure through vibration analysis

Structural health monitoring （SHM） is a relevant topic for civil systems and involves the monitoring, data processing and interpretation to evaluate the condition of a structure, in order to detect damage. In real structures, two or more sites or types of damage can be present at the same time. It has been shown that one kind of damaged condition can interfere with the detection of another kind of damage, leading to an incorrect assessment about the structure condition. Identifying combined damage on struc- tures still represents a challenge for condition monitoring, because the reliable identification of a combined damaged condition is a difficult task. Thus, this work presents a fusion of methodologies, where a single wavelet-packet and the empirical mode decom- position （EMD） method are combined with artificial neural networks （ANNs） for the automated and online identification-location of single or multiple-combined damage in a scaled model of a five-bay truss-type structure. Results showed that the proposed methodology is very efficient and reliable for identifying and locating the three kinds of damage, as well as their combinations. Therefore, this methodology could be applied to detection-location of damage in real truss-type structures, which would help to improve the characteristics and life span of real structures.