磁悬浮支承转子系统动力学特性计算与分析

介绍一种磁悬浮支承条件下的柔性转子系统临界转速及稳定性计算方法,并对其步骤予以详解.该方法基于传统转子动力学中的改进的传递矩阵法,并结合磁悬浮轴承刚度阻尼系数计算的特点,编制了完整的系统临界转速和稳定性计算程序.最后通过一个计算实例及其实验结果的验证,表明了该计算方法的有效性.     

锅炉给水泵转子动力学参数的一、二阶摄动识别研究

锅炉给水泵的临界转速是非常重要的参数,与结构密切相关。为了准确地计算出给水泵的干临界转速(在空气中)和湿临界转速(在水中),必须知道转轴上的零部件对其弯曲刚度的加强作用。本文利用摄动传递矩阵法,结合实验室的试验数据,对某电站锅炉给水泵转子的动力学参数进行了一阶和二阶摄动识别。给出了给水泵转子上的热装叶轮、轴套对转子刚度产生加强作用的一、二阶摄动识别结果,得到了修正的给水泵转子系统动力学计算模型。由修正模型计算得到的转子系统固有频率与实测的转子系统固有频率吻合良好。指出一阶摄动识别的结果可以满足工程实际的精度要求。     

多油楔轴承支承的转子系统在临界转速与失稳转速之间的半频振动

本文分析了多油楔轴承支承的单质量对称转子系统的非线性振动和稳定特性,研究了临界转速与失稳转速之间半频振动产生原因及其危害性.本文提出的计算方法和计算结果可供设计、计算和应用时参考.     

非稳态非线性油膜力作用下柔性轴裂纹转子的动力特性分析

分析了在动载轴承非稳态非线性油膜力作用下，具有横向裂纹柔性轴Jeffcott转子在非线性涡动影响下的动力特性。通过数值计算表明，在油膜失稳转速前，随着裂纹轴刚度变化比的增大，系统在低转速区域内具有丰富的非线性动力行为，出现倍周期分叉及混沌现象，涡动振幅随转速升高而减小，直到非稳态非线性油膜失稳，在无裂纹转子油膜临界失稳点处发现了类Hopf分叉现象，系统运动由平衡变为拟周期运动；裂纹转子在油膜临界失稳时的系统运动亦为拟周期运动，裂纹转子轴刚度变化对油膜失稳点及油膜失稳之后转子的运动影响不大，转子系统作拟周期运动。     

应用谐波小波提取转子系统动力参数

临界转这是离心压缩机转子系统的主要动力参数之一,尤其高阶临界转速在试车中不易被识别。本文应用谐波小波对转子系统试车振动信号进行分析,对转子高阶临界转速进行了分辨识别,结果令人满意。     

数学机械化在转子系统分析中的应用

以转子－轴承系统中两圆盘转子为研究对象,在计及陀累力矩的条件下,通过对两圆盘转子临界转速与振型参数的分析,对吴消去法在转子动力学研究中的应用做了初步探索,将吴消去法的特征列思想 Maple软件的符号计算功能相结合,实现了对两圆盘转子临界转速与振型参数的解析计算与分析。     

一飞机发动机动力特性分析

确定计算模型时，发动机定子按实际刚度，采用NASTRAN70．0程序对发动机整机进行了动力分析，分析结果与试验进行了比较，吻合度优于美国GE公司计算结果。作者认为造成偏磨故障的原因是弹性环压死，使压气机转子与定子反向平动的第六阶临界转速上升到接近放气阀门关闭时转速所致。根据动力响应计算结果，装配工艺采取措施后，克服了此偏磨故障。     

电机的电磁参数对转子共振的影响

一、引言转子轴系临界转速是一个比较老的问题,但是电机电磁参数对临界转速影响的规律却研究很少,而且电磁参数对电机转子轴系的临界转速有很大影响这个问题的提出,开始是不易被人接受的,但这在我们的实验研究中已被证实了。理论研究和实验结果表明,连续改变不同的电磁参数大小,可以使临界转速逐渐减小,令人感兴趣的是可以大     

挤压油膜阻尼器-滑动轴承转子系统动力学分析与优化设计

为了对挤压油膜阻尼器-转子系统中挤压油膜阻尼器(SFD)的各项参数进行优化设计,使转子系统的动力学性能达到最佳状态,本文综合运用转子动力学和油膜润滑基本理论以及数值分析方法,对SFD-滑动轴承转子系统的灵敏度及动力学优化进行了系统研究。灵敏度分析结果表明:轴承间隙c1、SFD间隙c2、油粘度η对转子系统的一阶临界转速的影响较大;SFD间隙c2、轴承间隙c1、转轴刚度K2对二阶临界转速的影响较大。据此得到优化的设计变量为c1、c2、η、K2,并采用遗传算法对临界转速进行了优化分析;经过优化后,系统的一阶、二阶临界转速差值由原来的510rad/s变为860rad/s,系统动力学性能得到较大改善。本文的优化设计结果可为此类转子系统的设计提供参考。     

Timoshenko转轴模型的若干讨论

本文讨论多自由度转子系统用Timoshenko梁模型取代工程梁模型作动力分析引起的定量修正。对小剪切变形和小陀螺效应情况导出了各阶临界转速和回转形态的摄动样。该解的表达式清晰展现了剪切变形和转动惯量对临界转速的影响,从而为是否采用Timoshenko梁模型提供了定量判据。本文还证明了,除薄壁截面转轴外,对一般转轴,其剪切变形和转动惯量对临界转速有同量级影响,应予同等对待。     

部分充液转子受侧向激励的精确解

本文讨论当部分充液转子受到侧向激励时,作用在转子上的扰动力。首先我们在和转子固连的旋转坐标系中证明了扰动流动是无旋的,然后在分析中把整个流动分解为常涡量的定常流动和无旋的扰动流动。求得了自由面和作用在转子上的合力的显式表达式。可见对于某一给定的充液比,存在两个临界频率。     

考虑密封的悬臂转子系统的裂纹故障分析

以双盘悬臂立式转子-轴承系统为研究对象，建立了系统运动微分方程，并用数值方法分析了在非线性密封力和非线性油膜力作用下的裂纹转子的动力学特性。分析表明，在一定深度裂纹下，转子系统响应随不同角频率比表现出复杂的非线性现象，出现了周期k运动、拟周期运动和混沌运动等多种运动形式。在一定角速度时，工作在远离临界角速度区的转子系统对裂纹非常敏感，而工作在近临界角速度区的转子系统对裂纹不是特别敏感，但是裂纹对它的运动状态影响较大。该研究结果为该类转子-轴承系统的安全运行与故障诊断提供了一定的理论参考。     

大型转子—基础—土壤系统的动力分析

本文对大型汽轮发电机组-基础-土壤系统采用模态综合技术进行了动力分析.用弹性半空间理论建立土壤的模型,基础底板则通过弹性薄板的李兹(Ritz)函数近似解的形式来描述.用三维梁单元来建立基础底板以上的框架结构和转子系统的运动方程.此外,还用模态应变能的相对大小,在这种复杂机械结构系统存在的众多固有频率中,区分出哪些是属于主要为转子系统的固有频率,称为“重要振动固有频率”,以确定系统的临界转速.最后,对引进的一台500MW汽轮发电机组的动力特性进行了分析.     

Statistical moment analysis of multi-degree of freedom dynamic system based on polynomial dimensional decomposition method

The first two moments of the steady-state response of the spring and rotor models are determined by the polynomial dimensional decomposition (PDD) method and the Monte Carlo simulation (MCS) method in this paper. Both the analytical and numerical cases of the PDD method in the dynamical models are provided, and the response of the numerical case is calculated via the harmonic balance and PDD methods. The PDD can describe the amplitude–frequency characteristics of the dynamical models with random variables except the frequencies around the resonant frequencies. These results are shown as a three-DOF spring model with stiffness uncertainty, rotor models with four and nine random variables and nonlinear rotor model with thirteen random variables, respectively. The effects of larger uncertainties and polynomial order are also highlighted. The efficiency of the PDD method is verified via comparing with the MCS method. The applications of the PDD method to the rotor model can provide guidance to further study the rotor systems supported by bearings.     

Study on catastrophic mechanism for rotor drop transient vibration following magnetic bearing failure

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Riccati传递矩阵法在流体动力学中的应用

传统的传递矩阵法在求解管内流体的固有频率时,因奇点干扰出现漏根现象.本文结合气体压缩机管道,运用转子动力学中的Riccati方法计算管内气体的固有频率及振型,从根本上消除了漏根现象.算例表明了本方法的可靠性.     

Quasi-periodic harmonic balance method for rubbing self-induced vibrations in rotor–stator dynamics

A quasi-periodic harmonic balance method (HBM) coupled with a pseudo arc-length continuation algorithm is developed and used for the prediction of the steady-state dynamic behaviour of rotor–stator contact problems. Quasi-periodic phenomena generally involve two incommensurable fundamental frequencies, and at present, the HBM has been adapted to deal with cases where those frequencies are known. The problem here is to improve the procedure in order to be able to deal with cases where one of the two fundamental frequencies is a priori unknown, in order to be able to reproduce self-excited phenomena such as the so-called quasi-periodic partial rub. Considering the proposed developments, the unknown fundamental frequency is automatically determined during calculation and an automatic harmonic selection procedure gives both accuracy and performance improvements. The application is based on a Jeffcott rotor model, and results obtained are compared with traditional time-marching solutions. The modified quasi-periodic HBM appears one order of magnitude faster than transient simulations while providing very accurate results.     

A non-linear study of a cracked rotor

The influence of the presence of transverse cracks in a rotating shaft is analyzed. The paper addresses the influence of crack opening and closing on dynamic response during operation. The evolution of the orbit of the cracked rotor near half and one-third of the first critical speed is investigated. The dynamic response of the rotor with a breathing crack is evaluated by expanding the changing stiffness of the crack as a truncated Fourier series and then using the Harmonic Balance Method. This method is applied to compute various parametric studies including the effects of the crack depth and location on the dynamic of a crack rotor. The evolution of the first critical speed, associated amplitudes at the critical speed and half of the critical speed, and the resulting orbits during transient operation are presented and some distinguishing features of a cracked rotor are examined.     

Operational Modal Analysis of a Helicopter Rotor Blade Using Digital Image Correlation

A novel procedure to perform operational modal analysis on a reduced-scale, 2 m diameter helicopter rotor blade is described. Images of the rotor blade rotating at 900 RPM are captured by a pair of high-speed digital cameras at a sampling rate of 1000 frames per second. From these images, the out-of-plane bending deformation of the rotor blade is measured using Digital Image Correlation, with a spatial resolution of 7.2 mm and an accuracy of 60 μm, or 0.006 % of the rotor radius. Modal parameters including natural frequencies and mode shapes are determined from the bending deformation through application of the Ibrahim Time Domain method. The first three out-of-plane bending modes were identified at each rotational speed and compared to an analytical finite element model of the rotor blade. The experimental and analytical natural frequencies agreed to within 0.2 % in the best case and 10.0 % in the worst case. The experimental mode shapes were also found to closely match the analytical predictions. The results of this study demonstrate the ability of this procedure to accurately determine the modal parameters of rotating helicopter rotor blades.