200 MW汽轮发电机组转子-轴承系统非线性稳定性研究

将一种降维计算方法应用到大型转子-轴承系统非线性稳定性分析中,提出将计算得到的转子发生油膜振 荡的转速作为判断系统非线性稳定性的准则。针对200 MW汽轮发电机组多跨转子-轴承系统建立了具有608自 由度的非线性振动方程,基于固定界面模态综合法对其降维,使其自由度数降到30,然后采用Newmark逐步积 分法对降维后的系统振动方程进行数值计算,在保证精度的前提下,显著提高了计算分析的效率。利用该降维计 算方法模拟出了油膜振荡现象的典型特征和发生油膜振荡的转速,并着重计算分析了发电机转子前轴承轴颈的失 稳转速随转子的偏心距、轴承长径比、间隙比和润滑油粘度的变化规律,研究结果为定性分析200 MW汽轮发电 机组机转子-轴承系统的稳定性提供了理论依据。     

复杂转子-轴承系统非线性动力学特性分析

针对现有方法在求解复杂转子-轴承系统非线性动力学特性时的不足,提出了基于动网格技术的计算流体力学和转子动力学相结合的流固耦合计算方法。首先建立滑动轴承轴心轨迹的运动方程,然后采用动网格技术对滑动轴承流场进行非线性瞬态计算,得到动态载荷作用下转子-轴承系统的轴心轨迹。最后,通过对某复杂转子-轴承系统非线性动力学特性的分析对本文方法进行了验证。结果表明,方法能够准确分析复杂转子-轴承系统非线性动力学特性并可求得其轴心轨迹。     

转子-轴承-密封耦合系统的非线性振动特性研究

结合短轴承非线性油膜力模型和Muszynska密封力模型,运用数值积分方法分析了转子-轴承-密封耦合系统的非线性动力学特性,针对转速对耦合系统动态响应的影响进行了仿真计算,并利用转子中心分岔图、轨迹图、Poincare映射图、功率谱图分析了耦合系统的非线性动力学特性.理论分析表明:随着转速的变化,耦合系统呈现复杂的动力学行为,产生了包括单周期、3倍周期、拟周期等振动现象.     

Jeffcott转子-轴承系统的非线性动力学特性分析

为了深入地研究转子-轴承系统的分岔规律,揭示转子系统丰富的非线性动力学行为,采用短轴承非稳态非线性油膜力的一般数学模型获得圆柱轴承的非线性油膜力表达式。在一定参数条件下,采用非线性动力学理论和方法,对刚性Jeffcott转子系统的动力学特性进行了分析。通过计算得到了系统的分叉图、时间历程、轴心轨迹、相图及Poincare映射图。计算结果表明-在特定的参数域内系统存在丰富的非线性动力学行为。该方法收敛速度快、精度高,为定性控制转子-轴承系统的稳定运行状态提供了理论依据。     

弹性转子—轴承系统的非线性动力学研究

以转子动力学和非线性动力学理论为基础,针对非线性转子－轴承系统的具体特点,建立了采用短轴承模型的弹性转子－轴承系统模型,并用数值积分和庞加莱映射方法对其在某些参数域中进行了非线性振动研究,得到了系统在某些参数域中的分叉图,庞加莱映射和随转速变化的3维谱图,计算结果显示,系统有可能发生混沌运动。对系统动力学特性随革些参数变化时的非线性特性进行了分析,直观显示了参数变化对系统动力学特性的影响,为该类转子－轴承系统的设计提供了参考。     

轴承预紧力作用下电主轴系统动力学特性研究

考虑轴承预紧力这一非线性因素对轴承支承动态刚度的影响,建立了磨削电主轴系统动力学模型。在转子系统中考虑由于转子质量偏心而产生的不平衡力,采用数值积分方法研究电主轴转子系统在轴承不同预紧力、不同转速下系统的非线性动力学行为。结果表明:轴承预紧力是影响电主轴转子系统非线性动力学特性的一个重要因素,合理的选择转子系统的工作参数,可提高系统的稳定性。     

基于非线性度的滑动轴承-转子系统支承松动状态评估

基于振动信号非线性度建立了滑动轴承-转子系统支承松动状态评估方法。针对滑动轴承-转子系统支承松动故障,运用转子动力学、机械振动等理论分别建立转子系统存在支承松动故障与无故障时的非线性动力学模型,其中松动间隙产生垂直方向弹性力采用非线性项进行描述。根据非线性度的定义,对支承松动系统动力学模型中滑动轴承油膜力采用8个系数动态特性线性化,松动故障弹性力部分采用泰勒展开进行近似,得到线性近似系统动力学模型。比较存在支承松动转子系统动力学模型与线性近似动力学模型的动力学行为差异,结合MATLAB数值积分方法,计算在不同松动间隙大小情况下滑动轴承-转子系统动力学行为非线性度,建立非线性度与松动程度之间的关系,直观地反映出支承松动故障对滑动轴承-转子系统动力学行为的影响程度,为转子轴承系统的支承松动状态评估提供一种新的思路。     

高速滚动轴承-转子系统时变轴承刚度及振动响应分析

高速滚动轴承广泛应用于机床主轴、航空发动机等转子系统中。在复杂运行工况下,滚动轴承的刚度表现出强烈的时变特性和非线性特性,往往是系统非线性的主要根源。考虑离心力、陀螺力矩、轴承内圈离心膨胀和热变形等因素,建立高速滚动轴承力学模型,计算轴承的时变刚度。将滚动轴承非线性模型与转子有限元模型集成,建立滚动轴承-转子耦合系统动力学模型。以FAG角接触球轴承(HCB7012E)为例,分别计算静载荷作用下的内外圈轴向、径向相对位移,并与舍弗勒轴承分析软件BearinX?的计算结果进行比较,验证了模型对静态位移仿真的精度。在不同轴承预紧状态下,仿真滚动轴承-转子系统在不平衡激励下的振动响应,并与试验结果比较,验证了模型仿真系统动态响应的精度。利用一个背对背安装的角接触球轴承-转子系统,研究在静载荷、不平衡载荷激励作用下滚动轴承刚度的变化规律,并计算时变轴承刚度作用下转子的时域振动响应及频域特征,为高速滚动轴承-转子系统设计、动力学分析与故障诊断提供依据。     

600MW汽轮机组大型转子-轴承系统非线性动力学分析

针对600 MW汽轮发电机转子-轴承系统,采用ANSYS计算了转子固有频率,分析其振动特性。建立了具有1 016个自由度的非线性振动方程,并基于固定界面模态综合法降维至34个自由度。分析了转子稳定性随转子偏心距、轴承间隙和润滑油动力黏度的变化规律,并利用三维谱图分析了不平衡力和重力对油膜失稳的影响。     

柔性转子-轴承系统非线性动力学行为分析

运用非线性动力学对柔性转子-轴承系统进行了分析,考虑了Newmark法在计算时间步长内产生的影响计算精度和计算稳定性的计算扰动效应,并将其改进形成一种有效的求解动力学周期响应的方法。将该方法的计算结果与Runge-Kutta法的计算结果进行了对比,结果表明该方法精度较高。运用Floquet分岔理论分析了系统周期运动的稳定性及其分岔行为,数值结果展现系统具有周期运动、准周期运动等非线性现象。     

不对称润滑对碰摩转子-轴承系统的动力学影响

在考虑非线性油膜力的基础上,建立了具有碰摩故障的转子-轴承系统的动力学模型。用数值方法研究了在非线性油膜力作用下具有碰摩故障的转子系统的动力学特性,并研究了当改变其中一个支承轴承润滑油的粘度时,转子系统的动力学特性。研究发现,随着一轴承润滑油粘度的降低,转子系统亚临界角速度区的混沌区域和拟周期区域扩大了。该结果为采用不同粘度润滑剂的转子-轴承系统的优化设计、安全运行和故障诊断等提供了一定的理论参考     

Application of computational fluid dynamics and fluid structure interaction techniques for calculating the 3D transient flow of journal bearings coupled with rotor systems

Journal bearings are important parts to keep the high dynamic performance of rotor machinery. Some methods have already been proposed to analysis the flow field of journal bearings, and in most of these methods simplified physical model and classic Reynolds equation are always applied. While the application of the general computational fluid dynamics (CFD)-fluid structure interaction (FSI) techniques is more beneficial for analysis of the fluid field in a journal bearing when more detailed solutions are needed. This paper deals with the quasi-coupling calculation of transient fluid dynamics of oil film in journal bearings and rotor dynamics with CFD-FSI techniques. The fluid dynamics of oil film is calculated by applying the so-called ’’dynamic mesh’’ technique. A new mesh movement approach is presented while the dynamic mesh models provided by FLUENT are not suitable for the transient oil flow in journal bearings. The proposed mesh movement approach is based on the structured mesh. When the journal moves, the movement distance of every grid in the flow field of bearing can be calculated, and then the update of the volume mesh can be handled automatically by user defined function (UDF). The journal displacement at each time step is obtained by solving the moving equations of the rotor-bearing system under the known oil film force condition. A case study is carried out to calculate the locus of the journal center and pressure distribution of the journal in order to prove the feasibility of this method. The calculating results indicate that the proposed method can predict the transient flow field of a journal bearing in a rotor-bearing system where more realistic models are involved. The presented calculation method provides a basis for studying the nonlinear dynamic behavior of a general rotor-bearing system.     

不同轴承支撑下碰摩转子系统的动力学特性

研究了不同类型轴承支撑下的转子碰摩故障振动特征。首先,采用了计及回转效应、剪切效应及横向扭转的梁单元建立了实验装置转子的有限元分析模型;然后,通过二维计算流体力学方法得到不同类型轴承的动力学参数;最后,在此基础上,结合非线性动力学理论,分析比较了转子在圆柱轴承、可倾瓦轴承等5种轴承支撑下的碰摩非线性动力学行为。研究结果表明：在椭圆轴承、五瓦轴承和四瓦可倾瓦轴承支撑下,系统主要表现为同频周期运动;而对于圆柱轴承和四油叶轴承支撑,系统会出现较复杂的运动。本研究工作是对之前转子碰摩非线性动力学研究的扩展,所得计算结果可为大型高速旋转机械系统动态设计制造和碰摩故障的诊断和控制提供理论参考。     

Nonlinear coupled dynamics of flexible blade-rotor-bearing systems

The nonlinear dynamic behavior of a rotor-bearing system with interaction between blades and rotor is addressed in this paper. Using the Lagrange equation, a time-dependent nonlinear model of a flexible blade-rotor-bearing system is established, in which the rotor is supported by journal bearings and the blades are modeled as pendulums in order to analyze the dynamic coupling between the elastic blades and the flexible shaft. To emphasize the gyroscopic effect of the rotor, the disk is assumed to be located at an arbitrary position of the shaft. Employing the orthogonal transformations, the 1-nodal diameter equations of motion of the blades, which are coupled with the dynamic equations of the rotor, are decoupled with other equations of the blades. Then the parametric excitation terms in the blade-rotor-bearing system are simplified in terms of periodic transformations. The dynamic equations with nonlinear oil-film forces are numerically solved using the Runge-Kutta method. Bifurcation diagrams, three-dimension spectral plots, and Poincaré maps are employed to analyze the dynamic behavior of the system. The numerical results show that the nonlinear dynamic behavior of the system varies with the increase of the rotational speed. And the effect of the nonlinear vibration of the rotor on the blade vibration is discussed.     

Chaos of rub-impact rotor supported by bearings with nonlinear suspension

The nonlinear dynamic analysis of the rotor-bearing system is studied in this paper and is supported by oil-film short bearings with nonlinear suspension. An observation of a nonlinearly supported model and the rub-impact between rotor and stator is needed. Therefore for more precise analysis of rotor-bearing systems, the rub-impact between rotor and stator is also proposed in this paper. The displacements in the horizontal and the vertical directions charactering the theoretical model of the system are considered with non-dimensional speed ratio. Inclusive of the analysis methods of the dynamic trajectory, the power spectrum, the Poincaré maps and the bifurcation diagrams are used to analyze the behavior of the rotor centre and bearing centre in the horizontal and vertical directions under different operating conditions. The maximum Lyapunov exponent analysis is also used in this study to identify the chaotic motion. It is concluded that the trajectory of rotor centre and bearing centre have undesirable vibrations. Especially at s=5.6, the rotor centre is at chaotic motion but the bearing centre is still at quasi-periodic motion. With the analysis of the dynamic behavior of these operating conditions, the theoretical and practical idea for controlling rotor-bearing systems and optimizing their operation can be more precise.     

Investigation on the stability of periodic motions of a flexible rotor-bearing system with two unbalanced disks

The stability of periodic motion of a rotor-bearing system with two unbalanced disks is analyzed based on a multi-degree of freedom (M-DOF) finite element model. Nonlinear effects of supporting oil-film and inertia distributions as well as shearing effect are taken into account. Focusing on the more realistic FE method to study the stability of nonlinear rotor-bearing system with the influence of the eccentricity phase, the stability calculation of the M-DOF FE model is done by using the combination of Shooting method and Newmark method. Experiments with a rotor-bearing test rig (two disks on a shaft with two bearings) are then performed and results are presented. It is found that typical instability characteristic is successfully produced. Through comparisons between calculated results and measurements, it is shown that the combination of Shooting method and Newmark method in studying the M-DOF rotor-bearing system is useful, especially for the complex rotor-bearing system. In addition, altering eccentricity phase of the two disks can significantly influence instability type and speed. When the two disks are out of phase, the occurring of oil whip is restrained effectively. It is suggested that a careful examination should be made in modeling more complex non-linear rotor-bearing system. Some response curves are shown to compare the beam motions at different load velocities.     

动静压轴承支撑高速主轴系统基本性能分析

以高速主轴水润滑动静压轴承为基础,在双动静压轴承支撑主轴系统实验平台上,分析转速、供水压力、载荷等基本运行参数对系统基本性能的影响,并采用不平衡轴承质量法识别了系统支撑轴承的动特性系数。结果表明:轴承-转子系统静态刚度随供水压力和载荷的增大而增大;流量随供水压力升高而增大,而随转速变化较小;利用不平衡轴承质量法识别系统支撑轴承的动特性系数与理论一致性。     

涡轮泵流体静压轴承设计及性能特性分析

针对流体静压轴承在液体火箭发动机涡轮泵中的设计和应用,以现有的滚动轴承支承的涡轮泵转子为应用对象,提出流体静压轴承的参数设计思路,采用粒子群优化算法设计得到支承刚度最大化的轴承结构参数组合,并计算分析所设计轴承的性能以及轴承-转子系统的动力学特性。分析表明：优化设计得到流体静压轴承的承载力和支承刚度可以满足要求,但轴承总流量达泵流量的21%,这会显著降低涡轮泵的总体效率;仅将滚动轴承改为流体静压轴承,而不改变其他结构或布局,转子的稳定性不能满足要求;涡轮泵流体静压轴承转子系统设计时应尽量将轴承布置在转子位移较大的位置,以充分发挥其阻尼作用。     

不对称润滑工况下碰摩转子-轴承系统的动力学分析

在考虑非线性油膜力的基础上，建立了具有碰摩故障的转子一轴承系统的动力学模型。研究了具有碰摩故障的转子在两支承轴承使用相同和不同粘度润滑剂时的动力学行为，发现随着一端轴承润滑油粘度的降低，转子的混沌区域和拟周期区域扩大了。该结果为采用不同粘度润滑剂的转子一轴承系统的故障诊断提供了依据。