转子/定子碰摩响应的全局动力学特性研究

在不考虑自重的转子系统全局碰摩动力响应特性的解析分析基础上,应用数值分析方法,研究了考虑自重的转子系统的全局碰摩动力响应特性。通过大量的数值计算得到了不同参数平面内、不同碰摩响应的稳定区域图。研究表明重力引起的静变形与偏心距之比是决定转子的碰摩响应的变化大小的重要参数,比值越大,转子碰摩响应较不考虑自重的转子碰摩响应的变化越大,会出现多种复杂的响应和共存现象。本研究有助于认清系统参数相互作用对出现不同碰摩响应序列的影响。     

转子与定子碰摩的非线性动力学研究

转子与定子碰摩的动力学行为及其与系统参数关系对旋转机械设计和安全运行至关重要. 转子/定子碰摩系统是一类多参数控制的高维非光滑强非线性系统, 其动力学行为非常复杂. 本文主要从动力学与控制的角度对过去半个世纪有关转子与定子碰摩的研究成果进行归纳和总结, 其目的在于帮助读者尽可能全面系统地了解该问题的研究现状, 提炼尚待解决的问题, 以求推动转子与定子碰摩研究的进一步深入, 并为解决实际问题提供帮助. 本文将首先从碰摩局部模型和碰摩系统模型两个方面对已有的转子/定子碰摩系统的建模进行了简单的划分和归类. 其次, 以典型碰摩非线性响应为主线, 分别介绍了有关同频碰摩响应、谐波周期碰摩响应、准周期局部碰摩响应、干摩擦自激反向全周涡动响应、碰摩的全局响应行为以及碰摩响应的分岔与混沌方面的研究成果. 接下来讨论了在主被动抑制碰摩振动方面取得的结果. 最后, 给出结论并提出有待进一步研究的问题.     

系统参数对碰摩转子稳态响应的影响

本文基于线性碰摩力模型,分析了转定子存在偏心时柔性JEFFCOTT转子的碰摩响应。通过数值仿真,揭示了转子碰摩响应与系统参数之间的定性关系,指出较小的定子刚度、较大的系统阻尼有利于抑制转子的混沌振动。     

转子有碰摩和支承松动故障时的非线性特性研究

以具有支承松动的Jeffcott转子为研究对象，并考虑到转子系统转子和定子间的碰摩现象，分析了支承松动和碰摩对转子系统刚度的影响，建立了转子系统振动的微分方程，并用数值方法分析了其非线性动力学特性。数值分析表明，转子在碰摩和支承松动这两种非线性因素的作用下，表现出复杂的非线性行为。     

基于Hertz接触理论的转子碰摩模型

对转子系统转、定子碰摩故障的过程进行了研究，建立了一个基于Hertz接触理论的转子非线性碰摩模型。通过对不同碰摩模型进行理论分析及数值仿真的对比研究表明：基于Hertz接触理论的非线性碰摩模型能更深刻地反映转、定子碰摩过程的本质特征，具有较好的实用价值。     

转子-机匣局部碰摩的分叉与混沌行为分析

研究了转子-机匣系统发生碰摩时的分叉与混沌行为,分析了转子机匣频率比与刚度比、偏心质量等参数对系统分叉与混沌特性的影响.当转子机匣系统发生碰摩时除了通过倍周期、阵发性和拟周期分叉进入混沌外,还发现了孪生叉形分叉现象,呈现出非常丰富的动力学行为.     

非线性碰摩力对碰摩转子分叉与混沌行为的影响

研究了具有非线性碰摩力的转子局部碰摩的分叉与混沌运动,利用计算机仿真对某发动机转子的碰摩故障进行了数值模拟,讨论了转子系统参数的变化对转子混池运动状态的影响,并与碰摩实验结果进行了比较,发现了具有非线性碰摩力的转子局部碰摩转子系统的各种多周期运动和混沌运动及其演变过程。     

某电厂转子碰摩机理分析

我国某电厂的２００ＭＷ汽轮发电机组因严重碰摩而被迫停机。本言语建立了转子碰摩的力学模型，用数值分析的方法研究了产生碰摩机理，指出高倍频振动分量的出现是判断产生 摩的必要条件，可依之进行了转子碰摩预测和诊断。     

一类刚性约束转子碰摩的非光滑分析

本文建立并研究了一类与定子几何不对中的转子刚性碰摩模型，通过建立碰摩映射，将对不连续流非光滑系统的研究转化为对映射的研究。文中从几何角度分析了转子碰摩的机理并用数值方法得取了该类子碰摩的分岔和混沌等非一性结果。     

碰摩转子系统的非光滑分析

通过建立转子系统碰摩的Ｐｏｉｎｃａｒｅ映射,将对非光滑碰摩系统的研究转化为对Ｐｏｉｎｃａｒｅ映射的分析,文中主要对转子碰摩当中一类特殊的运动形式－单点碰摩下的擦边现象者了详细研究。从序列的极限理论出发分析了该映射的周期不动点的稳定性及其吸引域,得到了转子系统在接近擦边运动时解随系统参数变化的分岔情形。     

Analytical study of nonlinear synchronous full annular rub motion of flexible rotor–stator system and its dynamic stability

The nonlinear synchronous full annular rub motion of a flexible rotor induced by the mass unbalance and the contact-rub force with rigid and flexible stator is studied analytically. The nonlinear property is due to the dry friction force between stator and rotor. The exact solutions of the synchronous full annular rub motion and its run speed regions are obtained. The stability of the synchronous full annular rub motion is discussed analytically. The stability criterion and the stability regions of the synchronous full annular rub motion are obtained. A simplified approximate criterion formula for dynamic stability is also derived under the conditions of large impact stiffness, small damping and small friction. The simplified criterion formula can be used conveniently in engineering and matches the real situations of industry.     

Determination of the global responses characteristics of a piecewise smooth dynamical system with contact

In this paper the global response characteristics of a piecewise smooth dynamical system with contact, which is specifically used to describe the rotor/stator rubbing systems, is studied analytically. A method to derive the global response characteristics of the model is proposed by studying each piece of the equations corresponding to different phases of the rotor motion, i.e., the phase without rubbing, the phase with rubbing and the phase of self-excited backward whirl. After solving the typical responses in each phase and deriving the corresponding existence boundaries in the parameter space, an overall picture of the global response characteristics of the model is obtained. As is shown, five types of the coexistences of the different rotor responses and deep insights into the interactive effect of parameters on the dynamic behavior of the model are gained.     

Dynamic characteristics of a rub-impact rotor-bearing system for hydraulic generating set under unbalanced magnetic pull

Electromagnetic and mechanical forces are main reasons resulting in vibrations in hydraulic generating set. The non-symmetric air-gap between the rotor and stator creates an attraction force called unbalanced magnetic pull (UMP). The UMP can produce large oscillations which will be dangerous to the machines. In this paper, the nonlinear dynamic characteristics of a rotor-bearing system with rub-impact for hydraulic generating set under the UMP are studied. The rubbing model is established based on the classic impact theory. Through the numerical calculation, the excitation current, mass eccentricity, stiffness of shaft and radial stiffness of stator are used as control parameters to investigate their effect on the system, by means of bifurcation diagrams, Poincaré maps, trajectories and frequency spectrums. Various nonlinear phenomena including periodic, quasi-periodic and chaotic motions are observed. The results reveal that the UMP has significant influence in the response of the rotor system that the continuous increase in the excitation current induces the alternation of quasi-periodic and chaotic motions, the co-occurrence of oil whip and rub in a wide excitation range aggravates the vibration and leads to the instability of the system. In addition, the large eccentricity and radial stiffness of stator, as well as the small stiffness of shaft may lead to the occurrence of full annular rubbing while increasing the stiffness of the shaft can play an important role of suppressing the chaotic motion, reducing the vibration and improving stability of the system.     

Improvement of rotor performance under rubbing conditions through active auxiliary bearings

This paper develops a new concept to enhance the adaptive capability of rotating machinery to the rubbing conditions through active auxiliary bearings. To demonstrate the feasibility of this idea, a model with a Jeffcott rotor and an active auxiliary bearing, which accounts for both the dynamics of the auxiliary bearing and the deformation on the contact surface, is investigated. The dynamics and the stability of the non-linear piecewise-smooth passive rotor/stator (auxiliary bearing) system are first studied. Then, two control approaches are proposed with the aim to reduce the rubbing severity during the rotor/stator rubbing. It is shown that by using an optimal controller, the harmful heavy rubbing between the rotor and the stator can be well stabilized to the mild light rub through the active auxiliary bearing, and the already established rotor-to-stator rubbing can even be released by using PD-controllers.     

Stability Analysis of Sliding Whirl in a Nonlinear Jeffcott Rotor with Cross-Coupling Stiffness Coefficients

An analytical study is carried out on the stability of the fullannular rub solutions of an externally excited, modified Jeffcott rotorwith a given rotor/stator clearance and cross-coupling influences. Theobtained analytical stability conditions provide an opportunity for abetter understanding of the dynamical phenomena of rotor/stator systemswith rubs, such as jump phenomena and the transition between periodicand quasi-periodic full rub responses as well as between the fullannular rubs and the partial rubs. A systematic study on the influenceof the system parameters on these phenomena is carried out. It is foundthat the simultaneous presence of the coefficient of friction and thecross-coupling stiffness coefficient with a proper value may benefit thedynamics of the rotor/stator system with rubs.     

油膜支承转子系统动静件碰摩特征分析

以支承在油膜轴承上的Jeffcott转子为对象，分析了油膜力对碰摩转子动力学行为的影响。通过与刚支情形对比，发现油膜力是耦合作用于碰摩转子系统，有时能够抑制振动，有时却加剧振动。因此实际转子碰摩故障诊断过程中，必须在充分考虑支承情况的基础上建立合理的非线性动力学模型，才能为实际转子系统的碰摩故障分析提供必要的理论依据。     

航空发动机整机耦合动力学模型及振动分析

面向航空发动机整机振动, 建立了航空发动机转子-滚动轴承-机匣耦合动力学模型. 该模型具有如下特点: (1)考虑转子、滚动轴承及机匣之间的耦合作用; (2)考虑了实际航空发动机的弹性支承及挤压油膜阻尼效应; (3)将转子考虑为等截面自由欧拉梁模型, 运用模态截断法进行分析; (4)考虑了滚动轴承间隙、非线性赫兹接触力以及变柔性VC(Varyingcompliance)振动; (5)考虑了转子与机匣之间的碰摩故障. 运用数值积分方法研究了航空发动机的整机振动规律, 包括: 滚动轴承VC振动分析、弹性支承刚度对耦合系统临界转速的影响、转轴模态截断阶数NM对系统响应的影响分析、挤压油膜阻尼器参数对系统响应的影响分析、突加不平衡的瞬态响应分析以及转静碰摩故障特性分析等.