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。     

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。     

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。     

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.     

考虑定子质量和碰摩面刚度的转子/定子系统碰摩响应的全局动力学特性研究

对考虑定子质量和碰撞面刚度的四自由度转子/定子模型的全局响应特性进行了研究。首先,通过解析方法确定了无碰摩响应的边界,然后,求解了同频全周碰摩解并进行了稳定性分析得到了同频全周碰摩响应的区域。在此基础上,利用非线性动力学分析的数值方法,确定了准周期局部碰摩与反向涡动失稳的边界,由此得出了参数平面内的不同碰摩响应的稳定区域图。进而研究了定子与转子质量比和碰撞面刚度对碰摩全局响应特性的影响,得到了不同碰摩响应共存及随系统参数变化的典型全局响应分岔图。     

具有裂纹-碰摩耦合故障转子-轴承系统的动力学研究

以非线性动力学和转子动力学理论为基础，分析了带有碰摩和裂纹耦合故障的弹性转子系统的复杂运动，在考虑轴承油膜力的同时构造了含有裂纹和碰摩故障转子系统的动力学模型。针对短轴承油膜力和碰摩-裂纹转子系统的强非线性特点，采用Runge-Kutta法对该系统由碰摩和裂纹耦合故障导致的非线性动力学行为进行了数值仿真研究，发现该类碰摩转子系统在运行过程中存在周期运动、拟周期运动和混沌运动等丰富的非线性现象，该研究结果为转子-轴承系统故障诊断、动态设计和安全运行提供理论参考。     

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。     

非线性转子-机匣系统的分岔行为研究

建立了一类非线性转子-机匣系统的碰摩模型.应用数值分析的方法对其进行研究,得到了不同参数变化下系统响应随转速变化的分岔图,分析了系统参数变化对分岔过程的影响,并作出了在相应参数状态和特定转速下的Poincare截面图,揭示系统参数变化对非线性碰摩转子-机匣系统分岔特性的影响.     

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。     

一类油膜转子刚性碰摩模型的动力学研究

本文结合非线油膜力模型和冲量定理，建立了Ｊｅｆｆｃｏｔｔ转子碰摩的刚性约束模型，通过对模型的数值模拟，揭示了转子系统碰摩产生的途径的过程，并 混沌运动发生的条件及其与碰摩的关系。     

Effect of parameters on the rubbing condition of an unbalanced rotor system with initial permanent deflection

A rotor-stator rubbing Jeffcott model of a rotor system with mass unbalance including the mass eccentricity and the initial permanent deflection was set up and the corresponding governing motion equation was derived by d’Alembert principle. Through the analytical method, the rubbing condition was analyzed. Whether the rub would happen and when the rub would happen were well solved. The amplitude of the rotor center was calculated, and the rubbing factor was introduced to determine whether the rub would happen or not for all rotating speeds. Rubbing speeds when rub began to happen were obtained. Parameters such as the mass eccentricity, the initial permanent deflection, damping coefficients, and the phase angle between the mass eccentricity and the permanent deflection were used to analyze their effect on the rubbing condition. Results were obtained and could be used to prevent the rubbing fault or decrease the damage of the rub and diagnose or balance the initial permanent deflection fault.     

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.      

异步进动转子与限位器碰摩试验

利用限位器来限制储能飞轮实验转子的大幅度低频异步进动,设计了转子与限位器碰摩试验装置,研究转子的碰摩振动。分析了转子内表面碰摩力对转子运动的影响。转子与内置式限位器发生稳定的局部碰摩时,转子低频进动幅值不再增加,转子自转速度保持不变。碰摩转子的强迫振动在时域及频域都表现出了复杂性,碰摩冲击作为宽频激励,能够激励出转子-支承系统的第二模态正向进动。     

ANALYTICAL SOLUTION FOR ROTATIONAL RUBBING PLATE UNDER THERMAL SHOCK

提出了热冲击和碰摩故障共同作用下的旋转悬臂板系统动力特性解析解法. 基于变分原理,推导出考虑碰摩力沿宽度方向差异性的薄板系统运动微分方程,将该方程的解分解为热冲击悬臂板准静态解和碰摩薄板热冲击动力解. 通过计算旋转悬臂板的模态特性和温度分布函数,获得了碰摩叶片旋转悬臂板模型的热冲击振动解析解,讨论分析得出热冲击和碰摩故障对薄板振动的影响规律. 研究表明:碰摩振动表现为复杂的多频率耦合振动,高频振动较为显著;热冲击振动表现为简单的低频振动形式,强烈的热冲击导致碰摩薄板趋于低频振动. 碰摩引起的振动形式较热冲击故障更加复杂,更容易引起叶片的破坏. 增大的摩擦系数加剧了碰摩引起的振动,利用减小表面粗糙程度等方法降低摩擦系数,可以达到减小碰摩破坏程度的目的.     

旋转碰摩板热冲击振动的解析法研究

提出了热冲击和碰摩故障共同作用下的旋转悬臂板系统动力特性解析解法. 基于变分原理,推导出考虑碰摩力沿宽度方向差异性的薄板系统运动微分方程,将该方程的解分解为热冲击悬臂板准静态解和碰摩薄板热冲击动力解. 通过计算旋转悬臂板的模态特性和温度分布函数,获得了碰摩叶片旋转悬臂板模型的热冲击振动解析解,讨论分析得出热冲击和碰摩故障对薄板振动的影响规律. 研究表明:碰摩振动表现为复杂的多频率耦合振动,高频振动较为显著;热冲击振动表现为简单的低频振动形式,强烈的热冲击导致碰摩薄板趋于低频振动. 碰摩引起的振动形式较热冲击故障更加复杂,更容易引起叶片的破坏. 增大的摩擦系数加剧了碰摩引起的振动,利用减小表面粗糙程度等方法降低摩擦系数,可以达到减小碰摩破坏程度的目的.      

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.     

Nonlinear dynamics of a Jeffcott rotor with torsional deformations and rotor-stator contact

The dynamics of a modified Jeffcott rotor is studied, including rotor torsional deformation and rotor-stator contact. Conditions are studied under which the rotor undergoes either forward synchronous whirling or self-excited backward whirling motions with continuous stator contact. For forward whirling, the effect on the response is investigated for two commonly used rotor-stator friction models, namely, the simple Coulomb friction and a generalized Coulomb law with cubic dependence on the relative slip velocity. For cases with and without the rotor torsional degree of freedom, analytical estimates and numerical bifurcation analyses are used to map out regions in the space of drive speed and a friction parameter, where rotor-stator contact exists. The nature of the bifurcations in which stability is lost are highlighted. For forward synchronous whirling fold, Hopf, lift-off, and period-doubling bifurcations are encountered. Additionally, for backward whirling, regions of transitions from pure sticking to stick-slip oscillations are numerically delineated.     

Self-excited vibration of the shell-liquid coupled system induced by dry friction

The nonlinear vibration theory and the experimental modal analysis are used in this paper to study the self-excited vibration of the shell-liquid coupled system induced by dry friction. The effect of dry friction stick-slip coefficients and rubbing velocity on self-excited vibration, and the limit cycle and Hopf bifurcation solution of the system are obtained. In particular, it is shown that the phenomenon of 4 point (or 6 point) water droplet spurting of the Chinese cultural relic Dragon Washbasin is the result of the perfect combination of the self-excited vibration induced by dry friction and its special modes, which indicates the significant scientific value of the Chinese cultural relic Dragon Washbasin.     

Rheology and processing of salad dressing emulsions

In order to study the influence that the processing parameters exert on the rheology and stability of salad dressing emulsions, both steady-state shear and oscillatory measurements, as well as droplet size distribution tests were performed. Emulsions containing a mixture of egg yolk and sucrose stearate as emulsifier were prepared using two different emulsification machines, a rotor-stator turbine and a colloidal mill. An increase both in energy input and in the temperature of processing yields higher values of the steady-state viscosity, an increase in emulsion stability and, generally, lower droplet size and lower polydispersity. Furthermore, a plateau region in the loss modulus versus frequency plots appears as the energy input and processing temperature increase. This effect has been analyzed by calculating the relaxation spectra of these emulsions. The results have been discussed taking into account the relationship between several structural parameters, such as interparticle interactions and droplet size distribution, and the rheological response of these emulsions.