Optimal design of a squeeze film damper using an enhanced genetic algorithm

This paper represents that an enhanced genetic algorithm (EGA) is applied to optimal design of a squeeze film damper (SFD) to minimize the maximum transmitted load between the bearing and foundation in the operational speed range. A general genetic algorithm (GA) is well known as a useful global optimization technique for complex and nonlinear optimization problems. The EGA consists of the GA to optimize multi-modal functions and the simplex method to search intensively the candidate solutions by the GA for optimal solutions. The performance of the EGA with a benchmark function is compared to them by the IGA (Immune-Genetic Algorithm) and SQP (Sequential Quadratic Programming). The radius, length and radial clearance of the SFD are defined as the design parameters. The objective function is the minimization of a maximum transmitted load of a flexible rotor system with the nonlinear SFDs in the operating speed range. The effectiveness of the EGA for the optimal design of the SFD is discussed from a numerical example.     

Analytical study on effect of a circumferential feeding groove on unbalance response of a flexible rotor in squeeze film damper

Of recent years, a series of researches have shown that a circumferential feeding groove of squeeze film damper (SFD) has evident effect on fluid film forces in SFD. Therefore, the feeding groove also affects dynamic responses of a rotor in SFD. Present work studies the effect of the feeding groove on unbalance response of a flexible rotor in SFD based on new film force models that include effects of the feeding groove and fluid inertia on dynamic characteristics of the fluid film in SFD. Compared with the published work, unbalance responses predicated under considering effect of the feeding groove on the dynamic characteristics in SFD are small, and rotor speed region for unbalance responses with multiple solutions is different, affecting the stability of a rotor system. And the effect of the feeding groove on the unbalance response is related to action of fluid inertia.     

基于胞映射算法的转子-挤压油膜阻尼器系统多目标优化设计

将挤压油膜阻尼器设计与转子动力学相结合,使用胞映射方法对定心式挤压油膜阻尼器进行多目标优化设计。阻尼器设计参数为阻尼器径向油膜间隙以及定心弹簧刚度。综合考虑了阻尼器的触底现象、转子系统的动力学响应及稳定性,使用多目标优化设计方法以达到抑制转子过临界转速振幅及支撑外传力的目的。针对所得帕累托集合,对所得全局最优解集进行试验验证,结果表明：该最优解集所得设计变量可满足设计需求,可有效地应用到阻尼器的设计过程。     

Analytical study of the effect of a circumferential feeding groove on the unbalance response of a rigid rotor in a squeeze film damper

In recent years, a series of researchers have shown that a circumferential feeding groove of a squeeze film damper (SFD) has an evident effect on the forces of fluid film in SFD. Therefore, the feeding groove also affects the dynamic responses of a rotor in SFD. The present work studies the effect of the feeding groove on the unbalance response of a rigid rotor in a squeeze film damper based on the film force models that include effects of the feeding groove and fluid inertia on dynamic characteristics of the fluid film in SFD. Comparisons with the published work show that the feeding groove increases the orbit radius of rotor whirling and affects the unbalance response of a rotor system. The effect of the feeding groove on the unbalance response is also related to the action of fluid inertia.     

挤压油膜阻尼器-滚动轴承-转子耦合系统的非线性响应分析

为了研究转子系统非线性动力学响应,建立了挤压油膜阻尼器-滚动轴承-转子耦合系统动力学模型。在转子系统模型中,考虑了转子、滚动轴承及挤压油膜阻尼器之间的相互耦合作用,并充分考虑了滚动轴承的间隙、非线性赫兹接触和挤压油膜阻尼器非线性油膜力等。运用数值积分方法分析了转子转速、支承刚度以及挤压油膜阻尼器油膜间隙对系统动力响应的影响,并结合分岔图、频谱图、Poincaré映射图和轴心轨迹图分析了转子系统的非线性动力学响应。结果表明:转子系统当转速较高、支承刚度较大或挤压油膜阻尼器油膜间隙较大时,转子系统容易出现拟周期运动。     

非线性挤压油膜阻尼器-转子系统周期解的分叉及稳定性分析

应用油膜力数据库方法获得非线性油膜力 ,采用非线性动力系统的稳定性及分叉理论对非线性挤压油膜阻尼器 转子系统非线性动力特性、非协调运动及周期解分叉的稳定性进行了分析。揭示了SFD 转子系统在特定参数范围内存在系统亚谐波、概周期和混沌等非协调运动 ,及从同步周期运动分叉发生一系列倍周期运动、最后导致转子 轴承系统混沌运动的过程。数值计算得到了SFD 转子系统发生周期解分叉时的分叉点、分叉图及周期解分叉而失稳的 3种情况 :即鞍结分叉、Hopf分叉及倍周期分叉。最后采用Floquet理论对SFD 转子系统的稳定性进行了分析。研究结果为实际SFD 转子系统的设计和研究提供了理论依据。     

有挤压油膜阻尼器支承的多故障转子系统的非线性特性研究

研究了有挤压油膜阻尼器、转子与静子碰摩和转轴上的横向裂纹等多种非线性因素作用下的转子系统的非线性响应特征。数值研究发现 ,这类转子系统具有丰富的非线性特性 ,三条通向混沌的道路都存在 ,即阵发性通向混沌、倍周期分叉通向混沌和拟周期通向混沌的道路。系统响应的最大振幅曲线包含了大量的跳跃现象 ,发生这些跳跃所对应的参数点与周期解分叉的参数点相重合 (以前已经发现了这种跳跃现象 ,但没有发现与周期解分叉有关系 )。保持不平衡参数在一个小区间内能够使系统抑制多种故障引起的振幅 ,并使系统能够保持稳定的周期一解。较大的挤压油膜阻尼器参数对系统的振动有明显的抑制作用。当裂纹正方向与不平衡方向成反方向时 ,系统具有最小的振动幅度。     

SFD作用下故障转子系统动力学特性及混沌控制

考虑挤压油膜阻尼器(squeeze film damper,简称SFD)作用,研究碰摩故障及不对中-碰摩耦合故障下系统动力学特性及SFD对系统混沌运动控制。基于Lagrange方程,建立不对中-碰摩耦合故障下SFD-转子-滚动轴承系统动力学模型,采用龙格库塔法对模型求解,并利用分岔图、Poincaré图、频谱图等进行对比分析。研究结果表明:合理油膜间隙下的SFD能有效抑制系统非协调响应以及振动幅值,使故障转子系统的混沌运动控制在稳定周期轨道上;过小的油膜间隙会形成很强的非线性油膜支反力,产生非协调频率成分,使稳定周期系统重返混沌状态;随着油膜间隙减小,SFD对不对中故障产生的典型2 X,3 X,4 X和5 X频幅值具有不同影响,其中2 X频幅值变化明显,3 X和4 X频幅值变化微弱,5 X频幅值基本不变。     

The effectiveness of squeeze-film damper bearings supporting flexible rotors without a centralising spring

An investigation has been carried out into the effectiveness of squeeze-film damper bearings incorporated into a flexible rotor system. A method has been devised for comparing the performance of squeeze-film damper bearings which operate without a parallel flexible support or centralising spring (squirrel cage). The model used in this investigation is a relatively simple one in which a rotor mass is lumped at the mid-point of a horizontal flexible shaft and separate rotor masses are lumped at each bearing position. The performance of the squeeze-film damper bearing is expressed in terms of six dimensionless system parameters.The squeeze-film damper bearing performance has been compared, in each case, against the excursion of the rotor centre and the maximum force transmitted to the bearing support, for an exactly similar system with rigid supports. This comparison has led to several interesting conclusions, for example, with a poorly designed squeeze-film damper bearing, the maximum force transmitted to the bearing support can be significantly greater than would have been the case if the damper had not been fitted. Similarly, the reduction in the transmitted force can be very large for certain ranges of parameters, with the squeeze-film damper response remaining constant for a wide range of frequency ratio either side of the (rigid support) critical speed. Further, this damper response is relatively insensitive to a wide variation of some of the system parameters, a trend which supports the past experiences of some aero-engine designers.     

高速转子系统振动控制技术评述

高速转子系统在正常工作过程中必须通过临界转速，此时由于不平衡质量的作用，转子系统会产生共振，导致强烈的振动。降低系统支承刚度以降低临界转速、增大支承阻尼，以减小振幅，这些措施可以抑制系统通过临界转速时的振动幅值和外传力。在振动被动控制技术中，常用弹性支承和挤压油膜阻尼器、金属橡胶减振器、高聚物复合材料减振结构等，降低系统支承刚度，增大支承阻尼，以减小系统振动；在主动控制技术中，通过主动控制挤压油膜阻尼器的参数，改变支承的刚度和阻尼的大小，以控制系统的振动；以及采用形状记忆合金调节器、电磁阻尼器、压电调器等装置，来主动控制系统的振动。目前控制技术仍存在装置结构复杂、性能不稳定等问题，采用粘弹阻尼复合材料与滚动轴承钢外圈复合结构的一体化滚动轴承，足一种有发展前途的研究方向。