特高压输电系统次同步谐振分析

加装串补装置可提升高压输电线路的输送能力,但这也是系统发生次同步谐振的诱因之一。以某实际电力系统为例,采用解析法对汽轮发电机组轴系扭振的模态进行分析,对不同频率下系统等值阻抗进行扫描,研判发生次同步谐振的风险;并基于时域仿真,对不同工况下系统运行情况进行验证,结果表明：汽轮发电机组轴系扭振模态与解析法的计算结果吻合;机组轴系扭振的剧烈程度及振荡模态会随故障不同而改变;任何工况下,发电机轴段均不会发生轴系扭振。     

次同步谐振对汽轮发电机组轴系扭振冲击的研究

本文研究了在电力系统发生次同步谐振时汽轮发电机组轴系的扭振特性。建立了机电统一模型,进行了数字仿真研究:并利用动模机组和模拟电网进行了一系列同步扭振试验。研究表明,次同步谐振对轴系的影响与机组特性参数和运行参数有密切关系。     

5kW扭振模拟机组轴系扭振试验研究

本文在介绍TVAP—M扭振测试分析软件包的基础上,着重介绍了应用TVAP—M在5kW汽轮发电机组轴系扭振模拟机组上进行的一系列机电互作用扭振试验.通过试验确定了该模拟机轴系的扭转固有特性.试验表明:在低频情况下,变频励磁激振是一种行之有效的激振方式.最后利用串补电容方式对机电互作用下的次同步谐振进行了探讨.     

2.8T柴油机轴系扭振特性测试与分析

利用比利时LMS公司生产的噪声振动测量系统,对某国产新型柴油机进行了全负荷加速工况下的曲轴扭振特性测试,同时采集曲轴飞轮端和自由端的转速信号,通过对全转速范围内加速工况下的扭振时域波形和各谐次扭振幅频特性曲线的综合分析,得出了曲轴前端与飞轮端的扭振特性,并进行了前后端曲轴轴系的相对扭振特性分析,测试结果表明,轴系的扭振幅值满足工程要求,扭振减振器起到有效地抑制扭振的作用。     

基于有限单元法发动机曲轴橡胶扭转减振器分析

发动机曲轴轴系扭转振动不仅影响整机的运行安全,也是NVH分析的重要内容。针对某直列四缸发动机曲轴轴系进行研究,采用多种方法对扭转振动特性进行分析,分为自由振动、约束模态、激励强迫谐振等工况;在此分析的基础上,对橡胶减振器的性能参数和结构参数进行分析设计,并对安装扭转减振器后,曲轴轴系的扭转振动幅频特性进行分析,以检验减振效果。结果可知：理论分析、有限元模型分析表明,曲轴轴系扭转振动的前三阶固有频率为阶次328Hz、789Hz、2029Hz;有限元分析结果略大,但二者数值基本一致;在发动机轴系的二阶自振频率值处出现了较大的共振振幅;在主谐次下出现的最大振幅值要比次主谐次下的大一个数量级;加装扭振减振器的曲轴轴系,无论是主谐次激振力矩还是次主谐次激振力矩下,振幅值在二阶自振频率附近处都已经基本消失;而二阶振幅的最大值处虽然改变位置,最大幅值下降程度也很明显;表明扭转减振器的减振效果比较明显,为此类设计提供参考。     

涡轮增压器转子系统三维动力学特性分析

针对涡轮增压器转子系统,考虑陀螺力矩、转子叶轮刚度和转轴抗扭刚度的影响,建立三维分析模型,利用有限元法进行转子系统动力特性分析.开展转子系统临界转速的分析,通过传递矩阵法模型和有限元梁单元模型校验三维模型的有效性,结果表明集总质量法在简化带有较厚轮盘的转子结构时,会减小转子结构的抗弯刚度.开展转子系统不平衡质量动力响应分析,结果显示,转子系统存在着弯扭组合振动,且弯扭组合振动表现为一种非同步的半频激振现象;随着转速的升高,转子系统的弯扭组合振动现象越趋明显;在弯扭组合振动频率附近,转子振动形式为弯扭组合振动;而在其他涡动频率下,转子振动形式为弯曲振动.     

大型水轮发电机组弹性轴系由电磁参数激发的弯扭耦合振动的研究

利用弹性体非线性振动的能量法研究水轮发电机组弹性轴系在电磁参数激发下弯扭耦合振动规律。揭示了弯曲振动能够激发扭振,两者相互耦合。利用奇异性理论在物理参数空间对共振的分叉形式进行分析,找到抑制共振发生的参数区域,为机组工程设计和安全运行提供理论依据。在弯扭耦合情况下,通过数值分析所得弯曲振动响应的理论结果与实测结果相符。     

混合动力挖掘机轴系扭振测试

以6t混合动力挖掘机动力系统相关技术参数为设计依据,建立了混合动力挖掘机轴系扭振测试实验台,提出了轴系扭振测试方案．对不同油门开度下轴系的最大扭转角进行了实验测试和分析．实验结果表明：扭振是轴系的固有特性;不同转速下轴系的最大扭转角均发生在2f0（f0为混合动力轴系的工作转频）处,表明引起轴系扭振的激励频率为2f0;不同转速下轴系扭振的激励频率主要集中在0．5,0～2．0f0,表明高频激励对轴系的扭振贡献很小;混合动力系统轴系扭振产生的主要激励源是柴油机,而不是电动机．     

某直升机传动系统旋翼轴扭振计算及优化设计

直升机传动系统旋翼轴系振动是影响其运行可靠性的重要因素,为了提高某共轴反转双旋翼传动系统旋翼轴系扭振安全裕度,在考虑轻量化设计的前提下,通过改变轴段直径尺寸或改变激励频率,使得扭振固有频率与激励频率错开,达到避免共振的目的,实现了轴系扭振调频的优化设计。优化后的轴系扭振安全裕度达到10%以上,扭振特性得到了有效改善。其计算与优化方法对直升机传动系统旋翼轴系的改进设计具有一定的指导意义。     

汽轮发电机轴系扭振固有频率的优化及其工程应用

分析了轴系结构参数的变化对扭振固有频率的影响，利用逐步线性化方法对轴系扭振频率进行优化。根据此优化方法合理地调整轴系结构参数，可以使轴系振动频率分布达到优化，从而获得最佳动力特性。最后，本文对某扭振特性不良的国产３００ＭＷ机组进行了轴系刚度直径敏感度计算及分析，并在此基础上用优化方法调整联轴节约的刚度，使扭振特性得以改善，提高了机组的稳定性。     

Jeffcott裂纹转子弯扭耦合振动特性分析

以重力决定的开闭裂纹模型为研究对象，导出了固定坐标系下该模型的刚度扭阵，建立了裂纹转子弯扭耦合振动微分方程，并对转子裂纹的升速瞬态响应和影响因素进行了计算机仿真研究。结果表明：升速过程中，弯振存在1／3阶和1／2阶亚谐共振现象，扭振出现1／2阶亚谐共振；在弯扭左耦合区，出现弯扭耦合共振；在亚临界转速区，存在1X，2X和3X等倍频分量的弯振和扭振；影响弯扭耦合振动特性的因素很多，包括裂纹刚度、裂纹夹角、质量偏心和阻尼等。     

直齿圆柱齿轮传动系统振动的动力学模型

通过对由齿轮、轴与轴承所组成的齿轮传动系统中弯曲振动、扭转振动和横向振动问题的分析,并考虑到齿轮质量偏心和轮齿啮合摩擦力对系统振动的影响,应用拉格朗日方程,建立了一对渐开线直齿轮传动系统振动的数学模型。得到了15自由度的时变系数振动微分方程组,为系统的振动分析奠定了基础。并给出一特定传动条件下的动态响应数值计算结果。     

直齿圆柱齿轮传动系统的振动分析

研究了由齿轮、轴和轴承所组成的齿轮传动系统的扭转振动和横向振动,建立了该系统的振动数学模型和运动方程式,用模态分析法和状态空间法相结合的方法求解了该系统的多自由度时变非线性微分方程,求出了系统的动态响应、齿轮动载系数和振动加速度均方根值,为系统的动态分析做好了理论准备。     

基于瑞利法的内燃机曲轴扭纵耦合振动

采用瑞利法对高速内燃机曲轴扭纵耦合振动进行了研究。将内燃机曲轴等效为连续分布阶梯轴模型,根据当量轴段以及集中质量的动能和势能关系,通过拉格朗日方程分别建立轴系扭振模型和纵振模型。根据刚度耦合原理,并考虑轴系强迫激励进而建立了扭纵耦合强迫振动模型。采用谐次分析法对模型求解后,通过与采用三维振动测量装置对某直列四缸柴油机曲轴自由端的振动信号进行实际测量所得到的结果进行比较,可以发现,扭振和纵振与实际测量的结果在各主要谐次都保持相当的一致。     

Intense flexural and torsional waves in an elastic bar

The paper considers the problems of propagation of an intense flexural wave in a twisted bar and an intense torsional wave in a bar with an initial curvature in the context of a geometrically nonlinear model of flexural and torsional vibrations of an elastic bar.     

DESIGN AND ANALYSIS OF NOVEL ACTIVE ACTUATOR TO CONTROL LOW FREQUENCY VIBRATIONS OF SHAFT SYSTEM

Aiming at providing with high-load capability in active vibration control of large-scale rotor system, a new type of active actuator to simultaneously reduce the dangers of low frequency flexural and torsional vibrations is designed. The actuator employs electro-hydraulic system and can provide a high and circumferential load. To initialize new research, the characteristics of various kinds of active actuators to control rotor shaft vibration are briefly introduced. The purpose of this paper is to introduce the preliminary results via presenting the structure, functions and operating principles, in particular, the working process of the electro-hydraulic system of the new actuator which includes a set of high speed electromagnetic valves and a series of sloping cone-shaped openings, and presenting the transmission relationships among the control parameters from control signals into the valves to active load onto shaft. The course of the work is dynamic, and a series of spatial forces and moments are put on the shaft to get an external resultant force to reduce excitations that induce vibration of shafts. By checking states of vibration, the actuator can control the impulse width and the interval of injection time for applying different control force to a vibration shaft in two circumference directions through the regulating action of a set of combination directional control valves. The results from simulating analysis and experiment show evidence of that this design can satisfy the case of active process of decreasing of flexural and torsional vibrations.     

Solution for torsional vibrations of stepped shafts using singularity functions

This paper gives a new viewpoint and calculation method for torsional vibrations of stepped shafts with attached rotors. The model has distributed, but discontinuous, parameters (both inertia and elasticity) including rigid thin disks. From the single governing equation of motion with derivatives in the generalized sense, simple and exact general forms of the frequency equation and of the mode shapes are extracted. This approach is the only way to demonstrate the orthogonality properties of the exact mode shapes. The modal superposition makes it possible to determine the torsional response of machine systems.     

基于四端网络法的汽轮发电机扭振特性仿真

基于四端网络模型和机械阻抗方法,提出了一种分布参数的汽轮发电机轴系扭振模型,并研制了相应的仿真软件包,可分析汽轮发电机扭振的各阶固有频率,振型及应力分布等性能,一种精确的低阶模型,算法简便快捷,所编软件包实用性强,可用于实际汽轮发电机轴系扭振的仿真研究。     

APPLICATION OF WAVELET PACKET ANALYSIS FOR FAULT DETECTION IN ELECTRO-MECHANICAL SYSTEMS BASED ON TORSIONAL VIBRATION MEASUREMENT

This paper primarily focuses on detecting electrical faults in turbine generator sets by monitoring torsional vibrations with the help of the non-contact measurement technique and analysing the data acquired from torsional vibration meter. Torsional vibrations in shaft trains can be excited by periodic excitation due to a variety of electromagnetic disturbances or unsteady flow in large steam turbine generator sets and may cause failure in shaft trains. A method is presented to use wavelet packet analysis for fault detection. It is achieved by decomposing the torsional vibration signals in the wavelet packet space at different levels to give finer details. Shannon wavelets have compact supports in frequency domain, it allows the analysis to be carried out in frequency bands of interest. Its effectiveness is verified by experimental results. Moreover, the application of the proposed method can be extended to analysis for transient conditions.     

Nonlinear Numerical Prediction of a Rotor–Bearing System Using Damped Flexure Pivot Tilting Pad Gas Bearings

Flexure pivot tilting pad gas bearings with pad radial compliance (FPTPGB-Cs) and metal mesh dampers (MMDs) in parallel (FPTPGB-C-MMDs) have been considered for application to high-speed and high-performance turbomachinery because of their advantages of high effective damping level and adequate compliance with variations in rotor geometry or misalignment. Although the dynamic coefficients of FPTPGB-C-MMDs have been predicted using the linear method, a nonlinear study is urgently needed for their high nonlinear behavior. A nonlinear numerical investigation on the rotor–bearing system supported by FPTPGB-C-MMDs is presented in this study by using the time domain orbit simulation method that couples rotor motion equations, the unsteady Reynolds equation, and pad motion (considering MMDs) equations. The nonlinear predictions are verified by the prediction and experimental results of a published paper.FPTPGB-C-MMDs can effectively suppress the subsynchronous vibrations compared with the rotor system supported by FPTPGB-Cs. The prediction results show that a high damper mesh density has a more positive effect on improving the stability of the rotor system by reducing the subsynchronous vibrations. Investigation shows that MMDs can improve the ability of the rotor system to sustain the effect of destabilizing forces. A high damper mesh density can sustain large destabilizing forces. The simulation results also indicate that low pad radial stiffness or preload leads to high amplitudes of subsynchronous vibrations. A small clearance results in an increase in critical speed and its synchronous amplitude. Moreover, large clearance results in a wide speed range that leads to the occurrence of subsynchronous vibrations with large amplitudes.