Optimization Method of Bearing Support Positions in a High-Speed Flexible Rotor System

Bearing support position is one of main factors affecting vibration characteristics of rotor systems. To optimize the bearing support positions in a high-speed flexible rotor system (HSFRS) based on the vibration characteristics, an optimization method of bearing support positions in the HSFRS is proposed. In this method, a finite element (FE) model of a high-speed flexible rotor (HSFR) was established. The natural frequencies and mode shapes of the HSFRS were used to obtain the initial design scheme of the bearing support positions. A frequency characteristic equation of the HSFRS was established to obtain the critical speeds of the HSFRS. And a dynamic model of the HSFRS was established to analyze the vibration characteristics for different bearing support position cases. The problem of optimizing bearing support positions in the HSFRS was solved by the developed method. The results showed that vibration amplitudes of the HSFRS were more stable when the bearing support positions were optimized. This study can provide a new method for optimizing bearing support positions of rotor systems.

REDUCING VIBRATION WITH FRICTION-DAMPING IN HIGH-SPEED ROTOR SYSTEM

To reduce the excessive vibration of a high-speed rotor system at the critical speed, a friction damper with a flexible support structure is introduced. The mechanism of vibration reduction and support characteristics are analyzed and a friction damper is designed. The effect on an unbalanced response is studied. Results show that the stiffness factor and the friction-damping factor of the damper are related to the cone angle and the friction factor of the inner-ring when adopting a proper structure. By changing these parameters and the Z-directional stiffness of the outer-ring, the stiffness and the damping characteristic of the damper can be varied. Introducing a friction damper into the support can reduce the stiffness and increase the damping of the support, thus decreasing the critical speed to avoid the operating speed, suppress the resonant response of a rotor system, and attenuate vibration forces to the outside.

Model-Based Degree Estimation of Unbalance and Misalignment in Flexible Coupling-rotor System

The condition of rotor system must be assessed in order to develop condition-based maintenance for rotating machinery. It is determined by multiple variables such as unbalance degree, misalignment degree, the amount of bending deformation of the shaft, occurrence of shaft crack of rotor system and so on. The estimation of the degrees of unbalance and misalignment in flexible coupling-rotor system is discussed. The model-based approach is employed to solve this problem. The models of the equivalent external loads for unbalance and misalignment are derived and analyzed. Then, the degrees of unbalance and misalignment are estimated by analyzing the components of the equivalent external loads of which the frequencies are equal to the 1 and 2 times running frequency respectively. The equivalent external loads are calculated according to the dynamic equation of the original rotor system and the differences between the dynamical responses in normal case and the vibrations when the degree of unbalance or misalignment or both changes. The denoise method based on bandpass filter is used to decrease the effect of noise on the estimation accuracy. The numerical examples are given to show that the proposed approach can estimate the degrees of unbalance and misalignment of the flexible coupling-rotor system accurately.

Finite Element Method Applied to the Eigenvalue Analysis of Flexible Rotors Supported by Journal Bearings

This work deals with a finite element procedure developed to perform the eigenvalue analysis of damped gyroscopic systems, represented by flexible rotors supported on fluid film journal bearings. The rotor finite element model is based on the Timoshenko beam theory, accounting for the shaft rotary inertia and gyroscopic moments. The governing equations for the hydrodynamic journal bearing are obtained through the Galerkin weighted residual method applied to the classical Reynolds equation. A perturbation scheme on the fluid film governing equation permits to obtain the zero-th and first order lubrication equations for the bearings, which allow the computation of the dynamic force coefficients associated with the bearing stiffness and damping. The rotor-bearing system equation, which consists of a case of damped gyroscopic equation, is rewritten on state form to compute the complex eigenvalues. The natural frequencies at several operating conditions are obtained and compared to the technical literature data. The influence of the effective damping on the eigenvalue real part sign is analyzed for some examples of rotor-bearing systems, showing how the stability conditions can be predicted by the eigenvalue analysis. The procedure implemented in this work can provide useful guidelines and technical data about the selection of the more appropriate set of bearing parameters for rotating machines operating at stringent conditions.

Optimization of a Flexible Rotor-Sliding Bearing System With a Squeeze Film Damper

A dynamic model of a flexible rotor-sliding bearing system ( FRSBS ) with asqueeze film damper ( SFD) is established. Considered in the model are oil film inertia force,damping farce, clearance excitation force, interference force of different frequencies and staticload, as opposed to previous research. On the basis of this model, the optimal design of the systemis deeply studied. Simulation shows that the system optimization design can effectively improve thesystem stability.

TRANSIENT RESPONSE OF FLEXIBLE ROTOR WITH ACTIVE MAGNETIC BEARINGS DURING ROTOR DROP

A new technique so-called finite modes condensation based on modal analysis is presented to simplify a long and complicated rotor system with distributed mass into a simplified rotor model with adjustablenumber of degrees of freedom. By means of this new method, a practical example study shows that it can bedone to calculate transient response for any cross-section of a flexible rotor with enough accuracy during itsdrop in case that there exist several active magnetic bearings and traditional bearings.

Residual Value Balance Method for Large Flexible Rotors

A Large balancing weight may be obtained by calculation, when the ordinary influence coefficient method is used. In this paper, a new residual value balance method is recommended. The fundamental idea of the new method is on the principle of getting the minimized weight on condition that the vibration values at various points are less than the admitted ones. Experimental results show that this method is effective for balancing the insensitive rotor and rotors with special dynamic characteristics.

Structural Dynamic Optimization for Flexible Beam of Helicopter Rotor Based on GA

As one of the most important steps in the design of bearing-less rotor systems,the design of flexible beam has received much research attention.Because of the very complex working environment of helicopter,the flexible beam should satisfy both the strength and dynamic requirements.However,traditional optimization research focused only on either the strength or dynamical characteristics.To sufficiently improve the performance of the flexible beam,both aspects must be considered.This paper proposes a two-stage optimization method based on the Hamilton variational principle:Variational asymptotic beam section analysis(VABS)program and genetic algorithm(GA).Consequently,a two-part analysis model based on the Hamilton variational principle and VABS is established to calculate section characteristics and structural dynamics characteristics,respectively.Subsequently,the two parts are combined to establish a two-stage optimization process and search with GA to obtain the best dynamic characteristics combinations.Based on the primary optimization results,the section characteristics of the flexible beam are further optimized using GA.The optimization results show that the torsional stiffness decreases by 36.1%compared with the full 0°laying scheme without optimization and the dynamic requirements are achieved.The natural frequencies of flapping and torsion meet the requirements(0.5 away from the passing frequencies of the blade,0.25 away from the excitation force frequency,and the flapping and torsion frequencies keep a corresponding distance).The results indicate that the optimization method can significantly improve the performance of the flexible beam.

RESEARCH ON SCHEME OF HIGH-SPEED ROTOR／WING TRANSITION HELICOPTER RD15

To analyze the existing schemes of high-speed rotorcrafts and some new technologies, a new conceptual sketch of the high-speed rotor/wing transition helicopter RD15 is proposed. The overall layout of the RD15 is given out and the transition process from the helicopter mode to the airplane mode is designed. The lift system consists of a circular disk-wing with four retractable blades. The technology of individual blade control is adopted for flight control in hover and low speed flight. The tail is a vectored thrust duct propeller. It can provide the anti-torque in hover, and offer the multi-directional controls and propulsion drive for the airplane mode flight. The aerodynamic characteristics and key technologies in the transition process for this layout, including the nose up angle of disk-wing, the length of the blade, rotation speed, pitch angle and other parameters, are theoretically ana lyzed and experimentally tested. Calculation and experiments show that the shift process of the lift, the power and controls are smooth, and the designed scheme is feasible.

Research on Rubbing-fault Diagnosis System in High-speed Rotor based on LabVIEW

The rubbing between rotors and determiners is the common mechanic vibration fault in the operation of rotation machinery. During the operation of equipment, in order to meet the demand of high speed and efficiency of machinery, the gap between the active and passive parts of the rotor system become smaller, which results in the common rubbing fault of rotors and stators. This essay studies the fault diagnosis of high speed rotors based on invented instrument and shows the measurement and research of the signals of rubbing failure of high speed rotors. The research introduces the designed software and hardware which are experimented and testified on Bentley rotor experiment platform. The system has theoretical and applicative meaning in practical projects.

Analysis of vibration and frequency transmission of high speed EMU with flexible model

When the operation speed of the high-speed train increases and the weight of the carbody becomes lighter,not only does the sensitivity of the wheel/rail contact get higher,but also the vibration frequency range of the vehicle system gets enlarged and more frequencies are transmitted from the wheelset to the carbody.It is important to investigate the vibration characteristics and the dynamic frequency transmission from the wheel/rail interface to the carbody of the high-speed electric multi-uint（EMU）.An elastic highspeed vehicle dynamics model is established in which the carbody,bogieframes,and wheelsets are all dealt with as flexible body.A rigid high-speed vehicle dynamics model is set up to compare with the simulation results of the elastic model.In the rigid vehicle model,the carbody,bogieframes and wheelsets are treated as rigid component while the suspension and structure parameters are the same as used in the elastic model.The dynamic characteristic of the elastic high speed vehicle is investigated in time and frequency domains and the di ff erence of the acceleration,frequency distribution and transmission of the two types of models are presented.The results show that the spectrum power density of the vehicle decreases from the wheelset to the carbody and the acceleration transmission ratio is approximately from 1%to 10%for each suspension system.The frequency of the wheelset rotation is evident in the vibration of the flexible model and is transmitted from the wheelset to the bogieframe and to thecarbody.The results of the flexible model are more reasonable than that of the rigid model.A field test data of the high speed train are presented to verify the simulation results.It shows that the simulation results are coincident with the field test data.

Effect of wheelset flexibility on wheel–rail contact behavior and a specific coupling of wheel–rail contact to flexible wheelset

The fexibility of a train＇s wheelset can have a large effect on vehicle–track dynamic responses in the medium to high frequency range.To investigate the effects of wheelset bending and axial deformation of the wheel web,a specifi coupling of wheel–rail contact with a fexible wheelset is presented and integrated into a conventional vehicle–track dynamic system model.Both conventional and the proposed dynamic system models are used to carry out numerical analyses on the effects of wheelset bending and axial deformation of the wheel web on wheel–rail rolling contact behaviors.Excitations with various irregularities and speeds were considered.The irregularities included measured track irregularity and harmonic irregularities with two different wavelengths.The speeds ranged from 200 to400km/h.The results show that the proposed model can characterize the effects of fexible wheelset deformation on the wheel–rail rolling contact behavior very well.

Parametric analysis of wheel wear in high-speed vehicles

In order to reduce the wheel profile wear of highspeed trains and extend the service life of wheels, a dynamic model for a high-speed vehicle was set up, in which the wheelset was regarded as flexible body, and the actual measured track irregularities and line conditions were considered. The wear depth of the wheel profile was calculated by the well-known Archard wear law. Through this model, the influence of the wheel profile, primary suspension stiffness, track gage, and rail cant on the wear of wheel profile were studied through multiple iterafive calculations. Numerical simulation results show that the type XP55 wheel profile has the smallest cumulative wear depth, and the type LM wheel profile has the largest wear depth. To reduce the wear of the wheel profile, the equivalent conicity of the wheel should not be too large or too small. On the other hand, a small primary vertical stiffness, a track gage around 1,435-1,438 mm, and a rail cant around 1：35-1：40 are beneficial for dynamic performance improvement and wheel wear alleviation.

Analysis of Temperature Rise in High-Speed Permanent Magnet Synchronous Traction Motors by Coupling the Equivalent Thermal Circuit Method and Computational Fluid Dynamics

To solve the problem of temperature rise caused by the high power density of high-speed permanent magnet synchronous traction motors,the temperature rise of various components in the motor is analyzed by coupling the equivalent thermal circuit method and computational fluid dynamics.Also,a cooling strategy is proposed to solve the problem of temperature rise,which is expected to prolong the service life of these devices.First,the theoretical bases of the approaches used to study heat transfer and fluid mechanics are discussed,then the fluid flow for the considered motor is analyzed,and the equivalent thermal circuit method is introduced for the calculation of the temperature rise.Finally,the stator,rotor loss,motor temperature rise,and the proposed cooling method are also explored through experiments.According to the results,the stator temperature at 50,000 r/min and 60,000 r/min at no-load operation is 68℃ and 76℃,respectively.By monitoring the temperature of the air outlets inside and outside the motor at different speeds,it is also found that the motor reaches a stable temperature rise after 65 min of operation.Coupling of the thermal circuit method and computational fluid dynamics is a strategy that can provide the average temperature rise of each component and can also comprehensively calculate the temperature of each local point.We conclude that a hybrid cooling strategy based on axial air cooling of the inner air duct of the motor and water cooling of the stator can meet the design requirements for the ventilation and cooling of this type of motors.

Flexible Optimal Model and Algorithm for Track Utilization in High-speed Railway Stations

Track utilization is the most important technical operation in high-speed railway stations.It is an effective way to take flexible man-agement based on dispatchers’decision preferences into consideration for making track utilization plans to relieve the influence caused by unmeasurable unstructured factors.Thus,based on the flexible management concept and taking the flexible optimal for track utilization in high-speed railway stations as the object,time and space occupation safety trajectories of arrival routes,departure routes and tracks are all analysed.Then,taking the following constraints into consideration-minimum safety time intervals for var-ious routes and tracks occupation,space-time arc occupation and decision-makers’preferences-a flexible optimal model for track utilization in high-speed railway stations is established to maximize its balance and robustness and to minimize its volatility at the same time.Further,a flexible optimal solution based on a simulated annealing algorithm is designed to make a safety track utilization plan in high-speed railway stations integrating the dispatchers’decision preference.The results from the experiments show that the proposed methodology can effectively make satisfied safety track utilization plans based on decision-makers’preferences,which can improve its balance and robustness level significantly.Meanwhile,its volatility can be reduced as much as possible caused by flexible management based on artificial intervention to ensure the relative stability of the plan.

基于虚拟力分析的全柔性共轴旋翼无人机路径跟踪方法

随着无人机作业工况复杂性的提升,对其控制精度提出了更高要求,需结合多种因素对无人机控制系统和结构特性进行建模并开展改进研究。该文章提出了基于虚拟力分析的全柔性共轴旋翼无人机路径跟踪方法:首先,基于旋翼柔性变形的受力形变模型构建全柔性共轴旋翼无人机动力学模型;然后,依据虚拟力分析方法制定虚拟力反馈控制律,并利用长短时记忆网络实现基于虚拟力反馈无人机路径跟踪;最后,开展模型特性分析及仿真实验,验证了所提方法在抵抗外界干扰方面具有有效性和鲁棒性。

柔性转子弹性对行波旋转超声电机接触特性的影响

转/定子间动态接触过程决定行波旋转超声电机(TRUM)的输出性能,但是柔性转子弹性在以往界面接触特性研究中常被忽略.本文中基于建立的考虑柔性转子和摩擦层三维弹性的转-定子动力学耦合模型,从接触界面的接触状态、速度、接触应力、摩擦应力驱动和阻碍子区等空间分布角度,研究了柔性转子弹性对TRUM摩擦界面的动态接触行为和摩擦损耗的影响.结果表明:柔性转子在轴向、径向和切向均呈现出一定的振动速度,且在接触界面沿圆周方向与定子各向速度形成一定的相位关系,显著影响界面动态接触特性、摩擦特性和摩擦损耗;柔性转子与定子轴向位移分布的相位一致性表明,定子与摩擦层的接触界面具有类齿轮啮合机制;与以往中间驱动两端阻碍的分布结果不同,考虑转/定子动力学耦合的接触区摩擦应力分布为一端驱动和一端阻碍的新机制.计算结果表明在建模过程中忽略柔性转子弹性得到的界面摩擦损耗要比考虑柔性转子弹性获得的摩擦损耗大得多,主要原因:(1)柔性转子径向刚度小,摩擦力作用下接触区的运动方向与定子相同,从而减小了径向速度差和径向摩擦损耗;(2)柔性转子界面的切向振动特性,改变了接触界面黏-滑子区分布,使得行波远离端的摩擦应力阻碍子区消失,且摩擦层界面切向剪切变形长度增大,从而减小了切向滑动和摩擦损耗.研究结果将有助于更好地理解TRUM中的动态接触特性,并指导摩擦界面的设计.

弹性支撑双风轮风电机组传动链强度分析

为使前后风轮间流场干涉影响降低,双风轮风电机组传动链具有跨距长、支撑点多的特性,导致双风轮风电机组传动链在长跨距柔性主机架支撑下具有复杂的载荷特性。建立考虑主机架柔性的某型双风轮风电机组传动链动力学模型,分析齿轮与主机架结构强度。结果表明:各级齿轮接触强度、弯曲强度以及主机架强度均满足设计要求;主机架支撑变形有助于协调各构件之间的相对变形,适量减小主机架柔性有助于改善传动链承载时主轴轴承之间的轴线不对中情况。

基于柔性转子的液膜密封稳态性能研究

为了研究转子柔性状态下动力学特征对航空发动机附件机匣轴端液膜密封的影响,结合转子的振幅、弯曲角度和热流体动力润滑理论,建立了柔性转子-液膜密封稳态分析模型,探究柔性转子-液膜密封的成膜机理,研究偏心量、倾斜角度、结构参数和工况参数对液膜密封性能影响规律。结果表明:当动环发生偏心时,液膜压力分布呈现不均匀性,随着偏心量由0.1 mm增至0.5 mm时,密封泄漏量上升了11.84%;倾斜角度的增加在一定程度上可以减弱膜压不均匀性,但对密封性能的影响不明显,当倾斜角度从1×10^(-5) rad升至3×10^(-5) rad时,泄漏量仅增加2.1%;在工况参数不变时,适当减少螺旋槽数,并选取合适的螺旋角度,可以有效抑制泄漏现象;在相同的结构参数条件下,适当降低转速及压差可以有效降低泄漏量;基于柔性转子的液膜密封由于较大偏心量的存在,会导致密封性能下降,此外,高转速与大压差会进一步增加泄漏量,工程应用中可通过减少槽数,修改螺旋角度的方式抑制泄漏。研究可为液膜密封的优化设计提供理论依据。

基于ANSYS/Rotordynamics的磁悬浮柔性转子运动特性研究

用ANSYS/Rotordynamics分析软件建立了磁悬浮柔性转子的有限元模型;对转子的运动特性——临界转速、模态轨迹和振型进行了系统的计算和理论分析;研究了磁悬浮柔性转子模态轨迹的特性以及对位移测试信号的影响;同时,为同类磁悬浮柔性转子的悬浮控制提供理论参考。