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.

Effectof Film Force Nonlinearity on Unbalance Responseof a Jeffcot RotorJournal Bearing System

The effect of oil film force nonlinearity on unbalance response of Jeffcot rotor elliptical bearing system is studied. Linear analysis is done by linearizing the bearing oil film dynamic forces and expressing them with stiffness and damping constants. Nonlinear dynamic simulation is done by taking the nonlinearity of bearing oil film dynamic force into full consideration, with the latter being expressed by a special database which is generated beforehand, and based on non stationary Reynolds equation and Reynolds boundary condition of film rupture. The linear and nonlinear unbalance responses of a Jeffcot rotor supported on a pair of elliptical bearings is studied. The resulting dynamic characteristics and rotor and journal whirling orbits are compared. While good consistancy between nonlinear and linear predictions is found under very small unbalance, significant or even drastic differences are found whenever the unbalance is not small, indicating the necessity of including the nonlinearity of oil film dynamic forces, especially when response to large unbalance is to be predicted.

Modeling unbalanced rotor system with continuous viscoelastic shaft by frequency-dependent shape function

A reduced-order dynamic model for an unbalanced rotor system is developed, taking the coupling between torsional and lateral vibrations into account. It is assumed that a shaft is regarded as a continuous viscoelastic shaft with unbalanced and small deformation properties. The equations of motion for the torsional and lateral vibrations are derived using Lagrange's approach with the frequency-dependent shape function. The rotor torsional vibration is coupled with the lateral vibrations by unbalance elements in a way of excitations. Simulation and experiment results show clearly that the torsional vibration has strong impact on the rotor lateral vibrations, and it causes subharmonic and superharmonic excitations through unbalance elements, which leads to the superharmonic resonances in the lateral vibrations. This model with low-order and high accuracy is suitable for rotor dynamic analysis in real time simulation as well as for active vibration control syntheses.

SAFETY MARGIN CRITERION OF NONLINEAR UNBALANCE ELASTIC AXLE SYSTEM

The safety margin criterion of nonlinear dynamic question of an elastic rotor system are given. A series of observing spaces were separated from integral space by resolving and polymerizing method. The stable_state trajectory of high dimensional nonlinear dynamic systems was got within integral space.According to international standard of rotor system vibration, energy limits of safety criterion were determined. The safety margin was calculated within a series of observing spaces by comparative positive_area criterion (CPAC) method. A quantitative example calculating safety margin for unbalance elastic rotor system was given by CPAC. The safety margin criterion proposed includes the calculation of current stability margin in engineering. This criterion is an effective method to solve quantitative calculation question of safety margin and stability margin for nonlinear dynamic systems.

A Modified Iterative Learning Control Approach for the Active Suppression of Rotor Vibration Induced by Coupled Unbalance and Misalignment

This paper proposes a modified iterative learning control(MILC)periodical feedback-feedforward algorithm to reduce the vibration of a rotor caused by coupled unbalance and parallel misalignment.The control of the vibration of the rotor is provided by an active magnetic actuator(AMA).The iterative gain of the MILC algorithm here presented has a self-adjustment based on the magnitude of the vibration.Notch filters are adopted to extract the synchronous(1×Ω)and twice rotational frequency(2×Ω)components of the rotor vibration.Both the notch frequency of the filter and the size of feedforward storage used during the experiment have a real-time adaptation to the rotational speed.The method proposed in this work can provide effective suppression of the vibration of the rotor in case of sudden changes or fluctuations of the rotor speed.Simulations and experiments using the MILC algorithm proposed here are carried out and give evidence to the feasibility and robustness of the technique proposed.

重型燃气轮机拉杆组合转子热瞬变振动特性研究

重型燃气轮机冷态启动的稳速升负荷阶段,常出现轮盘间径向变形不协调导致的相对滑移,拉杆组合转子会发生振动随燃气轮机转子温度的增加而显著变化的热瞬变振动现象。建立了周向拉杆组合转子平面摩擦带止口配合结构轮盘相对滑移的力学模型,包括平面摩擦、周向拉杆和止口与轮盘相对滑移的力学模型。以某型重型燃气轮机拉杆组合转子为研究对象,对其冷态启动过程中出现的热瞬变振动进行了分析,根据轮盘相对滑移的规律,通过减小轮盘间的变形不协调,并适当增加止口配合的过盈量的方法,成功优化了该重型燃气轮机拉杆组合转子冷态启动过程中的热瞬变振动。

突加不平衡下GTF发动机转子系统瞬态响应分析

针对GTF发动机低压转子系统突加不平衡瞬态响应问题,基于有限元法建立了考虑啮合单元、行星架单元、膜盘联轴器单元的多体接触、多转子耦合动力学模型,介绍了考虑非线性因素下突加不平衡瞬态响应计算方法,求解了低压转子系统的突加不平衡瞬态响应,并分析了关键部件刚度对突加不平衡的影响规律。结果表明:当风扇转子发生突加不平衡时,各部件均表现为振动幅值突增,后迅速趋于稳定,低压涡轮转子发生明显拍振,突加不平衡载荷主要由行星架结构和第1.5支点刚性支承承担;行星架刚度主要影响风扇转子突加不平衡响应、第1.5支点和行星架处的外传力;膜盘联轴器刚度主要影响增压级突加不平衡响应、转子在突加不平衡之后稳定运转情况。

立式离心泵典型故障复现试验研究

为了给立式离心泵的故障诊断提供试验和理论依据,搭建立式离心泵仿真试验台,进行立式离心泵典型故障的仿真复现试验,分析了转子不平衡、转子不对中和支座连接松动等故障的振动特性及其频谱特征.结果表明:机脚处的振动位移信号对支座连接松动故障的振动特性敏感性更高,轴系的振动信号对转子故障的振动特性敏感性更高;转子不平衡故障和转子不对中故障表现出不同的频谱特征,转子不平衡故障的频谱特征表现为1倍振动主要频率(amplitude power frequency,APF)幅值增大,且随着故障程度的增加,幅值呈现了逐渐减小的趋势,转子不对中故障的频谱特征表现为产生新的振动特征频率2APF,且随着故障程度的增大,信号幅值逐渐增大;支座连接松动故障表现为频谱图中的主频变为3APF,并出现新的2APF和1/2分数谐波频率.

非线性支承下磁悬浮转子系统μ综合控制的研究

针对磁悬浮转子系统支承力的非线性和不平衡扰动问题,采用μ综合控制方法对系统进行控制。根据磁悬浮转子系统模型推导出系统状态空间方程,并对其中的非线性支承力进行平衡点线性化,对状态空间方程进行模态分析,得到低阶控制模型,再通过D-K迭代法得到μ综合控制器,并将其应用于非线性支承下的磁悬浮转子系统。结果表明:μ综合控制下的闭环转子系统具有良好的起浮性能和抗干扰性能;与PID控制比较,μ综合控制下转子系统不平衡响应基频幅值和倍频幅值显著降低;系统不平衡扰动和非线性效应得到了抑制。

离心风机的故障验证技术研究

针对离心风机开展了故障注入试验与数据分析研究,阐述了风机叶轮不平衡、转子不平衡和轴承断裂故障对振动数据的影响。研究特征值变化规律,提取出其中有效的故障信号,为离心风机在线监测奠定了基础,对离心风机的运行维护具有极其重要的意义。

航空发动机转子不平衡量突增的自动识别

为实现在航空发动机振动信号分析时因封严胶条脱落发生的转子不平衡量突增的自动识别,采用多傅里叶变换(FFT)滤波技术获得转速跟踪滤波后的基频振动时域信号,提出了振幅突增和突增后振幅稳定的转子不平衡量突增的2种特征,通过应用案例对振动信号的程序化进行处理,得到转速跟踪滤波后的基频振动时域信号及转子不平衡量突增的识别参数,数据结果中振幅增大比例系数达到3.75,且突增后振幅稳定。结果表明:采用FFT滤波技术,实现了转子不平衡突增的自动识别,并验证了识别方法的有效性。转子不平衡量突增的识别技术应用于在线监测系统时,能及时识别故障并发出报警信息,保证设备运转的安全;应用于离线振动信号分析系统时,缩短了人工数据分析时间,提高了工作效率。

搭接-叠片式箔片气体动压轴承转子动力学特性实验研究

本文研制了由搭接式径向轴承和叠片式推力轴承组成的一套搭接-叠片式箔片气体动压轴承,同时设计并搭建了相应的箔片气体动压轴承转子实验台,通过多组转子降速对比实验研究了所提出箔片气体动压轴承的起飞特性,分析了转子不平衡量和外部载荷对该轴承-转子系统的转子动力学影响。起飞实验结果表明,本文所研制的搭接式径向箔片气体动压轴承的起飞转速约为7500 r/min,最大起飞转矩约为220 N·mm。转子降速实验研究结果表明,随着转子不平衡量的增加,转子系统1X频振动幅值逐渐增大、二阶临界转速逐渐降低、次频振动发生频率逐渐提前;随着转子转速的增加,转子系统1X频振动呈现先增大后减小的趋势、次频振动幅值整体逐渐增大;在减小顶箔结构的圆心距后,转子系统稳定性增加。不平衡量与外部载荷加载耦合实验结果表明,不平衡量与外部载荷都会激起系统的次频振动,次频振动幅值随转速升高而增大;并且在激起次频振动方面,不平衡量与外部载荷之间存在着相互放大作用。

催化烟机振动值上升原因分析与处理措施研究

催化烟机在日常运行中振动值突升导致主风机联锁停机。通过逐一分析影响烟机振动的各种因素,查找出问题出现的原因,制定机组操作指南。经烟机解体检修后确认,此次烟机故障原因为拉杆断裂,为类似故障处理提供了经验。

双重三要素型转子吸振器抑振性能的稳定性分析

利用转子动力学方法对双重三要素型吸振器-转子系统进行动力学建模,并基于局部灵敏度分析法建立了灵敏度评价模型,分析了最优抑振性能对吸振器参数、不平衡力、安装位置的灵敏度,探讨了吸振器抑振性能的稳定性。结果显示:当参数偏离系数为-0.35时,最优抑振性能对两个单体吸振器质量的灵敏度分别为0.54和0.36,而对串联刚度的灵敏度仅为0.03和0.12。整体上看,固有频率较大的单体吸振器的参数灵敏度系数相对较小。不平衡力增大时,系数均为正值。存在安装位置误差的情况下,吸振器使用时的安装位置若靠近优化时的安装位置,其灵敏度系数降低至0.05;而远离时,灵敏度系数提高至1.58。因此,在吸振器的参数中,质量对最优抑振性能的稳定性影响最大,而串联刚度的影响最小。固有频率较小的单体吸振器的参数对稳定性影响较大。使用安装位置距离优化时的安装位置越接近,其稳定性越高。

某1000 MW机组发电机阻尼条蹿动致转子振动异常案例分析及处理

详细介绍了某台1 000 MW汽轮发电机在检修后并网运行时转子振动幅值随负荷的升高而异常增大的分析和处理全过程。通过机组运行数据、变工况测试、转子匝间绝缘诊断和抽转子检修等分析转子振动异常的原因,同时结合机组检修,对转子阻尼条通风孔进行偏划扩孔。结果表明:转子阻尼条蹿动导致部分通风孔严重堵塞引起转子在高负荷工况下严重的热不平衡,进而造成转子振动异常,通过采用偏划扩孔方案彻底解决了阻尼条蹿动对异常转子振动的影响。

高负荷变动率下核电汽轮机转子热应力数值模拟

国内某大型核电汽轮机需要在线性负荷变动率为每分钟6%额定负荷工况下运行,这超出了当前国内建造的第三代核电的设计限制。汽轮机是影响机组负荷变动率的要素之一。采用ANSYS软件对汽轮机进行了有限元分析,模拟了汽轮机高压缸转子在负荷变动率为每分钟6%额定负荷工况下的温度场和应力场,结合转子疲劳曲线,评估了该高变负荷运行工况对汽轮机转子疲劳寿命的影响。研究成果可以为“双碳”目标下提升核电机组运行灵活性、适应当前核能-多能耦合运行提供参考。

具有轴向温差的封闭转静系盘腔流动和换热特性研究

采用数值模拟探究了具有轴向温差下封闭转静系盘腔的流动和换热特性。通过改变热罗斯比数,探究不同工况下盘腔的流动结构、温度分布以及转静盘努塞尔数的径向分布规律。结果表明:具有轴向温差的封闭转静系盘腔与等温封闭转静系盘腔的基本流动结构一致,属于典型的Batchelor流型;与等温封闭转静系盘腔相比,核心区内无量纲周向速度增大,且随着热罗斯比数的增加核心区无量纲周向速度逐渐增加、转静盘边界层内流体的无量纲周向速度也增加;具有轴向温差下,盘腔的温度沿径向逐渐降低,沿轴向先降低、经过核心区温度保持不变、靠近转盘侧继续降低;在热罗斯比数一定时,转静盘的努塞尔数沿径向逐渐增大,随着热罗斯比数的增加,转静盘的努塞尔数有所减小。

Dynamics Modeling and Numerical Analysis of Rotor with Elastic Support/Dry Friction Dampers

The elastic support/dry friction damper is a type of damper which is used for active vibration control in a rotor system.To establish the analytical model of this type of damper,a two-dimensional friction model-ball/plate model was proposed.By using this ball/plate model,a dynamics model of rotor with elastic support/dry friction dampers was established and experimentally verified.Moreover,the damping performance of the elastic support/dry friction damper was studied numerically with respect to some variable parameters.The numerical study shows that the damping performance of the elastic support/dry friction damper is closely related to the stiffness distribution of the rotor-support system,the damper location,the pressing force between the moving and stationary disk,the friction coefficient,the tangential contact stiffness of the contact interface,and the stiffness of the stationary disk.In general,the damper should be located on an elastic support which has a large vibration amplitude in order to achieve a better damping performance,and the more vibration energy in this elastic support concentrates,the better performance of the damper will be.The larger the tangential contact stiffness of the contact interface,and the stiffness of the stationary disk are,the better performance of the damper will be.There will be an optimal value of the friction force at which the damper performs best.

Temperature Field Analysis of Mine Flameproof Outer Rotor Permanent Magnet Synchronous Motor with Different Cooling Schemes

Aiming at the problem of temperature rise of mine flameproof outer rotor permanent magnet synchronous motor,based on the fluid structure coupling method,the temperature distribution of motor under three cooling schemes of air cooling and water cooling are calculated respectively.For the structure I air cooling system,the influence of different number of heat sink on the maximum temperature rise and pressure drop of fluid channel is analyzed,and the parameters of heat sink are optimized.For the structure II air cooling system,the influence of setting fillet at the turn back of the fluid channel on the head loss in the fluid domain of the motor is analyzed,and the influence of different fillet radius on the head loss and the maximum temperature rise in the fluid domain is obtained.For the structure II water cooling system,the influence of different water flow speed on the maximum temperature rise of the motor is analyzed,and the influence of different assembly clearance of modular stator teeth and yoke on the maximum temperature rise of the motor is analyzed.The cooling effect and temperature rise distribution characteristics of the three cooling schemes are compared and analyzed.Finally,a water-cooled prototype is manufactured,and the temperature rise experiment is carried out,and the influence of the thermal deformation of fluid channel,stator yoke and stator teeth on the maximum temperature of the motor is analyzed.The results show that the calculated temperature field after considering the thermal deformation is closer to the experimental value,which verifies the accuracy of the calculation results,It also provides a reference for the selection and design of the cooling structure of the same type of PMSM electric roller.