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针对早期碰摩时转子振动特征与其它旋转机械常见故障(如不对中)特征相重复的问题,研究转子进动信号中蕴含的早期碰摩故障特征.建立了转子动力学模型并求解得到仿真转子振动信号,从中计算出4项转子进动信号(公转半径、径向运动速度、公转转速、公转加速度)并进行了分析.结果表明发生早期碰摩时,转子进动信号的波动幅度会急剧加大,其中公转加速度信号会在碰摩点处发生瞬间剧烈波动,可用来指示碰摩部位;频谱中高阶倍频成分大大增加,大部分情况下高阶倍频代替转频成为主要成分.这些特征与正常状况有显著区别,可望用于碰摩故障的诊断. 相似文献
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针对旋转机械碰摩故障的特征,运用电涡流传感器和虚拟仪器检测和诊断转子的碰摩故障.分析了转子碰摩振动信号的时域波形特征、碰摩振动时的轴心运动轨迹特征,提出了应用小波包分解、重构技术进行消噪处理,实验分析结果表明该方法可以有效地提高故障诊断的准确性.这对转子碰摩故障诊断具有重要的理论和现实意义. 相似文献
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碰摩转子弯扭耦合振动特性仿真实验研究 总被引:1,自引:1,他引:1
建立了一碰摩转子弯扭耦合数学模型,应用非线性动力学理论对碰摩转子弯扭耦合数学模型的动态响应进行仿真。仿真结果表明,碰摩使转子的扭转振动和弯曲振动相互影响,产生复杂的运动形态。本文的研究结果对深入认识转子的碰摩机理和准确地诊断碰摩故障具有一定的参考价值。 相似文献
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结合机械结构寿命评价理论和数值分析方法,对基于有限元的大型汽轮机转子寿命评估系统进行研究。采用归一化方法对复杂的转子实际换热边界条件进行处理;依据转子的运行历史数据和结构几何参数自动生成传热学、力学边界条件,利用Delaunay非结构化自动剖分算法对几何模型进行网格剖分,将载荷谱处理和损伤累积无缝嵌入有限元分析过程。在此基础上,形成了基于复杂数值方法的转子寿命评价集成化系统,该系统具备了转子稳态、瞬态温度场、应力场和应变场分析及损伤和寿命评估功能,能直观显示转子损伤场分布及其演变,克服了传统方法中一些难以处理的技术障碍。 相似文献
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Scott C.Morris 《热科学学报(英文版)》2012,21(3):209-214
A numerical study is conducted to investigate the influence of inlet flow condition on tip leakage flow (TLF) and stall margin in a transonic axial rotor.A commercial software package FLUENT,is used in the simulation.The rotor investigated in this paper is ND_TAC rotor,which is the rotor of one-stage transonic compressor in the University of Notre Dame.Three varied inlet flow conditions are simulated.The inlet boundary condition with hub distortion provides higher axial velocity for the incoming flow near tip region than that for the clean inflow,while the incoming main flow possesses lower axial velocity near the tip region at tip distortion inlet boundary condition.Among the total pressure ratio curves for the three inlet flow conditions,it is found that the hub dis-torted inlet boundary condition improves the stall margin,while the tip distorted inlet boundary condition dete-riorates compressor stability.The axial location of interface between tip leakage flow (TLF) and incoming main flow (MF) in the tip gap and the axial momentum ratio of TLF to MF are further examined.It is demonstrated that the axial momentum balance is the mechanism for interface movement.The hub distorted inflow could de-crease the axial momentum ratio,suppress the movement of the interface between TLF and MF towards blade leading edge plane and thus enhance compressor stability. 相似文献
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针对转子高速转动的特点,分析了转子风道气体运动状态,建立了数值计算模型.分析结果表明,转子风道气体运动是由风扇和转子高速转动共同作用的结果,以吸入式空冷汽轮发电机通风结构为例,转子以3 000 r/min转速绕轴高速转动可以使风道中进风量由0.14 kg/s增加到0.21 kg/s,必须考虑转子转动对风道中气体运动的影响;粘性模型应选择无粘,相同条件下转子风道出口风速模型试验和数值模拟结果对比表明,数值模拟结果符合工程实际.转子风道中气体运动流场合理计算模型应为:以吸入式风扇和转子风道进口为进出口边界条件,流体边界条件考虑转子转动,墙边界条件中反映管壁表面粗糙度的相对粗糙度系数和常量分别取为k~+_s=500~1000和C_(ks)=1.0,粘性模型选择无粘,可用此计算模型对空冷汽轮发电机转子风道中气体运动流场进行分析. 相似文献
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Annika Lnger‐Mller 《风能》2019,22(4):523-537
The presented work investigates the impact of different sheared velocity profiles in the atmospheric boundary layer on the characteristics of a wind turbine by modifying the wall roughness coefficients in the logarithmic velocity profile. Moreover, the rotor and wake characteristics in dependence of the turbulence boundary conditions are investigated. In variant I, the turbulence boundary conditions are defined in accordance to the logarithmic velocity profile with different wall roughness lengths. In variant II, the turbulent kinetic energy and turbulent viscosity remain independent of the velocity profile and represent the free‐stream turbulence level. With an increase of the shear in the velocity profile, the amplitudes in the 3/rev characteristics of rotor thrust and rotor torque, induction factors, and effective angles of attack are increased. In variant I, the overall levels of thrust coefficient are hardly affected by the velocity profiles resulting from different wall roughness length values. The power coefficient is reduced about 1%. Conversely, compared with variant II, a difference of 2% in the power coefficient has been detected. Moreover, the wake recovery process strongly depends on the turbulence boundary condition. Simulations are carried out on an industrial 900‐kW wind turbine with the incompressible U‐RANS solver THETA. 相似文献
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The vertical axis wind turbines are simple in construction, self-starting, inexpensive and can accept wind from any direction without orientation. A combined Savonius–Darrieus type vertical axis wind rotor has got many advantages over individual Savonius or individual Darrieus wind rotor, such as better efficiency than Savonius rotor and high starting torque than Darrieus rotor. But works on the combined Savonius–Darrieus wind rotor are very scare. In view of the above, two types of models, one simple Savonius and the other combined Savonius–Darrieus wind rotors were designed and fabricated. The Savonius rotor was a three-bucket system having provisions for overlap variations. The Savonius–Darrieus rotor was a combination of three-bucket Savonius and three-bladed Darrieus rotors with the Savonius placed on top of the Darrieus rotor. The overlap variation was made in the upper part, i.e. the Savonius rotor only. These were tested in a subsonic wind tunnel available in the department. The various parameters namely, power coefficients and torque coefficients were calculated for both overlap and without overlap conditions. From the present investigation, it is seen that with the increase of overlap, the power coefficients start decreasing. The maximum power coefficient of 51% is obtained at no overlap condition. However, while comparing the power coefficients (Cp) for simple Savonius-rotor with that of the combined configuration of Savonius–Darrieus rotor, it is observed that there is a definite improvement in the power coefficient for the combined Savonius–Darrieus rotor without overlap condition. Combined rotor without overlap condition provided an efficiency of 0.51, which is higher than the efficiency of the Savonius rotor at any overlap positions under the same test conditions. 相似文献
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The authors present the calculation of the distribution of the transient temperature in the rotor bars of a canned induction motor, during locked rotor conditions, where the phenomena of electromagnetically induced currents and heat transfer are coupled. They have developed a coupled finite element electromagnetic code called WEMAP in which the calculated power loss densities are used as the heat sources for a transient thermal solution in subregions of the original problem geometry. These subregions are enclosed by surfaces on which either temperature or a convection boundary condition is known. In addition, the change in rotor bar resistance as a function of the temperature is included in these calculations. The calculated temperatures are compared with test results, and favorable agreement is obtained 相似文献
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In this paper, 3D Navier–Stokes simulations of the unsteady flow over the NREL Phase VI turbine are presented. The computations are carried out using the structured grid, incompressible, finite volume flow solver EllipSys3D, which has been extended to include the use of overset grids. Computations are presented, firstly, on an isolated rotor, and secondly, on the downwind configuration of the turbine, which includes modelling of the rotor, tower and tunnel floor boundary. The solver successfully captures the unsteady interaction between the rotor blades and the tower wake, and the computations are in good agreement with the experimental data available. The interaction between the rotor and the tower induces significant increases in the transient loads on the blades and is characterized by an instant deloading and subsequent reloading of the blade, associated with the velocity deficit in the wake, combined with the interaction with the shed vortices, which causes a strongly time‐varying response. Finally, the results show that the rotor has a strong effect on the tower shedding frequency, causing under certain flow conditions vortex lock‐in to take place on the upper part of the tower. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
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David Afungchui Baddreddinne Kamoun Ali Helali Abdellatif Ben Djemaa 《Renewable Energy》2010,35(1):307-313
The aim of this paper is to numerically explore the non-linear two-dimensional unsteady potential flow over a Savonius rotor and to develop a code for predicting its aerodynamics performances. In the model developed, the rotor is represented in a median plane by two semicircles, displaced along their common diameter. The two semicircles can be considered to produce lifting effects. As a result, they are modelled by a collection of discrete vortices on their contours. The flow field is then governed by the Laplace equation. The versatile Neumann boundary condition, applied over the contour of the semicircles and the Kutta Joukowsky condition applied at the four extremities of the semicircles have been used in the modelling. The torque distribution of the stationary rotor and the unsteady pressure field on the blades of the rotating rotor, predicted by the code developed, have been compared and validated by some experimental data. 相似文献