Journal articles on the topic 'Rotor Dynamic Eccentricity'
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1
Li, M., and L. He. "The dynamics of a parallel-misaligned and unbalanced rotor system under the action of non-linear oil film forces." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 224, no. 9 (September 1, 2010): 1875–89. http://dx.doi.org/10.1243/09544062jmes1916.
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A mathematical model of a parallel-misaligned rotor system with mass eccentricity that is supported on journal bearings is discussed and its dynamic behaviours are analysed under the action of non-linear oil forces in the present work. First, some assumptions are introduced, such as the long bearing model, small parallel misalignment between rotors and tiny eccentricity of discs, the misaligned displacement constraint between two rotors is taken into account, and the motion equations are deduced by the Lagrange method of undetermined multiplier. Then, the rotor orbits, Poincaré maps, and bifurcation diagrams of the system are studied by a numerical method; the results show that there exists some unrevealed motions and phenomena in the parallel-misaligned and unbalanced rotor system such as period 2, 3, 6, and 7 motions besides chaotic oscillations and so on.
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Muszynska, A. "Improvements in Lightly Loaded Rotor/Bearing and Rotor/Seal Models." Journal of Vibration and Acoustics 110, no. 2 (April 1, 1988): 129–36. http://dx.doi.org/10.1115/1.3269489.
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A model for lightly loaded steadily rotating shaft/bearing/seal systems is proposed in this paper. The model is based on modal characteristics for the rotor, and rotational characteristics for the fluid dynamic forces generated in bearings and/or seals. The fluid average circumferential velocity ratio as a nonlinear function of shaft eccentricity represents a key factor in the model. The model is extremely useful for rotor stability analysis. The model adequacy was proved for one and two lateral mode models of rotors.
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Chen, Guoda, Yijie Chen, Qi Lu, Quanhui Wu, and Minghuan Wang. "Multi-Physics Fields Based Nonlinear Dynamic Behavior Analysis of Air Bearing Motorized Spindle." Micromachines 11, no. 8 (July 25, 2020): 723. http://dx.doi.org/10.3390/mi11080723.
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The air bearing motorized spindle (ABMS) is the key component of the ultra-precision machine tool, which plays an important role in the ultra-precision machining process and directly influences machining accuracy. The influence of unbalanced magnetic force (UMF) on the nonlinear dynamic behavior of the ABMS is not understood clearly. To reveal the potential influence of the UMF, a mathematical model of the ABMS considering multiphysics fields is established. The variation trend of the UMF is simulated, and the nonlinear dynamic behavior of the ABMS is analyzed which emphasizes on the stability of the rotating shaft. It is shown that the UMF varies linearly at large rotor eccentricity which meets well with previous research, but it is noteworthy the UMF varies nearly to a quadratic function at small rotor eccentricity. The result of rotor dynamics shows that the UMF can change the converge position of the rotor center and the converge speed. Moreover, when at certain rotor mass and external load, the UMF can enlarge the stability boundary of the rotor. This research provides an example of analyzing the nonlinear dynamic behavior of the ABMS considering multiphysics fields which may help to the further investigation.
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WERNER, ULRICH. "THEORETICAL VIBRATION ANALYSIS OF SOFT MOUNTED TWO-POLE INDUCTION MOTORS WITH STATIC ROTOR ECCENTRICITY." International Journal of Applied Mechanics 03, no. 01 (March 2011): 131–59. http://dx.doi.org/10.1142/s1758825111000919.
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The paper shows a mathematical model for vibration analysis of soft mounted two-pole induction motors regarding electromagnetic excitation due to static rotor eccentricity. A static rotor eccentricity causes an electromagnetic force, acting on the rotor and on the stator and oscillating with the double supply frequency. This magnetic force is implemented into a simplified analytical machine dynamic model and the correlations between the rotor dynamics, electromagnetic, oil film characteristics of the sleeve bearings, and the stiffness and damping of a soft foundation are mathematically described. The derived results are clarified using an example that shows the influence of the rotor speed and the direction of the magnetic force on the vibration behavior. On one hand the aim of the paper is to show the mathematical correlations, based on a simplified model. On the other hand, the aim is to derive a method for calculating the forced vibrations — as a worst case — caused by a static rotor eccentricity. Therefore, the paper shall prepare the basis for implementing this method in more detailed numerical programs, e.g., finite element programs.
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Chen-Hui, Jia, Du Cai-Feng, and Qiu Ming. "Research on Nonlinear Dynamic Characteristics and Stability of Aerodynamic Bearings." Open Mechanical Engineering Journal 8, no. 1 (September 16, 2014): 243–50. http://dx.doi.org/10.2174/1874155x01408010243.
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In order to research the conical spiral groove aerodynamic bearings, the lubrication mathematical model of the bearings was established. The Reynolds equation of the laminar flow condition is used to calculate the partial differential equation of the perturbation pressure with the local finite difference method. Through calculating the stiffness and damping coefficient, the influence of the speed of law and eccentricity ratio on the dynamic characteristic coefficients has been gained. The mathematical model for the stability of the bearing-rotor system is established to study the influence law of speed influence of the law of speed and eccentricity ratio on the stability. The results show that the influence of the bearing's speed and eccentricity on the dynamic characteristics is significant. A reasonable choice of the bearing's speed and eccentricity contributes to improve the dynamic characteristics and the stability of the bearing-rotor system.
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Wan, Shuting, and Yuling He. "INVESTIGATION ON STATOR AND ROTOR VIBRATION CHARACTERISTICS OF TURBO-GENERATOR UNDER AIR GAP ECCENTRICITY FAULT." Transactions of the Canadian Society for Mechanical Engineering 35, no. 2 (June 2011): 161–76. http://dx.doi.org/10.1139/tcsme-2011-0010.
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This paper investigates the stator and the rotor vibration characteristics of turbo-generator under the air gap eccentricity fault. Firstly the air gap magnetic flux density of the fault is deduced, and the formula of the magnetic pull per unit area acting on the stator and the unbalanced magnetic pulls of x-axis and y-axis acting on the rotor are respectively gotten. Then the static eccentricity, the dynamic eccentricity and the mixed eccentricity are respectively studied to analyze the stator and the rotor vibration characteristics. Finally experiments are done on a SDF-9 non-salient fault simulating generator to verify the theoretical results. The investigation results of this paper will be beneficial to the air gap eccentricity fault diagnosis of turbo-generator.
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Wu, Quanhui, Yazhou Sun, Wanqun Chen, Guoda Chen, Qingshun Bai, and Qingchun Zhang. "Effect of motor rotor eccentricity on aerostatic spindle vibration in machining processes." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 232, no. 7 (April 24, 2017): 1331–42. http://dx.doi.org/10.1177/0954406217705686.
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In ultra-precision machining field, the air motorized spindle which is composed of a motor and an air bearing, plays a major role. In air motorized spindle, the motor eccentricity between the stator and the rotor is inevitably introduced during the manufacturing process, which directly affects the machining results of workpiece surface, and this phenomenon is particularly unwanted in machining. However, little attention has been paid to the motor eccentricity of air motorized spindle. In this paper, a new integrated electromechanical coupling method for estimating unbalanced force in air motorized spindle is presented, and the effects of motor rotor eccentricity on surface topography in ultra-precision processes are analyzed. An electromagnetic-mechanical method is used to study the coupling effects between the motor rotor and the aerostatic spindle. Meanwhile, the motor rotor and the aerostatic spindle are analyzed as a whole. In order to clearly describe the electromagnetic–mechanical method, the ultra-precision spindle for potassium dihydrogen phosphate crystal machining tool is selected as the research object, and the model of air motorized spindle and motor rotor eccentricity are presented. Besides, in order to assess the impact of the radial magnetic force caused by motor rotor eccentricity on the spindle performance, a range of rotor eccentricities is calculated. Additionally, the influence of the motor rotor eccentricity on the dynamic response of spindle is further analyzed. It is found that motor rotor eccentricity has a significant influence on the spindle vibration, which dramatically reduces the processing quality. Finally, the machining experiments are carried out, and the flatness errors of the workpiece caused by the motor rotor eccentricity are obtained by the wavelet method. The experimental results are consistent with the analysis results, which verifies the reliability of this method. This study is quite meaningful for deeply understanding the influence of motor rotor eccentricity on the machined surface.
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Zhu, Youfeng, Zibo Wang, Qiang Wang, Xinhua Liu, Hongyu Zang, and Liang Wang. "Nonlinear Dynamic Analysis of Rotor Rub-Impact System." Shock and Vibration 2019 (November 29, 2019): 1–20. http://dx.doi.org/10.1155/2019/4867364.
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A dynamic model of a double-disk rub-impact rotor-bearing system with rubbing fault is established. The dynamic differential equation of the system is solved by combining the numerical integration method with MATLAB. And the influence of rotor speed, disc eccentricity, and stator stiffness on the response of the rotor-bearing system is analyzed. In the rotor system, the time history diagram, the axis locus diagram, the phase diagram, and the Poincaré section diagram in different rotational speeds are drawn. The characteristics of the periodic motion, quasiperiodic motion, and chaotic motion of the system in a given speed range are described in detail. The ways of the system entering and leaving chaos are revealed. The transformation and evolution process of the periodic motion, quasiperiodic motion, and chaotic motion are also analyzed. It shows that the rotor system enters chaos by the way of the period-doubling bifurcation. With the increase of the eccentricity, the quasi-periodicity evolution is chaotic. The quasiperiodic motion evolves into the periodic three motion phenomenon. And the increase of the stator stiffness will reduce the chaotic motion period.
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Zhao, Jianhua, Weidong Yan, Ziqi Wang, Dianrong Gao, and Guojun Du. "Study on Clearance-Rubbing Dynamic Behavior of 2-DOF Supporting System of Magnetic-Liquid Double Suspension Bearing." Processes 8, no. 8 (August 12, 2020): 973. http://dx.doi.org/10.3390/pr8080973.
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As a new type of suspension bearing, Magnetic-Liquid Double Suspension Bearing (MLDSB) is mainly supported by electromagnetic suspension and supplemented by hydrostatic supporting. Its bearing capacity and stiffness can be greatly improved. Because of the small liquid film thickness (it is smaller 10 times than air gap), the eccentricity, crack, bending of the rotor, and the assembly error, it is easy to cause a clearance-rubbing fault between the rotor and stator. The coating can be worn and peeled, the operating stability can be reduced, and then it is one of the key problems of restricting the development and application of MLDSB. Therefore, the clearance-rubbing dynamic equation of 2-DOF system of MLDSB is established and converted into Taylor Series form and the nonlinear components are retained. Dimensionless treatment is carried out by dimensional normalization method. Finally, the rotor displacement response under different rotor eccentricity ratio and rotating speeds is numerically simulated. The studies show that the trajectory of the rotor is periodic elliptic without clearance-rubbing phenomenon when the eccentricity ratio is less than 0.2, while the rotor is greatly affected by the rotation speed and a variety of motions, such as single-period, quasi-period, double-period and chaos, are presented when greater than 0.3. Within the largest range of rotating speed and eccentricity ratio, the rotor presents the single-period trajectory, and then the number of Poincare mapping point is 1, without a clearance-rubbing fault. When the rotational speed is in the scope of (9, 13) krpm and the eccentricity ratio is in the scope of (0.27, 0.4), the number of Poincare mapping point is more than one, the maximum dimensionless rubbing force is −5.7, and then clearance-rubbing fault occurs. The research can provide a theoretical basis for the safe and stable operation of MLDSB.
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Dai, Bing, Guang Bin Yu, Jun Peng Shao, and Long Huang. "Eccentricity and Rotational Speed Effect on the Rotor-Bearing." Applied Mechanics and Materials 274 (January 2013): 237–40. http://dx.doi.org/10.4028/www.scientific.net/amm.274.237.
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Bearing dimensionless nonlinear oil film force model is deduced based on Capone theory of cylindrical bearings in this paper. Jeffcot rigid rotor-bearing system dynamic equations are built based on nonlinear dynamics, bifurcation, chaos theory. Eccentricity increases with the speed of the system by writing MATLAB codes. It appears the periodic motion, times of periodic motion and a series of non-linear kinetics. The system eccentricity increases with a series of emergence of non-linear dynamics when speed conditions is fixed, which is the actual system design’s basis. The finite element model of gas turbine rotor-bearing system is built by ANSYS software platform in this paper. The radial bearing deformation relationship are obtained by deformation theory of centrifugal force at high speed bearing radial deformation.
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Ebrahimi, Bashir Mahdi, Mohammad Etemadrezaei, and Jawad Faiz. "Dynamic eccentricity fault diagnosis in round rotor synchronous motors." Energy Conversion and Management 52, no. 5 (May 2011): 2092–97. http://dx.doi.org/10.1016/j.enconman.2010.12.017.
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Li, Chao Feng, Jie Liu, Qin Liang Li, and Bang Chun Wen. "Research on Dynamic Characteristic and Experiments of Double-Disc Rotor System with Oil Film Support." Advanced Materials Research 442 (January 2012): 235–39. http://dx.doi.org/10.4028/www.scientific.net/amr.442.235.
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Multi-DOF model of double-disc rotor-bearing system taking oil film support into account is established, and Newmark method is also applied to dynamic response of continuous system. To simplify the calculation in double-disc eccentric situation, the research aims at time domain, frequency response and bifurcation solution, simultaneously qualitative experiments are also carried out on the experiment bench. Experiments show that the numerical algorithm and calculation results are credible. The conclusions conclude: For the rotor system shown in the paper, with the other parameters constant, small eccentricity system is prone to appear quasi-periodic instability, but for big eccentricity system it is period-doubling instability, and the instability speed will increase with eccentricity enlargement; initial eccentric phase has severe effects on the dynamic characteristic of system, so it is worth studying it more in depth. This method and results in this paper provides a theoretical reference for stability analysis and vibration control in more complex relevant rotor-bearing system.
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Shuraiji, Ahlam Luaibi. "The effect of static and dynamic eccentricities on the performance of flux reversal permanent magnet machine." International Journal of Power Electronics and Drive Systems (IJPEDS) 11, no. 2 (June 1, 2020): 634. http://dx.doi.org/10.11591/ijpeds.v11.i2.pp634-640.
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This study investigates the effect of static and dynamic eccentricities on the performances of flux reversal permanent magnet (FRPM) machine with even rotor pole number, i.e. FRPM machine with 12/10 stator/rotor combination. No-load and load performances of the machine are investigated under three rotor operating conditions including centricity, static eccentricity and dynamic eccentricity. The investigation has been carried out using 2D-FEA. It has been revealed that the 12/10 FRPM machine under normal operating condition has no unbalanced magnetic force, due to the even pole number of the rotor. On the other hand, such undesirable feature would be presented in the 12/10 FRPM machine as a result of the existing of static and dynamic eccentricities. Both static and dynamic eccentric machines exhibit unbalanced three-phase flux linkage as well as back-EMF. Moreover, three operating conditions of the investigated machine have the same fundamental cogging torque harmonic. However, low order harmonics are existed in the static and dynamic centric machines and are not found in the centric machine. Furthermore, about 16% less torque ripple delivered by the centric machine compared with both static and dynamic counterparts.
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Lee, Hoon Ki, Tae Kyoung Bang, Jong Hyeon Woo, Hyo Seob Shin, and Jang Young Choi. "Electromagnetic Characteristic Analysis of Permanent Magnet Synchronous Machine Considering Current Waveform According to Static Rotor Eccentricity." Applied Sciences 10, no. 23 (November 27, 2020): 8453. http://dx.doi.org/10.3390/app10238453.
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In this study, we performed an electromagnetic characteristic analysis of a permanent magnet synchronous machine considering the current waveform based on static rotor eccentricity. First, the characteristics of the back electromotive force were analyzed through the no-load analysis of the analysis model according to static rotor eccentricity. Next, a dynamic analysis was performed through mathematical modeling of a permanent magnet synchronous motor and PWM method. The input current during operation was derived through the dynamic analysis, and the core loss analysis was performed using derived input current. The core loss analysis was performed using the case where the fundamental wave current was applied and the input current derived through the dynamic analysis, and the results were compared.
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Du, Jianmin, and Yan Li. "Analysis on the Variation Laws of Electromagnetic Force Wave and Vibration Response of Squirrel-Cage Induction Motor under Rotor Eccentricity." Electronics 12, no. 6 (March 8, 2023): 1295. http://dx.doi.org/10.3390/electronics12061295.
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Aiming to address the rotor eccentricity problem caused by various factors, such as manufacturing, operation and the mass imbalance of the induction motor, the variation law of electromagnetic force wave and vibration response under rotor eccentricity during no-load operation is investigated. To begin with, on the basis of the air-gap permeability, the air-gap magnetic density components under static and dynamic eccentricity are analyzed by using the analytical method. The order and amplitude expressions of the radial electromagnetic force generated by the interaction of harmonics are obtained. Subsequently, a finite element model of the electromagnetic field was developed, and the space-time spectrum of the electromagnetic force was obtained by combining the 2D Fourier analysis. Finally, the electromagnetic force wave is used as a load to investigate the electromagnetic vibration response under different rotor eccentric forms. The effect of rotor eccentricity on the vibration response of the motor is quantitatively analyzed by using the spectral analysis method. The method of analyzing electromagnetic force wave and vibration response can also provide a reference for the same type of motor.
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Baskharone, E. A., and S. J. Hensel. "Interrelated Rotordynamic Effects of Cylindrical and Conical Whirl of Annular Seal Rotors." Journal of Tribology 113, no. 3 (July 1, 1991): 470–80. http://dx.doi.org/10.1115/1.2920648.
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A comprehensive approach for computing the dynamic coefficients of an annular seal is presented. The coefficients are partly those associated with a uniform lateral eccentricity mode of the rotor (known as the cylindrical whirl mode) and with an angular eccentricity (which gives rise to a conical whirl type). The rotor excitation effects in both cases are treated as interrelated by recognizing the fluid-exerted moments resulting from the lateral eccentricity and the net fluid force resulting from the angular eccentricity. In all cases, the rotor is assumed to undergo a whirling motion around the housing centerline. The computational procedure is a finite-element perturbation model in which the zeroth-order undisplaced-rotor flow solution in the clearance gap is obtained through a Petrov-Galerkin approach. Next, the rotor translational and angular eccentricities, considered to be infinitesimally small, are perceived to cause virtual distortions of varied magnitudes in the finite element assembly which occupies the clearance gap. Perturbations in the flow variables including, in particular, the rotor surface pressure, are then obtained by expanding the finite-element equations in terms of the rotor eccentricity components. The fluid-exerted forces and moments are in this case computed by integration over the rotor surface, and the full matrix of rotordynamic coefficients, in the end, obtained. The computational model is verified against a bulk-flow model for a sample case involving a straight annular seal. Choice of this sample model for validation was made on the basis that no other existing model has yet been expanded to account for the mutual interaction between the cylindrical and conical rotor whirl, which is under focus in this study.
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Han, Tian, Jie Bai, and Zhong Jun Yin. "Dynamic Simulation Analysis of a Cracked Flexible Rotor Supported on Rotor-Rolling Bearing Based on Virtual Prototyping Technology." Advanced Materials Research 156-157 (October 2010): 293–97. http://dx.doi.org/10.4028/www.scientific.net/amr.156-157.293.
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The complex nonlinear dynamics of a rotor-rolling bearing system with crack is built by dynamic simulation software ADAMS. The transverse vibration response and swing response of rotor are studied on the basis of considering both the nonlinear contact force of rolling bearing and the impact of stiffness caused by crack. Furthermore, the influence factors of transverse vibration response are researched including speed, crack depth, crack angle and eccentricity. The simulation analysis demonstrated that it is an effective method to solve nonlinear dynamics of rotor-rolling bearing system with crack based on virtual prototyping technology. It provides a new method of feasibility study for fault diagnosis in the future.
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Gu, Can song, Zhao cheng Yuan, Zheng rui Yang, Jia xin Liu, and Hong liang Li. "Dynamic characteristics of high-speed gasoline engine turbocharger based on thermo-elasto-hydrodynamic lubrication bearing model and flexible multibody dynamics method." Science Progress 103, no. 1 (January 2020): 003685041989771. http://dx.doi.org/10.1177/0036850419897712.
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A flexible multibody dynamic calculation model based on thermo-elasto-hydrodynamic lubrication bearing model was established. This numerical simulation method provided a more realistic turbocharger calculation model and a more reliable theoretical support for studying the dynamic vibration characteristics of the floating ring bearing turbocharger system. In order to fully consider the dynamic characteristics of each component, the behavior of the floating ring bearing was described by generalized incompressible Reynolds equation in thermo-elasto-hydrodynamic lubrication model. The flexible body substructure models were established by the modal synthesis method. Based on this model, the direct mathematical model of the relationship between the eccentricity of the rotor and the oil film clearance on the turbocharger’s surface vibration was established. The influence of eccentricity and oil film thickness on the surface vibration of the turbocharger body was calculated by transient dynamics method. The results showed that the eccentricity of the rotor and the vibration of turbocharger housing were monotonic functions, but the interaction between the whirl of internal and external oil films made the mechanism of the influence of the oil film thickness on the turbocharger body’s vibration complicated. The research provided a new idea for the structural vibration and synchronous noise control of the supercharger.
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Wileman, J., and I. Green. "The Rotor Dynamic Coefficients of Eccentric Mechanical Face Seals." Journal of Tribology 118, no. 1 (January 1, 1996): 215–24. http://dx.doi.org/10.1115/1.2837081.
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The Reynolds equation is extended to include the effects of radial deflection in a seal with two flexibly mounted rotors. The resulting pressures are used to obtain the forces and moments introduced in the axial and angular modes by the inclusion of eccentricity in the analysis. The rotor dynamic coefficients relating the forces and moments in these modes to the axial and angular deflection are shown to be the same as those presented in the literature for the concentric case. Additional coefficients are obtained to express the dependence of these forces and moments upon the radial deflections and velocities. The axial force is shown to be decoupled from both the angular and radial modes, but the angular and radial modes are coupled to one another by the dependence of the tilting moments upon the radial deflections. The shear stresses acting upon the element faces are derived and used to obtain the radial forces acting upon the rotors. These forces are used to obtain rotor dynamic coefficients for the two radial degrees of freedom of each rotor. The additional rotor dynamic coefficients can be used to obtain the additional equations of motion necessary to include the radial degrees of freedom in the dynamic analysis. These coefficients introduce additional coupling between the angular and radial degrees of freedom, but the axial degrees of freedom remain decoupled.
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Sun, Dan, Sheng-Yuan Li, Huan Zhao, and Cheng-Wei Fei. "Numerical Investigation on Static and Rotor-Dynamic Characteristics of Convergent-Tapered and Divergent-Tapered Hole-Pattern Gas Damper Seals." Materials 12, no. 14 (July 21, 2019): 2324. http://dx.doi.org/10.3390/ma12142324.
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To study the influence of taper seal clearance on the static and rotor-dynamic characteristics of hole-pattern damper seals, this paper develops three-dimensional transient computational fluid dynamic methods, which comprise single-frequency and multi-frequency elliptical orbit whirl model, by the transient solution combined with a mesh deformation technique. Through the investigations, it is illustrated that: (1) In the present paper, the leakage rates of convergent-tapered hole-pattern damper seals are less than divergent-tapered hole-pattern damper seals for the same average seal clearance, and the maximum relative variation reaches 16%; (2) Compared with a constant clearance hole-pattern damper seal, the maximum relative variation of the rotor-dynamic coefficients is 1,865% for nine taper degrees in this paper; (3) Convergent-tapered hole-pattern damper seals have smaller reaction forces and effective damping coefficient, larger cross-over frequency, and direct stiffness coefficient, while divergent-tapered damper seals have the opposite effects; (4) Divergent-tapered hole-pattern damper seals alleviate the rotor whirl because of a larger effective damping coefficient when the rotor system has large natural frequency and small eccentricity. Convergent-tapered damper seals provide both sealing and journal bearing capabilities at the same time, and are more advantageous to the stability of the rotor system when rotor eccentricity is the main cause of rotor instability.
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Zhou, Shihua, Zhaohui Ren, Guiqiu Song, and Bangchun Wen. "Dynamic Characteristics Analysis of the Coupled Lateral-Torsional Vibration with Spur Gear System." International Journal of Rotating Machinery 2015 (2015): 1–14. http://dx.doi.org/10.1155/2015/371408.
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A sixteen-degree-of-freedom (16-DOF) lumped parameter dynamic model taking into account the gravity, eccentricity, bearing clearance, transmission error, and coupled lateral-torsional vibration is established. Based on the dynamical equation, the dynamic behaviors of the spur gear rotor bearing system are investigated by using Runge-Kutta method. The research focuses on the effect of rotational speed, eccentricity, and bearing clearance and nonlinear response of the coupled multibody dynamics is presented by vibration waveform, spectrum, and 3D frequency spectrum. The results show that the rotational frequency of the driven gear appears in the driving gear, and the dynamic characteristics of gears have obvious differences due to the effects of the gear assembly and the coupled lateral-torsional vibration. The bearing has its own resonance frequency, and the effect of the variable stiffness frequency of the bearings should be avoided during the system design. The results presented in this paper show an analysis of the coupled lateral-torsional vibration of the spur gear system. The study may contribute to a further understanding of the dynamic characteristics of such a spur gear rotor bearing system.
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Xiang, Ling, and Lan Lan Hou. "Nonlinear Dynamic Analysis of Rub-Impact Rotor System under Different Parameters." Advanced Materials Research 712-715 (June 2013): 1355–58. http://dx.doi.org/10.4028/www.scientific.net/amr.712-715.1355.
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Nonlinear dynamic-behavior analysis of rotor system under different parameters is presented. The derivation of nonlinear dynamic equations under the action of rub-impact force is set up basing on Jeffcott model, and the system bifurcation characteristics and influences has been investigated under the ratio of operating angular velocity and the rotor’ natural angular velocity influence by numerical analysis. Bifurcation and dynamical behaviors of nonlinear of system with the changes of argument (that is the ratio of operating angular velocity and the rotor’ natural angular velocity) under several specific parameters are analyzed. The results show that the ratio, rotor eccentricity and rotor stiffness have great effect on the dynamical behaviors of nonlinear system.
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Shi, YF, M. Li, GH Zhu, and Y. Yu. "Dynamics of a rotor system coupled with water-lubricated rubber bearings." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 232, no. 23 (January 22, 2018): 4263–77. http://dx.doi.org/10.1177/0954406217750942.
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Dynamic behaviour is significantly important in the design of large rotor systems supported on water-lubricated rubber bearings. In this study, the mathematical model of elastohydrodynamic lubrication of the bearing is established based on the theory of hydrodynamic lubrication after considering the elastic deformation of rubber, and the dynamic characteristics of water-lubricated rubber bearings are analysed under small perturbation conditions according to the load increment method and the finite difference method. Next, the differential equation of rotor systems coupled with the water-lubricated rubber bearing is deduced using Lagrange’s approach, and its critical speeds, stability, and unbalanced responses are analysed in detail. The numerical results show that several parameters, such as the eccentricity, length–diameter ratio, and clearance of bearing and the rotating speed of the rotor, have a great impact on the dynamic performance of water-lubricated rubber bearings, and this influence cannot be ignored, especially in the case of large eccentricity ratios. The dynamic characteristics of rotor systems guided by water-lubricated rubber bearings reveal that the critical speeds are much lower than the ones under the rigid supports because of the elastic deformation, and they also indicate that the rotor system supported on water-lubricated rubber bearings has a weaker stability. In addition, the steady-state responses of the rotor system are analysed when the mass unbalance of the propeller exists, and the effect of the thickness of the rubber liner is also considered.
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Gmu¨r, T. C., and J. D. Rodrigues. "Shaft Finite Elements for Rotor Dynamics Analysis." Journal of Vibration and Acoustics 113, no. 4 (October 1, 1991): 482–93. http://dx.doi.org/10.1115/1.2930212.
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This paper presents efficient C0-compatible finite elements for the modelling of rotor-bearing systems. The proposed linearly tapered elements, which have a variable number of nodal points, are simple and attractive from a cost viewpoint. They include the effects of translational and rotatory inertia, gyroscopic moments, internal viscous and hysteretic damping, shear deformations, and mass eccentricity. Developed from the weak formulation associated with the differential equations governing the transverse dynamic behavior of rotors, these elements show a convergence pattern similar to the one obtained with conventional C1-compatible shaft elements. Numerical examples are provided, which compare the proposed approach to the C1-formulation or to previously published results.
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Zhang, Haibo, Yi Liu, and Xin Huang. "Nonlinear Dynamic Performance of a Bolt-Disc Rotor with the Position Error of Circumferential Bolt-Holes." Shock and Vibration 2021 (May 7, 2021): 1–10. http://dx.doi.org/10.1155/2021/6639375.
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The bolt-holes in the assembly discs are designed to limit the circumferential displacement of bolts for the bolt-disc rotor. The position error of circumferential bolt-holes is created in a three-dimensional model of bolt-disc rotor. The distribution of nonuniform stress and deformation is acquired according to finite element approach. Static results demonstrate that the position error of bolt-holes leads to obvious concomitant unbalances including constant mass eccentricity and speed-variant bending under the influence of large tightening force. When these unbalance factors are taken into consideration, dynamic performance such as instability areas and nonlinear motions are analyzed by Newton iterative process and a prediction-correction calculation method. Dynamic results show that rotor flexure enables the systematic stability decreased obviously because of this position error. There is a special phenomenon compared to monobloc rotor that the vibration amplitude proceeds to rise when rotating speed exceeds the critical speed. Moreover, the allowable position error of bolt-holes is obviously smaller than that of monobloc rotor and uneven tightening is a feasible way to reduce adverse effects on the dynamic properties when position error appears. This work proposes a static-dynamic approach to investigate the dynamics of imprecise bolt-disc rotor and establishes the relationship between machining error and dynamic features.
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Mahdiuon-Rad, S., S. R. Mousavi-Aghdam, M. Reza Feyzi, and M. B. B. Sharifian. "Analysis of PM Magnetization Field Effects on the Unbalanced Magnetic Forces due to Rotor Eccentricity in BLDC Motors." Engineering, Technology & Applied Science Research 3, no. 4 (August 11, 2013): 461–66. http://dx.doi.org/10.48084/etasr.296.
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This paper investigates both static and dynamic eccentricities in single phase brushless DC (BLDC) motors and analyzes the effect of the PM magnetization field on unbalanced magnetic forces acting on the rotor. Three common types of PM magnetization field patterns including radial, parallel and sinusoidal magnetizations are considered. In both static and dynamic eccentricities, harmonic components of the unbalanced magnetic forces on the rotor are extracted and analyzed. Based on simulation results, the magnetization fields that produce the lowest and highest unbalanced magnetic forces are determined in rotor eccentricity conditions.
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Clappier, Marcel, and Lothar Gaul. "FE-BE computation of electromagnetic noise of a permanent-magnetic excited synchronous ma-chine considering dynamic rotor eccentricity." MATEC Web of Conferences 211 (2018): 18005. http://dx.doi.org/10.1051/matecconf/201821118005.
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Electromagnetic noise in Electrical Machines (EMs) occurs due to vibrations caused by magnetic forces acting onto rotor and stator surface. This is the dominant source for the considered permanent-magnetic excited synchronous machine in this paper. The radiated electromagnetic noise is sequentially calculated by a Finite Element (FE) and Boundary Element (BE) computation. An electromagnetic FE model is created to determine magnetic forces. Structure-borne sound and rotor dynamics are calculated using a structural dynamic FE model for the EM housing and the rotor. In order to predict resonance frequencies and amplitudes as reliable as possible, it is important to know the direction-dependent stiffness of the laminated rotor stacks and mechanical joints as well as their structural damping. Thereby, the properties of the laminated stack can be determined experimentally by a shear and dilatation test. Mechanical joint properties can be modelled by Thin-Layer Elements (TLEs) and the overall damping by the model of constant hysteretic damping. The radiated sound power is determined by a direct BE computation. The influence of dynamic rotor eccentricity on radiated sound power is examined for a run-up of the EM. All FE models are verified by data from experimental modal analysis.
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Wei, Yuan, Zhaobo Chen, and Earl H. Dowell. "Nonlinear Characteristics Analysis of a Rotor-Bearing-Brush Seal System." International Journal of Structural Stability and Dynamics 18, no. 05 (May 2018): 1850063. http://dx.doi.org/10.1142/s0219455418500633.
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The vibration response and nonlinear dynamic behavior of a rotor-bearing-brush seal system were investigated with a new seal force model of the brush seal. The nonlinear oil–film force model was adopted based on a short bearing assumption. The dimensionless equation of motion was solved using the fourth order Runge–Kutta method. The effects of key parameters including rotor speed, installation spacing of the brush seal, disk eccentricity, disk mass, and journal mass on the nonlinear dynamic characteristics of rotor-bearing-brush seal system were determined and compared under different operating conditions with a bifurcation diagram, time history, axis orbit, poincaré map, frequency spectrum, and spectrum cascade. The results showed that the system response contained various nonlinear phenomena, such as periodic motion, multi-periodic motion, and quasi-periodic motion. The interaction of the rotor speed, installation spacing of the brush seal, disk eccentricity, disk mass, and journal mass could seriously affect the stability and working condition of the system. This study provides a theoretical support for the selection of key design parameters and further understanding of the nonlinear characteristics of rotor-bearing-seal systems with a brush seal.
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Silwal, Bishal, Paavo Rasilo, Anouar Belahcen, and Antero Arkkio. "Influence of the rotor eccentricity on the torque of a cage induction machine." Archives of Electrical Engineering 66, no. 2 (June 27, 2017): 383–96. http://dx.doi.org/10.1515/aee-2017-0029.
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AbstractThe non-uniform air gap in an electrical machine caused by rotor eccentricity creates an asymmetrical flux-density distribution in the air gap. This can affect the nominal torque produced by the machine. Eccentricity also produces forces that act on the rotor which may also have an effect on the torque. Thus, it is important to know how the torque of the machine behaves. In this paper, the torque of a cage induction machine is studied when the machine has dynamic eccentricity. The study is performed using the finite element method and a magnetic vector potential formulation. The torque is calculated by the method of energy balance. The harmonic components of the torque are also analyzed. The results show that the machine under eccentricity does not exhibit the same torque as a normal healthy machine. The harmonic components around the first principal slot harmonic is most affected.
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Qian, Kun Xi, and Teng Jing. "Route Chart to Stabilizing Permanent Maglev Rotator." Advanced Materials Research 785-786 (September 2013): 1586–89. http://dx.doi.org/10.4028/www.scientific.net/amr.785-786.1586.
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Permanent maglev has been since long recognized to be unstable because of Earnshaw's theory, which theoretically proved that permanent maglev can not achieve stable equilibrium in static state. How about that in dynamic state, for example, about a rotator, nobody has given an answer until now actually. A permanent maglev pump and a permanent maglev turbine have been developed, by using a patented permanent magnetic bearing developed by the author. Experiments demonstrated, there is a critic speed either in the pump or in the turbine, under which the rotors in the pump and the turbine have a maximal eccentricity being possible to reach the gap between the rotor and the stator. That means the rotors have contact with the stators occasionally, and thus the rotor is not suspended. In case the rotating speed is higher than this critic speed, the rotors' eccentricity will be remarkably smaller than the gap between the rotor and the stator, that is to say the rotor is stably levitated. Further investigation exhibtes that at the critic speed a so-called gyro-effect is generated which stabilizes the rotor, just like a gyro standing over a ball, if the rotating speed is large enough it can be stable over the ball. The critic speed, essentially to be minimal stable speed of the rotor, depends on the rotating inertia of the rotor and the bearing force, the larger the inertia and the larger the force, the lower the critic speed. Conclusively, a route chart to stabilization of permanent maglev rotator has been clear: in static state, permanent maglev is unstable (Earnshaw's theory); as the rotating speed gradually increases but not up to a critic speed, the permanent maglev rotator is also unstable; in case that the speed equals or is larger than this critic speed, the permanent maglev rotator is suspended stably because of gyro-effect; the critic speed is affected by rotating inertia of the rotor and the bearing force, by larger inertia and larger bearing force, the critic speed will be smaller.
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Yao, Jianfei, Jinji Gao, Ya Zhang, and Weimin Wang. "The Dynamic Analysis of Two-Rotor Three-Bearing System." International Journal of Rotating Machinery 2015 (2015): 1–15. http://dx.doi.org/10.1155/2015/342636.
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A finite element model considering the shear effect and gyroscopic effect is developed to study the linear and nonlinear dynamic behavior of two-rotor three-bearing system named N+1 configuration with rub-impact in this paper. The influence of rotational speed, eccentric condition, and the stiffness of coupling on the dynamic behavior of N+1 configuration and the propagation of motion are discussed in detail. The linear rotordynamic analysis included an evaluation of rotor critical speed and unbalance response. The results show that the critical speed and unbalance response of rotors are sensitive to coupling stiffness in N+1 configuration. In the nonlinear analysis, bifurcation diagram, shaft-center trajectory, amplitude spectrum, and Poincaré map are used to analyze the dynamic behavior of the system. The results of the research transpire that these parameters have the great effects on the dynamic behavior of the system. The response of the system with rub-impact shows abundant nonlinear phenomena. The system will exhibit synchronous periodic motion, multiperiodic motion, quasiperiodic motion, and chaotic motion patterns under rotor-stator rub interaction conditions. The dynamic response is more complicated for flexible coupling and two mass eccentricities than that of system with rigid coupling and one mass eccentricity.
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Soulas, Thomas, and Luis San Andres. "A Bulk Flow Model for Off-Centered Honeycomb Gas Seals." Journal of Engineering for Gas Turbines and Power 129, no. 1 (March 1, 2002): 185–94. http://dx.doi.org/10.1115/1.2227031.
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A computational analysis for prediction of the static and dynamic forced performance of gas honeycomb seals at off-centered rotor conditions follows. The bulk-flow analysis, similar to the two-control volume flow model of Kleynhans and Childs (1997, “The Acoustic Influence of Cell Depth on the Rotordynamic Characteristics of Smooth-Rotor/Honeycomb-Stator Annular Gas Seals,” ASME J. Eng. Gas Turbines Power, 119, pp. 949–957), is brought without loss of generality into a single-control volume model, thus simplifying the computational process. The formulation accommodates the honeycomb effective cell depth, and existing software for annular pressure seals and is easily upgraded for damper seal analysis. An analytical perturbation method for derivation of zeroth- and first-order flow fields renders the seal equilibrium response and frequency-dependent dynamic force impedances, respectively. Numerical predictions for a centered straight-bore honeycomb gas seal shows good agreement with experimentally identified impedances, hence validating the model and confirming the paramount influence of excitation frequency on the rotordynamic force coefficients of honeycomb seals. The effect of rotor eccentricity on the static and dynamic forced response of a smooth annular seal and a honeycomb seal is evaluated for characteristic pressure differentials and rotor speeds. Leakage for the two seal types increases slightly as the rotor eccentricity increases. Rotor off-centering has a pronounced nonlinear effect on the predicted (and experimentally verified) dynamic force coefficients for smooth seals. However, in honeycomb gas seals, even large rotor center excursions do not sensibly affect the effective local film thickness, maintaining the flow azimuthal symmetry. The current model and predictions thus increase confidence in honeycomb seal design, operating performance, and reliability in actual applications.
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Shi, Mingming, Yongfeng Yang, Wangqun Deng, Jianjun Wang, and Chao Fu. "Analysis of Dynamic Characteristics of Small-Scale and Low-Stiffness Ring Squeeze Film Damper-Rotor System." Applied Sciences 12, no. 14 (July 16, 2022): 7167. http://dx.doi.org/10.3390/app12147167.
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Rotor machinery supports are susceptible to fracture arising from multi-period or irregular transient vibration and even the inconspicuous fatigue phenomenon. The novel dynamic model of a rotor mounted on the floating ring squeeze film damper (SFD) was developed. The proposed SFD implements low stiffness and small scale to overcome the deficiency. Based on the theory of hydrodynamic lubrication, the Reynolds equations on the working principle of the floating ring are established. Then, the dynamic characteristics of the rotor system during maneuvers, with the floating ring SFD supports, are subsequently examined by adopting the finite difference method. In addition, the oil film whirl mechanism of the floating ring SFD is demonstrated according to the transient analysis of the fluid–structure interaction model. The results of the SFD simulation reveal that, with increasing eccentricity ratio, both the inner and outer oil film pressure tend to be larger due to the shrinkage of the effective coverage of oil film. The maximum oil film pressure and bearing capacity increase nonlinearly within a certain eccentricity ratio range. Through the comparisons of the results, the vibration suppression effects of the proposed SFD are analyzed. This work will provide the practical reference for the dynamic design of the rotor support system.
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Nan, Guofang, Yujie Zhu, Yang Zhang, and Wei Guo. "Nonlinear Dynamic Analysis of Rotor-Bearing System with Cubic Nonlinearity." Shock and Vibration 2021 (May 25, 2021): 1–11. http://dx.doi.org/10.1155/2021/8878319.
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Nonlinear dynamic characteristics of a rotor-bearing system with cubic nonlinearity are investigated. The comprehensive effects of the unbalanced excitation, the internal clearance, the nonlinear Hertzian contact force, the varying compliance vibration, and the nonlinear stiffness of support material are considered. The expression with the linear and the cubic nonlinear terms is adopted to characterize the synthetical nonlinearity of the rotor-bearing system. The effects of nonlinear stiffness, rotating speed, and mass eccentricity on the dynamic behaviors of the system are studied using the rotor trajectory diagrams, bifurcation diagrams, and Poincaré map. The complicated dynamic behaviors and types of routes to chaos are found, including the periodic doubling bifurcation, sudden transition, and quasiperiodic from periodic motion to chaos. The research results show that the system has complex nonlinear dynamic behaviors such as multiple period, paroxysmal bifurcation, inverse bifurcation, jumping phenomena, and chaos; the nonlinear characteristics of the system are significantly enhanced with the increase of the nonlinear stiffness, and the material with lower nonlinear stiffness is more conducive to the stable operation of the system. The research will contribute to a comprehensive understanding of the nonlinear dynamics of the rotor-bearing system.
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Petryna, Janusz, Arkadiusz Duda, and Maciej Sułowicz. "Eccentricity in Induction Machines—A Useful Tool for Assessing Its Level." Energies 14, no. 7 (April 2, 2021): 1976. http://dx.doi.org/10.3390/en14071976.
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In the condition monitoring of induction machines operating in various industry sectors, the assessment of eccentricity is as important as the assessment of the condition of windings, bearings, mechanical vibrations or noise. The reasons for the eccentricity can be various; for example, rotor imbalance, damage or wear of the bearings, improper alignment of the rotor and the load machine and finally, assembly errors after overhaul. Disregard of this phenomenon during routine tests may result in the development of vibrations transmitted to the stator windings, faster wear of the bearings and even, in extreme cases, rubbing of the rotor against the stator surface and damage to the windings and local overheating of the machine core. On the basis of years of experience in the diagnosis of large induction machines operating in various industries, the article deals with the problem of developing reliable indicators for assessing the levels of commonly accepted types of eccentricity. Starting from field calculations and analyzing various cases of eccentricity, the methodology for determining the indicators for evaluation from the stator current spectrum is shown. The changes in the values of these indices for various cases of simultaneous occurrence of static and dynamic eccentricity are shown. The calculation results were verified in the laboratory. Also shown are three interesting cases from diagnostic practice in the evaluation of high-power machines in the industry. It has been shown that the proposed indicators are useful and enable an accurate diagnosis of levels of eccentricity.
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Benadda, Mohamed, Ahmed Bouzidane, Marc Thomas, and Raynald Guilbault. "Dynamic behavior analysis of a rigid rotor supported by hydrostatic squeeze film dampers compensated with new electrorheological valve restrictors." Industrial Lubrication and Tribology 72, no. 5 (November 4, 2019): 611–19. http://dx.doi.org/10.1108/ilt-06-2019-0226.
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Purpose This paper aims to propose a new hydrostatic squeeze film damper compensated with electrorheological valve restrictors to control the nonlinear dynamic behavior of a rigid rotor caused by high unbalance eccentricity ratio. To investigate the effect of electrorheological valve restrictors on the dynamic behavior of a rigid rotor, a nonlinear model is developed and presented. Design/methodology/approach The nonlinear results are compared with those obtained from a linear approach. The results show good agreement between the linear and nonlinear methods when the unbalanced force is small. The effects of unbalance eccentricity ratio and electric field on the vibration response and the bearing transmitted force are investigated using the nonlinear models. Findings The results of simulation performed that the harmonics generated by high unbalance eccentricities can be reduced by using hydrostatic squeeze film damper compensated with electrorheological valve restrictors. Originality/value The numerical results demonstrate that this type of smart hydrostatic squeeze film damper provides to hydrostatic designers a new bearing configuration suitable to control rotor vibrations and bearing transmitted forces, especially for high speed.
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Si, Heyong, Lihua Cao, and Pan Li. "Dynamic Characteristics and Stability Prediction of Steam Turbine Rotor Based on Mesh Deformation." Strojniški vestnik – Journal of Mechanical Engineering 66, no. 3 (March 15, 2020): 164–74. http://dx.doi.org/10.5545/sv-jme.2019.6283.
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In order to study the steam flow excited vibration caused by the eccentricity of a rotor, three-dimensional rotor whirl motion is simulated based on mesh deformation. The mechanism of steam flow excited vibration and its influence on the dynamic characteristics of the rotor are investigated. The results show that the exciting forces change with the displacement of the rotor’s centre. Rotor dynamic coefficients are nonlinear when the rotor whirls pass the mesh deformation. The rotor dynamic coefficients and effective damping increase with the increase of whirl frequency. When the whirl frequency is 24.41 Hz, the rotor dynamic coefficients are strongly affected by rotational velocity. The maximum fluctuations of average direct stiffness, cross-coupling stiffness, direct damping and cross-coupling damping are 8.1 %, 113.2 %, 45.8 %, and 121.0 %, respectively. Effective damping fluctuates greatly when both whirl and rotational frequency are 24.41 Hz. The direct stiffness, direct damping, and effective damping increase with the increase of pressure ratio, which can improve rotor stability. The pressure fluctuation on the rotor’s surface is a primary reason for steam flow excited vibration. The stability margin of the rotor can be estimated precisely via effective damping.
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Lin, Junzhe, Yulai Zhao, Pengfei Wang, Yuanyuan Wang, Qingkai Han, and Hui Ma. "Nonlinear Responses of a Rotor-Bearing-Seal System with Pedestal Looseness." Shock and Vibration 2021 (September 1, 2021): 1–22. http://dx.doi.org/10.1155/2021/9937700.
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In this paper, a pedestal looseness fault model of a rotor-bearing-seal system is established. Under two working conditions of the same direction eccentricity (Working Condition 1) and reverse eccentricity (Working Condition 2), rotor orbits, vibration waveforms, spectrum cascade, and Poincaré maps are used to study the dynamic characteristics of the system when the sliding bearing support is loosened. The influence of speed, the unbalance of two discs, the looseness clearance, and the mass of bearing support on system characteristics are analyzed. The study found that Working Condition 2 is more likely to cause looseness of the bearing support. Moreover, for the rotor system in this paper, the pedestal looseness fault is more likely to occur near the second-order critical speed. Through analysis of the spectrum, it is found that the spectrum of the looseness fault will show multiple frequencies or continuous spectra, and the rotor orbits will appear “cylindrical.”
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Feng, Hui-Hui, Chun-Dong Xu, and Jie Wan. "Mathematical Model and Analysis of the Water-Lubricated Hydrostatic Journal Bearings considering the Translational and Tilting Motions." Mathematical Problems in Engineering 2014 (2014): 1–15. http://dx.doi.org/10.1155/2014/353769.
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The water-lubricated bearings have been paid attention for their advantages to reduce the power loss and temperature rise and increase load capacity at high speed. To fully study the complete dynamic coefficients of two water-lubricated, hydrostatic journal bearings used to support a rigid rotor, a four-degree-of-freedom model considering the translational and tilting motion is presented. The effects of tilting ratio, rotary speed, and eccentricity ratio on the static and dynamic performances of the bearings are investigated. The bulk turbulent Reynolds equation is adopted. The finite difference method and a linear perturbation method are used to calculate the zeroth- and first-order pressure fields to obtain the static and dynamic coefficients. The results suggest that when the tilting ratio is smaller than 0.4 or the eccentricity ratio is smaller than 0.1, the static and dynamic characteristics are relatively insensitive to the tilting and eccentricity ratios; however, for larger tilting or eccentricity ratios, the tilting and eccentric effects should be fully considered. Meanwhile, the rotary speed significantly affects the performance of the hydrostatic, water-lubricated bearings.
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Jin, Xin, and Yi Liu. "Numerical and Experimental Analysis for the Dynamics of Flawed–Machining Rod–Disk Rotor with Inner Misalignment." Machines 10, no. 5 (May 9, 2022): 355. http://dx.doi.org/10.3390/machines10050355.
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The nonlinear dynamic effects of the misalignment between inner disks in a flawed–machining rod–disk rotor is studied. Non–uniform stress distribution due to inner misalignment is obtained based on 3D static solution. The concomitant unbalances, including constant mass eccentricity and speed–variant rotor bending, are taken into account in the nonlinear dynamics. The dynamic results show that rotor bending leads to stability reduction and vibration growth. There is a distinctive feature in that the rotor’s vibration goes up again after critical speed. The maximum allowable inner misalignment is obtained according to its stability boundaries. An uneven tightening method is also presented to reduce adverse effects when the inner misalignment exists. Moreover, an experiment is designed to measure the vibration characteristics for the rod–disk rotor bearing system with inner misalignment. The results show that the theoretical result of vibration amplitude of the flawed rod–rotor bearing system is basically consistent with the experimental value. It is also found that the precise rotor performs the periodic motion, but the flawed rod–disk rotor exhibits the period–doubling orbit. This phenomenon proves that the flawed rod–disk rotor loses stability more easily than the precise rotor due to inner misalignment. However, the amplitude of harmonic frequency components for the precise rod–disk rotor system is obviously larger than the flawed rod–disk rotor system with inner misalignment. The peak value of the vibration amplitude increases when the inner misalignment becomes larger. On the whole, this work presents numerical and experimental analysis to study the dynamics of flawed-machining rod–disk rotor with inner misalignment. It also establishes the relationship between centration precision and dynamic features.
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Liu, Yi, Heng Liu, and BoWen Fan. "Nonlinear dynamic properties of disk-bolt rotor with interfacial cutting faults on assembly surfaces." Journal of Vibration and Control 24, no. 19 (August 10, 2017): 4369–82. http://dx.doi.org/10.1177/1077546317724602.
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Interfacial cutting faults on assembly surfaces are considered in a three-dimensional (3D) disk-bolt rotor system. The traditional finite element method is used to establish the 3D model of faulted disk-bolt rotor. A contact algorithm is applied to calculate the static features of this combined rotor. It is revealed that interfacial cutting faults produce rotor bending which is gradually strengthened as rotational speed increases besides disk’s mass eccentricity. The 3D dynamic equations of a faulted disk-bolt rotor system include these cutting faults’ static influences. The nonlinear dynamic properties are investigated by Poincaré mapping, Newton iteration and a prediction-correction algorithm. As a result, the rotor bending due to cutting faults reduces the global stability of the complicated rotor and enlarges the vibration amplitude obviously. This speed-variant bending also decides the feature that rotor vibration increases again after critical speed no matter whether dynamic balance is carried out. The maximum allowable fault depth is obtained and it gives an explanation as to why the machining precision of assembly surfaces should be strictly controlled in the disk-bolt rotor. Generally, this paper originally tries to provide a feasible approach to consider a 3D interfacial cutting fault with specific shape and to analyze the static–dynamic coupling characteristics for a disk-bolt rotor.
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Pan, Zhiwei, Yongxiang Jiang, Hongchao Xia, Min Ge, and Yiwen Ma. "Nonlinear Dynamic Numerical Analysis of Solid-liquid Separation Rolling Bearing-Rotor System Finite Element Discrete Modeling." Journal of Physics: Conference Series 2417, no. 1 (December 1, 2022): 012017. http://dx.doi.org/10.1088/1742-6596/2417/1/012017.
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Based on a rolling bearing-single disc rotor, centrifugal force is generated due to the influence of unbalanced factors such as rotor eccentric excitation, bearing restraint stiffness, and rotating stator clearance, which leads to the imbalance of the rotor system, resulting in the problem of friction between the rotor and the stator. This paper establishes a dynamic model of a single-disk rotor supported by rolling bearings, and the fourth-order Runge-Kutta numerical integration method is used to solve it. Bifurcation behavior and nonlinear dynamic response at a rotational speed. The results show that the nonlinear dynamic characteristics of the system are significantly different due to changes in elliptic eccentricity, rotational speed, and bearing constraint stiffness; when the rotational speed increases, the system gradually appears bifurcation, quasi-periodic motion, and instability increases. Therefore, reasonable selection of the working speed of the rotor and the gap between the stator and the rotor can reduce the non-periodic vibration caused by the unbalanced force and improve the stability of the system operation.
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Werner, Ulrich. "Theoretical rotor dynamic analysis of two-pole induction motors regarding excitation due to static rotor eccentricity." Archive of Applied Mechanics 81, no. 2 (February 4, 2010): 241–62. http://dx.doi.org/10.1007/s00419-010-0413-z.
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Šedivý, Dominik, Petr Ferfecki, and Simona Fialová. "Influence of Eccentricity and Angular Velocity on Force Effects on Rotor of Magnetorheological Damper." EPJ Web of Conferences 180 (2018): 02091. http://dx.doi.org/10.1051/epjconf/201818002091.
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This article presents the evaluation of force effects on squeeze film damper rotor. The rotor is placed eccentrically and its motion is translate-circular. The amplitude of rotor motion is smaller than its initial eccentricity. The force effects are calculated from pressure and viscous forces which were measured by using computational modeling. Damper was filled with magnetorheological fluid. Viscosity of this non-Newtonian fluid is given using Bingham rheology model. Yield stress is not constant and it is a function of magnetic induction which is described by many variables. The most important variables of magnetic induction are electric current and gap width between rotor and stator. The simulations were made in finite volume method based solver. The motion of the inner ring of squeeze film damper was carried out by dynamic mesh. Numerical solution was solved for five different initial eccentricities and angular velocities of rotor motion.
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Wu, Yucai, and Guanhua Ma. "Anti-Interference and Location Performance for Turn-to-Turn Short Circuit Detection in Turbo-Generator Rotor Windings." Energies 12, no. 7 (April 10, 2019): 1378. http://dx.doi.org/10.3390/en12071378.
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Online and location detection of rotor winding inter-turn short circuits are an important direction in the field of fault diagnosis in turbo-generators. This area is facing many difficulties and challenges. This study is based on the principles associated with the U-shaped detection coil method. Compared with dynamic eccentricity faults, the characteristics of the variations in the main magnetic field after a turn-to-turn short circuit in rotor windings were analyzed and the unique characteristics were extracted. We propose that the degree of a turn-to-turn short circuit can be judged by the difference in the induction voltage of the double U-shaped detection coils mounted on the stator core. Here, the faulty slot position was determined by the local convex point formed by the difference in the induced voltage. Numerical simulation was used here to determine the induced voltage characteristics in the double U-shaped coils caused by the turn-to-turn short circuit fault. We analyzed the dynamic eccentricity fault as well as combined the fault of a turn-to-turn short circuit and dynamic eccentricity. Finally, we demonstrate the positive anti-interference performance associated with this fault detection method. This new online detection method is satisfactory in terms of sensitivity, speed, and positioning, and overall performance is superior to the traditional online detection methods.
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Beloborodov, Sergey, Vladimir Modorskii, and Dmitriy Tsimberov. "ENSURING DYNAMIC STABILITY OF FREEZING ROTORS BY TECHNOLOGICAL METHODS." Perm National Research Polytechnic University Aerospace Engineering Bulletin, no. 70 (2022): 104–11. http://dx.doi.org/10.15593/2224-9982/2022.70.10.
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The proposed article is devoted to artificial material systems operating in conditions of information scarcity for effective management. The problem is considered on the example of rotors operating in conditions of icing of surfaces of turbine units used in aviation and the thermal power complex. The analysis of measures to ensure the dynamic stability of rotors, whose surfaces are subject to icing, leading to an uncontrolled increase in local imbalances, is carried out. The relevance of the problem is due to both the general trend of scientific and technological progress aimed at improving technologies and types of products, and modern challenges of the economy. These should primarily include meeting the need for technological processes and types of products that are as close as possible to the requests in terms of the resource of work, cost, cost of operation and disposal. At the same time, the situation at the production site is complicated by the hostile attitude of the so-called Western countries to the development of Russian industry, especially in aviation, the thermal power complex, defense, elec-tronics, etc. All this creates a complex scientific and technical contradiction, burdened by a shortage of material support: financial inse-curity and the absence of a number of components supplied by previously unfriendly countries. Based on the results of the analysis of the dynamic state of the systems, the direction of its technological support is determined. Two methods are proposed to ensure the dynamic stability of the most problematic elements of rotors: wheels of centrifugal and axial compressors (turbines). At the same time, the method of precision preparation of rotor elements for assembly is designed to ensure the installation of the element on the shaft with minimized eccentricity of the forming seal and without imbalance, and the method of eccentricity-virtual assembly of turbine wheels is designed to balance the rotor with a pre–known imbalance. The application of the developed methods makes it possible to solve the formulated scientific and technical contradiction, significantly improve the quality of prod-ucts, reduce the labor intensity and cost of production. Technological processes using these methods have been tested in industrial conditions.
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Werner, Ulrich. "Influence of electromagnetic field damping on forced vibrations of induction rotors caused by dynamic rotor eccentricity." ZAMM - Journal of Applied Mathematics and Mechanics / Zeitschrift für Angewandte Mathematik und Mechanik 97, no. 1 (June 16, 2016): 38–59. http://dx.doi.org/10.1002/zamm.201500285.
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Ha, K. H., and J. P. Hong. "Dynamic rotor eccentricity analysis by coupling electromagnetic and structural time stepping FEM." IEEE Transactions on Magnetics 37, no. 5 (2001): 3452–55. http://dx.doi.org/10.1109/20.952635.
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Zhang, Yimin, Qibin Wang, Hui Ma, Jing Huang, and Chunyu Zhao. "Dynamic analysis of three-dimensional helical geared rotor system with geometric eccentricity." Journal of Mechanical Science and Technology 27, no. 11 (November 2013): 3231–42. http://dx.doi.org/10.1007/s12206-013-0846-8.
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Khan, M. Z., and T. A. Stolarski. "Dynamic Performance of Oil-Lubricated Helical Groove Journal Bearings." Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology 208, no. 1 (March 1994): 65–73. http://dx.doi.org/10.1243/pime_proc_1994_208_350_02.
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The provision of helical grooves on the surface of a plain journal bearing can, in principle, improve the stability of a rotor-bearing system. The improvement, however, depends on the arrangement of the grooves along the axial length of the bearing. In order to verify this, three types of helical groove bearing with different groove arrangements and a reference plain journal bearing were studied. The bearings were studied in a specially designed test rig. A computer model was also developed to predict the performance of the bearings studied. The experimental and theoretical results produced during the course of the studies show that at the expense of a reduced load capacity the helical groove bearings are more stable, particularly at low eccentricity ratios. For a given eccentricity ratio and speed the symmetrical bearing operates at higher temperature and with greater power losses than the other three bearings tested. At the same eccentricity ratio and speed, the asymmetrical bearing runs at about the same temperature as the plain journal bearing.