Journal articles: 'Dynamics of rotor'

1

Bartlett, H., and R. Whalley. "Distributed rotor dynamics." Proceedings of the Institution of Mechanical Engineers, Part I: Journal of Systems and Control Engineering 212, no. 4 (June 1, 1998): 249–65. http://dx.doi.org/10.1243/0959651981539442.

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The modelling, simulation and analysis of powered rotors with ‘long’ thin shells is investigated. General results enabling the prediction of the torsional vibrational signature of high-speed assemblies under acceleration or braking conditions are outlined. It is demonstrated that simulated response characteristics can be easily obtained and the effect of varying the rotor geometry can be routinely accommodated. Finally, a rotor for a high-speed paper manufacturing unit is investigated and the torsional behaviour of the assembly is computed. The volatile transient conditions presented are commented upon.

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Zaytsev, Nikolay, Denis Zaytsev, Andrey Makarov, and Dmitriy Mineev. "NUMERICAL SIMULATION OF THE DYNAMICS OF A FLEXIBLE ROTOR WITH TWO BALL AUTO-BALANCERS." Perm National Research Polytechnic University Aerospace Engineering Bulletin, no. 62 (2020): 31–44. http://dx.doi.org/10.15593/2224-9982/2020.62.04.

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Ball auto-balancing devices can to compensate changes of unbalance "on the move" only for rotors operating at supercritical speeds. For automatic balancing of such rotors, classified as flexible rotors, several auto-balancers located in different cross sections of the shaft are necessary. This makes it necessary to account bending fluctuations on studies of dynamics of the rotor with auto-balancers, that is especially important in the design of the real rotors. In view of the complexity of experimental studies of such rotors in the article the method of direct numerical simulation of the dynamics of the flexible rotor system – supports – auto-balances is considered. The methodological basis of this method is the use of a discrete multi-mass rotor model, which is equivalent in dynamic characteristics to a real rotor, and also the equations of dynamics of the system discrete rotor – supports – auto-balancers, obtained in the direct form of recording. For definition of discrete masses and a matrix of coefficients of influence of stiffness of rotor cross-sections it is supposed to use calculations for finite-element model of a real rotor by existing software complexes of the engineering analysis. The mathematical model of the system dynamics obtained by the Lagrange method takes into account the non-stationarity of the rotor rotation speed, the influence of gravity and the rolling friction of the balls in the auto-balancer cages. Verification of the mathematical model was performed by reproducing the published data using a computational model for a two-support single-disk three-mass rotor with a two-ball auto-balancer. For a four-mass rotor with two two-ball auto-balancers, the results of numerical simulation of dynamics for the modes of acceleration, steady-state rotation and deceleration are presented. It is shown that for the system under consideration, only partial auto-balancing takes place in the steady rotation mode, including after a stepwise increase of the imbalance.

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Rao, J. S., and H. Saunders. "Rotor Dynamics." Journal of Vibration and Acoustics 107, no. 3 (July 1, 1985): 351–52. http://dx.doi.org/10.1115/1.3269268.

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4

Case, Robert O. "Rotor dynamics." Mechanism and Machine Theory 20, no. 1 (January 1985): 81–82. http://dx.doi.org/10.1016/0094-114x(85)90063-1.

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Tondl, A. "Rotor dynamics." Journal of Sound and Vibration 157, no. 3 (September 1992): 566–67. http://dx.doi.org/10.1016/0022-460x(92)90538-9.

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6

Fletcher, T. M., and R. E. Brown. "Modelling the interaction of helicopter main rotor and tail rotor wakes." Aeronautical Journal 111, no. 1124 (October 2007): 637–43. http://dx.doi.org/10.1017/s0001924000004814.

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Abstract The mutual interaction between the main rotor and tail rotor wakes is central to some of the most problematic dynamic phenomena experienced by helicopters. Yet achieving the ability to model the growth and propagation of helicopter rotor wakes with sufficient realism to capture the details of this interaction has been a significant challenge to rotorcraft aerodynamicists for many decades. A novel computational fluid dynamics code tailored specifically for rotorcraft applications, the vorticity transport model, has been used to simulate the interaction of the rotors of a helicopter with a single main rotor and tail rotor in both hover and low-speed quartering flight, and with the tail rotor rotating both top-forward and top-aft. The simulations indicate a significant level of unsteadiness in the performance of both main and tail rotors, especially in quartering flight, and a sensitivity to the direction of rotation of the tail rotor. Although the model thus captures behaviour that is similar to that observed in practice, the challenge still remains to integrate the information from high fidelity simulations such as these into routine calculations of the flight dynamics of helicopters.

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Sawicki, Jerzy T., Asok K. Sen, and Grzegorz Litak. "Multiresolution Wavelet Analysis of the Dynamics of a Cracked Rotor." International Journal of Rotating Machinery 2009 (2009): 1–8. http://dx.doi.org/10.1155/2009/265198.

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We examine the dynamics of a healthy rotor and a rotor with a transverse crack, which opens and closes due to its self weight. Using discrete wavelet transform, we perform a multiresolution analysis of the measured vibration signal from each of these rotors. In particular, the measured vibration signal is decomposed into eight frequency bands, and the rms amplitude values of the healthy and cracked rotors are compared in the three lowest-frequency bands. The results indicate that the rms vibration amplitudes for the cracked rotor are larger than those of the healthy rotor in each of these three frequency bands. In the case of externally applied harmonic force excitation to the rotor, the rms values of the vibration amplitude of the cracked rotor are also found to be larger than those of a healthy rotor in the three lowest-frequency bands. Furthermore, the difference in the rms values between the healthy and cracked rotors in each of the three lowest-frequency bands is more pronounced in the presence of external excitation than that with no excitation. The obtained results suggest that the present multiresolution approach can be used effectively to detect the presence of a crack in a rotor.

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Fan, Ye Sen, San Min Wang, and Zhen Yang. "Dynamic Characteristics of the Coupled System of the High Pressure Rotor and the Radial Driveshaft of a Turbofan Engine." Advanced Materials Research 44-46 (June 2008): 127–34. http://dx.doi.org/10.4028/www.scientific.net/amr.44-46.127.

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In a turbofan engine, the high pressure rotor and the radial driveshaft, which transmit the power from the internal gear-box to the external gear-box, are geared by a spiral bevel gear pair. In this paper, a reasonably simplified dynamic model of the coupled rotors system is established, and then, the coupled stiffness matrix and coupled damping matrix of the spiral bevel gear pair are deduced. A shaft element method is proposed to investigate the lateral-torsional coupled vibration equations of the gear-rotor system. Furthermore, the mode shapes and unbalance responses of this two rotors coupled system are simulated. The results indicate that the system derives many new modes and the exciting forces on a rotor of the system would be passed to the other rotor for the gears meshing. When the rotor dynamics of a turbofan engine is being analyzed, the high pressure rotor and the radial drive shaft must be viewed as a whole. The dynamic balance precision of the rotors should be qualified properly, in order to improve the dynamic quality of the turbofan engine.

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9

Park, J. S., and S. N. Jung. "Comprehensive multibody dynamics analysis for rotor aeromechanics predictions in descending flight." Aeronautical Journal 116, no. 1177 (March 2012): 229–49. http://dx.doi.org/10.1017/s0001924000006813.

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AbstractThis paper studies the rotor aeromechanics in descending flight using a nonlinear flexible multibody dynamic analysis code, DYMORE. A freewake model is included in DYMORE to improve the rotor wake modelling. The wind-tunnel test data of the Higher-harmonic Aeroacoustics Rotor Test (HART) II rotor, with and without higher harmonic pitch control (HHC), and the flight test data of the full-scale utility helicopter rotor in descent are used for the aeromechanics correlation at an advance ratio of 0·15. The blade-vortex interaction (BVI) airloads are reasonably predicted for both the HART II and utility helicopter rotors, although some BVI peaks are missed on the advancing sides for both the rotors. The flap deflections and elastic torsion deformations at the blade tip are fairly correlated against the measured data of the HART II rotor. The correlation of blade structural moments for both HART II and utility helicopter rotors are not as good as the lift predictions; however, a reasonable prediction is obtained for the utility helicopter rotor.

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Barzdaitis, Vytautas, Vytautas Žemaitis, R. Jonušas, Vytautas Kazimieras Augustaitis, and Vytautas Bučinskas. "Dynamics of a Mechatronic System with Flexible Vertical Rotor." Solid State Phenomena 113 (June 2006): 223–28. http://dx.doi.org/10.4028/www.scientific.net/ssp.113.223.

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The paper is dedicated to research on flexible rotor systems with anisotropic rotor material properties. In addition, the anisotropy of rotor supports alters the rotor system resonance frequencies and the machine has to pass till it attains the operating angular speed. This phenomenon of rotor vibration is observed in vertical rotors. The aim of this work is to compare experimental vibration measurements and results of theoretical modeling. In the paper theoretical model, created from physical one of really existing rotor system is described. Collected experimental data of rotor vibrations in bearings are compared with results of theoretically derived equations. The results of theoretical modeling and research enables for estimation of a more precise technical condition of the rotor system both after the overhaul and during the maintenance and thus to avoid unexpected breakdowns, especially concerning the fatigue development in ball bearing elements.

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11

Liu, Yi, and Heng Liu. "Dynamic behaviors of three-dimensional rod-disk rotor rolling bearing system." Proceedings of the Institution of Mechanical Engineers, Part K: Journal of Multi-body Dynamics 232, no. 1 (April 20, 2017): 21–31. http://dx.doi.org/10.1177/1464419317705987.

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A typical rod-disk rotor is meshed by three-dimensional solid elements. The stability features, whirling motions and frequency spectrums of 3D rod-disk rotor rolling bearing system are investigated by combining nonlinear analysis method and finite element method. Meanwhile, an identical 1D rod-disk rotor system is introduced for comparison. With the support of the ball bearing, the stability region of 1D and 3D rod-disk rotors shows good consistency at lower speed and has obvious differences at higher speed. However, 3D rotor has smaller bending deformation because 3D solid elements can restrict large deflection but the equivalent springs in 1D model do not have this function. When cylindrical roller bearings are applied, both rotors also have the same frequency spectrums which consist of rotating frequency, variable compliance frequency and their linear combinations. Moreover, 3D rotor dynamics have the advantage of analyzing dynamic stress. In short, this paper proposes a numerical way to investigate the dynamic behaviors of 3D rod-disk rotor rolling bearing system.

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Pacholczyk, Michał, and Dariusz Karkosiński. "Parametric Study on a Performance of a Small Counter-Rotating Wind Turbine." Energies 13, no. 15 (July 29, 2020): 3880. http://dx.doi.org/10.3390/en13153880.

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A small Counter-Rotating Wind Turbine (CRWT) has been proposed and its performance has been investigated numerically. Results of a parametric study have been presented in this paper. As parameters, the axial distance between rotors and a tip speed ratio of each rotor have been selected. Performance parameters have been compared with reference to a Single Rotor Wind Turbine (SRWT). Simulations were carried out with Computational Fluids Dynamics (CFD) solver and a Large Eddy Scale approach to model turbulences. An Actuator Line Model has been chosen to represent rotors in the computational domain. Summing up the results of simulation tests, it can be stated that when constructing a CRWT turbine, rotors should be placed at a distance of at least 0.5 D (where D is rotor outer diameter) or more. One can then expect a noticeable power increase compared to a single rotor turbine. Placing the second rotor closer than 0.5 D guarantees a significant increase in power, but in such configurations, dynamic interactions between the rotors are visible, resulting in fluctuations in torque and power. Dynamic interactions between rotor blades above 0.5 D are invisible.

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13

Gislén, Lars, Carsten Peterson, and Bo Söderberg. "Rotor Neurons: Basic Formalism and Dynamics." Neural Computation 4, no. 5 (September 1992): 737–45. http://dx.doi.org/10.1162/neco.1992.4.5.737.

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Rotor neurons are introduced to encode states living on the surface of a sphere in D dimensions. Such rotors can be regarded as continuous generalizations of binary (Ising) neurons. The corresponding mean field equations are derived, and phase transition properties based on linearized dynamics are given. The power of this approach is illustrated with an optimization problem—placing N identical charges on a sphere such that the overall repulsive energy is minimized. The rotor approach appears superior to other methods for this problem both with respect to solution quality and computational effort needed.

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14

Belykh, V. N., and N. N. Verichev. "Coupled rotor dynamics." Radiophysics and Quantum Electronics 31, no. 6 (June 1988): 503–12. http://dx.doi.org/10.1007/bf01044654.

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15

Muszynska, Agnes, Charles T. Hatch, and Donald E. Bently. "Dynamics of Anisotropically Supported Rotors." International Journal of Rotating Machinery 3, no. 2 (1997): 133–42. http://dx.doi.org/10.1155/s1023621x97000134.

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The paper discusses dynamic effects occurring in machinery rotors supported in bearings and pedestals with laterally different characteristics. In the considered rotor model the anisotropy of radial stiffness and tangential (“cross”) stiffness components are included. Within certain ranges of the rotative speed the support anisotropy leads to the specific, excited-by-unbalance rotor lateral synchronous vibrations in a form of backward (reverse) precession. In addition, one section of the rotor may precess backward, while the other section simultaneously precesses forward. Experimental results illustrate this phenomenon. The analytical model of the system is based on multimode modal approach. It is also shown in this paper that greatly enhanced information for machine malfunction diagnostics can be obtained by simulated rotation of the XY transducer system observing rotor lateral vibration. This simulated rotation can be accomplished by the machine diagnostic data acquistion and processing system. The data processing also includes extraction of forward and backward components of elliptical orbits filtered to one frequency, and the filtered orbit major axis magnitude and its angular orientation.Numerical examples, field data, and experimental results performed on a rotor rig illustrate applications.

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16

Sawicki, Jerzy T., Joe Padovan, and Rabih Al-Khatib. "The Dynamics of Rotor with Rubbing." International Journal of Rotating Machinery 5, no. 4 (1999): 295–304. http://dx.doi.org/10.1155/s1023621x99000263.

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This paper presents the description of some phenomena associated with dynamic behavior of rotors interacting with stationary components. Numerical simulations show rotor vibration spectrum rich in subharmonic, quasi-periodic, and chaotic vibrations. The nonlinear calculation techniques are applied to demonstrate the changes of the vibration patterns for different operating conditions. Some conclusions are discussed with regard to unique characteristics of rub-induced rotor response, initial conditions, as well as appropriate ranges of system parameters. Of special interest are the changes in the apparent nonlinearity of the system dynamics as rubs are induced at different rotor speeds. In particular, starting with 2nd order sub/superharmonics, which are symptomatic of quadratic nonlinearity, progressively higher order polynomial behavior is excited, i.e., cubic, giving rise to 3rd order sub/superharmonics. As the speed is transitioned between such apparent nonlinearities, chaotic like behavior is induced because of the lack of whole or rational tone tuning between the apparent system frequency and the external source noise. The cause of such behavior will be discussed in detail along with the results of several parametric studies.

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17

Li, M. "Non-linear dynamic behaviour of rotor—bearing system trained by bevel gears." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 222, no. 4 (April 1, 2008): 617–27. http://dx.doi.org/10.1243/09544062jmes843.

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The vibrations of parallel geared rotor—bearing system have been intensively discussed; however, little attention has been paid to the dynamic analysis of angled bevel-geared system supported on journals. In the present work, the non-linear dynamics of a bevel-geared rotor system on oil film bearings is studied. First, the dynamic model is developed under some assumptions, such as rigid rotors, short-bearings, small teeth errors, and so forth. Then, the non-linear dynamic behaviours of both the balanced and unbalanced rotor system are analysed, respectively, in which the equilibrium points, limit cycles, their stability, and bifurcations are paid more attention. Numerical results show that in the bevel-geared rotor system under the action of non-linear oil film forces there exists a series of complex non-linear dynamic phenomena of rotor orbits, such as Hopf bifurcation, torus-doubling bifurcation, and jump phenomenon. All these features can help us to understand the dynamic characteristics of bevel-geared rotor—bearing system at design stage and during running period. Finally, some concerned problems during the investigation are also present.

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18

Liu, Bao Guo, Hai Feng Hua, Long Wang Yue, and Xiao Ding Xu. "Design of the Post-Processor for Rotors Dynamics Based on the STEP Standard." Advanced Materials Research 706-708 (June 2013): 1871–76. http://dx.doi.org/10.4028/www.scientific.net/amr.706-708.1871.

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The STEP standard is an international standard for data expressing and exchanging during the whole life cycle of the product, the neutral file is an universal data exchange form for the data exchanging. In order to develop a STEP post-processer for the rotor dynamics analysis software-Rotors Dynamics, the author elaborates the lexical analysis module and data mapping module, studies the rotor model parameter extraction based on STEP neutral file, and realizes the seamless connectivity between the Rotors Dynamics and the rotor’s CAD model.

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Li, Guang Xi, Yin Shan Zhang, Lin He, and Li Yang. "Rotor Dynamics Analysis of the Flywheel Energy Storage System." Applied Mechanics and Materials 312 (February 2013): 3–10. http://dx.doi.org/10.4028/www.scientific.net/amm.312.3.

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In this paper, a dynamics model of flywheel rotor - support system is build. Obtained the dynamic characteristics of the flywheel rotor by finite element method .The results indicate that the rotor system is stability and security. This provides the basis for the subsequent optimization of flywheel rotor.

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Singh, Puneet, and Peretz P. Friedmann. "Dynamic Stall Modeling Using Viscous Vortex Particle Method for Coaxial Rotors." Journal of the American Helicopter Society 66, no. 1 (January 1, 2021): 1–16. http://dx.doi.org/10.4050/jahs.66.012010.

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Dynamic stall is an important source of vibrations on a rotor at high advance ratios. The periodic flow separation and reattachment during dynamic stall generates large unsteady loads. In this study, the flow separation is modeled as the shedding of concentrated vorticity from the leading edge of the airfoil. The viscous vortex particle method is used to calculate the evolution of the rotor wake. Blade loads are calculated using a reduced order model obtained from computational fluid dynamics, and dynamic stall loads are calculated using the ONERA dynamic stall model. Results are presented for single main rotor and coaxial rotors at advance ratios of μ = 0.3–0.4. The separated wake modifies the angle of attack distribution on the rotor and hence impacts the hub loads. The results indicate that the separated wake modifies the vibratory hub loads by 5–10% for a single main rotor at μ = 0.3. The vibratory hub loads for the coaxial rotor are modified by 10–20% at μ = 0.4 with the inclusion of the separated wake. The upper and lower rotor tip path planes are tilted such that the blade and wake interaction is greater on the retreating side of the upper rotor and decreased on the advancing side.

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Asdaque, P. M. G. Bashir, and R. K. Behera. "Vibration Analysis of Hollow Tapered Shaft Rotor." Advances in Acoustics and Vibration 2014 (April 28, 2014): 1–14. http://dx.doi.org/10.1155/2014/410851.

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Shafts or circular cross-section beams are important parts of rotating systems and their geometries play important role in rotor dynamics. Hollow tapered shaft rotors with uniform thickness and uniform bore are considered. Critical speeds or whirling frequency conditions are computed using transfer matrix method and then the results were compared using finite element method. For particular shaft lengths and rotating speeds, response of the hollow tapered shaft-rotor system is determined for the establishment of dynamic characteristics. Nonrotating conditions are also considered and results obtained are plotted.

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Keogh, P. S., and M. O. T. Cole. "Rotor vibration with auxiliary bearing contact in magnetic bearing systems Part 1: Synchronous dynamics." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 217, no. 4 (April 1, 2003): 377–92. http://dx.doi.org/10.1243/095440603321509676.

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Magnetic bearing systems incorporate auxiliary bearings to prevent physical interaction between rotor and stator laminations. Rotor/auxiliary bearing contacts may occur when a magnetic bearing still retains a full control capability. To actively return the rotor to a non-contacting state it is essential to determine the manner in which contact events affect the rotor vibration signals used for position control. An analytical procedure is used to assess the nature of rotor contact modes under idealized contacts. Non-linearities arising from contact and magnetic bearing forces are then included in simulation studies involving rigid and flexible rotors to predict rotor response and evaluate rotor synchronous vibration components. An experimental flexible rotor/magnetic bearing facility is also used to validate the predictions. It is shown that changes in synchronous vibration amplitude and phase induced by contact events causes existing controllers to be ineffective in attenuating rotor displacements. These findings are used in Part 2 of the paper as a foundation for the design of new controllers that are able to recover rotor position control under a range of contact cases.

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Xiang, Ling, Zi Rui Wang, and Gui Ji Tang. "Bifurcation Characteristics of Unbalanced Rotor - Bearing System." Advanced Materials Research 490-495 (March 2012): 2037–41. http://dx.doi.org/10.4028/www.scientific.net/amr.490-495.2037.

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Dynamic model of nonlinear rotor—bearing system is set up using the modified Capone bearing forces models. And the nonlinear dynamics behavior of unbalanced rotor—bearing systems was studied. The system state trajectories, Poincare maps, are also constructed to analyze the typical dynamic behavior of the system．Through the nonlinear dynamic numerical simulation of the system，the dynamic phenomena of the rotor—bearing system caused by oil film forces are clearly distinct. The computational results show that the rotor speed is one of the most important factors of the system dynamic behavior. It presents a periodic, period-doubling motion, quasi-periodic motion, and abundant nonlinear dynamical behavior with the changes of the speed.

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Vázquez, J. A., and L. E. Barrett. "Modeling of Tilting-Pad Journal Bearings with Transfer Functions." International Journal of Rotating Machinery 7, no. 1 (2001): 1–10. http://dx.doi.org/10.1155/s1023621x0100001x.

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Tilting-pad journal bearings are widely used to promote stability in modern rotating machinery. However, the dynamics associated with pad motion alters this stabilizing capacity depending on the operating speed of the machine and the bearing geometric parameters, particularly the bearing preload. In modeling the dynamics of the entire rotor-bearing system, the rotor is augmented with a model of the bearings. This model may explicitly include the pad degrees of freedom or may implicitly include them by using dynamic matrix reduction methods. The dynamic reduction models may be represented as a set of polynomials in the eigenvalues of the system used to determine stability. All tilting-pad bearings can then be represented by a fixed size matrix with polynomial elements interacting with the rotor. This paper presents a procedure to calculate the coefficients of polynomials for implicit bearing models. The order of the polynomials changes to reflect the number of pads in the bearings. This results in a very compact and computationally efficient method for fully including the dynamics of tilting-pad bearings or other multiple degrees of freedom components that interact with rotors. The fixed size of the dynamic reduction matrices permits the method to be easily incorporated into rotor dynamic stability codes. A recursive algorithm is developed and presented for calculating the coefficients of the polynomials. The method is applied to stability calculations for a model of a typical industrial compressor.

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Smalley, Anthony J. "Jørgen Lund: A Perspective on His Contributions to Modern Rotor Bearing Dynamics." Journal of Vibration and Acoustics 125, no. 4 (October 1, 2003): 434–40. http://dx.doi.org/10.1115/1.1605765.

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This paper presents a perspective on the work of Dr. J. W. Lund, in the field of rotor-bearing dynamics. It traces his most influential work in published journals, software, data published in various manuals, government reports, and course notes. It addresses his work in oil bearings, gas bearings, unbalance response of flexible rotors, stability of flexible rotors, squeeze-film dampers, rotor balancing, and modal testing of rotors. It provides a road map for those who would revisit the knowledge base. It shows how Dr. Lund’s work has permeated the practice of today’s suppliers and users of turbomachinery, and industry consultants.

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Srinivasarao, Gopisetti, Arun K. Samantaray, and Sanjoy K. Ghoshal. "Bond graph modeling and multi-body dynamics of a twin rotor system." Proceedings of the Institution of Mechanical Engineers, Part I: Journal of Systems and Control Engineering 235, no. 1 (February 12, 2020): 117–44. http://dx.doi.org/10.1177/0959651819899267.

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The dynamics of a twin-rotor multi-input multi-output system, which is similar to that of a helicopter in many ways, is highly nonlinear in nature. In this article, a detailed dynamical model of twin-rotor multi-input multi-output system is developed and simulated by using bond graph approach. Nonlinear nature of the interface gain, thrust, and drag forces, and the stiffness of cable attached to support column joint are estimated. The rotors are modeled through the Newton–Euler equations. The bond graph model is created by using the generic sub-models and the same set of sub-models can be assembled differently to model many other similar systems such as tricopters and quadcopters. Inertial forces and moments, rotor thrust and drag forces, active and reactive motor torques, and direct current motor dynamics are considered in the model. The responses from the model are compared with the test data for validation.

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Gorbenko, A. N., S. Kh Shmelev, and G. Strautmanis. "The Effect of Unbalance Mass on the Necessary Conditions of the Double-Support Rotor Autobalancing Stability." Herald of the Bauman Moscow State Technical University. Series Mechanical Engineering, no. 2 (125) (April 2019): 71–82. http://dx.doi.org/10.18698/0236-3941-2019-2-71-82.

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The analysis of necessary conditions for autobalancing stability of rotor, which performs spatial oscillations, was carried out in this paper taking into account the influence of unbalance and autobalancer masses. It was found that the using of traditional models, where unbalance and autobalancer masses are assumed small, could lead to significant errors in the dynamics analysis of spatially moving rotor. The influence of this factor leads to the doubling of the critical rotational speeds spectrum. Moreover, the system motion between the split critical frequencies is unstable. There may be one or two onset areas of autobalancing mode motion depending on the dynamic rotor type, its location relative to the supports, the unbalance mass and other system parameters. It was found that rotors, that are long type or close to the spherical type, are the most sensitive to this factor. On the other hand, rotors of the short type are weakly sensitive. It is shown that the most preferred case is when the unbalance and autobalancer location plane passes through the common mass center of the composite rotor. The quantitative criterion is formulated for the necessity of taking into account (or not taking into account) the influence of this factor when analyzing the system dynamics

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Barkat, Ibtissem, Abdelouahab Benretem, Fawaz Massouh, Issam Meghlaoui, and Ahlem Chebel. "Modeling and simulation of forces applied to the horizontal axis wind turbine rotors by the vortex method coupled with the method of the blade element." International Journal of Power Electronics and Drive Systems (IJPEDS) 12, no. 1 (March 1, 2021): 413. http://dx.doi.org/10.11591/ijpeds.v12.i1.pp413-420.

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This article aims to study the forces applied to the rotors of horizontal axis wind turbines. The aerodynamics of a turbine are controlled by the flow around the rotor, or estimate of air charges on the rotor blades under various operating conditions and their relation to the structural dynamics of the rotor are critical for design. One of the major challenges in wind turbine aerodynamics is to predict the forces on the blade as various methods, including blade element moment theory (BEM), the approach that is naturally adapted to the simulation of the aerodynamics of wind turbines and the dynamic and models (CFD) that describes with fidelity the flow around the rotor. In our article we proposed a modeling method and a simulation of the forces applied to the horizontal axis wind rotors turbines using the application of the blade elements method to model the rotor and the vortex method of free wake modeling in order to develop a rotor model, which can be used to study wind farms. This model is intended to speed up the calculation, guaranteeing a good representation of the aerodynamic loads exerted by the wind.

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Lu, Ke, Chunsheng Liu, Chunhua Li, and Renliang Chen. "Flight Dynamics Modeling and Dynamic Stability Analysis of Tilt-Rotor Aircraft." International Journal of Aerospace Engineering 2019 (August 14, 2019): 1–15. http://dx.doi.org/10.1155/2019/5737212.

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The tilt-rotor aircraft has often been proposed as a means to increase the maximum speed of the conventional helicopter. The tilt-rotor aircraft consists of three primary flight modes that are the helicopter flight mode in low forward speed flight, airplane flight mode in high forward speed flight, and conversion flight mode. The aim of this paper is to develop a nonlinear flight dynamics mathematical modeling method of tilt-rotor aircraft and investigate the dynamic stability characteristics of tilt-rotor aircraft. First, a nonlinear tilt-rotor aircraft flight dynamics model is developed. The trim and linearized results are present to verify the model. Then, using a numerical differentiation technique, the dynamic stability of the tilt-rotor aircraft is assessed. The results show that the flight speed and nacelle angle would affect the magnitude and the trend of the aerodynamic derivatives. The damping of the pitch short period mode and the Dutch roll mode is insensitive to flight speed while they could be affected by nacelle angle. In all flight modes, as flight speed increases, the natural modes become more stable.

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Choy, F. K., J. Padovan, and Y. F. Ruan. "Coupling of Rotor-Gear-Casing Vibrations During Extreme Operating Events." Journal of Pressure Vessel Technology 114, no. 4 (November 1, 1992): 464–71. http://dx.doi.org/10.1115/1.2929256.

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During extreme operating environments (i.e., seismic events, base motion-induced vibrations, etc.), the coupled vibrations developed between the rotors, bearings, gears and enclosing structure of gear-driven rotating equipment can be quite substantial. Generally, such large vibrational amplitudes may lead to failures in both the rotor-gearing system and/or the casing structure. This paper simulates the dynamic behavior of rotor-bearing-gear system resulting from motion of the enclosed structure. The modal synthesis approach is used in this study to synthesize the dynamics of the rotor systems with the vibrations of their casing structure in modal coordinates. Modal characteristics of the rotor-bearing-gear systems are evaluated using the matrix transfer technique, while the modal parameters for the casing structure are developed through a finite element model using NASTRAN. The modal accelerations calculated are integrated through a numerical algorithm to generate modal transient vibration analysis. Vibration results are examined in both time and frequency domains to develop representations for the coupled dynamics generated during extreme operating conditions. Typical three-rotor bull gear-driven power plant equipment (compressors, pumps, etc.) is used as an example to demonstrate the procedure developed.

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Dai, Yuting, Linpeng Wang, Chao Yang, and Xintan Zhang. "Dynamic Gust Load Analysis for Rotors." Shock and Vibration 2016 (2016): 1–12. http://dx.doi.org/10.1155/2016/5727028.

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Dynamic load of helicopter rotors due to gust directly affects the structural stress and flight performance for helicopters. Based on a large deflection beam theory, an aeroelastic model for isolated helicopter rotors in the time domain is constructed. The dynamic response and structural load for a rotor under the impulse gust and slope-shape gust are calculated, respectively. First, a nonlinear Euler beam model with 36 degrees-of-freedoms per element is applied to depict the structural dynamics for an isolated rotor. The generalized dynamic wake model and Leishman-Beddoes dynamic stall model are applied to calculate the nonlinear unsteady aerodynamic forces on rotors. Then, we transformed the differential aeroelastic governing equation to an algebraic one. Hence, the widely used Newton-Raphson iteration algorithm is employed to simulate the dynamic gust load. An isolated helicopter rotor with four blades is studied to validate the structural model and the aeroelastic model. The modal frequencies based on the Euler beam model agree well with published ones by CAMRAD. The flap deflection due to impulse gust with the speed of 2m/s increases twice to the one without gust. In this numerical example, results indicate that the bending moment at the blade root is alleviated due to elastic effect.

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Keogh, P. S., and M. O. T. Cole. "Contact Dynamic Response With Misalignment in a Flexible Rotor/Magnetic Bearing System." Journal of Engineering for Gas Turbines and Power 128, no. 2 (March 1, 2004): 362–69. http://dx.doi.org/10.1115/1.2056530.

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This paper investigates the vibration characteristics of rotor displacement signals in a magnetic bearing system under conditions when rotor contact with auxiliary bearings is possible. Since these signals may be used for feedback control, it is necessary to determine how they may affect the ability of the controller to regain rotor levitation. An experimental system is used to demonstrate the sensitivity of the rotor nonlinear dynamic behavior to unbalance, which is sufficient to cause contact during rotor run-up through rigid-body and flexural mode critical speeds. Complex rotor dynamics may involve contact with more than one auxiliary bearing or bush. Application of appropriate rotating forces to the rotor through a magnetic bearing is also shown to induce similar contact dynamics. Thus, an alternative procedure for assessing the nonlinear rotor dynamic behavior is established with the potential for identification of appropriate control forces. The contact dynamics are also considered in the presence of auxiliary bearing misalignment. Misalignment may arise through physical translation of a housing or through steady-state offset errors in sensor measurements. A misalignment of 50% of the nominal radial clearance is applied at an auxiliary bearing. Various contact modes are evident as the rotor is run up in speed. During rundown, different contact dynamics may be encountered and the level of such hysteresis is assessed.

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Ahmad, Sagheer. "Rotor Casing Contact Phenomenon in Rotor Dynamics — Literature Survey." Journal of Vibration and Control 16, no. 9 (June 23, 2010): 1369–77. http://dx.doi.org/10.1177/1077546309341605.

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Knotek, Jiří, Pavel Novotný, Ondřej Maršálek, Peter Raffai, and Jozef Dlugoš. "The Influence of Rotor Unbalance on Turbocharger Rotor Dynamics." Journal of Middle European Construction and Design of Cars 13, no. 3 (December 1, 2015): 8–13. http://dx.doi.org/10.1515/mecdc-2015-0010.

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Shrnutí Članek analyzuje vliv nevyvahy na dynamiku rotoru turbodmychadla. Je zde prezentovan 3D vypočtovy model rotoru turbodmychadla a hydrodynamicky model kluzne ložiska. Sestaveni vysledneho vypočtoveho modelu na urovni virtualniho prototypu je provedeno v prostředi software pro řešeni dynamiky těles. Članek prezentuje vybrane vysledky, na kterych je podrobně rozebran vliv velikosti nevyvahy na dynamiku rotoru turbodmychadla.

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35

Jin, Yu, Liu Yong, and Yang Weidong. "Dynamics research on actively controlled swashplateless rotor." Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering 233, no. 12 (January 13, 2019): 4492–508. http://dx.doi.org/10.1177/0954410018824474.

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This study presents the design, dynamic model, and dynamics research of a new cyclic pitch control strategy in motor-driven rotorcraft. In this strategy, the control response and flapping feature of conventional rotor systems can be obtained by imposing (1) a lag-pitch coupling on rotor blade and (2) an additional sinusoidal rotational speed of rotor shaft without any actuators or swashplate. This study establishes a refined nonlinear dynamic model including the effects of pitch motion, and figures out the fundamental dynamic characteristics of this novel configuration. Analyses of its mechanical stability, dynamic responses and stability in hover are also conducted. The model in this research, compared with the previous linear model, improves the predicting accuracies of dynamic responses remarkably. A preliminary understanding of this novel rotor's dynamic mechanisms is gained by this study.

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Ma, Hui, Zhao Hui Ren, Ji Shuang Dai, and Bang Chun Wen. "Research on Dynamics of Rotor Systems in Large Centrifugal Compressor." Key Engineering Materials 419-420 (October 2009): 121–24. http://dx.doi.org/10.4028/www.scientific.net/kem.419-420.121.

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It is important to study system vibration characteristics for improving product quality and ensuring safety operation of units. In this paper, some dynamics of rotor systems are studied in large centrifugal compressor. The models of diaphragm coupling and tilting pad bearing are established by appropriate simplification. The finite element model of rotors with bearing and coupling is set up by taking interrelation of these subsystems into account. The unbalance responses of journal are computed based on the relative standard. The effect of bearing parameters (length-diameter ratio, clearance ratio and lubricating oil number) to journal vibration of rotor systems is analyzed. Finally test results and theoretical results are compared and errors are analyzed. The research results will provide theoretical basis for improving the bearing design of compressor rotor systems.

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Basumatary, Kamal Kumar, Gaurav Kumar, Karuna Kalita, and Sashindra K. Kakoty. "Stability analysis of rigid rotors supported by gas foil bearings coupled with electromagnetic actuators." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 234, no. 2 (September 25, 2019): 427–43. http://dx.doi.org/10.1177/0954406219877903.

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Rotors supported on gas foil bearings have low damping characteristics, which limits its application. A possible solution could be an integration of a gas foil bearing with an electromagnetic actuator. This paper discusses the effect of electromagnetic actuators on the stability of a rotor supported on gas foil bearings. A coupled dynamic model combining the dynamics of gas foil bearing and electromagnetic actuator has been developed. The fluid film forces from the gas foil bearings and the electromagnetic forces from the electromagnetic actuators are integrated into the equations of motion of the rotor. The sub-synchronous vibration present in case of conventional gas foil bearings is reduced and the stability band of the rotor is increased due to the implementation of electromagnetic actuator.

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Lee, Chong-Won, Jong-Po Park, and Kwang-Joon Kim. "Complex Time Series Modeling and Analysis for Rotor Dynamics Identification." Journal of Vibration and Acoustics 119, no. 4 (October 1, 1997): 512–22. http://dx.doi.org/10.1115/1.2889753.

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A new time series method, directional ARMAX (dARMAX) model-based approach, is proposed for rotor dynamics identification. The dARMAX processes complex-valued signals, utilizing the complex modal testing theory which enables the separation of the backward and forward modes in the two-sided frequency domain and makes effective modal parameter identification possible, to account for the dynamic characteristics inherent in rotating machinery. The dARMAX is superior in nature to the conventional ARMAX particularly in the estimation of the modal parameters for isotropic and weakly anisotropic rotors. Numerical simulations are performed to demonstrate effectiveness of the dARMAX.

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Schlotter, Michael, and Patrick S. Keogh. "Synchronous Position Recovery Control for Flexible Rotors in Contact with Auxiliary Bearings." Journal of Vibration and Acoustics 129, no. 5 (February 2, 2007): 550–58. http://dx.doi.org/10.1115/1.2731414.

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This paper details a methology for the active recovery of contact free levitation of a rotor from a state of persistent contact with auxiliary bearings. An analytical method to describe contact dynamics of flexible rotors is presented. It shows that synchronous unbalance forces can cause a rotor to adopt stable contact modes, which are characterized by periodic motion and a fixed contact point in a rotating frame of reference. Based on these observations, a recovery strategy is developed to return the rotor to a contact free state. Compensation forces may be applied by magnetic bearings to reduce the effective synchronous forcing which is driving the contact, so that the rotor can progress to a contact free orbit. It is shown that even in the presence of highly nonlinear contact dynamic effects, a linear finite element rotor model can be used to calculate appropriate influence coefficients. The contact recovery procedure is successfully verified by simulations and measurements on a flexible rotor test facility. Allowable bounds on the phase of the synchronous recovery forces are investigated and limitations of the method are discussed.

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Doyle, James D., and Dale R. Durran. "Rotor and Subrotor Dynamics in the Lee of Three-Dimensional Terrain." Journal of the Atmospheric Sciences 64, no. 12 (December 1, 2007): 4202–21. http://dx.doi.org/10.1175/2007jas2352.1.

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Abstract The internal structure and dynamics of rotors that form in the lee of topographic ridges are explored using a series of high-resolution eddy-resolving numerical simulations. Surface friction generates a sheet of horizontal vorticity along the lee slope that is lifted aloft by the mountain lee wave at the boundary layer separation point. Parallel-shear instability breaks this vortex sheet into small intense vortices or subrotors. The strength and evolution of the subrotors and the internal structure of the main large-scale rotor are substantially different in 2D and 3D simulations. In 2D, the subrotors are less intense and are ultimately entrained into the larger-scale rotor circulation, where they dissipate and contribute their vorticity toward the maintenance of the main rotor. In 3D, even for flow over a uniform infinitely long barrier, the subrotors are more intense, and primarily are simply swept downstream past the main rotor along the interface between that rotor and the surrounding lee wave. The average vorticity within the interior of the main rotor is much weaker and the flow is more chaotic. When an isolated peak is added to a 3D ridge, systematic along-ridge velocity perturbations create regions of preferential vortex stretching at the leading edge of the rotor. Subrotors passing through such regions are intensified by stretching and may develop values of the ridge-parallel vorticity component well in excess of those in the parent, shear-generated vortex sheet. Because of their intensity, such subrotor circulations likely pose the greatest hazard to aviation.

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de Carvalho Michalski, Miguel Angelo, Moysés Zindeluk, and Renato de Oliveira Rocha. "Influence of Journal Bearing Axial Grooves on the Dynamic Behavior of Horizontal Rotors." Shock and Vibration 13, no. 4-5 (2006): 285–300. http://dx.doi.org/10.1155/2006/785823.

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Journal bearing design and the lubricant characteristics are very influential in a rotating machine behaviour. The bearing geometry can drastically affect the lubricant flow and also the rotor dynamics. Approaching that issue, this paper presents an experimental study of the dynamic behavior of a horizontal rotor suported by journal bearings with semi-circular axial grooves. The journal bearings were manufactured with a varied number of axial grooves and a versatile test rig is used, making possible the analysis of different configurations. The acquired signals are analyzed with classical and non-linear tools and the differences among the rotors’ configurations can be shown.

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42

Ma, Hui, Ji Shuang Dai, Xue Jun Wang, and Bang Chun Wen. "Dynamics Analysis of Rotor Systems in Large Centrifugal Compressor." Applied Mechanics and Materials 16-19 (October 2009): 115–19. http://dx.doi.org/10.4028/www.scientific.net/amm.16-19.115.

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It is important to study system vibration characteristics for improving product quality and insuring safety operation of machine. In this paper, dynamics of rotor systems are studied in a large centrifugal compressor. The models of subsystems, such as coupling and bearing, are established by appropriate simplification. The finite element model of rotors is set up by taking interrelation of these subsystems into account. The unbalance responses and system stability are analyzed for overall unit and single cylinder. The results show that the critical speed and journal amplitude at working speed in the overall unit are greater than those of low pressure cylinder. The conclusion will provide guidance to compressor rotor system design.

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Hrishikeshavan, Vikram, and Inderjit Chopra. "Aeromechanics and Control of a Shrouded Rotor Micro Air Vehicle in Hover and in Edgewise Flow." Journal of the American Helicopter Society 56, no. 4 (October 1, 2011): 1–14. http://dx.doi.org/10.4050/jahs.56.042004.

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Shrouded rotors are efficient in hover but are quite sensitive to disturbances in external flow. In this paper, the dynamics and control of a shrouded rotor micro air vehicle is studied in hover and when it is subjected to edgewise gust. The importance of incorporating a hingeless rotor in a shrouded rotor configuration was shown and was flight-tested in hover using a proportional-integral attitude feedback controller. In edgewise flow, the shrouded rotor produced up to 300% higher pitching moment than the unshrouded rotor. To counter this pitching moment, the control moments were about 80–100% higher for the shrouded rotor. Time domain attitude dynamics identification of the vehicle, restrained in translation, was conducted with and without the flybar. It was shown to be desirable to incorporate a flybarless rotor for improved maneuverability and hover efficiency. A linear quadratic regulator (LQR) controller was developed based on the extracted attitude dynamics model. Gust disturbance rejection capabilities of the controller were tested with the vehicle in edgewise flow using a spherical gimbal setup. The shrouded vehicle was found to tolerate up to 2 m/s of edgewise gusts, whereas the unshrouded configuration could reject gusts of up to 4.8 m/s.

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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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Whalley, R., and A. Abdul-Ameer. "Contoured shaft and rotor dynamics." Mechanism and Machine Theory 44, no. 4 (April 2009): 772–83. http://dx.doi.org/10.1016/j.mechmachtheory.2008.04.010.

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46

Stout, K. J. "Dynamics of rotor-bearing systems." Precision Engineering 12, no. 4 (October 1990): 247. http://dx.doi.org/10.1016/0141-6359(90)90069-b.

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Lee, Y. T., T. W. Bein, J. Feng, and C. L. Merkle. "Unsteady Rotor Dynamics in Cascade." Journal of Turbomachinery 115, no. 1 (January 1, 1993): 85–93. http://dx.doi.org/10.1115/1.2929221.

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A time-accurate potential-flow calculation method has been developed for unsteady incompressible flows through two-dimensional multi-blade-row linear cascades. The method represents the boundary surfaces by distributing piecewise linear-vortex and constant-source singularities on discrete panels. A local coordinate is assigned to each independently moving object. Blade-shed vorticity is traced at each time step. The unsteady Kutta condition applied is nonlinear and requires zero blade trailing-edge loading at each time. Its influence on the solutions depends on the blade trailing-edge shapes. Steady biplane and cascade solutions are presented and compared to exact solutions and experimental data. Unsteady solutions are validated with the Wagner function for an airfoil moving impulsively from rest and the Theodorsen function for an oscillating airfoil. The shed vortex motion and its interaction with blades are calculated and compared to an analytic solution. For a multi-blade-row cascade, the potential effect between blade rows is predicted using steady and quasi-unsteady calculations. The accuracy of the predictions is demonstrated using experimental results for a one-stage turbine stator-rotor.

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Magari, P. J., L. A. Shultz, and V. R. Murthy. "Dynamics of helicopter rotor blades." Computers & Structures 29, no. 5 (January 1988): 763–76. http://dx.doi.org/10.1016/0045-7949(88)90344-6.

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Chen, Yue, Jiwen Cui, and Xun Sun. "A Vibration Suppression Method for the Multistage Rotor of an Aero-Engine Based on Assembly Optimization." Machines 9, no. 9 (September 5, 2021): 189. http://dx.doi.org/10.3390/machines9090189.

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The assembly quality of the multistage rotor is an essential factor affecting its vibration level. The existing optimization methods for the assembly angles of the rotors at each stage can ensure the concentricity and unbalance meet the requirements, but it cannot directly ensure its vibration responses meet the indexes. Therefore, in this study, we first derived the excitation formulas of the geometric and mass eccentricities on the multistage rotor and introduced it into the dynamics model of the multistage rotor system. Then, the coordinate transfer model of the geometric and mass eccentricities errors, including assembly angles of the rotors at all stages, was established. Moreover, the mathematical relationship between the assembly angles of the rotors at all stages and the nodal vibration responses was established by combining the error transfer model with the dynamics model of the multistage rotor system. Furthermore, an optimization function was developed, which takes the assembly angles as the optimization variables and the maximum vibration velocity at the bearings as the optimization objective. Finally, a simplified four-stage high-pressure rotor system was assembled according to the optimal assembly angles calculated in the simulations. The experimental results showed that the maximum vibration velocity at the bearings under the optimal assembly was reduced by 69.6% and 45.5% compared with that under the worst assembly and default assembly. The assembly optimization method proposed in this study has a significant effect on the vibration suppression of the multistage rotor of an aero-engine.

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Wagner, Matthew B., Amir Younan, Paul Allaire, and Randy Cogill. "Model Reduction Methods for Rotor Dynamic Analysis: A Survey and Review." International Journal of Rotating Machinery 2010 (2010): 1–17. http://dx.doi.org/10.1155/2010/273716.

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The focus of this literature survey and review is model reduction methods and their application to rotor dynamic systems. Rotor dynamic systems require careful consideration in their dynamic models as they include unsymmetric stiffness, localized nonproportional damping, and frequency-dependent gyroscopic effects. The literature reviewed originates from both controls and mechanical systems analysis and has been previously applied to rotor systems. This survey discusses the previous literature reviews on model reduction, reduction methods applied to rotor systems, the current state of these reduction methods in rotor dynamics, and the ability of the literature to reduce the complexities of large order rotor dynamic systems but allow accurate solutions.

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Journal articles on the topic 'Dynamics of rotor'

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