Vibration Characteristics Of Rotor Research Articles

Nonlinear vibration characteristics of an aeroengine cantilever flexible rotor considering interference fit and unbalance

Aeroengine power turbine rotor is a typical nonlinear rotor system, in which the interference connection between long shaft and short shaft has a prominent influence on the coupling vibration of the system, especially at high speed, the nonlinear stiffness change of interference contact is more obvious. Therefore, the paper considers the change of the contact characteristics of the long shaft and the short shaft of the turbine rotor, and the nonlinear restoring force of the bearing to analyze the dynamic characteristics of the rotor. Firstly, according to the theory of elasticity, the contact parameters under different speed states are calculated, the contact stiffness model under interference fit is established, and the relationship between contact stiffness and speed is analyzed. Secondly, according to the Hertz contact theory, a bearing nonlinear restoring force model considering time-varying characteristics is established. Finally, the dynamic model of the bearing-flexible rotor coupling considering interference contact is established. The influence of contact parameters and unbalance parameters on the nonlinear vibration characteristics of the rotor is analyzed by amplitude-frequency curve, bifurcation diagram, time-domain waveform, spectrum diagram, trajectory diagram and Poincaré diagram. In addition, the simulation results are compared with the experiment results of the rotor test rig to verify the accuracy of the established dynamic model. By analyzing the influence of different parameters such as interference magnitude, unbalance position, unbalance magnitude and unbalance couple on the nonlinear vibration of the rotor, the basis for the design and vibration control of the cantilever turbine rotor is provided.

Rotor Vibration Characteristics Considering Nonlinear Stiffness of Spigot Bolts

Rotor Vibration Characteristics Considering Nonlinear Stiffness of Spigot Bolts

Joint degradation and its effect on rotor vibration characteristics considering bolt assembly process

Bolted joints are the major connection form to hold the aero-engine rotor system as a discontinuous entirety. What is noteworthy is that the bolt assembly process (BAP) directly relates the uniformity of preload and the symmetry of joint stiffness when the rotor comes to assembly, thereby introducing a heightened level of complexity and unpredictability to the dynamic response of the rotor system. In this paper, the effect of BAP on the stiffness softening of bolted flange joints is analyzed based on a finite element contact model. Then, a bolted joint rotor system finite element model is established to discuss the magnitude-frequency characteristic under three assembly sequences of bolts. The rotor vibration response is further compared between the three sequences considering the stiffness loss. Finally, the theoretical studies are verified by a rotor test rig. Results demonstrate that the stiffness softens to varying degrees with the increase of external load, and the softening mechanism is intricately associated with the contact state of the joint interfaces. Intriguingly, joint stiffness and its softening law are also affected by the BAP, leading to substantial discrepancies in rotor critical speed and vibration response among different assembly sequences. It is further observed that the tangential stiffness softening complicates the dynamic properties of the rotor system and enhances the nonlinear features.

Comprehensive Analysis on Rotor Vibration Characteristics Based on A Novel Dynamic Stator Interturn Short Circuit Model of Synchronous Generator

Comprehensive Analysis on Rotor Vibration Characteristics Based on A Novel Dynamic Stator Interturn Short Circuit Model of Synchronous Generator

Effect of Shaft Speed, Crack Depth and L/D Ratio in Rotor Bearing System: Using Taguchi Method and ANOVA

Vibration is produced by imbalance, positioning, mechanical softness, shaft cracking, and various defects in spinning machinery. In recent years, rotor defect diagnostics have become more important. This study looks at the effects of various input parameters, such as shaft operating speed, crack depths, and l/d ratio (ratio of the distance of crack from one end to the diameter of the shaft). A steel shaft with a disc positioned in the center and supported by two bearings was utilized to investigate the vibration characteristics of a shaft. An artificial fracture was introduced in order to notice the rotor's vibration characteristics when a defect is present. On a rotor with a diameter of 25mm, the signature knowledge was first obtained with fracture depths ranging from 1mm to 3mm. The amplitude and frequency of vibration in the rotor bearing system were used to analyse the results of the three input parameters. FFT analyzer was used to measure the amplitude and frequency (Fast Fourier remodel analyzer). The signals are processed using a high-speed fast Fourier remodel analyzer. To evaluate important input parameters affecting system vibrations, Taguchi and Analysis of Variance (ANOVA) methods were applied. The ANOVA was distributed with a 95% confidence level. The technique parameters with a p-value of less than 0.05 were mentioned as being critical to the response. Taguchi Analysis was used to determine the effect of the input parameters on the amplitude and frequency of vibration in the axial and vertical directions.

Analysis on Rotor Vibration Characteristics under Dynamic Rotor Interturn Short Circuit Fault in Synchronous Generators

A dynamic rotor interturn short circuit fault may occur during synchronous generator operation. However, there is no method to analyze the generator’s characteristics under the dynamic rotor interturn short circuit fault and identify the fault. In order to solve this problem, a new dynamic rotor interturn short circuit fault analysis model is creatively proposed through mathematical derivation. Firstly, the rotor vibration characteristics and the mechanical response under magnetic pull excitation are theoretically analyzed. In addition, a finite element modeling method for the dynamic rotor interturn short circuit fault is proposed, and an experimental device is designed. The model of a synchronous generator under the dynamic rotor interturn short circuit fault is established to obtain the rotor’s unbalanced magnetic pulls and mechanical responses by finite element calculation. Finally, the rotor vibrations are tested on a CS-5 prototype generator. The validity of the model is verified by finite element calculation and an experiment. This paper provides theoretical support for the diagnosis of a synchronous generator’s dynamic rotor interturn short circuit fault.

Vibration characteristics of linear and nonlinear dissipative elastic metamaterials rotor with geometrical nonlinearity

Theoretical researches on the vibration characteristics of a dissipative elastic metamaterials rotor with geometrical nonlinearity are presented in this work. Both linear and nonlinear damping cases are implemented in parallel to the spring of the unit. The dynamic model of the dissipative metamaterials rotor is built and discretized by the assumed mode method. Then the solutions of the nonlinear equations are obtained using the harmonic balance method, and the numerical integration method is applied to validate the solutions obtained by the analytical method. The comparisons of the dynamic behaviors for the rotor with different types of geometrical nonlinearities and dissipations are presented, and the effect of the distribution position of the absorber unit on the dynamic behaviors is investigated. The results show that the linear damping has a better capacity to reduce the amplitude compared to the nonlinear damping due to the energy dissipation near the resonance region. On the other hand, compared to the linear dissipation, the nonlinear dissipation has a better performance around the bandgap that forbids the propagation of the vibration. Moreover, these properties can be further improved by adjusting the position of the unit on the rotor. The results presented in this paper provide a theoretical basis for enhancing the properties of metamaterials rotors.

A method for the estimation of oil film parameters in an asymmetric rotor-bearing system

PurposeAsymmetric rotating machinery supported by oil film bearings is relatively common in practical applications. The purpose of this study is to propose a method for estimating the oil film parameters of the bearings in an asymmetric rotor-bearing system.Design/methodology/approachThe proposed method requires the finite element model and translational displacement responses at the center of mass and bearings locations to form a regression equation to estimate the unknown parameters. Due to the transverse stiffness of the asymmetric rotor is not symmetrical, the analysis and parameter estimation procedures are performed in a rotating coordinate. Numerical simulations were carried out to illustrate the vibration characteristics of the asymmetric rotor system. The proposed method is applied to the simulated responses to estimate the assumed oil film parameters. The influence of the estimated parameter deviations on the rotor dynamic characteristics is discussed.FindingsThe vibration characteristics of asymmetric rotors are different from those of symmetrical rotors. The bearing parameters estimated by the proposed method are close to the assumed values, within a maximum error of 9%. The deviations of the estimated parameters have little effect on the vibration characteristic of the rotor system.Originality/valueThe proposed method does not require changing the rotational speed or applying additional excitation force to the rotor, which is suitable for the field test.Peer reviewThe peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-04-2023-0111/

Analysis of the vibration characteristics of pin-connected hammer rotor of straw rubbing filament machine

The finite element method and the 3D laser Doppler measurement technology were used to simulate and test the vibration characteristics of the pin-connected hammer rotor. This was done to determine the critical speeds of the pin-connected hammer rotor of the straw rubbing filament machine and avoid the resonance of the straw rubbing filament machine during operation. The frequencies and mode shapes of the rotor’s first six free modes were determined. The accuracy of the pin-connected hammer rotor finite element model is validated by comparing calculation and test values. On this basis, the prestressed modes of the pin-connected hammer rotor under actual working conditions are calculated. The effect of the hammer swing angles rotating around the pin shaft is investigated, and the critical speeds of the pin-connected hammer rotor are calculated. The results indicate that the rotor has the same mode shapes at 11 kinds of joint swing angles, and the maximum relative error for each order frequency is 0.88%. It can be seen that the hammer-pin swing angles have little effect on the vibrational frequencies and mode shapes of the hammer-pin articulated rotor. Compared to the free modes, the prestressed modes all have an additional torsional mode and consist of two-mode shapes of global and local; the global mode shapes are similar to the free ones except for an additional torsional mode shape, with increased amplitudes and modal frequencies; the local mode shapes mainly occur in cutting knives and hammers. The critical speed range of the rotor of the 9ZR-2.2 straw rubbing filament machine must be 2076.99–2348.32 r/min which is based on ensuring the processing quality of straw. The study provides a reference method for investigating the vibration characteristics of pin-connected hammer rotors. It is also of great practical importance to scientifically predict the critical speed of a pin-connected hammer rotor in order to reduce failure and safety accidents.

Vibration characteristics of multi-acoustic metamaterials rotor with geometrical nonlinearity

Vibration characteristics of multi-acoustic metamaterials rotor with geometrical nonlinearity

METHODS FOR ASSESSING THE TECHNICAL CONDITION OF DRILL ROTORS

This article, devoted to methods for assessing the technical condition of drill rotors, will help to consider the problem of servicing industrial equipment. The relevance of this work lies in the fact that in today's time, with the development of industrial sectors, both in our country and in other countries, there is a need for new and effective approaches to assessing the technical condition of equipment. Especially with the expansion of the boundaries of the oil and gas industry, the number of unexplored deposits is increasing. To process such deposits, there is a need to introduce new methods of maintenance. In order to increase the productivity of equipment that works for a long time, sometimes continuously, it is important to adhere to certain service methods. The aim of the work is to study the available methods for assessing the technical condition of drill rotors and propose a new integrated approach that combines the available indicators and criteria of known methods. This article discusses in detail the methods for assessing the technical condition of drill rotors, their characteristics are studied. The objectives of this work are to analyze the available methods for assessing the technical condition of drilling equipment, to determine the procedure for establishing the noise and vibration characteristics of rotors, to develop criteria for assessing the technical condition of the rotor. The article also analyzes the factors affecting the operation of drill rotors in operating conditions. Having studied the existing methods, a new integrated method is proposed, which, through a point approach and the choice of a specific method, based on the available data on the unit, will ensure higher reliability and longevity of the drill rotors used. The use of an integrated method is based on the calculation of all important points that are relevant to the object under study. The proposed method will have to reduce errors and malfunctions of drill rotors, increase the accuracy and service life of the equipment. The choice of an integrated method will help to ensure the continuous operation of drill rotors in industrial enterprises. Keywords: drilling rotor, method, control, damage, wear, factors, detection, vibration monitoring, noise characteristics, evaluation.

Anisotropic Vibration Characteristics Analysis of Steam Turbine Rotor Influenced by Steam Flow Excited Force Coupling Thermal and Dynamic Loads

Abstract In order to reveal the influence of thermal and dynamic loads coupling on the vibration characteristic of steam turbine rotor, the high-pressure cylinder anisotropic rotor of a 1000-MW ultra-supercritical steam turbine was modeled by the lumped mass method. The steam flow excited force of the front eight stages obtained through the numerical simulation before and after the coupling was converted to the equivalent gas bearing and added on the rotor, and the influence of steam flow excited force on rotor vibration characteristics was obtained by the Riccati transfer matrix method. The results show that, considering the thermal and dynamic loads, the two ends of the ellipse trajectory are smaller and the middle is larger. Before and after coupling thermal and dynamic loads, the azimuth of ellipse trajectory increases with the increase of load and nodes. The greater the load, the greater the changing range of azimuth. As the load increases, the first-order natural speed of the rotor increases and the second-order natural speed decreases, but the natural speed after the coupling is noticeably lower than that before the coupling. The changing scope of the first-order amplitude shrinks with the load increasing. The first-order logarithmic decrement rate can be increased under the relatively higher load by coupling thermal and dynamic loads, but the stability margin of rotor is insufficient, which causes the instability.

Nonlinear response of rotor system with bearing dynamic misalignment

Aiming at the nonlinear vibration problem caused by the dynamic misalignment of rolling bearings in the rotating machinery, a rotor dynamic model with bearing dynamic misalignment is established, and the effects of the dynamic misalignment of single and two bearings and the phase relationship of two dynamic misalignment bearings on the rotor vibration characteristics are researched. The effects of bearing clearance, raceway curvature radius, the ball number and radial load on the nonlinear vibration response of the dynamic misalignment bearing-unbalance rotor system are further analyzed. The results show that the dynamic misalignment of the bearing can excite the vibration at twice the rotor frequency, raise the resonance speed and enhance the hardening-type nonlinearity characteristics of the rotor. The influence of dynamic misalignment under two bearings with out-of-phase on rotor resonance is greater than that of the in-phase. The stability of the system can be improved by decreasing the bearing clearance and increasing the curvature radius coefficient. The vibration caused by bearing dynamic misalignment can be reduced by selecting the bearing with more balls and appropriately increasing the bearing load.

Analysis and Research on Vibration Characteristics of Nuclear Centrifugal Pumps Rotor Rubbing Fault

To investigate the vibration characteristics of nuclear centrifugal pumps rotor rubbing fault, the mechanical model of rotor rub is established, and the causes, types, and mechanisms of rotor rub fault are introduced. Taking the HAZ50-250 Type Horizontal single-stage centrifugal pump prototype as the object, through a reasonable test scheme, the vibration test and analysis of the rotor under different rub conditions were carried out using the Enpac2500 Dual channel spectrum analyzer, and the fault data of different rub impact degrees were collected. Combining the characteristics of vibration parameters such as time-domain, frequency-domain, and axis trajectory, it is found that the time-domain signal of rub fault shows an obvious “Top Clipping phenomenon.” The frequency-domain signal is mainly concentrated in one-time rotation frequency, two times rotation frequency, and a large number of nonlinear high harmonics. The axis trajectory will produce a concave image in the rub direction. In the actual rotor rub vibration fault diagnosis, it is necessary to comprehensively judge the vibration caused in combination with the operating state of the centrifugal pump, the state of the time domain, the frequency domain, and the axis trajectory. Based on the analyzed spectrum characteristics of the rub impact vibration, it is applied to the vibration fault diagnosis case of the centrifugal pump in the power plant, which timely prevents the pump damage and other faults caused by the deterioration of the rub impact fault, and plays a key role in the safe and stable operation of the centrifugal pump. It also provides an important reference for pump design and vibration fault diagnosis of rotating equipment in nuclear power plants.

Effect of static/dynamic air‐gap eccentricity on stator and rotor vibration characteristics in doubly‐fed induction generator

Effect of static/dynamic air‐gap eccentricity on stator and rotor vibration characteristics in doubly‐fed induction generator

The coupling free vibration characteristics of a rotating functionally graded shaft-disk system in thermal field

The numerical model of a functionally graded (FG) shaft-disk rotor system with flexible shaft and flexible various-thickness disk as components is established to investigate the coupling free vibration behavior of this rotor system in thermal field. Considering the thermophysical properties of the material, the properties of functionally graded material vary continuously according to the power law with the thickness of the disk. Based on the theory of rotor dynamics, the kinetic energy expression and strain energy expression of rotating shaft-disk system are obtained. In the framework of Ritz method, the global control differential equation of the rotor system assembled by shaft and FG disk is established by using differential quadrature finite element method. On this basis, a set of numerical examples are presented to perform convergence, correctness and effectiveness verification of the current model. Moreover, the influence of temperature difference, rotating speed, geometric and material parameters on the thermoelastic coupling vibration characteristics of light-weight shaft-disk rotor is discussed in detail, which can help to improve the rotor vibration performance in design work and future research.

1.5 kW 유도전동기 엔드링 기공이 회전체 진동 및 베어링 내구성에 미치는 영향 분석

This paper presents the results of rotordynamic analyzing the effect of the end-ring porosity of a 1.5 kW induction motors on the rotor vibration and the bearing durability. Firstly, the end ring porosity shape of the induction motor was simplified by the porosity cross-sectional area (S) and porosity distribution angle (θ), and a mathematical model was established to calculate the amount of unbalance. The amount of unbalance due to porosity shape was analyzed through a mathematical model. As a result, it was confirmed that the amount of unbalance significantly increased to more than the balancing grade G40 by S and θ. In general, the proper balancing class for induction motors is G2.5. Second, a rotordynamic analysis model was developed that can predict the vibration characteristics of rotor. In addition, the analysis model was validated through the modal test. Finally, the vibration characteristics of the rotor were analyzed according to the amount of unbalance and phase angle through the rotordynamic analysis. As S decreases, the maximum rotor amplitude linearly decreased and the bearing life increased. As θ increases, the maximum rotor amplitude nonlinearly decreased and the bearing life increased. As the phase angle increases, the maximum rotor amplitude decreased by 75% and the bearing life increased 63 times.

Dynamic modeling and stability analysis of a rotor-bearing system with bolted-disk joint

In large rotating machines, the rotor system involves multistage disks, where bolted joints are the basic form to connect the adjacent disks. Those bolted joints, subjected to unbalanced forces and moments during normal operation, influencing the rotor dynamics and giving rise to different motion states, which are of interest for investigations focusing on vibration signatures and dynamic stability. However, little research has been done on the rotor vibration characteristics considering dynamic parameters of bolted-disk joints. Thus, the bolted-disk joint element with two nodes is proposed by characterizing the mechanical relationship between the adjacent disks in this paper. Then, in terms of the proposed joint element and lumped mass modeling method, the dynamic model for the rotor system with a bolted-disk joint is established. After that, the responses of the system are solved numerically using the Newmark-β method, and bifurcation diagram, three-dimensional spectral plots, Poincare maps as well as spectral plots are used to analyze the dynamic behaviors under different tangential stiffness and transition point of bending stiffness of the bolted joint. Additionally, the influences of the bending stiffness of bolted-disk joint on system response are also examined. Finally, utilizing the rotor dynamic responses experiment performed at a bolted-joint rotor-bearing test rig with an electric tightening wrench, some of the results from the simulation study are verified. The present work provides a theoretical basis for detecting the performance of the bolted joint of the rotor-bearing system, and prevent failure caused by changes in the stiffness of the bolted joint.

Vibration analysis of three-DOF motor with liquid suspension based on fluid-solid coupling

Based on the combination of elastohydrodynamic lubrication and contact deformation theory, i.e. fluid-solid coupling theory, and considering the surface roughness of stator and rotor, a three-degree-of-freedom vibration model of spherical bearings with spiral grooves is established. The finite difference method is used to calculate and analyze the distribution of lubricating film pressure, film thickness and the influence of eccentricity of rotor on film pressure. Combining the stiffness of lubricating oil film with the finite element method, the displacement, stator vibration speed, acceleration and displacement of lubricating oil film are calculated from the angle of elastic boundary, and compared with the slotless structure. The results show that the bearing capacity of lubricating oil film of spherical bearing is improved and the stability of continuous oil film is improved by adding spiral groove. Secondly, the vibration characteristics of stator and rotor with spiral groove structure are more in line with the viscoelastic periodic distribution law. The vibration stability of the system is improved. In order to further optimize the vibration stability of the motor, the theoretical basis is provided.

Rotor UMP characteristics and vibration properties in synchronous generator due to 3D static air‐gap eccentricity faults

In this article, the qualitative theoretical derivation, together with finite element analysis and experimental studies are presented to investigate the unbalanced magnetic pull (UMP) as well as the rotor vibration characteristics. Differently from previous studies, this study focuses on the UMP/vibration not only under the normal and the conventional radial rotor eccentricity conditions but also for three-dimensional (3D) hybrid static air-gap eccentricity (SAGE) cases which are composed of both the radial SAGE and the axial SAGE. The detailed UMP expressions before and after each SAGE, are first deduced based on the analysis of the magnetic flux density variation. Then, the 3D finite element calculation and the experimental study are carried out on the CS-5 prototype generator which has two poles and a rated speed of 3000 rpm in order to validate the proposed theoretical analysis. It is shown that the DC component and the even harmonics of the radial UMP/vibration, especially the second harmonic, increase under the SAGE conditions. Specifically, the increment of the radial SAGE increases both the radial and the axial UMPs/vibrations, while the growth of the axial SAGE increases the axial UMP/vibration but meanwhile reduces the radial UMP/vibration.