Rotor Coupling Research Articles

Design and Analysis of Double-Rotor Flux-Reversal PM Magnetic Differential Motor With Suppressed Rotor Coupling

Design and Analysis of Double-Rotor Flux-Reversal PM Magnetic Differential Motor With Suppressed Rotor Coupling

Digital Simulation of Coupled Dynamic Characteristics of Open Rotor and Dynamic Balancing Test Research

An aero engine, as the core power equipment of the aircraft, enables safe and stable operation with a very high reliability index, and is an important guarantee in flight. The open rotor turbine engines (contra-rotating propeller) have stood out as a research hotspot for aviation power equipment in recent years due to their outstanding advantages of low fuel consumption, high airspeed, and strong propulsion efficiency. Aiming at the problems of vibration exceeding the standard generated by imbalance during the operation of the dual-rotor system of aircraft development, the difficulty of identifying the coupled vibration under the micro-differential speed condition, and the complexity of the dynamic characteristic law, a kind of numerical simulation of the dynamics based on the finite element technology is proposed, together with an experimental research method for the fast and accurate identification of the coupled vibration of the dual-rotor system. Based on the existing open rotor engine structure design to build a simulation test bed, establish a double rotor finite element simulation digital twin model, and analyze and calculate the typical working conditions of the dynamic characteristics of parameters. The advanced algorithm of double rotor coupling vibration signal identification is utilized to carry out decoupling and dynamic balancing experimental tests, comparing the simulation results with the measured data to verify the accuracy of the technical means. The results of the study show that the vibration suppression rate of the finite element calculation simulation test carried out for the simulated double rotor is 98%, and the average vibration reduction ratio of the actual field test at 850 rpm, 1000 rpm, and 3000 rpm is over 50%, which achieves a good dynamic balancing effect, and has the merit of practical engineering application.

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.

Analysis of Vibration and Noise in Electric Drive System Under Resolver and Motor Rotor Coupling Eccentricity

Eccentricity in a permanent magnet synchronous motor (PMSM) can cause additional electromagnetic forces and resolver error, which in turn can lead to an aggravation of vibration and noise in the electric drive system. In this paper, the additional electromagnetic forces and the resulting vibration and noise under the conditions of the three-dimensional (3-D) static and dynamic motor eccentricities, the resolve error, and the coupling between these faults, are analytically derived and analyzed, with special emphasis on the coupling effect of the motor eccentricity and resolver error. The results of the present theoretical analyses agree well with those from the finite element simulations and the experimental measurements. It can be concluded from the results that the coupling between the 3-D motor eccentricity and the resolver error will induce additional electromagnetic forces with much more diverse spatial orders and frequencies.

Splitting of waves in rotor-in-rotor nonlocal metamaterials by internal rotor coupling

Mechanical metamaterials can be used to control wave propagation because they are flexibly adjustable. In this paper, a one-dimensional rotor-in-rotor metamaterial with internal rotor coupling is proposed. This metamaterial introduces a new connection between lattices into a rotor-in-rotor system to produce a nonlocal metamaterial. Meanwhile, a zero-frequency bandgap with negative mass can be obtained. The vibration reduction efficiency of bandgaps is analysed based on the recursive method and numerically verified. Furthermore, wave splitting is found in the rotor-in-rotor metamaterial due to strong equivalent nonlocal interactions. Its dispersion relation shows a “dual wavevector” phenomenon: there are frequency ranges where a positive slope and a negative slope coexist. Numerical simulations using finite cell analysis are performed to validate the wave splitting by calculating the phase velocity and group velocity. The finding of wave splitting in the dual wavevector region is expected to provide new insights to control wave propagation.

Simulation analysis of dynamic coefficients for high-speed water-lubricated bearing-rotor system of satellite

With the development of space technology, the traditional aerospace cooling technology is hard to meet the constantly developing requirements of heat dissipation. In order to address the problem of temperature control for aerospace systems, the pump-driven fluid loop system has been often adopted. In the pump-driven fluid loop system, the rotor system is needed to be analyzed. In this paper, the rotor coupling system of the canned pump with multiple journal bearings has been studied based on the bearing data, lumped parameter method, Reynolds equation and finite element method. By solving the Reynolds equation, parameters of each bearing have been solved, and a database file has been formed. The bearing data have been addressed by linear interpolation. In this study, the static indeterminate problem has been combined to analyze the bearing force, and the bearing characteristic parameters under the steady-state condition have been solved based on the iterative method. The results indicated that the influences of clearance ratio and rotational speed on the natural frequency, critical rotational speed and unbalanced response of the rotor show certain regularity. The study provides a theoretical basis for the stable operation of the whole rotor system.

Study on time-varying mixed lubrication performance of microgroove journal-thrust coupled bearing under water lubrication

PurposeThe purpose of this study is to numerically investigate the time-varying mixed lubrication performance of microgroove journal-thrust coupled bearing (MJTCB) under nonlinear excitation.Design/methodology/approachA three degree of freedom (3-DOF) dynamic model of the rotor coupling with the transient mixed lubrication behavior is established. Based on numerical predictions, the role of the microgroove on the time-varying mixed lubrication performance of MJTCB is identified. The effects of the microgroove depth, microgroove shape and external load on the time-varying mixed lubrication performance of MJTCB are also studied.FindingsNumerical results show that the effect of the coupling hydrodynamic on the time-varying mixed lubrication performance of the coupled bearing is strengthen with the increasing of microgroove depth. Furthermore, it is found that the optimal microgroove shape for the thrust bearing, arc or rectangle, highly depends on the microgroove depth. Finally, the contact performance of the thrust bearing is slightly affected by the radial external load.Originality/valueThis study is expected to achieve a better understanding of the time-varying mixed lubrication performance of MJTCB under nonlinear excitations.

Development and Performance Measurements of Gas Foil Polymer Bearings with a Dual-Rotor Test Rig Driven by Permanent Magnet Electric Motor

The rotordynamic stability of journal gas foil–polymer bearings (GFPBs) applied to a dual-rotor bearing system was investigated. The GFPB has a high damping structure, i.e., it has an additional polymer layer, and top/bump/bottom foil structures. Test GFPBs were fabricated with nitrile butadiene rubber polymer layers with a thickness of 2 mm. Static-load-deflection tests of test gas foil bearings (GFBs) and GFPBs were performed to estimate the geometric bearing clearance (200 µm). The dual-rotor rotordynamic test rig consisted of a motor rotor, test rotor, and beam-type coupling. Two journal test bearings were installed on both the drive-end and non-drive-end sides of the test rotor. Predicting and testing the natural mode characteristics of the dual rotors revealed that the relative error between them was less than 7%, indicating that the first and second natural frequencies were 15 Hz and 160 Hz, respectively, and the third natural frequency was 1835 Hz in the tests. Based on the API 612 standard, the upper limit of the rotating speed for the test rig was limited to be approximately 92 krpm with a separation margin of 26%. Rotordynamic tests were conducted to examine the stability performance of GFBs and GFPBs, where the adjusted bearing clearance was 150 µm. The test results indicate that GFPBs have better stability performance in terms of delaying and suppressing unstable vibrations than GFBs. Specifically, GFPBs showed stable synchronous and subsynchronous responses up to a maximum rotating speed of 80 krpm. As a result, GFPB is a reliable lubricating element that can be used for vibration dampening in machines operating at relatively low temperatures.

Splitting of Waves in Rotor-in-Rotor Nonlocal Metamaterials by Internal Rotor Coupling

Splitting of Waves in Rotor-in-Rotor Nonlocal Metamaterials by Internal Rotor Coupling

Multimachine stability enhancement with hybrid PSO-BFOA based PV-STATCOM

The article explores the mitigating capabilities of a large PV-farm as a PV-STATCOM (Static synchronous compensator) in quenching the power system oscillations in a multimachine power system. Power system oscillations include fluctuation in the rotor dynamics (generator speed and angle), coupling voltage, and shaft torsions. At dusk, the PV-farm starts operating as VSC (Voltage Source Converter)-STATCOM deploying its entire inverting capabilities for suppressing the oscillations. While at the full sun during the faults, the solar-farm instantly ceases the real power generation and, operating as a PV-STATCOM until the normal operating states are resumed. The paper demonstrates the optimizing capabilities of a Bacterial Swarm Optimization (BSO), a hybrid of particle swarm and bacterial foraging optimizations in controlling the power flow of PV-STATCOM deployed in the literature. Kundur’s modified two-area model integrated with a largescale PV-farm is designed in Matlab to probe the rotor swings with torsional deviations in the interconnected shaft segments. The results for several test cases including without-with and BSO-tuned PV-STATCOM reveal the optimizing capabilities of the proposed BSO-based controller in alleviating the power system oscillations in the multi-machine power system.

Repair of Cracked 150 MW High-Pressure Steam Turbine Rotor Coupling

A 150 MW high-pressure steam turbine rotor in Philippine experienced cracking in coupling area. The root cause of crack failure was investigated, and it was revealed that alignment setup design from original equipment manufacturer (OEM) contributed to the failure. The cracked coupling was restored by weld build up back to original dimension and new alignment target was recalculated and the result was counterchecked by finite element analysis (FEA) method to verify the stress level reduction.

A simulation of an electric machine considering the coupling of rotor‐ and electrodynamics

AbstractIn this paper, a method is presented to determine the vibrational behavior of an electric motor and the associated structure. Therefore, a holistic simulation approach is used, which takes into account the mutual influence of structural mechanics and electrodynamics. For this purpose, a multi body simulation (MBS) is extended so that electromagnetic loads can be considered, which are calculated by using the finite element method (FEM). In electric machines an undisturbed and constant magnetic field is of great importance. Even small variations of the air gap lead to changes in the magnetic field compared to the ideal geometry, which cause a change in the resulting torque and vibration excitation. Especially local and global asymmetric air gap changes due to load‐ and operation‐dependent deformations of the stator and rotor are problematic. Such deformations result on the one hand from the electromagnetically excited structural vibrations and on the other hand from the rotordynamic loads. For these reasons, it is necessary to consider the electro‐ and structural‐dynamic effects together. The developed method is presented on a simple generic motor to show the influence of the coupling.

Triple resonances involving two frequencies in the motor frequency conversion start phase

A rigid body model of torsional vibration of stator and rotor coupling system excited by electromagnetic force of motor is established in this paper. Energy method is introduced to solve the nonlinear vibration of the coupling system. Based on the linear part of the kinetic energy, potential energy and air gap magnetic field energy, the Lagrange function is obtained. And then, the Lagrange-Maxwell equation is used to solve natural characteristics. The nonlinear part is used to derive the nonlinear vibration equations of coupling system in torsional vibration modes. With numerical calculation, considering the triple resonances involving two natural frequencies, the influences of tuning parameters, damping coefficient and magnetic flux-density on resonance characteristics are illustrated and analyzed by the frequency-response curves. The results provide a theoretical basis for the subsequent calculation.

Rotorcraft fuselage/main rotor coupling dynamics modelling and analysis

Abstract This article presents the fuselage/main rotor coupling dynamics under a modal analysis to study the modes of oscillation. The authors provide a rotorcraft simulation model that captures complex dynamics, wherein the validation is done with existing theories. The model has been set up by using VehicleSim, software specialized in modelling mechanical systems composed by rigid bodies. It is presented a helicopter simulation framework, that allows to study the impact of the main rotor varying angular speed on the system. Moreover, the generated heterodyning behaviour and harmonics can be analysed on the fuselage. The detection of this performance is not a simple task, and this helicopter model provides an accurate system for its study using a short-time Fourier transform processing. The coupled dynamics observed between the fuselage and the main rotor indicate that the model can be a suitable tool to detect this type of performance.

Energy levels of a coupled-rotors model

We calculate the energy levels of a coupled-rotors model that has proved useful for the analysis of the multiple tunnelling peaks in the inelastic neutron scattering from 4-methylpyridine crystals. We resort to the Rayleigh–Ritz variational method with a basis set for each irreducible representation. The energy levels in terms of the rotor coupling strength exhibit a rich pattern of crossings between states of different symmetry and avoided crossings between states of the same symmetry.

Technical Diagnostics and Adjustment of Steam Turbine Units

The main activities conducted at the department for technical diagnostics and repair technologies of the All-Russia Thermal Engineering Institute (JSC “VTI”) are described. It is shown that the diagnostics of the main and auxiliary power equipment can be efficiently performed using specialized monitoring tools. Effective methods and tools for assembling rotor couplings of turbine units are presented. Technologies for repairing the blade apparatus of steam turbines arereviewed.

Spectrum Analysis of a Coaxial Dual-Rotor System with Coupling Misalignment

The finite element model of a dual-rotor system was established by Timoshenko beam element. The dual-rotor system is a coaxial rotor whose supporting structure is similar to that of an aero-engine rotor system. The inner rotor is supported by three bearings, which makes it a redundantly supported rotor. The outer rotor connects the inner rotor by an intershaft bearing. The spectrum characteristics of the dual-rotor system under unbalanced excitation and misalignment excitation were analysed in order to study the influence of coupling misalignment of the inner rotor on the spectral characteristics of the rotor system. The results indicate that the vibration caused by the misaligned coupling of the inner rotor will be transmitted to the outer rotor through the intershaft bearing. Multiple harmonic frequency components, mainly 1x and 2x, will be excited by the coupling misalignment. The amplitudes of all harmonic frequencies increase with the misalignment in both the inner and outer rotors. The vibration level of the outer rotor affected by the misalignment is lower than that of the inner rotor because it is far from the misaligned coupling. Harmonic resonance occurs when any harmonic frequencies of the misalignment response coincide with a natural frequency of the system. In order to verify the theoretical model, experiments are performed on a test rig. Both the experimental and simulation results are in good accordance with each other.

New rotational levels in 186Re nucleus

Excited levels of 186Re have been studied using results of the single γ-ray spectra measurements following the thermal neutron capture reaction. Energies and intensities of more than 500 γ-transitions have been obtained with the high-resolution crystal diffraction spectrometer GAMS5 of ILL. Most of the obtained intense γ-transitions have been placed in the 186Re level scheme. A number of new levels, as well as the depopulation for levels observed earlier in the 187Re(p,d)186Re reaction measurements have been proposed. Structure of 186Re levels is interpreted in terms of two-quasiparticle plus rotor coupling model and compared with that of the neighbouring doubly-odd nucleus 188Re.

A novel double rotor coupling model for inner bore grinding process

Hydrostatic bearings are the supporting parts of hydrostatic spindles. Hence, the bearing inner bore roundness may affect the spindle shaft equilibrium position and rotation accuracy. Although many scholars have established various models to simulate the internal and external grinding process, the existing models cannot provide precise calculations for choosing an efficient grinding strategy, and the final bore roundness predictions are also insufficient. To achieve precise prediction for grinding process and final bore roundness, the coupling interaction between the grinding wheel spindle system and the workpiece-spindle system during the inner bore grinding process is considered, and then a novel inner bore grinding double rotor model is established. The model adopts iterative algorithm to calculate material removal and the bore roundness forming process. Based on the model, different inner bore grinding strategies are quantitatively simulated for a given grinding system. The material removal and inner bore forming process under different grinding conditions are compared. The final bore roundness roughly matches the experiment results. The proposed double rotor system model and the simulation algorithm could be a new path for further studies of the grinding transition process.

Investigating the dehumidification characteristics of the low-pressure stage with blade surface heating

At present, the vast majority of electricity is generated by steam turbines. Nonequilibrium condensation will occur in the low-pressure stage, which will not only reduce efficiency but also corrode blades and endanger the safety of the steam turbine. The aim of this work is to optimize the blade surface volume heating scheme to reduce the wetness loss. Based on thermodynamic theory, the nucleation model and droplet growth model were studied. A two-fluid model of homogeneous condensation was established from the point of view of the volume average, and the accuracy of the model was verified. The effects of stator blade surface volume heating, rotor blade surface volume heating and coupling heating on the wet steam condensation characteristics in the nucleation stage were analyzed. The research shows that stator blade surface volume heating can satisfactorily prevent steam condensation. When the stator blade surface volume heating rate is 0.375 J /(mm2·s), the average outlet wetness of the stage is 0.0158, which decreases 69.34% compared with the non-heating condition, and the entropy increase is only 0.26% higher than that of the non-heating condition. Blade surface heating can inhibit steam condensation very well and improve the turbine efficiency to a certain extent.