Vibration Rotation Research Articles

The application of the bilinear foil model to three-pad foil air bearings in rotordynamic analysis including reduced order modelling

Foil air bearings (FABs) are the mainstay of oil-free turbomachinery technology which is undergoing rapid expansion. A rotor system using such bearings is a nonlinear multi-domain dynamical system comprising the rotor, the air films and the foil structures. Multi-pad (segmented) FABs offer opportunity for enhanced stability performance but are naturally more computationally challenging than single (360°) pad FABs. Their analysis has been limited to a simple model that ignores the detachment of the top foil from the underlying foil. Although a correction can be applied for the rotor vibration, the actual top foil deflection cannot be predicted. Additionally, reduced order modelling techniques have so far not been applied to such bearings. This paper presents the nonlinear and linearised dynamic analyses of three-pad FAB rotor systems considering foil detachment and using both Galerkin Reduction (GR) and Finite Difference (FD) to model the air film. Various models for the force distribution on the top foil are considered for use within a bilinear foil model, focusing on the ability to achieve numerical convergence. GR halved the computation time for a waterfall graph, without compromising the accuracy of the prediction of the nonlinear response. The results are validated against results from the literature.

Development of an Industrial Safety System Based on Voice Assistant

Currently, there are limitations in the human–machine interfaces (HMIs) used in industry, either due to the characteristics of users’ cognitive abilities or interfaces, which hinder communication and interaction between humans and equipment. For this reason, this work presents an alternative interaction model based on a voice assistant, Alexa, which promotes more natural, intuitive, direct, and understandable communication. The purpose of this work is the development of an industrial safety system for a controlled electric motor based on Alexa voice assistant, which allows the monitoring of its operating parameters, such as phase current, housing temperature, and rotor vibration, as well as making it possible to control ignition and shut down and change the rotation of the motor with a prior password, as a safety measure. Commercial smart devices and Arduino-compatible modules were used to achieve this, providing them with the Internet of Things (IoT) feature. In addition, several software platforms, such as Blynk, Tuya Smart, Node Red, and Voiceflow, are used to perform data transmission, device management, and programming of the Alexa skill, oriented to the execution of the security and run system. This shows the potential capacity of voice assistants in the industry to deliver information more naturally to humans and obtain optimal notifications. However, problems were evidenced, such as the influence of noise in the environment when communicating with the assistant, the vocalization of words, low voice tones, and accents typical of the language, that will increase the security level of the system and prevent potential identity theft.

Analysis of High-Speed Rotor Vibration Failure Due to Sudden Angular Deformation of Bolt Joints

As the efficiency of advanced aero engines improves, the operational speed of their rotors increases. This heightened operational speed makes the rotor dynamics highly sensitive to changes in the rotor’s mass asymmetry state, or unbalance state. During the use of a dual-spool turbofan engine, when its supercritical high-pressure rotor (HPR) exceeds a certain operational speed, the rotor’s vibration spikes and continues to increase with the operational speed until it drops sharply near the maximum operational speed. Analysis of the bolt joints in the faulty rotor reveals various phenomena such as joint interface damage, changes in bolt loosening torque distribution, and alterations in rotor initial unbalance. This paper proposes that at high operational speeds, the bolt joint of the HPR undergoes sudden angular deformation, resulting in the slanting of the principal axis of inertia of the turbine disk. This slant leads to changes in the unbalanced state of the HPR. The additional unbalance causes a sudden rotational inertia load excitation, triggering the rotor vibration failure. Subsequently, a rotor dynamic model that incorporates the angular deformation of the joints is established to simulate how this joint deformation influences the dynamic response of the rotor. The simulation results align well with the observed failure phenomenon and validate the proposed failure mechanism. Finally, troubleshooting measures are proposed and implemented in the faulty engine, effectively mitigating the vibration fault.

Investigation on the dynamic characteristics of a rotor-damper-casing coupling system under diving-climbing maneuver

The thin-walled casing and squeeze film damper (SFD) of an aero-engine have significant effects on the vibration of the rotor during maneuvering flight. However, few studies have been conducted on the vibration responses of a rotor-damper-casing coupling system under this condition. This paper uses Lagrange's principle to derive the equation of motion for a rotor system that considers the flexible casing and static eccentricity of the SFDs during maneuvering flight. The model of a casing is established, and the frequency response functions (FRFs) with pre-stress are calculated by converting the flight parameters to pre-stress. Then, the FRFs are generated for various flight statuses and combined with the rotor finite element model using the linear interpolation method. The vibrations of a dual-rotor system during the diving-climbing maneuver are calculated by the Hilber-Hughes-Taylor-α (HHT-α) method. The results indicate that the deflection will appear in the rotor vibrations during maneuvering flight. The flexible supports of a casing make the vibration transfer between the High Pressure and Low Pressure rotors, and there are harmonic and subharmonic components in the vibrations of a rotor-damper-casing coupling system. Due to the influence of a flexible casing, the vibrations of a rotor vary at different speeds under the diving-climbing maneuver, even if the speed is far from the critical speed. This study illustrates the significance of considering the flexible casing and the SFD during maneuvering flight.

An experimental and FEA approach to investigate effect of cracks on a rotor bearing system

The field of rotordynamics primarily focuses on the analysis and characterization of lateral and torsional vibrations of rotor bearing system. In this study, the lateral vibrations of a single disc rotor bearing system are studied. The effect of crack location, crack depth, and number of cracks has been studied for structural health monitoring of shafts. For the finite element approach, Ansys version 19.0 is used, and a modal analysis was conducted in order to determine the participation factor and bending modal frequencies. Also, a Campbell diagram for critical speeds and whirl direction is plotted. A single-disc rotor bearing system is treated as a simply supported case. Experimental performance has been carried out on a self-designed testbed, and results are obtained using a DEWEsoft FFT Analyzer. A plot of the frequency spectrum is plotted for all shaft cases. After comparing FEA and Experimental results, a maximum variation of 5 percent was found. The investigational results are corelated; hence, the above methodology for rotordynamic analysis may be suggested.

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.

Flexible rotor unbalance fault location method based on transfer learning from simulation to experiment data

In the study of the high-speed dynamic balance of flexible rotors, rotor unbalance positioning is a challenging topic. Particularly for slender rotors, the axial position of the unbalance has an important influence on the high-speed dynamic balance. The unbalance at different axial positions is not the same or even opposite in different rotor mode vibration behaviors. If the unbalance position of a rotor can be identified, the actual unbalance of the rotor can be reduced from the root. This balance method has the same effect in each vibration mode of the rotor; hence, low-speed dynamic balance can be realized to replace high-speed dynamic balance, considerably saving on costs. Deep learning based on few labeled samples can achieve good results for the identification of unbalanced positions; however, there are infinite potential positions of unbalance in the actual rotor. It is difficult to collect sufficient labeled samples to train a reliable intelligent diagnostic model. Fortunately, a large number of rotor vibration datasets labeled with different unbalance positions are available using the rotor dynamic model, and the unbalance position data calculated using the dynamic model contain diagnostic knowledge related to the rotor unbalance position data measured in the rig. Hence, inspired by transfer learning, this study proposed a transfer learning method using dynamic model simulation and experiment data for flexible rotor unbalance fault location. Cross-domain deep transfer recognition of rotor unbalance position was realized.

Novel features of nuclear spectra of light mass Os isotopes

The (N=88-108) light mass Os isotopes exhibit level spectra different from the heavier (N > 108) isotopes. The spectral pattern, for ground, β- and γ- bands is illustrated empirically, and analyzed in terms of the collective rotation vibration model and the algebraic sd Interacting Boson Model IBM-1. The variation of the spectral features with neutron number N has been linked to the odd-A neighbors and to the occupation of the underlying Nilsson orbits. The quadrupole β vibration produces the axially symmetric shape of light mass Os isotopes, in contrast to the main role of the asymmetry parameter γ in the heavier Os isotopes. The energy level spectra, and the inter band B(E2) ratios in IBM-1 reproduce the shape variation from spherical to the X(5) symmetry status, and to the prolate deformed rotor, as in experiment. This reveals the interesting physics of the rotation vibration model by high lighting the special features of the light mass 164−184Os isotopes. The detailed band structure and their variation with neutron number N of the Os isotopes is presented empirically and in IBM-1.

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.

A strategy for designing temperature-sensitive complexes based on ligand vibration rotation mode control

Copper(I) and 3,5-dimethyl-1,2,4-triazole ligands construct the isomers α-Cu(mdtz) and β-Cu(mdtz), respectively. In α-Cu(mdtz), the hexagonal ring structure composed of Cu(I) and N atoms restricts the vibrational rotation of the triazole ring structure and reduces the nonradiative transition, achieving a high internal quantum efficiency at room temperature and pressure (IQY = 72.3%). As for β-Cu(mdtz), the triazole ring can rotate back and forth along its own C2 axis within a certain angle. We investigated the comparison of the luminescence spectra of α-Cu(mdtz) and β-Cu(mdtz) at different temperatures, confirmed that the vibrational rotation of the triazole ring improved the sensitivity of the luminescence intensity and spectral broadening to the temperature response, especially at low temperatures. In addition, we found that the decay time of Cu(mdtz)s varies linearly with temperature in a certain temperature interval, which provides strategy for temperature measurement based on the luminescence lifetime. Besides, the non-porous structure of Cu(mdtz)s prevents oxygen from entering the structure and protects the luminescent center from oxygen, thus improving the accuracy of temperature measurement in atmospheric environments.

The localised response and filtering performance of centrifugal pendulum vibration absorbers allowing a rotational mobility

Rotating machines are often subjected to fluctuating torques, which causes rotor vibrations, early wear and noise pollution. These vibrations can be reduced using centrifugal pendulum vibration absorbers (CPVAs), which are passive devices made of several bodies (pendulums) oscillating along a given path and rotating relatively to a rotor. Previous studies showed that the dynamics of these devices is subjected to instabilities leading to a localisation of the motion of the pendulums. In this paper, the localised behaviour of a CPVA made of two pendulums allowed to rotate about their centre of mass is investigated. To this aim, a dynamical model based on an analytic perturbation method is established. The aim of this model is to highlight some special features of the localised response, such as the appearance of quasi-periodic regimes. The case studies showed that in some special cases, localisation can improve the filtering efficiency as compared to a unison motion. The validity of the model was confirmed through a comparison with numerical resolutions of the system’s dynamics.

Experimental Detection of Lubrication Characteristics in a Solid–Liquid Two-Phase Flow Supported Bearing-Rotor System Using Vibration Monitoring Techniques

This work aims to investigate the friction and vibration behaviors of a liquid–solid two-phase flow supported bearing-rotor system for the early monitoring and assessing of oil contamination resulting from externally ingested particles. Based on a Jeffcott rotor test rig, the lubricating oil in journal bearing was mixed with micron-scale silica particles of different sizes and concentrations. The vibration monitoring techniques utilizing eddy current, photoelectric, and piezoelectric sensors were conducted to detect the rotor displacement amplitude and bearing acceleration online. According to the quantitative evaluation, the vibration frequency spectrum, shaft trajectory, and the bearing surface characteristics were analyzed and classified at different conditions of particle parameters. Furthermore, the lubricating mechanism at bearing interface which possesses a strong interactive coupling effect with rotor vibration was deduced and illustrated. The results showed that although the sizes of ingested micron particles were less than the minimum oil-film thickness, they usually exhibited detrimental effects on the flow stability and fluid support. As the particle size or concentration increased, the interaction between particles and bearing surfaces led to the burrs in time-domain waveform, reverse displacements in rotor orbit, higher frequency harmonics in vibration spectrum, and the scratches on the bearing surface. The occurrence of continuous three-body friction could induce misalignment, blockage, oil starvation, and rub-impact fault. Furthermore, the detectability of particle contamination and damage microstructure of bearing surface was described for reference.

Low-Temperature Cavity-Enhanced Spectroscopy with a Diode Laser: Vibration–Rotation Absorption of CO (3ν) at 80 K and CH3C≡C–H (2ν1) at 165 K

A rotational resolution cavity-enhanced absorption spectroscopy (CEAS) technique is presented for infrared (IR) absorption studies at temperatures between 77 and 300 K. The cavity consists of an aluminum tube with two highly reflecting near-IR mirrors at each end. The cavity is attached to the cold head of a liquid nitrogen cryostat inside a vacuum chamber. In this way, all the cavity components are the temperature of the cold head. The spectra are obtained with a tunable diode laser and lock-in detection. The laser is modulated with an electro-optic modulator and coupled to the optical cavity. To illustrate the use of the technique, the vibrational–rotational overtone transitions (υ = 0→3) of carbon monoxide at 295 and 80 K and the acetylenic C–H (υ = 0→2) bond of CH3C≡C–H at 293 and 165 K are obtained. Temperatures are obtained with a Boltzmann distribution calculation that involves rotational intensities and energies from the spectra. Spectroscopic constants agree with previous determinations using other methods. An average of signals over the entire range of the absorption produces a rotational intensity distribution with some deviations. The calculated temperature based on the Boltzmann distribution is in very good agreement with the temperature measured with a silicon temperature sensor attached to the cell. Comparison with other experimental approaches to CEAS and the importance of the technique for applications in astrochemistry are discussed.

Chaotic Effect-Based Array Duffing Systems with Improved Nonlinear Restoring Force for Weak Signal Detection in Dynamic MWD.

In the process of dynamic Measurement While Drilling (MWD), the strong vibration and rapid rotation of the Bottom Hole Assembly (BHA) lead to multi-frequency and high-amplitude noise interference in the attitude measurement signal. The weak original signal and extremely low signal-to-noise ratio (SNR) are always the technical difficulties of dynamic MWD. To solve this problem, this paper uses the chaotic effect of the Duffing system, which takes the expression (-x3 + x5) as a nonlinear restoring force to detect the weak characteristic signal of downhole dynamic MWD. First of all, in order to meet the limit condition of the chaotic phase transition of the system output, the frequency value of the characteristic signal is reconstructed and transformed based on the variable scale theory. Then, in order to solve the influence of the initial phase of the characteristic signal on the detection accuracy, a detection model based on the array Duffing system is presented, and a frequency-detection scheme with all-phase coverage is given. Finally, another array Duffing system is designed for the parameter estimation of the characteristic signal. The critical value of chaotic phase transition is determined by adjusting the amplitude of the driving signal of the array Duffing system, and then the amplitude and phase parameters of the characteristic signal are synchronously estimated. The experimental results show that the proposed method can effectively extract the weak characteristic signal within the strong noise, and the SNR of the characteristic signal can be as low as -21 dB. Through the attitude calculation for the extracted characteristic signal, it can be seen that the proposed method can improve the accuracy of the inclination of the drilling tool significantly, which proves the feasibility and effectiveness of the method proposed in this paper.

Cross-infection risk assessment in dental clinic: Numerical investigation of emitted droplets during different atomization procedures

Cross-infection risk induced by the emitted droplets and bioaerosols during dental procedures has challenged service providers and patients alike. The present study aims to investigate the transmission mechanism of emitted droplets during the dental atomization procedures: vibration ultrasonic scaling (vUS) and rotation high-speed drilling (rHSD) and propose the risk assessment. Computational fluid dynamics (CFD) simulation was performed, and the experimentally recorded droplet velocity and diameter distribution during the atomization procedures were defined as initial boundary conditions. The droplet transmission in the dental clinic was analyzed from the final fate (deposition, suspension, and escape) and fallow time (FT) of emitted droplets. The results revealed that the diameter threshold for the droplet deposition and suspension was 60μm, and the fraction of deposited droplets would be stable at 79.5% for rHSD and 85% for vUS. The primary contamination distance was generally within 0.28 m and 0.4 m from the treatment position for the atomization procedures of rHSD and vUS, respectively. An increment of about 2% in the fraction of escaped droplets was noted when conducting the rHSD. The median of estimated FT for the atomization procedure of rHSD, 34 min, was longer than that of vUS, 30.6 min. In general, cross-infection risk during rHSD can be regarded as “higher” than vUS. The contribution of the present study can serve as guidance to decrease the cross-infection risk in dental clinics.

Study on the Vibration Characteristics of Yaw Gear System for Large-Capacity Offshore Wind Turbine

Vibration and noise must be considered to maximize the efficiency of a yaw system and reduce the fatigue load acting on a wind turbine. This study investigated a method for analyzing yaw-system vibration based on the change in the load-duration distribution (LDD). A substructure synthesis method was combined with a planetary gear train rotational vibration model and finite element models of the housing and carriers. For the vibration excitation sources, the mass imbalance, gear mesh frequency, and bearing defect frequency were considered, and a critical speed analysis was performed. The analysis results showed that the critical speed did not occur within the operating speed range, but a defect occurred in the bearing of the first-stage planetary gear system. It was found that the bearing stiffness and first natural frequency increased with the LDD load. In addition, no vibration occurred in the operating speed range under any of the LDD loads. Because the rolling bearing stiffness changed with the LDD, it was necessary to consider the LDD when analyzing the wind turbine vibration.

Coupled responses of the flow-induced vibration and flow-induced rotation of a rigid cylinder-plate body

In this study, coupled responses of flow-induced vibration and rotation for an elastically mounted cylinder-plate body are numerically investigated at a low Reynolds number of 120. A wide vibrational reduced velocity range of Uy = 3–18 under four rotational reduced velocities Uθ = 5, 8, 12, and 18 are considered. The non-bifurcation responses, bifurcation only in rotation responses, and bifurcation in both vibration and rotation responses are identified. Typical vortex-induced vibration (VIV) responses are recognized when considering the passive rotations, different from the full interactions between VIV and galloping for the vibration-only case. As Uθ increases, the peak vibration amplitudes increase, the onset Uy of the lock-in region becomes larger, and the lock-in region is wider. The phase angles of displacements versus lift coefficients experience a jump from 0° to 180° in the lock-in region, and the larger the Uθ, the wider the Uy range of phase jump. Whether the instantaneous posture of the cylinder-plate body is streamlined or not is determined by oscillation amplitudes and phase differences between displacements versus rotation angles. Streamlined profiles can be achieved under small oscillation amplitudes or when the phase angles are nearly 90°. The 2S (two isolated vortices) vortex shedding mode dominates the initial and desynchronization branch, while the 2P (two pairs of vortices), 2S* (two isolated vortices with tendency to split), and 2T (two triplets of vortices) modes appear in the lock-in region. After the symmetry-breaking bifurcation, the reattachment behavior becomes simpler and the length of the recirculation region is significantly increased, as compared with those in non-bifurcation region. With the above study, a new method of improving energy harvesting from flow-induced vibration, by incorporating passive rotations simultaneously, is first introduced. It is found that passive rotations can enhance the vibration responses and thus lead to the increased output power and energy transfer ratio, although they make less contributions to the total power. Generally, this mechanical system presents a promising opportunity for energy harvesting through flow-induced vibration.

A snap-through vibration-rotation modulation mechanism for high-performance low frequency energy harvester

Ambient low frequency (LF) vibrations are ubiquitous but their efficient utilization is still an open issue. To tackle this problem, this paper reports an ingenious vibration–rotation (V-R) modulation mechanism that is realized by introducing a reset spring and a pair of magnets to the conventional rack-and-pinion mechanism. By taking advantage of the magnets-enabled snap-through dynamics, the V-R mechanism can convert LF-vibrations to fast rotation. Under a pressed depth of 10 mm and trigger frequency of 2.0 Hz, a high rotation speed of 1230 rpm can be achieved by the snap-through V-R mechanism in combination with a pawl-ratchet mechanism, which is 1.4 times higher than that enabled by the linear counterpart. A rotor-based vibration energy harvester (R-VEH) designed with the snap-through V-R mechanism can generate high voltage of 4.3 V and large power of 10.8 mW as excited at 2.5 Hz. The snap-through R-VEH can also sustain the continuous work of a hygrothermograph by tapping the irregular LF-vibration of a treadmill (even with a small amplitude of roughly 2.5 mm). The snap-through R-VEH is thus a potential technology for the efficient harvesting of pervasive LF-vibrations toward self-driven sensing systems.

Random response of a two-degree-of-freedom rotational vibration energy harvester

Random response of a two-degree-of-freedom rotational vibration energy harvester

Stability control of high-speed magnetic levitation turbomolecular pumps with shock-excited disturbance

The disturbance suppression of magnetic levitation turbomolecular pumps is a critical problem in industrial applications. This work addresses the stability control of high-speed magnetic levitation turbomolecular pumps with shock-excited disturbance. A disturbance suppression method based on improved linear extended state observer is proposed to attenuate the impact of external low-frequency disturbing force on a magnetic levitation turbomolecular pump. Firstly, a linear extended state observer of an active magnetic bearing is obtained by analyzing the rotor dynamics model. Then, the detailed descriptions of external disturbance suppression method using linear extended state observers and adaptive notch filters are discussed for the system. The boundary condition of the parameters of the improved linear extended state observer is determined. The root loci of the closed-loop system with improved linear extended state observers is also investigated. Finally, simulation and experimental results on a magnetic levitation turbomolecular pump show the applicability of the proposed method. The results show that the proposed method can attenuate the rotor vibration displacement caused by impact by 46.9%.