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The low-pressure rotor system of an aircraft engine includes a fan rotor and a low-pressure turbine rotor, which are connected and fixed by a gear coupling. The existence of machining errors and assembly errors can cause rotor assembly misalignment, which is one of the important factors causing aircraft engine failures. Based on the finite element matrix set theory, this paper establishes a dynamic model of the aircraft engine rotor system, including the climbing maneuver load, nonlinear contact force of bearings, oil film force of SFDs, gravity field, additional force caused by coupling misalignment, and rotor misalignment imbalance force, considering the climbing maneuver load. Using Newmark-β algorithm to solve the misaligned rotor system model with SFDs. The influence of misalignment stiffness, clearance of the oil film, and bearing clearance on the motion state of the rotor system were analyzed in detail through bifurcation diagrams, axis trajectory diagrams, and frequency spectra. And analyze and cross compare the effects of three influencing factors on the system motion state under different maneuvering load environments. Through comparative analysis, it was found that among these three influencing factors, the misalignment stiffness of the sleeve coupling has the smallest effect on the system's motion state, but an appropriate intermediate value needs to be selected. The effect of rolling bearing clearance on the system's motion state is small and regular, while the impact of oil film clearance on the system's motion state is large and complex. The research results of this paper can provide theoretical support for parameter selection in the simulation and design of dynamic phenomena with misalignment faults in aircraft engines during maneuvering flight. [ABSTRACT FROM AUTHOR]

The performance of a rotor system is influenced by various design parameters that are neither precise nor constant. Uncertainties in rotor operation arise from factors such as assembly errors, material defects, and wear. To obtain more reliable analytical results, it is essential to consider these uncertainties when evaluating rotor performance. In this paper, the Chebyshev interval method is employed to quantify the uncertainty in the steady-state response of the rotor system. To address the challenges of high-dimensional integration, an innovative sparse-grid integration method is introduced and demonstrated using a rotor tester. The effects of support stiffness, mass imbalance, and uncertainties in the installation phase angle on the steady-state response of the rotor system are analyzed individually, along with a comprehensive assessment of their combined effects. When compared to the Monte Carlo simulation (MCS) method and the full tensor product grid (FTG) method, the proposed method requires only 68% of the computational cost associated with MCS, while maintaining calculation accuracy. Additionally, sparse-grid integration reduces the computational cost by approximately 95.87% compared to the FTG method. [ABSTRACT FROM AUTHOR]

Rotor system unbalance is one of the most important factors that affects the operating accuracy and stability in aerospace engineering. The extraction and identification of unbalanced features is the premise for the dynamic balance of rotor system. In order to accurately identify the unbalanced vibration feature, based on the fused cross‐correlation fast Fourier transform (FC‐CFFT) method, an unbalanced feature extraction method of the rotor system is proposed. The convolution window weighs the data of the vibration sequence and carries out delay processing. Through spectrum calculation, the phase information of the vibration signal is obtained. And the amplitude information of the vibration feature can be acquired through cross‐correlation calculation. The unbalanced features of the rotor system vibration signals are identified under different working conditions through simulation and experiment. The results show that this method is more accurate than FFT, the cross‐power method, and the sine‐approximation method in extracting different unbalanced vibration features of the rotor system. The extraction accuracy of unbalanced feature phase and amplitude reaches 98.61% and 97.27%, respectively. After the unbalanced feature is extracted, the dynamic balance experiment can be carried out. The unbalanced feature is used for dynamic balance compensation. In this way, the average amplitude decreased by 76.35%. The high accuracy of the FC‐CFFT method for extracting the unbalanced feature has been verified. This research provides a theoretical foundation for the vibration signal processing and dynamic balance control of the rotor system. [ABSTRACT FROM AUTHOR]

When it comes to practical engineering, there is a high likelihood of shafts developing slant cracks due to torque transmission. These cracks exhibit breathing characteristics, repeatedly opening and closing under gravity and radial forces. To diagnose rotor systems with breathing slant cracks, the nonlinear output frequency response functions (NOFRFs) method is introduced. Firstly, a dynamic model of rotor systems with breathing slant cracks is established, and the system's frequency spectra are obtained by solving the model with different crack angles, depths, and positions. Secondly, the NOFRFs values at different orders are derived based on the NOFRFs theory. The simulation results display increased nonlinear characteristics with crack angle and depth. The system's nonlinear characteristics are stronger when cracks are closer to the disk. The G 3 (j ω F) ¯ value for the first-order is sensitive to crack angles, the G 4 (j 2 ω F) ¯ value for the second-order is sensitive to crack depths, and the G 4 (j 4 ω F) ¯ value for the fourth-order is sensitive to crack positions. As a result, the NOFRFs response at different orders can detect variations in angles, depths, and positions of the breathing slant crack. Finally, experiments are conducted on a rotor system with breathing slant cracks, and the results match those of the simulation, indicating that the NOFRFs method is feasible for identifying breathing slant cracks. [ABSTRACT FROM AUTHOR]

Aiming at the difficulty of feature extraction of rotor vibration signals under strong noise, a fault diagnosis method based on mesh search variational mode decomposition (VMD) parameters combined with fine composite multiscale spread entropy (RCMDE-Relieve-F) is proposed. Based on time-domain energy entropy, kurtosis and Pearson correlation coefficient, a new index grid was formed to search VMD to decompose the optimal K of the original signal, a value was reconstructed, RCMDE in the reconstructed signal was extracted as the characteristic value, and input was filtered into the generalized regression neural network (GRNN) for training and fault pattern recognition using Relief-F dimensionality reduction. The effectiveness of VMD noise reduction parameter selection was verified by numerical simulation and comparison with other decomposition methods. Moreover, the fault simulation experiment results showed that compared with other algorithm models, the mesh search-optimized VMD combined with the RCMDE-Relief-F-GRNN method could effectively filter noise with accuracy of 96 %. [ABSTRACT FROM AUTHOR]

Impact loads affect the operational performance and safety life of rolling equipment's connecting-shaft rotor system, even causing faults and accidents. Therefore, recognizing and investigating impact loads is of great significance. Hence, a load recognition method based on motor current information is proposed in this paper to recognize impact loads on the connecting-shaft rotor system. First, the fast Fourier transform is used to obtain the frequency domain information for the motor's current response signal from the rotor system load recognition test. Consequently, the required load response information can be presented more clearly using the singular value decomposition method to remove the power frequency components in the current signal. Then, wavelet packet decomposition is performed on the signal to generate energy analysis feature vectors. A qualitative recognition of the impact load on the system is achieved by learning vector quantization neural networks; the resulting load recognition results are good. These findings indicate that using the motor current as the analysis signal can solve the problem of the difficult layout for traditional vibration sensors in rolling sites. The preprocessing and recognition method of the current response signal can recognize the impact load, confirming the applicability and feasibility of the proposed method. [ABSTRACT FROM AUTHOR]

Various processes take place in rotor systems with tilting pad bearings. It is important not only to control but also to manage these processes. Due to the instability of the oil film layer in a bearing with inclined pads, oil whirl/whip can occur. Such whirl/whip destabilize the operation of the rotor system. Additional elastic elements between the tilt pads suppress oil whirl/whip and thus reduce rotor vibration excitation. By identifying the working zones of such bearings where oil whirl and whip occur, the problems of rotor rotation instability can be solved. In order to determine the effectiveness of the elastic elements between the tilting pads, research was conducted. A special stand with diagnostic equipment was used for the tests. The clearance between the rotor and the bearing was 50 μm. During the research, the rotor rotation speed was varied from 0 to 5000 rpm. After conducting the research, stable and unstable rotor working zones were determined (Zone I: 0 to 1938 rpm; Zone II: 1938–3923 rpm; Zone III: 3923–5000 rpm). Based on the obtained research results, it is possible to control the working process of the rotor system. [ABSTRACT FROM AUTHOR]

Rotating machinery is an important component of mechanical equipment, and misaligned rotor systems are a key factor leading to equipment failures. If there is a misalignment fault during operation, it may have various adverse effects on the stable operation of mechanical equipment, such as causing dynamic and static friction between the rotor and stator, bearing friction damage, shaft bending deformation, oil film oscillation, vibration, etc., all of which may seriously interfere with the stable operation of mechanical equipment. Studying the mechanism and vibration characteristics of misalignment faults in rotor systems is particularly crucial for accurately judging and mastering the operating conditions of the rotor system. This article focuses on the parallel misalignment fault of the rotor system of a hydroelectric generator set and the collision friction coupling fault between the rotor system of the generator set. Based on nonlinear rotor dynamics theory and the motion mechanism of parallel misalignment faults, a nonlinear dynamic model of the rotor system of a hydroelectric generator set is constructed, which considers the influence of parallel misalignment and collision friction coupling faults. The model explores the nonlinear dynamic performance of the generator rotor system under multiple parameter changes such as unit speed, eccentricity, and parallel misalignment. [ABSTRACT FROM AUTHOR]

Sealing aerodynamic characteristics are affected by the seal structure, and thus the stability of the rotor system is affected too. A 1.5-stage, three-dimensional, full-cycle model of the high-pressure cylinder of a 1000 MW steam turbine was established. The high eccentricity whirl of the rotor was realized using mesh deformation technology and the multi-frequency whirl model. The nonlinear steam-flow-exciting force of different sealing structures was obtained using CFD/FLUENT, and the motion equations with a nonlinear steam-exciting force were solved using the Runge–Kutta method. The motion characteristics and stability of the rotor system with different sealing structures were obtained. The results show that there are "inverted bifurcation" and "double bifurcation" phenomena in the bifurcation diagrams of different tooth numbers, boss numbers, and tooth lengths, and a 1/2 power frequency of different sealing structures goes through the process of weakening, disappearing, reproducing, and evolving into a 1/3 power frequency and a 2/3 power frequency. With the increasing load, the steam-flow-exciting force becomes stronger, and the multi-frequency vibration and dense frequency phenomena are significant. Under some load conditions, the change curves of three kinds of teeth in 1/3 and 2/3 power frequency vibrations are highly similar, and the tooth number has little influence on the system stability. Under the high load condition, with the boss number increasing, the chaos phenomenon is weakened. Increasing the tooth length is beneficial to the stability of the rotor. [ABSTRACT FROM AUTHOR]

During the operation of the rotor system,parts may fall and loose,resulting in rubbing between the external object and the rotor shaft.To solve this problem,a finite element model of rotor systems with coupling fault was established by considering the case that disc⁃shaft loosening and rubbing occur simultaneously.Ansys was employed to simulate the rotor system.The influence of the looseness on the vibration characteristics of the rotor system was analyzed.Experiments were carried out to verify the simulation results.The results show that the time⁃domain waveform of the rotor system changes periodically,and the spectrogram mainly contains the first harmonic component.With the aggravation of the looseness,high frequency components gradually appear in the spectrum.The initial value of the speed difference of the disc⁃shaft in the start⁃up phase gradually increases with the aggravation of the loosening.The vibration amplitude of the disc center trajectory in the vertical direction also increases with the aggravation of the looseness,and the orbit shape becomes more complex.Due to the influence of the rubbing,the vibration in the vertical direction is obviously suppressed,and its amplitude is smaller than that in the horizontal direction.The research results have very important reference value for the study on dynamic characteristics of rotor systems with coupling faults.

[Objective] To improve the design efficiency of the mechanical structure of the rotor system of a rubber roller husker. [Methods] An auxiliary calculation system for the rotor system design parameters of a rubber roller husker （RRHRSPD） that can be independently installed and operated under the Windows system was developed using VB and Matlab platforms. Based on the equivalent design method and the traditional mechanical design method, the coupling relationships among the technological parameters, dynamic parameters and structural parameters of the husker were established, and the calculation principle of the structural parameters of the rotor system was also explored. VB was used to develop the software operation interface and to quickly call the Matlab dynamic link library, which formed the core computing mechanism of the system, and the system was packaged and released. [Results] A set of auxiliary calculation system for structural parameters of the rotor system of rubber roller husker was developed. [Conclusion] The calculation results of the system are accurate and reliable, which can be used not only for the design and calculation of the rotor system structure of the rubber roller husker, but also for the virtual test platform for the performance analysis of the rubber roller husker.

The operational state of a rotor system directly affects its working efficiency, and the axis trajectory can accurately characterize this state. Therefore, a method for extracting axis motion trajectory characteristics based on distance sequence representation is established. First, the axis trajectory sample signal is constructed from the original vibration displacement signal. Singular value decomposition (SVD) is performed on the sample signal to obtain effective components, resulting in a purified and denoised axis motion trajectory signal. Next, the axis motion trajectory signal is centralized and normalized. Feature extraction is then performed on the axis motion trajectory signal. Based on the different curvatures of various regions in the axis motion trajectory graph, data points are adaptively selected. The distances between the selected data points and a unique fixed point are calculated in the two-dimensional plane, resulting in a feature signal that characterizes the axis motion trajectory graph. This completes the extraction of the axis motion trajectory characteristics. Different rotational speeds, additional weights, and changes in rotor arrangement types are applied to a multi-disk rotor test rig to obtain measured data for various unbalanced states, validating this method. The results show that this method effectively characterizes the axis motion trajectory with strong generality. [ABSTRACT FROM AUTHOR]

The blade fracture of horizontal centrifugal pump will not only affect the hydraulic performance of the pump, but also affect the safety and stability of the whole unit. In this paper, for horizontal centrifugal pumps, five single-blade fracture schemes are designed and numerical simulations are carried out under different operating conditions. The results show that with the increase of fracture size, the influence on the hydraulic characteristics of the pump shows a decreasing trend, and it will also affect the turbulent kinetic energy distribution near the impeller inlet, so that the internal flow becomes complex and the flow loss increases. The radial force on the impeller changes periodically, and its magnitude shows a nonlinear decreasing change with the increase of the fracture size. The pressure pulsation analysis of several monitoring points in the worm shell shows that as the fracture size increases, the amplitude of the lobe frequency slowly rises, and the shaft frequency, which is second only to the lobe frequency, becomes higher and higher and begins to dominate. A study of the rotor system shows that the maximum deformation of the impeller occurs at the edge of the impeller cover and the maximum equivalent stress occurs at the blade exit; blade fracture causes a significant reduction in the latter third-order intrinsic frequency. [ABSTRACT FROM AUTHOR]

The nonlinear stiffness of a structure results in complex nonlinear dynamic behaviors and bifurcations of rotor systems. However, there still lacks of comprehensive studies on the bifurcation-induced motion to chaos of the nonlinear system. This study investigated the energy transfer during the motion evolution to chaos around bifurcations. In this paper, a flexible rotor system with nonlinear stiffness is established and the nonlinear responses under different parameter excitations are studied. We construct the energy trajectory in energy space and propose a bifurcation detection method based on generalized energy transfer for studying the evolution of motion cascades to chaos. The induction of period-doubling and period-halving bifurcation is revealed through the energy trajectory. The stability domains of the rotor system in different parameter planes are determined based on the Lyapunov stability criterion. A nonlinear rotor test platform is built and speed-up experiments are carried out to verify the proposed bifurcation detection method based on generalized energy transfer. These results indicate that the energy transfer is consistent with the switching of bifurcations. The sudden shift and fluctuation in the generalized energy amplitude correspond to period-doubling bifurcation and chaos, respectively. The generalized energy curves reveal the period-halving bifurcation, which cannot be observed in the speed-up test. This research and proposed method have potential for application in condition monitoring and bifurcation recognition during the operation of rotating machinery. [ABSTRACT FROM AUTHOR]

Copyright of Bearing is the property of Bearing Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Bearing is the property of Bearing Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Mechanical Strength / Jixie Qiangdu is the property of Zhengzhou Research Institute of Mechanical Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In order to solve the problem of imbalance of internal forces in the system caused by the gravity force of the eccentric wheel and the orbiting scroll close to the drive bearing and the rotational inertia force during the operation of the electric scroll compressor, a dynamic model of the rotor system of the scroll compressor that takes into account the effect of the gas force was established using the multibody dynamics software ADAMS/View 2020. Dynamic simulation analysis of the rotor system is carried out, focusing on the force of the drive bearing; a parametric optimization method is adopted to optimize the position of the center-of-mass coordinates of the eccentric wheel of the relevant components, and the relevant parameters are derived after optimization. The results show that by adjusting the center-of-mass position of the eccentric wheel it is possible to optimize the unbalance force and unbalance moment of the main shaft drive system; compared with the pre-optimization, the force fluctuation ranges of the drive bearing in the horizontal and vertical directions are reduced, the peak value is reduced by 18%, and the impact force of the drive bearing during the initial period of compressor operation is effectively relieved. Through optimization calculation, the vibration and noise of the system are reduced, the operating stability of the scroll compressor is improved, and analytical methods and theoretical guidance are provided for the design and prediction of the dynamic behavior of the scroll compressors. [ABSTRACT FROM AUTHOR]

Along with the rotating machinery advances toward high speeds, the significance of the excitation force of the seal fluid in the rotor system is growing, which can cause serious accidents. Most of the previous research on rotors in rotating machinery has predominantly focused on the effects of misalignment in couplings. In this article, a novel model is proposed, introducing an analytical approach that combines both internal friction in couplings and loosening support faults. Additionally, an analysis and discussion of the vibration characteristics of the rotating system under the influence of internal friction are presented. This method allows for a more comprehensive assessment of the performance of rotors in engineering applications. Assuming that the left support of the rotor is loose, this model focused on how various factors such as rotor speeds, eccentricity, seal disc mass, and left-end support mass affect the labyrinth seal rotor system's dynamic characteristics. Based on the findings, The emergence of internal friction forces advances the chaos of the rotor. It seems that as the rotating speed increases, there will be a small frequency range, resulting in fluid oscillation, and the system stability will be reduced at this time. The improvement in the seal disc's quality has minimal impact on the stability of the left journal, but it will reduce the stability of the seal disc. The increase in the mass of the left end support will increase the stability of the movement at the left journal and reduce the stability of the movement at the seal disc. [ABSTRACT FROM AUTHOR]

Copyright of Food & Machinery is the property of Food & Machinery Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This paper proposes a novel cylindrical conformal contact model for the large-diameter bearing with small clearance to its housing in aero-engines. Since the clearance between them is usually below one-thousandth of the bearing nominal diameter, Hertz's law is not feasible in this case. The proposed contact model accounts for the surface contact condition and more geometric parameters of the bearing-housing component to obtain more accurate prediction results, which are validated by the finite element method (FEM) results. Based on this novel contact model, the vibration response of a single-disk rotor introduced by Ishida et al. is investigated. Numerical results are in good agreement with experimental results by Ishida et al. Influences of several critical parameters on the vibration responses are also studied. Furthermore, a complex dual-rotor system whose front bearing has a clearance stop between the outer ring and housing is analyzed with the proposed model. Good agreement is shown in the comparison between numerical and experimental results, which shows the feasibility of the proposed model in the contact simulation of large-diameter bearings with a small clearance. The results show that periodic collision between the bearing and housing could lead to self-excited vibrations. A natural frequency component in frequency-domain responses is an important indicator for the occurrence of self-excited vibration. This work provides a reference for the fault diagnosis of practical rotor-bearing systems with bearing clearance. [ABSTRACT FROM AUTHOR]

Copyright of Electric Machines & Control / Dianji Yu Kongzhi Xuebao is the property of Electric Machines & Control and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The twin rotor aerodynamic system (TRAS) reflects the dynamics of vertical take-off rotor systems. TRAS considers the coupling effect and gyroscopic disturbance torque as unwanted signals. For safe and reliable TRAS operation, proper control input is vital, along with fast fault indication. This paper addresses the output sensor fault detection problem in the linear model of TRAS subjected to l2-norm bounded disturbance. A robust design of an observer is formulated as H-/H∞ optimization problem to maximize the sensitivity/robustness criterion. The approach minimizes the disturbance effect on the residual signal, which leads to successful fault detection. Furthermore, a linear quadratic regulator-based state feedback controller is proposed to meet the system's desired transient response requirement. The incorporation of an observer-based residual generator for fault detection along with the state-feedback controller differs the current work from the existing work. Successful fault detection in the output sensor of TRAS depicts the good performance of the proposed observer.