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Electrically assisted turbocharging (EAT) technology is an important technical means to effectively solve the problems of insufficient intake air and poor transient response of traditional turbocharged engines at low speed or acceleration, and to realize the electrification of marine internal combustion engine power system. In the EAT design stage, the original rotor model of a marine turbocharger was established and verified. Subsequently, the EAT rotor dynamics design and analysis were carried out, and the influence of the unbalanced phase and external clearance on rotor vibration was discussed. The results show that when the external clearance is small, extensive sub-synchronous vibration occurs and bifurcation occurs at high speed. When the external clearance is large, the sub-synchronous vibration component almost disappears but high synchronous vibration occurs at a high speed. At the same time, the shaft is significantly affected by the gravity load at low speeds, and the rotor makes a balanced motion on the critical limit cycle at high speed. In order to minimize the vibration and noise of the same type of EAT, it is recommended to control the outer clearance of the EAT bearing in the range of 0.30–0.36mm. The research content provides a reference for the dynamic design and analysis of the EAT, which effectively helps the development of the original engine of the ship electric auxiliary turbocharger and improves the operation stability of the EAT. [ABSTRACT FROM AUTHOR]

Rotor systems are widely used in industrial power generation and propulsion. Once the nonlinear contact stiffness and oil film force are taken into account, the dynamics and stability of rotor systems become quite complex, often accompanied by super-harmonic and chaotic motions. Furthermore, conventional methods face limitations in real-time detection of the bifurcations and complex nonlinear motions. This research investigates the bifurcations and stability induced by nonlinear factors in a rotor-bearing system from an energy perspective. Dynamic equations of a rotor-bearing system considering cubic term stiffness are established, the steady responses are obtained by the fourth-order Runge–Kutta method. The relationship between the bifurcations and energy transfers is analyzed numerically, the proposed stability criterion is validated by comparing the Lyapunov exponents. The bistable phenomenon of period-3 m (m = 0 , 1) motion is discussed in terms of numerical results and experiments which corresponds to the asymmetric jumps of the generalized energy. It is found that bifurcations and unstable motions of the nonlinear system can be captured accurately by detecting the energy transfers, the proposed generalized energy curve exhibits more detailed information than the conventional speed-up curve. These findings provide a new perspective on studying bifurcations and stability of rotating systems, which can be further applied in the condition monitoring, stability prediction as well as the design of nonlinear energy sink, representing significant progress in converting theory into engineering applications for rotor systems. [ABSTRACT FROM AUTHOR]

This study presents the development and evaluation of a spin test rig for high-speed rotating components. The innovation of this study is using a discrete model to determine dynamic positioning during the preliminary design phase based on vibration characteristics. The primary aim is to manage vibrations and alternating stress effects from rotor dynamics to prevent issues such as crack propagation or bursts before achieving desired speeds. MATLAB 2023b Simulink-based tool was developed, which played a role in providing the design of bearing support regions and stiffness values. The system underwent rigorous validation through structural, modal, and harmonic finite element analyses. Testing showed a maximum deviation of 4.2% for 10 kg specimen and 4.85% for 4 kg specimen between Simulink predictions and actual data, due to factors such as contact and bearing damping. For the 10 kg specimen, the maximum equivalent stress was 314.92 MPa with an alternating stress of 64.87 MPa at 0.5% damping ratio, representing 37.27% of the yield limit. For the 4 kg specimen, the maximum equivalent stress was 513 MPa with alternating stress below 40 MPa at 3% damping ratio, corresponding to 54.32% of the yield limit. This research enhances the reliability and performance of high-speed rotating machinery. [ABSTRACT FROM AUTHOR]

The "Virtual Rotor Kit (VRK) Project" is a lightweight and standalone application developed in response to the challenges posed by the COVID-19 outbreak in the field of rotating machinery dynamics. This alternative emulates a rotor test rig, enabling virtual balancing tests on a single-plane rotor and offering students a comprehensive learning experience that simulates on-site balancing. The Virtual Rotor Kit utilizes a three-dimensional model based on a well-known rotor test rig widely used in educational and research settings. To simulate the dynamics of the rotor test rig, the application employs PyChrono, a dedicated Python library that wraps Chrono, a validated open-source multi-physics simulation engine. A detailed usability assessment involving 41 senior mechanical engineering students yielded promising results, indicating the Virtual Rotor Kit's potential to enhance comprehension of vibration phenomena in unbalanced rotating machines. Despite revealing certain issues related to the graphical user interface and the application's execution time, three defined achievement indicators demonstrated positive outcomes for a virtual balancing laboratory experience using the Virtual Rotor Kit application. By focusing on the dynamic behavior of a rotor test rig instead of simulating a specific laboratory experience, the application offers instructors greater flexibility in developing learning experiences. Unlike other virtual testbeds, the Virtual Rotor Kit allows students to conduct both steady-state and transient experiments, offering a comprehensive understanding of rotating machinery dynamics. Additionally, the application is distributed under the BSD-3 license and can serve as a complement to on-site laboratory experiences. The results presented in this study inspire further research and development to enhance its efficacy. [ABSTRACT FROM AUTHOR]

Copyright of Machine Tool & Hydraulics is the property of Guangzhou Mechanical Engineering Research Institute (GMERI) 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.)

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]

Rotor dynamics plays a crucial role in the performance and safety of rotating machinery, with disk position and unbalance significantly impacting system behavior. This study investigates the dynamic characteristics of two rotor configurations: a centrally mounted unbalanced disk (Rotor05un) and an off-center unbalanced disk (Rotor025un). Using numerical simulations and Monte Carlo analysis, we examined critical speeds and orbital patterns for both configurations. Probability distributions of shaft orbital positions revealed distinct patterns for each configuration. Quantile analysis revealed approximate linear trends for Rotor025un, suggesting higher system stiffness and more predictable behavior near critical speeds. Cross-sectional analyses of the orbits provided insights into the complex interactions between disk position, gyroscopic effects, and system natural frequencies. These findings provide valuable insights for rotor system design, particularly for applications with non-ideal mass distributions. The study goes beyond traditional critical speed analysis to examine orbital patterns and point on orbit occurrence from a probabilistic perspective. Based on the simulation of the orbits, an orbital is determined that allows the probability of the shaft occurring at the analyzed distance from the origin to be determined. The paper also offers insights into the complex interaction behavior of chosen rotor configurations and highlights the importance of considering disk position in predicting and optimizing rotor dynamic behavior, contributing to the development of more robust and efficient rotating machinery. [ABSTRACT FROM AUTHOR]

Damages in rotor systems have severe impact on their functionality, safety, running durability and their industrial productivity, which usually leads to unavoidable economical and human losses. Rotor systems are employed in extensive industrial applications such as jet engines, gas and steam turbines, heavy-duty pumps and compressors, drilling tools, and in other machineries. One of the major damages in such systems is the propagation of fatigue cracks. The heavy-duty and recurrent cyclic fatigue loading in rotor systems is one of the main factors leading to fatigue crack propagation. For the past few decades, numerous research have been conducted to study crack related damages and various methodologies were proposed or employed for damage detection in rotor systems. Therefore, the purpose of the present review article is to provide a thorough analysis and evaluation regarding the associated research related to the modeling aspects of rotor systems that are associated with various kinds of (rotor related) damages. Based on this review, it is observed that the crack modeling, especially with the breathing crack type in rotor systems, is still based on few primary models. Several researchers, based on different assumptions, have extended and modified such models to be more reliable for analysis. Moreover, the arising demand for early crack detection has led to utilization of various tools such as Fast Fourier transform, Hilbert Huang transform, wavelet transform, whirling analysis, energy methods, and the correlation between backward whirling and rotor faults etc. In addition, the significant impact of nonsynchronous whirl within resonance zones of rotor systems on post-resonance backward whirl, under various rotor related faults, is also highlighted in the present review. Therefore, the review provides an evaluation and comparison between several crack models and detection methodologies in rotor systems. Moreover, this review could help in identifying the gaps in modeling, simulation, and dynamical analysis of cracked rotor systems to establish robust research platform on cracked rotor systems. [ABSTRACT FROM AUTHOR]

The combination of a rotor and bearings plays a pivotal role in various industrial applications, including gas turbines, compressors, turbochargers, aircraft engines, and wind generators. Ensuring the structural integrity of the rotor-bearing assembly during static and dynamic conditions is most important, as any failure could lead to unpredictable losses. Due to their continuous operation, high-speed rotors are more susceptible to faults such as misalignment, bow, eccentricity, and cracks. Among these faults, cracks are the most predominant fault that affects the system’s reliability. Despite significant advancements in rotor dynamics, cracks still threaten the integrity and performance of the rotor-bearing assembly. This review paper aims to thoroughly review the challenges and issues associated with crack formation in high-speed rotor systems. Various crack detection methods are also explored using vibration signals obtained from the rotor-bearing unit and their associated processing techniques. This study also gives an extensive overview of different crack modelling and analysis techniques. Furthermore, a novel rotor-bearing model is modelled using the finite element method, and the numerical results obtained from this model are validated with the existing literature model. This review paper will serve as a valuable resource for researchers that offers insights into the latest advancements and emphasises the importance of crack detection for ensuring the reliability of high-speed rotor systems. [ABSTRACT FROM AUTHOR]

Copyright of Machine Tool & Hydraulics is the property of Guangzhou Mechanical Engineering Research Institute (GMERI) 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 the optimization of high-speed permanent magnet motors (HSPMMs), electromagnetic characteristics, rotor stress, rotor dynamics, and temperature characteristics must all be considered simultaneously, and there are numerous optimization parameters for both the stator and rotor. These factors pose significant challenges to the multiphysics optimization of HSPMMs. Therefore, this paper presents a multiphysics optimization process for the HSPMM of 60 kW 30,000 rpm by combining subspace strategy and sequential strategy to mitigate the issues of high training volume and mutual coupling. Ten optimization parameters of stator and rotor are determined firstly. Then, using finite element analysis of rotor stress and rotor dynamics, the range of values for critical parameters of the rotor is established. Next, in the electromagnetic optimization, the process is divided into rotor parameter subspace and stator parameter subspace according to the subspace optimization strategy. The temperature field is also checked based on the optimization results. Finally, a prototype is manufactured and the comprehensive performance is tested to validate the multiphysics optimization process. [ABSTRACT FROM AUTHOR]

Vibration analysis is crucial for studying rotor dynamics. The gas turbine rotor system is subjected to complex alternating loads during navigation, resulting in vibrations transmitted to the bearings that alter the system's dynamic characteristics. Based on the similarity law of the wave resistance test, a hull model was established. Beam sea and head sea tests were conducted in the towing pool to measure the acceleration response at the key positions. A finite element model of the turbine rotor system was established, and the test data were imported into the model after wavelet noise reduction and resampling to calculate the vibration response at the front and rear bearing points. The vibration responses transmitted to different locations and directions caused by beam sea and head sea conditions were analyzed. A comparison and analysis were conducted on the acceleration responses in various locations and directions under beam sea or head sea conditions. The equivalent von Mises stress distribution of the gas turbine rotor system under beam sea and head sea loads was obtained. The vibration transfer model was verified for accuracy and can be used to quickly analyze the vibration response of bearings under wave load transfer. This study provides a theoretical basis and reference for enhancing the stability of the gas turbine rotor system. [ABSTRACT FROM AUTHOR]

This paper examines the stability behavior of the nonlinear dynamical motion of a vibrating cart with two degrees of freedom (DOFs). Lagrange's equations are employed to establish the mechanical regulating system of the examined motion. The proposed approximate solutions (ASs) of this system are estimated through the use of the multiple-scales method (MSM). These solutions are considered novel as the MSM is being applied to a new dynamical model. Secular terms have been eliminated to meet the solvability criteria, and every instance of resonance that arises is categorized, where two of them are examined concurrently. Therefore, the modulation equations are developed based on the representations of the unknown complex function in polar form. The solutions for the steady state are calculated using the corresponding fixed points. The achieved solutions are displayed graphically to illustrate the impact of manipulating the system's parameters and are compared to the numerical solutions (NSs) of the system's original equations. This comparison shows a great deal of consistency with the numerical solution, which indicates the accuracy of the applied method. The nonlinear stability criteria of Routh–Hurwitz are employed to assess the stability and instability zones. The value of the proposed model is exhibited by its wide range of applications involving ship motion, swaying architecture, transportation infrastructure, and rotor dynamics. [ABSTRACT FROM AUTHOR]

Tall wind turbines are structures susceptible to high vibration levels, which may affect their optimal functioning and, ultimately, their overall structural stability. One alternative to minimize undesirable vibrations is to install vibration control devices. Various such devices are documented in the literature, with one noteworthy example being the tuned liquid column damper (TLCD), which is a vertical column filled with a liquid mounted at the top of the structure. When the main structure is dynamically excited, the appropriate TLCD vibrates out of phase with the structure, controlling its dynamic response. In this work, the nonlinear vibrations and control of a wind tower-nacelle-blade system subjected to an external harmonic force are studied. Nonlinear Euler–Bernoulli beam theory, together with the Rayleigh–Ritz method and Hamilton's principle, are used to obtain a set of nonlinear equations of motion, which are, in turn, solved by the Runge–Kutta method. A TLCD device located at the top of the tower is used to control vibrations. First, the effect of blade rotation on the natural frequencies of the system is studied. Second, resonance curves are obtained to study the effect of blade rotation and the frequency of the external force on the nonlinear vibrations of the tower, and the effect of the TLCD on vibration control is also analyzed. This study provides valuable perspectives on the dynamics of offshore wind turbines, contributing to the development of wind energy systems that are more robust and adaptable. [ABSTRACT FROM AUTHOR]

Polygonal wear affects driving safety and drastically shortens a wheel's life. This work establishes a wheel–rail coupled system's rotor dynamics model and a wheel polygonal wear model, taking into account the wheelset's flexibility, the effect of the wheelset rotation, and the initial wheel polygon. The energy approach is applied to study the stability of the self-excited vibration of a wheel–rail coupled system. The wheel polygonal wear generation and evolution mechanism is revealed, along with the impact of vehicle and rail characteristics on a wheel's high-order polygon. The findings demonstrate that wheel polygonal wear must occur in order for the wheel–rail system to experience self-excited vibration, which is brought on by a feedback mechanism dominated by creepage velocity. Additionally, the Hopf bifurcation characteristic is displayed by the wheel–rail system's self-excited vibration. Wheel polygonal wear is characterized by "fixed frequency and integer division", and the wheelset flexibility largely determines the fixed frequency of high-order polygonal wear, which is mostly unaffected by the suspension characteristics of the vehicle. By decreasing the tire load, increasing the wheelset's damping, and choosing a variable running speed, the progression of polygonal wear on wheels can be prevented. Future investigations on the suppression of wheel polygonal wear evolution can be guided by the results. [ABSTRACT FROM AUTHOR]

To enhance the static and dynamic performance of the grinding wheel spindle system, with the gear grinding machine (YKF2060) as the research object, a static mechanics model of the spindle system was established based on Castigliano's theorem, taking into account the equivalent effect of the triple-point contact ball bearing at the front end of the spindle. Meanwhile, based on the overall transfer matrix method, a dynamic model of the main spindle–eccentric shaft dual-rotor system was established, taking into account the effects of shear deformation and gyroscopic moments. On this basis, the effect of the spindle span, the front and rear overhang of the eccentric shaft, and the bearing stiffness on the static stiffness and first-order critical speed of the system was analyzed. Finally, static stiffness experiments, modal tests, and finite element simulation models were conducted to verify the static and dynamic models. The results show that the stiffness of the front outer bearing has the greatest influence on the static and dynamic performance of the system, while the stiffness of the rear inner bearing has the least influence. The relative errors of the static stiffness and the first two natural frequencies between static stiffness experiments, modal tests, and finite element simulation models are less than 10%, and the mode shapes match well. The established static and dynamic model can effectively reflect both the static and dynamic characteristics of the spindle system. [ABSTRACT FROM AUTHOR]

Sling configurations significantly influence the coupled dynamics of the helicopter with slung load system (HSLS), resulting in alterations to handling qualities (HQs) that remain inadequately understood. This study introduces a computer-oriented, generalized method for constructing the HSLS model with various sling configurations. To evaluate the HQs of 1-point, 2-point, and 4-point sling configurations, both the stability and response criteria outlined in ADS-33E and a newly proposed criterion for slung loads towards the updated ADS-33F were employed. Modal analysis was conducted to elucidate the coupled mechanisms of the HSLS under different sling configurations. The findings reveal that the dynamics of the main rotor can attenuate the lateral swing motions of the load in the 4-point sling configuration. While multiple-point sling configurations can enhance the helicopter's bandwidth, they also amplify the magnitude notch in the helicopter's response. Nevertheless, when a larger hook distance is employed, the notch frequency is sufficiently distant from the load swing bandwidth, leading to a reduced degradation in HQs. A 4-point configuration with lateral and longitudinal hook distances equal to twice the width and length of the slung load is recommended in practice to achieve sufficient swing stability and mitigate HQ degradation. [ABSTRACT FROM AUTHOR]

The high-temperature molten salt pump is the core equipment in the small modular molten salt reactor with media temperatures up to 700 °C. The cantilever ratio of the molten salt pump is usually large. Excessively large cantilever ratios cause increased deformations and rotational amplitudes at the impeller, thus affecting the operational stability of the main pump; small cantilever ratios cause heavy temperature gradients, thus affecting the structural integrity evaluation. This paper used numerical simulation methods to calculate and analyze the temperature field, stress, and structural integrity, optimized the pump shaft cantilever length of the original scheme based on structural integrity using the dichotomy method, and analyzed the rotor dynamics of the optimization results. The results of this study show that the thermal expansion load caused by the temperature difference has a significant mechanical effect on the structure; the first-order critical speed of the rotor system of the optimized schemes has been improved, and the amplitude of the unbalanced response has been significantly reduced, which not only improves the operational stability of the rotor, also contributes to the compact design of the main pump of a small modular molten salt reactor.

Wind and gusts can significantly impact the performance of rotors and turbines. The transient behavior of the rotor should be carefully examined to account for these effects. This paper investigates the unsteady aerodynamic characteristics of a rotor blade under different wind conditions, such as direction, speed, and angle. A 3D transient Computational Fluid Dynamics (CFD) simulation using the dynamic mesh technique is performed to analyze the rotor dynamics. The unsteady Reynolds-averaged Navier–Stokes (URANS) equations with the k-ω SST turbulence model are solved. The rotor blade used for this study is the U15XXL Combo KV29 industrial blade, which has not been numerically analyzed before. The results show that wind in the same direction as the rotation reduces the thrust more than lateral or opposite wind. Lateral wind with a speed lower than 5 m/s decreases the blade performance, but higher speeds increase it. Higher lateral wind speeds also cause two peaks in the torque curve, forming a butterfly wing shape in the polar torque plot and multiple extrema in the torque curve with increasing speed. The maximum thrust shifts slightly to the left with increasing lateral wind speed. The lateral angle does not affect the average thrust produced in one blade revolution but only causes a spatial shift. The thrust production decreases as the angle approaches the opposite direction of rotation. The motion amplitude decreases, and the curve becomes smoother as this angle increases. A nearly straight line similar to no side wind is observed at 60 and 90 degrees, which is attributed to the constant effective angle of attack during the rotation cycle. [ABSTRACT FROM AUTHOR]

This scientific research presents a modal analysis of the impact of honeycomb structures on rotors' dynamic characteristics. The natural frequencies and mode shapes of free vibration were determined employing the modal analysis. The impact hammer and the laser vibrometer were used for experimental modal analysis to provide valuable data using OptoGUI data acquisition software. The numerical modal analysis was performed by the finite element method using ANSYS software to validate the experimental results. The main objective of this study was to evaluate the influence of honeycomb structures on natural frequencies and critical speeds by comparing the dynamic behaviour of the rotors with the simple hollow shafts and the hollow shaft with honeycomb structures. The results indicated that the integration of honeycomb structures injected important stiffness and damping properties, leading to significant variations in the natural frequencies and critical speeds of the rotors. The agreement between the experimental and numerical results validated the accuracy of the numerical model and predicted the dynamic behaviour of the rotors. This validation is crucial for the dynamics of rotor design and future applications. The results offer new perspectives on rotor behaviour with honeycomb structures that develop and optimize future design. [ABSTRACT FROM AUTHOR]

In rotating machinery, aerodynamic forces and oil film forces often lead to cross-coupling stiffness. This paper is aimed at studying the stick-slip whirling vibrations induced by the piecewise smooth rotor/stator frictions in a modified flexible rotor subjected to cross-coupling stiffness. Governing equations determining the sliding region and boundaries of piecewise discontinuous friction are defined. This analytical study was conducted to discuss the complex vibrations and bifurcations. Various types of sliding motions (continuous pure rolling, continuous crossing, and grazing–sliding) were observed in this research. Further, as for discussing the impacts of the parameters on nonlinear sliding vibrations, a parametric study was conducted. The obtained results reveal that with an increase in the cross-coupling stiffness coefficient, continuous pure rolling occurs earlier, and the disk vibration time around the contact regime becomes shorter. For studying the self-excited backward whirling vibration of stick–slip nonlinear motions, analytical formulations are established. Detailed vibration amplitude and frequency studies of friction-induced backward whirling vibrations were carried out. Numerical simulations were performed to compare them with the analytical solutions and to validate the results as well. The proposed theory and results provide fresh perspectives for predicting friction-induced whirlings and creating proper designs for turbo machinery. [ABSTRACT FROM AUTHOR]

The construction and assembly of an axial compressor blade row introduces real geometric features, which leads to the deviation of flow characteristics from the intended design. According to the realistic assembly errors observed in the four-stage low-speed research compressor developed by Shanghai Jiao Tong University, two representative step geometries at the rotor platform were abstracted. Unsteady simulations were carried out in the stage environment to study the influence of hub discontinuities on compressor performance and loss mechanisms. The comparisons of smooth hub, elevated hub (EH), and a wedged hub (WH) demonstrated that all the step geometries resulted in increased loss inside both rotor and stator rows. The loss induced by WH was more sensitive to step heights than EH. Under the influence of forward facing step, rotor incidence was reduced and horseshoe vortex (HV) was exacerbated, leading to the accumulation and separation of low momentum fluids at the pressure side corner. This led to a redistribution of losses across the span. In the lower half span, the relative total pressure loss increased almost linearly with step heights, while in the tip region, it reduced slightly. The backward facing step generated the step corner vortices (SCV) that shed and propagated downstream. The SCV interacted with the HV and cavity leakage vortex in the stator passage. Coupled with the augmented stator inflow angle, the corner separation at the suction side was dramatically intensified and led to a significant loss increase. [ABSTRACT FROM AUTHOR]

To enhance the fluid dynamic performance of bearingless cross-flow fans (CFFs), this paper presents a CFD-based optimisation of both rotor and static casing wall modifications. High-performance CFFs are essential in industrial applications such as highly specialised laser modules in the semiconductor industry. The goal for the investigated rotor modifications is to enhance the CFF's mechanical stiffness by integrating reinforcing shafts, which is expected to increase the limiting bending resonance frequency, thereby permitting higher rotational speeds. Additionally, the effects of these rotor modifications on the fluid dynamic performance are evaluated. For the casing wall modifications, the goal is to optimise design parameters to reduce losses. Optimised bearingless CFFs benefit semiconductor manufacturing by improving the gas circulation system within the laser module. Higher CFF performance is a key enabler for enhancing laser performance, increasing the scanning speed of lithography machines, and ultimately improving chip throughput. Several numerical simulations are conducted and validated using various commissioned prototypes, each measuring 600 mm in length and 60 mm in outer diameter. The results reveal that integrating a central shaft increases the rotational speed by up to 42%, from 5000 rpm to 7100 rpm , due to enhanced CFF stiffness. However, the loss in fluid flow amounts to 61% and outweighs the gain in rotational speed. Optimising the casing walls results in a 22% increase in maximum fluid flow reaching 1800 m 3 / h at 5000 rpm . It is demonstrated that the performance of bearingless CFFs can be enhanced by modifying the geometry of the casing walls, without requiring changes to the CFF rotor or bearingless motors. [ABSTRACT FROM AUTHOR]

This study explores the implications of the number of blades on the performance of both open and shrouded rotors. By conducting a thorough experimental analysis at a fixed solidity ratio, this research seeks to enhance our understanding of rotor dynamics and efficiency. Two-, three-, four-, and five-bladed rotors were designed and manufactured to have the same solidity ratio. This leads to smaller chord distribution values for higher blade numbers. The experimental analysis aims to quantify the effects of the number of blades and provides a comparative analysis of performance differences between the two rotor configurations (shrouded and open). For the open rotor, results indicate that increasing the number of blades has a minimal impact on overall performance. This is due to the decrease in the tip loss factor being counterbalanced by a decline in efficiency caused by the two-dimensional airfoil performance, which results from a smaller chord and a lower Reynolds number. In contrast, the shrouded rotor exhibits a noticeable performance decay with an increased blade count. Since tip loss is inherently absent in shrouded designs, the decline is primarily attributed to the two-dimensional airfoil performance. This decay occurs while maintaining a constant solidity ratio, highlighting the significant effect of blade count on shrouded rotor efficiency, thereby contributing to the optimization of rotor design in various engineering applications. [ABSTRACT FROM AUTHOR]

This paper delves into the dynamics of the pipe-in-pipe system, crucial in offshore oil and gas exploration, featuring an inner drill string nestled within an outer riser. A reduced-order model with five degrees of freedom is proposed to capture the coupled dynamics of this system. Here, the inner drill string is depicted as a torsional-lateral coupled rotor constrained by the outer riser. In contrast, the outer riser is modeled as a suspended stator subjected to vortex-induced excitations and contact forces. The model incorporates nonlinearities, including dry frictions, collisions, loss of contact, and nonlinear damping through the van der Pol wake oscillator. This comprehensive model allows an in-depth exploration of the dynamics of the coupled pipe-in-pipe system. The research revealed that the overall coupling frequency of the PIP system is slightly lower than the natural frequency of a single riser. Additionally, vortex-induced vibration of the pipe-in-pipe system predominantly occurs near the coupling frequency (cross-flow vibration) and its second frequency (in-line vibration). Furthermore, the coupling frequency and its higher harmonics are significant frequency components of drill string whirl. Parametric analysis is conducted based on the non-dimensional numerical model, revealing a novel and stable whirling phenomenon termed "following whirling" at low rotary speeds of the drill string. This phenomenon arises from a combination of vortex-induced vibration and dry friction. During this stable following whirling, the riser's vortex-induced vibration traces an "8"-shaped trajectory, while the drill string follows suit, oscillating between forward- and backward-whirling, forming a "C"-shaped trajectory relative to the riser. Additionally, within the frequency lock-in region of the vortex-induced vibration, frequency analysis indicates induced nonlinear resonances through the continuous contact whirling of the drill string, showcasing a strong coupling between the drill string and the riser. In contrast, within the non-lock-in region, the system dynamics are primarily dominated by the backward whirling of the drill string. Furthermore, the parametric study reveals that the backward whirling of the drill string can significantly reduce both the cross-flow and the in-line vortex-induced vibration of the riser. However, as a side-effect, the backward whirling of the drill string can lead to higher-frequency vibrations, potentially causing fatigue damage to both the outer riser and the inner drill string. This research lays a foundation for comprehending the coupled dynamics of pipe-in-pipe systems in offshore drilling applications. [ABSTRACT FROM AUTHOR]

Spherical piezoelectric motors (SPMs) represent a promising actuator technology applicable to the development of motion control systems with multiple degrees of freedom. However, few SPMs have made it successfully to market, as an effective and systematic rotor orientation analysis and manipulation technique has yet to be developed. This study thus developed a novel triplet-stator SPM design that integrates electrode configuration to excite lateral vibrations and offers two fundamental rotor orientations for each set of piezoelectric plates by changing the contact position between the rotor and stator. To accomplish omnidirectional orientations for the proposed SPM system, we present a systematic orientation analysis based on spherical coordinates. We further apply the concept of vector composition to derive new composite orientations by adjusting the magnitude ratio of the provided torques between three stators. An orientation angle representation accounting for the rotor dynamics is used to validate the correctness of the synthesized orientation vectors both in simulation and experiments. The orientation analysis results in a three-dimensional sphere containing eight vector spaces corresponding to eight stator actuation modes, in which an arbitrary rotor orientation reference command can be generated under the designed actuation modes. Experimental results were well correlated with simulations, thereby verifying the effectiveness of the proposed SPM system design and orientation analysis. [ABSTRACT FROM AUTHOR]

Ultra-high-speed permanent magnet motors (UHSPPMs) are gradually increasing in the number of scenarios to realize energy saving and emission reduction due to their advantages such as high power density and fast response speed, and their accurate design and analysis are becoming more and more important. UHSPMMs need to consider the effects of multiple physical fields such as electromagnetism, force, and heat on their performance and structure due to their high rotational speed and small size. In this paper, firstly, the loss of each component of the motor is accurately calculated, and the distribution of the flow field and temperature field inside the motor is obtained by computational fluid dynamics (CFD) to determine the limiting working conditions of each component of the motor. Secondly, the mechanical stresses of the rotor are calculated at different limiting working conditions, especially the checking of the stresses of the permanent magnets and the sleeves when they are working at different temperature gradients, in order to improve the reliability of the ultra-high-speed rotor. Furthermore, the dynamics analysis is performed for the whole rotor system to ensure stable operation for a long time at the rated working conditions. Finally, the dynamics of the whole rotor system is analyzed to ensure that the ultra-high-speed permanent magnet rotor can operate stably for a long period of time at the rated operating conditions. Based on the theoretical calculations and analyses, a 25 kW, 95 krpm prototype was designed and fabricated, and relevant experimental studies were carried out. The correctness of the calculation of rotor mechanical properties under extreme working conditions (extreme speed and extreme temperature) is verified through tests, which achieved the target of design accuracy within 5%, and can provide great help to further improve the high-precision design of UHSPMMs. [ABSTRACT FROM AUTHOR]

In this article, we study the influence of the excitations created by the support movement, on the vibratory behavior of the rotor. The modeling of the rotor system is done by the hierarchical polynomial (h-p) version of the finite element method, on an on-board rotor with movable non-deformable supports. The disk is supposed to be rigid; the shaft is deformable and it is treated with the theory of beams of Euler Bernoulli. The 3D beam element has two nodes and is used for the discretization of the rotor. The shape functions used are the cubic Hermit type which respect the boundary conditions in all directions and represent the h-version of the finite element method and are modified so that it can be combined with the K-orthogonal polynomial form functions for the use of the h-p version of the finite element method. The energy method is used to determine the kinetic energies, and deformation of rotor system. The equations of motion of the rotor system are determined by the Lagrange method. The analysis of the dynamic behavior of the orbits of the on-board rotor systems is studied using the implicit method of Newmark and Newton-Raphson. In this article, we make some examples to study the influence of the excitations of the mobile support on the rotor behavior. [ABSTRACT FROM AUTHOR]

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This paper aims to study and demonstrate the possibilities of using reinforcement learning for the synthesis of multi-objective controllers for radial actively lubricated hybrid fluid film bearings (ALHBs), which are considered to be complex multi-physical systems. In addition to the rotor displacement control problem being typically solved for active bearings, the proposed approach also includes power losses due to friction and lubricant pumping in ALHBs among the control objectives to be minimized by optimizing the lubrication modes. The multi-objective controller was synthesized using the deep Q-network (DQN) learning technique. An optimal control policy was determined by the DQN agent during its repetitive interaction with the simulation model of the rotor system with ALHBs. The calculations were sped up by replacing the numerical model of an ALHB with its surrogate ANN-based counterpart and by predicting the shaft displacements in response to operation of two independent control loops. The controller synthesized considering the formulated reward function for DQN agent is able to find a stable shaft position that reduces power losses by almost half compared to the losses observed when using a passive system. It also is able to prevent the established limit of the minimum fluid film thickness being exceeded to avoid possible system damage, for example, when the rotor is unbalanced during the operation. Analysis of the development process and the results obtained allowed us to draw conclusions about the main advantages and disadvantages of the considered approach, and also allowed us to identify some important directions for further research. [ABSTRACT FROM AUTHOR]

Squeeze film dampers are used to reduce vibration in aircraft jet engines supported by rolling element bearings. The underlying physics of the squeeze film dampers has been studied extensively over the past 50 years. However, the research on the SFDs is still ongoing due to the complexity of modeling of several effects such as fluid inertia and the modeling of the piston rings, which are often used to seal SFDs. In this work, a special experimental setup has been designed to validate the numerical models of SFDs. This experimental setup can be used with various SFD geometries (including piston ring seals) and simulate almost all conditions that may occur in an aircraft jet engine. This work also focuses on the inertia forces of the fluid. The hydrodynamic pressure distribution of a detailed 3D-CFD model is compared with the solution of the Reynolds equation including inertia effects. Finally, the simulation results are compared with experimental data and good agreement is observed. [ABSTRACT FROM AUTHOR]

The shaft system, transferring the kinetic energy of water flow into electrical energy, is the most critical component in hydropower plants. Installation deviations of the shaft system for a giant hydro-generator unit can have significant impacts on its dynamic characteristics and overall performance. In this investigation, a three-dimensional geometry of the shaft system of an operating hydro-generator unit prototype with a rated power of 1 GW is established. Then, the calculation model of the shaft system is generated accordingly with tetrahedral and hexahedral elements. By applying different boundary conditions, the finite-element method is used to analyze the influences of installation deviations, including shaft radial misalignment and angular misalignment, on the dynamic characteristics of the shaft system. The calculation results reveal that the installation deviations change the natural frequencies, critical speeds, and mode shapes of the shaft system to a certain degree. The natural frequencies of the backward precession motion with installation deviations are reduced by 23% and 38% for the rated speed and the maximum runaway speed. Furthermore, for the forward precession motion, they increased by 30% and 48%, respectively. The critical speeds for the shaft system with radial and angular deviations are 3.2% and 3% larger than the critical speed of the shaft system without any mounting deviations. The radial and angular installation deviations below the maximum permissible values will not result in the structural performance degradation of the 1 GW hydro-generator shaft system. The conclusion drawn in this research can be used as a valuable reference for installing other rotating machinery. [ABSTRACT FROM AUTHOR]

This article aims to study the physical characterization and performance of a material‐based magnetorheological fluid (MRF) dampers for vibration attenuation of a high‐speed rotor–motor system near resonance. Four samples are synthesized by combining electrolytic iron and carbonyl iron (CI) with Castor and Karanja oil and experimentally investigated for their contribution to vibration attenuation. The results demonstrate effective vibration attenuation of the biodegradable oil‐based MRF damper than the nonbiodegradable oil‐based MRF damper. The best vibration attenuation is observed in the case of moderately viscous MRF. CI‐based samples exhibit a lower sedimentation rate, hence recommended for MRF. The vibration amplitude is maximum for the Castor oil‐based MRF damper, however, is minimum for the Karanja oil‐based MRF damper. The steady and transient results of vibration amplitudes are obtained and analyzed for different currents supplied to the MRF damper. The range of unstable speed near resonance is also obtained. The prepared samples show higher attenuation of 6–25% than Sample 5. The vibration amplitude attenuation of Sample 4 and Sample 5 are 47% and 22%, respectively. The findings of this study carry significant implications for controlling the vibration of the dynamic system using an eco‐friendly damping system. [ABSTRACT FROM AUTHOR]

This article proposes a new nonlinear processing method combined with model predictive control (MPC) to study the demagnetization vibration problem of permanent magnet synchronous motors (PMSMs). First, based on the theory of rotor dynamics, a demagnetized rotor vibration dynamics model considering the unbalanced magnetic pulling (UMP) caused by demagnetization of PMSM was constructed. Accurately modeling the nonlinear UMP function is difficult in practical engineering, thereby increasing the complexity of accurately constructing the parameters of the demagnetized rotor vibration dynamics model. Thus, this article innovatively constructs an empirical function model for UMP based on practical experience and then establishes a system observer model. Sufficient conditions are obtained for the system observer model based on Lyapunov stability theory to effectively observe the demagnetization vibration dynamics model. Then, an MPC scheme is proposed based on the constructed demagnetization vibration observer model. Finally, numerical simulation was conducted to verify the effectiveness of the system observer model in tracking the system model and predicting the effectiveness of system vibration control. [ABSTRACT FROM AUTHOR]

A multibladed drag-based Vertical Axis Wind Turbine (VAWT) was developed and its startup dynamics evaluated using wind tunnel tests. The experimental data obtained for the time-based angular position of the rotor shaft at Aberdeen's average wind speed of 6 m/s show an initial rapid acceleration of the VAWT due to the drag force being exerted on the rotor blades. This acceleration becomes more gradual until the VAWT reaches its peak rotational speed of 85 rpm in 30 s, which corresponds to an operating tip speed ratio (TSR) of 0.42. The operating TSR of the VAWT was found to be 27% higher than previously reported in numerical studies. [ABSTRACT FROM AUTHOR]

Bubble inclusion in the tribo-pair leads to two-phase fluid lubrication. Upon the initial introduction of air bubbles to the tribo-pair, it can lead to instability in the operational state. A numerical model is formulated by coupling the fluid Reynolds equation, bubble dynamics equation, and rotor dynamics equation. Various parameters, such as hydrodynamic pressure, fluid carrying capacity, rotor trajectory, and equilibrium position, are employed to characterize the impact of operational and fluid interface parameters on the bubble entrainment process. The findings reveal that the hydrodynamic pressure plays a crucial role in establishing the correlation between velocity and fluctuations in kinetic parameters. Surface tension predominantly influences bubbles within the dispersion region, while surface dilatational viscosity affects the entire domain. Lower surface dilatational viscosity or neglecting surface tension can trigger larger fluctuations in the rotor trajectory. Changes in liquid-phase viscosity result in fluctuations in bubble behavior and dynamics parameters, influenced by the equilibrium position and the effect of hydrodynamic pressure. Higher initial gas-phase volume fractions lead to a more pronounced reduction in fluid-carrying capacity and increased system instability. [ABSTRACT FROM AUTHOR]

The pressure gain combustion in wave rotors has the potential to significantly enhance the performance of gas turbine engines. Wave rotor design focuses on understanding the complex behavior of rotating channels, which is challenging due to high rotational speeds. To investigate the influence of different working conditions on the unsteady process within the wave rotor combustor, a simplified 24-channel model was established to study both the unsteady flow and the wave dynamics. The calculations indicate that, for the current port position adopted and a rotor speed of 4000 rpm, backflow occurs at the inlet port for various inlet pressures. By analyzing the working sequence of the wave rotor combustor, it is found that the inlet port does not close in time when the pre-compression wave returns. This delay results in reflected expansion waves or compression waves moving within the channel, which affect a portion of the pressure gain, leading to a damped sinusoidal trend in the pressure profiles within the channel. The optimal pre-pressurization effect can be achieved at a rotor speed of 2000 rpm for the test conditions considered, and the total pressure gain achieved was 6.3%. By adding hot-jet ignition, it is found that the shock wave and flame interact at least five times in the current simulation. The shock–flame interaction can greatly accelerate the process of chemical reactions. After the fourth interaction, the shock wave achieved local coupling with the flame, forming a local high-pressure area of 4 bar, verifying the effectiveness of the wave rotor as a constant-volume supercharging device. [ABSTRACT FROM AUTHOR]

Vibroacoustic metamaterials represent an innovative technology developed for broadband vibration reduction. They consist of an array of local resonators and are able to reduce vibrations over a wide frequency range, commonly referred to as a stop band. Vibroacoustic metamaterials may be a promising strategy to reduce out-of-plane vibrations of thin-walled, disk-shaped structures, such as saw blades. However, their behavior in rotating systems has not yet been fully understood. In this study, a vibroacoustic metamaterial integrated into a circular disk for the reduction of out-of-plane vibrations is experimentally investigated in the rotating and non-rotating state. Derived from the predominant frequency range of noise emitted by saw blades, a vibroacoustic metamaterial with a numerically predicted stop band in the frequency range from 2000 Hz to 3000 Hz, suitable for integration into a circular disk, is designed. The resonators of the metamaterial are realized by cutting slots into the disk using a waterjet cutting machine. To experimentally examine the structural dynamic behavior, the disk is excited by an impulse hammer and observed by a stationary optical velocity sensor on a rotor dynamics test stand. The results of the rotating and the non-rotating state are compared. The measurements are carried out at two different radii and at speeds up to 3000 rpm. A distinct stop band characteristic is shown in the desired frequency range from 2000 Hz to 3000 Hz in the rotating and non-rotating state. No significant shift of the stop band frequency range was observed during rotation. However, adjacent modes were observed to propagate into the stop band frequency range. This work contributes to a better understanding of the behavior of vibroacoustic metamaterials in the rotating state and enables future applications of vibroacoustic metamaterials for vibration reduction in rotating, disk-shaped structures such as saw blades, brake disks or gears. [ABSTRACT FROM AUTHOR]

The research work is focused on vibration analysis of rotating equipment's and is carried out in Vibration Analysis Lab at KLS Vishwanathrao Deshpande Institute of Technology, Haliyal funded by Vision Group Science and Technology under K-FIST-L2 collaborated with Diagnostic Engineers, Bangalore. The main objective of research work is to predict the behavior of a complex rotor model using Xlrotor technique and obtained results is validated with experimental results. The Xlrotor tool is not only applied at design stage but also it is focused on maintenance stage to predict the behavior of rotor model effectively which cannot be done by other techniques. The Xlrotor technique is followed by various vibration analysts for root cause analysis. Hence, the complex rotor model is considered for vibration analysis to know undamped, damped critical speeds and imbalance response at bearings (end boundary conditions) due to imbalance at various locations. The results clearly highlight a small 10 gm of imbalance in rotor model results high vibration in end boundary conditions (bearings). This study also specifies the proper selection of bearing stiffness and damping properties that cannot be predicted effectively by any other methods. The response is recorded at bearing supports and placement of an imbalance mass at different location of rotor model assembly to predict its behavior and diagnose the model effectively. [ABSTRACT FROM AUTHOR]