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In this contribution, we employ a recurrent neural network (RNN) architecture in a variational optimization to obtain the ground state of linear chains of planar, dipolar rotors. We test different local basis sets and discuss their impact on the sign structure of the many-body ground state wavefunction. It is demonstrated that the RNN ansatz we employ is able to treat systems with and without a sign problem in the ground state. For larger chains with up to 50 rotors, accurate properties, such as correlation functions and Binder parameters, are calculated. By employing quantum annealing, we show that precise entanglement properties can be obtained. All these properties allow one to identify a quantum phase transition between a paraelectric and a ferroelectric quantum phase. [ABSTRACT FROM AUTHOR]

A number of internal rotation codes can deal with the combination of one or two internal rotors with one 14N quadrupole nucleus, but once it comes to two 14N nuclei, no such code is available even for the case of one internal rotor. We present here the extension of our internal rotor program called BELGI-2N using the rho-axis method global approach to deal with compounds containing one methyl rotor and two weakly coupling 14N nuclei. To test our new code, we applied it to the microwave data recorded for N-methylimidazole, 2-methylimidazole, 4-methylimidazole, and 5-methylimidazole using a chirped-pulse Fourier transform microwave spectrometer in the 7.0–18.5 GHz frequency range. Compared to the previously published study, BELGI-2N was able to (i) significantly increase the number of assigned and fitted lines, (ii) fit the complete datasets considering both the internal rotation and the 14N nuclear quadrupole coupling effects simultaneously, and (iii) achieve standard deviations within the measurement accuracy for all methylimidazole isomers. [ABSTRACT FROM AUTHOR]

In this work, we perform a density matrix renormalization group study of chains of planar rotors interacting via dipolar interactions. By exploring the ground state from weakly to strongly interacting rotors, we find the occurrence of a quantum phase transition between a disordered and a dipole-ordered quantum state. We show that the nature of the ordered state changes from ferroelectric to antiferroelectric when the relative orientation of the rotor planes varies and that this change requires no modification of the overall symmetry. The observed quantum phase transitions are characterized by critical exponents and central charges, which reveal different universality classes ranging from that of the (1 + 1)D Ising model to the 2D classical XY model. [ABSTRACT FROM AUTHOR]

In this study, a composite control algorithm based on classical control methods is developed to achieve all control objectives, such as power production, load reduction, and motion reduction, for the floating wind turbine. In previous studies, peak shaving and nacelle feedback were used together to reduce both platform motion and the tower-base loads of floating wind turbines. The new approach presented in this study not only addresses the platform motion and tower loads but also aims to mitigate the rotor speed fluctuations and the blade loads by additionally introducing feedforward control and individual pitch control. This expansion enhances the applicability and control performance of classical control algorithms. To achieve this, parametric simulations were conducted using OpenFAST to assess the effects of control parameter variations for each control technique. The simulation results showed that the proposed control algorithm significantly reduced the rotor speed fluctuations, tower loads, blade loads, and platform motion compared with the baseline controller. [ABSTRACT FROM AUTHOR]

This study investigates the efficiency evaluation of a compressor rotor designed for drive units requiring compressors with a power demand of less than 30 kW. The primary aim of the research presented in this article is to assess the feasibility of utilizing axial compressors to maintain high efficiency across a broad range of rotor speeds. A critical challenge in the considered power range is the occurrence of low Reynolds numbers, specifically those below 250,000. This research seeks to identify the underlying causes of efficiency degradation at low Reynolds numbers and determine the rotor's geometric parameters which most significantly influence the localized efficiency drop. Compressor efficiency was evaluated through numerical simulations. The numerical model was validated using experimental data and subjected to a grid independence study. Simulations were conducted for nine geometric configurations of the axial compressor rotor, with modifications to parameters such as the blade angle, blade thickness, blade solidity, and hub-to-tip ratio. For each configuration, a series of simulations was performed at rotor speeds ranging from 400 RPM to 2400 RPM. The simulation results indicated that the blade angle solidity was the most influential parameter affecting efficiency. A reduction in the blade angle led to approximately a 20% decrease in efficiency, primarily due to localized flow separation near the blade tip. Additionally, altering the number of blades caused a 20% efficiency reduction attributed to hub corner separation. The findings enabled the identification of optimal parameters, which will serve as a foundation for efficiency testing in the multistage configuration. [ABSTRACT FROM AUTHOR]

Flexibility plays a crucial role in the design and performance of modern rotors. Its impact on rotor performance and its ability to adapt to external flow disturbances are well-established. In this study, we employ numerical simulations to explore the behavior of a flexible rotor submerged in a turbulent flow, aiming to forecast the influence of its flexibility on performance metrics. The rotational motion of the rotor and the forces imposed by the flow induce deformations in the blades, including bending and twisting. These deformations not only disrupt the flow patterns (vortices) in the turbulent wake but also modify the aerodynamic profiles, thereby affecting essential performance aspects such as thrust, drag, and lift. Our objective is to uncover the relationships between blade deformations, rotation frequencies, and rotor performance in a turbulent flow with a Reynolds number, R e = O (1 0 4) , and for a tip speed ratio in the range [ 0 , 18 ]. We demonstrate that the mean blade bending angle can be effectively expressed using a modified Cauchy number, revealing a scaling law. We also examined how the aerodynamic performance of the rotor blade is affected by variations in the tip speed ratio, either amplifying or reducing it. Through this research, we advance our understanding of the interplay between rotor flexibility, deformation, and performance, contributing to the optimization of rotor design and operational efficiency. [ABSTRACT FROM AUTHOR]

Detecting Broken Rotor Bars (BBFs) in induction motors is critical for ensuring their reliable operation. While conventional methods, such as Fast Fourier Transform analysis of stator current spectra, have been widely used for BBF detection, they suffer from limitations like spectral leakage and low-frequency resolution. The Welch Transform is known for effectively reducing spectral leakage and noise when analyzing finite data. This paper presented an innovative FPGA-based architecture for real-time implementation of Welch transform for BBFs in induction motor diagnostics accompanied by a novel right-band-based detection technique, and the architectures are explained in detail. We conducted experiments to verify the effectiveness of the proposed architectures, including applying BBF faults under varying loads and severity levels. The results demonstrated the efficiency of our proposed architectures, as it was found that resource consumption rates were meagre, and error indicators were obvious. The results were displayed in real-time through a user-friendly graphical interface, demonstrating the practical effectiveness of the FPGA-based solution. [ABSTRACT FROM AUTHOR]

This paper presents a method of rotor position estimation for switched reluctance motors suitable for saturation. The effects of saturation as well as voltage changes are taken into account at the same time. It is based on the inductance in the unsaturated region. When the phase inductance is equal to the threshold, it is defined as a characteristic point. Meanwhile the characteristic pulse signal is triggered. Different inductance intersection thresholds are determined when the phase current and bus voltage change. The rotor position is estimated by interval speed. Compared with the traditional inductance method, the position estimation error is smaller. Finally, the correctness and effectiveness of the proposed method are verified by simulation and experiments. [ABSTRACT FROM AUTHOR]

In this paper, an aerodynamic design method for a contra-rotating open rotor based on lifting line theory is presented. By changing the number of blades, the solidity and camber angle are changed, and several different aerodynamic designs are completed. The effect of solidity and camber angle on the aerodynamic performance is studied. The results show that when the number of blades increases, the solidity linearly increases while the camber angle nonlinearly decreases. There exists an optimal number of blades for aerodynamic design. The highest propulsion efficiency improved by 2.41% compared to the lowest value. The highest propulsion efficiency of 0.81 occurred with 10 blades. Increased solidity leads to increased viscous and wake losses. The change in solidity also changes the shock wave structure in the channel and the static pressure distribution on the blade surface. When the number of blades is reduced, decreased solidity results in greater circumferential differential pressure. The increased camber angle brings a larger inverse pressure gradient in the flow direction. This resulted in a significant flow reversal region in the channel, increasing the rear rotor root losses. [ABSTRACT FROM AUTHOR]

Coaxial rotor helicopters have many advantages and have a wide range of civilian and military applications; however, there is a risk of blade collision between the upper and lower rotor blades, and the challenge still exists in balancing rotor parameters and flight control. In this paper, a blade tip distance measurement method based on coded ultrasonic ranging and phase triggering is proposed to tackle this measurement environment and expand the application of ultrasonic ranging in high-speed dynamic measurement. The time of flight (Tof) of coded ultrasonic ranging is calculated by the amplitude threshold improvement method and cross-correlation method, and the sound velocity is compensated by a proposed multi-factor compensation method. The static distance error of coded ranging with different codes are all within ±0.5 mm in the range of 10–1000 mm. The measurement error characteristics under different trigger phases and different rotational speeds are studied, and the error model is fitted by the back-propagation neural network method. After compensation, the vertical distance measurement errors are within ±2 mm in the range of 100–1000 mm under the condition that the rotational speed of the blade is up to 1020 RPM. It also provides a potential solution for other high-speed measurement problems. [ABSTRACT FROM AUTHOR]

Rub-impact is a common nonlinear fault of the rotor system, occurring in rotating machines with radial clearance between the rotor and the stator, which may lead to serious consequences. Since the vibration response of rotor rub-impact is shown as multicomponent with time-varying characteristics of undulatory instantaneous frequency, it is desired to exploit advanced signal processing methods for rub-related feature excavation and failure diagnosis under complex noise interferences, which is of crucial significance to ensure the stable and efficient operation of the whole unit. This paper concerns the processing of acceleration signals and proposes a novel intrawave frequency modulation detection approach for structural rotor rubbing diagnosis based upon targeted component extraction and stochastic resonance enhancement. First, the acquired vibratory acceleration signal is converted into displacement signal via a two-stage integration strategy. Next, to extract the rotating frequency component of high information clarity for further time–frequency analysis from the multicomponent signal, an especially designed improved variational mode decomposition method based on the modified target frequency index is put forward, and the instantaneous frequency of the objective component is estimated. Then, the optimum stochastic resonance is leveraged for intrawave frequency modulation enhancement. Finally, the rotor rub-related symptom can be distinctly revealed and the diagnostic procedure can be performed. The effectiveness and superiority of the proposed rotor rub-impact diagnosis approach are demonstrated through both simulations and experiments, indicating that it is suitable to be implemented in practical applications, with high noise-resistance ability, and can efficiently extract the potential characteristics of rotor rub-impact malfunction from multicomponent signals. [ABSTRACT FROM AUTHOR]

To increase the accuracy of an analytic method based on the concentrated-mass approach for solving the mechanical operating modal characteristics of complete impellers and impellers with balancing holes in a centrifugal-pump rotor system, we establish a mathematical model and a three-dimensional simulation model for a double-supported three-stage centrifugal-pump rotor system. By comparing the modal results obtained from the two models, we propose a mathematical model that integrates the optimization of mass-distribution methods and bending stiffness correction coefficients, and we derive an optimized mathematical model for rotors with balancing holes. The effectiveness of the optimized mathematical model is validated via three-dimensional simulation, and the influence of balancing holes on the wet modes is analyzed. The results show that the wet natural frequencies are lower than the dry ones and that the wet natural frequencies obtained from analytical calculations are consistently higher than those obtained from three-dimensional simulation results. The optimized mathematical model significantly improves the accuracy of the wet modal characteristics for both complete impellers and impellers with balancing holes, with the errors in the low-order natural frequencies reduced by more than 50%. Under the same hole spacing, the natural frequencies of the three-stage centrifugal pump rotor system decrease with increasing hole diameter slightly. Under the same hole diameter, the natural frequencies of the rotor system increase slightly with the hole spacing. The effect of stiffness changes caused by balancing holes on the natural frequencies is larger than the effect of mass changes. [ABSTRACT FROM AUTHOR]

Steel–concrete hybrid towers (SCHTs) have been adopted as a popular supporting structure for wind turbines with the increasing hub height and rotor diameter. The excessive transverse vibration of the supporting tower adversely compromises the turbine’s operation and leads to structural deteriorations. The tuned mass damper (TMD) has been validated as an efficient device integrated with high-rise structures in vibration suppressions. This study aims to provide a reliable method for determining the key parameters of the TMD to obtain the optimal performance in vibration suppressions. This study begins with a rigorous theoretical analysis to investigate the dynamic responses of the SCHT. The dynamic analysis serves as a basis for developing a dynamics model of the SCHT integrated with a TMD, which provides a programmable method to analyze the effect of the TMD on the dynamic responses of the SCHT. Then, an optimization model based on the genetic algorithm (GA) is established to obtain the optimal parameters of the TMD. Finally, a numerical test comprising 12 loading conditions is conducted to analyze the vibration mitigation effect of the TMD. The validation process also provides discussions about the influence of the wind turbine operation states and the fitness function adopted in the GA on the efficiency of the TMD. Those findings demonstrate the effectiveness and limitations of the TMD for mitigating vibrations of the SCHT. It thereby contributes to the understanding and improvement of vibration control strategies for SCHT structures and can guide future design and optimization efforts. [ABSTRACT FROM AUTHOR]

Dynamic loads are inevitably generated during the operation of rotating machinery. In situ monitoring the dynamic loads is of great significance for assessing shafting health. Triboelectric nanogenerator (TENG) is sensitive to motion but not suitable for load monitoring, while piezoelectric nanogenerator (PENG) is just the opposite. Therefore, the combination of the two can complement each other. From this, a dynamic load monitoring smart bearing (DLMSB) integrated with TENG and PENG is proposed. The specially designed TENG can produce an "M‐waveform", which can be used to extract rotation frequency and distinguish the quadrant of the rotor. Meanwhile, applying PENG to capture the load condition of the bearing, and referring to the main frequency of M‐waveform, it is convenient to obtain the dynamic loads of shafting. Furthermore, a real‐time monitoring system is developed, which can realize not only real‐time monitoring of the rotation speed and dynamic loads magnitude but also the quadrant discriminating of dynamic loads. The results have shown that the monitoring error for dynamic loads is 3 N or 5.5%, and the accuracy rate for determining the quadrant of the dynamic loads can reach 93%. This study provides a novel approach for the in situ monitoring of mechanical operating status via nanogenerators. [ABSTRACT FROM AUTHOR]

The contra-rotating open rotor (CROR) engine has gained attention for its outstanding fuel-saving potential. Attention needs to be paid to the propulsion efficiency of the contra-rotating open rotor, as it is the key to realizing the engine's fuel-saving advantage. In this paper, the performance of CRORs with different lean angles is investigated by numerical simulation. Furthermore, the mechanism of the influence of leaned blades on the propulsion efficiency of the CROR is analyzed. The results show that the positive leaned blades (pressure-surface down) significantly improve the propulsion efficiency of the CROR, with a maximum improvement of 1.34%. In contrast, the negative leaned blades (suction surface down) reduce propulsion efficiency. Due to the radial equilibrium equation, the positive lean increases the radial pressure gradient. The increased gradient enhances flow on the suction surface and reduces the flow reversal region, thus improving the propulsion efficiency. At low advance ratios, the enhanced radial flow due to the leaned blades makes the optimization less effective. By comparing the inlet conditions of the front and rear rotors, it was found that the front rotor was less likely to have a flow reversal region compared to the rear rotor. If a flow reversal region occurs in the channel, it is necessary to introduce leaned blades. The most recommended lean angle is the one that makes the flow reversal region disappear exactly. [ABSTRACT FROM AUTHOR]

The axial misalignment and tip clearance of the double spiral seals are important indexes affecting the sealing performance of the double spiral seals. In practical engineering applications, the sealing ability of double spiral seals is greatly affected by axial misalignment and tip clearance, and the coupling of assembly parameters and structural parameters of double spiral seals leads to the difficulty of seal design and use. A numerical model of spiral seals was established, and the velocity field, pressure field and critical sealing ability of double spiral seals were simulated and calculated. The influence of different axial misalignment displacements and different tip clearances on the sealing ability of double spiral seals was analyzed. The influence of axial misalignment displacement, tip clearance and rotor speed on the sealing performance of double spiral seals is obtained. The above research results provide a design basis for the engineering application of double spiral seals. [ABSTRACT FROM AUTHOR]

Purpose: To study the dynamic characteristics of the gear-rotorbearing system under a non-inertial system. Method: A gear-rotor-bearing finite element dynamic model consisting of flexible shafts, rigid gear rotors, gear meshing, and bearings under non-inertial system is established and the transmission system's characteristics are investigated. First, the equations of motion of the rotor and shaft element are derived, and the gyroscopic effect in the gear rotor and shaft is considered. The subsequent step is to deduce the nodal equations of the gear mesh, which include the time-varying mesh stiffness, mesh damping, and transmission error excitation. The basic bearing stiffness and damping matrices are utilized to study the bearings' influence as elastic support boundaries. In conclusion, a dynamic model of the gear-rotor bearing system is assembled based on the node positions. Natural properties and dynamic responses are also investigated. Results: The results indicate that, in a non inertial system, the carrier (jet fighter) acceleration in the X-direction can suppress the x-direction vibrations to a certain degree and amplify the vibrations in the angular direction about the z-axis. The angular motions of the carrier about the Z-axis amplifies x-direction vibrations while suppressing vibrations about the z-direction. [ABSTRACT FROM AUTHOR]

To keep pace with the construction of the new‐type power system, virtual synchronous generator control, as a classical method of virtual inertia control, has been widely adopted due to its electromechanical characteristics similar to synchronous generator. However, the introduction of rotor motion equations leads to low‐frequency oscillation issues in virtual synchronous generator units similar to synchronous machines. To address this challenge, this paper constructs the Phillips‐Heffron model of the virtual synchronous generator grid‐connected system and analyses the mechanism of low‐frequency oscillation in virtual synchronous generator through the damping torque method. Subsequently, a virtual dual‐input power system stabilizer is proposed by drawing inspiration from the design principles of the traditional dual‐input power system stabilizer to suppress low‐frequency oscillations in the power system. The structure of the virtual dual‐input power system stabilizer is provided, and the phase compensation method is used to optimize the parameters of the virtual dual‐input power system stabilizer. Finally, the effectiveness of the proposed virtual dual‐input power system stabilizer is verified by simulation comparison. [ABSTRACT FROM AUTHOR]

The magnetic bearing rotor system is affected by internal uncertainties and various forms of external disturbances, which will affect the stability of the active magnetic bearing system. To address this issue, a composite hierarchical anti-disturbance strategy is used to improve the anti-disturbance ability of the magnetic bearing rotor system. The disturbance observer is used to compensate the system's external disturbances, and the controller is used to suppress the system's internal uncertainties. For this purpose, H ∞ controller, disturbance observer (DOB), and linear extended state observer (LESO) are designed, respectively. Then, H ∞ controller is combined with DOB and LESO to form H ∞-DOB and H ∞-LESO composite controllers and prove their stability. Finally, simulation and experiments show that H ∞ -DOB and H ∞ -LESO have better disturbance suppression effects than the H ∞ controller for external disturbances. And when the disturbance frequency or rotor rotation frequency of the system is high, H ∞ -LESO controller has better disturbance suppression effect than H ∞ -DOB. [ABSTRACT FROM AUTHOR]

The design and technological scheme of a small-sized forage harvester with a capture width of 1.35 m equipped with a device oriented along the length of the stems was developed in this study. As a result of theoretical studies, the process of the movement of mass into the chamber of the mowing rotor due to centrifugal forces was revealed. The speed of mass movement and the average size of crushed particles with the mowing rotor were determined. The oriented feeding process of stems in the chamber of the chopping rotor is mathematically described in this paper. An analytical expression is obtained for determining the average size of crushed particles by the forage harvester, that is, a mathematical model of the processes of mowing, oriented feeding, and the chopping of stem fodder by the forage harvester. Laboratory and field tests of a forage harvester equipped with a device oriented along the length of the stems were conducted. The combine harvester's productivity was 6.14 t/h when mowing alfalfa. Special experiments were conducted to determine the average size of crushed particles after the mowing rotor. The average size of crushed particles with the mowing rotor was 147.4 mm, while the theoretical value was 144 mm. The difference between these values was only 2.31%. A special experiment was conducted on the combine without an orienting device to compare the quality indicators. The mass fractions of crushed particles of up to 50 mm in length when the combine was operating with and without an orienting device were 79.3 and 46.7, respectively. Accordingly, the average length of crushed particles was 33.79 mm and that without an orienting device was 77.07 mm. The theoretical value of the average length of crushed particles was 34.9 mm (i.e., the difference between the theoretical and actual value of the average size of the crushed particles was only 3.25%). All this proves that when the combine harvester was operated with an orienting device, there was a significant increase in the quality indicators of the chopped feed, and the reliability of the theoretical studies and the resulting mathematical model were determined. [ABSTRACT FROM AUTHOR]

In order to solve the problem of difficult simulation of the bolted joint structure of rotors, this study proposes an improved sub-regional thin-layer element method (ISRTL) and applies it to the equivalent simulation of the joint interface in the presence of bolt deviations. The theory introduces the fractal theory and Hertz contact theory to calculate the thin-layer parameter for the region with weak influence of bolt preload. The trend of dynamic response under different loosening deviation conditions is investigated. The experimental study of bolt deviation under axial tension and transverse vibration was carried out using a drum-disk rotor. The frequency and stiffness with bolt loosening position conform to M-type trend. The error of the eigenfrequencies calculated by the proposed method is within 3 % from the experimental results. The results demonstrate that ISRTL method has high accuracy and efficiency in the simulation study for the assembly deviation of rotor bolt connections. [ABSTRACT FROM AUTHOR]

This study investigates the prediction of the aerodynamic characteristics of Flettner rotors through three deep learning models. Various numbers of Flettner rotors, arrangements, and spin ratios are employed to consider these effects in the dataset. For the training of deep learning models, a dataset of aerodynamic force coefficients and flow fields is generated using Computational Fluid Dynamics (CFD). Three deep learning architectures (U-net, Encoder-Decoder, and Decoder models) are employed and trained to predict the aerodynamic characteristics of Flettner rotors. Three deep learning models are established through a training stage with a hyperparameter study and by altering the number of layers. The aerodynamic force coefficients and flow fields are predicted by established deep learning models and show small absolute errors compared to those from the CFD analysis. Moreover, predicted flow fields reflect the flow characteristics according to the difference of spin ratio and arrangement of Flettner rotors. In conclusion, the established deep learning models demonstrate rapid and robust predictions of aerodynamic force coefficients and flow fields for Flettner rotors under varying arrangements and spin ratios. Furthermore, a significant reduction in computational time is measured when comparing the analysis time of CFD simulations to the training and testing time of the deep learning models. [ABSTRACT FROM AUTHOR]

The flux observer method is widely utilized as a sensorless control technique in which the stator or rotor flux of IPMSM can be measured with a closed-loop observer or an integrator. However, DC-offset (DCoff), the ramp signal, and harmonics are consistently present in the acquired rotor flux because of an unidentified starting value, errors in the integral computation's current detection, and the inverter's nonlinearity. The aforementioned interference signals will drastically reduce the sensorless control efficacy. This work introduces an enhanced flux estimator with a negative feedback loop and PI controller to overcome the DC drift problem resulting from a pure integrator and a low-pass filter. Moreover, an optimal design approach of flux estimator structures with a broad range of speeds for Interior permanent magnet synchronous motor (IPMSM) drives is proposed, which utilizes an integrated topology of the voltage and current models incorporating a DC-offset PI-correction loop, actual and estimated flux magnitude's correction error. The flux vector's initial inaccuracy is eliminated, together with the DCoff and drift in the acquisition channel. A phase-locked-loop state estimator is utilized to derive the speed and position from the actual and estimated flux. The effectiveness and superiority of the suggested approach were proven by simulation and experimental findings for the IPMSM drives, which displayed high dynamic performances over varying scenarios. This reliable approach, including sensorless control, is suitable for all AC motors with sinusoidal flux distributions over a wide speed range. [ABSTRACT FROM AUTHOR]

Tip loss correction is necessary for all aerodynamic computations based on the blade-element momentum theory (BEMT) that plays an essential role in wind turbine design. Glauert tip-loss correction, which is most widely used, assumes the rotor is lightly loaded and thus lose some accuracy for modern wind turbines that are highly loaded. In the present work, a new g-function involving the rotor's thrust-coefficient is introduced, which connects the tip loss correction with the rotor's load condition and reduces the error of the tip loss correction. Computational tests are performed on two rotors that are distinct in size and tip shape. The new g-function results in good consistency between the computed forces and the reference data, exhibiting excellent role in improving the accuracy of the BEMT computations. In general, the new g-function combines good effectiveness and applicability, and thus has great potential for engineering applications. [ABSTRACT FROM AUTHOR]

Lobe pumps are used in many different sectors because of their versatility and effectiveness for managing multiphase flows. In this study, three-dimensional unsteady numerical simulations are performed to evaluate the vortex cavitation phenomenon in these pumps. The work combines dynamic meshing techniques, advanced vortex recognition methods, and a full cavitation model to provide insight into the genesis, evolution, and influence of vortex cavitation on pump performance. The results of the study demonstrate that under high-speed and high-pressure conditions, vortex flow occurs at the edge of the rear of the rotor lobe in the suction chamber of the lobe pump, resulting in the production of vortex cavitation. Cavitation is most strong at the core of the vortex, while the degree of cavitation at the edge of the vortex gradually diminished. The gas volume fraction reduces from 0.135 to 0.0832, and this makes the pressure decrease from 1.055 to 1.02 MP. The process of genesis, development, and removal of vortex cavitation is cyclic. At different levels of cavitation, the degree of pulsation in pump outlet flow, pressure, and radial force increases with increasing cavitation. Periodic vortex cavitation leads to periodic changes in pump output pressure, flow rate, radial force, and axial force. [ABSTRACT FROM AUTHOR]

The possibility of wobbling mode in the A ≈ 80 mass region is investigated by using the constrained triaxial covariant density functional theory and quantum particle rotor model for rubidium isotopes. Several states with the obvious triaxial deformation and high-j particle configuration are obtained in 79 , 81 , 83 , 85 Rb, which are suitable for establishing the wobbling mode. Taking the nucleus 81 Rb as an example, the available experimental energy spectrum with the π g 9 / 2 configuration is described well. The decreased energy difference between the partner bands, the enhanced B (E 2) out / B (E 2) in values, the angular momentum components and the azimuthal plots indicate that 81 Rb can be transverse wobbling candidate. The present work provides a promising basis for future experimental research on the wobbling mode in the A ≈ 80 mass region. [ABSTRACT FROM AUTHOR]

Understanding the aerodynamics of multi-rotor systems under temporally varying discrete gusts is the focus of this work. Axial and edgewise 1-minus-cosine profiles of varying amplitude (0.1 Ω R – 0.3 Ω R) and gust durations (0.3 – 15 s) were studied for the rigid, unarticulated Harrington single and coaxial rotors, and the Advanced Precision Composites (APC) 12x6E (a commercial off-the-shelf propeller) quad-rotor in hover. An in-house free vortex method (FVM) was utilized to study the time and frequency domain of thrust, span-wise angle of attack distribution, and the rotor wake structure across the gust event. It was observed that edgewise gusts produced higher frequency components in the thrust signal compared to axial gusts for all rotor systems. Strong wake–wake and blade–vortex interactions (BVI) were observed particularly for edgewise gusts, leading to strong variations in the sectional angle of attack and the thrust values. The wake interactions are more pronounced in the APC quad-rotor system, which operates at a low reduced frequency, essentially resulting in a quasi-steady response of the wake to the gust, resulting in a considerably higher number of BVI events, increased peak rotor loads, and higher frequency content. This study can aid in the understanding of the gust response of small- and medium-scale rotors. [ABSTRACT FROM AUTHOR]

For long flight duration and low noise emission, efficient and quiet quadcopters have a continuous demand. The toroidal rotor, which is ring-shaped with each blade forming a closed loop, is recognized for its potential to reduce tip vortex intensity, thereby improving aerodynamic efficiency and reducing noise levels. However, existing studies provide limited and sometimes controversial results of toroidal rotor performance relative to conventional rotors. This study aims to conduct a more comprehensive and systematic evaluation by employing a multi-objective optimization framework to design toroidal and conventional rotors for fair comparison. The optimization under the constraint of a required thrust considers objectives of aerodynamic efficiency and noise emission, with the design variable of blade twist angle. The study compares a toroidal 2-blade rotor with conventional 2-blade and 4-blade rotors. The results show that, while the toroidal rotor generates lower noise than conventional 2-blade rotors, it shows lower aerodynamic efficiency. Compared to conventional 4-blade rotors, the toroidal rotor has lower aerodynamic efficiency and larger noise emission. The trend is determined by the effect of rotational speed and blade–vortex interaction, as revealed by flow field analysis. Noise spectrum analysis allows to identify loading and thickness noise contributions and locate the primary noise sources of the toroidal rotor. [ABSTRACT FROM AUTHOR]

The shock wave/boundary layer interaction at the tip of transonic shrouded rotor blades usually leads to severe flow separation, which seriously affects aerodynamic performance. In this paper, the effect of part-shroud treatment on the shock wave/boundary layer interaction was numerically investigated. The part-shroud treatment suppresses the shock wave/boundary layer interaction-induced flow separation by introducing the tip leakage vortex at an optimal location. Parametric studies reveal that positioning the tip leakage vortex onset upstream the shock wave effectively reduces flow separation on the suction side, with the best outcomes achieved when the onset is slightly upstream of the shock wave. Based on these findings, the optimal shroud range extends from the leading edge to just upstream of the shock wave under a near stall condition. In National Aeronautics and Space Administration Rotor 35, the 30% shrouded rotors demonstrate a 2.4% improvement in the stall margin over 100% shrouded rotors with little reduction in peak efficiency. [ABSTRACT FROM AUTHOR]

The advantages of vertical axis wind turbines (VAWTs) have increasingly been recognized as effective turbomachines. Nonetheless, significant challenges remain regarding their efficiency and operational range. One promising approach to enhance their aerodynamic performance is the integration of vortex cavities, which can contribute to improved operational efficiency. This study utilizes computational fluid dynamics (CFD) to analyze the placement of vortex cavities systematically. The research investigates different configurations, such as suction side layout (SSL) and pressure side layout within single, double, triple, and quadruple arrangements to forecast their effect on H-type Darrieus VAWT aerodynamic performance. The findings show that the optimal configuration, with a concentration of 0.2 and 0.8 C in SSL, led to a 25% increase in power coefficient ( C p ) at the tip speed ratio (TSR) of 3.3. Conversely, the suboptimal configuration, with a concentration of 0.2 and 0.4 C in SSL, resulted in a substantial 54% decrease in C p at the same TSR due to issues with flow separation and lack of flow attachment after the vortex cavity. To optimize efficiency within the high-TSR range, a double, top, and bottom deflector configuration has been developed. Findings indicate that incorporating the double deflector has broadened the rotor's operational range from TSR 3.5 to 4.2 and concurrently elevated the rotor efficiency to 86%. [ABSTRACT FROM AUTHOR]

We conduct experimental investigations of the effect of the tip air injection as a stability control method on a low-speed axial-flow compressor experiencing severe circumferential total pressure distortion. Eight Coanda-shaped injectors, uniformly distributed upstream of the rotor blade leading edge, were employed to counteract stall margin degradation caused by a flat-baffle circumferential distortion. Unsteady pressure data from the tip clearance and rotor wake regions were captured using time-resolved sensors and probes and analyzed through time-frequency transformation and proper orthogonal decomposition (POD) techniques. POD investigation under distorted inflow conditions reveals that the third-order POD mode, which characterizes unsteady tip leakage flow (TLF), plays a dominant role in triggering stall. Based on this insight, tip air injection with varying momentum ratios was applied to enhance the stall margin. The positive correlation between the injected momentum ratio and stall margin improvement was established, demonstrating the stabilizing effect of tip air injection under the circumferential distortion. The results indicate that tip air injection primarily acts on the rotor blade tip region to suppress the unsteady TLF at the center and downstream areas of the distortion, leading to an increase in tip blade load and a reduction in both the scale and number of pre-stall disturbances. However, the injection has a minimal impact on the unsteady TLF frequency band in the rotor wake region. Additionally, the POD analysis confirms that as the injection rate is increased, the energy percentage, flow field intensity, and power spectral density amplitude of the third-order POD mode are decreased, further reflecting the mitigation of unsteady TLF. The present work provides important insight into the stability control mechanisms of a tip air injection under circumferential distortion, offering design guidance for the implementation of active stability control strategies in axial-flow compressors. [ABSTRACT FROM AUTHOR]

We report remarkable pattern formation of quasiperiodic domains in the two-dimensional parameter space of an intrinsically coupled system, comprising a rotor and a Duffing oscillator. In our analysis, we characterize the system using Lyapunov exponents, identifying self-similar islands composed of intricate regions of chaotic, quasiperiodic, and periodic behaviors. These islands form structures with an accumulation arrangement, denominated here as metamorphic tongues. Inside the islands, we observe Arnold tongues corresponding to periodic solutions. In addition, we surprisingly identify quasiperiodic shrimp-shaped domains that have been typically observed for periodic solutions. Similar features to the periodic case, such as period-doubling and secondary-near shrimp with three times the period, are observed in quasiperiodic shrimp as torus-doubling and torus-tripling. [ABSTRACT FROM AUTHOR]

Due to the complexity of determining the initial rotor flux and detecting errors, conventional rotor flux observation methods are easily affected by direct current (DC) components and harmonics. To address this issue, this paper proposes an in-phase filter (IPF)-based rotor flux observation strategy for sensorless control of permanent magnet synchronous machines (PMSMs). The core components of the IPF consist of a double second-order generalized integrator (DSOGI) and a phase angle compensation transfer function (PACTF). The DSOGI provides a accurate electrical angular frequency, while the PACTF implements a phase correction to the v q ′ signals. By employing IPF structure, accurate observations for rotor flux, electronic speed, and rotor position are achieved, which can be effectively used in the sensorless control of PMSMs, eliminating the need for magnitude and phase compensations. Finally, the proposed observation strategy is applied to an experimental bench of a PMSM, and its effectiveness is illustrated by experimental results. From experimental results, it can be concluded that the IPF is significantly better than the LPF, and 5% more accurate than the observer based on cascade second-order generalized integral(CSOGI) overall. • The rotor position of PMSMs is estimated via rotor flux observation. • An in-phase filter is developed for rotor flux observation in sensorless control of PMSMs. • The in-phase filter is implemented on a PMSM bench. [ABSTRACT FROM AUTHOR]

This paper provides a review of power system stability, focusing on the rotor angle case. To gain a preliminary understanding of the stability studies, the discussion begins with an overview of generators in power system generation. The distinguishing parameters of synchronous generators as compared to their counterparts such as induction generators, inductor alternators, and direct current generators are also emphasized. The discussion that is not bounded within their stability issues and control strategies is briefly assessed. The shortcomings and advantages of various modeling approaches are also discussed therein. To extend the thoughts, this review includes a thorough discussion and classification of power system stability, which includes rotor angle stability, frequency stability, and voltage stability. The stability of the rotor angle is important as it ensures frequency stability and voltage stability. This paper also presents the power system modeling approach that is able to facilitate the rotor angle stability studies. This paper also aims to review the established rotor angle stabilizers and algorithms developed by previous researchers. [ABSTRACT FROM AUTHOR]

The sensitivity of speed estimators for parameter variations presents a significant challenge for sensorless Induction Motor (IM) drives, particularly at very low speeds. This paper examines the impact of parameter variations and the PI adaptation mechanism on the stator current-based Model Reference Adaptive System (MRAS). In contrast to the estimation of rotor flux, the MRAS method uses the observed stator current and the stator current estimate error within the adjustable IM model. The stability analysis for changes in machine parameters and PI controller gains is examined using small-signal perturbation. Additionally, a sensitivity analysis of stator and rotor resistance changes is included. A complete simulation using MATLAB/Simulink and experimental validation using a laboratory prototype based on the DSP-DS1103 are provided. The analytical, modeling, and measurement results reveal that the suggested observer responds well and provides precise speed estimation in all four quadrants of operation. [ABSTRACT FROM AUTHOR]

Slurry pumps are widely used in complex media and harsh operating conditions due to their good transport performance and non-blocking characteristics. This paper takes a slurry pump as the research object, intending to analyze the impeller's structural characteristics and ensure the rotor's safe operation. By combining theoretical analysis and numerical simulation, the dynamic stress characteristics and vibration characteristics of the slurry pump structure are systematically analyzed using the bidirectional fluid-structure interaction research method, and the dry and wet modes of the pump rotor are analyzed. The results show that: the equivalent stress and deformation are the most severe under small flow conditions, and decrease with the increase of flow rate; the maximum equivalent stress occurs at the junction of the trailing edge of the suction surface of the blade and the back cover plate; the maximum deformation occurs at the intersection of the outlet of the impeller flow passage and the back cover plate; the wet mode has a lower inherent frequency than the dry mode; the rotor's inherent frequencies have some equal values of adjacent orders; the rotor's critical speed is 3408.4 r/min, far higher than the rotor's actual speed of 1480 r/min, and will not cause resonance. [ABSTRACT FROM AUTHOR]

Turbomachinery in gas turbines uses seals to control the leakage between regions of high and low pressure, consequently enhancing engine efficiency and performance. A film riding seal hybridizes the advantages of contact and non-contact seals, i.e., low leakage and low friction and wear. The literature focuses on the leakage performance of these seals; however, one of their fundamental characteristics, i.e., the gap between the rotor and seal surface, is scarcely presented. The seal pad levitates due to the deflection of the springs at its back under the influence of hydrodynamic forces. This study develops a test rig to measure the levitation of film riding seals. A high-speed motor rotates the rotor and gap sensors measure the levitation of the seal pads. Measurements are also compared with the predictions from a Reynolds equation-based theoretical model. Tests performed for the increasing rotor speed indicated that, initially, until a certain rotor speed, the pads adjust their position, then rub against the rotor until another rotor speed is reached, before finally starting levitating with further increased rotor speeds. Moreover, both the measured and predicted results show that pads levitated the most when located 90° clockwise from the positive horizontal axis (bottom of seal housing) compared to other circumferential positions. [ABSTRACT FROM AUTHOR]

Electric motors transform the electrochemical energy into mechanical energy needed for the vehicles' motion. Given that the transition from internal combustion engines to electric vehicles is likely to be the main driver of sustainable transportation, high‐performing electric motors will be increasingly important for this transition. Herein, the effect of the grinding process on the surface integrity and magnetic properties of NdFeB permanent magnets are investigated. NdFeB permanent magnets are most commonly used in the fabrication of permanent magnet electric motors and they are usually ground during their fabrication process chain in order to create a high‐quality cylindrical rotor for subsequent mechanical assembly. In particular, the effects of wet and dry grinding processes on magnetic properties and surface integrity are studied and compared. Guided by a thermal model, the grinding process parameters are varied highlighting their effects on the underlying thermomechanical phenomena responsible for the changes in surface integrity and magnetic properties observed. Wet grinding proves to be a viable process for NdFeB magnets. Additionally, acceptable results are achieved with dry grinding, which is particularly appealing due to its sustainability. It is noteworthy that the range of process parameters yielding acceptable results is narrower. [ABSTRACT FROM AUTHOR]

The periodic-cell model was proposed to simulate the successive contacts between the labyrinth fin and multiple honeycomb cells. With the experimental data, the finite-element-analysis (FEA) method with the periodic-cell model was validated. The effects of incursion parameters (i.e. incursion depth, incursion rate and sliding velocity) on the contact force, frictional temperature, material loss, and worn geometry of the honeycomb seal during the incursion process were studied. With the predicted worn geometry, the sealing performance degradation in the honeycomb seal was analyzed. The results showed that the proposed periodic-cell model has an excellent accuracy in predicting the wear behavior of honeycomb seal in rubbing events. The contact force between the honeycomb liner and labyrinth fin is pronounced especially at low sliding velocity and high incursion rate conditions, which increases the possibility of wear damage in the rotor part. At low sliding velocity and low incursion rate conditions, the frictional heat transferring to rotor part is increased, which increases the thermal stress near the contact region of the rotor part. As the clearance gap of honeycomb seal increases from 0.6 mm to 0.9 mm in the rubbing event, the leakage rate is increased by about 12%, and the carry-over effects downstream of the worn cells are increased. [ABSTRACT FROM AUTHOR]

In the heavy-duty vehicle industry, unbalance in the armature is one of the most common problems affecting starters' performance and durability. This research presents a comprehensive study to improve the balancing process for starting rotors in heavy-duty vehicles. The complete manufacturing process of armatures was analyzed to understand the contribution of assembly processes to unbalancing. The analysis revealed that the primary factor leading to high unbalance in these parts is the misalignment of conductors within the armature winding. During assembly, these conductors experience axial movements, resulting in non-uniform mass distribution and causing unbalanced values ranging from 150 to 350 g·mm. These values surpass the permissible limit, making rectification during the balancing process at the end of the assembly impossible. Consequently, a novel alignment tool was designed to address this issue, significantly reducing the effect and achieving the maximum allowable unbalance of 100 g·mm. This allowed the balancing machine used in the process to correct the initial unbalance of the reinforcements in a single work cycle, improving operation efficiency by about 15%. [ABSTRACT FROM AUTHOR]

In order to be able to recycle composite components made of polymer and metal, which are used in the automotive industry, the joints must be broken. The success of the separation is influenced by the stress and also by the joining mechanism between the polymer and the metal. Here, force-fit and form-fit connected components are produced and crushed in a rotor impact mill with two different rotors. The results show that the crushing results differ significantly for the different rotors and for the various joining processes. In short, the hammer-type rotor provides much finer and better-separated fragments and the force-fit joints enable a better separation of metal and polymers. The additional cooling of the samples also changes the result in a way, where deep cooling significantly improves the separation of the metal and the polymer. Different types of polymers also led to a different separation result with both rotors. [ABSTRACT FROM AUTHOR]

Purpose: Misalignment is one of the serious faults that occur in rotating machinery. This fault may be caused by the offset between the axis of the supported shaft and the bearings axis or the offset between two coupled shafts. Excessive vibration can be developed in the machines due to the misalignment fault, which can result in the breakdown of the complete machine. Therefore, there is a need to explore and analyze the vibrational behavior of a faulty rotor-bearing system and identify the fault for the untroubled performance of machines. Methods: An innovative virtual trial misalignment approach based on trial bias current is proposed to study the dynamics of an unbalanced rigid rotor misaligned with the supported active magnetic bearings and eddy current proximity displacement sensors. The same approach has been also utilized to identify the residual offset amounts of displacement sensors located at active magnetic bearing locations. Results: Numerical results are obtained by solving the system's equations of motion on SIMULINKTM platform. The results demonstrate that the displacement and current signals are sinusoidal in nature due to the presence of unbalanced force. Moreover, the size of orbital responses gets enhanced with increments in the misalignment level and noise signal errors. The virtual trial misalignment strategy could also identify the offset amounts of sensors. Conclusions: This paper proposes a virtual trial misalignment approach to analyze the effects of unbalance and AMBs as well as sensor residual misalignments on rotating machinery integrated with active magnetic bearings. For executing this motive, a rigid rotor linked with two discs (at offset positions) mounted on two misaligned AMBs at the end locations is considered and mathematically modeled. The dynamic effect of AMB and sensor residual misalignment on the vibrating nature of the rotor is presented for different misalignment levels, at a single spin speed of the rotor as well as ramp-up speed. The residual misalignments of eddy current proximity sensors are also identified with the help of mathematical modeling of misaligned sensors and virtual trial misalignments of the rotor. The proposed method is found to be more reliable and efficient as compared to traditional approaches for the identification of faults. [ABSTRACT FROM AUTHOR]

Purpose: The two main methods under use for balancing of flexible rotor know as Influence Coefficient Method (ICM) and Modal Balancing Method (MBM). It needs few trials to arrive at predicting the unbalance mass. In presence of initial bow along with unbalance these methods will fail to give accurate predictions. It becomes further complex when rotors are mounted on flexible supports. To overcome the limitations of these two methods, a new method called response matching method is disused here for flexible rotor balancing. Method: The objective of present work is to develop a balancing procedure for flexible rotor balancing, wherein unbalance response of Finite element model (FEM) is matched with experimental response using iterative technique. Unbalance masses, moments and shaft stiffness of FEM model was iterated to match experimental unbalance responses at three distinct speeds below its first flexural critical speed. Further, unbalances mass was estimated iteratively to cross the bending critical speed with lower residual amplitudes at critical speeds. Results: Experimental test setup was developed to validate the proposed method. Results show that present method predicts the unbalance masses and moments to compensate the bow more accurately. Conclusion: Results shows that with single run, rotor unbalance masses and movements are predicted accurately. Corrected masses are used in experimental test setup to check the rotor amplitudes during its bending critical speeds. It shows rotor passes first bending critical speed without excessive amplitudes. [ABSTRACT FROM AUTHOR]

Rotor structure has a great influence on the gas backflow in a screw vacuum pump. The characteristics of the gas main flow along the spiral groove of the screw rotor and the gas reverse flow along the tooth-shaped, tooth side, radial, and circumferential clearances are investigated. A new mathematical model of the pumping flow and backflow involved in a flow balance model is proposed to investigate the actions of the shearing force and pressure difference force. The calculated backflow is verified by comparing the experimental measured results. The relationships of the structural parameters of the screw rotor are established. The effects of the rotor parameters, such as pitch, diameter, and compression ratio, on backflow are revealed. The results show that the rotor diameter and compression ratio remain constant and that the influence of pitch on the backflow is slightly weak, with backflow variations of less than 3%, whereas the pitch, rotor length, and compression ratio are constant and the rotor addendum diameter is directly proportional to the backflow. The addendum diameter of rotor #4 is the largest, and its backflow is about 1.5 times larger than that of rotor #1. When the rotor radial sizes and the pitch of the suction end are constant, the compression ratio is inversely proportional to the backflow in the low-pressure region and proportional to the backflow in the high-pressure regions. Therefore, for a vacuum pump operating in low-pressure areas, the use of the compression ratio of 2.2 or higher is favorable for the reduction in backflow. [ABSTRACT FROM AUTHOR]

Rotors of steam turbines in power plants can be locally deformed by undesired situations, such as rubbing between the rotors and stationary parts. A straightening process is required to correct bending without causing additional damage because a rotor bending displacement of ∼0.15 mm can stop turbine unit operation. In this study, a numerical framework was established to simulate the straightening process using electromagnetic induction heating, which is straightforward and economical among the methods for straightening bent rotors. The straightening process involves complex coupling of electromagnetic, thermal, and mechanical phenomena. For efficiency, sequential coupling was used in the simulations, dividing the multiphysics phenomena into electromagnetic–thermal and thermal–mechanical fields. The temperature distributions resulting from electromagnetic induction heating were calculated through two-way coupling of the electromagnetic–thermal analysis. The thermal deformations of the rotors were obtained by solving the coupled equations for the thermal field obtained from the electromagnetic–thermal analysis and the mechanical field. Using the established numerical framework, the thermal–mechanical behaviors and straightening mechanisms of bent rotors were investigated. Furthermore, the effects of process parameters, including the direction of gravity and heating and cooling conditions, on the straightening performance were determined. Appropriate parameters were identified to achieve the desired straightening performance with final bending displacements of <0.1 mm for bent rotors with initial bending displacements of 0.15–0.3 mm. For a rotor made of A182 F11 Class 2, the best straightening performance was obtained by heating the rotor to a maximum temperature of 650 °C for 20 h under insulation, followed by natural cooling. The simulation results revealed that the straightening performance can be improved when the rotor is rapidly heated to a high maximum temperature and cooled immediately, as long as the temperature conditions do not cause phase transformation or unintended plastic deformation of the bent rotors. [ABSTRACT FROM AUTHOR]

Although annular centrifugal contactors (ACCs) have been widely applied, their complex operation and its dependence on operational variables are still not fully quantified. That hinders their acceptance and precludes revealing their potential. Intuitive techniques to informedly operate ACCs while maximizing their gain are thus demanded. This work introduces a procedure to define the operation window of an extraction task on ACCs, using CINC V 02 variant, that demonstrates the feasible ranges of the operational variables and the maximum possible throughput. The overlapping impacts of the variables are also visualized, thus understood and, to enhance practicality, the procedure is converted into user‐interface software. The concept is intended to adapt to any task on ACCs and it is based on merging a hydraulic part focusing on the rotor and a statistical one modeling the annulus mass transfer. Additional insights on ACC's hydraulics and mass transfer dynamics are presented, including the time needed to establish the steady state. [ABSTRACT FROM AUTHOR]