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Assembly errors can lead to the eccentricity of rotors, further resulting in angular misalignment of rotors and inducing some secondary misalignments, such as the angular misalignment of gears and tilt misalignment of the inner ring of bearings (TMIRB). Ultimately, these misalignments can lead to rubbing faults. However, these misalignments have not raised significant concern, this article investigates their influence on the vibration responses of a dual-rotor-gear-bearing system with rubbing. First, a finite element model (FEM) of the system is built by using an in-house beam element code, and the nonlinear force model of the bearing is established based on the Hertz contact theory. Then, a new model to simulate angular misalignment of gears is proposed by changing the time-varying meshing stiffness (TVMS). Furthermore, the nonlinear dynamic characteristics of the system are investigated in detail under different misalignment angles and rotating speeds, and some interesting conclusions are summarized as follows. Specifically, analyses of the spectrum cascade of radial and axial responses reveal the presence of rich multi-time frequencies and combined frequencies. Moreover, as the misalignment angle increases, the system experiences partial rubbing, the rotating speed threshold (RST) corresponding to initial rubbing decreases, and the mesh stiffness of gears decreases. In summary, the proposed model and the results of the analysis offer valuable insights into the vibration characteristics of such systems and these findings can be instrumental in optimizing their design and operation. [ABSTRACT FROM AUTHOR]

AbstractModern helicopter rotor blades are made of composite materials. Due to the harsh service environment, the blades may be impacted by hail and other falling objects at low velocity. The damage behavior of composite rotor blades subjected to low-velocity impact is studied here. Low-velocity impact experiment is conducted on a composite helicopter rotor blade, and the impact force and the damage are measured. Based on the experiment, a finite element model is developed and validated to predict the impact damage of the blade. With the model, a parametric study is performed to investigate the effects of impact energy, impact locations, and foam core on impact responses of the composite blades. The results show that the rib is the most vulnerable part to damage, associated with severe deformation, and delamination rapid expanding under low-velocity impact. The foam crush region is close to the blade top surface below the impact point. The interface between the skin and internal part is especially sensitive to increase in impact energy. Impacts near the leading edge produce higher impact force, while impacts near the trailing edge cause large deformation and small impact force. Better impact performance will be achieved when modulus and density of the foam are increased. [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]

In this work, the dynamic responses of an uncertain flexible shaft-disk-drum rotor under elastic support and connection are investigated, where uncertain parameters are considered as unknown but bounded interval variables. The energy method is used to derive deterministic analytical model for the flexible shaft-disk-drum rotor, which is validated by modal tests. A non-intrusive interval method based on Chebyshev polynomial approximation is introduced to evaluate the uncertain dynamic response of the flexible shaft-disk-drum rotor system. Comparative studies of Monte Carlo simulation, scanning method and the interval method are conducted to illustrate the validity and accuracy of the approach proposed here. [ABSTRACT FROM AUTHOR]

In high-speed electrical machines (HSEM), mechanical vibration associated with critical speeds of rotor systems can be detrimental to the machine operational stability, especially for vibration near resonances. The structural sizing of a rotor system is often constrained to its mechanical parameters, such as its overall weight, maximum torque, and rated power, which complicate the design, necessitating an iterative design optimization process. This work presents a systematic and iterative rotor structural sizing optimization methodology that incorporates semi-analytical and numerical modeling, specifically taking into account multiple mechanical design parameters from the static, rotordynamic, and electromagnetic-thermal evaluation. The proposed methodology provides an effective design optimization procedure for a general application of HSEM to accelerate its design process, by which the power density and the dynamics stability during high-speed operation are optimized simultaneously. A parametric analysis was carried out where a 24-kW, 12,000-rpm aviation starter-generator was optimized. It was demonstrated that the power density of the machine could be increased by 14.7% from 2.3 to 2.6 kW/kg, while the critical speed was increased by 128.6% from 1,400 to 3,200 Hz. [ABSTRACT FROM AUTHOR]

This paper presents motion planning strategies that assure stable hovering for a transformable unmanned aerial vehicle (UAV) throughout its transformation. The considered multirotor UAV consists of multiple links equipped with rotors. The UAV can transform its structure by changing the lateral joint angle connecting these links. We first introduce the concept of hoverability, which assures static hovering with a linear state feedback controller. Because the hoverability can be evaluated quantitatively by utilizing a convex hull yielded by the positions of rotors, we propose motion planning methods that leverage the hoverability to achieve transformation while guaranteeing stable hovering with desired margin. As the hoverability can be investigated geometrically without analyzing the dynamics of UAVs, the proposed method can be readily employed for a wide class of transformable UAVs, including the one in which clockwise and counterclockwise rotors are not arranged alternately. The proposed motion planning is designed to secure the specified threshold for hoverability and avoid interferences between links or rotors. We then present two types of costs for motion planning: one minimizes the transformation duration, and the other maximizes the hoverability during the transformation. The proposed motion planning is optimized via Dijkstra's algorithm and demonstrated in simulation. [ABSTRACT FROM AUTHOR]

The present study investigates vibrational behavior of a porous conical hollow rotor. Inner and outer rotor surface, sensor, and actuator strips made of piezoceramic are modeled and positioned, which are symmetrically distributed in the circumferential direction. Kinetic and potential energies were computed considering the effects of Coriolis and centrifugal force. Modeling of the system has been carried out assuming classical theory and using Lagrange approach for simple-supported boundary conditions. Also, the relations of piezoceramic and three types of porosity attend in equilibrium equations. The discretization of kinetic and potential energies using displacement field which is defined as double mixed series based on independent mode shape and time function leads to obtaining the equations in form of ordinary differential. To calculate the natural frequencies, the equations were converted to a special form of state space model. The correctness of the study is examined by comparing it with similar study results. The most consequential parameters affecting the forward and backward natural frequency, such as type and porosity coefficient, size, number, and thickness of piezoceramic, and the rotor angular velocity, are researched. The results demonstrate that the effect of porosity coefficient in various longitudinal modes on natural frequency is different. [ABSTRACT FROM AUTHOR]

The application of the Darrieus rotors in regions with lower wind potentials is one of the challenging issues in the operation of this type of vertical axis wind turbine (VAWT). To overcome this problem, various combinations of Darrieus and Savonius rotors, called the hybrid rotor, are proposed, which is one of the attractive subjects among wind turbine researchers. Using the computational fluid dynamics technique (CFD), this study investigates a new combination between the Savonius and Darrieus rotors at which a two-bladed Bach-type rotor is attached inside a two-bladed Darrieus rotor made by NACA 0018. In this way, various attachment angles (α) between the internal and external rotors such as 0°, 45°, and 90° are studied to find the optimal case. Computations are performed for various tip speed ratios (TSR) such as 1.5, 2.5, and 3.5, and free-wind speeds (U∞) of 5 and 10 m/s. The obtained results revealed that the application of a hybrid wind turbine is more beneficial under lower TSR and U∞ values. Additionally, it is demonstrated that the case with α = 90° is the optimal case in TSR = 1.5 and 2.5 providing a maximum 21.43% improvement in comparison to the Darrieus rotor for TSR = 1.5 and U∞ = 5 m/s. [ABSTRACT FROM AUTHOR]

In January 1940, the U.S. Coast Guard intercepted numerous messages that were encrypted on a commercial Enigma D machine using the same key. By solving these messages in depth and examining the resulting cipher alphabets for each position of the rotors, the Cryptanalytic Unit, headed by Elizebeth Smith Friedman, was able to recover the wiring of two of the rotors. This paper explains Friedman's methods in detail and uses them to determine the wiring of two rotors from an Enigma M3 machine. [ABSTRACT FROM AUTHOR]

The Savonius rotor is a type of vertical-axis wind turbine that utilizes drag to generate power. Its design simplicity and ability to self-start at low wind speeds make it an attractive option for small-scale wind energy generation. Previous research has focused on optimizing the geometric configuration of a 1-stage, 2-bladed rotor with semicircular blade profiles to improve its performance and mitigate negative torque. However, limited research has been conducted on 2-stage, 2-bladed Savonius rotors with elliptical blade profiles. The present investigation aims to fill this research gap by evaluating the aerodynamic characteristics of a 2-stage, 2-bladed Savonius rotor with elliptical profiles. 3D unsteady simulations using the SST k-ω turbulence model in ANSYS Fluent are conducted to evaluate the performance coefficients over a range of tip speed ratios. The numerical results are validated through wind tunnel experiments. The results show that the CPmax (maximum power coefficient) for the 1-stage rotor is 0.19 and 0.12 for numerical and experimental analyses, respectively. For the 2-stage rotor, the CPmax is 0.21 and 0.17 for numerical and experimental analyses, respectively. These findings suggest that the 2-stage rotor with elliptical profiles has the potential to efficiently harness wind energy. [ABSTRACT FROM AUTHOR]

SRMs have high torque ripples. Modifying the stator and rotor shape of SRMs is one of their methods to remove torque ripples. In this study, new rotor and stator geometries have been proposed for SRM. Performance characteristics are obtained and dynamic analyses are carried out for both novel and classical 6/4 SRMs. FFT analyses of the torque characteristics are also performed for the both SRMs. The changes in performance and the FFT results of torque characteristics are determined for both the current-controlled and uncontrolled operations in both SRMs. 23.60% and 15.20% improvements in torque ripples are achieved for the uncontrolled and current-controlled operations in SRMs respectively. When the FFT analyses are applied to the torque characteristics, the THD values are obtained as 21.19% and 8.31% in the uncontrolled and controlled motor current operations respectively. A 122 W three-phase 6/4 SRM simulation based on the MATLAB–SIMULINK environment is performed to validate the improvement of the torque ripple of the proposed model. [ABSTRACT FROM AUTHOR]

Hot deformation of 12%Cr USC rotor steel was investigated by hot compression testing over a temperature range of 900 °C to 1,200 °C at strain rates of 0.001 s−1–1 s−1 with the use of a Gleeble–1500D thermal-mechanical simulator. The true stress–strain curves were obtained and showed that the stress increased with a decrease in temperature, an increase in strain rate, or both. Based on the stress–strain curves, processing maps of 12%Cr USC rotor steel under various strains were established, and the Zener-Hollomon (Z) parameter was calculated, it increased with decreasing temperature or increasing strain rate. Combining the values of the Z parameter and the microstructure after thermal compression, it was found that dynamic recovery was the main softening mechanism at lnZ > 39.09, and dynamic recrystallisation (DRX) became the main softening mechanism at 39.09 > lnZ > 32.56. When lnZ < 32.56, DRX occurred completely, and a small amount of recrystallised grains formed. The deformed microstructures showed that 12%Cr USC rotor steel incurred a continuous dynamic recrystallisation mechanism, a discontinuous dynamic recrystallisation mechanism, and a geometric dynamic recrystallisation mechanism during the hot deformation process. The intrinsic workability of 12%Cr USC rotor steel was explored by analysing the processing maps. It was found that the best forging process parameters range of the material in the actual production process was a deformation temperature range of 1,100 °C to 1,200 °C and a strain-rate range of 0.01 s−1–0.1 s−1. [ABSTRACT FROM AUTHOR]

Wear at the inner surface of the rotor cup by granular impurities could adversely affect the slip of fibers and increase yarns' hairiness. Therefore, understanding the mechanism of wear formation due to the moving granular impurities and the wear characteristics at the inner surface of the rotor cup is of great significance for the improvement of yarn quality. This paper numerically explores the mapping relationship between the motion characteristics of particles (i.e. spherical impurities) and the wear characteristics of the rotor cup via the combination of computational fluid dynamics (CFD) and the discrete element method (DEM). The simulation results are first validated against the experimentally obtained microscopic view of the surface of the discarded rotor cup. After that, the wear characteristics of the rotor cup under different rotating speeds and angles of the transfer channel are analyzed. The results show that the most serious cutting and impact wear is found at the rotor groove, followed by the first collision position of the slip surface. The cutting and impact wear in the rotor groove are positively correlated with the rotating speed, while are not affected by the angle of the transfer channel. The cutting and impact wear at the first collision position of the slip surface are negatively correlated with the rotating speed and the angle of the transfer channel. However, the impact and cutting wear at the first collision position is no longer affected significantly by the rotating speed when it is above 90000 rpm. Increasing the rotating speed and the angle of the transfer channel is found to reduce the second wear area on the slip surface of the rotor cup. [ABSTRACT FROM AUTHOR]

Large Eddy Simulations (LES) are performed to study the vortex characteristics in a rotating rotor cup of rotor spinning. The instantaneous evolution process of vortex in the cup is analyzed, and the effects of rotor speed, slip surface angle, and rotor diameter on the airflow field in the rotor cup are examined. The numerical results show that vortices mainly concentrate at the outlet of the transfer channel, which may be due to the collision between the high-speed air stream from the transfer channel and the rotating wall. The strengths of these vortices gradually decrease as they are transported downstream due to the rotating of the cup. To analyze the impact of the parameters on the airflow field and yarn formation, a vortex area ratio (S) is defined which characterizes how much the rotor cup is occupied by vortices. A larger S value usually means a more chaotic and less structured flow field, thus is undesired for the spinning as it may adversely affect the slip and assemble of fibers in the rotor cup. Our parametric study indicates that the largest S value is found at 80,000 rpm for a 50 mm-rotor with a slip surface angle of 68 °. A rotor speed close to this thus may be unfavorable in spinning according to our criterion. For a rotor speed of 100,000 rpm and a diameter of 50 mm, the optimal slip surface angle is found to be about 64 ° , which brings a smallest S value. For a rotor speed of 100,000 rpm and a slip surface angle of 68 ° , the S value is observed to drop dramatically when the rotor diameter reaches 60 mm, a large enough rotor cup thus can efficiently alleviate the chaotic level of the airflow field. The numerical results may provide a preliminary guideline for the choice of spinning conditions that would be better for rotor spinning. [ABSTRACT FROM AUTHOR]

The present work focuses on the rotor dynamic properties of a 650 W roof-top horizontal axis windturbine (HAWT) rotor supported by radial permanent magnet bearings (PMBs). Radial PMBs were designed and optimized concerning the rotor of a wind turbine for maximum stiffness. Initially, a generalized design and optimization process for multi-ring radial PMBs (MrRPMBs) with a radial air gap is presented to get the maximized force and stiffness per magnet volume. The proposed mathematical model is validated using the Finite Element (FE) analysis tool Ansys for chosen rotor dimensions. Then, the same optimization technique was extended for HAWT rotor bearings to extract the optimized multi-ring radial bearing parameters. The dynamic investigation is performed to study the effect of bearing parameters on the rotor-bearing modal frequency and dynamic amplitude of a rotor. Firstly, the dynamic investigation was performed for the conventional deep groove ball bearings (DGBs) supported rotor, considering the effect of bearing span length. Secondly, the dynamic response was analyzed for the rotor system through a hybrid bearing set (HBS) by replacing DGB with PMB. Finally, DGBs are completely replaced by radial PMBs. FEanalysis was performed using the Ansys workbench rotor dynamic tool for all the bearing combinations. [ABSTRACT FROM AUTHOR]

A partitioned solution approach for the fluid-structure interaction (FSI) simulations of turbo machine rotors is presented. The in-house developed boundary element method solver panMARE is used for the fluid simulation, while the structural side is treated with the commercial finite element method solver ANSYS. The generic in-house multiphysics coupling library comana is used for the management of the implicit coupling procedure. As the first example, the KRISO container ship propeller is considered. The simulation is validated for open water test conditions assuming a rigid propeller based on the thrust and torque coefficients. Simulation results for a flexible propeller in open water are also presented. In the second example, the validation of the FSI simulation is conducted for a multilayered flexible submersible mixer based on thrust and torque coefficients and local strains. The results show a good agreement between the simulations and the experimental data for both examples. [ABSTRACT FROM AUTHOR]

This paper presents a novel structure for a quadrotor, making it hover only with clockwise rotors, where we denote it as a 4P (Positive) rotor. We first investigate the condition for a 4P rotor to hover. More specifically, we conduct the hoverability analysis, which is closely related to the controllability analysis, and show that the tilting angles of each rotor are crucial conditions for the hoverability of the 4P rotor. The derived condition for the tilting angles is then utilized to present two prototypes. Each prototype is developed with the following design purposes: One is to reduce the horizontal force generated by the tilted rotors, and the other is to make its torque generation the same as that of a standard quadrotor. The hoverability and dynamical property of both prototype is demonstrated in simulations and experiments. [ABSTRACT FROM AUTHOR]

This paper presents a hybrid method, validated through a series of experiments for balancing of rigid and flexible rotors at a constant rotational speed. Unlike existing balancing methods, this hybrid method combines the benefits of the 4-runs method and the Influence Coefficient (IC) method without requiring a response phase measurements to estimate three correction weights so as to minimise rotor balancing errors. The proposed method requires three trial runs without phase measurements to localise the position of unbalance using the centroid concept. Then, calculating the phase angles of each trial run to apply, three times, the IC balancing method. Finally, estimating the overall corrective weight from these three correction weights. A comparative study was used to verify the reliability of this hybrid method as a contrast test. Additionally, two experimental cases were designed to evaluate the method in two different operating environments. Experimental analyses show that the proposed method presents acceptable results, despite the use of a modest instrument such as the smartphone to acquire the vibration signal of the unbalanced rotor. In this context, this paper highlights the opportunities behind smartphones, which can be a reliable tool to perform professional operations such as field balancing for rotating machinery. [ABSTRACT FROM AUTHOR]

Vibration is the vital feature of the motor to diagnose various faults. The existing methods have many limitations. This work proposes a non-invasive Software Phase Locked Loop (SPLL) technique to diagnose the multiple rotor faults. A high-frequency (10.525GHz) microwave signal is projected on the motor and the reflected signal is captured by the handheld ultra-wide band (UWB) radar. Hardware filter is replaced by a software phase locked loop filter to remove high-frequency noise content in the signal. The output of the SPLL is analysed with Rational Dilation Wavelet Transforms (RDWT) and compared the change in the signal energy of the wavelet sub-band 6 for the multiple rotor bar faults and sub-bands 6 and 7 for the combination of rotor bar and bearing faults, respectively. The signal energy at sub-band 6 increased from 2.19% without fault to 3.99%, 6.03% and 13.66% with an increase in the number of rotor bars with faults. The variation of the experimental values of the signal energy for rotor bar faults compared with the theoretical values found that the error is reduced and accuracy is increased with the number of faults. For simultaneous rotor bar and bearing faults, the signal energy at sub-bands 6 and 7 also increases. The proposed SPLL-based method that is able to diagnose the individual faults and combination of the faults and has advantages such as simple, cost-effective and non-invasive technique compared with the existing methods. [ABSTRACT FROM AUTHOR]

The paper presents a critical analysis of the procedures for defect propagation assessment recommended by British standards and their application to rotating components. The way of applying these procedures was shown by an example of a steam turbine rotor with particular use of a characteristic strain model of high-temperature creep. Calculations of the flaws located at the rotor axis have shown that their growth in the design life is small. The performed analyses have also shown that crack development due to low-cycle fatigue is comparable to that due to creep and cannot be ignored under typical service condition. It was also shown that there is no risk of brittle fracture in the rotor under typical start-up conditions. The presented results prove the usefulness of the methods included in the British standards and guidelines for crack growth assessment in components subject to centrifugal load. [ABSTRACT FROM AUTHOR]

Knowledge of the load parameters of wind turbine rotor is the key problem to eliminate the misalignment of wind turbine. In this paper, an inverse method for identifying the load parameters with imprecise information is investigated by using the probability and interval variables. The interval variables are dealt with interval analysis, only the bounds of the structure response are needed avoiding time-consuming inner loop for structure response prediction. The probability variables are dealt with a proposed iteration method combined micro genetic algorithm with the search interval advance and retreat method. Firstly, at the midpoint of the interval variables, the mean of the load parameters is identified based on the proposed iteration method; secondly, the first-order Taylor expansion is employed to gain the boundary of rotor dynamic response from predicting structure response strip derived from the existence of interval variables; thirdly, the interval of the load parameters is identified via the boundary of rotor dynamic response based on the proposed iteration method. Eventually, the accuracy and efficiency of the proposed inverse method are verified by one numerical example. [ABSTRACT FROM AUTHOR]

To achieve fast, accurate control of the position angle of the rotor of permanent magnet synchronous motor (PMSM), traditional auto disturbance rejection control often has many adjustable parameters and complex tuning problems. Sliding mode control technology is introduced into the extended state observer (ESO) part of the auto disturbance rejection controller, and a new sliding mode approach law is designed based on several typical sliding mode approaches, which simplifies parameter tuning while retaining the original anti-interference performance of auto disturbance. In addition, the nonlinear state error feedback control law in active disturbance rejection control is enhanced to improve the component order PID control law, which can improve the response speed and robustness of the system, and prove the stability of the controller. Finally, the simulation of the PMSM rotor position control system based on the sliding mode ESO is carried out, and the results verify the validity of the method. [ABSTRACT FROM AUTHOR]

In this paper, the giant magnetoresistance broken rotor (GBR) method is used to diagnose the induction motor (IM) rotor bar fault at an early stage from outward magnetic flux developed by IM.The outward magnetic field signal has anti-clockwise radiation due to broken rotor bar current.In this paper, the outward magnetic signal is acquired using a giant magnetoresistance (GMR) sensor. In the GBR method, IM rotor fault is analysed with a non-decimated wavelet transform (NDWT)-based outward magnetic signal. Experimental result shows the difference in statistical features and energy levels of sub-bands of NDWT for healthy and faulty IM. Least square-support vector machine(LS-SVM)-based classification results are verified by confusion matrix based on 150 outward magnetic signals from a healthy and damaged rotor (broken rotor). The proposed method identifies IM rotor faults with 95% sensitivity, 90% specificity and 92.5% classification accuracy. Furthermore, run-time IM condition monitoring is performed through the ThinkSpeak internet of things (IoT) platform for collecting outer magnetic signal data. ThinkSpeak streaming data of outward magnetic field help detect rotor fault at the initial stage and understand the growth of rotor fault in the motor. The proposed GBR method overcomes sensitivity, translation-invariance limitations of existing IM rotor fault diagnosis methods. [ABSTRACT FROM AUTHOR]

In this article we study the quality of permutations in historical cipher machines from Germany, Spain, Italy, Norway, Switzerland, Japan, Hungary, Croatia, Poland, Czechoslovakia, Russia and the United States. We show that numerous real-life rotors have been made in order to imitate or tend to a certain ideal property related to latin squares. Rotors from the same source and the same period have consistent properties deeply rooted in classical cryptography of polyalphabetical ciphers. We demonstrate this based on probabilities: random occurrence of permutations having such features is unlikely, or would amount to winning in a lottery several times in row. We put all this in the context of known historical sources on how cipher machines and cryptanalysis have developed on both German and Allied sides. We also exhibit strong linear and differential properties. The same occurs in Fialka cipher machines. Finally, a stronger property holds for the historical block cipher T-310. [ABSTRACT FROM AUTHOR]

In this paper, a new design scheme for counter-rotating horizontal-axis tidal turbines (CRHATTs) is introduced using blade element momentum (BEM) theory. The coordinated working performance between rotor and generator of the CRHATT are analysed by experimental and CFD methods. The effects of the key parameters on the energy harvesting efficiency of the CRHATT are studied in detail. The study indicates the existence of the optimal rotor solidity (σ) combination and blade installation angle (γ) combination for dual rotors to reduce the power coefficient (Cp) deviation of the dual rotors. The distance between dual rotors (L) is suggested to be set as about 0.225D, which can maximise the Cp of the CRHATT. Finally, the hydrodynamic performance of the flow field is carried out to verify the reliability of the CRHATT design. The results presented in this paper may serve as a reference in the design of CRHATTs in practical engineering. [ABSTRACT FROM AUTHOR]

The current research deals with the possibility of relying on wind energy, specifically Flettner rotors; as a source of ships propulsion to reduce ships' emissions. The paper highlights the technical, environmental, and economic aspects of wind-assisted propulsion systems. As a case study, four Flettner turbines are examined to be used onboard a bulk carrier ship, considering three different routes. Technically, the ship's route and wind characteristics are the focal aspects that affect the output power of Flettner rotors. The economic results indicate that the payback periods for the selected Flettner rotors will be 7, 13, and 11 working years for the first, second, and third ship routes, respectively, with considerable levelised costs of energy. Environmentally, NOx and CO2 emissions will be decreased by 154.3 and 5089 ton per year, for longest route, with cost-effectiveness of 3350 and 89 $ per ton, respectively with a 10 percent interest rate. [ABSTRACT FROM AUTHOR]

The strength of rotor-spun yarns is usually lower than that of ring-spun yarns. One of the major factors which affect the strength is the fiber morphology. Better understanding of the fiber morphology in the rotor cup would help to strengthen the yarn. In this paper, a visual experimental platform is used to study the morphology evolution of the fiber in the rotor. Two parameters S1 and S2 are defined to evaluate the deformation of the fiber. When the values of S1 and S2 decrease, the fiber deformation becomes smaller. While the rotor speed is 60,000 rpm, the outlet velocity is 20 m/s and the angle of the transport channel relative to the rotor is 30°, the fiber has minimal deformation. The results may provide a useful insight to the yarn-forming properties of rotor spinning. [ABSTRACT FROM AUTHOR]

In this paper, numerical simulation of transient thermal and static structural analysis was performed here sequentially with coupled thermo-structural method. Numerical procedure of calculation was based on important steps such as the Computational Fluid Dynamics (CFD) and thermal analysis which were well illustrated in 3D. Two different rotor designs and three different brake disc materials were tested and comparative analysis of the results was here conducted in order to get the one with the best thermal behaviour. The current numerical results were in good agreement with the previous experimental results available in the literature. Finally, the resolution of the thermo-mechanical coupling model allows us to visualise other important results of this research. According to the results presented in this study, several conclusions can be drawn. The choice will allow us to deliver the excellent rotor design to ensure and guarantee the good braking performance of the vehicles. [ABSTRACT FROM AUTHOR]

Rotor slots in induction motor expand due to thermal imbalance and create magnetic stress. Magnetic stress is a force that develops on the laminated surface of the rotor due to the curving or stretching magnetic flux. Traditional motor fault detection methods never measure magnetic stress on the rotor; a significant problem frequently arises in the motor. Magnetic stress is proportional to slot size variations in the rotor. High slot size variations on the laminated surface of the rotor lead to more curving and stretching magnetic flux and damage the rotor and stator, reducing their efficiency and induce harmonics. In this paper, the Average rotor Slot Size Variation (ASSV) in the rotor is predicted during the running condition of the motor through logistic regression. Logistic regression predicts ASSV by multimodal sensor signal sub-band energy values and measures rotor slot sizes from microscope images. Multimodal sensor signal is obtained from various sensors, such as vibration, temperature, current and Giant Magneto Resistance (GMR). Signal sub-band energy is obtained from Over complete Rational-Dilation Wavelet Transform (ORaDWT). From experimental results, ASSV is more than 75% from standard size, damaging the rotor and stator. The accuracy of ASSV prediction is about 92%. [ABSTRACT FROM AUTHOR]

Hydrodynamic coefficients including thrust, torque and efficiency at different advance ratios are investigated for all components of a Linear-Jet propulsion system. Ansys-CFX software is utilised and URANS equations are solved by the SST k − ω turbulent model. Pressure on high- and low-pressure sides of the stator at different spans is computed based on different axial gap size between stator and rotor as well as chord of the rotor in the propulsion system. The computed thrust and torque coefficient as well as efficiency are validated by available experimental data for a ducted propeller. The obtained pressure distribution indicates different fluctuations caused by the interaction of rotor and stator. These oscillations and vibrations are the main cause of damage to the ship hull and the propulsion system. To study these phenomena, unsteady forces applied on the stator at different distances between the rotor and the stator for various time steps are investigated. [ABSTRACT FROM AUTHOR]

We, the Editors and Publisher of the journal Engineering Optimization, have retracted the following article at the request and agreement of the author: Chih-Hong Lin (2020): Mended grey wolf optimization and Taguchi method with multi-goal optimization for six-phase copper rotor induction motor design, Engineering Optimization, DOI: The content of this article contains a high level of similarity with the published article below: Chih-Hong Lin (2020): Altered Grey Wolf Optimization and Taguchi Method with FEA for Six-Phase Copper Squirrel Cage Rotor Induction Motor Design, Energies, 13, 2282, DOI: We have been informed in our decision-making by our policy on publishing ethics and integrity and the COPE guidelines on retractions. The retracted article will remain online to maintain the scholarly record, but it will be digitally watermarked on each page as 'Retracted'. [ABSTRACT FROM AUTHOR]

We, the Editors and Publisher of the journal Engineering Optimization, have retracted the following article at the request and agreement of the author: Chih-Hong Lin (2020): Mended grey wolf optimization and Taguchi method with multi-goal optimization for six-phase copper rotor induction motor design, Engineering Optimization, DOI: The content of this article contains a high level of similarity with the published article below: Chih-Hong Lin (2020): Altered Grey Wolf Optimization and Taguchi Method with FEA for Six-Phase Copper Squirrel Cage Rotor Induction Motor Design, Energies, 13, 2282, DOI: We have been informed in our decision-making by our policy on publishing ethics and integrity and the COPE guidelines on retractions. The retracted article will remain online to maintain the scholarly record, but it will be digitally watermarked on each page as 'Retracted'. [ABSTRACT FROM AUTHOR]

In this paper, an exact solution is presented for whirling analysis of rotors carrying concentrated masses. Effect of various parameters on the forward and backward frequencies are investigated including velocity of spin and quantity, translational inertia and position of the concentrated masses. It is shown that vibration characteristics of rotors can be affected by concentrated elements depended on the position of point masses and value of their translational inertia. The most advantage of the presented solution is that for rotors with any number of concentrated masses, all natural frequencies can be obtained through solution of a determinant of order 2. [ABSTRACT FROM AUTHOR]

Multiple oily wastewaters are necessary for scientific research and technological development. Experimental oily wastewater is prepared with an in-line high shear mixer at a constant flow rate. Rotor speeds have a significant effect on pressure drops across shear mixer, while oil/water ratios have less effect. With the increase of rotor speeds, most of the oil droplet size (D50, D90) show a downward trend. D10 of oil droplets may increase at low oil/water ratios while those decrease at high ones. Oil droplet sizes (D50 and D90) change slowly and emulsibility values decrease with the increase of oil/water ratios, and 0.06% is most favorable for fine emulsion. Higher rotor speeds prepare the turbulent environment easily, and higher oil/water ratios are available to improve droplets coalescence. Rotor stirring changes the drop size, and in turn influences the Zeta potential and stability of the emulsion. As oil/water ratios increase, absolute Zeta potential tends to decrease and coalesce easily. The oil contents of prepared wastewater measured with polyacrylamide addition are more than those without polyacrylamide addition respectively, and all of them are lower than their theoretical counterparts respectively. The results can provide necessary parameter references for the laboratory to prepare the character-specific oily wastewater. [ABSTRACT FROM AUTHOR]

Many efforts have been made to enhance the hydrokinetic turbines' energy efficiency, extracting the energy from the flowing water in the canal and river. Savonius hydrokinetic turbine is one of the turbines producing mechanical power output using renewable energy sources of flowing water. It has good starting characteristics but has low energy efficiency. In the present investigation, an attempt is made toward the enhancement of the energy efficiency and load-carrying capacity of the Savonius turbine. The two dual-rotor Savonius turbine designs with deflector plates are proposed termed as Dual Rotor with Diverging Deflector Plate (DR-DDP) and Dual Rotor with Converging Deflector Plate (DR-CDP). The investigations are carried out with numerical simulations. The experiments are also performed for the validation of the methodology adopted in the presented numerical simulations. The results indicate the improved performance of the turbine units with both deflector plate designs. The power coefficient with the Savonius turbine unit's investigated design is enhanced from 0.135 of the conventional turbine to 0.16 with DR-DDP, and that up to 0.20 with DR-CDP. [ABSTRACT FROM AUTHOR]

A detailed comprehensive study of a proposed V-shaped turbine rotor is performed in order to examine its structural and aerodynamic characteristics. The structural analysis section of this work determined the most structurally sound blade geometry from 3 different blade geometries. Using the chosen blade profile, 8 rotor models are developed and are tested numerically. These rotor models are of different configurations, focusing on an inclination angle of 45 and 60 degrees, blade twist angle of 0 and 5 degrees and number of blades. Four rotor models are taken from the initial tests for further study, 3B45D which is a three-bladed rotor with a 45 degree inclination angle, 5B45D which is a five-bladed rotor with a 45 degree inclination angle, 5B45D (5deg) which is a five-bladed rotor with a 45 degree inclination angle and a 5 degree blade twist angle, and 5B60D which is a five-bladed rotor with a 60 degree inclination angle. From the structural study, blade design 2 held the best structural characteristics. The design showed an excellent Von-Mises at 8.8 MPa for static structural and 22.2 MPa for fatigue stress response which is well below the yield strength of ABS Plastic. Both experimental and numerical data have relatively good agreement that is within 15% difference. Overall, maximum power coefficient achieved in this study is about 0.259 numerically and 0.213 experimentally. The best performance is seen by the 3B45D rotor in both static and dynamic study considering experimental and numerical corroboration of results. [ABSTRACT FROM AUTHOR]

The article presents the results of the analysis of the active control of Stodola-Green rotor, made of a cantilevered beam with a rigid disc attached to its free end. The rotor is of a smart type, with piezoelectric patch sensors and actuators glued to its surface. The aim of active control is to decrease the effective internal damping, thus increasing the range of stable operation. The simulation studies show that it is feasible to increase the range of stability of rotors by means of velocity feedback control. Unlike in most studies that utilize this control scheme, negative gains are used, which allows for the effective internal damping to be decreased. [ABSTRACT FROM AUTHOR]

In this study the nonlinear dynamics of an asymmetrical rotating shaft is investigated. The high-static-low dynamic stiffness are used. Also, the active time-delayed proportional derivative controller is employed to. The control signals include time delays. The effects of the proportional and derivative gains, flexible supports and added damping on the nonlinear behaviors of the system are examined. Also, the influences of the proportional and derivative gains on the critical time delays are investigated. As a result, it can be seen that a proportional derivative controller can decrease the unstable regions, and flexible supports improve the stability conditions of the system. [ABSTRACT FROM AUTHOR]

On-site estimation of multiple fault parameters has been performed in a rotor integrated with active-magnetic bearing (AMB) with a cracked shaft supported on flexible conventional bearings. In addition to external viscous damping (at flexible bearings), internal damping (at transverse crack) is considered to show its influence on the dynamics of the cracked system. The instability generated in the rotor system due to the effect of internal damping at high speed are reduced with the control action of the AMB. A Multiple Harmonic Influence Coefficient Method (MHICM) has been proposed that requires the full spectrum amplitude and phases of the rotor responses and excitation forces to obtain the fault parameters of the rotor. The additive crack stiffness, residual unbalances, and internal damping can be estimated in the operating condition with less information on the rotor system. The intensity of the fault parameters is required to be monitored periodically to identify the safe operating speed of the system. As the AMB is an integral part of the rotor system, the multi-harmonic excitation can be initiated without changing the physical condition of the system. To check the robustness of the algorithm, different percentages of random noise are added to the rotor responses. [ABSTRACT FROM AUTHOR]

The coupled rotor/ship flowfield is investigated using the Navier–Stokes solver when the helicopter rotor hovers in the ship's airwake. The solid rotor model (SRM) and virtual rotor model (VRM) are employed, considering the different types of rotor simulation by the momentum source method. Qualitative and quantitative rotor/ship coupled flowfield analyses are conducted when the rotor hovers at different locations and with different wind-over-deck conditions. The results show that both models effectively reflect the different vortex interactions and velocity distributions in the rotor/ship coupled flowfield, and the discrepancy of velocity magnitudes between the SRM and VRM is kept within 1 m/s under most conditions. Moreover, a comparison is made of computational costs between the SRM with the moving overset mesh method and the VRM during a helicopter vertical shipboard landing. It is shown that the computational time of the VRM is smoother than the SRM by about 10 times. Considering the computational cost, it is more appropriate to use the VRM to conduct coupled flowfield studies in the helicopter/ship dynamic interface. [ABSTRACT FROM AUTHOR]

Design optimization of transonic airfoils for rotary blades is a challenging subject that remarkably affects the stage and overall performance of axial-flow compressors. This paper describes a surrogate-based multi-objective optimization process over a transonic rotary blade. This blade works in the first high-pressure stage of a pre-designed industrial axial compressor. It experiences a massive separation behind an impinging shock wave over its suction side, resulting in very low efficiency of the whole stage. The key components of the current approach involve the application of novel-objective functions over the pressure distribution of airfoils, called the location of the shock wave and a flat-roof-top factor, to design supercritical airfoils. Moreover, to ensure the advantages of having an attached boundary layer and a high efficient blade, the area of separated boundary layer is also defined alongside other well-known objective functions related to the polar loss diagram. Notably, a sequential feed-forward multi-layer perceptron is designed to construct a mapping between airfoil geometrical variables and the objective functions. A numerical simulation of the whole compressor has shown an efficiency improvement of about 10% and 0.17% for the first stage and the whole compressor, respectively, and an attached boundary layer with a supercritical pressure distribution when employing the optimized rotor blade at the design stage. [ABSTRACT FROM AUTHOR]

This study aimed to investigate the effect of geometric characteristics and traffic scenarios on the performance measures, including delay, volume to capacity (v/c) ratio, capacity, and the level of service (LOS) in basic and rotor turbo roundabouts. In addition, it attempted to compare turbo roundabouts using performance measures based on geometric characteristics and traffic scenarios. The results showed that performance measures reduced significantly by increasing the diameter of four-leg turbo roundabouts although they improved in three-leg turbo roundabouts. Further, four- and three-leg basic turbo roundabouts had a better performance by changing the balanced to imbalanced traffic flow scenario compared with four- and three-leg rotor turbo roundabouts. Additionally, substituting four- and three-leg basic turbo roundabouts for rotor four- and three-leg turbo roundabouts increased the performance measures. Overall, the basic turbo roundabouts had a better performance compared to the rotor turbo roundabout under unsaturated and saturated traffic conditions. [ABSTRACT FROM AUTHOR]

The faults diagnosis of Induction Motor (IM) is a required field of the research area grown in recent years. Industrialists and researchers predominately use this interest as a result of improvement in control circuits for IM. This paper proposes a new approach for the detection of Broken Rotor Bar (BRB) fault in a three-phase Induction Motor Drive (IMD) using one of the signals Discrete Wavelet Transform (DWT), where the machine is controlled by Direct Torque Control (DTC). The amplitude and frequency components are extracted by Fast Fourier Transform (FFT), and the DWT decomposes the signal. Energy eigenvalue of stator current of the signal calculates the severity of the fault and gives a better solution for indicating the failure. DTC is adopted for advisable control techniques in the industrial drives system to preserve the excellent performance in variable torque control applications. The effectiveness of the above method is evaluated by using MATLAB/SIMULINK and experimental tests demonstrate the superior performance of the proposed technique. [ABSTRACT FROM AUTHOR]

To improve the calculation accuracy for the mechanics mode of a double-support four-stage centrifugal pump rotor system (FCPRS), a simplified mathematical model derived from "four segments-four concentrations" and an ANSYS model were used to solve the model of a D-type FCPRS with balanced mass. Based on ourresults, we present an improved mathematical model combining "five segments-four concentrations" and the modal resistance-bending stiffness (RBS) correction coefficient. Moreover, the calculation results of the impeller mass eccentricity from the optimized model were compared with those from ANSYS simulations. The natural frequencies (NF) from the concentrated mass method (CMM) are slightly lower than those obtained from ANSYS. After optimization, the errors of the first four orders of NFs decreased from 1.13%, 1.24%, 7.62%, and 7.96% to 0.79%, 0.90%, 4.17%, and 4.51%, respectively. The NFs of each order increase slightly in the case of impeller mass eccentricity. The low-order NF increases slightly and the high-order NF decreases when the impeller in the middle is eccentric. The NF error obtained via the optimized CMM for the impeller with eccentric mass is slightly larger than that for the impeller without eccentricity. [ABSTRACT FROM AUTHOR]

Differences between gas-phase and matrix-isolated rotational and rovibrational spectra of the water molecule are interpreted in term of the confined rotor model. The parameters of this model enable the isotopic composition of the molecule, which has non-trivial impacts on the spectra of matrix-isolated confined rotors, to be taken into account on a very simple and intuitive basis. We use molecular dynamics simulations to systematically explore the effects of the mass distribution of various isotopomers of the water molecule on the coupled rotational and translational dynamics of the confined asymmetric rotor, and on their coupling with the phonons of the argon matrix. Analysis of the trajectories reveals that, depending on the mass distribution, a preferred orientation of the water molecule can be strongly imposed by the topology of its interaction potential with the confinement medium. Features of the confining potential, and of the rotation-translation coupling, are thus revealed from classical molecular dynamics simulations. [ABSTRACT FROM AUTHOR]

Current wind turbine rotor blades have a significant impact on the cost of the turbine, which is mainly a consequence of the manual process steps involved in blade production. The manual, labour-intensive production process leads to high tolerances and requires high safety and reliability factors. Especially in the case of offshore turbines with current and upcoming blade dimensions, automation will make the blades cost effective, quicker to produce and guarantees a higher quality. Here, we analyse the current blade structure and production processes and present a technical review of the existing automation approaches for the textile build-up process in industry and academia. Thereby we classify these approaches according to the different techniques based on the rotor blade structure parts. [ABSTRACT FROM AUTHOR]

A mathematical model is proposed to calculate the total separation effectiveness in terms of GT for a disk stack centrifuge taking account of the variation of the centrifugal force with a position in the disk. In practice, the centrifuge ability/force is often referred as Relative Centrifugal Force (RCF) or G number, which is a multiple of the centrifugal acceleration over the gravitational acceleration. As the radial velocity varies it is important to integrate the relative centrifuge force, here in terms of the G number along the path taking account of the change in velocity. The separation effectiveness, GT is defined as an integrated product of local G number, G(x) and local residential time (dt), where dt is the time taken for the bulk fluid to traverse a distance from r to r+ dr. The GT value calculated for a disk type centrifuge can be compared with the GT value of others and compared with a bench top fixed rotor centrifuge. An industrial centrifuge would be expected to be able to deliver similar separation performance to a pilot or a lab scale one, if operated at the same/similar value of GT. This would allow the performance of a full-scale clarifier to be predicted. This model is, in essence, a simple alternative to the Sigma concept. [ABSTRACT FROM AUTHOR]

Ciphers based on rotor machines were the state-of-the-art in the mid-1900s, with arguably the most famous being the German Enigma. We have found that students have great interest in the Enigma and its cryptanalysis, so we created our own rotor cipher that is simulated with shifting tables and can be cryptanalyzed. Ours and the historic rotor ciphers are based on rotating wheels that change the encryption with each character encrypted. Our cipher is easily programmed or can be simulated in Excel for students with less experience, and its cryptanalysis leads to interesting structure and the re-creation of the rotors. [ABSTRACT FROM AUTHOR]

A 4 degrees of freedom ship performance prediction model is used to compare wind-assisted ship propulsion technologies: the Flettner rotor, a wingsail and the DynaRig concept. An Aframax Oil Tanker on a route between Gabon and Canada is used in a case study to compare the three technologies using actual information for the voyage. The fuel savings for were calculated and they varied between 5.6% and 8.9%; the Flettner rotor showed the largest fuel savings. A parametric study of the Flettner rotor technology was carried out to research how its dimensions and operation conditions for two ship types on two voyages influence the fuel savings. The results show that fuel savings were achieved by several percentages. It is shown that it is necessary to select and operate the Flettner rotor according to its ship type, speed, voyage routes and corresponding weather conditions to achieve as large fuel savings as possible. [ABSTRACT FROM AUTHOR]

In order to balance a rotor, the standard rotor balancing methods involve measurement of vibration amplitude and vibration phase angle. But accurate phase angle measurement is generally difficult because vibration phase is sensitive to speed variations and it is difficult to maintain a constant speed in operating condition. Also, phase angle measurement requires very high end instrumentation for accurate phase angle measurement. Number of trial runs during balancing process also plays an important criterion in deciding the effectiveness of that method. A Method is considered to be more effective if it balances a rotor in less number of trial runs. This paper presents a novel rotor balancing method called amplitude subtraction method in which vibration amplitudes are measured only. Performance of this method is analysed by a comparative study with phase angle based rotor balancing method (trim balancing method). Trim balancing and amplitude subtraction method are compared on the basis of its accuracy and number of trial runs during balancing process. The results of experimentation demonstrate successful implementation of proposed method. [ABSTRACT FROM AUTHOR]