Academic literature on the topic 'Rotori principali'

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Journal articles on the topic "Rotori principali"

1

Zhang, Xiao Long, Ya Bin Dong, Yu Min He, and Mei Juan Tong. "Forced Vibration of Rotor Suppressed by a Automatic Ball Balancer (Nonlinear Principal Resonances)." Advanced Materials Research 655-657 (January 2013): 551–57. http://dx.doi.org/10.4028/www.scientific.net/amr.655-657.551.

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The automatic ball balancer is equipment used to balance the rotor system online and control its forced vibration. Although the rotor system is a nonlinear system actually, especially the occurrence of the nonlinear elastic restoring force in the support of rolling elements bearings, many researches still focus on the linear rotor systems at present. The Jeffcott rotor acted by unsymmetrical nonlinear restoring force is studied in this paper. Through the resolving theoretically and simulating numerically, the principal resonance respond of the rotor system controlled by the balancer with two balls and its stability are studied, while the vibration characteristics and movement laws of the rotor and balls in every rotary speed region are analyzed. The results showed that the balancer can suppress the principal vibration of the nonlinear rotor system in high speed region very well.
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2

Chiang, H. W. D., and S. Fleeter. "Passive Control of Flow-Induced Vibrations by Splitter Blades." Journal of Turbomachinery 116, no. 3 (1994): 489–500. http://dx.doi.org/10.1115/1.2929438.

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Splitter blades as a passive control technique for flow-induced vibrations are investigated by developing an unsteady aerodynamic model to predict the effect of incorporating splitter blades into the design of an axial flow blade row operating in an incompressible flow field. The splitter blades, positioned circumferentially in the flow passage between two principal blades, introduce aerodynamic and/or combined aerodynamic-structural detuning into the rotor. The unsteady aerodynamic gust response and resulting oscillating cascade unsteady aerodynamics, including steady loading effects, are determined by developing a complete first-order unsteady aerodynamic analysis together with an unsteady aerodynamic influence coefficient technique. The torsion mode flow induced vibrational response of both uniformly spaced tuned rotors and detuned rotors are then predicted by incorporating the unsteady aerodynamic influence coefficients into a single-degree-of-freedom aero-elastic model. This model is then utilized to demonstrate that incorporating splitters into axial flow rotor designs is beneficial with regard to flow induced vibrations.
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3

Lanchares, V., M. Iñarrea, and J. P. Salas. "Spin Rotor Stabilization of a Dual-Spin Spacecraft with Time Dependent Moments of Inertia." International Journal of Bifurcation and Chaos 08, no. 03 (1998): 609–17. http://dx.doi.org/10.1142/s0218127498000401.

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We consider a dual-spin deformable spacecraft, in the sense that one of the moments of inertia is a periodic function of time such that the center of mass is not altered. In the absence of external torques and spin rotors, by means of the Melnikov's method we prove that the body motion is chaotic. Stabilization is obtained by means of a spinning rotor about one of the principal axes of inertia.
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4

Viswanathan, R., and S. M. Bruemmer. "In-Service Degradation of Toughness of Steam Turbine Rotors." Journal of Engineering Materials and Technology 107, no. 4 (1985): 316–24. http://dx.doi.org/10.1115/1.3225825.

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The toughness of steam turbine rotors degrades with time of service exposure in the range of 340°–540°C. There is a need to estimate the toughness degradation that has occurred in order to assess the reliability, remaining life, and further operational parameters for the rotors. Since it is not possible to take large specimens from operating rotors to evaluate the rotor toughness, nondestructive or relatively nondestructive techniques involving removal of small samples are needed. To serve this need, several techniques such as composition based correlations, grain boundary analysis by Auger electron spectroscopy, analytical electron microscopy, and secondary ion mass spectroscopy, chemical and electrochemical etching, eddy current measurements and mechanical testing of miniature samples have been explored by the electric power industry. This paper presents an overview of the principal results emerging from the various on-going projects in this area.
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5

Bejaoui, Islem, Dario Bruneo, and Maria Gabriella Xibilia. "Remaining Useful Life Prediction of Broken Rotor Bar Based on Data-Driven and Degradation Model." Applied Sciences 11, no. 16 (2021): 7175. http://dx.doi.org/10.3390/app11167175.

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Rotating machines such as induction motors are crucial parts of most industrial systems. The prognostic health management of induction motor rotors plays an essential role in increasing electrical machine reliability and safety, especially in critical industrial sectors. This paper presents a new approach for rotating machine fault prognosis under broken rotor bar failure, which involves the modeling of the failure mechanism, the health indicator construction, and the remaining useful life prediction. This approach combines signal processing techniques, inherent metrics, and principal component analysis to monitor the induction motor. Time- and frequency-domains features allowing for tracking the degradation trend of motor critical components that are extracted from torque, stator current, and speed signals. The most meaningful features are selected using inherent metrics, while two health indicators representing the degradation process of the broken rotor bar are constructed by applying the principal component analysis. The estimation of the remaining useful life is then obtained using the degradation model. The performance of the prediction results is evaluated using several criteria of prediction accuracy. A set of synthetic data collected from a degraded Simulink model of the rotor through simulations is used to validate the proposed approach. Experimental results show that using the developed prognostic methodology is a powerful strategy to improve the prognostic of induction motor degradation.
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6

Parish, D., and D. G. MacManus. "Aerodynamic investigations of ventilated brake discs." Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering 219, no. 4 (2005): 471–86. http://dx.doi.org/10.1243/095440705x11121.

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The heat dissipation and performance of a ventilated brake disc strongly depends on the aerodynamic characteristics of the flow through the rotor passages. The aim of this investigation was to provide an improved understanding of ventilated brake rotor flow phenomena, with a view to improving heat dissipation, as well as providing a measurement data set for validation of computational fluid dynamics methods. The flow fields at the exit of four different brake rotor geometries, rotated in free air, were measured using a five-hole pressure probe and a hot-wire anemometry system. The principal measurements were taken using two-component hot-wire techniques and were used to determine mean and unsteady flow characteristics at the exit of the brake rotors. Using phase-locked data processing, it was possible to reveal the spatial and temporal flow variation within individual rotor passages. The effects of disc geometry and rotational speed on the mean flow, passage turbulence intensity, and mass flow were determined. The rotor exit jet and wake flow were clearly observed as characterized by the passage geometry as well as definite regions of high and low turbulence. The aerodynamic flow characteristics were found to be reasonably independent of rotational speed but highly dependent upon rotor geometry.
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7

Hansen, Morten Hartvig. "Modal dynamics of structures with bladed isotropic rotors and its complexity for two-bladed rotors." Wind Energy Science 1, no. 2 (2016): 271–96. http://dx.doi.org/10.5194/wes-1-271-2016.

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Abstract. The modal dynamics of structures with bladed isotropic rotors is analyzed using Hill's method. First, analytical derivation of the periodic system matrix shows that isotropic rotors with more than two blades can be represented by an exact Fourier series with 3/rev (three per rotor revolution) as the highest order. For two-bladed rotors, the inverse mass matrix has an infinite Fourier series with harmonic components of decreasing norm; thus, the system matrix can be approximated by a truncated Fourier series of predictable accuracy. Second, a novel method for automatically identifying the principal solutions of Hill's eigenvalue problem is introduced. The corresponding periodic eigenvectors can be used to compute symmetric and antisymmetric components of the two-bladed rotor motion, as well as the additional forward and backward whirling components for rotors with more than two blades. To illustrate the use of these generic methods, a simple wind turbine model is set up with three degrees of freedom for each blade and seven degrees of freedom for the nacelle and drivetrain. First, the model parameters are tuned such that the low-order modal dynamics of a three-bladed 10 MW turbine from previous studies is recaptured. Second, one blade is removed, leading to larger and higher harmonic terms in the system matrix. These harmonic terms lead to modal couplings for the two-bladed turbine that do not exist for the three-bladed turbine. A single mode of a two-bladed turbine will also have several resonance frequencies in both the ground-fixed and rotating frames of reference, which complicates the interpretation of simulated or measured turbine responses.
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8

Ur Rahman, Lutf, Faisal Khan, Muhammad Afzal Khan, et al. "Modular Rotor Single Phase Field Excited Flux Switching Machine with Non-Overlapped Windings." Energies 12, no. 8 (2019): 1576. http://dx.doi.org/10.3390/en12081576.

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This paper aims to propose and compare three new structures of single-phase field excited flux switching machine for pedestal fan application. Conventional six-slot/three-pole salient rotor design has better performance in terms of torque, whilst also having a higher back-EMF and unbalanced electromagnetic forces. Due to the alignment position of the rotor pole with stator teeth, the salient rotor design could not generate torque (called dead zone torque). A new structure having sub-part rotor design has the capability to eliminate dead zone torque. Both the conventional eight-slot/four-pole sub-part rotor design and six-slot/three-pole salient rotor design have an overlapped winding arrangement between armature coil and field excitation coil that depicts high copper losses as well as results in increased size of motor. Additionally, a field excited flux switching machine with a salient structure of the rotor has high flux strength in the stator-core that has considerable impact on high iron losses. Therefore, a novel topology in terms of modular rotor of single-phase field excited flux switching machine with eight-slot/six-pole configuration is proposed, which enable non-overlap arrangement between armature coil and FEC winding that facilitates reduction in the copper losses. The proposed modular rotor design acquires reduced iron losses as well as reduced active rotor mass comparatively to conventional rotor design. It is very persuasive to analyze the range of speed for these rotors to avoid cracks and deformation, the maximum tensile strength (can be measured with principal stress in research) of the rotor analysis is conducted using JMAG. A deterministic optimization technique is implemented to enhance the electromagnetic performance of eight-slot/six-pole modular rotor design. The electromagnetic performance of the conventional sub-part rotor design, doubly salient rotor design, and proposed novel-modular rotor design is analyzed by 3D-finite element analysis (3D-FEA), including flux linkage, flux distribution, flux strength, back-EMF, cogging torque, torque characteristics, iron losses, and efficiency.
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9

Zapoměl, Jaroslav, Jan Kozánek, and Petr Ferfecki. "Investigations of Transient Oscillations of Rotors Supported by Magnetorheological Squeeze Film Dampers Using Bilinear Material to Model the Lubricant." Applied Mechanics and Materials 821 (January 2016): 309–16. http://dx.doi.org/10.4028/www.scientific.net/amm.821.309.

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Unbalance of rotors is one of the principal causes of their lateral vibration. A technological solution frequently used to its suppression consists in placing damping devices to the rotor supports. To achieve their optimum performance their damping effect must be controllable. This is offered by squeeze film dampers utilizing the magnetorheological phenomenon to control the damping force. In mathematical models magnetorheological oils are usually represented by Bingham or Herschel-Bulkley theoretical materials. Here the magnetorheological oil is modeled by bilinear material with the yielding shear stress depending on magnetic induction. Its flow curve is continuous which contributes to reducing nonlinear character of the motion equations. The new mathematical model was applied to investigate several operating regimes of rotating machines.
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10

Beaumier, P., M. Costes, and D. Petot. "Couplage dynamique - aérodynamique sur le rotor principal d'hélicoptère." La Houille Blanche, no. 3-4 (June 2000): 38–46. http://dx.doi.org/10.1051/lhb/2000026.

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