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Critical speed

About: Critical speed is a research topic. Over the lifetime, 2764 publications have been published within this topic receiving 31365 citations.


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Patent
10 Mar 1989
TL;DR: In this paper, the rotational speed of a rotating member was determined by determining the speed from signals having a frequency directly proportional to the rotation speed, even if no speed signals are detected over a sampling interval.
Abstract: A system and method determines the rotational speed of a rotating member by determining speed from signals having a frequency directly proportional to the rotational speed. The system provides for the estimation of rotational speed even if no speed signals are detected over a sampling interval.

17 citations

Journal ArticleDOI
01 May 1987
TL;DR: The flexural vibrations of a rotating shaft, running through one or more critical speeds, can be reduced to an acceptably low level by applying suitable control forces at an intermediate span as mentioned in this paper.
Abstract: The flexural vibrations of a rotating shaft, running through one or more critical speeds, can be reduced to an acceptably low level by applying suitable control forces at an intermediate span posit...

17 citations

Proceedings ArticleDOI
01 Jan 2004
TL;DR: In this article, a small rotor supported on flexure pivot-hydrostatic pad gas bearings (FPTPBs) demonstrated stable rotordynamic responses up to 100,000 rpm (limit of the drive motor).
Abstract: Micro-turbomachinery demands gas bearings to ensure compactness, lightweight and extreme temperature operation. Gas bearings with large stiffness and damping, and preferably of low cost, will enable successful commercial applications. Presently, tests conducted on a small rotor supported on flexure pivot–hydrostatic pad gas bearings (FPTPBs) demonstrate stable rotordynamic responses up to 100,000 rpm (limit of the drive motor). Test rotor responses show the feed pressure raises the system critical speed (increase in bearing direct stiffness) while the viscous damping ratio decreases. Predictions correlate favorably with experimentally identified (synchronous) direct stiffness bearing force coefficients. Identified experimental gas bearing synchronous damping coefficients are 50% or less of the predicted magnitudes, though remaining relatively constant as the rotor speed increases. Tests without feed pressure show the rotor becomes unstable at ∼ 81 krpm with a whirl frequency ratio of 20%. FPTPBs are mechanically complex and more expensive than cylindrical plain bearings. However, their enhanced stability characteristics and predictable rotordynamic performance makes them desirable for the envisioned oil-free applications in high speed micro turbomachinery.Copyright © 2004 by ASME

17 citations

Journal ArticleDOI
TL;DR: In this work, the modeling and basic control design process of a rotary flexible spindle hovered by Active Magnetic Bearings (AMB) whose good capabilities for machine-tool industry extensively treated in the literature is presented.
Abstract: In this work the modeling and basic control design process of a rotary flexible spindle hovered by Active Magnetic Bearings (AMB) whose good capabilities for machine-tool industry extensively treated in the literature is presented. The modeling takes into account the three main behavioral characteristics of such magnetically-levitated rotor: the rigid dynamics, the flexible dynamics and the rotating unbalanced motion. Besides, the gyroscopic coupling is also studied proving that in this case, its effects are not significant and can be neglected. Using this model, a stabilizing controller based on symmetry properties is successfully designed for the system and a complete experimental analysis of its performance is carried out. Also, the predictions of the model are compared with the actual measured experimental results on a laboratory set-up based on the MBC500 Rotor Dynamics. Afterwards, a brief study about some nonlinear behavior observed in the system and its effect over the system stability at the critical speed is included.

17 citations

01 Jan 1998
TL;DR: In this paper, the non-linear dynamic behavior of a flexible shaft is analyzed with an unsteady time integration procedure and the coupling between the axial thrust bearing behavior and the bending vibrations of the shaft is especially studied.
Abstract: In this work, the non-linear dynamic behavior of a flexible shaft is presented. The shaft is mounted in two bearings and axial load is supported by a hydrodynamic thrust bearing, at one end. The coupling between the axial thrust bearing behavior and the bending vibrations of the shaft is especially studied. The shaft is modeled by typical beam finite element including effects such as gyroscopic. A modal reduction allows reducing the number of degrees of freedom. The dynamic behavior of the bearings is considered as non-linear. The dynamic behavior is analysed with an unsteady time integration procedure. The thrust bearing provides an additional stiffness on the flexible shaft. A defect on the thrust-bearing rotor excites a critical speed.

17 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
20241
202343
2022120
202182
202092
2019102