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  • 1
    Digitale Medien
    Digitale Medien
    Chaos in the unbalance response of journal bearings (1994)
    Springer
    Nonlinear dynamics 5 (1994), S. 421-432 
    Details
    ISSN: 1573-269X
    Schlagwort(e): Chaos ; unbalance ; journal ; bearings
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Abstract The behaviour of non-linear systems often yield unexpected phenomena which are extremely sensitive to initial conditions. The hydrodynamic journal bearing is a common machine element which is strongly nonlinear for large excursions within the clearance space. A simple model of a rigid journal, supported hydrodynamically using a short bearing theory is shown to behave chaotically when the rotating unbalance force exceeds the gravitational load. At these values of the force ratio the time history of the response is very sensitive to initial conditions and a spectral analysis demonstrates a significant broadening from the expected peak at the rotational frequency. A once per revolution sampling of the time history (Poincaré plot) revealed an apparent aperiodic pattern. An estimate of the fractal dimension using the Grasberger-Procaccia algorithm resulted in a lower bound of 2.15, a typical result for low dimensional systems with significant dissipative action. The required levels of unbalance are only an order of magnitude greater than acceptable levels for rotating machinery and thus could be achieved with in-service erosion or minor damage. The subsequent non-synchronous response could result in fatigue and potential shaft failure.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00052452
    Standort Signatur Erwartet Verfügbarkeit
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    Artikel (Nationallizenzen)
    Volltext
  • 2
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    Unbekannt
    A novel form of damper for turbo-machinery (1987)
    In:  CASI
    Details
    Publikationsdatum: 2013-08-31
    Beschreibung: Anti-swirl vanes are used by some manufacturers to delay the full development of half speed circulation in annular clearance spaces. The objective is to reduce the aerodynamic cross-coupling in the forward direction. The novel feature of a jet damper is a number of tangential nozzles discharging against the rotor surface speed. Some preliminary results on a 33.9 Kg rotor demonstrate that significant reductions in amplitude are obtained at the synchronous critical speeds.
    Schlagwort(e): MECHANICAL ENGINEERING
    Materialart: NASA. Lewis Research Center Rotordynamic Instability Problems in High-Performance Turbomachinery, 1986; p 325-347
    Format: application/pdf
    Standort Signatur Erwartet Verfügbarkeit
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    NASA TECHNICAL REPORTS
  • 3
    facet.materialart.
    Unbekannt
    Experimental investigation of lateral forces induced by flow through model labyrinth glands (1984)
    In:  CASI
    Details
    Publikationsdatum: 2016-06-07
    Beschreibung: The lateral forces induced by flow through model labyrinth glands were investigated. Circumferential pressure distributions, lateral forces and stiffness coefficients data obtained are discussed. The force system is represented as a negative spring and a tangential force orthogonal to eccentricity. The magnitude of these forces are dependent on eccentricity, entry swirl, rotor peripheral velocity and seal size. A pressure equalization chamber at midgland tests should in significantly reduced forces and stiffness coefficients.
    Schlagwort(e): MECHANICAL ENGINEERING
    Materialart: NASA. Lewis Research Center Rotordynamic Instability Problems in High-Performance Turbomachinery; p 187-210
    Format: application/pdf
    Standort Signatur Erwartet Verfügbarkeit
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    NASA TECHNICAL REPORTS
  • 4
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    Unbekannt
    The effect of inlet swirl on the dynamics of long annular seals in centrifugal pumps (1994)
    In:  CASI
    Details
    Publikationsdatum: 2013-08-31
    Beschreibung: This paper describes additional results from a continuing research program which aims to identify the dynamics of long annular seals in centrifugal pumps. A seal test rig designed at Heriot-Watt University and commissioned at Weir Pumps Research Laboratory in Alloa permits the identification of mass, stiffness, and damping coefficients using a least-squares technique based on the singular value decomposition method. The analysis is carried out in the time domain using a multi-fiequency forcing function. The experimental method relies on the forced excitation of a flexibly supported stator by two hydraulic shakers. Running through the stator embodying two symmetrical balance drum seals is a rigid rotor supported in rolling element bearings. The only physical connection between shaft and stator is the pair of annular gaps filled with pressurized water discharged axially. The experimental coefficients obtained from the tests are compared with theoretical values.
    Schlagwort(e): MECHANICAL ENGINEERING
    Materialart: NASA. Lewis Research Center, Rotordynamic Instability Problems in High-Performance Turbomachinery, 1993; p 149-165
    Format: application/pdf
    Standort Signatur Erwartet Verfügbarkeit
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    NASA TECHNICAL REPORTS
  • 5
    facet.materialart.
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    Limit cycles of a flexible shaft with hydrodynamic journal bearings in unstable regimes (1980)
    In:  CASI
    Details
    Publikationsdatum: 2016-06-07
    Beschreibung: A symmetric 3 mass rotor supported on hydrodynamic bearings is described. An approximate method of representing finite bearings is used to calculate bearing forces. As the method sums forces from a number of independent circular lobes lemon 3 and 4 lobe bearings are taken into account. The calculations are based on an axial groove bearing. Linear analysis precedes nonlinear simulation of some unstable conditions. The demonstration of small limit cycles suggests that necessarily flexible rotors e.g., helicopter tail rotors, may be practical without either tilt pad bearings or external dampers.
    Schlagwort(e): MECHANICAL ENGINEERING
    Materialart: NASA. Lewis Res. Center Rotordyn. Instability Probl. in High-Performance Turbomachinery; p 331-343
    Format: application/pdf
    Standort Signatur Erwartet Verfügbarkeit
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    NASA TECHNICAL REPORTS
  • 6
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    Circumferential pressure distributions in a model labyrinth seal (1982)
    In:  CASI
    Details
    Publikationsdatum: 2016-06-07
    Beschreibung: A research program to isolate and study leakage flow through labyrinth glands was initiated. Circumferential pressure distributions were measured in the labyrinth glands with geometry appropriate to the high pressure labyrinths in large steam turbines. Knowledge of this pressure distribution is essential as it is this unequal pressure field that results in the destabilizing force. Parameters that are likely to affect the pressure distributions are incorporated into the test rig. Some preliminary pressure profiles are presented.
    Schlagwort(e): MECHANICAL ENGINEERING
    Materialart: NASA. Lewis Research Center Rotordyn. Instability Probl. in High-Performance; p 223-241
    Format: application/pdf
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    NASA TECHNICAL REPORTS
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