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  • MECHANICAL ENGINEERING  (5)
  • INSTRUMENTATION AND PHOTOGRAPHY  (1)
  • 1
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    A novel form of damper for turbo-machinery (1987)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: 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.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA. Lewis Research Center Rotordynamic Instability Problems in High-Performance Turbomachinery, 1986; p 325-347
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  • 2
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    Experimental investigation of lateral forces induced by flow through model labyrinth glands (1984)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: 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.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA. Lewis Research Center Rotordynamic Instability Problems in High-Performance Turbomachinery; p 187-210
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  • 3
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    The effect of inlet swirl on the dynamics of long annular seals in centrifugal pumps (1994)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: 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.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA. Lewis Research Center, Rotordynamic Instability Problems in High-Performance Turbomachinery, 1993; p 149-165
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  • 4
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    Seeding materials: Health and safety considerations (1985)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The choice of a proper seeding material for laser velocimeters must include health and safety considerations. Failure to do so can lead to catastrophic results. All materials are toxic, and laser velocimeter seeding materials are no exception. Toxicity may be considered an inherent property of a given material. The manifestation of that property or the physiological response to the material is dependent on dose and exposure conditions. An approximate physiological classification of toxicity is given in tablular form. Toxicity in some situations is not necessarily the most restrictive factor in selection of materials. It is also very important to consider how the material is used so that actual exposure to the material in a damaging form can result. For example, nickel and cadmium are both extremely toxic as systemic poisons and in the case of nickel as a carcinogen. Seeding materials are dispersed in air under conditions that favor personnel exposure. Dispersal equipment is frequently if not normally manned, and personnel are often required to make frequent adjustments to assure proper operations.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Wind Tunnel Seeding Systems for Laser Velocimeters; p 211-219
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  • 5
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    Limit cycles of a flexible shaft with hydrodynamic journal bearings in unstable regimes (1980)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: 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.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA. Lewis Res. Center Rotordyn. Instability Probl. in High-Performance Turbomachinery; p 331-343
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  • 6
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    Circumferential pressure distributions in a model labyrinth seal (1982)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: 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.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA. Lewis Research Center Rotordyn. Instability Probl. in High-Performance; p 223-241
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