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  • MECHANICAL ENGINEERING  (5)
  • EARTH RESOURCES AND REMOTE SENSING  (3)
  • 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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    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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  • 5
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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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  • 6
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    Power spectra of geoid undulations (1975)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Data from spacecraft altimeters are expected to contribute to an improved determination of the marine geoid. To better define altimeter system design requirements for geoid recovery, amplitudes of geoid undulations at short wavelengths were examined. Models of detailed geoids in selected areas around the earth, developed from a combination of satellite derived spherical harmonics and 1 deg-by-1 deg area mean free-air gravity anomalies, were subjected to a spectral analysis. The resulting undulation power spectra were compared to existing estimates for the magnitude of geoid undulations at short wavelengths. The undulation spectra were found to be consistent with Kaula's rule of thumb, following an inverse third power relationship with spatial frequency for wavelengths at least as small as 300 km. The requirements imposed by this relationship on altimeter accuracy, data rate, and horizontal resolution to meet the goal of a detailed geoid description are discussed.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: NASA-TM-X-71028 , X-921-75-300
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  • 7
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    Improved definition of crustal magnetic anomalies for MAGSAT data (1982)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The routine correction of MAGSAT vector magnetometer data for external field effects such as the ring current and the daily variation by filtering long wavelength harmonics from the data is described. Separation of fields due to low altitude sources from those caused by high altitude sources is affected by means of dual harmonic expansions in the solution of Dirichlet's problem. This regression/harmonic filter procedure is applied on an orbit by orbit basis, and initial tests on MAGSAT data from orbit 1176 show reduction in external field residuals by 24.33 nT RMS in the horizontal component, and 10.95 nT RMS in the radial component.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: E82-10314 , NASA-CR-168889 , NAS 1.26:168889
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  • 8
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    Mean sea level determination from satellite altimetry (1977)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The primary experiment on the Geodynamics Experimental Ocean Satellite-3 (GEOS-3) is the radar altimeter. This experiment's major objective is to demonstrate the utility of measuring the geometry of the ocean surface, i.e. the geoid. Results obtained from this experiment so far indicate that the planned objectives of measuring the topography of the ocean surface with an absolute accuracy of + or - 5 meters can be met and perhaps exceeded. The GEOS-3 satellite altimeter measurements have an instrument precision in the range of + or - 25 cm to + or - 50 cm when the altimeter is operating in the short pulse mode.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: NASA-TM-X-71298 , X-921-77-41
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