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  • 1985-1989  (7)
  • 1980-1984  (7)
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  • 1
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    Two-dimensional unsteady analysis of fluid forces on a whirling centrifugal impeller in a volute (1984)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Destabilizing fluid forces on a whirling centrifugal impeller rotating in a volute were observed. A quasisteady analysis neglecting shed vorticity or an unsteady analysis without a volute does not predict the existence of such destabilizing fluid forces on a whirling impeller. The effects of a volute and the shed vorticity are considered. We treat cases when an impeller with an infinite number of vanes rotates with a constant velocity omega and its center whirls with a constant eccentric radius epsilon and a constant whirling velocity psi. It is assumed that: (1) the number of the vanes is so large that the impeller can be treated as an actuator impeller in which the flow is perfectly guided; (2) flow is inviscid, incompressible and two dimensional; (3) the eccentricity epsilon is so small that unsteady components can be linearized; (4) vorticity is transported on a prescribed mean flow, the operating point is near design flow rate; and (5) the volute can be represented by a curved plate.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA. Lewis Research Center Rotordynamic Instability Problems in High-Performance Turbomachinery; p 161-172
    Format: application/pdf
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  • 2
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    Hydrodynamic impeller stiffness, damping, and inertia in the rotordynamics of centrifugal flow pumps (1984)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The lateral hydrodynamic forces experienced by a centrifugal pump impeller performing circular whirl motions within several volute geometries were measured. The lateral forces were decomposed into: (1) time averaged lateral forces and (2) hydrodynamic force matrices representing the variation of the lateral forces with position of the impeller center. It is found that these force matrices essentially consist of equal diagonal terms and skew symmetric off diagonal terms. One consequence of this is that during its whirl motion the impeller experiences forces acting normal and tangential to the locus of whirl. Data on these normal and tangential forces are presented; it is shown that there exists a region of positive reduced whirl frequencies, within which the hydrodynamic forces can be destablizing with respect to whirl.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA. Lewis Research Center Rotordynamic Instability Problems in High-Performance Turbomachinery; p 137-160
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  • 3
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    On the effect of cavitation on the radial forces and hydrodynamic stiffness of a centrifugal pump (1987)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The asymmetric flow within a volute exerts a radial force on a centrifugal impeller. Experimental measurements of the radial forces on the impeller in the presence of cavitation are presented.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA. Lewis Research Center Rotordynamic Instability Problems in High-Performance Turbomachinery, 1986; p 493-501
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  • 4
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    Rotor-stator interaction in a diffuser pump (1988)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Steady and unsteady pressure measurements were obtained on the diffuser vanes and the shroud wall of vaned and vaneless diffuser pumps in order to investigate the rotor-stator interaction. It is shown that the magnitude of the fluctuating lift is greater than the steady lift, and that the pressure fluctuations are larger on the suction side than on the pressure side. Pressure fluctuations near the shroud were much smaller than those near the hub across the span of the vane. Pressure fluctuations on the shroud wall itself were found to be larger for the vaned diffuser than for the vaneless diffuser.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: ASME PAPER 88-GT-55
    Format: text
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  • 5
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    A test program to measure fluid mechanical whirl-excitation forces in centrifugal pumps (1980)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The details of a test program for the measurement of the unsteady forces on centrifugal impellers are discussed. Various hydrodynamic flows are identified as possible contributors to these destabilizing forces.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA. Lewis Res. Center Rotordyn. Instability Probl. in High-Performance Turbomachinery; p 229-247
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  • 6
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    Dynamics of cavitating cascades and inducer pumps (1981)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Report chronicles advances in understanding and predicting unsteady dynamic characteristics of cavitating cascades and inducer pumps. It includes bibliography of 19 papers authored between 1972 and 1980.
    Keywords: MECHANICS
    Type: MFS-25399 , NASA Tech Briefs (ISSN 0145-319X); 5; 3; P. 359
    Format: text
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  • 7
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    Rotordynamic forces on centrifugal pump impellers (1987)
    In:  Other Sources
    Details
    Publication Date: 2019-07-27
    Description: The asymmetric flow around an impeller in a volute exerts a force upon the impeller. To study the rotordynamic force on an impeller which is vibrating around its machine axis of rotation, the impeller, mounted on a dynamometer, is made to whirl in a circular orbit within the volute. The measured force is expressed as the sum of a steady radial force and an unsteady force due to the eccentric motion of the impeller. These forces were measured in separate tests on a centrifugal pump with radically increased shroud clearance, a two-dimensional impeller, and an impeller with an inducer, the impeller of the HPOTP (High Pressure Oxygen Turbopump) of the SSME (Space Shuttle Main Engine). In each case, a destabilizing force was observed over a region of positive whirl.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Conference on Fluid Machinery; Sept. 1987; Budapest; Hungary
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  • 8
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    Unsteady diffuser vane pressure and impeller wake measurements in a centrifugal pump (1987)
    In:  Other Sources
    Details
    Publication Date: 2019-07-27
    Description: Unsteady surface pressure measurements on a vaned diffuser of a centrifugal pump, and wake measurements of the flow exiting a centrifugal impeller into a vaneless diffuser are presented. Frequency spectra and ensemble averages are given for the unsteady measurements. Two different impellers were used, the pump impeller of the HPOTP (High Pressure Oxygen Turbopump) of the SSME (Space Shuttle Main Engine) and a two-dimensional impeller. The magnitude of the unsteady total pressure measured in the stationary frame at the impeller exit was found to be of the same order of magnitude as the total pressure rise across the pump. The magnitude of the unsteady diffuser vane pressures was observed to be significantly different on suction and pressure side of the vane, attaining its largest value on the suction side the leading edge while decreasing along the vane.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Conference on Fluid Machinery; Sept. 1987; Budapest; Hungary
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  • 9
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    Dynamics of cavitating cascades (1980)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The unsteady dynamics of cavitating cascades and inducer pumps were studied with a view to understanding (and possibly predicting) the dynamic characteristics of these devices. The chronology of the research is summarized as well as the final conculsions for each task. The construction of a dynamic pump test facility and its use in making experimental measurements of the transfer function is described as well as tests conducted using a scale model of the low pressure liquid oxygen turbopump inducer in the shuttle main engine. Auto-oscillation and unsteady inlet flow characteristics are discussed in addition to blade cavity influence and bubbly cavitation.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-CR-161673
    Format: application/pdf
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  • 10
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    Experimental measurements of hydrodynamic stiffness matrices for a centrifugal pump impeller (1982)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The objective of the Rotor Force Test Facility at the California Institute of Technology is to artificially orbit the center of rotation of an impeller enclosed within a volute over a range of frequencies from zero to synchronous and to measure the resulting forces on the impeller. Preliminary data from the first stage experiments in which the shaft is orbited at low frequency is reported. Steady volute forces along with stiffness matrices due to the change in position of the rotor center are measured. Static pressure taps around the volute are used to obtain volute pressure distributions for various fixed positions of the impeller center and for various flow rates. Static pressure forces are calculated from these pressure distributions allowing a more complete analysis of the components of the impeller forces. Comparison is made with various existing theoretical and experimental results.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA. Lewis Research Center Rotordyn. Instability Probl. in High-Performance Turbomachinery; p 382-398
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