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  • MECHANICAL ENGINEERING  (4)
  • MACHINERY  (2)
  • INSTRUMENTATION AND PHOTOGRAPHY  (1)
  • Spacecraft Propulsion and Power  (1)
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Keywords
Years
  • 1
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    Electromechanical simulation and test of rotating systems with magnetic bearing or piezoelectric actuator active vibration control (1994)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: This paper contains a summary of the experience of the authors in the field of electromechanical modeling for rotating machinery - active vibration control. Piezoelectric and magnetic bearing actuator based control are discussed.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA. Langley Research Center, Second International Symposium on Magnetic Suspension Technology, Part 2; p 467-478
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 2
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    Piezoelectric pushers for active vibration control of rotating machinery (1988)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: The active control of rotordynamic vibrations and stability by magnetic bearings and electromagnetic shakers have been discussed extensively in the literature. These devices, though effective, are usually large in volume and add significant weight to the stator. The use of piezoelectric pushers may provide similar degrees of effectiveness in light, compact packages. Tests are currently being conducted with piezoelectric pusher-based active vibration control. Results from tests performed on NASA test rigs as preliminary verification of the related theory are presented.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: NASA, Lewis Research Center, Lewis Structures Technology, 1988. Volume 1: Structural Dynamics; p 29-46
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 3
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    Feed-forward control of gear mesh vibration using piezoelectric actuators (1994)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: This paper presents a novel means for suppressing gear mesh-related vibrations. The key components in this approach are piezoelectric actuators and a high-frequency, analog feed-forward controller. Test results are presented and show up to a 70-percent reduction in gear mesh acceleration and vibration control up to 4500 Hz. The principle of the approach is explained by an analysis of a harmonically excited, general linear vibratory system.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA-TM-106366 , E-8168 , NAS 1.15:106366 , ARL-TR-416
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 4
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    Vibration dampers for cryogenic turbomachinery (1990)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: This paper describes the development of effective and reliable minimum-weight and minimum-envelope vibration dampers for cryogenic turbines. To meet this objective, a high speed test rig was designed and fabricated, which is currently used to test a curved beam type damper. The operation, capacity, structural characteristics, measurement system, and safety features of the cryogenic damper test rig are discussed.
    Keywords: MECHANICAL ENGINEERING
    Type: AIAA PAPER 90-2740
    Format: text
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    NASA TECHNICAL REPORTS
  • 5
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    Dual-Actuator Active Vibration-Control System (1994)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Dual-actuator active vibration-control (DAAVC) system is developmental system of type described in "Active Vibration Dampers for Rotating Machinery" (LEW-15427). System features sensors and actuators positioned and oriented at bearings to measure and counteract vibrations of shaft along either of two axes perpendicular to axis of rotation. Effective in damping vibrations of helicopter-engine test stand, making it safer to operate engine at speeds near and above first resonance of engine/test-stand system. Opens new opportunities for engine designers to draw more power from engine, and concept applicable to other rotating machines.
    Keywords: MACHINERY
    Type: LEW-15765 , NASA Tech Briefs (ISSN 0145-319X); 18; 12; P. 74
    Format: text
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    NASA TECHNICAL REPORTS
  • 6
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    Use of piezoelectric actuators in active vibration control of rotating machinery (1990)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Theoretical and test results for the development of piezoelectric-actuator-based active vibration control (AVC) are presented. The evolution of this technology starts with an ideal model of the actuator and progresses to a more sophisticated model where the pushers force the squirrel cage ball bearing supports of a rotating shaft. The piezoelectric pushers consist of a stack of piezoelectric ceramic disks that are arranged on top of one another and connected in parallel electrically. This model consists of a prescribed displacement that is proportional to the input voltage and a spring that represents the stiffness of the stack of piezoelectric disks. System tests were carried out to stabilize the AVC system, verify its effectiveness in controlling vibration, and confirm the theory presented.
    Keywords: MECHANICAL ENGINEERING
    Type: Electro-optical Materials for Switches, Coatings, Sensor Optics, and Detectors; Apr 16, 1990 - Apr 20, 1990; Orlando, FL; United States
    Format: text
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    NASA TECHNICAL REPORTS
  • 7
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    Piezoelectric Pushers Suppress Vibrations (1990)
    In:  Other Sources
    Details
    Publication Date: 2019-07-12
    Description: Vibration-suppressing control systems including piezoelectric actuators undergoing development. Small, lightweight, and rugged. Requires simpler electronic control subsystems and does not require large electromagnet coils. Continues to provide support and some passive damping even when electronic control subsystems or power supplies fail. Intended primarily to enhance safety and prevent damage in rotating machinery by sensing and counteracting vibrations. Useful in suppressing unpredictable vibrations caused by changes in loads, losses of rotating components and consequent imbalances in rotors, and ingestion of foreign objects into turbines.
    Keywords: MACHINERY
    Type: LEW-14927 , NASA Tech Briefs (ISSN 0145-319X); 14; 8; P. 59
    Format: text
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    NASA TECHNICAL REPORTS
  • 8
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    Bleed Cycle Propellant Pumping in a Gas-Core Nuclear Rocket Engine System (1972)
    In:  CASI
    Details
    Publication Date: 2019-09-18
    Description: The performance of ideal and real staged primary propellant pumps and bleed-powered turbines was calculated for gas-core nuclear rocket engines over a range of operating pressures from 500 to 5000 atm. This study showed that for a required engine operating pressure of 1000 atm the pump work was about 0.8 hp/(lb/sec), the specific impulse penalty resulting from the turbine propellant bleed flow as about 10 percent; and the heat required to preheat the propellant was about 7.8 MW/(lb/sec). For a specific impulse above 2400 sec, there is an excess of energy available in the moderator due to the gamma and neutron heating that occurs there. Possible alternative pumping cycles are the Rankine or Brayton cycles.
    Keywords: Spacecraft Propulsion and Power
    Type: NASA-TM-X-2517 , E-6639
    Format: application/pdf
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    NASA TECHNICAL REPORTS
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