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  • 11
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    Liquid-Hydrogen-Cooled 450-hp Electric Motor Test Stand Being Developed (2005)
    In:  CASI
    Details
    Publication Date: 2018-06-05
    Description: With growing concerns about global warming, there is a need to develop pollution-free aircraft. One approach is to use hydrogen-fueled airc raft that use fuel cells or turbogenerators to produce electric power to drive the electric motors that turn the aircraft#s propulsive fan s. Hydrogen fuel would be carried as a liquid, stored at its boiling point of 20.5 K (-422.5 ?F). Conventional electric motors, however, are too heavy to use on an aircraft. We need to develop high-power, lig htweight electric motors (high-powerdensity motors).
    Keywords: Aircraft Propulsion and Power
    Type: Research and Technology 2004; NASA/TM-2005-213419
    Format: text
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    NASA TECHNICAL REPORTS
  • 12
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    "Fan-Tip-Drive" High-Power-Density, Permanent Magnet Electric Motor and Test Rig Designed for a Nonpolluting Aircraft Propulsion Program (2004)
    In:  CASI
    Details
    Publication Date: 2018-06-05
    Description: A scaled blade-tip-drive test rig was designed at the NASA Glenn Research Center. The rig is a scaled version of a direct-current brushless motor that would be located in the shroud of a thrust fan. This geometry is very attractive since the allowable speed of the armature is approximately the speed of the blade tips (Mach 1 or 1100 ft/s). The magnetic pressure generated in the motor acts over a large area and, thus, produces a large force or torque. This large force multiplied by the large velocity results in a high-power-density motor.
    Keywords: Aircraft Propulsion and Power
    Type: Research and Technology 2003; NASA/TM-2004-212729
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 13
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    High-Temperature Magnetic Bearings Being Developed for Gas Turbine Engines (1998)
    In:  CASI
    Details
    Publication Date: 2018-06-05
    Description: Magnetic bearings are the subject of a new NASA Lewis Research Center and U.S. Army thrust with significant industry participation, and cooperation with other Government agencies. The NASA/Army emphasis is on high-temperature applications for future gas turbine engines. Magnetic bearings could increase the reliability and reduce the weight of these engines by eliminating the lubrication system. They could also increase the DN (diameter of bearing times the rpm) limit on engine speed and allow active vibration cancellation systems to be used, resulting in a more efficient, "more electric" engine. Finally, the Integrated High Performance Turbine Engine Technology (IHPTET) program, a joint Department of Defense/industry program, identified a need for a high-temperature (1200 F) magnetic bearing that could be demonstrated in their Phase III engine. This magnetic bearing is similar to an electric motor. It has a laminated rotor and stator made of cobalt steel. Wound around the stator's circumference are a series of electrical wire coils which form a series of electric magnets that exert a force on the rotor. A probe senses the position of the rotor, and a feedback controller keeps it centered in the cavity. The engine rotor, bearings, and casing form a flexible structure with many modes. The bearing feedback controller, which could cause some of these modes to become unstable, could be adapted to varying flight conditions to minimize seal clearances and monitor the health of the system.
    Keywords: Aircraft Propulsion and Power
    Type: Research and Technology 1997; NASA/TM-1998-206312
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 14
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    More-Electric Gas Turbine Engines (1997)
    In:  Other Sources
    Details
    Publication Date: 2019-07-18
    Description: A new NASA Lewis Research Center and U.S. Army Research Laboratory (ARL) thrust, the more-electric commercial engine, is creating significant interest in industry. This engine would have an integral starter-generator on the gas generator shaft and would be fully supported by magnetic bearings. The NASA/Army emphasis is on a high-temperature magnetic bearing for future gas turbine engines. Magnetic bearings could increase the reliability and reduce the weight of such engines by eliminating the lubrication system. They could also increase the DN (diameter of the bearing times the rpm) limit on engine speed and allow active vibration cancellation systems to be used, resulting in a more efficient, more-electric engine.
    Keywords: Mechanical Engineering
    Type: Research and Technology 1996; NASA-TM-107350
    Format: text
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    NASA TECHNICAL REPORTS
  • 15
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    In Operation Detection and Correction of Rotor Imbalance in Jet Engines Using Active Vibration Control (1994)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Jet Engines may experience severe vibration due to the sudden imbalance caused by blade failure. This research investigates employment of on board magnetic bearings or piezoelectric actuators to cancel these forces in flight. This operation requires identification of the source of the vibrations via an expert system, determination of the required phase angles and amplitudes for the correction forces, and application of the desired control signals to the magnetic bearings or piezo electric actuators. This paper will show the architecture of the software system, details of the control algorithm used for the sudden imbalance correction project described above, and the laboratory test results.
    Keywords: Aircraft Propulsion and Power
    Type: SAE-TP-941151 , (ISSN 0148-7191)|Aerospace Atlantic Conference and Exposition; Apr 18, 1994 - Apr 22, 1994; Dayton, OH; United States
    Format: text
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    NASA TECHNICAL REPORTS
  • 16
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    Update on High-Temperature Coils for Electromagnets (2005)
    In:  CASI
    Details
    Publication Date: 2019-07-12
    Description: A report revisits the subject matter of "High-Temperature Coils for Electromagnets" (LEW-17164), NASA Tech Briefs, Vol. 26, No. 8, (August 2002) page 38. To recapitulate: Wires have been developed for use in electromagnets that operate at high temperatures. The starting material for a wire of this type can be either a nickel-clad, ceramic-insulated copper wire or a bare silver wire. The wire is covered by electrical-insulation material that is intended to withstand operating temperatures in the range from 800 to 1,300 F (.430 to .700 C): The starting wire is either primarily wrapped with S-glass as an insulating material or else covered with another insulating material wrapped in S-glass prior to the winding process. A ceramic binding agent is applied as a slurry during the winding process to provide further insulating capability. The turns are pre-bent during winding to prevent damage to the insulation. The coil is then heated to convert the binder into ceramic. The instant report mostly reiterates the prior information and presents some additional information on the application of the ceramic binding agent and the incorporation of high-temperature wire into the windings.
    Keywords: Man/System Technology and Life Support
    Type: LEW-17467-1 , NASA Tech Briefs, December 2005; 29-30
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 17
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    Stabilizing Gyroscopic Modes in Magnetic-Bearing-Supported Flywheels by Using Cross-Axis Proportional Gains (2006)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: For magnetic-bearing-supported high-speed rotating machines with significant gyroscopic effects, it is necessary to stabilize forward and backward tilt whirling modes. Instability or low damping of these modes can prevent the attainment of desired shaft speed. We show analytically that both modes can be stabilized by using cross-axis proportional gains and high- and low-pass filters in the magnetic bearing controller. Furthermore, at high shaft speeds, where system phase lags degrade the stability of the forward-whirl mode, a phasor advance of the control signal can partially counteract the phase lag. In some range of high shaft speed, the derivative gain for the tilt modes (essential for stability for slowly rotating shafts) can be removed entirely. We show analytically how the tilt eigenvalues depend on shaft speed and on various controller feedback parameters.
    Keywords: Mechanical Engineering
    Type: NASA/TM-2006-214027 , E-15382 , ARL-TR-3799 , AIAA Paper 2005-5955 , Guidance, Navigation, and Control Conference and Exhibit; Aug 15, 2005 - Aug 18, 2005; San Francisco, CA; United States
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 18
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    A New 1000 F Magnetic Bearing Test Rig (1997)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: NASA and the Army are currently exploring the possibility of using magnetic bearings in gas turbine engines. The use of magnetic bearings in gas turbine engines could increase the reliability by eliminating the lubrication system. The use of magnetic bearings could also increase the speed and the size of the shafts in the engine, thus reducing vibrations and possibly eliminating third bearings. Magnetic bearings can apply forces to the shafts and move them so that blade tips and seals do not rub. This could be part of an active vibration cancellation system. Also, whirling (displacing the shaft center line) may delay rotating stall and increase the stall margin of the engine. Magnetic bearings coupled with an integral starter generator could result in a more efficient 'more electric' engine. The IHPTET program, a joint DOD-industry program, has identified a need for a high temperature, (as high as 1200 F), magnetic bearing that could be demonstrated in a phase m engine. A magnetic bearing is similar to an electric motor. The magnetic bearing has a laminated rotor and stator made out of cobalt steel. The stator has a series of coils of wire wound around it. These coils f u. a series of electromagnets around the circumference. These magnets exert a force on the rotor to keep the rotor in the center of the cavity. The centering force is commanded by a controller based on shaft position, (measured by displacement probes). The magnetic bearing can only pull and is basically unstable before active control is applied The engine shafts, bearings, and case form a flexible structure which contain a large number of modes. A controller is necessary to stabilize these modes. A power amplifier is also necessary to provide the current prescribed by the controller to the magnetic bearings. In case of very high loads, a conventional back up bearing will engage and stop the rotor and stator from rubbing.
    Keywords: Research and Support Facilities (Air)
    Type: Paper-30 , Physics and Process Modeling (PPM) and Other Propulsion R and T; 2; NASA-CP-10193-Vol-2
    Format: text
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    NASA TECHNICAL REPORTS
  • 19
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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
  • 20
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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
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