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Licht, L.

Publications and source records attributed to Licht, L..

17 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1980

Dynamic characteristics of a high-speed rotor with radial and axial foil-bearing supports

An asymmetric rotor (19N; 4.3 lb), supported radially and axially by compliant bearings is subjected to severe excitation by rotating unbalance in the 'pitching' mode at speeds to 50,000 rpm. The resilient, air-lubricated bearings provide very effective damping, so that regions of resonance and instability can be traversed with amplitudes and limit-trajectories within acceptable bounds. A novel journal bearing is introduced, in which a resilient support is furnished by the outer turn of the coiled foil-element bent to form an open polygon. The experimental apparatus and procedure are described, and the response of the rotor and flexible support system are documented by oscilloscope records of motion.

Licht, L.↗
NASA NTRS1980

Design and performance of compliant thrust bearing with spiral-groove membranes on resilient supports

Novel thrust bearings with spiral-groove flexible membranes mounted on resilient supports were designed and their performance demonstrated. Advantages of surface compliance were combined with the superior load-capacity of the spiral-groove geometry. Loads of 127-150N were supported on an area 42 sq cm, at speeds of 43,000-45,000 rpm and mean clearances of 15-20 microns. Support-worthiness was proved when tested in conjunction with foil journal-bearings and a 19N rotor, excited in a pitching mode by a total unbalance of 43 micron-N.

Licht, L.↗
NASA NTRS1978

Foil bearings for axial and radial support of high speed rotors: Design, development, and determination of operating characteristics

Flexible surface thrust and journal foil bearings were fabricated, and their performance was demonstrated, both individually and jointly as a unified rotor support system. Experimental results are documented with graphs and oscilloscopic data of trajectories, waveforms, and scans of amplitude response. At speeds of 40,000 to 45,000 rpm and a mean clearance of the order of 15 to 20 micrometers (600 to 800 micrometers, the resilient, air lubricated, spiral groove thrust bearings support a load of 127 N (29 lb; 13 kgf), equivalent to 3.0 N/sq cm (4.5 lb/sq in 0.31 kgf sq cm). Journal bearings with polygonal sections provided stable and highly damped supports at speeds up to 50,000 rpm.

Licht, L.↗
NASA NTRS1973

Design, fabrication, and performance of foil journal bearing for the brayton rotating unit

Foil bearings were designed and manufactured to replace pivoted-shoe journal bearings in an existing Brayton Cycle turbo-alternator-compressor. The design of this unconventional rotor support was accomplished within the constraints and space limitations imposed by the present machine, and the substitution of foil bearings was effected without changes or modification other machine components. A housing and a test rig were constructed to incorporate the new foil-bearing support into a unified assemble with an air-driven rotor and the gimbal-mounted thrust bearing, seals, and shrouds of an actual Brayton Rotating Unit. The foil bearing required no external pressure source, and stable self-acting rotation was achieved at all speeds up to 43,200 rpm. Excellent wipe-wear characteristics of the foil bearing permitted well over 1000 start-stop cycles with no deterioriation of performance in the entire speed range.

Licht, L.↗
NASA NTRS1973

Gas-lubricated foil bearings for high speed turboalternator - Construction and performance

Foil bearings were designed and fabricated to replace pivoted-shoe journal bearings in a Brayton cycle turboalternator, within space limitations and constraints imposed by the existing machine. The foil bearings were integrated into a unified assembly with the rotor, housing, seals, and gimbal-mounted thrust bearing, without changes and modifications of machine components other than the journal bearings. The gas-lubricated foil bearings, which require no external pressure-source, furnished a stable support for a 21.9 pound rotor in the vertical attitude at speeds to 43,200 rpm. Excellent wipe-wear characteristics permitted well over 1000 start-stop cycles, without deterioration of performance in the entire speed range. The paper reviews salient aspects of design, fabrication, and performance. An account is given of rotor dynamics during starting, stopping, and traversing the region of resonances. The state of journal and foil surfaces is examined following intensive start-stop cycling and high-speed runs over extended periods of time.

Licht, L.↗
NASA NTRS1970

The dynamic characteristics of a turbo-rotor simulator supported on gas-lubricated foil bearings. Part 1: Response to rotating imbalance and unidirectional excitation

A sixteen-inch rotor, weighing approximately twenty-one pounds, was supported by air-lubricated foil bearings. In physical size and in mass distribution, the rotor closely matched that of an experimental Brayton cycle turboalternator unit. The rotor was stable in both vertical horizontal attitudes at speeds up to 50,000 rpm. A detailed description of the experimental apparatus and of the foil bearing design are given. The paper contains data on response of the rotor to rotating imbalance, symmetric and asymmetric, and to excitation by means of a vibrator (shake table). It is concluded that the gas-lubricated foil bearing suspension is free from fractional frequency whirl and suffers no loss of load capacity when excited at frequency equal to half the rotational speed. In contrast to rigid gas bearings, the foil bearing imposes no stringent requirements with respect to dimensional tolerances, cleanliness, or limitations of journal motion within the narrow confines of bearing clearance.

Licht, L.↗
NASA NTRS1970

The dynamic characteristics of a turbo-rotor simulator supported on gas-lubricated foil bearings. Part 2: Operation with heating and thermal gradients

A high speed rotor, supported by gas-lubricated foil bearings, is free from self-excited whirl and displays no loss of load capacity when vibrated at frequency equal to the rotational speed. It is demonstrated that in addition to tolerance of geometrical imperfections, misalignment and foreign particles, the foil bearing performs well at elevated temperatures and accommodates appreciable temperature gradients. The foil bearing is endowed with superior wipe-wear characteristics and the flexibility of the foil accounts not only for the stability of the foil bearing, but also for its accommodation of, and compensation for, distortion, contamination, and contact.

Licht, L.↗
NASA NTRS1969

Foil bearings.

Foil bearings design, fabrication, applications to flexible material transport, rotor support, etc

Eshel, A.↗