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Pollack, J. L.

Publications and source records attributed to Pollack, J. L..

9 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1977

Optical detection of blade flutter

The paper examines the capabilities of photoelectric scanning (PES) and stroboscopic imagery (SI) as optical monitoring tools for detection of the onset of flutter in the fan blades of an aircraft gas turbine engine. Both optical techniques give visual data in real time as well as video-tape records. PES is shown to be an ideal flutter monitor, since a single cathode ray tube displays the behavior of all the blades in a stage simultaneously. Operation of the SI system continuously while searching for a flutter condition imposes severe demands on the flash tube and affects its reliability, thus limiting its use as a flutter monitor. A better method of operation is to search for flutter with the PES and limit the use of SI to those times when the PES indicates interesting blade activity.

Nieberding, W. C.↗
NASA NTRS1977

Optical Detection of Blade Flutter

Dynamic strain gages mounted on rotor blades are used as the primary instrumentation for detecting the onset of flutter and defining the vibratory mode and frequency. Optical devices are evaluated for performing the same measurements as well as providing supplementary information on the vibratory characteristics. Two separate methods are studied: stroboscopic imagery of the blade tip and photoelectric scanning of blade tip motion. Both methods give visual data in real time as well as video tape records. The optical systems are described, and representative results are presented. The potential of this instrumentation in flutter research is discussed.

Nieberding, W. C.↗
NASA NTRS1973

High powered arc electrodes

Nonconsumable metal electric arc electrodes are described capable of being operated in a variety of gases at various pressures, current, and powers. The cathode has a circular annulus tip to spread the emission area for improved cooling.

Hall, J. H.↗
NASA NTRS1972

A 400 kilowatt argon arc lamp for solar simulation

A 400 kilowatt argon arc lamp for a solar simulator has been designed, operated, and evaluated. The lamp is designed to produce one solar constant on a test area 4.6 by 9.2 meters when used with a collimator. The divergence angle of the beam is about 1 deg. The lamp is designed to operate completely within a vacuum environment. Over 80 kilowatt of directed radiation was monitored and measured for a 25-hour period during a recent test. In another test, an arc was operated at 400 kilowatt for 110 hours without removal or refurbishing of the electrodes. These tests have proven the cleanliness and integrity of the radiation source.

Decker, A. J.↗
NASA NTRS1971

Durable cathodes for high-power inert-gas arcs

Cathode design minimizes evaporation of electrode material which may deposit on associated optical surfaces. It also results in stable operation and precise positioning of arc relative to optical collector. Innovation applies to high power light sources and to arcs used in industrial furnaces.

Decker, A. J.↗
NASA NTRS1964

Status of solar simulation at Lewis

Evaluation of solar simulators using enclosed sources, in-house measurement facility for testing proposed devices to produce solar simulation, and related research programs

SOLAR SIMULATOR↗