Radiant energy – Photocells; circuits and apparatus – Optical or pre-photocell system
Patent
1976-06-23
1977-09-20
Smith, Alfred E.
Radiant energy
Photocells; circuits and apparatus
Optical or pre-photocell system
250208, 356167, G01D 536, H01J 3912
Patent
active
040496449
ABSTRACT:
A reference mark for photo detection is placed on the disc or shaft of a blade carrying rotor of a turbomachine. A first light source and photodetector are aimed at the referencce mark and provide an electrical pulse per revolution. A second light source and photodetector are positioned in the casing of the turbomachine adjacent to the rotor of interest. A first signal from the first photodetector turns on a first and second counter, counting pulses from a high frequency source. A signal from the second photodetector turns off the second counter. The next signal from the first photodetector turns off the first counter. The first counter provides a count of pulses per revolution. The second counter provides a count of pulses representative of arc of movement of the blade tip in interest from the time the reference mark passed the first photodetector until the next blade tip passed the second photodetector. The difference in the ratios of the count of pulses from the second counter with respect to the count from the first counter with the turbomachine unloaded and then loaded provides a figure, derived subsequently of rotational speed, that is representative of the circumferential deflection of the blade tip at the detection position due to the loading. The above sequence may be continued for multiple revolutions to provide an average result that is less influenced by blade vibration. By multiplying this figure times 2.pi.R, where R is the radius of the blade tip, the actual deflection of the blade tip in the units of measurement of R is obtained. Multiple photodetectors at different positions aimed at the blade tip will provide a profile of tip deflection. The loading referred to may be aerodynamic or centrifugal or both.
REFERENCES:
patent: 3614617 (1971-10-01), Blake, Jr.
patent: 3757167 (1973-09-01), Yoshikawa et al.
patent: 3856410 (1974-12-01), Swift et al.
patent: 3935537 (1976-01-01), Batchlor
Duncan Robert Kern
Moore David K.
Rusz Joseph E.
Smith Alfred E.
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