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Tester for turbine buckets
302
CURRENT TOPICS
In addition to the 216,000-hp. fourmotor drive, the rotating machine will have five compressors, now under construction at the Westinghouse plant in Sunnyvale, Calif. Work on these transonic and supersonic compressors is not expected to be completed for at least another year. T h e transonic compressor will be a single unit, but the supersonic compressor will be made up of four compressors coupled as one. Blades for the compressors measure 2 ft. across the face, are 6 ft. long, and will be mounted on'a spindle 18 ft. in diameter. Weighing almost twothirds of a ton each, the blades will be solid forgings. Although the machine will have the highest stored energy of any rotating mass ever built, it can be brought to a halt in about three minutes by using its wound-rotor motors as brakes, the energy being dissipated in liquid rheostats. During operation, the wind tunnels will require 100,000 gallons of cooling water per minute to reduce the air discharge temperature to about 600 F. However, air in the test chamber will be a b o u t 100 F. below zero. T h e transonic wind tunnel is scheduled for completion early in 1955. T h e supersonic tunnel will be completed in 1957. Tester for Turbine Buckets.--A wailing, complaining inferno of a machine that puffs and blinks and blasts but doesn't move has been developed by scientists of the General Electric Research L a b o r a t o r y to imitate a whirling turbine. Designed to aid in predicting how modern gas turbine buckets will hold up after years of service, the raucous device simulates conditions present in the modern G-E turbine. Such buckets, shaped somewhat like small pro-
[J. F. I.
peller blades, are mounted on turbine rotors to take the impact of hot gases blown against them to turn the rotor. With an eerie howl and a beady, blinking light, the machine blows a scalding hurricane of gas through a slotted wheel against the bucket. Timed electronically to reach a criticM resonance, the sound produced soon sets up a destructive vibration in the tapering bucket. A winking blue stroboscopic light then "stops" this motion to reveal to scientists how much the bucket oscillates. Further details about strains placed on the metal are relayed to a b a t t e r y of recording machines mounted on a nearby instrument panel. Information leading to valuable predictions about metal performance of the buckets under stress can be determined "in a m a t t e r of minutes" by the machine, according to R. V. Klint, young G-E scientist who developed the bucket vibrator. Klint explained that in his machine, resonance set up in the buckets soon causes sufficient vibration to produce fatigue failures in them. This testing, he said, can be done rapidly and at low cost. Another i m p o r t a n t use of the machine, he reported, is in studying conditions that help buckets withstand vibratory forces. One such effect, called damping, is the restraint inherent in metals and bucket designs that prevents excessive vibrations during actual turbine operation. Rupture of the buckets could otherwise resull from these vibrations, Klint pointed out. " B y using the laboratory machine, we are able to measure the magnitudes of these sources of damping and can test and develop various ideas which should p u t damping at the maximum for a given turbine design," the young scientist added.
CURRENT TOPICS
In addition to the 216,000-hp. fourmotor drive, the rotating machine will have five compressors, now under construction at the Westinghouse plant in Sunnyvale, Calif. Work on these transonic and supersonic compressors is not expected to be completed for at least another year. T h e transonic compressor will be a single unit, but the supersonic compressor will be made up of four compressors coupled as one. Blades for the compressors measure 2 ft. across the face, are 6 ft. long, and will be mounted on'a spindle 18 ft. in diameter. Weighing almost twothirds of a ton each, the blades will be solid forgings. Although the machine will have the highest stored energy of any rotating mass ever built, it can be brought to a halt in about three minutes by using its wound-rotor motors as brakes, the energy being dissipated in liquid rheostats. During operation, the wind tunnels will require 100,000 gallons of cooling water per minute to reduce the air discharge temperature to about 600 F. However, air in the test chamber will be a b o u t 100 F. below zero. T h e transonic wind tunnel is scheduled for completion early in 1955. T h e supersonic tunnel will be completed in 1957. Tester for Turbine Buckets.--A wailing, complaining inferno of a machine that puffs and blinks and blasts but doesn't move has been developed by scientists of the General Electric Research L a b o r a t o r y to imitate a whirling turbine. Designed to aid in predicting how modern gas turbine buckets will hold up after years of service, the raucous device simulates conditions present in the modern G-E turbine. Such buckets, shaped somewhat like small pro-
[J. F. I.
peller blades, are mounted on turbine rotors to take the impact of hot gases blown against them to turn the rotor. With an eerie howl and a beady, blinking light, the machine blows a scalding hurricane of gas through a slotted wheel against the bucket. Timed electronically to reach a criticM resonance, the sound produced soon sets up a destructive vibration in the tapering bucket. A winking blue stroboscopic light then "stops" this motion to reveal to scientists how much the bucket oscillates. Further details about strains placed on the metal are relayed to a b a t t e r y of recording machines mounted on a nearby instrument panel. Information leading to valuable predictions about metal performance of the buckets under stress can be determined "in a m a t t e r of minutes" by the machine, according to R. V. Klint, young G-E scientist who developed the bucket vibrator. Klint explained that in his machine, resonance set up in the buckets soon causes sufficient vibration to produce fatigue failures in them. This testing, he said, can be done rapidly and at low cost. Another i m p o r t a n t use of the machine, he reported, is in studying conditions that help buckets withstand vibratory forces. One such effect, called damping, is the restraint inherent in metals and bucket designs that prevents excessive vibrations during actual turbine operation. Rupture of the buckets could otherwise resull from these vibrations, Klint pointed out. " B y using the laboratory machine, we are able to measure the magnitudes of these sources of damping and can test and develop various ideas which should p u t damping at the maximum for a given turbine design," the young scientist added.