Abstract
Experiments have been undertaken at selected electrical loads on a self-contained turbo-alternator set comprising a 350-kW 60-c/s alternator driven by means of double helical parallel shaft gearing by a high-speed (15 000 rev/min) steam turbine.
The turbo-alternator was erected on flexible mountings with all steam, water, and other service connections arranged in such a manner that they placed no constraint on the machine.
In addition to the turbine and alternator rotors several auxiliary drives each contribute to the total noise output. These include the d.c. exciter, pilot exciter, and metadyne unit which are driven directly, or by belts, from the alternator shaft and the oil pumps, governor, etc., which are driven from the turbine shaft by way of spur and bevel gears.
The paper describes the manner in which the separate effects of each of the major sources of structural vibration and airborne noise were isolated and measured. In-place balancing techniques were employed to aid an investigation of the variation of vibration level with rotor out-of-balance. In the process experimental information was obtained about the damping effects of journal bearing oil films, vibration amplitudes of the bearing housing being as much as 25 dB below the equivalent shaft amplitudes.
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