THE SYNCHRONOUS INSTABILITY OF A COMPRESSOR ROTOR DUE TO BEARING JOURNAL DIFFERENTIAL HEATING

The paper describes a synchronous vibration instability problem encoun tered on a centrifugal compressor with oil-lubricated bearings. The pr oblem was solved by modification of the compressor rotor; however, the root cause was not completely understood at that time. A possible exp lanation was based on a theory that suggested differential heating of the bearing journals. II rt as decided to verify this theory by experi ments. Therefore a rest rotor,vas designed with identical rotor dynami c characteristics to those of the compressor rotor. To fill a gap in t he published research on bearing thermohydrodynamics, an experimental technique was devised to measure the surface temperature variations ar ound one of the journals of this rotor. The dependence of significant temperature differentials across the journal upon its orbit was confir med.