Lecture 9: Prediction of Subsynchronous Rotor Vibration Amplitude Caused by Rotating Stall

Lecturepg. 97-102The prediction of rotating stall is one of the most important key technologies for compressors, especially high-pressure compressors. The operating ranges of compressors are restricted by rotating stalls because they my cause severe subsynchronous vibration of the rotor. As a consequence, there are many papers that have reported on the subject, including the influence of vaneless diffuser geometry on rotating stalls,m and prediction of when a rotating stall occurs through experiment and theory. But, so for, there is no way to predict accurately the amplitude of subsynchronous rotor vibration caused by a rotating stall. In this paper, the pressure fluctuation caused by rotating stall and the resulting vibration of the rotor were measured using a test rig. The external force on the impeller during a rotating stall was estimated from the measured pressure fluctuation. The subsynchronous vibration amplitude was then calculated using rotordynamics analysis by adding this external force. Comparing the result of this rotordynamics analysis with the measured subsynchronous vibration, an influence factor of pressure fluctuation to rotor vibration, β, was calculated. The accuracy of this factor β was checked by comparison with the result of a shop test on a compressor. Using this factor, the subsynchronous rotor vibration level caused by a rotating stall can then be predicted at the design stage