The relative influence of the different zones with fluid - structure interaction on the dynamic behaviour of hydraulic machines

In hydraulic machinery, the interactive behaviour of annular seals and impellers plays an important role in the dynamic behaviour, in addition to the influence of the shaft and of the bearings. Taking a high speed, high energy boiler feed pump as an example, the relative influence of the different annular seals (impeller suction side, impeller pressure side, balance piston) and of the impeller interaction is shown and compared with that of the shaft stiffness and of the oil lubricated sleeve type journal bearings. The strong influence of the fluid interactive elements on dynamic rotor behaviour, unbalance response as well as rotor stability, is demonstrated. The impact a swirl brake at the balance piston entrance has on rotor stability is also shown.