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Description:
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A new closed -loop frequency -domain model is developed to incorporate the water hammer effect with pump rotordynamics , in order to investigate the sub -synchronous instability problem observed in a field pump . Seal flow -rate perturbations due to eccentricity are calculated from Soulas and San Andres's seal code . A complete transfer function matrix between rotor motion and reaction force due to pressure perturbation is developed in detail . Stability analysis with transfer -function'add -in' modules is conducted in XLTRC2 . Seal clearances and the reaction force angle are found to be important in shifting natural frequencies and damping . The sub -synchronous instability observed in field is duplicated successfully with double -clearance seals . |