Dynamic Response of a Rotor-Integral Squeeze Film Damper to Couple Imbalances

Abstract

Squeeze film dampers (SFDs) are used in high speed rotating machinery to reduce rotor vibration amplitudes and to isolate transmitted loads through the bearing support structures. SFDs are also effective means to ameliorate destructive subsynchronous vibrations excited by hydrodynamic bearings, seals, impellers and other unknown sources. Modern jet engines demand lighter and flexible structures with compact components to obtain the largest power to weight ratios. This current trend makes evident rotordynamic phenomena that must be adequately addressed by dissipation elements such as SFDs. Integral squeeze film dampers (ISFDs) incorporating built in elastic supports are of reduced weight and length, offer accuracy of positioning, and a split segment construction allowing easier assembly, inspection and retrofit. Yet ISFDs require of extensive experimentation to verify their dynamic forced performance and to prove their reliability for applications on high performance turbomachinery. Measurements of the synchronous response of a test rotor supported on ISFDs and due to couple-imbalances are hereby presented. Masses inserted at two axial planes in the rotor and out of phase by 180° excite the second (conical) mode of vibration of the test rotor. Peak rotor responses at the second critical speeds, vertical and horizontal, allow the determination of amplification factors from which system damping coefficients for the rotor conical motions are extracted. The measurements verify the damping capacity of ISFDs to reduce (conical mode) rotor vibrations.