Rotordynamic Evaluation of a Large High-Speed Rotor Equipped With Flexure Pivot Journal Bearings and Integral Squeeze Film Damper

Abstract

The current oil and gas market trends lead the compressor OEMs to increase the rotational speed and maximize the efficiency given a target power output. Especially when applied to large process gas centrifugal compressors, characterized by high-flexibility ratio, the achievement of these targets pushes the rotordynamic design towards its limit in terms of API requirements. Tiling pad journal bearings (TPJBs) are commonly adopted in high-speed applications for their inherent stability characteristics that permit to ensure the rotordynamic stability and eliminate self-induced sub-synchronous vibrations. The experimental activities subject of this paper aim to assess, for the first time, the rotordynamic behaviour of a large dummy rotor (6 meter long and total weight of 8 tons) equipped with Flexure Pivot tilting-pad journal bearing and Integral squeeze film damper (ISFD). This system level testing program has been performed in the Authors’ high-speed balancing bunker properly equipped with special instrumentation such as: flow meters and pad temperature probes to monitor journal bearing behaviour, displacement probes to measure rotor vibrations relative to the bearings. The main objective of the experimental activity is the full assessment of the rotordynamic response and the selection of the best configuration to target the design requirements (e.g. FPJB and “Active ISFD” vs. FPJB and “Inactive ISFD”).