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 compressor, 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 application for their inherent stability characteristics which permit&nbsp;to ensure the rotordynamic stability and eliminate self-induced sub-synchronous vibrations. Among these, Flexure Pivot® journal bearings (FPJBs) present some distinct advantages for high-speed application compared to standard TPJBs. FPJBs have typically been used in small high-speed applications such as integrally-geared compressors and multistage high-speed compressors, where the component reliability and rotordynamic stability of the machine are the main targets. Nevertheless, the need for high-speed applications is also present for large compressors. Integral squeeze film damper (ISFD®) are sometimes added in series to the FPJB to reduce stiffness and increase damping [1]. ISFD are not so often adopted by OEMs but in many cases they are selected as a retrofit solution when high level of synchronous/sub-synchronous vibrations are experienced in the field [2]. ISFD can be locked with the insertion of dedicated pins which block the ISFD and the journal bearing can operate stand-alone. If introduced by OEMs in the design phase, ISFDs can represent a bearing-integrated back-up solution. However&nbsp;for machines with high flexibility ratio, ISFD are the only acceptable solution to pass the API rotordynamic requirements.The experimental activity presented in this paper is related to a qualification process whose steps were previously published by the Authors. The first step [3] was a system level test on a small “dummy rotor”&nbsp;(110mm shaft diameter) which confirmed the successful behaviour of the ISFD device both in terms of static performance and rotordynamics. The use of FPJB was moreover validated by the Authors through a system level testing on a high speed rotor having 100mm size journals [4].The last was a component level test, performed on a large FPJB, 280mm shaft diameter, at operating conditions representative of a high-speed process gas compressor [5].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 11 tons) equipped with FPJB and ISFD. This system level testing program was performed in the Authors’ high speed balancing bunker which was equipped with special instrumentation such as: flow meters and pad temperature probes to monitor journal bearing behaviour, displacement probes to monitor rotor vibrations relative to 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 ISFD locked vs. FPJB and ISFD unlocked).[1] Agnew and Childs, "Rotordynamic Characteristics of a Flexure Pivot Pad Bearing With an Active and Locked Integral Squeeze Film Damper", Proceedings of the ASME Turbo Expo 2012,&nbsp;Copenhagen, Denmark. June 11–15, 2012. pp. 551-561.[2]&nbsp;Ferraro, Catanzaro, J. Kim, Massini, Betti Livermore-Hardy, "Suppression of Subsynchronous Vibrations in a 11 MW Steam Turbine Using Integral Squeeze Film Damper Technology at the Exhaust Side Bearing", in Proceedings of the ASME Turbo Expo 2016,&nbsp;Seoul, South Korea. June 13-17, 2016.[3]&nbsp;Gerbet, Catanzaro, Alban, Vannini, "Rotordynamic Evaluation of Full Scale Rotor on Tilting Pad Bearings With Integral Squeeze Film Dampers", Proceedings of ASME IGTI Turbo Expo, Copenhagen, Denmark, 2012.[4] Vannini .&nbsp;“Rotordynamic Validation of an Ultra High Speed Multistage Centrifugal Compressor Stacked Rotor”, Proceedings of ASME IGTI Turbo Expo, Dusseldorf, 2014.[5] Vannini, Cangioli, Ciulli, Nuti, Forte,&nbsp;Kim Livermore-Hardy, “Experiments on a large flexure pivot journal bearing: summary of test results and comparison with predictions”, Proceedings of ASME IGTI Turbo Expo, Phoenix, AZ, 2019.

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

Paper Proceedings: https://asmedigitalcollection.asme.org/GT/GT2021/volume/84898

Turbo Expo 2021

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