Static and Dynamic Coefficient Measurements for a Thrust Collar Used in an Integrally Geared Compressor Conference Paper uri icon


  • Copyright © 2018 ASME. This paper introduces a test facility specifically designed to measure the axial stiffness and damping coefficients of an oillubricated thrust collar (TC). The geometry, load, and speeds of the test facility are representative of a production integrally geared compressor (IGC). Separate electric motors spin the shafts according to an assumed gear ratio, a pneumatic air piston loader provides a non-contacting, static thrust force, a remotelycontrolled impact hammer delivers a perturbation force, and eddy-current motion probes record the resulting vibration. The paper uses a one degree of freedom (1DOF) axial motion model that neglects the static and dynamic stiffness of the bull wheel and presents estimates of the TC oil-film dynamic coefficients for pinion spin speeds between 5 and 10 krpm, and static loads between 200 and 400 N, using time-domain (log-dec and damped period) and static load-deflection techniques. The measurements show that the TC oil-film develops appreciable stiffness (tens of MN/m), and the 1DOF model used here is inadequate for higher loads. Axial runout on the interfacing surfaces of the test facility TC and bull wheel complicates parameter identification, but time-domain averaging effectively attenuates the runout while preserving the transient vibration that results from the impact hammer. Measurements of the TC oilfilm stiffness, damping and virtual mass coefficients are useful to machinery OEMs or end-users seeking to predict or diagnose subsynchronous vibration in their machine that might be TCrelated.

author list (cited authors)

  • Kerr, T., Crandall, A., Childs, D., & Delgado, A.

citation count

  • 1

publication date

  • June 2018