Field Methods for Identification of Bearing Support Parameters: Part II — Identification From Rotor Dynamic Response Due to Imbalances

This paper describes a procedure suitable for field implementation that allows identification of synchronous bearing support parameters (force coefficients) from recorded rotor responses to imbalance. The experimental validation is conducted on a test rotor supported on two dissimilar bearing supports, both mechanically complex, each comprising a hydrodynamic film bearing in series with a squeeze film damper and elastic support structure. The identification procedure requires a minimum of two different imbalance distributions for identification of force coefficients from the two bearing supports. Presently, the test rotor responses show minimal cross-coupling effects, as also predicted by analysis, and the identification procedure disregards cross-coupled force coefficients thereby reducing its sensitivity to small variations in the measured response. The procedure renders satisfactory force coefficients in the speed range between 1,500 and 3,500 rpm, enclosing the rotor-bearing system first critical speed. The identified direct force coefficients are in accordance with those derived from the impact load excitations presented in a companion paper [1].