Experimental study of freely alignable journal bearings .2. Dynamic characteristics

The traditional harmonic excitation method was modified to estimate 16 dynamic force coefficients of two misaligned journal bearings. To avoid the effects of different running conditions on the estimated coefficients, two harmonic forces with different frequencies were excited on the rotor simultaneously and all data were acquired during one test run. The excitation forces and their displacement responses were transferred to the frequency domain in which eight linear (complex) equations are derived. All 16 bearing force coefficients can then be obtained by solving these simultaneous linear equations through one operation. Applicable experimental procedures and data processing techniques are presented. The force coefficients of two circular journal bearings with two axial grooves each are estimated and correlate well with theoretical values when misalignment is considered. Various experimental en ors are discussed and the uncertainty in the estimated coefficients is analyzed.