Experimental and Theoretical Rotordynamic Characteristics of a Hybrid Journal Bearing

This paper describes an experimental and theoretical investigation of a four-pocket,oil-fed, orifice-compensated hydrostatic bearing including the hybrid effects of journalrotation. The test apparatus incorporates a double-spool-shaft spindle which permitsindependent control over the journal spin speed and the frequencyof an adjustable-magnitude circular orbit, for both forward and backwardwhirling. This configuration yields data that enables determination of thefull linear anisotropic rotordynamic model. The dynamic force measurements weremade simultaneously with two independent systems, one with piezoelectric loadcells and the other with strain gage load cells. Theoreticalpredictions are made for the same configuration and operating conditionsas the test matrix using a finite-difference solver of Reynoldslubrication equation. The computational results agree well with test results,theoretical predictions of stiffness and damping coefficients are typically withinthirty percent of the experimental results.

©1997 The American Society of Mechanical Engineers