THEORETICAL AND EXPERIMENTAL COMPARISONS FOR ROTORDYNAMIC COEFFICIENTS OF A HIGH-SPEED, HIGH-PRESSURE, ORIFICE-COMPENSATED HYBRID BEARING

Comparisons are presented between measurements and predictions for a 7 6.2 mm diameter, high-speed (24,600 rpm), high-pressure (7.0 MPa), hyb rid bearings using warm (54 degrees C) water as a test fluid. ''Hybrid '' refers to combined hydrostatic and hydrodynamic action. Test result s are presented for an orifice-fed, square-recess configuration with f ive recesses. Data are provided for rotordynamic coefficients includin g direct and cross-coupled stiffness, direct damping, direct added-mas s coefficients, and the whirl-frequency ratio. Experimental results ar e compared to predictions from an analysis by San Andres (1990a), whic h accounts for both temporal and convective acceleration terms in the fluid film. San Andres' development uses an orifice discharge coeffici ent to model the pressure drop from supply pressure to recess pressure . With experimentally determined discharge-coefficient values as input , good agreement is obtained between theory and experiment. However, p redictions are sensitive to changes in the orifice discharge coefficie nts.