Rotordynamic and thermal analyses of compliant flexure pivot tilting pad gas bearings were performed. First, compliant flexure pivot tilting pad gas bearings with pad radial compliance (CFTPBs) were introduced and designed for high-speed oil-free micro turbomachinery. The pad radial compliance was for accommodation of large rotor growth at high speeds. Parametric studies on pivot offset, preload, and tilting stiffness were performed using non-linear orbit simulations and coast-down simulations for an optimum design. Second, coast-down tests for imbalance response and stability of typical rotor-bearing system with a rigid rotor and two CFTPBs designed from the above design studies were conducted over operating speeds up to 55 krpm. Prediction of synchronous rotordynamic responses was made in terms of critical speed for various imbalance modes by using a rotordynamic analysis software (XLTRC), combined with dynamic force coefficients from the perturbation analysis. For stability analyses, a generalized orbit simulation program was developed considering both the translational and angular rotor motions with two different bearings. Linear stability analyses for the conical vibration mode were also performed by using XLTRC and the perturbation analysis based on the Lund method. Predictions of whirl speed showed good agreement to the tests, but the estimated onset speed of instability appeared lower than the measured instability. Finally, a new thermo-hydrodynamic analysis model of a typical rotor-bearing system with CFTPBs was presented, accompanying linear perturbation analyses to investigate thermal effects on the rotordynamic performance. A numerical procedure was established for solving the generalized Reynolds equation, the 3-D energy equation, and the associated boundary conditions at the pad inlet flow and solid walls (rotor and pad) simultaneously. Parametric studies were conducted on nominal clearance and external load. Nominal clearance showed significant influence on temperature fields, and external load had uneven thermal effects among pads. Case studies with heat flux and temperature boundary conditions on the rotor end surface were performed to simulate various working conditions of the bearing. Large rotor thermal growth due to the high rotor temperature showed noticeable influence on rotordynamic performance by increasing direct stiffness and damping coefficients.

A polycrystalline diamond was tested as a bearing material for a tilting pad thrust bearing to be used in an electric submersible pump, which elevates process fluids from the bottom of well bores. The goal of this study was to compare the PCD to a current best of technology, which is stainless steel with an engineering polymer.This study found that PCD can handle larger loads than current technology but is limited in size due to diamond sintering and manufacturing constraints. The maximum size is Ø75mm.

A polycrystalline diamond was tested as a bearing material for a tilting pad thrust bearing to be used in an electric submersible pump, which elevates process fluids from the bottom of well bores. The goal of this study was to compare the PCD to a current best of technology, which is stainless steel with an engineering polymer.This study found that PCD can handle larger loads than current technology but is limited in size due to diamond sintering and manufacturing constraints. The maximum size is Ø75mm.

Static characteristics and rotordynamic coefficients were experimentally determined for a four-pad tilting-pad journal bearing with ball-in-socket pivots in loadbetween- pad configuration. A frequency-independent [M]-[C]-[K] model fit the measurements reasonably well, except for the cross-coupled damping coefficients. Test conditions included speeds from 4,000 to 12,000 rpm and unit loads from 0 to 1896 kPa (0 to 275 psi). The test bearing was manufactured by Rotating Machinery Technology (RMT), Inc. Though it has a nominal diameter of 101.78 mm (4.0070 in.), measurements indicated significant bearing crush with radial bearing clearances of 99.6 μm (3.92 mils) and 54.6 μm (2.15 mils) in the axes 45º counterclockwise and 45º clockwise from the loaded axis, respectively. The pad length is 101.6 mm (4.00 in.), giving L/D = 1.00. The pad arc angle is 73º, and the pivot offset ratio is 65%. The preloads of the loaded and unloaded pads are 0.37 and 0.58, respectively. A bulk-flow Navier-Stokes model was used for predictions, using adiabatic conditions for the bearing fluid. Because the model assumes constant nominal clearances at all pads, the average of the measured clearances was used as an estimate. Eccentricities and attitude angles were markedly under predicted while power loss was under predicted at low speeds and very well predicted at high speeds. The maximum detected pad temperature was 71ºC (160ºF) and the rise from inlet to maximum bearing temperature was over predicted by 10-40%. Multiple-frequency force inputs were used to excite the bearing. Direct stiffness and damping coefficients were significantly over predicted, but addition of a simple stiffness-in-series model substantially improved the agreement between theory and experiment. Direct added masses were zero or negative at low speeds and increased with speed up to a maximum of about 50 kg; they were normally greater in the unloaded direction. Although significant cross-coupled stiffness terms were present, they always had the same sign. The bearing had zero whirl frequency ratio netting unconditional stability over all test conditions. Static stiffness in the y direction (obtained from steadystate loading) matched the rotordynamic stiffness Kyy (obtained from multiple-frequency excitation) reasonably at low loads but poorly at the maximum test load.