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Journal ArticleDOI

The Effect of Geometry Variations on Hydrodynamic Bearing Performance

01 Jan 1966-Tribology Transactions (Taylor & Francis Group)-Vol. 9, Iss: 4, pp 411-419
TL;DR: In this article, the effect of imperfections of the stationary bearing component becomes a junction of their location relative to the pressure producing region of the bearing and creates a difficult problem in predicting characteristic performance results.
Abstract: In fabricating gas bearing components, it is necessary to establish allowable tolerances on out-of-roundness, taper and surface finish of the parts. Several evaluations of the effects of these variable on bearing performance characteristics were conducted in order to determine reasonable bearing tolerances. It was found that, generally, variations in diameter of the rotating member can be averaged out for predicting performance. Unfortunately, the effect of imperfections of the stationary bearing component becomes a junction of their location relative to the pressure producing region of the bearing and creates a difficult problem in predicting characteristic performance results. Contributed by the ASLE Technical Committee on Bearings and Bearing Lubrication and presented at the Annual Meeting of the American Society of Lubrication Engineers held in Pittsburgh, Pa., May 3–5, 1966.
Citations
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Dissertation
01 Jan 2000
TL;DR: Breuer et al. as mentioned in this paper performed numerical simulations of gas-lubricated journal bearings for microfabricated machines with specialized tools and found a large-amplitude whirling mode on both sides of the fixed-point threshold speed, in agreement with experimental observation.
Abstract: Numerical simulations of gas-lubricated journal bearings for microfabricated machines are performed with specialized tools. To maximize flexibility, an orbit method formulation is chosen for the primary tool. Its pseudospectral fluid equation solver enables run-time resolution adjustment while maintaining the efficiency advantage of spectral methods. A design framework is established for microfabricated bearings, including several new charts that reflect the unique constraints of MEMS. A duality between applied load and imbalance level is demonstrated and a method for experimentally determining appropriate loads for unknown imbalance is suggested. A large-amplitude whirling mode is shown to exist on both sides of the fixed-point threshold speed, in agreement with experimental observation. A quasi-static method for calculating shock tolerance is suggested and evaluated against unsteady simulations. Simulations of loads applied via noncircumferentiallyuniform pressure at the bearing end are shown to increase the attitude angle and decrease the allowable nondimensional mass compared to the equivalent gravity-loaded case. Furthermore, the associated axial pressure gradients are shown to produce a hydrostatic stiffness via inertial effects. A nondimensional model is constructed for this stiffness and its dependence on various parameters is studied. It is shown that the load capacity advantage reported in the literature for noncircular bearings can be canceled by microfabrication constraints. The stability advantage, however, survives. Tapered axial clearance is shown to have an extremely deleterious effect on performance while bowed clearance proves less detrimental. Navier-Stokes solutions of infinite-length bearings with unity inertial parameters are performed using a second specially-built tool. Little change is found in the steady-state results from inertial and curvature effects in the MIT microengine’s parameter space. Thesis Supervisor: Kenneth S. Breuer Title: Visiting Associate Professor of Aeronautics and Astronautics

36 citations


Cites methods from "The Effect of Geometry Variations o..."

  • ...This behavior has also been observed experimentally by Reynolds and Gross [26] and Wilson [60] for gas bearings....

    [...]

Dissertation
01 Jan 2000
TL;DR: Breuer et al. as discussed by the authors presented a high-order, efficient scheme for computing both the steady and unsteady hydrodynamic properties of the rotor/gas film dynamical system along with comprehensive calculations for this class of plain cylindrical, gas journal bearing.
Abstract: A macro-scale experimental test facility for investigating high-speed gas bearings for MEMS devices such as the MIT Micro-Engine is presented along with results from subsequent experiments. It is shown that the bearings required by such MEMS devices fall outside the usual range of design parameters for conventional gas lubrication systems. Due to the unorthodox design of the bearings, a new "hybrid" mode of operation is introduced along with the traditional hydrodynamic regime. The new hybrid mode is exploited to implement a novel in-situ rotor balancing scheme which enables hydrodynamic operation. Analysis for both modes of operation is presented along with experimental results. A high-order, efficient scheme for computing both the steady and unsteady hydrodynamic properties of the fully coupled, rotor/gas film dynamical system is presented along with comprehensive calculations for this class of plain, cylindrical, gas journal bearing. The scheme is then used to perform a generalized eigenvalue analysis on the compressible, unsteady system which reveals a new type a hydrodynamic instability. From a fundamental understanding of the bearing physics, strategies for operating MEMS devices with this class of bearing are deduced and minimum requirements for the accompanying measurement systems are established. Ancillary issues such as axial equilibrium of the rotor are discussed in detail. Thesis Supervisor: Prof. Kenneth S. Breuer Title: Visiting Associate Professor

30 citations


Cites background from "The Effect of Geometry Variations o..."

  • ...The work of Wilson [70] marked a departure from earlier work on plain, cylindrical, journal bearings by addressing more advanced topics such as the effect on hydrodynamic whirl instability of rotor non-circularity, rotor taper, bearing surface finish, and moment loading....

    [...]

Journal ArticleDOI
TL;DR: A journal bearing test rig was designed and constructed to test the behavior of journals with wavy surfaces, the circumferential undulations being varied both in amplitude and in number as discussed by the authors.

26 citations

Journal ArticleDOI
TL;DR: In this article, the effect of misalignment of journal in conjunction with geometric imperfections of journal on the performance of four pocket hybrid journal bearing system has been investigated and the numerically simulated results indicate that the performance gets significantly deteriorated due to the geometric imperfection and mis alignment of journal.

25 citations

Journal ArticleDOI
TL;DR: In this paper, the effect of manufacturing errors on the performance of large tilting pad thrust bearings has been investigated, following a CFD-based Thermohydrodynamic analysis of a single pad.

20 citations

References
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Journal ArticleDOI
TL;DR: In this article, a perturbation analysis is used to find the torque generated by a misaligned journal bearing, and the angular displacement of a torque-loaded journal is calculated graphically in terms of non-dimensional parameters.
Abstract: A perturbation analysis is used to find the torque generated by a misaligned journal bearing (or, equivalently, to find the angular displacement of a torque-loaded journal). Results are presented graphically in terms of nondimensional parameters. (auth)

11 citations

Journal ArticleDOI
John R. Rice1
TL;DR: In this article, design curves for misalignment torques are presented which are valid for high eccentricity ratios and instead of perturbation analysis, numerical analysis is used to solve the governing Reynolds equation.
Abstract: Design curves for misalignment torques are presented which are valid for high eccentricity ratios. Instead of perturbation analysis, numerical analysis is used to solve the governing Reynolds equation. A comparison of the two methods is also included.

9 citations