Gas Journal Bearings Research Articles

A Theoretical Analysis of Whirl Instability and Pneumatic Hammer for a Rigid Rotor in Pressurized Gas Journal Bearings

A theoretical analysis is presented for the threshold of instability for a rigid rotor supported in hydrostatic gas journal bearings. Both rotationally induced instability (hybrid instability) and pneumatic hammer are considered. The analysis is based on a first-order perturbation with respect to the eccentricity ratio (i.e., the results are limited to small eccentricity ratios) and makes use of the linearized Ph-method [2, 5, 8]. The pressurized gas is supplied to the bearing through restricted feeding holes in the center plane of the bearing and the analysis takes into account the discreteness of the feeding holes, the feeder hole time constant, and inherent compensation effects. Numerical results are given in form of 16 graphs, showing the threshold of instability as a function of supply pressure ratio, feeding parameter and eccentricity ratio. Also, the effect of the feeder hole time constant is investigated with respect to pneumatic hammer.

Theoretical Analysis of Externally Pressurized Porous Journal Gas Bearing (1st Report)

Theoretical Analysis of Externally Pressurized Porous Journal Gas Bearing (1st Report)

Investigation of Whirl Instability of Externally Pressurized Gas Journal Bearings

Investigation of Whirl Instability of Externally Pressurized Gas Journal Bearings

First Paper: An Analytical Study of the Tilting Pad Gas Lubricated Journal Bearing

Presented in this paper is an analytical method of producing design curves for tilting pad gas journal bearings, with dimensionless parameters chosen in such a way that a single set of curves may be used for any size of bearing with any length to diameter ratio. An analytical solution to the compressible Reynolds equation, based on the linearization by Ausman, is presented in detail. Comparisons are made between the analytical results, numerical results, and experimental findings on the author's rig at Southampton University. Included in the paper is a sample design curve, together with equations for constructing additional curves. The author concludes by briefly outlining his proposed extension of this work.

Theory and Experiments of Squeeze-Film Gas Bearings: Part 1—Cylindrical Journal Bearing

An asymptotic analysis for the cylindrical squeeze-film gas journal bearing has been formulated. An approximate analytical solution is presented. Load-deflection experiments have been performed on a double-film, squeeze-film gas journal bearing. The experimental data confirm the theoretical predictions. Design curves are given for the steady-state radial load capacity and radial stiffness of the cylindrical gas journal bearing.

Plane vibration of the inherently compensated gas journal bearing; analysis and comparison with experiment : P. J. Mullan and H. H. Richardson, ASLE Trans., 7 (1964) 277–287; 16 figs., 1 table, 11 refs.

Plane vibration of the inherently compensated gas journal bearing; analysis and comparison with experiment : P. J. Mullan and H. H. Richardson, ASLE Trans., 7 (1964) 277–287; 16 figs., 1 table, 11 refs.

Pressurized Fixed-Orifice Gas Journal Bearing in Plane Vibration

Technical Briefs Pressurized Fixed-Orifice Gas Journal Bearing in Plane Vibration P. J. Mullan P. J. Mullan IBM Corporation, Poughkeepsie, N. Y. Search for other works by this author on: This Site PubMed Google Scholar Author and Article Information P. J. Mullan IBM Corporation, Poughkeepsie, N. Y. J. Basic Eng. Mar 1965, 87(1): 264-265 (2 pages) https://doi.org/10.1115/1.3650521 Published Online: March 1, 1965 Article history Received: August 21, 1964 Online: November 3, 2011

Stability Analysis of Gas-Lubricated, Self-Acting, Plain, Cylindrical, Journal Bearings of Finite Length, Using Galerkin’s Method

This paper extends the method of Cheng and Trumpler [5] to study stability of plain cylindrical gas journal bearings of finite length. Both equilibrium and stability results have been obtained.

On Gas Lubrication in Turbulent Regime

This paper analyzes first the transient conditions from laminar to turbulent regime for gas lubricated bearings. Then the pressure equation is deduced for self-acting gas-lubricated bearing by using Prandtl’s mixing length theory. A simple method for determining the pressure and the operating characteristics for bearings operating at high numbers H is given, based on an analogy with the corresponding laminar case. The pressure equation is also given for thrust and journal gas bearings under variable forces and velocities. The last two sections examine the influence of turbulence in externally pressurized gas bearings and the influence of inertia forces, respectively. The results obtained show that the turbulence does not alter qualitatively the operation conditions of gas-lubricated bearings. Moreover, the influence of turbulence in self-acting gas bearings is less important than in the case of liquid-film lubrication and even negligible when the bearing operates at high numbers H.

Static and Dynamic Characteristics of Self-Acting, Partial-Arc, Gas Journal Bearings

The Reynolds equation applicable to a self-acting partial-arc gas journal bearing is perturbed in terms of the compressibility number Λ. The resulting set of equations is then put into a standard form and Galerkin’s method is used to obtain bearing loads and stability derivatives. These results are expressed in a power series in Λ.

The Hydrostatic Gas Journal Bearing With Journal Rotation and Vibration

This paper analyzes the load-carrying capacity of the externally pressurized gas journal bearing, including the effect of journal rotation and vibration. The analysis assumes small eccentricity ratio and small vibration amplitude such that a first-order perturbation solution is obtained. The gas is fed to the bearing through orifice-restricted feeding holes around the circumference in one or two feeding planes. The number of feeding holes is sufficiently large to permit treating the feeding planes as line sources. Results are given for the load-carrying capacity and the attitude angle.

Plane Vibration of the Inherently Compensated Gas Journal Bearing; Analysis and Comparison with Experiment

Lumped and distributed parameter analyses of the inherently compensated gas journal bearing are developed for small eccentricity ratios. Curves are presented for static and dynamic gas film forces and for bearing gas flow requirements. Experimental results are compared with the theories for the case of plane vibration. 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 Chicago, Illinois, May 1964.

Gas behaviour and load capacity of hydrodynamic gas journal bearings : J. W. Powell, University of Southampton

Gas behaviour and load capacity of hydrodynamic gas journal bearings : J. W. Powell, University of Southampton

Research on Externally Pressurized Journal Gas Bearing

A theoretical research on externally pressurized journal gas-bearing has been reported by T. Sasaki and H. Mori. In their paper, the experimental data employed in comparison with the theoretical results were for the bearing with a single gas supply hole without restriction. It is common to use externally pressurized gas-bearings with multiple gas supply holes arranged circumferentially and axially. In this paper, a gas-bearing with multiple gas supply holes is designed theoretically and the pressure distribution, flow rate and optimum restriction are examined and compared with the complex potential theory. The experimental results show good agreement with the theoretical results.

A Preliminary Study of Whirl Instability for Pressurized Gas Bearings

Experimental data are presented for the threshold of whirl instability for a short, rigid rotor supported in externally pressurized compensated gas journal bearings. The effects of supply pressures from zero to 200 psig and of radial clearances from 0.0006 to 0.0032 in. are discussed for one type of bearing configuration. A simple stability criterion is presented which explains qualitatively the observed trends. Whirl instability was observed when the frequency of rotation of the shaft exceeded from two to six times the lowest natural frequency of the shaft-bearing system.

Half-Speed Whirl and Load Capacity of Hydrodynamic Gas Journal Bearings

A phenomenological theory of the half-speed whirl of gas bearings is developed; it predicts the existence of four modes of whirl which depend variously on the mass and transverse inertia of the bearing and on the mass and transverse inertia of the shaft. All four modes of whirl have been distinguished experimentally, and related to each other theoretically. From these measurements, it is shown that the half-speed whirl properties of a plain bearing can be considerably improved by cutting an axial slot in the bearing. Further improvement, if required, can be effected by introducing an ovality into the bearing or cutting circumferential grooves in it. The introduction of these anti-whirl devices, however, reduces the load capacity, although measurements have shown the effect is not serious except for the circumferentially grooved bearing

Half-speed whirl and load capacity of hydrodynamic gas journal bearings : S. Whitley, A. J. Bowhill and P. McEwan. Inst. Mech. Engrs., Preprint P 22/62, (1962) 34–45; 16 figs., 3 tables, 9 refs.

Half-speed whirl and load capacity of hydrodynamic gas journal bearings : S. Whitley, A. J. Bowhill and P. McEwan. Inst. Mech. Engrs., Preprint P 22/62, (1962) 34–45; 16 figs., 3 tables, 9 refs.

Analytical and Experimental Study of Externally Pressurized Air Lubricated Journal Bearings

A simplified analysis for calculating the characteristics, such as stiffness, flow, and load of an externally pressurized gas journal bearing, is obtained through a standard one-dimensional flow approach altered to take into account the effect of circumferential pressure variations. From this analysis, it is revealed that bearing stiffness has an optimum which, it is further shown, can be chosen through a proper selection of bearing design parameters, such as radial clearance, upstream resistor, and supply pressure. As the analysis is developed each assumption is experimentally verified. The final predictions of the analysis are also verified. It is felt that the analysis is sufficiently simple to allow comparison of many different bearing configurations, while sufficiently complete to compare very well against experimental measurements in all respects. A comparison is made between the recessed and nonrecessed bearing.

Research on Externally Pressurized Journal Gas Bearing

Research on Externally Pressurized Journal Gas Bearing

Externally Pressurized Step Journal Bearings

An externally pressurized gas journal bearing which achieves its load carrying capability by utilizing flow throttling dams parallel to the direction of rotation is discussed in this paper. Test procedures and equipment used to develop this bearing concept are described. A theoretical method of determining pressure distribution and load carrying capacity for the bearing is presented and correlated with experimental data for non-rotating shafts. Experiments showing the behavior of the bearing under shaft whirl conditions are described and illustrated. Suggested ranges of the design parameters are indicated. The paper also points out advantages accruing from the design simplicity as well as the static and dynamic stability of this bearing concept.