Gas-Lubricated Porous Bearings Research Articles

Analysis of stiffness and damping characteristics of externally pressurized gas-lubricated porous bearings under conical mode of vibration

This work gives a theoretical analysis of the dynamic behaviour of externally pressurized gas-lubricated porous bearings with journal rotation and with regard to the stiffness and damping in the conical mode of vibration. The theoretical analysis has been obtained by the simultaneous solution of the continuity equation of flow through a porous medium (derived from a modified version of Darcy's law) and the modified Reynolds equation (governing the pressure in the bearing clearance) by the finite difference method (successive over relaxation, central difference) satisfying the appropriate boundary conditions. The effects of journal speed, feeding parameter, supply pressure, porosity parameter and length-to-diameter ratio on the stiffness and damping coefficients have been investigated. A one-dimensional flow model without velocity slip is considered.

On Slip Flow Considerations in Gas-Lubricated Porous Bearings

A modified form of Reynolds equation is derived for the compressible lubrication of porous bearings. The analysis takes into account two kinds of nonadherence conditions on the sliding surfaces, namely, the slip flow under the influence of molecular mean free path and the slip flow at gas film-porous shell interface. Numerical results are presented to illustrate the relative effects of the two kinds of slip flow conditions on static characteristics of self acting journal bearings.

Stability analysis of externally-pressurized gas-lubricated porous bearings with journal rotation Part 1. Cylindrical whirl

Whirl stability (cylindrical) of externally-pressurized gas-lubricated porous journal bearings, considering one-dimensional flow through the porous matrix, is analysed by a first-order perturbation method. The effect of supply pressure, feeding parameter, porosity parameter and length-to-diameter ratio on the stability is also investigated.

Stability analysis of externally-pressurized gas-lubricated porous bearings with journal rotation Part 2. Conical whirl

The stability analysis of externally pressurized gas journal bearings under conical mode of vibration has been obtained using a first-order perturbation method. The effect of journal speed, feeding parameter, supply pressure, porosity parameter and length-to-diameter ratio on the conical whirl and whirl ratio has been investigated.

The Dynamical Behaviour of Externally Pressurized Gas-Lubricated Unloaded Porous Journal Bearings

In many practical applications, such as with vertical rotors, journal bearings operate with nearly zero eccentricities. In such situations the externally pressurized gas-lubricated porous bearings can offer a viable alternative to the self-acting gas and oil bearings which are generally prone to film induced instabilities under lightly loaded conditions. This paper presents a thorough investigation of the dynamical behaviour of unloaded externally pressurized gas porous bearings. Expensive computations and a large number of design variables involved with the overall performance analysis make it difficult to carry out a comprehensive study of these bearings. However, an attempt has been made to bring out clearly the effect of the more important design variables on the dynamic performance of the bearings.

Closure to “Discussion of ‘Gas-Lubricated Porous Bearings of Finite Length—Self-Acting Journal Bearings’” (1978, ASME J. Lubr. Technol., 101, p. 348)

Closure to “Discussion of ‘Gas-Lubricated Porous Bearings of Finite Length—Self-Acting Journal Bearings’” (1978, ASME J. Lubr. Technol., 101, p. 348)

Gas-Lubricated Porous Bearings of Finite Length—Self-Acting Journal Bearings

The effects of porosity on the performance of gas bearings are investigated. A thin-wall approximation is developed to simplify the coupling between the Reynolds equation in the fluid film and the three dimensional Laplace equation in the porous matrix. The Newton-Raphson method is used to linearize the modified Reynolds equation and the column method is employed to solve the system of linear equations in matrix forms. The solution of a solid-wall bearing is included as a special case. Bearing characteristics are presented in tables and charts for varied permeabilities, slip coefficients, porous layer thicknesses, eccentricity ratios, length-to-diameter ratios, and for a wide range of compressibility number.

Gas-Lubricated Porous Bearings—Short Journal Bearings, Steady-State Solution

The governing equations for a short porous bearing are derived by adopting Ocvirk’s approximation to the general equations for a finite bearing, which are given in a previous paper (reference [1]). Crank-Nicholson’s numerical method and the analytical-numerical technique, which consists of Green function approximation and the local smoothing by integration for a Fourier series, developed in reference [1] are employed to solve the modified Reynolds equation for a wide range of compressibility number. The solution for a solid-wall bearing is obtained as a special case of a porous bearing. Comparison between two thicknesses of porous layer is included.

Closure to “Discussion of ‘Gas-Lubricated Porous Bearings—Short Journal Bearings, Steady-State Solution’” (1977, ASME J. Lubr. Technol., 99, p. 338)

Closure to “Discussion of ‘Gas-Lubricated Porous Bearings—Short Journal Bearings, Steady-State Solution’” (1977, ASME J. Lubr. Technol., 99, p. 338)

Zero-load stability of a rigid rotor supported on pressurized porous gas bearings

A theoretical and experimental investigation of stability characteristics of a rigid rotor mounted on externally expressurized gas-lubricated porous bearings in made. The hydrodynamic fluid film forces of an unloaded journal which undergoes steady whirl are obtained to find limits of the stable region. The results are compared with experimental data and with a similar solution using Galerkin's method. The effect of a feeding parameter, supply pressure, thickness of porous bushing and porosity of bushing material on stability characteristics is also investigated.

Gas-Lubricated Porous Bearings—Infinitely Long Journal Bearings, Steady-State Solution

The general governing equations for finite porous journal bearings with compressible lubricants and slip-flow are derived. A mass content rule is developed for infinitely long porous bearings; an exact solution is established for a gas-lubricated porous bearing with very large bearing number consistent with the mass content rule. An analytic-numerical technique which takes advantage of the linearity of the pressure equation in the porous medium is developed to solve the problem for finite values of compressibility. The results approach those for the solid bearing case as the defined poro-slip parameter β becomes very large.

Closure to “Discussion of ‘Gas-Lubricated Porous Bearings—Infinitely Long Journal Bearings, Steady-State Solution’” (1976, ASME J. Lubr. Technol., 98, p. 462)

Closure to “Discussion of ‘Gas-Lubricated Porous Bearings—Infinitely Long Journal Bearings, Steady-State Solution’” (1976, ASME J. Lubr. Technol., 98, p. 462)

Gas-lubricated porous bearings: A bibliography

The literature pertaining to the theoretical and experimental investigation of gas-lubricated porous bearings is briefly reviewed.

Closure to “Discussions of ‘A Survey of Gas-Lubricated Porous Bearings’” (1969, ASME J. Lubr. Technol., 91, pp. 222–224)

Closure to “Discussions of ‘A Survey of Gas-Lubricated Porous Bearings’” (1969, ASME J. Lubr. Technol., 91, pp. 222–224)

A Survey of Gas-Lubricated Porous Bearings

A review of the literature pertaining to the theory of porous gas bearings, their experimentally observed behavior, and their applications.