0


RESEARCH PAPERS

J. of Lubrication Tech. 1969;91(1):1-16. doi:10.1115/1.3554857.

This is a review of selected publications over the past eight years, dealing with the analysis and design of self-acting, gas-lubricated bearings. An effort has been made to evaluate the advances made both in the understanding of the basic phenomena involved and in the technical analytical ability to deal with them. Whenever possible, design procedures have been referenced and illustrated.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1969;91(1):17-24. doi:10.1115/1.3554851.

The behavior of the pressure distribution within partial-arc and slider bearings under conditions of high-speed operation is investigated to provide an understanding of the basic phenomenon. Both the trailing-edge conditions and side-leakage effects are treated by asymptotic methods. A design example is given in which the edge effects on load capacity are computed as “corrections” to the infinite speed (Λ → ∞ ) solution.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1969;91(1):25-34. doi:10.1115/1.3554888.

An approximate solution for the pressure distribution around a finite length, herringbone grooved journal bearing is derived in analytical form. Some results for the bearing stiffness and attitude angle are presented and compared with experimental results and other theories. The effect of changing the number of grooves is investigated. The validity of the approximate method used is checked by applying it to a simple step slider bearing for which exact solutions are available. The theoretical development is extended to cover the dynamic loading case. Theoretical solutions for the amplitudes of vibration for different frequencies are compared with experimental results.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1969;91(1):37-44. doi:10.1115/1.3554892.

A general description of the behavior of foil bearings is given. This description summarizes and interprets the work of various authors in the field of foil bearings, with particular emphasis on recent publications.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1969;91(1):45-51. doi:10.1115/1.3554894.

The methods of matched asymptotic expansions are used in a systematic manner to obtain the load-carrying capacity of an infinitely long slider bearing correct through terms 0 (1/Λ ) where Λ is the bearing number. The expression for the load is extremely simple. It is shown that the error is 0 (1/Λ2 ), and the procedure for obtaining higher order terms is discussed. Results are given for the case of a converging film thickness with a parabolic shape and for a partial arc journal bearing.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1969;91(1):52-57. doi:10.1115/1.3554896.

Experimental studies were conducted on six rotors, 1 1/2 in. dia by 12 1/4 in. long operating in ambient air to high compressibility numbers. Herringbone-groove geometries and clearances were varied to determine their effect on half-frequency whirl (HFW). All rotors were operated vertically and without any applied radial load. Results show that half-frequency-whirl onset is very sensitive to radial clearance. Limited test results indicate that a fully grooved bearing is more stable than a partially grooved one, other parameters being equal. Generally fair agreement between theory and experiment was achieved for predicting HFW onset speeds.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1969;91(1):60-68. doi:10.1115/1.3554900.

Current methods in gas lubrication have been used in this paper to analyze the gas-film characteristics in a high-speed, face-type gas seal. Detailed analyses are presented for two different surface geometries, the spiral-groove-orifice seal and the shrouded Rayleigh step seal. Results are presented in three parts. The first part shows the performance of a spiral-groove seal without the orifices, and also the difference in performance when the grooves are located at the high pressure, low pressure, or both sides. The second part gives typical performance of a nonparallel film profile for the spiral-groove-orifice seal as well as for the shrouded Rayleigh step seal. In the last part, a comparison is made between the two seal geometries on their tolerance to coning or dishing under a constant seal load.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1969;91(1):69-78. doi:10.1115/1.3554901.

The objective of this paper is to study the effect of molecular mean free path on the steady-state performance characteristics of a spiral-grooved thrust bearing operating in extremely thin film and/or low ambient pressure environments. Numerical results for the most popular three versions of the spiral-grooved designs are presented. These results reveal that the effect of slip boundary conditions could contribute substantial reduction, in performance. Helium is the worst gas lubricant in this sense because of its high Knudsen number. The slip-flow corrected results check well with recently published experimental data [11].

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1969;91(1):79-86. doi:10.1115/1.3554902.

In order to determine the qualitative effect of lubricant compressibility in groove bearings, the Whipple’s method already used in several papers references [1–8]1 is employed, but eliminating, however, certain approximations, especially the consideration of constant pressure gradients perpendicular to the groove edge. Under these conditions one shows that the analysis is consistent with the normal limiting solution of ph = const, which takes place when the compressibility number increases indefinitely. Grooved bearings behave thus similarly to the usual step bearings, but they operate at a much smaller local compressibility number. Some considerations concerning the values of the compressibility number at which the compressibility effect must be taken into account are given. An exact solution obtained by numerical methods over a no-throughflow groove-ridge pair with cyclic conditions is presented over the entire range of compressibility numbers of interest to show the actual influence of local compressibility.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1969;91(1):87-103. doi:10.1115/1.3554903.

Calculated load capacity and friction for complete pivoted-pad journal bearings are presented, for use in design computations. Dimensionless numerical results are given for the following variations in bearing geometry: 3 and 5 pads, L/D ratios of 1/2 to 1, pivot locations of 40, 50, and 60 percent, on pivot and between pivot loading, and ratios of “assembled” to “ground” clearance of 0.6, 0.8, and 1.0. The numerical results are an extension of the work of Castelli, et al., reference [1],1 and were generated in the same manner i.e., numerical solution of Reynolds’ equation by digital computer. Laminar, incompressible flow, and subambient pressures in diverging portions of the films were assumed. Illustrative numerical examples are included and significant conclusions with respect to major variables (L/D ratio, number of pads, clearances, pivot location, load direction) are drawn from the range of data produced.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1969;91(1):104-112. doi:10.1115/1.3554841.

An analysis, based on the narrow groove theory, is presented for the closed, spiral-grooved spool bearing. Designs optimized for static stiffness are obtained for range of values of the groove extent parameter Y , and the characteristics of these designs under oscillatory motion are investigated over a wide frequency spectrum. It is shown that the geometry of the boundaries common to thrust and journal sections has an appreciable effect on the dynamic compliance of the bearing, and that a relief volume between the bearing sections can give rise to a gas film resonance, at which the compliance is strongly dependent on the dimensions of this volume. The beneficial effect of a thrust-bearing seal region with respect to this type of resonance is demonstrated, and it is shown that a design for optimum static stiffness differs considerably from one for optimum dynamic stiffness. It is the prediction of this analysis that a small sacrifice in static performance can lead to considerable gains in the performance under dynamic conditions.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1969;91(1):113-119. doi:10.1115/1.3554842.

The linearized theory for the stability of self-acting gas bearings is extended to include bearing systems with noncircular members or additional elements of flexibility and damping. The theory offers a satisfactory explanation for the unusual behavior of a bearing system with a three-lobed rotor, including the whirl at low speeds and the whirl cessation. A comparison between the theory and experiments for a flexibly mounted bearing system shows that the theory can be applied to predict the stability boundaries of bearing systems with additional elements of flexibility. A new type of bearing apparatus is proposed in which it would be possible to obtain information about bearing stability without operating at the stability boundary.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1969;91(1):120-125. doi:10.1115/1.3554843.

A technique for the solution of time-dependent foil bearing problems is presented in this report. Solutions obtained for typical disturbances which are introduced into the bearing indicate that they are swept out at a speed of, essentially, U/2. The effects of higher foil stiffness on this phenomenon are found to be small.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1969;91(1):126-131. doi:10.1115/1.3554844.

Two parallel circular disks are separated by a viscous fluid; one of the disks oscillates sinusoidally in a direction normal to its plane and the other is at rest. A solution to this problem is presented and compared with previous approximate solutions and experimental results. It is suggested that further experimental results are required.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1969;91(1):132-137. doi:10.1115/1.3554845.

The steady-state ph distribution and the load support capability for a squeeze-film bearing in the form of a sphere, or portions of a sphere, are given for two cases, (a) when the sphere pulsates radially and (b) when the sphere motion is along the polar axis. Both small parameter and finite-difference results are given for loads in the radial and polar directions. It is shown that considerably more load support in both the radial and the polar directions is developed when the sphere pulsates radially. It is further shown that the load support can be improved by removing a portion of the sphere near the pole, thus venting the bearing to the ambient pressure.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1969;91(1):138-148. doi:10.1115/1.3554846.

An experiment is described in which the motion of the supported mass was the main contributor to the generation of the squeeze film. An analysis was performed and a computer program written to predict the motion of the supported mass. Good agreement is shown between the analysis and the computer program and the experiment, except that two of the observed operation points cannot be verified.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1969;91(1):149-160. doi:10.1115/1.3554847.

The stability and vibration response of a spherical squeeze-film hybrid bearing were analyzed theoretically. Since the squeeze frequency is typically much higher than the vibration frequency, the asymptotic analysis for large squeeze number can be applied here. Perturbation solutions about the radially concentric position were obtained for small vibration amplitudes and small radial displacement. There is no limitation, however, in the values of vibration number (so long as it is small in comparison with the squeeze number), compressibility number, axial displacement ratio, and excursion ratio. Dynamic bearing reactions were computed based on the perturbation solutions. Results indicate that a spherical squeeze-film bearing is always stable in the axial direction. In the radial direction, however, instability about the radially concentric position is possible when there is journal rotation, the frequency of instability is exactly one half of the rotational frequency; the system would be stable if the mass is kept below the critical value. The analysis can be readily extended to compute the response to vibratory excitation in either the axial or the radial direction.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1969;91(1):161-165. doi:10.1115/1.3554848.

The evolution of gas bearing technology during the period since 1959 is reviewed. References to significant literature on externally pressurized gas bearings are cited for the benefit of designers.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1969;91(1):166-170. doi:10.1115/1.3554849.

An “unevenly distributed supercharging” pattern is suggested for treating externally pressurized bearings. The scheme simplifies the problem and is applicable in calculating any type of externally pressurized bearings Results of numerical integration of Reynolds’ equation for a section spherical bearing using this treatment are given.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1969;91(1):171-180. doi:10.1115/1.3554850.

The inherent limitations of load capacity and stability of hydrodynamic gas-lubricated bearings can be reduced by introducing external pressure and creating a hybrid bearing. Numerical computerized analyses of a hybrid journal bearing are discussed; separate developments are presented for steady-state and dynamic characteristics. The steady-state analysis provides performance over a wide range of operating parameters; the more complicated and lengthy dynamic analysis determines stability of the bearing-rotor system using geometry based upon steady-state results. Simplified flow charts of the computer programs are included. The analyses are applied to the preliminary design of a hybrid journal bearing.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1969;91(1):181-193. doi:10.1115/1.3554854.

In order to make clear the characteristics of externally pressurized gas bearings, several mathematical flow-models are constructed by making proper chains of fundamental and elemental flow-patterns and pressure changes for circular thrust bearings with single central supply hole. The suggested flow-models, which are the combination of rather simple elements to make the mathematical analysis easy, are quite effective to explain the pressure distributions, the load capacity, and the rate of flow observed experimentally over wide operating conditions. And also, these flow-models make it possible to understand the effects of the inherent compensation, the so-called restrictions in series and the occurrence of shock wave.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1969;91(1):194-198. doi:10.1115/1.3554855.

The problem of gas lubrication is examined by taking into account the energy equation and variation of viscosity with temperature. The velocity profiles and the pressure differential equation are deduced. When the temperatures T0 , T1 of the two lubricated surfaces are constant, simple corrections can be obtained in order to estimate the influence of unequal temperatures of the two surfaces on pressure distribution, load capacity, and friction stresses in self-acting films and on pressure distribution and mass flow in externally pressurized bearings. However, as the influence of the transversal heat transfer manifests only through the intermediary of the variation of viscosity with temperature, the isothermal analysis can further on be used, provided that one takes a mean value for the viscosity, corresponding to a mean temperature Tm = (T0 + T1 )/2.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1969;91(1):199-202. doi:10.1115/1.3554856.

The behavior of an infinitely long journal bearing using an ionized gas lubricant in which a magnetic field is applied axially and an electric field is applied transversely to the fluid film is investigated theoretically. It is found that in the absence of an applied electric field the behavior of the bearing with the ionized gas is not much different from that of a bearing using a neutral gas even at large Hartmann numbers. However, by application of the crossed magnetic and electric fields the pressure distribution in the lubricating film can be altered significantly. Various curves showing the effect of the Hartmann, Hughes, and Harrison numbers on the pressure distribution, film load-carrying capacity, and the locus of the journal center in the bearing are presented and discussed.

Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1969;91(1):203-208. doi:10.1115/1.3554858.

The paper examines some of the possibilities of MGD lubrication by considering some typical examples of external electromagnetic conditions and some simple types of bearings. Thus, for self-acting films, the case when an external tangential magnetic field combined with a transversal electrical field is studied. Pressures and load capacity are thus improved and, in addition, the friction forces can be diminished and even eliminated. For externally pressurized films, insulated surfaces subjected to an external transversal magnetic field can reduce the flow, provided that the Hartmann number has a sufficiently high value. Finally, it is pointed out that it is possible to produce pressures by electromagnetic means only. The electromagnetic pumping effect is produced, for instance, when a transversal electrical field is applied, combined with a tangential magnetic field, even when both lubricated surfaces are at rest. Some considerations concerning the practical possibilities of obtaining an electrically conductive gas at relatively low temperatures are also given.

Commentary by Dr. Valentin Fuster

DISCUSSIONS

J. of Lubrication Tech. 1969;91(1):44. doi:10.1115/1.3554893.
FREE TO VIEW
Abstract
Commentary by Dr. Valentin Fuster
Commentary by Dr. Valentin Fuster
Commentary by Dr. Valentin Fuster
Commentary by Dr. Valentin Fuster
Commentary by Dr. Valentin Fuster
Commentary by Dr. Valentin Fuster
Commentary by Dr. Valentin Fuster
Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1969;91(1):215. doi:10.1115/1.3554874.
FREE TO VIEW
Abstract
Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1969;91(1):215. doi:10.1115/1.3554875.
FREE TO VIEW
Abstract
J. of Lubrication Tech. 1969;91(1):215-216. doi:10.1115/1.3554876.
FREE TO VIEW
Abstract
Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1969;91(1):216. doi:10.1115/1.3554877.
FREE TO VIEW
Abstract
J. of Lubrication Tech. 1969;91(1):216. doi:10.1115/1.3554878.
FREE TO VIEW
Abstract
Commentary by Dr. Valentin Fuster
Commentary by Dr. Valentin Fuster
J. of Lubrication Tech. 1969;91(1):222-224. doi:10.1115/1.3554884.
FREE TO VIEW
Abstract
Commentary by Dr. Valentin Fuster
Commentary by Dr. Valentin Fuster

Sorry! You do not have access to this content. For assistance or to subscribe, please contact us:

  • TELEPHONE: 1-800-843-2763 (Toll-free in the USA)
  • EMAIL: asmedigitalcollection@asme.org
Sign In