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

1967 ◽  
Vol 89 (2) ◽  
pp. 154-165 ◽  
Author(s):  
J. W. Lund
Keyword(s):  
Theoretical Analysis ◽  
Time Constant ◽  
Pressure Ratio ◽  
Journal Bearings ◽  
Restricted Feeding ◽  
Rigid Rotor ◽  
Eccentricity Ratio ◽  
Pneumatic Hammer ◽  
Small Eccentricity ◽  
First Order

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.

Analysis of Pneumatic Instability of Externally Pressurized Porous Gas Journal Bearings

1979 ◽  
Vol 101 (1) ◽  
pp. 48-53 ◽  
Author(s):  
N. S. Rao ◽  
B. C. Majumdar
Keyword(s):  
Theoretical Analysis ◽  
Mass Parameter ◽  
Journal Bearings ◽  
Order Perturbation ◽  
Rigid Rotor ◽  
Eccentricity Ratio ◽  
Dynamic Displacement ◽  
First Order ◽  
Supply Pressure ◽  
First Order Perturbation

A theoretical analysis is presented for the study of pneumatic instability for a rigid rotor supported in externally pressurized porous gas journal bearings. The analysis is based on a first-order perturbation with respect to the amplitude of dynamic displacement of rotor. The variation of threshold mass parameter with feeding parameter is shown. In addition, the effects of supply pressure, eccentricity ratio, L/D ratio, and porosity parameter are investigated and presented in the form of graphs.

The Hydrostatic Gas Journal Bearing With Journal Rotation and Vibration

1964 ◽  
Vol 86 (2) ◽  
pp. 328-336 ◽  
Author(s):  
J. W. Lund
Keyword(s):  
Carrying Capacity ◽  
Journal Bearing ◽  
Load Carrying Capacity ◽  
Restricted Feeding ◽  
Eccentricity Ratio ◽  
Small Vibration ◽  
Small Eccentricity ◽  
First Order ◽  
Load Carrying ◽  
Gas Journal Bearing

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.

Theoretical Analysis of Pneumatic Instability of Externally Pressurized Porous Gas Journal Bearings Considering Velocity Slip

1988 ◽  
Vol 110 (4) ◽  
pp. 730-733 ◽  
Author(s):  
M. C. Majumder ◽  
B. C. Majumdar
Keyword(s):  
Perturbation Theory ◽  
Theoretical Analysis ◽  
Mass Parameter ◽  
Velocity Slip ◽  
Journal Bearings ◽  
Order Perturbation ◽  
Rigid Rotor ◽  
First Order ◽  
First Order Perturbation

An analysis based on first-order perturbation theory is presented for the determination of pneumatic instability of a rigid rotor supported on externally pressurized porous gas journal bearings considering velocity slip. The variation of threshold mass parameter with feeding parameter for various supply pressures and L/D ratios under slip and no slip conditions is shown. It has been observed that there is a little decrease in stability when slip is taken in the analysis.

The Influence of Fluid Inertia on the Dynamic Properties of Journal Bearings

1975 ◽  
Vol 97 (2) ◽  
pp. 159-165 ◽  
Author(s):  
E. Reinhardt ◽  
J. W. Lund
Keyword(s):  
Journal Bearing ◽  
Dynamic Properties ◽  
Journal Bearings ◽  
Graphical Form ◽  
Inertial Forces ◽  
Virtual Mass ◽  
Fluid Inertia ◽  
Eccentricity Ratio ◽  
First Order ◽  
First Order Perturbation

Based on a first-order perturbation solution in a modified Reynolds number an analysis is presented to determine the effect of the fluid film inertial forces on the dynamic properties of a journal bearing. The corrections to the regular amplitude and velocity coefficients are found to be small, but the accompanying acceleration coefficients which may correspond to a virtual mass of several times the mass of the journal itself, could become significant for short rotors. Numerical results are given in graphical form with dimensionless coefficients as functions of the operating eccentricity ratio.

The Hybrid Isothermal Air Lubricated Journal Bearing

1979 ◽  
Vol 101 (4) ◽  
pp. 444-450 ◽  
Author(s):  
V. Kamala
Keyword(s):  
Comparative Study ◽  
Carrying Capacity ◽  
Journal Bearing ◽  
Order Perturbation ◽  
Load Carrying Capacity ◽  
Eccentricity Ratio ◽  
Small Eccentricity ◽  
First Order ◽  
Load Carrying ◽  
First Order Perturbation

This paper analyzes the load-carrying capacity of the hybrid air lubricated journal bearing. Assuming a small eccentricity ratio, a first order perturbation solution is obtained. The air is fed to the bearing through inherent restrictor with feeding holes distributed around the circumference in one, two, and three feeding planes (Fig. 1). The number of feeding holes in each plane is sufficiently large to permit the feeding planes being treated as the line sources. The results are given for the load-carrying capacity and the attitude angle. A comparative study is made of the three types of gas feeding arrangements.

A General Analysis of Multi-Recess Hydrostatic Journal Bearings

1969 ◽  
Vol 184 (1) ◽  
pp. 827-838 ◽  
Author(s):  
P. B. Davies
Keyword(s):  
Energy Dissipation ◽  
Aspect Ratio ◽  
Ambient Pressure ◽  
Pressure Ratio ◽  
Journal Bearings ◽  
The Other ◽  
Eccentricity Ratio ◽  
Optimum Speed ◽  
Ratio Speed ◽  
Induced Flow

A number of assumptions enable the effects of both pressure and velocity induced flow between adjacent recesses to be included in an analysis of multi-recess hydrostatic journal bearings. Consideration of the rate of energy dissipation within a bearing enables an optimum speed variable to be defined which relates the speed of shaft rotation to the other describing parameters involved. The behaviour of a particular orifice compensated bearing of high aspect ratio was investigated at large values of eccentricity ratio and it was revealed that considerable interaction occurred between the recesses. The performance of the bearing was found to be determined jointly by its pressure ratio, speed variable and, significantly, the direction of loading. Considerable variations inload capacity occurred with changes in these parameters and it is shown that the range of operation of multi-recess bearings may be limited as some recess pressures may drop to the ambient pressure. The application of these results to practical designs is suggested.

Characteristics of Externally Pressurized Journal Bearings with Membrane-Type Variable-Flow Restrictors as Compensating Elements

1974 ◽  
Vol 188 (1) ◽  
pp. 527-536 ◽  
Author(s):  
C. Cusano Ms
Keyword(s):  
Aspect Ratio ◽  
Load Capacity ◽  
Pressure Ratio ◽  
Journal Bearings ◽  
Eccentricity Ratio ◽  
Rotating Shaft ◽  
Variable Flow ◽  
Type Variable ◽  
Bearing Stiffness ◽  
Membrane Type

The characteristics of externally pressurized journal bearings with four recesses and with membrane-type variable-flow restrictors as compensating elements are analytically investigated by using the bearing model of Raimondi and Boyd. The effects of the ratio of the recess pressure at zero eccentricity to the supply pressure (pressure ratio), the eccentricity ratio, the compliance of the membrane and the shaft rotation on the lubricant flow rate, the load capacity and the stiffness of these bearings are presented for a given aspect ratio and inter-recess*** land width-to-diameter ratio. For a non-rotating shaft, it is shown that when the bearing operates at zero eccentricity there is a pressure ratio that gives an optimum bearing stiffness. This pressure ratio is a function of the aspect ratio of the bearing only. Using this pressure ratio, data for the load capacity and stiffness of the bearing are presented for an eccentricity ratio that varies from 0 to 0·1. For these data, the membrane compliances used are those that would give an infinite bearing stiffness if the bearing were operating at zero eccentricity.

Sign in / Sign up

Export Citation Format

Share Document