Optimum Design of Multiple-Hole Inherently Compensated Air Bearings—Part 1: Circular Thrust Bearings

1975 ◽  
Vol 97 (2) ◽  
pp. 221-227 ◽  
Author(s):  
S. Eshghy
Keyword(s):  
Optimum Design ◽  
Flow Model ◽  
Dynamic Pressure ◽  
Journal Bearings ◽  
Entrance Region ◽  
Experimental Measurements ◽  
Partial Recovery ◽  
Air Bearings ◽  
Normal Stiffness ◽  
Thrust Bearings

Analyses of inherently compensated hydrostatic gas bearings of three types are presented. The flow model incorporates empirically the partial recovery of the dynamic pressure in the entrance region. Conditions leading to maximum normal stiffness or/and load are given for air. Analytical results are compared with experimental measurements. Circular thrust bearings are discussed in this article. Subsequent papers will deal with collar thrust and journal bearings.

An Experimental Investigation on Friction Coefficient in Plain Journal Bearings During Start-Up

2008 ◽  
Author(s):  
J. Bouyer ◽  
M. Fillon
Keyword(s):  
Experimental Investigation ◽  
Friction Coefficient ◽  
Journal Bearings ◽  
Radial Clearance ◽  
Experimental Measurements ◽  
Air Bearings ◽  
Specific Pressure ◽  
Thrust Bearings ◽  
Start Up ◽  
Transient Thermal

The start-up friction coefficient is a parameter which is very useful for engineers who design hydrodynamic bearings. It is most often issued from an approximation. Several studies can be found in the literature on this topic but most of them are concerned with air bearings or are only numerical. Some studies are more general and deal with the transient thermal behaviour in journal bearings as well as in thrust bearings. Other studies deal with the friction coefficient during running, at a fixed rotational speed. The aim of this study is to provide experimental measurements of the bush torque during start-up of plain journal bearings, varying the specific pressure. Thus, the friction coefficient at start-up (deduced from measurements) is obtained for four different bearings varying feeding conditions, radial clearance and length.

Measurement of Recovery Factors and Friction Coefficients for Supersonic Flow of Air in a Tube: 2—Results Based on a Two-Dimensional Flow Model for Entrance Region

1952 ◽  
Vol 19 (2) ◽  
pp. 185-194
Author(s):  
J. Kaye ◽  
T. Y. Toong ◽  
R. H. Shoulberg
Keyword(s):  
Boundary Layer ◽  
Supersonic Flow ◽  
Laminar Boundary Layer ◽  
Flow Model ◽  
Variable Mass ◽  
Entrance Region ◽  
Two Dimensional ◽  
Dimensional Flow ◽  
Change Of State ◽  
Two Dimensional Flow

Abstract The first part of a program to obtain reliable data on the rate of heat transfer to air moving at supersonic speeds in a tube has been devoted to measurements made on adiabatic supersonic flow of air in a tube. The details of these measurements have been described in a previous paper. The calculated quantities such as the local apparent friction coefficient, recovery factor, Mach number, and so forth, were obtained from the simple one-dimensional flow model for which the properties of the stream are uniform at any section, and boundary-layer effects are ignored. The analysis of some of the same data given in the previous paper is undertaken here with the aid of a simplified two-dimensional flow model. The supersonic flow in the tube is divided into a supersonic core of variable mass with the fluid remaining in the core undergoing a reversible adiabatic change of state, and a laminar boundary layer of variable mass. The compressible laminar boundary layer increases in thickness in the direction of flow, and then undergoes a transition to a turbulent boundary layer. The two-dimensional flow model is limited here to the region where a laminar boundary layer appears to be present in the entrance region of the tube. The results of the analysis based on the two-dimensional flow model indicate that where the flow in the tube boundary layer appears to be laminar, the measured pressures and temperatures in the tube for adiabatic supersonic flow of air could have been predicted, with sufficient accuracy for engineering problems, from measured data for supersonic flow of air over a flat plate with a laminar boundary layer, and with zero pressure gradient.

An experimental investigation of a microturbine simulated rotor supported on multileaf gas foil bearings with backing bump foils

2017 ◽  
Vol 232 (9) ◽  
pp. 1169-1180 ◽  
Author(s):  
Bo Zhang ◽  
Shemiao Qi ◽  
Sheng Feng ◽  
Haipeng Geng ◽  
Yanhua Sun ◽  
...  
Keyword(s):  
High Speed ◽  
Preliminary Test ◽  
Journal Bearings ◽  
Rotating Machinery ◽  
System Stability ◽  
Test Rig ◽  
Thrust Bearings ◽  
Foil Bearings ◽  
Simulated System ◽  
First Time

Two multileaf gas foil journal bearings with backing bump foils and one set of gas foil thrust bearings were designed, fabricated, and used in a 100 kW class microturbine simulated rotor system to ensure stability of the system. Meanwhile, a preliminary test rig had been built to verify the simulated system stability. The rotor synchronous and subsynchronous responses were well controlled by using of the gas foil bearings. It is on the multileaf gas foil bearings with backing bump foils that the test was conducted and verified for the first time in open literatures. The success in the experiments shows that the design and fabrication of the rotor and the gas foil bearings can provide a useful guide to the development of the advanced high speed rotating machinery.

On the Optimum Groove Geometry for Herringbone Grooved Journal Bearings

2006 ◽  
Vol 128 (3) ◽  
pp. 585-593 ◽  
Author(s):  
A. M. Gad ◽  
M. M. Nemat-Alla ◽  
A. A. Khalil ◽  
A. M. Nasr
Keyword(s):  
Groove Depth ◽  
Radial Force ◽  
Journal Bearings ◽  
Friction Torque ◽  
Performance Characteristics ◽  
Width Ratio ◽  
Geometrical Parameters ◽  
Thrust Bearings ◽  
Circular Groove ◽  
Groove Profile

Recently, herringbone-grooved journal bearings have had important applications in miniature rotating machines. The scribed grooves, on either the rotating or stationary member of the bearing, can pump the lubricant inward, which generates supporting stiffness and improves the dynamic stability, especially for concentric operation. Most of the previous investigations that dealt with herringbone grooved journal bearings and grooved thrust bearings were theoretical. Few experimental attempts for the investigation of the performance characteristics of herringbone grooved journal bearings (HGJBs) and grooved thrust bearings have been done. All these investigations concentrated on rectangular and circular groove profiles of HGJBs. In order to improve the performance characteristics of HGJBs, a new design of the groove profile, the beveled-step groove profile, is introduced. The introduced groove profile is capable of increasing the pressure recovery at the divergence of the flow over the step. In addition, it increases the amount of oil pumped inward over the circular groove profile. Optimization processes were carried out experimentally, in order to obtain the optimal geometry of the introduced groove profile. The optimum geometrical parameters of the groove (groove angle α, groove width ratio β, and groove depth ratio Γ) are 29deg, 0.5, and 2.0, respectively, which give maximum radial force and maximum radial stiffness of the beveled-step HGJB. In order to check the effectiveness of the introduced beveled-step groove profile, the obtained results were compared with that for rectangular groove profile. The comparison shows that the introduced beveled-step HGJBs have higher radial force, higher load carrying capacity, and lower friction torque than the rectangular HGJBs.

Experimentally study of dynamic pressure distribution and oil film forces in journal bearing using ElectroMechanical Film sensor array

2019 ◽  
Vol 234 (4) ◽  
pp. 903-913
Author(s):  
Changmin Chen ◽  
Jianping Jing ◽  
Jiqing Cong ◽  
Chao Ji
Keyword(s):  
Pressure Distribution ◽  
Sensor Array ◽  
Journal Bearing ◽  
Dynamic Pressure ◽  
Vertical Direction ◽  
Journal Bearings ◽  
Film Sensor ◽  
Film Pressure ◽  
Oil Film ◽  
Oil Film Pressure

The acquisition of the oil film pressure and forces on the bearing pads through experimentation is crucial to understanding the characteristics of journal bearing. Lots of efforts had been taken in film pressure measurement, and the pressure was obtained at specified position on the bearing pads. However, due to the space and structure constraint, merely very limited number of the point pressure can be obtained with traditional sensors and acquiring the detail pressure field on whole bearing pad surface is still an open challenge. In this paper, a method based on thin-film sensors technique is proposed and employed to measure the pressure distribution and oil film forces of journal bearings. The measurement is conducted on a cylindrical journal bearing with two axial grooves, and ElectroMechanical Film sensor arrays are designed and laid on the surface of the bearing pads. The oil film pressure is acquired at up to 32 measurement points in total along the bearing pads in both circumference and axial directions. The pressure distribution in a wide rotation speed range is obtained successfully by using fitting algorithm. Furthermore, the oil film forces on horizon and vertical direction are obtained through the integration of the measured pressure filed. The test results prove that it is feasible to measure the oil pressure filed of journal bearings using ElectroMechanical Film piezo-film sensor array.

Effect of a Circumferential Feeding Groove on the Dynamic Force Response of a Short Squeeze Film Damper

1994 ◽  
Vol 116 (2) ◽  
pp. 369-376 ◽  
Author(s):  
G. L. Arauz ◽  
L. San Andres
Keyword(s):  
Flow Model ◽  
Dynamic Pressure ◽  
Squeeze Film ◽  
Dynamic Force ◽  
Force Response ◽  
Squeeze Film Damper ◽  
Circumferential Groove ◽  
Damping Characteristics ◽  
Radial Forces ◽  
Lubricant Viscosity

The effect of a circumferential feeding groove on the dynamic force response of a short length, open end squeeze film damper is studied experimentally. Damper configurations with increasing groove depths and journal orbit radii were tested for several conditions of whirl frequency and lubricant viscosity. Significant levels of dynamic pressure were measured at the circumferential groove, and relatively large tangential (damping) forces are produced at the groove which contribute considerably to the damping characteristics of the SFD test articles. Radial forces of substantial magnitude are determined at the groove and at the thin film land where the squeeze film Reynolds number is typically less than 1. The circumferential groove is thought to induce an inertia like effect into the film land. The experimental results correlate well with the predictions from a groove volume-circumferential flow model developed.

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