Plain bearing

Summary

A plain bearing, or more commonly sliding contact bearing and slide bearing (in railroading sometimes called a solid bearing, journal bearing, or friction bearing), is the simplest type of bearing, comprising just a bearing surface and no rolling elements. Therefore, the journal (i.e., the part of the shaft in contact with the bearing) slides over the bearing surface. The simplest example of a plain bearing is a shaft rotating in a hole. A simple linear bearing can be a pair of flat surfaces designed to allow motion; e.g., a drawer and the slides it rests on or the ways on the bed of a lathe. Plain bearings, in general, are the least expensive type of bearing. They are also compact and lightweight, and they have a high load-carrying capacity. Design The design of a plain bearing depends on the type of motion the bearing must provide. The three types of motions possible are:

Journal (friction, radial or rotary) bearing: This is the most common type of plain bearing; it

Official source

https://en.wikipedia.org/wiki/Plain_bearing

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Experimental Contribution to the Mechanics of Herringbone Grooved Journal Air Bearings

Ivan Ognjanovic

Gas Lubricated Herringbone Grooved Journal Bearings (HGJB) have long been used in equipment such as navigation systems, optical scanners for laser printers and high speed cameras and disk spindle for flyhead testers. All such applications are characterized by a relatively small size (journal diameter

EPFL2011

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The nonlinear behavior of a rigid rotor supported by herringbone grooved journal gas bearings (HGJBs) was investigated in this study. The two-dimensional narrow groove theory (2D-NGT) was adopted to model the HGJBs. A set of integrated rotor-bearing state equations were built by coupling the rotor motion equations and the bearing Reynolds equation. An implicit integrator with adaptive time step method was used to solve those state equations continuously. Two low-stability HGJBs were implemented to experimentally demonstrate and analyze the appearance of self-excitation motions. The theoretical model was successfully validated by the experimental data on predicting the onset speed of the sub-synchronous vibration of the HGJB-rotor system and the whirl frequency ratio. The predicted limit cycle amplitude increases as the speed increases until the rotor contacts with the bearing surface, which leads to a bearing failure. Forward conical mode dominates the self-excited motion during the whole speed range of self-excited motion. The prediction shows that the HGJB-rotor system can still operate in a stable, even though the rotor is installed vertically, i.e., without static load on the bearings. This is a distinct advantage in comparison to plain bearings. As the static load applies on the bearings increases, the onset speed of sub-synchronous vibration increases as well. For the investigated rotor-bearing system, an increase of the onset speed of sub-synchronous vibration from 36 krpm to 75 krpm is predicted as the static load increases from 0 to 4 times of the rotor weight. This indicates an increased HGJB stability with increased static load. The rotor orbits show complex shapes when the imbalance excitation is considered in the simulation. Both synchronous frequency and whirl frequency are shown in the spectral analysis. Moreover, the speed range of self-excited motion reduces from [38,48] krpm to [40,42] krpm as the imbalance increases from 0 to 40 mgmm.

2021

Externally Pressurised and Hybrid Bearings Lubricated with R134A for Oil- Free Compressors

Adam Molyneaux

This paper discusses the choice and implementation of bearings for oil-free compressors where the system refrigerant is used as the lubricant in externally pressurised and hybrid bearings. The problems of oil contamination in heat pump application is described followed by methods to produce genuine oil-free hermetic systems. Alternative bearing choices are described for high and low speed applications. Theoretical and experimental results are presented showing the effects of turbulence in the bearing clearence and pockets of externally pressurised thrust and journal bearings for a co-rotating scroll compressor operating with r134a. The paper concludes that design methods are now available to enable the incorporation refrigerant lubricated bearing in hermetic oil-free compressors.

1996