Gas and hydrodynamic bearings have been studied at LUT since 1981.
The design work is based on in-house simulation programs, which are used to predict the properties and stability of the bearings before manufacturing.
Gas Bearings
The great advantage of a gas dynamic bearing is its capability to generate the loading force from the surrounding gas. The load is generated from the friction of the relative movement of the thin gas layer between the rotating shaft and stationary bearing pad. Other advantages are compact size, low friction, no contact between the shaft and pad, operation in low and high temperatures, possibility to use high speed, no external pressure devices, long operational life in clean conditions, low noise and vibration levels.
The disadvantages of gas bearings are low loading capacity, high precision requirements, risk for dynamic instability and risk for wear during start and stop,
Dynamic gas bearings have been designed and manufactured for rotational speeds from 25 000 rpm to 250 000 rpm.
The static gas bearing needs externally pressurized gas, which separated the rotational and static bearing surfaces. Usually the gas is directed through nozzles in the bearing body and exits from bearing boundaries.
The advantages are low friction, no contact between the shaft and pad, operation in low and high temperatures, high loading capacity, long operational life in clean conditions, possibility to use high speed, low noise and vibration levels. The disadvantages of gas bearings are high precision requirements and the need of an external compressor.
The axial gas static bearing used in the gas bearing demonstration unit of the Laboratory. The diameter of the rotating bearing disc is 120 mm. The gas is supplied with blue pneumatic pipes through nozzles in the yellow bearing body. The stationary bearing is in a gyroscopically stationed in order to get the bearing components accurately parallelled.
Static gas bearings have been designed and manufactured for rotational speeds from 12 000 rpm to 60 000 rpm.
Liquid bearings
Liquid water and toluene bearings have been used in pumps and ORC power plants in LUT research. The advantages are compact size, high loading capacity and possibility to use high speed. The disadvantages of liquid bearings are rather high friction and the need of an external compressor.
Liquid bearings have been designed and manufactured for rotational speeds from 25 000 rpm to 150 000 rpm.
One doctoral thesis and one licentiate’s thesis have been done on the topic (Sallinen).
Tribological Durability of Compressor Safety Bearings is very important. Magnetic bearings are very reliable, and they are also protected against power failures. Despite of this, machines with magnetic bearings are usually equipped with safety bearings, which are required to stay in working order for three shutdowns. A theoretical and experimental study of suitable safety bearing materials and types has been conducted at LUT.