What is an air bearing
Bearing, I believe everyone will be familiar with, our commonly used rolling bearing should be the most familiar, it is an important part of contemporary machinery and equipment. So what is an air bearing?
Gas bearing: A plain bearing that uses gas as a lubricant. The most commonly used gas lubricant is air, but nitrogen, argon, hydrogen, helium or carbon dioxide can also be used as required.
In gas compressors, expanders and circulators, the working medium is often used as a lubricant.
Air bearing refers to the bearing that supports the load with the help of the pressure air film formed between the surface of the bearing sliding pair, and the surface of the sliding pair is completely separated by the air film when working.
Air bearings belong to the fluid sliding bearings in the sliding bearings, which are fluid lubricated when working, and their lubricating medium is air.
Classification of air bearings
According to the formation mechanism of pressure air film, air bearings are mainly divided into two categories: aerodynamic bearings and aerostatic bearings.
The pressure air film of the aerodynamic bearing is formed by bringing air into the area of convergence between the surfaces of the sliding pairs by the mutual movement of the sliding pairs, and the air film is roughly wedge-shaped. Since aerodynamic bearings do not require an external air source, they are also called "self-acting bearings".
The pressure air film of the aerostatic bearing is formed by the external compressed air being introduced through the throttle between the surface of the sliding pair. Aerostatic bearings require a clean external air supply.
Air bearing features
(1) Extremely low friction resistance
Since the viscosity of gas is much lower than that of liquid, the viscosity of air at room temperature is only 1/5000 of that of No. 10 mechanical oil, and the friction resistance of the bearing is directly proportional to the viscosity, so the friction of gas bearings is lower than that of liquid lubricated bearings.
(2) Wide range of applicable speeds
The friction resistance of the gas bearing is low, the temperature rise is low, and the temperature rise does not exceed 20~30 °C when the speed is as high as 50,000 rpm, and the speed is even as high as 1.3 million rpm. Hydrostatic bearings can also be used for very low speeds, even zero speeds.
(3) Wide range of applicable temperatures
The gas remains gaseous over a wide range of temperatures, and its viscosity is minimally affected by temperature (the viscosity increases slightly at increasing temperatures, e.g. from 20°C to 100°C, the air viscosity increases by 23%), so the gas bearings can be used in a temperature range of -265°C to 1650°C.
(4) Low bearing capacity
The bearing capacity of the hydrodynamic bearing is directly proportional to the viscosity, and the bearing capacity of the pneumatic bearing is only a few thousandths of the same size of the hydrodynamic bearing. Due to the compressibility of the gas, there is a limit to the load carrying capacity of the gas dynamic bearing, and the load per unit projected area can only be increased to 0.36 MPa.
(5) High processing accuracy requirements
In order to improve the load-bearing capacity and air-film stiffness of gas bearings, a bearing clearance (less than 0.015 mm) is usually used that of liquid-lubricated bearings, and the accuracy of the parts needs to be improved accordingly.
Application of air bearings
Air bearing is a new type of bearing that uses air elastic potential energy to play a supporting role.
The only lubricant used is air; Air bearing technology is therefore ideal for workpieces that must be free of contamination or for working environments.
In air bearings, the balls are replaced by air cushions. Perhaps one of the most well-known applications for air bearings is hovercraft.
A huge fan blows air underneath the hovercraft, blocking the escape of air through an elastic rubber "skirt". The high air pressure generated under the hovercraft supports the weight of the hull and thus makes it float on the air cushion.
The application of gas bearings is becoming more and more extensive and has been extensively and intensively studied. At present, gas bearings can be used in textile machinery, cable machinery, instrument machine tools, gyroscopes, high-speed centrifugal separators, dental drills, refrigerators running at low temperatures, hydrogen expanders and gas circulators running at high temperatures.
Post time: Mar-28-2025
