The so-called gas-lubricated bearing refers to the interactive bearing that uses gas lubricant for lubrication. Our common gas lubricant is air. In use, the mechanism of the gas-lubricated bearing to form a bearing gas film is the same as that of the liquid-lubricated bearing. Therefore, gas-lubricated bearings have the following advantages and disadvantages when used.

Advantages of gas-lubricated bearings
1. High speed
The speed of the small helium turboexpander has reached 650 000r/min, the linear speed is 238m/s, and it has reached 455x106mm·r/min calculated by the dn value.

2. High precision　
The air film has the effect of homogenizing the error, its accuracy is two orders of magnitude higher than that of the rolling bearing, and the vibration is low and the noise is low.

3. Low friction loss　
The gas viscosity is only one thousandth of the lubricating oil viscosity, so the friction torque caused by the friction in the gas film is three orders of magnitude lower than that of the oil film.

4. Wide applicable temperature range, capable of antigenic radiation 　
The high temperature resistance can reach 300-500℃, and the gas bearing can still work when the temperature is as low as 10K.

5. No pollution
The lubricating gas is generally air or inert gas, which will not cause pollution when discharged into the atmosphere. The bearing has low vibration and low noise, and it does not pollute the environment.

6. Long life
The aerostatic bearing has no direct metal contact, and its theoretical life is infinite. Considering other conditions, it should generally be above 104h. There is metal-to-metal friction when the dynamic pressure gas bearing starts and stops, and the service life is affected to a certain extent, but it is also more than 3000h.

Disadvantages of gas-lubricated bearings
1. Low carrying capacity
Compared with similar oil-lubricated bearings, the carrying capacity of gas-lubricated bearings is about 1 to 2 orders of magnitude lower. According to the bearing capacity per unit area, oil-lubricated bearings are generally (0.5-2) MPa, while gas-lubricated bearings are only (0.02-0.04) MPa.

2. Poor reliability
On the one hand, gas-lubricated bearings are prone to instability, and common air hammer vibration and whirl instability occur. On the other hand, gas-lubricated bearings are stuck, pinched or seized from time to time.

3. The required manufacturing precision is high and the cost is expensive
Because the gas film is very thin, generally between several micrometers and tens of micrometers, the manufacturing precision of the parts is relatively high, which increases the cost. In addition, there are special process requirements for processing spiral grooves, throttle holes, and porous materials, which increase manufacturing difficulty and cost.

4. Harsh working conditions are required
Gas-lubricated bearings require a highly clean working environment and strict compliance with operating procedures to ensure that the bearings work normally without accidents. For this reason, its wide application and commercialization are limited to a certain extent.