What is compressed air?

The basic principles of compressed air

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What is compressed air?

Let's get back to basics; what is compressed air and what are the basic principles? In short, compressed air is created by one of two basic principles of compression of air (or gas): positive displacement compression and dynamic compression.

Positive displacement compression is the most common form of air compression, with piston and rotary screw compressors being the most common types of positive displacement machines. However scroll, tooth and vane are also other forms of positive displacement compression technology.


In positive displacement technique, compressed air is created by decreasing the air volume by pushing it through a compression chamber to another one or more chambers of decreasing size which are closed off from the inlet side; as more air gets pushed in, the air volume is reduced and compressed air is created. When the correct pressure is reached the air is discharged. A simple example is the bicycle pump.


Turbo air compressors are the most common type of dynamic air compressors. To explain dynamic air compression in a simplified way would be that larger volumes of air are propelled into a small outlet, hence getting compressed. The working principle of dynamic air compression is that air is drawn between blades on a rapidly rotating impeller and the air is accelerated to a high velocity. The air is then discharged through a diffuser, where it is transformed into a static pressure. Dynamic air compressions are designed for large volumes of air and flow. A simple example of this principle is the Aeroplane Jet engine which takes in a huge amount of air which then gets pushed through the jet impellers to the combustion chambers to be burned with the fuel and due to the high air force (pressure) the plane starts to run and then fly.


Want to learn more? You can download Atlas Copco’s Compressed Air Manual or you can call us on 1800 023 469 to learn more and discuss the best compressed air option for you.


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