How does a compressor work

Published: Fri 22nd May 2026

A guide to compressor technology

• What is air displacement, and how does it allow an air compressor to work?
• What are positive displacement and dynamic displacement, and which compressor technologies rely on them?
• What is the difference between the working principle of oil-lubricated and oil-free compressors?

What is air displacement, and how does it allow an air compressor to work?

Air displacement is vital to the air compression process. This is because it is the way in which an air compressor gets atmospheric air into its chamber. There are two different types of air displacement: positive displacement and dynamic displacement. All compressed air technologies rely on one of these air displacement methods to work. Let’s take a look…

What is positive displacement, and which compressor technologies rely on it?

Positive displacement involves the air compressor reducing the volume of its compression chamber in order to compress the air. Once compressed, this air is then transferred into a storage container for later use. There are 3 main types of compressor technologies that rely on positive displacement. These are:

1. Rotary screw compressors: Rotary screw air compressors have two screws inside their motor. These screws are moving continuously and simultaneously in opposite directions. This motion creates a vacuum which sucks air in and traps it between the screws. Once trapped, it is then transferred to a storage tank.
2. Rotary vane compressors: These positive displacement air compressors have a motor which sits off-centre in a rounded cavity. The engine has vane-operated rotors (blades) that spin. The spinning motion creates a large air cavity when approaching the air input. As the motor continues to spin, it moves the air with it, causing the space between the vanes to get smaller. This reduction in volume compresses the air.
3. Reciprocating compressors/piston compressors: These positive displacement compressors have a rotor. The role of the rotor in a reciprocating air compressor is to force a piston to move up and down. When the piston goes down, air is pulled into a chamber, compressed, and then forced back out when the piston rises back up.

What is dynamic displacement, and which compressor technologies rely on it?

Dynamic displacement compressors are also known as non-positive displacement compressors. These compressors rely on an impeller with rotating blades that bring air into the compression chamber. The movement of the blades creates kinetic energy, which acts to build up air pressure. There are 2 types of air compressors that rely on dynamic displacement to work:

1. Centrifugal compressors: These compressors work by drawing air into the centre of a rotating impeller with radial blades. Centrifugal forces push the air out towards the perimeter of the impeller. This causes a rise in pressure and the generation of kinetic energy. The air is then passed through a diffuser and a volute before it enters the next compressor stage, where kinetic energy is converted into pressure.
2. Axial compressors: These machines have an axial flow, as their name suggests. This means that air or gas will pass along rows of rotating and stationary blades through the compressor shaft. This process will gradually increase the velocity of the air whilst the stationary blades convert the kinetic energy into pressure.

What is the difference between the working principle of oil-lubricated and oil-free compressors?

The defining distinction between the working principle of oil-lubricated and oil-free compressors is that oil is used in an oil-lubricated compressor to lubricate components. This is to ensure they are working efficiently and make them well-suited to heavier-duty applications. Oil-free compressors eliminate the need for oil to lubricate internal components. This makes them ideal for industrial environments where high air quality and sanitation are uncompromisable.

Bambi’s solutions – selecting the right compressor:

Now that you know how they work, it is vital to choose the right compressor for your operations, as otherwise their efficiency and productivity might be compromised. Bambi offers an extensive range of oil-lubricated and oil-free reciprocating piston compressors. Our solutions are suitable for a wide variety of industries and environments, including dental, laboratory, drink dispensing, and fire suppression, hobby and craft, OEM and specialist applications.

To help you choose the best Bambi compressor for you, we have provided a detailed guide under our Knowledge Centre covering the essential factors to consider when selecting a compressor, such as the pressure/flow required, tank size, noise level, pipework, and dimensions. Our Product Selector has been developed to help you identify the right compressor and any potential alternatives for you to consider. Please get in touch with one of our expert team should you need any help in selecting the right product.

Interested in finding out more about our available air compressors? Please get in touch with one of our expert team members for any advice or further information.