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Technology, Oil-Free Air Compressors

Ask Atlas Copco: What are Dynamic Compressors?


There are two generic principles when it comes to the compression of air: positive displacement compression and dynamic compression. We went over the different types of positive displacement compressors and how they work. Now, we’ll dive into the technology behind dynamic compressors, also known as turbocompressors.

What is dynamic compression? 

During dynamic compression, air is drawn between the blades on a rapidly rotating compression impeller as it accelerates to a high velocity. Subsequently, the gas is discharged through a diffuser, where the kinetic energy is transformed into static pressure. Depending on the main direction of the gas flow, these compressors are called radial or axial compressors, all of which are designed for large volume flow rates. 

Centrifugal compressors

Dynamic compressors with radial design are referred to as centrifugal compressors. In a centrifugal compressor, air is drawn into the center of a rotating impeller with radial blades and is pushed out toward the perimeter of the impeller by centrifugal forces. A pressure rise generates kinetic energy due to the radial movement of air.

The radial movement of air causes a pressure rise and generates kinetic energy. Before entering the center of the impeller, the air passes through a diffuser and volute where the kinetic energy is converted into pressure.

Each stage of compression contributes to the compressor unit’s overall pressure rise. Depending on the pressure requirement of the application, multiple stages can be arranged to achieve the necessary pressure. 

Axial compressors

In an axial compressor, air passes along the compressor shaft through rows of rotating or stationary blades. This process causes the air’s velocity to gradually increase as the compressor’s stationary blades convert the kinetic energy into pressure. A balancing drum is usually built into the compressor to counterbalance axial thrust.

Axial compressors are generally smaller and lighter than centrifugal compressors while operating at higher speeds. They are used for constant and high-volume flow rates at a relative moderate pressure. Given their high rotational speed, axial compressors are ideally coupled with gas turbines for electricity generation and aircraft propulsion.

Learn more about compressor technology when you download a copy of Atlas Copco’s Compressed Air Manual, or contact us with any questions you might have.

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